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f6f85e9521c754f2baa3841b51017af9 | 101 205 | 6 LMDS Channel Use | |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 6.1 Modulation and Channel Coding | MWS is a term associated with the pan-European band of 40,5 GHz ... 43,5 GHz. In concept it is similar to the earlier term LMDS which applies specifically to the US scenario being sited at 28 GHz ... 30 GHz. The first interest when exploiting a new spectral resource in the sense of MWS (Multimedia Wireless Systems) is compatibility to existing technology to keep the additional effort and costs for carrier translation and re-modulation small. Further a balanced quality and availability shall be envisaged for both forward and return path. In a certain sense this is guaranteed when it is referred to DVB compliant signal generation and distribution. This is technically given and well approved for the DVB systems below 40 GHz as described in EN 300 421 [1]. In the present document it shall also be recommended for 40 GHz applications. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 6.1.1 Channel Characteristics at 40 GHz | To decide on a modulation system it is noted that at 40 GHz nearly Gaussian propagation characteristics are to be expected. This is due to the granularity of surfaces which in most cases are coarser than the order of wavelength (7 mm). Thus all reflections will have strong attenuation while the direct path has to be without obstruction since even refractions at borders are not significant (the strict directivity of user terminal antennas included in consideration). In addition a strong atmospheric attenuation compared to lower terrestrial frequency applications has to be expected. Thus significantly less multipath effects as well as true line-of-sight operation can be spoken of. The Gaussian characteristic makes it similar to a satellite channel and implies the use of the DVB-S codec for broadcast. The only significant difference is that one has to envisage the enhanced thermal noise caused by the lower elevation of user and base station antennas in some cases. Thus e.g. QAM as used in CATV is not recommended due to the link budget. The following specifications are recommended for coding and modulation: β’ EN 300 421 [1] β’ EN 301 199 [1a] ETSI ETSI TR 101 205 V1.1.2 (2001-07) 13 Today the specification EN 300 421 [1] is widely applied standard via worldwide space segments. A special property is the low C/N (carrier-to-noise ratio) being applicable to the system within AWGN (Additive White Gaussian Noise) channels, based on the implementation of a so-called convolutional codec incorporating a VITERBI Decoder at the receiver site for extracting the signal out of a noisy environment. A second facility, the so-called puncturing, enables the codec to adopt its error correction performance to the channel quality status. In clause 7.2 a link budget calculation will be presented as being the basis for determining the transmit power for achieving a sufficient C/N. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 6.2 Definition of a Possible Spectrum Structure | |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 6.2.1 The First Way To Exploit the Resource at 40 GHz | The present document proposes operation in the 40,5 GHz ... 43,5 GHz range. Spectrum allocation at 40 GHz means the on one hand a most optimum exploitation of the resource and on the other hand technical feasibility in terms of bi-directional channelization equipment. In the present document two possible kinds of spectrum structure are introduced allowing operation in 40,5 GHz ... 43,5 GHz range. The first one is designed with the goal of keeping the frequency bands for up and downstreams consistent and reducing the guard bands to a minimum according to possible future technology. The symbol rate is supposed to be a variable for optimum tailoring of operation to actual demand. Further QPSK modulation is envisaged with either differential or non-differential mapping, because this kind of modulation is: β’ intrinsically bandlimited; β’ of high characteristic bandwidth efficiency of 2 bit/(s x Hz); β’ suitable for quasi-Gaussian channels as is the case at 40 GHz. With a variable symbol rate, i.e. for wideband as well as for narrowband applications the spectrum allocation up to 43,5 GHz can be specified as shown in figure 1a (Frequency Raster see annex A). Upstream Frequency 40,5 GHz 43,4 GHz 42,75 GHz Return channels (variable symbol rates) Broadcast channels with Interaction (embedded or not) Satellite segment's reception range (variable symbol rates) Guard Band Slopes! 40,6 GHz 42,65 GHz 42,85 GHz 43,5 GHz Downstream Figure 1a: First Proposal: Use of Actual Resource for LMDS up to 43,5 GHz For the sake of understanding the spectrum with customer direction "Downstreams" are drawn upside-down. Broadcast & Interaction (Downstream): 1 x 2,05 GHz = 2,05 GHz, Return channels (Upstream): 1 x 550 MHz = 550 MHz. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 14 Overhead: Centre guard bands: 1 x 200 MHz = 200 MHz Border guard bands: 2 x 100 MHz = 200 MHz The equipment shall be able to accept spectrum in the RF layer in the inverted or non-inverted form. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 6.2.2 Alternative Use of the Resource | As was explained in clause 4, the re-broadcast of satellite segments will be a possible contribution to spectrum use. The number of return channels will also increase (e.g. by the growing implementation of telephony) with the consequence that there must be found a sufficient compromise between broadcast and interactivity aspects. Thus the following structural alternative shall be proposed (figure 2): a b c d e f a b c d e f POL V POL H POL V POL H g p q r s t n m i l o h s n t q i l g o h p m r POL V POL H POL V POL H 40,5 GHz 41 GHz 41,5 GHz 42 GHz 42,5 GHz 43 GHz 43,5 GHz Figure 2: Alternative Spectrum for LMDS Respecting the Future Use of Interaction/Broadcast up to 43,5 GHz The spectral resource displayed here shows up the following bands: Table 2: 40 GHz Frequency Plan Proposal - Wide Bands DOWNSTREAM UPSTREAM SERVICES Frequency (GHz) POL. Frequency (GHz) POL. T/R SPACING (MHz) WIDE BAND CH. Sub-Band a 40,5 β 41,48 V 42,3 β 42,5 H 820 Sub-Band b 41,5 β 42,48 V 40,5 β 40,7 H 800 Sub-Band c 42,5 β 43,48 V 41,5 β 41,7 H 800 Sub-Band d 40,5 β 41,48 H 42,3 β 42,5 V 820 Sub-Band e 41,5 β 42,48 H 40,5 β 40,7 V 800 Sub-Band f 42,5 β 43,48 H 41,5 β 41,7 V 800 ETSI ETSI TR 101 205 V1.1.2 (2001-07) 15 Table 3: 40 GHz Frequency Plan Proposal - Narrow Bands DOWN-STREAM UP-STREAM SERVICES Frequency (GHz) POL. Frequency (GHz) POL. T/R SPACING (MHz) NARROW BAND CH. Sub-Band g 40,5 β 40,99 V 41,4 β 41,5 H 410 Sub-Band h 41 β 41,49 V 40,5 β 40,6 H 400 Sub-Band i 41,5 β 41,99 V 42,4 β 42,5 H 410 Sub-Band l 42 β 42,49 V 41,5 β 41,6 H 400 Sub-Band m 42,5 β 42,99 V 43,4 β 43,5 H 410 Sub-Band n 43 β 43,49 V 42,5 β 42,6 H 400 Sub-Band o 40,5 β 40,99 H 41,4 β 41,5 V 410 Sub-Band p 41 β 41,49 H 40,5 β 40,6 V 400 Sub-Band q 41,5 β 41,99 H 42,4 β 42,5 V 410 Sub-Band r 42 β 42,49 H 41,5 β 41,6 V 400 Sub-Band s 42,5 β 42,99 H 43,4 β 43,5 V 410 Sub-Band t 43 β 43,49 H 42,5 β 42,6 V 400 |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 6.2.3 Other RF Resources | Besides the 40,5 GHz β 43,5 GHz (MWS) range there also exist some older and already regulated so-called FWA (Fixed Wireless Access) ranges. These ranges consist of the following resources and are covered by CEPT/ERC Recommendation 13-04 [9]: 3,4 GHz β 3,6 GHz, [Together with mobile services, fixed satellite and amateur radio] 10,15 GHz β 10,3 GHz, [Together with mobile services and amateur radio] 10,5 GHz β 10,65 GHz, [Together with radio astronomy, mobile, earth satellite (passive) space research] 24,5 GHz β 26,5 GHz, [Together with mobile, inter-satellite] 27,5 GHz β 29,5 GHz. [Together with earth exploration-satellite (space-to-Earth)] The characteristic of these resources is that many CEPT countries have already granted licenses or are planning to do so. The problem with this is that in some countries there are other primary services operated in parallel which means that in case of interferences MWS is not or only hardly possible. Thus we take the opportunity here to recommend an operation in the 40 GHz range which is only used by radio astronomers in parallel. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 6.2.4 Mesh Systems | In parallel to the point-to multipoint structure which is the main structural subject being discussed in the present document there are coming up so-called "meshed systems" with a more de-central network organization. These structures comprise point-to-point microwave links between "Nodes" at customer premises, forming a distributed network. Traffic routing through the radio network has to employ a TCP/IP or ATM transport platform and thus it is no longer a broadcasting network. Broadcast tasks have in this scenario to be performed by addressing the customer on-demand like it is the case in the internet. It is expected that the effort for routing higher bit rates through this network will be somewhat higher than in the point-to multipoint system, because in a meshed system the data stream must pass through a plenty of customer nodes with the consequence that a high reliability is required at each of these nodes. The Mesh network architecture requires a novel form of multi-directional antenna array at each radio node. Designs for switched arrays and steerable arrays have to be developed. Concerning EN 301 199 [1a] the protocol layer must be widely modified when the transition and/or adoption of this specification to meshed networks is focused upon. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 16 Thus, in the present document, it can only be stated that the radio link budget becomes much more simple since point- to-point links are on the one hand in most cases shorter than in the point-to-multipoint case and on the other hand the antennas are of an equal structure of construction on both sides, i.e. they will previously have equal gains and directional diagrams at lower radiation powers. However, the advantage of meshed systems can be found in the more flexible and redundant routing procedure but a disadvantage obviously will be the overall link delay due to the repetitive demodulation/processing/remodulation at each node. Another aspect might be that each node comes up as a kind of bottleneck if several broadband data streams are routed in parallel. Thus the "broadband" wireless access may be in a certain sense limited in such systems compared to the central system with the base station transmitting e.g. a plenty of broadband streams in parallel to many users. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7 Propagation Parameters and Cell Size | The purpose of this clause is to prove the parameters of these guidelines by physical and mathematical models and/or to support them by measurement and experiences. In the case of LMDS this is urgently indicated, first because it is a wireless system and second because it shall have despite this a defined reach. Thus it is not only the interest of the local regulating offices but also of the provider to ensure an interference free signal distribution. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.1 The Propagation of Millimetric Waves | |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.1.1 Atmospherical Attenuation | From the physical point of view millimetric waves behave in vacuum like every other electromagnetic radiation i.e. the power flux density is given by the so-called Poynting Vector (W/m2). S = E X H This power flux density is given by the vector product of electric and magnetic field vectors and thus reaches a maximum in case of mutual orthogonality when far field distance is reached. This condition is approximately fulfilled in the so-called distant field area RF which is approximately calculated for specular antennas by: RF = 2 D2/Ξ» with D being the aperture width of the antenna and Ξ» being the wavelength. If e.g. D = 10 Ξ» the distant field area begins at 200 Ξ». Thus at a wavelength of 7,5 mm (40 GHz), and using a specular antenna with a diameter of 7,5 cm, we expect the distant field area beginning at 1,5 m, i.e. from this distance the radiated wave behaves like being yielded by a spherical radiator. For the vacuum case this means a dependence on the distance r by the following law assumed that a sufficient height of the antenna above ground is used: 2 4 r G P S Γ Γ = Ο where the product P .G is called EIRP (Effective Isotropic Radiated Power) because of the virtual isotropic decrease. In atmosphere the propagation can normally be calculated similar to the vacuum case when using frequencies in the UHF range (note that reflections/refractions must then be taken into account!). In the range of several tens of GHz a certain atmospheric attenuation has to be part of the calculation. From the satellite communication world there exist valid and well-known tables and diagrams of parameters on propagation which can be used for short slant paths through the atmosphere as e.g. occur within LMDS. Diagram 3 shows a diagram for a frequency range running from 10 GHz to 1 000 THz with three essential marks (black dots): β’ A loss of 0,2 dB/km for an arid atmosphere ETSI ETSI TR 101 205 V1.1.2 (2001-07) 17 β’ A loss of 7 dB/km for medium precipitation (25 mm/h) β’ A loss of 30 dB/km for very strong precipitation (150 mm/h) It is very clear that the propagation loss can vary on a large range dependent on the actual weather conditions. When expressed by the equation the propagation loss shows up as an additional dependence on distance as an exponent in the denominator. km dB r r G P S 10 / ) 2 ,0 7 ( 2 10 1 4 + Γ Γ Γ Γ = Ο with r being inserted with the unit "km". In this equation the medium precipitation (7 dB/km) has been chosen (as an example) together with the arid atmosphere propagation (0,2 dB/km), which in each case must be taken into account in terms of a basic exponent offset. Thus the law of propagation now has an exponent characteristic that dominates the free space loss, begins from a certain distance and overrides the squared decrease significantly. Diagram 2 shows the propagation characteristics of S referred to the equation above for different rain attenuations. Two properties are highlighted very clearly. First the steepness converges for small distances towards the 1/r2 characteristic according to a 6 dB per duplication of distance. Secondly the exponent decrease begins to dominate at a distance of approximately 1 km. In clause 7.2 the figures are treated in somewhat more detail when the link budget is explained. However on this occasion it shall be anticipated that the signal level of 30 dBpW/m2 (= 1 nW/m2) is the flux density necessary for 1 km coverage at 15 dB rain attenuation. It is an interesting fact that a decrease of the rain attenuation by e.g. 5 dB from 15 dB to 10 dB does not really yield a dramatic change in gain in distance as one could expect. The signal level has again decreased to the limit after some hundred metres. Thus the expression "wireless cable" is really true. This can be verified by comparing the curves with a cable or waveguide characteristic that decreases also by N dB/m which corresponds to an exponent decrease in the linear notation! (see diagram 2). Nevertheless it is recommended that the base station as well as the user terminals power is controlled to avoid interference with adjacent LMDS cells! This power control may be performed by continuously measuring the flux density or the C/N at the worst case remote location where users are established. All other cell locations are then covered by stronger signals and treated by the AGC (Automatic Gain Control) of the user terminals. From diagram 2. it can be clearly derived that the AGC of the user terminal reception front end shall cover a gain variation range of 60 dB to cope with all signal levels occurring in an LMDS cell. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.1.2 Reflection/Refraction | Reflections and refractions of waves at an obstacle result in unwanted impairments due to multipath reception. These effects act like comb filter characteristics (selective fading) when exceeding a certain magnitude. In this case the channel modelling must be drastically changed from a Gaussian to a Rice or Rayleigh one. However, it is shown here that in most cases Gaussian modelling is valid for the 40 GHz ranges. Since many activities are ongoing in the 40 GHz range and higher there exist some investigations into propagation. An example is given [2]. The main difference in propagation between the 60 GHz and the 40 GHz ranges is that at 40 GHz no oxygen absorption is observed. The other properties as e.g. rain attenuation and refractional/reflectional behaviour are nearly the same. It was attempted to build physical and mathematical models for the distance - dependent decrease showing that there exists (without rain attenuation) a theoretical breakpoint distance given by: dbp = 4 hthr / Ξ» ETSI ETSI TR 101 205 V1.1.2 (2001-07) 18 where: h = Antenna height (transmit or receive); and Ξ» = Wavelength Beyond this distance the decrease runs as the fourth power of the radius. This is supposed to be caused by multipath propagation mechanisms. If e.g. dbp is calculated for 40 GHz (7,5 mm), a distance value of 4,8 km is obtained when the reception antenna height is set to 1,8 m and the transmission antenna height is 5 m. On the other hand it is shown in the link budget that quite different causes (rain attenuation) forbid a cell radius being significantly greater than 1 km. Thus within this distance the 1/r2 law is obviously dominating as for the vacuum case, added to by certain atmospheric attenuation laws, if sufficient antenna heights are assumed. Further it is reported that diffuse reflections as e.g. are caused by trees or other coarse granular surfaces can be totally neglected. The dependence on antenna height (e.g. supported by [3]) can be explained to be due to the ground absorption of wave: diagram 1 (extrapolated to 40 GHz, Ξ» = 7,5 mm) shows once more a decrease of the field strength by 1/r4 at ground vicinity according to 40 dB per decade of distance. Thus in general the free space propagation laws apply at sufficient antenna heights. Further supposing that a directional user terminal antenna of 35 dBi gain and β3dB angle of Β±1Β° is applied it can be assumed that in most cases the residual reflections will attenuate by 20 dB. If the fact that a reflected signal is itself attenuated by more than 10 dB by the reflection process is additionally taken into account then the conclusion is that nearly every reflection or refraction contributes less than β30 dB compared to the useful signal. Because the QPSK signal in each case is PRBN energy dispersed before transmission an RFI jamming situation with selective fading due to echoes can be nearly totally excluded. Conclusion: It is adequate to treat the 40 GHz directional radio link like a Gaussian channel and therefore to apply a specification like is known from satellite links. Special terrestrial modulation schemes like e.g. COFDM are not obligatory. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.2 Link Budget | |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.2.1 General | Link budgets are well-known from satellite communications and are suitable to make a statement about the reception C/N at the destination point of the link. The so-called path loss is one of the most important effects treated by the budget. It determines widely the system operating distance if a certain availability is supposed. In this link budget consideration the path loss is treated separately from the antenna aperture despite this is not being done in the literature in most cases, i.e. both are very often combined, resulting in a frequency dependent "free space loss" which shall not be mixed up here (the vacuum is really not "low pass"!). This is done for the sake of clear propagation influence demonstration. Antennas and first amplifier stages contribute their noise figures in a well-known manner too. Nevertheless at 40 GHz these noise figures are somewhat increased which requires an utmost exact verification. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.2.2 Basic Relations | |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.2.2.1 C/N Margin | In the following considerations the embedded downstream is firstly taken into account. The modem and codec of [1] is supposed which is for no loss in general. Later-on the link budget for other modems/codecs can easily be scaled according to their different coding gains or Nyquist filter bandwidths. [1] indicates that for the satellite scenario the following C/N values apply for the so-called quasi error free reception at a BER = 10-11 ... 10-10 at the input of the MPEG2 demultiplexer. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 19 Code Rate C/N (dB) 1/2 4,1 (4,38) 2/3 5,8 (6,08) 3/4 6,8 (7,08) 5/6 7,8 (8,08) 7/8 8,4 (8,68) These values have been calculated for a symbol rate of 25,776 MSy/s according to a Nyquist filter bandwidth of 12,888 MHz (-3 dB). The signal bandwidth at carrier level is therefore: 2.fn = 25,776 MHz which is relevant for noise considerations. In practice the implementation on satellite today is realized with a signal bandwidth of 27,5 MHz which is slightly different from the values above which refer to a transponder bandwidth of 33 MHz (-1dB) and are implemented with a form factor of 1,2 between transponder and signal bandwidth. This change results in a modification of: dB 28 ,0 776 , 25 5, 27 log 10 = β
The new values are written within brackets in the table. For the down streams 27,5 MSy/s is assumed and the link budget is calculated. Further we base this calculation on a sufficient margin with a minimum C/N of 10 dB to cope with the weakest code rate of 7/8 respectively. In addition to this 5 dB are recommended to adopt to implementation influences such as e.g. antenna mispointing. This C/N of 15 dB must be valid at the demodulator input (down-converter output). Another very important aspect is the fact that cases of "multiple budgets" are possible, e.g. when a satellite transport stream is purely back-hauled and up-converted rather than re-modulated which means that the LMDS radio link is not the only one but it is preceded by e.g. a satellite up β and down-link. The C/N Values then behave according to the law: n n ges ges N C N C N C N C / 1 ... / 1 / 1 1 2 2 1 1 + + + = This means that the total C/N of course becomes worse than the worst one in the chain. In such scenario, consequently the particular budgets should be significantly better than the overall link budget because if e.g. two systems figure up with approximately similar budgets the link will be worse by 3 dB as a whole. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.2.2.2 Antennas | It was already mentioned that the antenna gain at the user site should contribute with approximately 35 dBi to receive the base station signals but, on the other hand, with not too critical angular pitch. The situation concerning this is then similar to satellite reception scenarios where 35 dBi antennas apply, in this case with diameters of approximately 60 cm. The difference about this is the effective aperture of the antenna which decreases proportionally to the squared wavelength. This must be strictly taken into account when exploiting the power flux density at the reception site. Further it is important that reciprocity is valid, i.e. the same antenna gain must be supposed for reception as well as transmission at the same location. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.2.2.2.1 Antenna of the User Terminal | Shall the aperture of an elementary Hertzian dipole be given by: 2 8 3 Ξ» Ο Γ = HD A the antenna has at a gain of 35 dBi and a wavelength of Ξ» = 7,5 mm an effective aperture of: 2 5,3 212 10 cm A A HD = Γ = ETSI ETSI TR 101 205 V1.1.2 (2001-07) 20 This aperture collects, at correct pointing state, the signal power: A S P Γ = from the air. (S being the pointing vector magnitude). This power results at the so-called "antenna flange" and it is further transported to the Low Noise Amplifier by using a waveguide adaptor. In transmission direction the gain is the same, i.e. the antenna yields a power flux density being 103,5 times stronger than that for an elementary dipole would do. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.2.2.2.2 Antenna of the Base Station | The antenna technique of the base station differs profoundly from that for a user site one. In the latter case the following criteria are valid: β’ High antenna gain. => Narrow main lobe. => Extinction of interferences by high antenna directivity. β’ "Only base station visible". For the base station itself the following criteria are valid: β’ Radiation of sufficient power. β’ Sufficient area coverage. => Lower directivity. (=> "All wanted users visible".) The antenna gain definition can only be made by including the required foot print to define the area covered. This foot print is strictly correlated with the spacial angle cutting a piece of area out of the theoretical spheric area of an omnidirectional radiation pattern. It shall be supposed that at the base station site a so-called horn antenna is applied, i.e. an antenna with neglectable sidelobes [3]. Horn antennas belong to the group of so-called waveguide antennas having very homogeneous power flux density distribution. Therefore the footprint coverage calculation can be made by using the spacial angle without introducing significant error. The forming of the footprint in the area envisaged will be done according to the details of the landscape and user distribution. Field trials or sample measurements may also influence the result. The position of the antenna (i.e. the height above ground and its elevation or whether it is covering the interior of a valley or a plane), also determine the shape of the optimized footprint. In each case the resulting gain is important for the link budget. If the shape of the coverage area is an arbitrary oval, the spacial angle forming can be made by using spheric integration with the azimuth and elevation maxima being the limits. Thus, the area being cut out of the isotropic sphere becomes: β«β« Γ Γ Γ = 2 1 2 1 0 Ο
Ο
Ο Ο Ο
Ο d d r R A With Ο
being the elevation angle, Ο being the azimuth angle, R0 being the sphere radius and r being the cylindric radius within the sphere (see figure 3). ETSI ETSI TR 101 205 V1.1.2 (2001-07) 21 r R0 Ο
Figure 3 Where: r = R0 sin Ο
. And the integration results: ( ) ) cos (cos 2 1 1 2 2 0 Ο
Ο
Ο Ο β Γ β = R A Now we can calculate the approximate antenna gain by using the ratio of the whole isotropic sphere and the particular area A: ( ) ) cos (cos 4 4 2 1 1 2 2 0 Ο
Ο
Ο Ο Ο Ο β Γ β = Γ = A R g ; or written in logarithmic notation: ( ) )) cos (cos 4 log( 10 4 log 10 2 1 1 2 2 0 Ο
Ο
Ο Ο Ο Ο β Γ β Γ = Γ Γ = A R G ; Further it shall be supposed that the shape of a cell will in many cases be a quarter of a circle, which means that the azimuth spot angle will be approximately 90Β°. This situation can become valid e.g. in case of an area coverage with the base station being located on a hill. The elevation spot angle, on the other hand, is determined by several parameters of the location (e.g. the spacial extension of the area being covered, the height of the base station, etc.). In this example the elevation opening angle is assumed to be 30Β°. If these values are applied to a horn radiator (referring to spheric coordinates): Ο2-Ο1 = Ο/2 (90Β°), Ο
1 = 90Β° - 15Β°, Ο
2 = 90Β° + 15Β°, 12 dBi antenna gain can be obtained for the base station antenna. This is shown schematically by figure 4. βΟ
= 30Β° βΟ = 90Β° Figure 4: An example for antenna height and spot ETSI ETSI TR 101 205 V1.1.2 (2001-07) 22 If the scenario is changed to cover an area from a low hill spot angles such as: Ο2 - Ο1 = 90Β°, Ο
2 - Ο
1 = 10Β°, would result in an antenna gain of 16,6 dBi. However, in this case the shadowing by the buildings must be taken into account by installing the user site aerials on roof tops. The situation is quite different in case a narrow valley is to be covered (mountain terrain). Thus the angles of: Ο2 - Ο1 = 20Β°, Ο
2 - Ο
1 = 20Β°, (symmetric circular horn) must be implemented resulting in an antenna gain of approximately 20 dBi . For the link budget calculation of the base station the worst case value of 12 dBi shall be supposed. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.2.2.3 Waveguides | Waveguides for TV satellite communications (Uplink 17/18 GHz, Downlink: 10,7 GHz ... 12,75 GHz) have a typical loss figure of approximately 0,16 dB/m. Waveguide transitions contribute with somewhat greater losses: Usually a value of approx. 0,3 dB is supposed within the so-called LNB unit ("feed waveguide") of consumer equipment. In the 40 GHz ranges we can suppose for the sake of a safe calculation 3 dB due to possible parasitic influences like extreme skin effects and/or moisture, oxydation or pollution. Assumptions in this order of magnitude are also made by manufacturers of those components. The decisive fact for the link budget is that this feed waveguide has its location before the low noise front end amplificator and thus shows up its influence by: G F 1 = ; (F = Noise figure, G = "Gain" < 1) as a noise source. In this example the noise figure has to be put to: F = 3 dB in the logarithmic notation. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.2.2.4 Low Noise - Amplifier | Providing sufficient amplification, with adequate bandwidth, and stability is in most cases a question of circuit layout as well as geometry. In the literature, standard methods of calculation are known [6]. Semiconductor technology, on the other hand, is nowadays capable of handling these frequencies (25 ps duration period!). The transistors applied are mainly of the GaAs type or, alternatively, indium-phosphide FETs, sometimes occurring as a mixed-type technology with GaAs being the base material. An amplifier unit as a whole is in most cases produced in the shape of small wafers being directly bonded onto the PCB circuit layout to avoid parasitic inductors and capacitors as well as mismatched lines (wavelength 7,5 mm!). Despite these precautions there are remaining effects of attenuation which increase the noise figure, especially at the low noise amplifier input. In the link budget β again for safety reasons β a value of F = 5 dB is assumed as the worst case. The values of total amplification are supposed to be in the range of approx. 40 dB ... 50 dB (as for satellite LNBs) because higher values would lead to unstable operation. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 23 |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.2.3 Link Budget/Details | Under the conditions listed in clause 7.2.2 above the link budget for the up/downstream can be calculated. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.2.3.1 Downstream | First, the so-called in-band downstream shall be regarded (see table 4), i.e. the scenario of the base station covering a defined area by a 12 dB horn antenna with a defined power flux density, measured in W/m2 and being linked to the user terminals operating with a 35 dB equivalent antenna aperture. The result shall be that even at the cell border the carrier-to-noise ratio C/N is sufficient great to ensure safe reception according to e.g. the margins required by EN 300 421 [1] (DVB) or another specified modem/codec. The margins are themselves defined by e.g. the geographical rain statistic and the basic atmospherical attenuation. We proceed step by step along the signal path. Let's suppose a generated RF power of P = 30 mW in the base station HPA. With an antenna gain of G = 12 dBi an EIRP of: dBm G P EIRP 77 , 26 ) log( 10 = + Γ = is yielded. The transmission path is illuminated with this power. The maximum length has been found to be approx. 1 km in 7.1.1. The signal power density undergoes (8.1.1.) a quasi-spheric propagation attenuation according to 1/r2 , downgraded by the rain attenuation according to the exponential law. A basic air (clear sky) attenuation of 0,2 dB/km has also been taken into account: 2 10 /) 2,0 15 ( 2 / 1,1 10 1 4 m nW r G P S r = Γ Γ Γ = + Γ Ο The value of 15 dB for the rain attenuation was in this example taken as being a compromise between the cases of "medium precipitation" (25 mm/h, 7 dB) and "very strong precipitation" (150 mm/h, 30 dB) to obtain a realistic availability figure of the system. According to [4] central Europe belongs to rain zone 3 with a rainfall rate of 37 mm/h for 0,01% of the time (year), i.e. the availability is calculated by: % 99 , 99 % 01 ,0 % 100 _ _ _ = β = + = time l operationa time out time l operationa A The reception antenna has a worst-case elevation of 0Β° which implies that for the equivalent background noise temperature a figure of 300 K (27Β°C) must be supposed (see note). The equivalent noise temperature of the antenna matter is in most cases assumed to be in the range of 20 K. Further, the so-called system bandwidth, which is the bottleneck bandwidth for the noise and which is in most cases provided by the so-called Nyquist filter (matched filter) in the modulator/demodulator baseband processing, is assumed to be 27,5 MHz according to 7.2.2.1. NOTE: This is really the worst case. Normally the user antenna will have a slight positive elevation due to the enhanced position of the base station. With these values the noise power at the antenna flange is calculated as: pW K K f k N 121 ,0 ) 20 300 ( 0 = + Γ β Γ = On the other hand the signal power flux density S will be collected by the effective antenna aperture Aeff with the antenna flange signal power being the result (G = gain, AHD = elementary hertzian dipole aperture): HD eff A G A Γ = pW A S C eff 2, 24 = Γ = ETSI ETSI TR 101 205 V1.1.2 (2001-07) 24 Thus the expected C/N at the antenna flange becomes: dB dB Antenna N C Flange 23 121 ,0 2, 24 log 10 ) ]( [ / = Γ = This value undergoes further additional degradations due to feed waveguide losses and LNA stage noise figure FLNA as well as the downconverter noise figure FDOWN: LNA DOWN LNA Flange LNA waveguide DOWN LNA waveguide Flange OUT G G F F F Antenna N C G G F G F F Antenna N C DOWNCONV N C waveguide waveguide waveguide β
β + β
= β
β + β + = 1 ] [ 1 1 ] [ ] . [ ; with waveguide waveguide G F 1 = ; - logarithmically evaluated: dB DOWNCONV N C OUT 15 ] [ / = The C/N interface loss at the feed waveguide output is also shown in table 4 as 3 dB. The LNA noise figure has a very important influence upon the result while it is clear that the downconverter noise figure (supposed to be 8 dB) is neglectable compared to this. This is well-known and is related to the fact that the noise figure of every consecutive stage is denominated by the cumulative gain of the predecessors. Thus, the noise figures of the IF path are not relevant for the link budget. Consequently the C/N value of 15 dB can also be approximated for the demodulator input. It contains, in addition, enough margin for implementation losses as e.g. slight antenna mispointing, losses due to suboptimum feed mounting, etc. The transmitted EIRP is in this case approx. 26,8 dBm as shown in table 4. An interesting fact is that, with these link budget assumptions, the flux density value at a distance of 1 km becomes 1,1 nW/m2 and exceeds the satellite flux density of a satellite DTH downlink (10 ... 20 pW/m2) by a factor of approx. 100 in the footprint centre. This factor is due to the enhanced rain margin calculation and on the other hand to the smaller elementary aperture at 40 GHz. Radio links of different frequencies are unlikely to be interfered because in regular cases they are off axis and, if they are despite of this, the spin-off level is low enough to avoid mixing products. The danger of cellular over-spill can be minimized by suitable beam forming (spot definition) and geographically enhanced positioning of the base station as well as by qualified power control to cope with weather changes. Additionally mentioned shall be the so-called "Figure of Merit" G/T with a value of approx. 2,2 dB/K for this system in the downstream. This figure depicts the ratio of antenna gain and the overall noise temperature. The interesting fact about this is that the value is positive related to the high user terminal antenna gain which is similar to the gain of a satellite in-orbit dish pointing onto the "warm" earth. For the Out of band downstreams, EN 301 199 [1a] supposes a channel raster of 2 MHz. The rolloff is defined to be 30 % with the consequence that the pure signal bandwidth becomes: 2 MHz/1,3 = 1,54 MHz which is also the OOB downstream QPSK symbol rate. Since the system noise bandwidth is determined by the Nyquist rolloff matched filter in the receiver, the C/N can be scaled according to this proportionally. On the other hand, if the C/N shall be kept at the same value, the transmission power can be scaled. Following this, the EIRP values for different bandwidths are: 14,3 dBm at 1,54 MSy/s (2 MHz raster, "Grade B" with 3,088 Mbit/s), ETSI ETSI TR 101 205 V1.1.2 (2001-07) 25 For the flange power at same antenna gain we obtain: 1,68 mW at 1,54 MSy/s (2 MHz raster, "Grade B" with 3,088 Mbit/s). Of course these values are understandable in terms of orders of magnitude and can vary according to additional conditions. In clause 7.2.3.3 it is proved that the omission of the convolutional codec does not lead to a change of these figures. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.2.3.2 Upstream | For the upstream link budget calculation the same weather conditions as well as equipment parameters in terms of waveguides and amplifiers shall be supposed. Only the reception and transmission antenna gains are mutually exchanged (see also 7.2.2.2). We first calculate the link budget regardless of the different codec used. Table 5 shows the budget calculation result. One essential difference to the downstream is the far higher EIRP of approx. 47 dBm which is calculated for the same system bandwidth but, on the other hand, for a base station reception antenna being now far smaller due to the wider spot required. A law for scaling according to different upstream bandwidths is given in 7.3.2. The spot design laws are explained in 7.2.2.2.2. The now very negative figure of merit G/T of -21 dB/k is similar to those of isotropic reception systems as e.g. GSM base stations. At 40 GHz, implementation losses are the main source for the enhancement of the equivalent noise figure. However, they are reduced with progress in manufacturing. In this case it is supposed that the transmission antenna flange of the user outdoor unit is loaded with 15 mW. Then, at the base station site, a C/N of approx. 12 dB is left which provides enough margin in relation to e.g. the value of 8,7 dB for code rate 7/8 at 27,5 MHz system bandwidth (symbol rate). The reciprocity is well visible here: If 30 mW were chosen for antenna flange power the C/N would increase to 15 dB but the 15 mW value is a good compromise according to user consumer electronics and it is easy to implement. The case of a return channel symbol rate of 27,5 MHz has been chosen for example to verify bi-directional link budgets and as a guideline for measurement. In context with the DVB LMDS document EN 301 199 [1a] an upstream channel raster of 2 MHz is provided in a first step. The rolloff is defined to be 30 % with the consequence that the pure signal bandwidth becomes: 2 MHz/1,3 = 1,54 MHz which is also the upstream QPSK symbol rate. Since the system noise bandwidth is determined by the Nyquist rolloff matched filter in the receiver, the C/N can be scaled according to this proportionally. On the other hand, if the C/N shall be kept at the same value, the transmission power can be scaled. Following this, the EIRP values for different bandwidths are: 34,5 dBm at 1,54 MSy/s (2 MHz raster, "Grade C" with 3,088 Mbit/s), 37,5 dBm at 3,08 MSy/s (4 MHz raster, "Grade D" with 6,176 Mbit/s). For the flange power at same antenna gain we obtain: 0,84 mW at 1,54 MSy/s (2 MHz raster, "Grade C"), 1,68 mW at 3,08 MSy/s (4 MHz raster, "Grade D"). Of course these values are understandable in terms of orders of magnitude and can vary according to additional conditions. In the next clause it is proved that the omission of the convolutional codec does not lead to a change of these figures. Figure 2a contains as an example the link budget for 1,54 MSy/s. Nevertheless, it is recommended that the outdoor unit power amplifier stage should be designed for higher bandwidths in future, i.e. a power of 15 mW at antenna flange should be possible. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 26 A special aspect of the user outdoor unit is that the spot beam of the transmitted signal is with a value of approx. Β±1Β°, far narrower than the bas station beam which ensures that the risk of impairing foreign services is effectively minimized. Since, in addition to this, the base station has in most cases a raised location, a situation similar to satellite uplinking is given, i.e. the user outdoor aerial will have a raised elevation ensuring that beam overspilling disperses into the atmosphere. In clause 9 the electromagnetic safeness topic is treated in somewhat more details. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.2.3.3 Codec Influence | The link budget calculated below did not incorporate convolutional and Reed-Solomon codec properties. This was omitted intentionally to give a basis for bandwidth scaling. Thus, it seems to be reasonable to calculate the link budget on a C/N basis and then to compare it to actual codec requirements. The codec supposed here for downstream is the DVB EN 300 421 [1] one which was shown in clause 7.2.2.1 when estimating the C/N margin. In the upstreams, no convolutional codec is used which means that its coding gain is missing. Despite of this, a certain gain is achieved due to the reduced bandwidth form 27,5 MHz down to e.g. 1,54 MHz. This means that an additional margin of: dB 5, 12 54 ,1 5, 27 log 10 = ο£·ο£· ο£Έ ο£Ά  ο£ ο£« Γ is gained, as calculated above (7.2.3.2). If we omit, on the other hand, the codec (see 7.2.2.1), approximately 5 dB are lost in case of taking the rate 1/2 as a basis (this is the approximate coding gain of the rate 1/2 K = 7 133 171 DVB standard convolutional code). If the rate 7/8 (see 7.2.2.1) is taken as a reference we only loose approx. 5 dB β 4,3 dB = 0,7 dB when omitting the punctured convolutional codec (the influence of the reed-Solomon codec is nearly the same in both systems). As a result there remain approximately 12,5 dB β 5 dB = 7,5 dB or 12,5 dB β 0,7 dB = 11,8 dB gain compared to the DVB EN 300 421 [1] application which is achieved in case the 2 MHz raster for up β and downstreams is used. In 7.2.2.1 the weakest code rate of 7/8 was taken as a basis, i.e. the EIRP values from above (7.2.3.2) for the "Grade C/D" β bandwidths need not to be corrected dramatically because the loss of 0,7 dB due to codec omission does not influence the system anywhere and a sufficient margin was incorporated in the link budget. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.3 Specification of Power and Frequency Resource | The results obtained can be now used to generate a scaling rule for the power flux densities in the given frequency resource. The main goal is to keep the spectral power density constant in terms of W/Hertz ant to tolerate local changes only. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.3.1 Downstream | The signal of one modulated carrier radiated by a base station in the 40 GHz ranges shall have a power flux density at the worst-case borders of a cell coverage of: MHz f MHz S S 5, 27 ) 5, 27 ( Γ = with S being the Poynting vector magnitude and S(27,5 MHz) = 1,2 x 10-9 W/m2. Within the whole LMDS cell the power flux density may be higher. The radiation shall be performed with two possible polarizations, depending on the requirements in terms of services as well as adjacent cell signal separation and/or frequency re-use where possible. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 27 |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.3.2 Upstream | The signal of the modulated carrier radiated by a user terminal outdoor unit in the 40 GHz ranges shall have a power flux density at the base station reception antenna of: MHz f MHz S S 5, 27 ) 5, 27 ( Γ = with S being the Poynting vector magnitude and S(27,5 MHz) = 100 x 10-9 W/m2. Within the whole LMDS cell the power flux density may be higher. The radiation shall be performed with two possible polarizations, depending on the requirements in terms of services as well as adjacent cell signal separation and/or frequency re-use where possible. The user shall be recommended to radiate his signal with the aid of a directional antenna with at least 35 dBi gain referring to the elementary Hertzian dipole aperture at 40 GHz (6,7 x 10-6 m2). The off axis EIRP shall be similar to or better than the off axis radiation according to the radiation mask of a conventional satellite 35 dBi specular reception Ku band antenna. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.3.3 Power Control | Power control of upstreams is provided in order to avoid severe near-far problems of the signals arriving at the base station. The problem of receiving a composite entity of individually modulated carriers increases in scenarios given in LMDS since the wide spectral resource allows a very large number of carriers being received. These carriers of course load the low noise amplifier of the reception stage for this polarization in parallel with the consequence that on the one hand a signal level being too great results in enhanced beat frequency components overranging the linear characteristic, on the other hand a signal level which is too small for one individual carrier results in a degraded signal-to-noise/crosstalk ratio for this signal envisaged. The minimum signal level for one carrier is given by the required C/N, as it has been described by the link budget in tables 5/5a. It is clear that the signal bandwidth directly influences the absolute level linearly as it has been described in the clause before, i.e. narrow band carriers do not need the reception power wideband carriers need due to the Nyquist Filter Noise Bandwidth limiting the incoming noise budget. Thus, the power control algorithm not only has to tailor the absolute signal amplitude but also has to incorporate the signal bandwidth. With the link budget given in tables 5/5a an example of determining the power of an individual carrier can be shown here: The level of a narrowband (2 MHz) return channel carrier (TDMA) has been calculated to yield a power flux density of 6 080 pW/m2 to fulfil signal-to-noise ratio requirements. If this is received by the 12 dB β horn antenna it comes out as a flange power of 0,65 pW. This is attenuated by the feed waveguide by 3 dB to 0,325 pW occurring at the LNA input. If in the upstream resource (figure 1a) of 550 MHz one polarization and sector is loaded with 275 carriers (see 8.2 "Cell Planning") the LNA input observes a composite power of 275 x 0,325 pW β89 pW. But this is not the real upper limit capability the LNA must cope with. Due to the beat frequencies occurring by linear superposition of a plenty of single carriers there must be a headroom reserved in the LNA amplitude characteristic as follows (all figures in dB): Phead (dB) = Ppeak - Pcomp; where Ppeak (dBpW) = Psingle + 20 x log(N); Pcomp (dBpW) = Psingle + 10 x log(N); This headroom is due to the squared behaviour of signal voltages in relation to power (P ~ U2 !) to avoid distortions (like in the audio) based on beat signal overranging. E.g. when 275 carriers are active in parallel (regardless whether TDMA or not) the headroom of the LNA must be tailored to: Phead (dB) = 10 x log(275) β24 dB; the true average power load is 10 x log(275) + 10 x log(0,325) dBpW = 19,5 dBpW. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 28 Consequently the total input peak power capability of the LNA comes out as: 20 x log(275) + 10 x log(0,325) dBpW β44dBpW. This is equivalent to approx. 25 nW (1,37 mV @ 75 β¦, 1,1 mV @ 50 β¦) and must be linearly guided through the LNA and to the further stages. Thus, power control becomes very important to keep each carrier within certain limitations of the link budget requirement. Now let us assume that one user terminal is transmitting from a point having a certain distance to the base station. Then it has to limit its power (like each terminal) according to diagram 2 at the beginning of the transmission by using the <MAC> Ranging and Power Calibration Message (5.5.4.3 in EN 301 199 [1a]) since the AGC of the base station can only calibrate the composite incoming signal. The following procedure is then initialized: On a so-called "Provisioning Channel" the NIU receives the so-called <MAC> Default Configuration message and configures according to this among other parameters the default power level of upstream transmission. The range of this power level is generally defined by the two parameters Max_Power_Level and Min_Power_Level (8 Bit unsigned integers). It is expected that the location distance from the base station will determine these two parameters. From a distance of e.g. 1 km, as described in the link budget (table 5a), the NIU has to provide an EIRP of 34 dBm worst-case, that means with 15 dB rain attenuation. In the best case the rain attenuation becomes zero ("clear sky", only 0,2 dB atm. att., see diagram 3) and according to this the power level has to be reduced by this value. Thus, the two parameters become at a distance of 1 km (antenna flange values!): Min_Power_Level = 19 dBm β 35 dBi(Antenna Gain) + 109 dB = 93 dBΒ΅V; Max_Power_Level = 34 dBm β 35 dBi(Antenna Gain) + 109 dB = 108 dBΒ΅V (see notes). NOTE 1: 109 dB is the offset for transforming dBm to dBΒ΅V in 75 β¦systems, 107 dB for 50 β¦systems. NOTE 2: The transformation to values into dBΒ΅V is only due to the definition of the "Power_Levels" in EN 301 199 [1a] as "unsigned integer at 75 β¦"!) And at arbitrary distances (generally, different from 1 km) the two power levels have to be calculated according to the distance equation: km dB r r G P S 10 / ) 2,0 15 ( 2 10 1 4 + Γ Γ Γ Γ = Ο where only the relative change is important. Thus, the Poynting vector magnitude itself has not to be calculated rather than the variation caused by the exponential term and 1/r2: Min_Power_Level (r) = 19 dBm β 35 dBi(Antenna Gain) + 109 dB + 20 x log(r/1km) + (0,2 dB/km) x (r/1km) = = 93 dBΒ΅V + 20 x log(r/1km) + (0,2 dB/km) x (r/1km); (without rain); Max_Power_Level (r) = 19 dBm β 35 dBi(Antenna Gain) + 109 dB + 20 x log(r/1km) + (15,2 dB/km) x (r/1km) = = 93 dBΒ΅V + 20 x log(r/1km) + (15,2 dB/km) x (r/1km); (rain included); It can be verified by inserting r = 1km that the Max_Power_Level becomes approx. 108 dBΒ΅V and for every different radius values accorded. For a different rain attenuation (rain zone, availability) only the 15 dB/km has to be replaced by a suitable value. E.g. if the availability is set to 99,90% instead of 99,99% the correction factor reveals as a subtraction (at 40 GHz) of approximately 1 dB in the equations [4]. Warning: This means that a misalignment of the power, regardless whether base station or user terminal, comes very sensibly out as a changed availability! This enforces the necessity to control the power of both sites very carefully. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 29 The tentative upstream transmission power should lay between these two power levels, regardless that it is in a single case (only one carrier requiring participation) it is previously not critical since the composite 25 nW are not significantly over-ranged (one carrier only equals 0,325 pW as calculated above). The only aspect about this is that in case many new carriers are coming up the two power levels should not be over β resp. under-ranged. A few words shall be said upon the base station power control topic: The same that is told above also goes for the base station signal radiation, i.e. if no rain attenuation is in the transmission path the signals radiated become stronger according to this. To avoid, especially in a multi-cell environment (cluster) overspill interferences it is recommended to attenuate the transmitter power according to the ceasing rain attenuation since the link budgets (tables 4, 5, 5a) are calculated for 15 dB. Thus, a mathematical and physical model should run in the base station computer exploiting the upstream link budgets for tailoring also downstream power. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.3.4 Frequency Control | Providing a wireless service always implies a certain quality of precision concerning the on-air signals since broadcasting and point-to-point links have been existing with high quality standards a long time before LMDS was considered. Thus, LMDS shall continue this tradition of quality especially under the aspect of spectral resources becoming narrower in future due to steep increase of digital services, regardless that national and international regulation offices define particularly strict limits for carrier drifts and out β of β band emissions. In EN 301 199 [1a] e.g. 0,1 ppm are required for the OOB downstreams which means that a carrier radiated at e.g. 40 GHz by the base station must not deviate in frequency more than 4 kHz over the whole time of operation. The base station (INA) carriers have to cope with this (see EN 301 199 [1a], 5.2.1.7) which is in this case easy to realize by locking the equipment to a fixed frequency reference being available by GPS or backbone facilities. For the IB downstreams Β±5 MHz are specified to be tolerated on-air. In the present document it shall be recommended to specify this tolerance in practice much better than Β±5 MHz since the user outdoor unit downconverter itself previously has a tolerance within this magnitude. This would result in a tuner acquisition range of worst-case Β±10 MHz which would require a more expensive receiver than usual. However, if the OOB downstreams are realized with 0,1 ppm, as defined in EN 301 199 [1a], it is of minor effort to do so for the IB downstream carriers, too. Carrier frequency precision is not a question of content. The new aspect about LMDS is that now return channels are introduced into the transmission scenario from the user site which has traditionally been known as consumer β level equipment with the requirement to be sufficient cheap. Performing frequency control in a consumer-like environment with cheap NIUs requires an aid by the base station. The so-called ranging process (EN 301 199 [1a], 5.5.4.6) is an interactive tentative process using the protocol of the ranging and calibration signalling. In EN 301 199 [1a] it is described how the ranging process guides the NIU to the base station demodulator window by hopping the upstream frequency with several attempts and increasing steps until the window is matched. Besides this the upstream frequency must be controlled during the whole transmission time because of e.g. thermal drift of the conversion oscillators. In this case the Ranging and Power Calibration Message contains a "range_frequency_control-field" with a boolean value "frequency_adjustement_included" which is set to logical "1" if a correction is necessary. The Frequency_Offset_Value is a 32 bit signed integer representing the upstream carrier offset frequency compared to the centre IF frequency in Hz. It is clear that less messages are necessary if the equipment hardware is of higher quality resulting in a slower or smaller drift behaviour in the upstream. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 7.3.5 Other Modulation Schemes | In the present document QPSK is treated to be a suitable modulation scheme because this is widely applied for satellite and radio links with critical link budgets. Since LMDS is a terrestrial distribution system, also closer distances between transmitter (base station) and receiver (user terminal) occur in practical operation. In these cases it can be considered to exploit the improved link budget to enhance data throughput for selected customers. When searching a modulation scheme with a higher ratio of bit/s/Hz QAM is a well-known configuration since it is, first, also a quadrature modulation, and second, modulation equipment is widely available on the market. A further aspect is the spectral shaping of the signal: The spectrum is a finite one due to the fact that it is AM-related and does not need any additional shaping beyond the Nyquist Filtering. The link budget in general remains the same, only the resulting C/N must be changed according to the values required by QAM (no additional channel coding): ETSI ETSI TR 101 205 V1.1.2 (2001-07) 30 16 QAM: 18 dB, 32 QAM: 21 dB, 64 QAM: 24 dB, 128 QAM: 27 dB, 256 QAM: 30 dB. These values are all > 15dB which shows clearly that the link budgets in tables 4, 5/5a must be changed in terms of an increased signal power since the noise power remains the same at similar noise bandwidth conditions. On the other hand it is not recommended to solve the problem by simply increasing the transmitter power because in this case the overall signal scaling (frequency power density) in the cell is violated, i.e. the cell size planning, AGC ranges of user terminals as well as return channel power should in this case be under review. If the same power conditions as with QPSK (table 4, Downstreams) are kept we get the following distance limits if additional 3 dB are supposed for antenna mispointing and other implementation margins (rain is assumed with 15 dB as usual, symbol rate = 27,5 Msy/s): 16 QAM: 750 m, 32 QAM: 650 m, 64 QAM: 550 m, 128 QAM: 450 m, 256 QAM: 350 m. If the symbol rate is decreased the transmission power must be decreased, too (see also 7.3.1). Thus the distance limitations remain the same. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 8 Cell Cluster Structures and Cell Planning | In clause 7.2.2.2.2 the antenna spot beam forming was generally discussed. As an important parameter, the shape of the coverage area was highlighted at the examples of an enhanced base station on a hill or a "narrow valley" to be covered. Generally, the shaping of a coverage area will depend on natural conditions as e.g. landscape forms, buildings and vegetation. This goes for the cell shape itself as well as for the cluster structure made up of several adjacent cells. In the LMDS system one fixed location is assumed for the base station as well as for each user. Mobile applications are not considered in a first instant. To include them, additional assumptions must be made in terms of omnidirectional antennas and doppler-safe modulation schemes. At this point of time there is no fixed standard defining scenarios like this. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 8.1 Cluster Structures | "Wireless Cable", or more general, BWS systems draw their main advantages from the fact of the so-called frequency re-use which means that each carrier frequency used in one cell can be re-used in the neighbour cell. To enable this facility certain limits in terms of power and geometry must be introduced. Generally, the laws for re-using a frequency in a neighbour cell can be formulated by the following: β’ Define a minimum C/N ratio at the cell border ensuring excellent reception of downstreams within the wanted (own) cell. β’ Control the base station power to adopt the power flux density to changing weather conditions. E.g. if the maximum power is tailored to a rain attenuation of approximately 15 dB in the worst case (see also diagram 2) and clear sky is being expected the transmission power must be dynamically lowered by 15 dB with the in- running new conditions. Else the neighbour cell might be impaired by over-radiation and the frequencies must not be used again. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 31 Since the polarization diversity shall serve for a re-use of the spectrum within the same cell this parameter should not be used for neighbour cell protection. Thus, the directivity of the user outdoor unit antenna in combination with its actual geometric direction shall be the means for establishing a line-of-sight with the wanted base station only. Other neighbour base stations being in this line shall have a multiple distance of one cell radius. If despite of this, Interferences are observed due to an in-line array of a user terminal and two base stations this shall be solved by individual measures, i.e. for such users e.g. another frequency (than this of the neighbour base station interfering) shall be used. This e.g. can be in a range where the neighbour base station radiates narrowband carriers with respective backoff, or in a range where the neighbour base station does not radiate anything or only at opposite polarization momentarily. Further a special coordination in the sense of a customer-friendly reaction upon the problem can be made together with the neighbour base station: A carrier could be removed to another frequency/polarization. But in most cases the user antenna directivity cancels other signals being not exactly in line-of-sight. A possible cluster structure fulfilling these conditions is shown below: 1 400 m r = 1 000 m User Terminals Figure 5: Example of a Cell Cluster As it is shown here, this array consists of a planar and symmetric packaging of the base stations and their transmission/reception radius with the consequence that the users within one cell only directly point upon their wanted base station. Of course, within one line of sight there may be other base stations but their antennas are located at a distance of at least 1 400 m if the cell radius is 1 000 m (square root of 2). Also the reason for the narrow user antenna directive characteristic can be clearly seen here: Despite the cell areas are overlapping the user antennas do not receive/radiate any energy (or only neglectable portions) from/to the neighbour base station. Since this characteristic is narrow (approx. 1Β° for 35 dBi antennas) in azimuth as well as in elevation user antennas being located close to the wanted base station also do not receive significant portions from the next in-line base station because of their enhanced elevation (they are looking "upwards" and not "straight-on" to the neighbour!). Adjacent sector overlap within one cell is the only problem to be solved: This occurs e.g. four times when using a 90Β° sectoral horn antenna for transmission/reception. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 32 In the reception case (from the user terminal to the horn) the ambiguous signal of the user terminal carrier in two horns can be cancelled in one sector by communication between the components of the two sectors, providing thus a certain antenna diversity feature, but in the transmission case (from the horns to the user terminal) the reception of two carriers coming from the base station may cause problems if not precisely distinguished by the user antenna. To overcome this it is recommended to use in a narrow range of angle (e.g. 2Β°... 3Β°) different polarizations as drawn below: User Terminal Horizontally Polarized User Terminal Vertically Polarized Horizontally Polarized Area Vertically Polarized Area Both Polarizations Both Polarizations Both Polarizations Both Polarizations Figure 6: Overlap Polarization Organization The idea behind the restriction to the use of one polarization only within a narrow particular sector is a most efficient exploitation of the frequency resource by polarization re-use. If a 90Β° sector as a whole is used by only one polarization the loss of spectrum is 50% compared to a full polarized system, i.e. the spectrum is principally wasted since there is no critical overlap within the sector centres requiring this restriction. If e.g. only 2Β° are used for polarization restriction we only loose: 100 x 2/90 = 2,2 % of the resource if "the resource" is interpreted to be the spectrum exploited within an area (Ο r2) of inhabitants living inside. The realization of these "border spots" can be done either by small additional single-polarized antennas at the sector borders or by a specially higher sophisticated spot-tailored antenna providing a directional diagram with two single polarized side lobes. The restriction to one polarization within the small sector border areas has to be taken into account when logging in these terminals and during the whole time of operation, i.e. the base station has to know (by analysing the MAC address) the geographic location of the user terminal. Together with this, the permission/restriction to receive certain polarizations is fixed. Despite of this the user will in most cases not recognize this restriction because the bandwidth of a service is independent of the polarization used. At high traffic there only might be sometimes a slight longer log-in waiting time due to the limited resource in the narrow border sectors. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 8.2 Cell Planning | The planning of a cell incorporates a plenty of actions being necessary. First, the propagation of the signals must be assured which is done according to the previous clauses treating the link budget and the antenna sizes/spots. Another parameter is the traffic being throughput by the base station. An example of a cell with a plenty of users is given here. It is assumed that the cell is a circular one, i.e. no line-of-sight obstructions require a non-homogeneous beam distribution and/or gap fillers (which may become necessary in certain situations as e.g. shadowing by very high buildings!). Table 7 then describes the spectral throughput being possible as a whole. Smaller scenarios can be scaled down to sizes being envisaged. However, the backbone must in each case be tailored to this. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 33 It is a big town assumed (like Munich) which shall be covered by LMDS on both polarizations and with circular cells. Supposing sectorized antennas with approx. 90Β° azimuth spot angle four base stations must be provided to cover a full cell (i.e. one base station operates ideally spoken at both polarizations if they need not to be used for cancelling interferences). The total number of base stations comes then out as to be 392 within 98 cells. The average number of households is taken from official statistics and leads to the number of houses resp. households per cell of 7 050. If the spectrum allocation example of figure 1a is taken as a basis the upstream frequency resource is 550 MHz. With both polarizations and four sectors the total resource becomes approx. 3,38 GHz if the rolloff is set to 30% (EN 301 199 [1a]). Further, a certain percentage of parallel use is supposed and for ATM the effective payload rate (Reed-Solomon, unique word and guard byte strapped) calculates as 53/64 = 0,828. Thus the bit rate per household can be estimated by: hold Rate/House Bit /Cell Households No Av Use parallel Time of Perctg (ATM) Rate Payload l Bits/Symbo Ress/Cell Frequency = Γ Γ Γ This comes out with approximately 2,54 MBit/s when supposing all these parameters and 31,2 % parallel use and shows clearly the facility of the 40 GHz range simply under the upstream resource's aspects. Since EN 301 199 [1a] basically deals with 3 Mbit/s β channels (net rate 2,54), shared by TDMA users, it is clearly visible that with a parallel use of less than 31,2 % TDMA can be switched off (steady-state operation). On the other hand, TDMA has to be switched on again when a number of households (one carrier/one household assumed) reaches a parallelism in operation of 31,2 % because the bit rate per household begins then to exceed approximately 2,54 Mbit/s which is equivalent to one effective continuous upstream bit rate. In other words: A number of users of 550 MHz/2 MHz = 275 is transmitting continuous upstreams within one segment and one polarization according to the basic EN 301 199 [1a] upstream channel bandwidth. Of course this is only valid when imagining a base station serving the whole possible resource or, at least, when a business model is supposed with a base station being operated like a satellite on the whole resource, and which is leased to a plenty of users dealing with a subset of spectrum. The calculation for the downstreams is done according to the equivalent parameters in EN 301 199 [1a], i.e. also an ATM frame of 53 bytes is assumed to be the payload. The payload rate is then calculated as the ratio of 10 x 53 bytes to the whole number of bits within the so-called Extended SuperFrame (ESF, see 5.3, table 9 and figure 17 in [1a]) of 4 632, resulting in 4 240 bits/4 632 bits = 0,915. The total spectral resource is now assumed (according to figure 1a) to be 2,050 GHz and the parallelism is again assumed to be 31,2 %, i.e. the same users transmitting the upstreams are receiving the downstreams. EN 301 199 [1a] describes these carriers to be also within a 2 MHz raster which means that with a parallel and individual interaction use of 275 downstream carriers per segment and polarization the resource is really not entirely exploited by this kind of interaction, as table 7 shows, and theoretically, 10,5 Mbit/s could supply every household. Of course, with EN 301 199 [1a], this is possibly done in the form of particularly supplying in-band downstreams according to the EN 300 421 (DVB-SAT, [1]) modem with - optionally - TV contents as an addition. In general a mixed type of operation - in-band and out-of-band - will take place. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 9 Connectivity to other Networks | An LMDS cell features in a certain sense as a special single communication system interacting with other networks like e.g. telecom's networks etc. Depending on customer's requirements the link to a satellite segment might be one of the first interconnections for the sake of re-broadcasting. This is the real manifestation of the "wireless cable" application comparable to the scenario of satellite programmes being distributed by cable headends. In the LMDS case, a remodulation can be omitted due to the large resource in case no transport stream change is provided. However, the network interconnection will surely not be restricted to satellite segment use and thus in most cases digital data are re-ordered and remodulated at the base station. The networks being served in this sense by LMDS can e.g. be: β’ Satellite Networks (Broadcast & Interaction). β’ Cable Networks (Broadcast & Interaction). ETSI ETSI TR 101 205 V1.1.2 (2001-07) 34 β’ GSM - Network (mobile telephone). β’ UMTS - Network (mobile data). β’ ISDN/PSTN (telephone & internet). β’ ATM - Networks. β’ PDH/SDH - Networks. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 10 Backbones | An additional network is the so-called backbone interconnecting the base stations with one another. The complexity of the base station will be driven by the number of connections being served. Mainly it will be the customer's wishes as well as the legal regulation facilities in a region determining this. |
f6f85e9521c754f2baa3841b51017af9 | 101 205 | 11 Radiation Safety | It is a self-understanding item that new wireless networks come up with a new problem of radiation safety. In classical regulations like the German one values of 10 W/m2, which is equal to 1 mW/cm2, are fixed for an enduring exposition. From this a security distance can be defined and it is briefly shown here that with some care to be taken the risk for health of persons is kept rather low. Since this is a free space propagation it is generally referred to the power flux density which is defined by the so-called Poynting Vector S (see clause 7.1.1). Other field magnitudes can be calculated by the use of the so-called: free space impedance Z = 120 Οβ¦ The electrical and magnetic field strength are then given by: Z S E Γ = Z S H = Since the magnitudes are quasi-stationary the RMS values are to be taken when estimating the situation for the environment. E.g. in ([5], Bild 3) it is recommended for exposition times β₯6 min: Exposition range 1: 50 W/m2, Exposition range 2: 10 W/m2. In the following we can refer to exposition range 2 because it covers civil dwelling scenarios without any consciousness of the public of the service provided by wireless radiation. This is really the LMDS situation. The main task is then to figure out the areas with power flux densities greater than the maximum tolerable value of 10 W/m2. The basis for this shall again be the link budgets defining the transmission power in terms of a sufficient C/N. The radiation power source is always the transmitting antenna and thus the maximum flux density will occur on the main radiation axis of it. Consequently, everything being closer to the antenna than the distance of the 10 W/m2 point describes, also being referred to as the "security distance", shall be out of the reach for persons. First, the security distance for the base station aerials shall be estimated. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 35 To get on this scope valid figures it is reasonable to assume the base station being fully loaded with wide-band RF carriers on each polarization, e.g. if it is shared by multiple operators which means that the whole resource of 2 x 2,05 = 4,1 GHz is filled with approximately 100 QPSK carriers at a frequency raster of 39 MHz. Basing e.g. this upon the requirement [5] the overall carrier powersum must be calculated and the security distance is then derived. Table 7 shows the relations being important for this calculation: The downstream powers are multiplied with the number of frequency channels to obtain the resulting power at antenna flange. The whole table is partitioned in three sub tables to perform the same calculation for: - the base station site, - the user terminal transmitting at return channel wideband operation (27,5 Msy/s), - the user terminal transmitting at EN 301 199 [1a] operation (1,54 Msy/s.). The power flux densities are also finally calculated. It comes out that for this value the base station figures up with a security distance of 60 cm for 100 channels and an antenna gain of 12 dB. So does the user terminal for wideband operation and an antenna gain of 35 dB (only one carrier). At EN 301 199 [1a] operation this distance reduces to only 14 cm. However, the aerials must in each case be positioned at unreachable places for public. The important thing about this is that despite the regulation offices will generally add a local flux density offset due to other transmitters operating in the vicinity, the security distance will not exceed the value of 1 m in most cases. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 36 Annex A: Recommended Frequency Raster Based upon regulation efforts concerning a MVDS (Video-) distribution from 1997 there exists a frequency raster with 39 MHz carrier spacing adopted to the usual digital satellite space segments. In the present document the spectrum structure of figure 2 is proposed and with table 6 a proposal with a frequency raster of 100 kHz shall be supplied. This raster adopts to the narrow band OOB downstreams as well as to the upstreams according to EN 301 199 [1a] and it is extended to the future resource up to 43,5 GHz. This raster also covers exactly the edges of the 39 MHz raster and thus there is no inconsistency when migrating to the new one. Each regulated bandwidth can be composed of 100 kHz segments, but it is strictly to note that the precision of transmission shall cope with the values fixed in EN 301 199 [1a]. ETSI ETSI TR 101 205 V1.1.2 (2001-07) 37 Diagram 1 (Ground Absorption alone) ETSI ETSI TR 101 205 V1.1.2 (2001-07) 38 -100 -80 -60 -40 -20 0 20 40 60 80 100 0,0078125 0,015625 0,03125 0,0625 0,125 0,25 0,5 1 2 4 Distance from Antenna / km Power Flux Density / dBpW/mΒ² 30 dB 15 dB 10 dB 5 dB 0 dB (arid Atmosphere only, 0.2 dB/km) 30 dBpW / mΒ²= 1000 pW/mΒ² Characteristic: 6 dB/Distance Duplication, like isotropic 1/rΒ² Decrease Overmode Waveguide Characteristic with 80 dB/km = 0.08dB/m Attenuation (18 GHz) Characteristic of a Cable with Attenuation of 280 dB/km = 28dB/100m at (1 GHz) Used Here: 15 dB Rain Attenuation for 99.99% Availability. Diagram 2: Signal Propagation at 40 GHz and different Rain Attenuation ETSI ETSI TR 101 205 V1.1.2 (2001-07) 39 Diagram 3: Atmospheric Attenuation versus Frequency (E.g. Central Europe: 0,01 % of the year with 37 mm/h; ITU) ETSI ETSI TR 101 205 V1.1.2 (2001-07) 40 Table 4: Link Budget/Base station -> User Terminal at 40 GHz P (W) at Antenna Flange / Base Station 0,03 Red = Transmission Antenna Gain, Transmission / dB 12 EIRP (dBm) 26,77 Path Length / Km 1 Green = Path influence Rain Attenuation / dB/km 15 Power Flux at Reception Site /pW/mΒ² 1142,65 Background Noise Temperature / K 300 Aperture Hertzian Dipole / 40 GHz / mΒ² 6,7E-06 Blue = Reception Antenna Gain, Reception / dB 35 Equivalent Antenna Noise Temperature 20 Signal Power / Antenna Flange (pW) 24,26 System (2 x Nyquist-) Bandwidth / MHz 27,5 Noise Power / Antenna Flange (pW) 0,12 C / N (dB) / Antenna Flange 23,01 Feed Waveguide Attenuation / dB 3 C / N (dB) / Feed Waveguide Output 20,01 Gain / LNA (dB) 40 Noise Figure of LNA / dB 5 C / N (dB) / LNA Output 15,01 Noise Figure of Downconverter / dB 8 C / N (dB) / Downconverter Output 15,00 Environment Temperature / k 300 Equivalent System Noise Temperature / k 1913,19 G / T (dB/K) 2,18 ETSI ETSI TR 101 205 V1.1.2 (2001-07) 41 Table 5: Link Budget/User Terminal -> Base Station at 40 GHz P (W) at Antenna Flange / User Terminal 0,015 Red = Transmission Antenna Gain, Transmission / dB 35 EIRP (dBm) 46,76 Path Length / Km 1 Green = Path influence Rain Attenuation / dB/km 15 Power Flux at Reception Site /pW/mΒ² 113994 Background Noise Temperature / K 300 Aperture Hertzian Dipole / 40 GHz / mΒ² 6,7E-06 Blue = Reception Antenna Gain, Reception / dB 12 Equivalent Antenna Noise Temperature 20 Signal Power / Antenna Flange (pW) 12,13 System (2 x Nyquist-) Bandwidth / MHz 27,5 Noise Power / Antenna Flange (pW) 0,12 C / N (dB) / Antenna Flange 20,00 Feed Waveguide Attenuation / dB 3 C / N (dB) / Feed Waveguide Output 17,00 Gain / LNA (dB) 40 Noise Figure of LNA / dB 5 C / N (dB) / LNA Output 12,00 Noise Figure of Downconverter / dB 8 C / N (dB) / Downconverter Output 11,99 Environment Temperature / k 300 Equivalent System Noise Temperature / k 1913,19 G / T (dB/K) -20,82 ETSI ETSI TR 101 205 V1.1.2 (2001-07) 42 Table 5a: Link Budget/User Terminal -> Base Station at 40 GHz @ 1,54 MSy/s P (W) at Antenna Flange / User Terminal 0,0008 Red = Transmission Antenna Gain, Transmission / dB 35 EIRP (dBm) 34,03 Path Length / Km 1 Green = Path influence Rain Attenuation / dB/km 15 Power Flux at Reception Site /pW/mΒ² 6079,67 Background Noise Temperature / K 300 Aperture Hertzian Dipole / 40 GHz / mΒ² 6,7E-06 Blue = Reception Antenna Gain, Reception / dB 12 Equivalent Antenna Noise Temperature 20 Signal Power / Antenna Flange (pW) 0,65 System (2 x Nyquist-) Bandwidth / MHz 1,54 Noise Power / Antenna Flange (pW) 0,01 C / N (dB) / Antenna Flange 19,78 Feed Waveguide Attenuation / dB 3 C / N (dB) / Feed Waveguide Output 16,78 Gain / LNA (dB) 40 Noise Figure of LNA / dB 5 C / N (dB) / LNA Output 11,78 Noise Figure of Downconverter / dB 8 C / N (dB) / Downconverter Output 11,78 Environment Temperature / k 300 Equivalent System Noise Temperature / k 1913,19 G / T (dB/K) -20,82 ETSI ETSI TR 101 205 V1.1.2 (2001-07) 43 Table 6: Frequency Raster Future Ressource up to 43,5 GHz Frequency Raster 40,6 - 42,65 GHz (20 500 Segments Γ 100 KHz) Frequency Raster 42,85 - 43,4 GHz (5500 Segments Γ 100 KHz) Lower Ressource Edge: 40600 MHz Upper Ressource Edge: 43400 MHz Edge Guard Band: 100 MHz Edge Guard Band: 100 MHz Starting at/MHz: 40500,05 Stopping at/MHz: 43499,95 Raster - Increment/MHz: 0,1 Raster - Increment/MHz: 0,1 (=Segment Width) (=Segment Width) Segment Number: Segment Centre Frequency: Lower Edge Upper Edge Segment Number: Segment Centre Frequency: Lower Edge Upper Edge 1 40500,1 MHz 40500,05 40500,15 23500 42850 MHz 42849,95 42850,05 2 40500,2 MHz 40500,15 40500,25 . Sum: . 3 40500,3 MHz 40500,25 40500,35 . 5500 Upstreams . . . Segments . . Guard Band 28999 43399,9 MHz 43399,85 43399,95 . 740 40574 MHz 40573,95 40574,05 Beginning of Guard Band 29000 43400 MHz 43399,95 43400,05 . Sum: . . . . 741 40574,1 MHz 40574,05 40574,15 . 1000 . . . . 742 40574,2 MHz 40574,15 40574,25 . Segments . . . . 743 40574,3 MHz 40574,25 40574,35 29999 43499,9 MHz 43499,85 43499,95 . Sum: End of Guard Band . 195 Guard Band . Segments 935 40593,5 MHz 40593,45 40593,55 936 40593,6 MHz 40593,55 40593,65 937 40593,7 MHz 40593,65 40593,75 938 40593,8 MHz 40593,75 40593,85 . . . . . . 998 40599,8 MHz 40599,75 40599,85 999 Sum: 40599,9 MHz 40599,85 40599,95 195 End of Guard Band 1000 Segments 40600 MHz 40599,95 40600,05 1001 40600,1 MHz 40600,05 40600,15 1002 40600,2 MHz 40600,15 40600,25 . . . Downstreams . Sum Downstreams: . . 20500 Segments 1130 40613 MHz 40612,95 40613,05 1131 40613,1 MHz 40613,05 40613,15 . Sum: . . 20369 Downstreams . . Segments . 21499 42649,9 MHz 42649,85 42649,95 Beginning of Guard Band 21500 42650 MHz 42649,95 42650,05 . Sum: . . . . . 1000 . . . . . Segments . . . . 22499 42749,9 MHz 42749,85 42749,95 ETSI ETSI TR 101 205 V1.1.2 (2001-07) 44 Table 7: Security distance for 10 W/m2 at full load conditions Security Distance and Power Flux Density Security Distance and Power Flux Density Base Station User Terminal Number of Channels 100 Number of Channels P(W) per Carrier @ 27.5 Msymbols/sec 0,03 P(W) per Carrier @ 27.5 Msymbols/sec Comp. Power (W)/Antenna Flange/Base St. 3 Comp. Power (W)/Antenna Flange/Base St. Antenna Gain / dB 12 Antenna Gain / dB EIRP (dBm) 46,77 EIRP (dBm) Distance to Antenna / m 0,6 Distance to Antenna / m Power Flux /W/mΒ² 10,22 Power Flux /W/mΒ² ETSI ETSI TR 101 205 V1.1.2 (2001-07) 45 Table 7a: Frequency Ressource of a Cell ATM Framing Area of a big Town/kmΒ² 310,5 (Munich/Germany) Cell Area kmΒ² 3,14 Number of Cells 98 Number of Base Stations 392 Number of Houses 123478 (status: 2000) Av No Households/House 5,6 (status: 2000) Av No Households 691476,80 Av No Houses/Cell 1259 Upstreams Assumed Spect Ress/MHz 550 No of Polarizations 2 No of Sectors/Cell 4 Nyquist Rolloff 1,3 Perctg of Time parallel Use 31,20% (assumed, Limit of TDMA Operation) Frequency Ress/Cell/MHz 3384,62 Bits/Symbol 2 Payload Rate (ATM) 0,83 Av No Households/Cell 7050,4 Bit Rate/Household/Mbit/s 2,55 Downstreams with ATM OOB Channels Assumed Spect Ress/MHz 2050 No of Polarizations 2 No of Sectors/Cell 4 Nyquist Rolloff 1,3 Perctg of Time parallel Use 31,20% (assumed) Frequency Ress/Cell/MHz 12615,38 Bits/Symbol 2 Payload Rate (ATM) 0,92 Av No Households/Cell 7050,4 Bit Rate/Household/Mbit/s 10,50 ETSI ETSI TR 101 205 V1.1.2 (2001-07) 46 History Document history V1.1.1 May 2001 Publication V1.1.2 July 2001 Publication |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 1 Scope | The present document provides implementation guidelines for the use and implementation of the Digital Video Broadcasting (DVB) data broadcast service in a DVB digital broadcast environment including satellite-, cable-, MMDS- and terrestrial networks. The guidelines are intended to be highly recommended rules for the usage of the DVB data broadcast specification as put down in EN 301 192 [1]. As such, they facilitate the efficient and reliable implementation of data broadcast services. The rules apply to broadcasters, network operators as well as manufacturers. The rules are specified in the form of constraints on the data broadcast implementation. The specification of these functions in no way prohibits end consumer device manufacturers from including additional features, and should not be interpreted as stipulating any form of upper limit to the performance. NOTE: It is highly recommended that the end consumer device should be designed to allow for future compatible extensions to the DVB data broadcast specification. All the fields "reserved" (for ISO), "reserved_future_use" (for ETSI), and "user defined" in the EN 301 192 [1] should be ignored by end consumer devices not to make use of them. The "reserved" and "reserved_future_use" field may be specified in the future by the respective bodies, whereas the "user defined" field will not be standardized. This guidelines document uses the terminology defined in EN 301 192 [1] and should be read in conjunction with that document. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 2 References | For the purposes of this Technical Report (TR) the following references apply: [1] ETSI EN 301 192 (V1.3.1): "Digital Video Broadcasting (DVB); DVB specification for data broadcasting". [2] ISO/IEC 13818-1: "Information technology - Generic coding of moving pictures and associated audio information: Systems". [3] ETSI ETS 300 802: "Digital Video Broadcasting (DVB); Network-independent protocols for DVB interactive services. [4] ISO/IEC 13818-6: "Information technology - Generic coding of moving pictures and associated audio information - Part 6: Extensions for DSM-CC". [5] IETF RFC 791 (1981): "Internet Protocol", J. Postel. [6] ETSI EN 300 468: "Digital Video Broadcasting (DVB); Specification for Service Information (SI) in DVB systems". [7] ETSI EN 300 472: "Digital Video Broadcasting (DVB); Specification for conveying ITU-R System B Teletext in DVB bitstreams". [8] ETSI EN 300 743: "Digital Video Broadcasting (DVB); Subtitling system". [9] OMG Specification (1995): "The Common Object Request Broker: Architecture and Specification", Revision 2.0. [10] IETF RFC 1521 (1993): "MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies", N. Borenstein, N. Freed. [11] IETF RFC 1590 (1994): "Media Type Registration Procedure", J. Postel (Updates RFC 1521). [12] James Rumbaugh (1995): "OMT: The Object Model", JOOP 7.8. [13] IETF RFC 1112 (1988): "Host extensions for IP multicasting", S.E. Deering. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 7 [14] IETF RFC 2464 (1998): "Transmission of IPv6 Packets over Ethernet Networks", M.Crawford. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 3 Definitions and abbreviations | |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 3.1 Definitions | For the purposes of the present document, the following terms and definitions apply: broadcaster (SERVICE Provider): organization which assembles a sequence of events or programmes to be delivered to the viewer based upon a schedule component (ELEMENTARY Stream): one or more entities which together make up an event, e.g. video, audio, teletext, data Digital Storage Media - Command & Control (DSM-CC): Refers to the standard ISO/IEC 13818-6. LLC/SNAP: Refers to the standards ISO/IEC 8802-2 and ISO/IEC 8802-1. MPEG-2: Refers to the standard ISO/IEC 13818. Systems coding is defined in part 1. Video coding is defined in part 2. Audio coding is defined in part 3. multiplex: stream of all the digital data carrying one or more services within a single physical channel section: syntactic structure used for mapping all service information into ISO/IEC 13818-1 Service Information (SI): digital data describing the delivery system, content and scheduling/timing of broadcast data streams etc. NOTE: It includes MPEG-2 Program Specific Information (PSI) together with independently defined extensions. sub-table: sub-table is comprised of a number of sections with the same value of table_id, table_id_extension and version_number NOTE: The table_id_extension field is equivalent to the fourth and fifth byte of a section when the section_syntax_indicator is set to a value of "1". table: table is comprised of a number of sections with the same value of table_id transport stream: data structure defined in ISO/IEC 13818-1 NOTE: It is the basis of the Digital Video Broadcasting (DVB) standards. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 3.2 Abbreviations | For the purposes of the present document, the following abbreviations apply: API Application Portability Interface BIOP Broadcast Inter ORB Protocol bit/s bits per second bslbf bit string, left bit first CDR Common Data Representation CORBA Common Object Request Broker Architecture CRC Cyclic Redundancy Check DDB DownloadDataBlock message of DSM-CC DII DownloadInfoIndication message of DSM-CC DSI DownloadServerInitiate message of DSM-CC DSM-CC U-N DSM-CC User to Network DSM-CC U-U DSM-CC User to User DSM-CC Digital Storage Media - Command & Control DVB Digital Video Broadcasting EIT Event Information Table ETSI ETSI TR 101 202 V1.2.1 (2003-01) 8 GIF Graphics Interchange Format HTML HyperText Markup Language IDL Interface Definition Language IETF Internet Engineering Task Force IOR Interoperable Object Reference IP Internet Protocol JPEG Joint Photographic Experts Group LLC Logical Link Control MAC Medium Access Control MPEG Moving Pictures Expert Group MTU Maximum Transport Unit NPT Normal Play Time NSAP Network Service Access Point OMG Object Management Group OMT Object Modelling Technique ORB Object Request Broker PAT Program Association Table PCR Program Clock Reference PES Packetized Elementary Stream PID Packet Identifier PLL Phase Locked Loop PMT Program Map Table ppm parts per million PSI Program Specific Information PTS Presentation Time Stamp RFC Request For Comments SDT Service Description Table SI Service Information SIS Systems for Interactive Services SNAP SubNetwork Attachment Point TS Transport Stream uimsbf unsigned integer, most significant bit first ETSI ETSI TR 101 202 V1.2.1 (2003-01) 9 |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4 Rules of operation | This clause contains some recommendations on the usage of the Digital Video Broadcasting (DVB) data broadcasting specification. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.1 Introduction | Figure 4.1 gives an overview of the data broadcast specification as put down EN 301 192 [1]. MPEG-2 Transport Stream PES Section DVB data piping service specific Application level interface : Service specific : DVB defined : Other standards (IETF,ISO) : DSM-CC defined DVB data streaming service specific DVB multi protocol service specific datagram spec. (eg IP/IPX) DSM-CC data service specific DSM-CC data service specific DSM-CC object DVB object DVB data carousel service specific Applications Data Piping Application area: data_broadcast_id: 0x0001 Data Streaming 0x0002 0x0003 0x0004 Multi-protocol encapsulation 0x0005 Data Carousel 0x0006 Object Carousel 0x0007 Registered service t.b.d DSM-CC priv. data Figure 4.1: Graphical overview and relation to other standards The basis of the complete specification is formed by the MPEG-2 Transport Stream (TS) as defined in ISO/IEC 13818-1 [2]. Data information can be transported within this MPEG-2 TS by means of application areas. The application areas are: β’ Data piping. β’ Data streaming. β’ Multiprotocol encapsulation. β’ Data carousel. Furthermore in figure 4.1 the object carousel is depicted. This carousel is used by the specification for Network Independent Protocols for Interactive Services ETS 300 802 [3]. A registered service is shown on the right hand side of the figure. DVB allows to register private implementations for data broadcast services, as described in annex A of EN 301 192 [1]. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 10 Figure 4.1 shows what is standardized by which body. ISO has standardized the MPEG-2 TS in ISO/IEC 13818-1 [2] and the DSM-CC framework in ISO/IEC 13818-6 [4]. IETF has standardized the Internet Protocol (IP) in RFC 791 [5]. DVB has specified within the data broadcast specification EN 301 192 [1] the DVB data piping, DVB data streaming, DVB multiprotocol encapsulation, DVB data carousel and DVB object carousel parts. Within figure 4.1 the encapsulation of the Internet Protocol (IP) is just an example. Other protocols can also be encapsulated. As shown in figure 4.1, the specification for data broadcast EN 301 192 [1] specifies different service levels for all application areas. The data piping specification does not give much information on how to get the data out of the MPEG-2 TS. It more or less only specifies how to put data into MPEG-2 Transport Stream packets. In comparison with the other application areas a lot of service specific hard- and/or software has to be built to get a service running. The data streaming specification gives some more functionality, especially for timing. It is possible to do asynchronous data broadcast, synchronized broadcast or synchronous broadcast. The specification is based on PES packets as defined in MPEG-2 ISO/IEC 13818-1 [2]. The multiprotocol encapsulation, data carousel and object carousel application areas specifications are all built using the DSM-CC framework of MPEG-2 ISO/IEC 13818-6 [4]. It is based on MPEG-2 private sections as defined in MPEG-2 ISO/IEC 13818-1 [2]. DVB has added specific information to get the framework working in the DVB environment, especially in conjunction with the Service Information specification EN 300 468 [6]. In the specification for data broadcast EN 301 192 [1], every application area is defined by two parts as shown in figure 4.2. Transport Control Application Areas MPEG 2 TS #a #b #c #d Control: SI and PSI Transport: Databroadcast transport specification Figure 4.2: Transport and control specification parts The control specification is part of the EN 300 468 [6] Service Information specification, the transport part of the specification is part of the EN 301 192 [1] data broadcast specification. The following clauses give implementation guidelines how to use the different application areas. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.2 Selection of the appropriate profile | As shown in figure 4.1 there are different ways to transmit data via MPEG-2 DVB Transport Streams. The mechanisms have different characteristics concerning filtering, overhead, size, etc. The selection of the appropriate mechanism has to be based on the specific requirements of the target application. The level of detail of the specification varies for the different profiles. In case of Multiprotocol Encapsulation (see EN 301 192 [1], clause 7) and Data Carousels (see EN 301 192 [1], clause 9) the specification is very detailed, which only requires very few application specific definitions, in case of the other profiles there is much freedom. Furthermore, it is possible to use application areas for other purposes than the recommended ones; e.g. a data carousel like application can be based on top of Data piping and an IP broadcast one on top of Data streaming. Such arrangements are of course part of service specific choices. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.2.1 Fragmentation of datagrams | Generally data of any kind of protocols are transmitted in packetized form ("datagrams"). These datagrams may have different length. If the data are not packetized or the packetization method is irrelevant or hidden to the DVB transmission chain the most appropriate way of transmission is the Data Pipe (see EN 301 192 [1], clause 4). ETSI ETSI TR 101 202 V1.2.1 (2003-01) 11 On the layer of MPEG-2 Transport Stream data are transmitted within packets with a fixed length of 188 bytes (184 bytes payload), therefore datagrams of higher layers must be fragmented at the transmission side and be re-assembled at the reception. For fragmentation of the datagrams there are three possible ways (see also figure 4.1): β’ Private mechanisms based on the Data Pipe. β’ MPEG-2 Packetized Elementary Streams (PES). β’ MPEG-2 Sections. MPEG-2 PES provides a mechanism to transmit datagrams of variable size with a maximum length of 64 kbytes. Additionally it provides the facility to synchronize different data streams accurately (as used in MPEG for synchronization of Video and Audio), therefore it was chosen by DVB for the transmission of synchronous and synchronized but also asynchronous data streams (see EN 301 192 [1], clauses 5 and 6). MPEG-2 Sections can be used to transmit datagrams of variable size with a maximum length of 4 kbytes. The transmission is asynchronous. MPEG-2 Sections are built in a way that MPEG-2 demultiplexers available on the market can filter out single sections in hardware which may reduce the required software processing power of the receiver. This is the main reason why the MPEG-2 Sections have been chosen as the mechanism for the transmission of encapsulated protocols and data carousels. For data broadcasting services in the DVB framework the data_broadcast_id_descriptor (EN 300 468 [6]) can be present in the PMT, i.e. use of this descriptor is optional. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.3 Data Pipe | The Data Pipe is an asynchronous transportation mechanism for data. The data are inserted directly in the payload of MPEG-2 Transport packets. There is no mechanism for fragmentation and reassembly of datagrams defined. This - if required - is part of the application definition. For instance, the payload_unit_start_indicator could be used to signal the start of a datagram in a packet while the transport_priority field could signal the end of a datagram. The continuity_counter shall be used as defined by MPEG (ISO/IEC 13818-1 [2], clause 2.4.3). |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.3.1 Usage of the adaptation field | The main use of the Adaptation Field is stuffing. However, it is possible to use it for other purposes, e.g. the transmission of PCR. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.4 Asynchronous/Synchronized/Synchronous Data Streaming | |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.4.1 Usage of the adaptation field | According to ISO/IEC 13818-1 [2], clause 2.4.3 a PES packet always has to start at the first payload byte of an MPEG-2 Transport Packet. This means that for PES packets which are not aligned with the MPEG-2 Transport Packet there is stuffing necessary. Since MPEG only allows stuffing bytes at the end of the packet for sections and not for PES (see ISO/IEC 13818-1 [2], clause 2.4.3.3) stuffing can only be achieved by using Adaptation fields. This is no real constraint for the performance of a decoder since most demultiplexer implementations provide the automatic extraction of Adaptation Fields and therefore no additional processing power is required. An Adaptation Field that is only used for stuffing can be created by setting all adaptation field flags (discontinuity_indicator, random_access_indicator, elementary_stream_priority_indicator, PCR_flag, OPCR_flag, splicing_point_flag, transport_private_data_flag, adaptation_field_extension_flag) to "0" and inserting the number of required stuffing bytes. The elementary_stream_priority_indicator and the adaptation_field_extension_flag shall be set to zero, since the affiliated features have no meaning for Data Streaming. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 12 |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.4.2 Asynchronous Data Streaming | Asynchronous Data Streaming is used in the case that the PES mechanism is of advantage for applications that need the asynchronous transmission of datagrams. Since no synchronization is necessary for this kind of transmission the stream_id "private_stream_2" (see ISO/IEC 13818-1 [2]) has been chosen which implicitly excludes the usage of the PES packet header fields. Therefore the PES_packet_length field is immediately followed by the datagram. The definition of the datagram format is part of the private implementation ant therefore not subject of the DVB specification. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.4.3 Synchronous/Synchronized Data Streaming | In order to meet the requirements of the Synchronous and Synchronized Data Streaming an additional header, specific to this DVB application profile has been defined (see EN 301 192 [1], table 1). The field stream_id shall be set to "private_stream_1", allowing for the usage of the PES header fields, especially the PTS. Usage of the time stamps requires the definition of Access Units. Since this is application dependant it has not been defined within the DVB data broadcasting specification. The first byte of this header (which is from MPEG-2 PES point of view the first payload byte) contains the data_identifier. It is defined in accordance with the specifications for embedding of EBU-data (EN 300 472 [7]) and DVB-subtitling (EN 300 743 [8]) and indicates the type of Data Streaming (synchronous /synchronized). A combination of Synchronized and Synchronous Data Streaming in the same PES packet is not allowed. However, both types of streaming data can be carried as part of a same program in separate PID's. The field sub_stream_id may be used for private definition. The two flags PTS_extension_flag and output_data_rate_flag indicate the existence of an output data rate field and of a field for PTS extension. The usage of these fields is explained below. The PES_data_packet_header_length indicates the length of the header and allows the addition of private bytes in the header. The DTS field in PES header is of no use while the PTS shall be coded in the same way as defined by MPEG in ETS 300 802 [3]. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.4.4 Synchronous Data Streaming | Synchronous data streaming may be used if the output data rate at the receiver side needs to be very accurate. The receiver clock is synchronized by the PCR. The 9 bit PTS_extension is needed to position data access units (a bit, a byte or few bytes depending on how one defines access units) very accurately over a large range of data rates (kbit/s to Mbit/s). The 9 bits extends the accuracy of the PTS clock from 11 Β΅s to the same accuracy as a 27 MHz clock (37 ns). Precise positioning of the data is required if multiple data decoders receiving the same data services (and knowing the latency through the process) have to output the data at the same time in an aligned way, or if it is required to maintain synchronization in the data output stream following a temporary loss of signal. The field output_data_rate is used in order to specify the output data rate for the synchronous data stream. With the 28 bit accuracy (instead of the 400 bit/s resolution of 22 bit ES_rate in PES header) it is possible to implement PLL (with clock down conversion) with a ratio of data output rate to 27 MHz (Β±30 ppm) covering a wide range of data rates. The output_data_rate field conveys the bit rate of the regenerated signal for a synchronous data stream. The encoding of the bit rate of the data stream into the output_data_rate field depends on the application. Applications which require bit rates which are a multiple of 1 bit per second may encode the data streams bit rate into the output_data_rate field directly with the units of output_data_rate as bits/second. Applications which require a continuous range of bit rates to be regenerated within the 30 ppm tolerance specified by MPEG for the 27 MHz system_clock_frequency may encode the bit rate of the data stream into the output_data_rate field as: β’ output_data_rate = bit rate x M/system_clock_frequency; ETSI ETSI TR 101 202 V1.2.1 (2003-01) 13 where M is chosen to be a number sufficiently large to express the range of bit rates required for the application with the desired bit rate accuracy. The practical range of bit rates for synchronous data streaming with a system_clock_frequency of 27 MHz is 1 bit/s to 27 Mbit/s. Note that the decoder model described in clause 12 of EN 301 192 [1] is not necessarily applicable if the output data rate field is used. ES_rate in the PES header can be used without the output_data_rate field in the PES data_packet for applications where the 400 bit/s accuracy of ES_rate is adequate (e.g. T1 and E1). If both ES_rate and output_data_rate are present in an encoded stream, the decoder can use either of the rates. The recommended buffer size for synchronous data streaming is 4 800 byte. This gives sufficient capacity for a typical maximum multiplexing jitter of 4 ms and a bit rate up to 9 Mbit/s. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.4.5 Synchronized Data Streaming | Synchronized Data Streaming is used when the data stream shall be synchronized with another MPEG-2 PES stream. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.5 Multiprotocol encapsulation | |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.5.1 Overview | The multiprotocol encapsulation provides a mechanism for transporting data network protocols on top of the MPEG-2 Transport Streams in DVB networks. It has been optimized for carriage of the Internet Protocol (IP) (RFC 791 [5]), but can be used for transportation of any other network protocol by using the LLC/SNAP encapsulation. It covers unicast (datagrams targeted to a single receiver), multicast (datagrams targeted to a group of receivers) and broadcast (datagrams targeted to all receivers). 48-bit MAC addresses are used for addressing receivers. However, DVB does not specify how the MAC addresses are allocated to the receivers. Due to the broadcast nature of DVB networks, security of the data is very important. The encapsulation allows secure transmission of data by supporting encryption of the packets and dynamically changing MAC addresses. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.5.2 Data transport | The datagrams are transported in datagram_sections which are compliant to the DSMCC_section format for private data. The section format provides an efficient format for mapping the datagrams to the MPEG-2 Transport Stream packets and support filtering of datagrams based on the MAC address using existing hardware or software demultiplexers. The section format permits fragmenting datagrams into multiple sections. If the length of the datagram is less or equal than 4 080 bytes (including the possible LLC/SNAP header), the datagram shall be sent in one section. In case of IP and the LLC/SNAP header being omitted, the MTU shall be set to 4 080 bytes or less, so that the datagrams will never be fragmented. In case of IP and the LLC/SNAP header being present the MTU shall be set to 4 074 or less. The MAC address has been divided into 6 bytes that are located in two groups. The reason for this is that the bytes 5 and 6 are in place of the table_id_extension field of the DSMCC_section while bytes 1, 2, 3 and 4 are in the payload area of the DSMCC_section. 1 2 3 4 5 6 48-bit MAC address byte: table id .... section length MAC address 6 reserved last section number MAC address 5 MAC address 4 MAC address 3 MAC address 2 MAC address 1 .... .... section : MSB LSB ETSI ETSI TR 101 202 V1.2.1 (2003-01) 14 Some demultiplexers are able to filter bytes 5 and 6 with hardware while filtering bytes 1, 2, 3 and 4 is done in software. It is recommended that the two bytes of the MAC address which most probably differentiate the receivers are put to the bytes 5 and 6. This is normally the case with IEEE MAC addresses and it is recommended that all MAC addresses are constructed in this way. Payload scrambling is controlled by a 2-bit field payload_scrambling_control. If the value of these bits is '00', the payload is not scrambled. If the payload is scrambled, the scrambling algorithm is private to the service. The mechanism how the scrambling method is signalled to the receiver is not defined by DVB. MAC address scrambling provides further security by dynamically changing MAC addresses. By changing the control word that is used for scrambling the MAC addresses periodically, monitoring of the stream can be prevented as the destination of a particular datagram can not be determined by observing the MAC addresses. It also strengthens the security as collecting datagrams destined to a single receiver is difficult. The delivery mechanism of control words used for scrambling the MAC addresses is not defined by DVB. Address scrambling is controlled in the section header by a 2-bit field address_scrambling_control. If the value is these bits is '00', the MAC address is not scrambled. It should be noted that using MAC address scrambling without payload scrambling is of no use, since the protocol address that is part of the datagram is visible in the clear. The LLC/SNAP encapsulation provides a multiprotocol encapsulation that can be used for carrying any network protocol, including IP. There is an optimization for carrying IP that allows transmitting IP datagrams without the LLC/SNAP header. This is controlled by the LLC_SNAP_flag bit in the section header. If the value of the bit is '0', the payload contains a bare IP datagram. If the value of the bit is '1', the payload contains an LLC/SNAP encapsulation which consists of the LLC/SNAP structure LLC_SNAP() followed by the datagram bytes. The optimized way of carrying IP can be used for both IPv4 and IPv6. The section_number and last_section_number fields must both be '0' when carrying the IP protocol. The section may contain stuffing after the datagram. The stuffing bytes may be used, for example, for making the payload of the section to be multiple of a block size when a block encryption code is used. The value of these bytes is not specified and in case of payload encryption they should not be assigned a fixed value as it would help breaking the encryption. The datagram_section has a checksum or a CRC_32 in the end depending on the value of the section_syntax_indicator. It is recommended to use the CRC_32 as it provides a slightly better protection against bit errors as it can be checked by hardware in most hardware demultiplexers while the checksum has to be normally checked by software. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.5.3 Information in the SI | For services using multiprotocol encapsulation, the data_broadcast_descriptor shall be present in the SDT or the EIT. The multiprotocol_encapsulation_info structure [1] is carried in the selector_byte field. MAC_address_range field is used for signalling to the receiver which bytes of the MAC_address are significant for filtering. The significant bytes of the MAC address are at the least significant end of the MAC address. The MAC_IP_mapping_flag signals whether the mapping of multicast IP addresses to MAC addresses is done according to RFC 1112 [13] for IPv4 multicast addresses and RFC 2464 [14] IPv6 multicast addresses. It should be noted that as DVB does not define that the MAC addresses are used as defined by IEEE, alternative, possibly more optimized, mappings are allowed. Alignment indicator indicates if the datagram_section is 8-bit aligned or 32-bit aligned to the Transport Stream packets. 8-bit alignment essentially means that it is not aligned. Alignment is useful in implementations which input Transport Stream packets and rely on the beginning of the section being on a 32-bit boundary for enabling efficient comparison operations in filtering. The alignment is performed using the adaptation field of the Transport Stream packet and / or stuffing bytes at the end of the sections. The max_sections_per_datagram field defines the maximum number of section that are used for carrying a single datagram (for IP this is restricted to be 1). This defines the maximum length of the datagram. Typically a receiver has to combine the fragments of the datagram before passing it on, so this field defines the size of the buffer that the receiver has to have for combining a datagram of the maximum length. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 15 |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6 Data carousel | |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.1 Introduction | The data carousel is a transport mechanism that allows a server (the broadcast component of an application) to present a set of distinct data modules to a decoder (a program that is run by a receiver) by cyclically repeating the contents of the carousel, one or more times. If an application decoder wants to access a particular module from the data carousel, it may simply wait for the next time that the data for the requested module is broadcast. A good example of the data carousel concept that is widely understood is the Teletext system. In this system, a complete set of Teletext pages is cyclically broadcast in some of the lines of an analogue video signal that are not part of the active picture. When users requests a page, they must usually wait for the next time the page is broadcast. The maximum length of time the user has to wait can be determined by the time it takes for a complete cycle of the carousel, which in turn can be deduced from the size of the carousel and the rate at which data can be broadcast. M3-1 M3-2 M8-3 M8-0 M8-1 block_size cycle_time M2: "file1" M3: "file2" M8-7 M8-5 M8-6 M8-4 M2-0 M3-0 M8-8 M8-2 download data message (MX-Y): DownloadDataBlock () X = module_id Y = block_number download control message: DownloadServerInitiate () or DownloadInfoIndication () M8: "file3" M2_size M3_size M8_size Figure 4.3: Cyclic transmission of information in a data carousel Within a data carousel the data is structured into Modules, depicted in figure 4.3 as M2, M3 and M8. This could simply be the contents of a number of files, say "file1", "file2" and "file3" as in this example. Each Module is divided up to form the payload of one or more download data messages each defined using the DSM-CC DownloadDataBlock syntax. The number of such messages depends on the size of the Module and the maximum payload of each download data message. Information describing each Module and any logical grouping is provided by download control messages, defined using either the DSM-CC DownloadServerInitiate or DownloadInfoIndication syntaxes as appropriate. In this example each download message has been inserted only once and DownloadDataBlocks from the same Module have been inserted adjacent to one another and in order. There are however, no restrictions on how often a particular message is inserted into a single loop of the carousel and the order and relative position of messages. This allows the data carousel to be created in whatever way best suits a particular use. In addition the frequency and order of insertion of messages into the data carousel do not need to be fixed and can change dynamically as required. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 16 |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.2 Data carousel Groups and SuperGroups | A logically consistent set of Modules within the data carousel may be clustered together to form a Group as defined in EN 301 192 [1]. The description of the Modules in the Group is provided by a DownloadInfoIndication message. There are no restrictions on how Modules are associated into Groups and, in particular, one Module may be a member of more than one Group. Groups may be clustered together to form a SuperGroup as defined in EN 301 192 [1]. The description of the Groups in the SuperGroup is provided by a DownloadServerInitiate message. NOTE: A SuperGroup may contain any number of Groups, even only one. The structure of the data carousel (in Groups and SuperGroups) does not necessarily reflect the structure of the content. For purpose of clarification the exact DSM-CC messages are depicted in annex A. Annex B gives information about the inclusion of DSM-CC messages in MPEG-2 sections. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.3 Use of the one-layer data carousel | If the data carousel consists only of a single Group and the complete description of the Group can be contained within a single DownloadInfoIndication message (i.e. one-layer of control information) then a one-layer data carousel can be used. In all other cases a two-layer data carousel should be used. The DownloadInfoIndication message is the only download control message in the data carousel and is referred to as the top-level control message. NOTE: Although there is only one defined download control message there may be multiple insertions of the same message in a single loop of the data carousel. An example where a one-layer data carousel would be appropriate would be the delivery of a small HTML based application (say 10 to 20 Modules) authored to support HTML V1.0 only. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.4 Use of the two-layer data carousel | A two-layer data carousel has one or more DownloadInfoIndication messages and a single DownloadServerInitiate message (i.e. two-layers of control information). The DownloadServerInitiate message is referred to as the top-level control message. A two-layer data carousel should be used in the situations described below. These are the Guidelines for specific circumstances and can be mixed together as necessary. 4.6.4.1 The data carousel consists of a single group the description of which is too large for a single DownloadInfoIndication message In this situation as many DownloadInfoIndication messages as necessary should be used to describe all the Modules in the large Group. This effectively divides the large Group up into a number of smaller Groups each defined by its own DownloadInfoIndication message. Since a data carousel can only have a single top-level control message this imposes the use of a two-layer carousel. To be able to recreate the original large Group the new smaller Groups need to be linked together. This is achieved by including group_link_descriptor() in the description of each of the new small Groups in the DownloadServerInitiate message. An example would be the delivery of a large HTML based application (say 500+ Modules) authored to support HTML V1.0 only. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 17 4.6.4.2 The data carousel delivers a single version of an application but supports a number of different receiver profiles In this situation the data carousel should consist of a Group for each different receiver profile that is to be supported, with common Modules shared amongst more than one Group. An example would be the delivery of a small HTML based application (say 10 to 20 Modules) authored to support HTML V1.0, V2.0 and V3.0. The data carousel would be structured as a SuperGroup containing three Groups. Many of the Modules would be common to all three Groups, e.g. GIFs and JPEGs, but some would be specific to only one Group, e.g. a particular HTML version of a page. The groupCompatability structure associated with each Group would be used to determine which Group should be used for a given receiver profile. 4.6.4.3 The data carousel simultaneously delivers more than one version of an application for a single receiver profile In this situation the data carousel should consist of a Group for each version of the application being delivered. Since there is no Group versioning mechanism available, the DownloadServerInitiate message should only reference the Group that describes the most recent version. This means that new viewers who access the data carousel via the top-level control message will automatically use this version. If a new version of the application is to be added to the data carousel whilst still delivering existing versions then a new Group should be created. The DownloadServerInitiate message should be updated to remove any reference to the previous "most recent" Group and now reference the new "most recent" Group. This imposes the restriction that the receiver must store locally the relevant top-level (DownloadServerInitiate) control message if it wishes to continue to access an older version still being broadcast. NOTE: The transactionId field in the data_broadcast_descriptor could be used to point directly at the DownloadInfoIndication message that describes an older version of the Group still in the data carousel. An example would be using the receiver as a software download interface to a mass storage device where it is desirable to continue to broadcast a large file to completion even though a more recent version of the same file is also being broadcast. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.5 Assignment and use of transactionId values | The use of the transactionId in the DVB data carousel is inherited from its use as defined by the DSM-CC specification, and as such it can appear somewhat complex. The transactionId has a dual role, providing both identification and versioning mechanisms for download control messages, i.e. DownloadInfoIndication and DownloadServerInitiate messages. The transactionId should uniquely identify a download control message within a data carousel, however it should be "incremented" whenever any field of the message is modified. NOTE: The term "incremented" is used in the DSM-CC specification. Within the scope of the DVB data carousel this should be interpreted as "changed". The transactionId has been split up into a number of sub-fields defined in table 4.1. This reflects the due role of the transactionId (outlined above) and constraints imposed by DVB to reduce the minimum level of filtering required by receivers. However, to increase interoperability the assignment of the transactionId has been designed to be independent of the expected filtering in target receivers. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 18 Table 4.1: Sub-fields of the transactionId Bits Value Sub-field Description 0 User-defined Updated flag This must be toggled every time the control message is updated 1 to 15 User-defined Identification This must and can only be all zeros for the top-level control message. All non-top-level control messages must have one or more non-zero bit(s). 16 to 29 User-defined Version This must be incremented/changed every time the control message is updated. 30 to 31 Bit 30 - zero Bit 31 - non-zero Originator This is defined in the DSM-CC specification (ISO/IEC 13818-6 [4]) as 0x02 if the transactionId has been assigned by the network - in a broadcast scenario this is implicit. Due to the role of the transactionId as a versioning mechanism any change to any message in the data carousel will cause the transactionId of the top-level control message to be incremented. The change propagates up through the structure of the data carousel as follows. Any change to a Module will necessitate incrementing its moduleVersion field. This change must be reflected in the corresponding field in the description of the Module in the DownloadInfoIndication message(s) that describes any Group(s) that includes it. Since a field in the DownloadInfoIndication message is changed its transactionId must be incremented to indicate a new version of the message. Again (in the case of a two-layer data carousel) this change must be reflected in the corresponding field in the description of the Group in the DownloadServerInitiate message that describes the SuperGroup. Since fields in the DownloadServerInitiate message have changed its transactionId must also be incremented. This is useful since just by looking at the transactionId of the top-level control message a change to any message in the data carousel can be detected. If the transactionId of any control message is referenced in the corresponding field of a data_broadcast_descriptor in SI (see EN 300 468 [6], clause 6.2.6) then this will need to be updated to reflect any changes. One consequence of this is that changes to the content of the data carousel may necessitate re-acquisition of the modified SI tables. Due to the repetition rate of SI which can be up to 2 s, this may be an undesired side-effect that reduces the speed of response of dynamic data services. To avoid this behaviour the value of 0xFFFFFFFF for the contents of the transactionId field in the data_broadcast_descriptor can be used to indicate any top-level control message is valid. The encapsulation of download control messages within MPEG-2 Transport Streams is defined in the DSM-CC specification. It specifies that the 2 least significant bytes of the transactionId field are copied into the table_id_extension field of the DSMCC_section header. This means that if the PID on which the DVB data carousel is being broadcast is known the top-level control message can be located without knowing its transactionId by setting up the section filters for table_id = 0x3B (download control messages) and table_id_extension = 0x0000 or 0x0001. Table 4.1a reflects the encoding of the section header fields for the different message type. Table 4.1a: Encoding of DSM-CC section_fields Message table_ id table_id_extension version_ number section_ number last_section_ number Download-ServerInitiate (DSI) 0x3B two LSB bytes of transaction_id of DSI 0x00 0x00 0x00 Download-InfoIndication (DII) 0x3B two LSB bytes of transaction_id of DII 0x00 0x00 0x00 Download-DataBlock (DDB) 0x3C moduled module Version % 32 blockNumber % 256 Max(section_ number) |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.6 Use of descriptors specific to the DVB data carousel | All descriptors described in this clause are optional. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.6.1 Type descriptor | With this descriptor the type of the Module or Group of the data carousel is transmitted. Its use is proprietary to the service provider. A string of 'char' fields specifies the type of the module following the Media Type specifications RFC 1521 [10] and RFC 1590 [11]. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 19 |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.6.2 Name descriptor | With this descriptor the name of the Module or Group in the data carousel is transmitted. Its use is proprietary to the service provider. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.6.3 Info descriptor | With this descriptor information about the Module or Group in the data carousel is transmitted. Its use is proprietary to the service provider. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.6.4 Module link descriptor | The module_link_descriptor provides information about which Modules of one group are to be linked to get a complete piece of data out of the carousel. Within this descriptor two fields, the position field and the module_id field together indicate what is the first module in the list (position = 0x00, module_id = next module number), what is the next module (position = 0x01, module_id = next module number) and what is the last module (position = 0x02) in the list in case of a multi-module linkage. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.6.5 CRC32 descriptor | With this descriptor CRC-32 calculation over a complete Module is indicated. The CRC-32 bits of the Module are part of the descriptor. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.6.6 Location descriptor | The location descriptor in a DownloadServerInitiate message indicates on which PID a Group of the data carousel can be found. The DownloadInfoIndication message of the Group to be found has to be on that PID. The same mechanism can be used in the DownloadInfoIndication message to find all the Modules on different PIDs. This is a very powerful means to operate with Groups and Modules for different kinds of users. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.6.7 Estimated download time descriptor | The descriptor for estimated download time has been introduced in order to provide an indication to the receiver of the time it will take to download a Module or Group. Some care is needed in how it is used. The download time will obviously be sensitive to the bitrate available to deliver the data carousel. This may be a problem where the data carousel is produced separately from playout of that carousel. If playout of the same data carousel is at one bitrate on one day (e.g. 1 Mbit/s) and at another bitrate on the next day (e.g. 2 Mbit/s) then the estimated download time can not be correct for both (or even either!). NOTE: One approach would be to calculate the value for estimated download time based on the minimum playout bitrate. Obviously it may be more practical in some cases for the receiver to simply indicate how much of the data has been received based on received messages. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.6.8 Group link descriptor | The description of the Modules in a Group is provided by a DownloadInfoIndication message. The number of Modules that may be described is determined by the maximum size of such a message and the size of the description of each Module. The encapsulation of such download control messages within MPEG-2 sections limits the maximum size to just under 4 kbytes. The size of a simple Module description (say basic information and a name descriptor of 30 bytes) is about 40 bytes. This means that the DownloadInfoIndication message can describe about 100 Modules which will be sufficient in most cases but not all. In the later situation as many DownloadInfoIndication messages as necessary should be used to describe all the Modules in the large Group. This effectively divides the large Group up into a number of smaller Groups each defined by its own DownloadInfoIndication message. To be able to recreate the original large Group the new smaller Groups need to be linked together. This is achieved by including group_link_descriptor() in the description of each of the new small Groups in the DownloadServerInitiate message. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 20 |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.6.9 Private descriptor | If a service provider has a need for a private descriptor the syntax of the private descriptor in (EN 301 192 [1], clause 9.2.10) shall be used. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.6.10 Compressed module descriptor | Presence of the compressed_module_descriptor indicates that the data in the module has the "zlib" structure as defined in RFC 1951. The ZLIB structure is defined as: zlib structure(){ No. of bytes compression_method 1 flags_check 1 compressed_data n check value 4 } |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.7 Information in the SI and PSI | Access to the data carousel can be achieved via descriptors in either SI or PSI. This provides some flexibility in how the service is identified. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.7.1 Descriptor in SI | For services using data carousel(s), the data_broadcast_descriptor shall be present in the SDT or the EIT, i.e. use of this descriptor is mandatory. The data_broadcast_id field shall be set to 0x0006 to indicate the use of the DVB data carousel. The component_tag will identify the PID on which the data carousel is broadcast by association with a similar tag in the stream_identifier_descriptor() for the particular stream in the PMT. The data_carousel_info structure (EN 301 192 [1]) is carried in the selector_byte field. The carousel_type_id indicates which kind of data carousel is used (figure 4 in EN 301 192 [1]). The use of the transaction_id is depicted above in clause 4.6.4. The time_out_value_DSI and time_out_value_DII gives some indication to the receiver of how long it shall wait before assuming an error condition. The leak_rate is included for optimization of the receiving device. By giving the leak_rate a decoder is able to compute whether a service can be decoded. The leak rate may also be given in a smoothing_buffer_descriptor or a maximum_bitrate_descriptor in which case the values given in both descriptors shall be consistent. However, the usage of a maximum bitrate descriptor is not recommended". The advantages of using an SI based access to the carousel instead of the PSI one are: β’ The transactionId can be used to explicitly identify the top-level control message in the data carousel. β’ By including the transactionId field in this descriptor, updates to the data carousel (which will cause a change in transactionId) can be detected by filtering on just the SI. NOTE: This behaviour can be avoided by using the special value of transactionId, 0xFFFFFFFF, as described in clause 4.6.4. β’ The descriptor does not consume any space in the PSI tables (which may be a scarce resource). The disadvantage of using an SI based access to the carousel instead of the PSI one is: β’ The repetition period of SI can be up to 2 s which can introduce delay to the initial access of the service. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 21 |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.6.7.2 Descriptors in PSI | For services using data carousel(s), the data_broadcast_id_descriptor can be present in the PMT, i.e. use of this descriptor is optional. The data_broadcast_id field shall be set to 0x0006 to indicate the use of the DVB data carousel. The advantage of using this mechanism is that: β’ The maximum repetition period of PSI is only 0,1 s which allows fast initial access to the service. The disadvantages of this mechanism are that: β’ There is no transactionId field so explicitly identify the top-level control message. As such only download control messages from a single data carousel may be transported on the identified elementary stream. β’ The descriptor does not provide any information about the time-out period for download control messages. This information must still be obtained from the descriptor in SI. β’ The descriptor consumes some space (albeit small) in the PSI tables. β’ The descriptor in SI must still be included as well. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7 Object carousel | |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.1 Introduction | A DSM-CC object carousel facilitates the transmission of a structured group of objects from a broadcast Server to broadcast Receivers (Clients) using directory objects, file objects and stream objects. The actual directory and content (object implementations) are located at the Server. The Server repeatedly inserts the mentioned objects in the DVB compliant MPEG-2 Transport Stream using the object carousel protocol. The object carousel is part of a DVB Service as shown in figure 4.4. The transmitted directory and file objects contain the content of the objects, while the transmitted stream objects are references to other streams in the broadcast. The stream objects may also contain information about the DSM-CC events that are broadcast within a particular stream. DSM-CC events can be broadcast with regular stream data and can be used to trigger DSM-CC applications. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 22 Directory File Stream (reference) Stream (reference) File File File Directory Directory Stream+Events (references) Directory AV Program Object Carousel StreamEvents AV Program DVB Service DVB Service Figure 4.4 Example of including object carousel specification in DVB Services Multiple Clients can recover the object implementations by reading the repeatedly transmitted carousel data, hence mimicking the Server's objects in a local object implementation. The objects in the carousel offer Clients a way to access applications and content used by these applications, more or less as if there was an interactive connection with the Server. The following sections provide guidelines regarding the implementation and use of DSM-CC U-U object carousels in DVB-compliant broadcast networks and in interactive systems compliant to DVB-SIS (ETS 300 802 [3]). This clause focuses on the following subjects: β’ Platform independence; β’ Encoding of BIOP control structures used in U-U object carousels; β’ Encoding of BIOP data messages used in U-U object carousels; β’ Encoding of Download Data Carousel messages; β’ Encoding of DSM-CC sections; β’ Use of PSI descriptors for object carousels; and β’ Use of SI descriptors for object carousels. The scope is illustrated in figure 4.5 by the area surrounded by thick lines. Figure 4.5 shows the protocol stacks defined by DVB-SIS for both Broadcast and Interactive Networks. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 23 Broadcast Network Interactive Network U-U API MPEG-2 TS DSM-CC Sections Download Data Carousel Object Carousel (BIOP) DSM-CC U-U Application(s) PPP-MP IP TCP UNO-CDR / RPC (IIOP) Figure 4.5: Place of object carousel protocols in the DVB-SIS framework |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.2 Platform independence | |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.2.1 Overview | The object carousel specification is platform-independent and compatible with the DSM-CC User-to-User specification of ISO/IEC 13818-6 [4] and with the Object Request Broker (ORB) framework as defined by CORBA (OMG Specification [9]). Within the DSM-CC User-to-User (U-U) system environment, a structured group of objects is referred to as a Service Domain. The Service Domain has a Service Gateway which can be seen as the top-level directory of the structured group of objects. As such the Service Gateway provides a context for the graph of service names (i.e. object names) that is published to the Clients. A Service Domain can be located at a Server in an interactive network as well as on a Server in a broadcast Network. In the latter case the objects within the Service Domain are broadcast by means of an object carousel. NOTE: For naming of objects please refer to annex C of the present document. The data and attributes of a single Object within an object carousel are transmitted in a single message. The message format is specified by the object carousel specification and is referred to as the BIOP message format (Broadcast Inter ORB Protocol). BIOP messages are broadcast in a single Module of a DSM-CC Data Carousel (ISO/IEC 13818-6 [4]). One Module may contain one or more BIOP messages. According to the DSM-CC Data Carousel specification each Module is fragmented into one or more Blocks which are carried in a DownloadDataBlock message. Each DownloadDataBlock message is of the same size (except for the last block of the Module which may be of a smaller size) and is transmitted in turn in an MPEG-2 section as specified in (ISO/IEC 13818-6 [4]). The encapsulation rules for DownloadDataBlock messages in MPEG-2 sections are such that Blocks can be acquired directly from the Transport Stream using hardware filters found generally on demultiplexers. Objects within Service Domains are identified using object references. DSM-CC U-U uses the Interoperable Object Reference (IOR) structure as defined by CORBA. The object reference contains all the information that is necessary to retrieve the object from one or more Servers in the network. The structure in the IOR that contains the location information of a single instance of a stored Object is called a profile body. An IOR may contain multiple Profile Bodies to indicate multiple (network) locations of the object. The object carousel specification uses two Profile Bodies. These two Profile Bodies: BIOPProfileBody and LiteOptionsProfileBody, are used to refer to objects that are located either in the same object carousel or in another object carousel, respectively. The first Profile Body is called the Broadcast Inter ORB Protocol (BIOP) Profile Body and is solely used to refer to objects within the same object carousel (i.e. Service Domain). It facilitates the unique identification of the Object using the identifier of the object carousel, the identifier of the Module in which the object is broadcast, and an unique key that identifies the object within the Module. The identifier of the object carousel is linked to a DVB-service via a descriptor in the PMT of the MPEG program. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 24 The second Profile Body is called the Lite Options Profile Body and is used to refer to objects in another Service Domain (either Interactive or Broadcast). It facilitates applications to connect to another Service Domain using a globally unique NSAP address format. For Service Domains in DVB-compliant networks the NSAP address is linked to a particular DVB-service. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.2.2 Supported U-U Objects | The object carousel specification is designed to support a number of the interfaces defined in the Application Portability Interface (API) of DSM-CC U-U (User-to-User). This section provides guidelines regarding the objects and interfaces supported within object carousels (see for interface definitions ISO/IEC 13818-6 [4]): Table 4.2: Objects with supported READER interfaces Object Supported READER Interfaces DSM::Directory Access, Directory DSM::File Base, Access, File DSM::Stream Base, Access, Stream DSM::ServiceGateway Access, ServiceGateway BIOP::StreamEvent Base, Access, Stream, Event It should be noted that the semantics of the API for broadcast networks will differ slightly from the semantics of the API for interactive networks. The cause for this lies in the broadcast nature of the network. A typical example is with the Stream interface where a pause ("now") API call for streams delivered via the broadcast network may freeze the image on screen but not pause the delivery of the (broadcast) stream. DVB Guideline: The present document does not provide any guidelines regarding the precise operation of the DSM-CC U-U interface in Broadcast networks. The DSM-CC interface Access will return attributes (i.e. object properties like read permission and access times) which are set to default values because the broadcast of these attributes is not defined in BIOP ISO/IEC 13818-6 [4] and in ETS 300 802 [3]. DVB Guideline: The present document does not provide any guidelines regarding the broadcasting of Access attributes in object carousel. Figure 4.6 shows the relationships between the U-U Objects using OMT notation [12]. StrEventTap StrStatusTap EventList Name Content BiopProgramTap BiopEsTap ServiceGateway Binding Directory Stream BIOP::StreamEvent 1+ Tap 1+ File IOR Object refers to StrNptTap Figure 4.6: Supported Objects within object carousel ETSI ETSI TR 101 202 V1.2.1 (2003-01) 25 In an object carousel the following information is transmitted for each object: Directory object data: List of Bindings, where each Binding binds a Name to an object reference (IOR). In addition, each Binding may also contain some additional attributes of the bound object to support the fast browsing through directories. In the current object carousel specifications this is only used for the contentSize attribute for file objects. File object data: File content data and the contentSize attribute. Stream object data: A list of identifiers (called Taps) referring to one or more streams in the Broadcast network. Each Tap refers to either an Elementary Stream (BiopEsTap) or to a complete MPEG program (BiopProgramTap). Additionally other identifiers may be present that point to broadcast channels that contain control information for the stream (such as Taps that refer to StreamDescriptors for NPT, status/mode and events). The stream object data also includes the StreamInfo attribute. ServiceGateway object data: Identical to Directory object because ServiceGateway inherits from Directory. Special for the ServiceGateway object is that it contains the Root directory of the Service Domain. StreamEvent object data: Similar to the Stream object data, but extended with the EventList attribute and a list of eventIds. These attributes contain a list of DSM-CC event names and a mapping of those to eventIds. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.2.3 Transmission of objects | The data and attributes of one U-U Object in an object carousel are transmitted in one message. The message format is specified by the Broadcast Inter ORB Protocol (BIOP) and is referred to as the BIOP Generic Object Message format (or BIOP message for short). A BIOP Message consists of a MessageHeader, a MessageSubHeader and a messageBody. The MessageHeader provides information about the version of the BIOP protocol and the length of the BIOP message. The MessageSubHeader contains information about the conveyed Object such as objectType (File, Stream, Directory) and objectKey (the unique identifier within a Module). The messageBody depends on the objectType and contains the actual U-U Object's data. The size of a BIOP message is variable. BIOP messages are broadcast in Modules of Data Carousels (ISO/IEC 13818-6 [4]). A Module is formed by the one or more concatenated BIOP Messages (see figure 4.7) and are thus of variable length. Within the Module each Object is identified by the objectKey. An Object can easily be found by parsing subsequently the objectKey field of the BIOP message and the length of the BIOP message. According to the DSM-CC Data Carousel specification each module is fragmented into one or more Blocks which are carried in a DownloadDataBlock message. Each DownloadDataBlock message is of the same size (except for the last block of the Module which may be of a smaller size) and is transmitted in turn in an MPEG-2 private section as specified in ISO/IEC 13818-6 [4]. The encapsulation rules for DownloadDataBlock messages in MPEG-2 private sections are such that Blocks can be acquired directly from the Transport Stream using hardware filters found generally on demultiplexers. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 26 Download Data Carousel : Modules and Blocks Object Carousel: BIOP messages Obj-1 (Directory) Module-1 Obj-3 (File) Obj-2 (Stream) Block-1 Block-2 Block-3 Block-4 Block-5 Download DataBlock Headers Message Headers and SubHeaders DSM-CC Sections Section-2 Section-1 Section-4 Section-3 Section-5 Section Headers Figure 4.7: Encapsulation and fragmentation of BIOP Messages in Modules, Blocks, and MPEG-2 sections The acquisition of an object from the broadcast network requires the complete acquisition of the module in which the object is contained. This requires knowledge of the delivery parameters of the Module such as module version, module size, block size, timing and broadcast channel. These delivery parameters are transmitted in a DownloadInfoIndication message which has to be acquired from the network before acquiring the module (ISO/IEC 13818-6 [4]). One DownloadInfoIndication message can describe the delivery parameters of multiple modules. The retrieval of an object from the Broadcast network is therefore a two-step process. Within BIOP the object reference of the Service Gateway of a Service Domain is transmitted in a DownloadServerInitiate message (ISO/IEC 13818-6 [4]). This message can be found using information from either the PSI or the PSI and SI. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.2.4 Object References | BIOP uses CORBA's Interoperable Object Reference (see also ISO/IEC 13818-6 [4] and OMG [9]). An object reference contains for each network location one Profile Body. The type of Profile Body depends on the protocols that are necessary to acquire the Object from the Server. For an IOR that refers to an Object within the same broadcast Service Domain (i.e. within the same object carousel), the BIOP Profile Body identifies the location of the BIOP message that conveys the Object data and attributes. The BIOP Profile Body consists therefore of an ObjectLocation component and a ConnBinder component (see figure 4.8). Figure 4.8 illustrates how the object reference (IOR) with BIOP Profile Body can be resolved into the Object that it refers to. The ObjectLocation identifies the object in the U-U object carousel by means of the triple carouselId, moduleId and objectKey. The ConnBinder consists of a sequence of Taps (see clause 4.7.2.5). The Taps identify via the PMT the streams on which the DownloadInfoIndication message is broadcast that contains the Module Delivery Parameters of the object. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 27 ObjectLocation Optional More Taps objectKey Tap carouselId moduleId IOR BIOPProfileBody ConnBinder moduleId module data blockNumber DownloadDataBlock Module Object Object Object Object 1 module delivery params of other modules module delivery param moduleId DownloadInfoIndication Optional More Taps Tap 2 1 2 TapUse = BIOP_OBJECT_USE TapUse = BIOP_DELIVERY_PARA_USE PMT PMT Figure 4.8: How an IOR with BIOP profile body can be resolved into an Object The ConnBinder shall contain at least one Tap that 'points' via the PMT to the DownloadInfoIndication message. The moduleId in the IOR is used to determine the appropriate delivery parameters in the DownloadInfoIndication message. The delivery parameters shall in turn contain at least one Tap that 'points' (also via the PMT) to the DownloadDataBlock messages that convey the Module. Finally the objectKey from the IOR is used to identify the Object message in the Module. Note that both the ConnBinder and the module delivery parameters may contain more than one Tap. Additional Taps may identify alternative streams where the same Module (with possible other delivery parameters) is transmitted. For an IOR that refers to an object in another Service Domain the Lite Options Profile Body is used. The Lite Options Profile Body uses a globally unique NSAP address to identify the Service Domain which may be either Interactive or Broadcast. For Service Domains in DVB-compliant broadcast networks the NSAP address identifies a particular DVB-service as specified in EN 301 192 [1] (see figure 4.9). Figure 4.9 illustrates how the object reference (IOR) with a Lite Options Profile Body can be resolved into the Service Gateway of a broadcast Service Domain. The Profile Body contains a Service Location component that contains in turn the NSAP address. The NSAP address identifies the broadcast Service Domain using the triple transport_stream_id, service_id, and orginal_network_id of the DVB service in which the object carousel is broadcast. Using the PAT and the PMT of the service the IOR of the Service Gateway is found in a DownloadServerInitiate message. This IOR contains in turn an BIOP Profile Body that points to the Service Gateway Object of the broadcast Service Domain. The resolve operation of the BIOP Profile Body is identical as in figure 4.8. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 28 ServiceLocation service_id org_network_id LiteOptions.Pr.Body NSAP Transport_id carousel_id IOR DownloadServerInitiate See previous Figure PMT path_name() PAT ObjectLocation Optional More Taps objectKey Tap carouselId moduleId IOR BIOPProfileBody ConnBinder Figure 4.9: How an IOR with Lite Options Profile Body can be resolved into a Service Gateway |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.2.5 Taps and associations | IORs do not refer to streams directly by means of a PID, because PIDs can be changed by re-multiplexers. DSM-CC has defined therefore Taps (ISO/IEC 13818-6 [4]) which are used in a similar way as component tags in DVB SI. A Tap consists of: id this field is for private use (shall be set to zero if not used) use field indicating the usage of the Tap. association_tag (association tag) field to associate the Tap with a particular (Elementary) Stream. selector optional selector, to select the associated data from the associated (Elementary) Stream. The presence of the selector depends on the use field. The following use values are used within object carousels: 1) BIOP_DELIVERY_PARA_USE: The ConnBinder component of an BIOP Profile Body shall include such Taps to indicate the connections at which the DownloadInfoIndication() messages are broadcast that describe the module delivery parameters of the Module in which the object is conveyed (see figure 4.10). The selector field of such Taps contains a transactionId field and a timeout field. The value of the transactionId field shall be set to the transactionId of the DownloadInfoIndication() message that contains the module delivery parameters. The timeout field shall be set to the time-out period in microseconds to be used to time out the acquisition of the DownloadInfoIndication message. 2) BIOP_OBJECT_USE: Used in the DownloadInfoIndication() messages which convey the module delivery parameters of the Modules to indicate the elementary stream on which the Modules are broadcast. The selector field is empty. 3) BIOP_ES_USE, BIOP_PROGRAM_USE: The Stream object contains such Taps to indicate the stream(s) that are associated with the object. Where a BIOP_ES_USE refers to a single Elementary Stream and BIOP_PROGRAM_USE refers to a complete MPEG-2 Program (DVB Service). The selector field of both Tap types is empty. 4) STR_STATUS_AND_EVENT_USE, STR_EVENT_USE, STR_STATUS_USE, STR_NPT_USE: The Stream object and StreamEvent object may contain these Taps to indicate the various sub-streams that are associated with the object. The selector field of all such Taps is empty. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 29 use Tap id association_tag selector transactionId time-out PMT 1st descriptor loop carousel_id_descr ES loop PID carouselId 2nd descriptor loop association_tag_descr association_tag use selector module delivery params of other modules module delivery param moduleId DownloadInfoIndication Optional More Taps Tap 2 transactionId Figure 4.10: Use of association_tag descriptor to indicate elementary streams (TapUse = BIOP_DELIVERY_PARA_USE). In the course of resolving an object, Clients have to associate the Taps to the connections of the broadcast network. Clients need, therefore, an association table that makes the association between the Taps and the connections of the broadcast network. To support the implementation of U-U object carousels in Broadcast Networks based on MPEG-2 Transport Streams, ISO/IEC 13818-6 [4] defines three descriptors that can be inserted into MPEG-2 PMTs: 1) The carousel_identifier_descriptor labels a PMT with a carousel_id, identifying that all association_tags present in the PMT belong to that U-U object carousel (providing a scope for the association tags (see figure 4.10). 2) The association_tag_descriptor labels an Elementary Stream with an association_tag, associating all Taps containing this tag with this Elementary Stream (see figure 4.10). Like a Tap, an association_tag_descriptor also contains a use field and an optional selector field. Setting this use field to 0x0000, labels the Elementary Stream that a DownloadServerInitiate message (DSI) is transmitted at this stream. This DSI contains the IOR of the ServiceGateway. 3) The deferred_association_tags_descriptor contains a list of association_tags that are associated with (Elementary Streams in) another MPEG-2 program (PMT) or that refer to another program (for use with BIOP_PROGRAM_USE Taps). Figure 4.11 illustrates the use of the deferred_association_tags_descriptor to point to another program. id Tap use association_tag PMT 1st descriptor loop carousel_id_descr ES loop PID carouselId 2nd descriptor loop deferred_assoc_tag_descr association_tag descriptors transport_stream_id program_number PAT PMT 1st descriptor loop ES loop PID 2nd descriptor lp. descriptors descriptors PID 2nd descriptor lp. descriptors audio video org_network_id Figure 4.11: Use of deferred_association_tag descriptor to indicate an MPEG-2 program (TapUse = PROGRAM_USE) ETSI ETSI TR 101 202 V1.2.1 (2003-01) 30 |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.3 BIOP Control Structures | BIOP control and data structures are defined in ISO/IEC 13818-6 [4] using the platform-independent specification language OMG IDL (Interface Definition Language) as defined in OMG [9]. The 'bits-on-the-wire' encoding is defined by the CDR (Common Data Representation, OMG [9]) encoding rules that converts IDL grammar to bits on the wire. BIOP uses the CDR Lite encoding rules (ISO/IEC 13818-6 [4] which uses maximum length numbers in sequences and byte alignment. Consequently, CDR Lite achieve a much more compact packing of data, compared to CDR. NOTE: This also implies that all strings are terminated by a null character and that this character forms part of the string length. (For an example see in table 4.9 the fields objectKind_length and objectKind_data). In this clause the BIOP control structures are shown using an MPEG-2 syntax and guidelines are provided concerning the encoding of the fields. Fields that are affected by the guidelines are shaded. In clause 4.7.4 the BIOP messages are shown using an MPEG-2 syntax. In the case of any differences between the IDL structures defined in ISO/IEC 13818-6 [4] and the structures defined in the following clauses, the defined structures in ISO/IEC 13818-6 [4] will be correct. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.3.1 Interoperable Object Reference (IOR) | DSM-CC uses the Interoperable Object Reference (IOR) format defined by OMG for object references at the Client- Server Inter-operability Interface. Table 4.3 shows the syntax of the IOP::IOR (ISO/IEC 13818-6 [4]). Table 4.3: IOP::IOR syntax Syntax bits Type Value Comment IOP::IOR { type_id_length 32 uimsbf N1 for (i=0; i<N1; i++) { type_id_byte 8 uimsbf + see table 4.4 } if (N1 % 4 β 0) { + CDR alignment rule for (i=0; i<(4-(N1 % 4)); i++) { alignment_gap 8 uimsbf 0xFF } } taggedProfiles_count 32 uimsbf N2 Profile bodies for (n=0; n<N2; n++) { IOP::taggedProfile() { profileId_tag 32 uimsbf + e.g. TAG_BIOP e.g. TAG_LITE_OPTIONS profile_data_length 32 uimsbf N3 for (i=0; i<N3; i++) { profile_data_byte 8 uimsbf e.g. BIOPProfileBody e.g. LiteOptionsProfileBody } } } } The type_id_byte fields of the IOR form a string representing the type of the object. For object identification in OMG [9] mechanisms, string ids are used in the form "<Module>::<Interface>". In order to reduce the size of IORs, DSM-CC defines aliases of 3 characters. The type_ids for Objects used in a DVB object carousels are shown in table 4.4. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 31 Table 4.4: U-U Objects type_id Full type_id alias type_id "DSM::Directory" "dir" "DSM::File" "fil" "DSM::Stream" "str" "DSM::ServiceGateway" "srg" "BIOP::StreamEvent" "ste" DVB Guideline: Only the alias type_id fields shall be used with DVB compliant systems. This implies that no alignment stuffing bytes have to be inserted by the Server when using these aliases. An IOR that refers to an object transmitted in the same U-U object carousel contains a BIOP Profile Body in the taggedProfileList. ISO/IEC 13818-6 [4] allows an IOR to contain more than one profile body. DVB Guideline: DVB compliant receivers shall be able to process at least the first of these profile bodies, while the other profile bodies may be ignored. There shall be at least 1 taggedProfile included in an IOR. For objects carried in a broadcast object carousel, the first taggedProfile shall be either a TAG_BIOP profile or a TAG_LITE_OPTIONS. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.3.2 BIOP Profile Body | The BIOP Profile Body has a LiteComponentProfile structure which follows the MultipleComponentProfile structure. Table 4.5 shows the syntax of the BIOP Profile Body including the mandatory ObjectLocation component and ConnBinder Component. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 32 Table 4.5: BIOP Profile Body syntax Syntax bits Type Value Comment BIOPProfileBody { profileId_tag 32 uimsbf 0x49534F06 TAG_BIOP (BIOP Profile Body) profile_data_length 32 uimsbf * profile_data_byte_order 8 uimsbf 0x00 big endian byte order liteComponents_count 8 uimsbf N1 BIOP::ObjectLocation { componentId_tag 32 uimsbf 0x49534F50 TAG_ObjectLocation component_data_length 8 uimsbf * carouselId 32 uimsbf + moduleId 16 uimsbf + version.major 8 uimsbf 0x01 BIOP protocol major version 1 version.minor 8 uimsbf 0x00 BIOP protocol minor version 0 objectKey_length 8 uimsbf N2 for (k=0; k<N2; k++) { objectKey_data_byte 8 uimsbf + } } DSM::ConnBinder { componentId_tag 32 uimsbf 0x49534F40 TAG_ConnBinder component_data_length 8 uimsbf * taps_count 8 uimsbf N3 BIOP::Tap { id 16 uimsbf 0x0000 user private use 16 uimsbf 0x0016 BIOP_DELIVERY_PARA_USE association_tag 16 uimsbf + selector_length 8 uimsbf 0x0A selector_type 16 uimsbf 0x01 transactionId 32 uimsbf * timeout 32 uimsbf * } for (m=0; m<N3-1; m++) { BIOP::Tap { id 16 uimsbf 0x0000 user private use 16 uimsbf 0x0016 BIOP_DELIVERY_PARA_USE association_tag 16 uimsbf + selector_length 8 uimsbf N4 for (i=0; i<N4; i++) { selector_data_byte 8 uimsbf } } } } for (n=0;n<N5;n++) { N5=N1-2 BIOP::LiteComponent { componentId_tag 32 uimsbf + component_data_length 8 uimsbf N6 for (i=0; i<N6; i++) { component_data_byte 8 uimsbf } } } } DVB Guideline: The byte_order field shall have the value of 0x00 meaning that following data is encoded using big-endian byte ordering. The carouselId field provides a context for the moduleId field. It uniquely identifies the carousel within the Broadcast Network and allows the distributed implementation of the carousel. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 33 DVB Guideline: The BIOP Profile Body shall only be used to refer to Objects within the same carousel. I.e. the value of the carouselId is equal to the carouselId of the object carousel in which the IOR is transmitted. To refer to Objects in another carousel use the Lite Options Profile Body. DVB Guideline: The list of LiteOptionComponents shall contain exactly 1 BiopObjectLocation and exactly 1 DsmConnectionBinder as the first two components in that order. The moduleId identifies the module in which the object is conveyed within the carousel. The objectKey identifies the object within the module in which it is broadcast. This field is a series of bytes that is supplied by the server and which is only meaningful to the server. DVB Guideline: The value of the objectKey length field shall be less than or equal to 0x04. Multiple Taps may share the same association tag, enabling one Elementary Stream to be used for more than one purpose. Table 4.6 shows the defined Tap uses. Table 4.6: Allowed Tap use definitions for Taps in a BIOP Profile Body TapUse field Value Broadcast on PID BIOP_DELIVERY_PARA_USE 0x16 Module delivery parameters BIOP_OBJECT_USE 0x17 BIOP objects in Modules DVB Guideline: If the BIOP_DELIVERY_PARA_USE tap is present in the ConnBinder component then it will be the first tap in the ConnBinder. DVB Guideline: DVB compliant receivers may skip over the BIOP_OBJECT_USE taps in BIOP Profile Bodies in IORs. DVB Guideline: The id field shall be set to zero if not used. The semantics of the fields of a Tap with a TapUse value of BIOP_DELIVERY_PARA_USE are described below: β’ The use field indicates the use of the Tap. The value of this field shall be BIOP_DELIVERY_PARA_USE. β’ The association_tag identifies the broadcast channel (i.e. the Elementary Stream) on which the DownloadInfoIndication() message is broadcast. The selector field shall contain a selectorType of value MESSAGE (=0x0001) and the transactionId and timeout fields. The value of the transactionId field shall be set to the transactionId of the DownloadInfoIndication() message that contains the module delivery parameters. The timeout field shall indicate the time-out period in microseconds to be used to time out the acquisition of the DownloadInfoIndication() message. The semantics of the fields of a Tap with a TapUse value of BIOP_OBJECT_USE are described below: β’ The use field indicates the use of the Tap. The value of this field shall be BIOP_OBJECT_USE. β’ The association_tag identifies the broadcast channel (i.e. Elementary Stream) on which the Modules are broadcast. β’ The selector field shall be of 0 length. NOTE: Taps with a TapUse value of BIOP_OBJECT_USE should, however, in DVB compliant systems be used only in the DownloadInfoIndication messages and not in the IORs. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.3.3 Lite Options Profile Body | To refer to an Object in another Service Domain, an IOR is present that contains a ServiceLocation component in an Lite Options Profile Body. When a DSM-CC U-U API user attempts to resolve a Name (Directory::resolve, see ISO/IEC 13818-6 [4], clause 5), that results in the encounter of such an IOR, a SERVICE_XFR exception is raised. A SERVICE_XFR exception carries the ServiceLocation structure found in the Lite Options Profile Body of the IOR. The API user may use the serviceDomain from the ServiceLocation structure for a subsequent attach to the new ServiceGateway. The optional pathName contains the path within that ServiceGateway to find the Object. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 34 A Lite Options Profile Body has a LiteComponentProfile structure which follows the MultipleComponentProfile structure. Table 4.7 shows the syntax of an Options Profile Body, that conveys a ServiceLocation component. Table 4.7: Syntax of Options Profile Body with ServiceLocation component Syntax bits Type Value Comment LiteOptionsProfileBody { profileId_tag 32 uimsbf 0x49534F05 TAG_LITE_OPTIONS (Lite Options Profile Body) profile_data_length 32 uimsbf * profile_data_byte_order 8 uimsbf 0x00 big endian byte order component_count 8 uimsbf N1 DSM::ServiceLocation { componentId_tag 32 uimsbf 0x49534F46 TAG_ServiceLocation component_data_length 32 uimsbf * serviceDomain_length 8 uimsbf 0x14 Length of carousel NSAP address serviceDomain_data() 160 uimsbf + DVBcarouselNSAPaddress (see table 4.8) CosNaming::Name() { pathName nameComponents_count 32 uimsbf N2 for (i=0; i<N2; i++) { id_length 32 uimsbf N3 NameComponent id for (j=0; j<N3 j++) { id_data_byte 8 uimsbf + } kind_length 32 uimsbf N4 NameComponent kind for (j=0; j<N4 j++) { kind_data_byte 8 uimsbf + as type_id (see table 4.4) } } initialContext_length 32 uimsbf N5 for (n=0; n<N5 n++) { InitialContext_data_byte 8 uimsbf } } } for (n=0;n<N6;n++) { N6=N1-1 BIOP::LiteOptionComponent{ componentId_tag 32 uimsbf + component_data_length 8 uimsbf N7 for (i=0; i<N7; i++) { component_data_byte 8 uimsbf } } } } DVB Guideline: The ServiceLocation component shall be the first component in the profile body. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.3.4 Carousel NSAP address | Each instance of a U-U object carousel represents a Service Domain. Each Service Domain has a globally unique identifier that identifies a particular instance of a carousel, called the Carousel NSAP address (Network Service Access Point). ETSI ETSI TR 101 202 V1.2.1 (2003-01) 35 Table 4.8: DVB Carousel NSAP Address syntax Syntax bits Type Value Comment DVBcarouselNSAPaddress() AFI 8 uimsbf 0x00 NSAP for private use Type 8 uimsbf 0x00 Object carousel NSAP Address. carouselId 32 uimsbf + specifierType 8 uimsbf 0x01 IEEE OUI specifierData { IEEE OUI } 24 uimsbf 0x<DVB> Constant for DVB OUI dvb_service_location () { transport_stream_id 16 uimsbf + original_network_id 16 uimsbf + service_id 16 uimsbf + (= MPEG-2 program_number) reserved 32 bslbf 0xFFFFFFFF } } The semantics of the AFI, type, carouselId, specifierData, transport_stream_id, original_network_id, and service_id, and fields are as defined in EN 301 192 [1]. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.4 BIOP Messages | |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.4.1 Directory | The BIOP::DirectoryMessageBody structure consists of a loop of Bindings. A binding correlates an object name (i.e. bindingName) to an IOR and provides additional information about the object. The IOR must include the BIOP Profile Body when the referenced object belongs to the Carousel. Strings shall be terminated by the character "0x0". The BIOP Directory message is an instantiation of the generic object message format. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 36 Table 4.9: BIOP::DirectoryMessage syntax Syntax bits Type Value Comment BIOP::DirectoryMessage() { magic 4x8 uimsbf 0x42494F50 "BIOP" biop_version.major 8 uimsbf 0x01 BIOP major version 1 biop_version.minor 8 uimsbf 0x00 BIOP minor version 0 byte_order 8 uimsbf 0x00 big endian byte ordering message_type 8 uimsbf 0x00 message_size 32 uimsbf * objectKey_length 8 uimsbf N1 for (i=0; i<N1; i++) { objectKey_data_byte 8 uimsbf + } objectKind_length 32 uimsbf 0x00000004 objectKind_data 4x8 uimsbf 0x64697200 "dir" type_id alias objectInfo_length 16 uimsbf N2 objectInfo for (i=0; i<N2; i++) { objectInfo_data_byte 8 uimsbf + } serviceContextList_count 8 uimsbf N3 serviceContextList for (i=0; i<N3; i++) { context_id 32 uimsbf context_data_length 16 uimsbf N9 for (j=0; j<N9; j++) { context_data_byte 8 uimsbf + } } messageBody_length 32 uimsbf * bindings_count 16 uimsbf N4 for (i=0; i<N4; i++) { Binding BIOP::Name(){ nameComponents_count 8 uimsbf N5 for (i=0; i<N5; i++) { id_length 8 uimsbf N6 NameComponent id for (j=0; j<N6; j++) { id_data_byte 8 uimsbf + } kind_length 8 uimsbf N7 NameComponent kind for (j=0; j<N7; j++) { kind_data_byte 8 uimsbf + as type_id (see table 4.4) } } } bindingType 8 uimsbf + 0x01 for nobject 0x02 for ncontext IOP::IOR() + objectRef (see table 4.3) objectInfo_length 16 uimsbf N8 for (j=0; j<N8; j++) { objectInfo_data_byte 8 uimsbf + } } } The semantics of the fields of the BIOP::DirectoryMessageBody are defined below: The byte_order field indicates the byte ordering used for the following subsequent elements of the message (including message_size). A value of FALSE (0) indicates big-endian byte ordering, and TRUE (1) indicates little endian ordering. DVB Guideline: The byte_order field shall have the value of 0x00 meaning that following data is encoded using big-endian byte ordering. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 37 The objectKey field identifies the object that is conveyed in this message. It is identical to the objectKey that is present in the BIOP::ObjectLocation component of the IOR of the object. The value of the objectKey is only meaningful to the Broadcast Server and is not interpreted by the Client. It will however be used by the Client for a byte by byte comparison to compare this objectKey with the objectKey from an IOR. DVB Guideline: The value of the objectKey length field shall be less than or equal to 0x04. The objectKind field identifies the kind of the object that is conveyed in this message. It is identical to the type_id string that is present in the IOR of the object (see clause 4.7.3.1 and table 4.4). The value of the objectKind defines the syntax and semantics of the objectInfo field and the messageBody field. DVB Guideline: The objectKind of a Directory message shall be "dir". The objectInfo field contains some or all of the attributes of this object. The syntax and semantics of this field are dependent of the value of the objectKind field. The serviceContextList may be used to pass user private data related to the object interfaces. Its use will not be defined by this specification. DVB Guideline: DVB compliant receivers shall be able to skip over the ServiceContextList field. The bindingName field (i.e. id and kind) contains the path specification of the object (as defined by CosNaming). DVB Guideline: The BIOP::Name the name shall contain exactly one NameComponent thus nameComponents_count shall be set to 1. The bindingType field indicates the type of the object binding. Binding can either be of type 'ncontext' when the name is bound to a Directory or ServiceGateway object or 'nobject' when the name is bound to an object other than Directory or ServiceGateway. BindingType 'composite' is not supported for U-U object carousels. The objectRef field contains the IOR of the object. The objectInfo field may contain some of the attributes of the bound object as well as user private information about the object. If attributes of the bound object are carried in this field they shall be the first structures that are encapsulated in this field. DVB Guideline: DVB compliant receivers shall be able to skip over information in the objectInfo field. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 38 |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.4.2 File | The FileMessageBody contains the file data as an octet stream. Table 4.10: BIOP::FileMessage syntax Syntax bits Type Value Comment BIOP::FileMessage() { Magic 4x8 uimsbf 0x42494F50 "BIOP" biop_version.major 8 uimsbf 0x01 BIOP major version 1 biop_version.minor 8 uimsbf 0x00 BIOP minor version 0 byte_order 8 uimsbf 0x00 big endian byte ordering message_type 8 uimsbf 0x00 message_size 32 uimsbf * objectKey_length 8 uimsbf N1 for (i=0; i<N1; i++) { objectKey_data_byte 8 uimsbf + } objectKind_length 32 uimsbf 0x00000004 objectKind_data 4x8 uimsbf 0x66696C00 "fil" type_id alias objectInfo_length 16 uimsbf N2 DSM::File::ContentSize 64 uimsbf + objectInfo for (i=0; i<N2-8; i++) { objectInfo_data_byte 8 uimsbf + } serviceContextList_count 8 uimsbf N3 serviceContextList for (i=0; i<N3; i++) { context_id 32 uimsbf context_data_length 16 uimsbf N9 for (j=0; j<N9; j++) { context_data_byte 8 uimsbf + } } messageBody_length 32 uimsbf * content_length 32 uimsbf N4 for (i=0; i<N4; i++) { content_data_byte 8 uimsbf + actual file content } } The semantics of the fields of the BIOP::File message are identical as for the BIOP::Directory message except the following rules: The objectKind field identifies the kind of the object that is conveyed in this message. It is identical to the type_id string that is present in the IOR of the object (see clause 4.7.3.1 and table 4.4). The value of the objectKind defines the syntax and semantics of the objectInfo field and the messageBody field. DVB Guideline: The objectKind of a File message shall be "fil". ETSI ETSI TR 101 202 V1.2.1 (2003-01) 39 |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.4.3 Stream | DVB Guideline: The objectKind of a Stream message shall be "str". The BIOP::StreamMessageBody consists a sequence of Taps that are associated with the stream object. Table 4.11: BIOP::StreamMessage syntax Syntax bits Type Value Comment BIOP::StreamMessage() { magic 4x8 uimsbf 0x42494F50 "BIOP" biop_version.major 8 uimsbf 0x01 BIOP major version 1 biop_version.minor 8 uimsbf 0x00 BIOP minor version 0 byte_order 8 uimsbf 0x00 big endian byte ordering message_type 8 uimsbf 0x00 message_size 32 uimsbf * objectKey_length 8 uimsbf N1 for (i=0; i<N1; i++) { objectKey_data_byte 8 uimsbf + } objectKind_length 32 uimsbf 0x00000004 objectKind_data 32 uimsbf 0x73747200 "str" type_id alias objectInfo_length 16 uimsbf N6 DSM::Stream::Info_T { objectInfo aDescription_length 8 uimsbf N2 aDescription for (i=0; i<N2; i++) { aDescription_bytes 8 uimsbf + } duration.aSeconds 32 simsbf + AppNPT seconds duration.aMicroSeconds 16 uimsbf + AppNPT micro seconds audio 8 uimsbf + video 8 uimsbf + data 8 uimsbf + } for (i=0; i=N6-(N2+10); i++) { objectInfo_byte 8 uimsbf + } serviceContextList_count 8 uimsbf N3 serviceContextList for (i=0; i<N3; i++) { context_id 32 uimsbf context_data_length 16 uimsbf N9 for (j=0; j<N9; j++) { context_data_byte 8 uimsbf + } } messageBody_length 32 uimsbf * taps_count 8 uimsbf N4 for (i=0; i<N4; i++) { id 16 uimsbf 0x0000 undefined use 16 uimsbf + (see table 4.12) association_tag 16 uimsbf + selector_length 8 uimsbf 0x00 no selector } } The stream field contains one or more Taps that are associated with this stream object. Regarding the content of the stream either one or more Taps are present with a TapUse value of BIOP_ES_USE or one Tap is present with a TapUse value of BIOP_PROGRAM_USE. In the first case, the stream consists of a number of elementary streams, each elementary stream is identified by a BIOP_ES_USE Tap. In the second case the stream consists of an MPEG-2 Program, identified by a BIOP_PROGRAM_USE Tap. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 40 The semantics of the fields of a Tap that points to an elementary stream are described below: β’ The use field indicates the use of the Tap. The value of this field shall be BIOP_ES_USE. β’ The association_tag identifies the broadcast Elementary Stream. β’ The selector field shall be empty. The semantics of the fields of a Tap that points to an MPEG-2 Program are described below: β’ The use field indicates the use of the Tap. The value of this field shall be BIOP_PROGRAM_USE. β’ The association_tag identifies the MPEG-2 Program Map Table (PMT) that describes the broadcast program. The association_tag value will correspond with an association_tag value in a deferred_association_tags_descriptor, that points to the PMT (see clause 4.7.7.4). β’ The selector field shall be empty. Note that the Taps in a stream may also refer to NPT (Normal Play Time), status and event elementary streams. Table 4.12: Allowed Tap use definitions for Taps in a BIOP::StreamMessage TapUse field Value Broadcast on PID STR_NPT_USE 0x000B Stream NPT Descriptors STR_STATUS_AND_EVENT_USE 0x000C Both Stream Mode and Stream Event Descriptors STR_EVENT_USE 0x000D Stream Event Descriptors STR_STATUS_USE 0x000E Stream Mode Descriptors BIOP_ES_USE 0x0018 Elementary Stream (Video/Audio) BIOP_PROGRAM_USE 0x0019 Program (DVB Service) Reference |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.4.4 Service Gateway | The syntax and semantics of the Service Gateway message are identical to the syntax and semantics of the BIOP::Directory message except the following: DVB Guideline: The objectKind of a ServiceGateway message shall be "srg". ETSI ETSI TR 101 202 V1.2.1 (2003-01) 41 |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.4.5 StreamEvent | Table 4.13: BIOP::StreamEventMessage syntax Syntax bits Type Value Comment BIOP::StreamEventMessage() { magic 4x8 uimsbf 0x42494F50 "BIOP" version.major 8 uimsbf 0x01 BIOP major version 1 version.minor 8 uimsbf 0x00 BIOP minor version 0 byte_order 8 uimsbf 0x00 big endian byte ordering message_type 8 uimsbf * message_size 32 uimsbf * objectKey_length 8 uimsbf N1 for (i=0; i<N1; i++) { objectKey_data_byte 8 uimsbf + } objectKind_length 32 uimsbf 0x00000004 objectKind_data 4x8 uimsbf 0x73746500 "ste" type_id alias objectInfo_length 16 uimsbf N6 DSM::Stream::Info_T { aDescription_length 8 uimsbf N2 aDescription for (i=0; i<N2; i++) { aDescription_bytes 8 uimsbf + see BIOP::StreamMessage() } duration.aSeconds 32 simsbf + see BIOP::StreamMessage() duration.aMicroSeconds 16 uimsbf + see BIOP::StreamMessage() audio 8 uimsbf + see BIOP::StreamMessage() video 8 uimsbf + see BIOP::StreamMessage() data 8 uimsbf + see BIOP::StreamMessage() } DSM::Event::EventList_T { eventNames_count 16 uimsbf N3 for (i=0; i<N3; i++) { eventName_length 8 uimsbf N4 for (j=0; j<N4; j++) { eventName_data_byte 8 uimsbf + (including zero terminator) } } } for (i=0; i=N6-(N2+10)- (2+N3+sum(N4)); i++) { 8 uimsbf + objectInfo_byte } serviceContextList_count 8 uimsbf 0x00 Empty serviceContextList for (i=0; i<N3; i++) { context_id 32 uimsbf context_data_length 16 uimsbf N9 for (j=0; j<N9; j++) { context_data_byte 8 uimsbf + } } messageBody_length 32 uimsbf * taps_count 8 uimsbf N5 for (i=0; i<N5; i++) { id 16 uimsbf 0x0000 undefined use 16 uimsbf + (see table 4.12) association_tag 16 uimsbf + selector_length 8 uimsbf 0x00 no selector } eventIds_count 8 uimsbf N3 (= eventNames_count) for (i=0; i<N3; i++) { eventId 16 uimsbf + } } ETSI ETSI TR 101 202 V1.2.1 (2003-01) 42 DVB Guideline: The objectKind of a StreamEvent message shall be "ste". The eventIdList contains the eventIds that are correlated to the event names published in the EvenList_T attribute. The sequence count of the eventIds shall be equal to the sequence count of the EventNames. NOTE: DSM-CC events do not correspond to DVB-SI events. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.5 Download Data Carousel Messages | |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.5.1 DownloadInfoIndication | The delivery parameters of the module in the broadcast network are conveyed in a DownloadInfoIndication() message (ISO/IEC 13818-6 [4]). One DownloadInfoIndication() message can convey the module delivery parameters of multiple Modules of the same U-U object carousel. The following semantics apply to the fields of the DownloadInfoIndication() message: The transactionId field shall have the same value as the transactionId value encapsulated in the selector of the BIOP_DELIVERY_PARA_USE Taps of the IORs of the objects that are carried in Modules described in this message. DVB Guideline: If any field of the DownloadInfoIndication message changes, its transaction_id shall be incremented by a positive integer value to a new unique value. The downloadId field shall have the same value as the downloadId field of the DownloadDataBlock() messages which carry the Blocks of the Modules described in this message. Consequently, the value of this field shall be equal to the carouselId of the U-U object carousel. The blockSize field contains the block size of all the DownloadDataBlock() messages which convey the Blocks of the Modules described in this message. The windowSize, ackPeriod, tCDownloadWindow, and tCDownloadScenario fields are not used and are set to zero. The compatibilityDescriptor() field is not used and has a zero length. The moduleId, moduleSize, and moduleVersion fields semantics are in ISO/IEC 13818-6 [4], clause 7.3.2. The moduleInfoLength field defines the length in bytes of the moduleInfo field for the described module. The moduleInfoBytes field shall contain the BIOP::ModuleInfo structure. The BIOP::ModuleInfo structure provides additional delivery parameters and the Taps that are used to broadcast the Modules in the network. The syntax and semantics of the BIOP::ModuleInfo structure are shown in table 4.14. Table 4.14: BiOP:: ModuleinfoMessage syntax Syntax bits Type Value Comment BIOP::ModuleInfo() { ModuleTimeOut 32 uimsbf + BlockTimeOut 32 uimsbf + MinBlockTime 32 uimsbf + taps_count 8 uimsbf N1 for (j=0; j<N1; j++) { Id 16 uimsbf 0x0000 user private Use 16 uimsbf 0x0017 BIOP_OBJECT_USE association_tag 16 uimsbf + selector_length 8 uimsbf 0x00 } UserInfoLength 8 uimsbf N2 for (j=0; j<N2; j++) { userInfo_data_byte 8 uimsbf + (including zero terminator) } } ETSI ETSI TR 101 202 V1.2.1 (2003-01) 43 The moduleTimeOut field gives the time out value in microseconds that may be used to time out the acquisition of all Blocks of the Module. The blockTimeOut field gives the time out value in microseconds that may be used to time out the reception of the next Block after a Block has been acquired. The minBlockTime field indicates the minimum time period that exists between the delivery of two subsequent Blocks of the described Module. Clients may use this value to adjust their acquisition procedures for optimization purposes. The Taps field of BIOP::ModuleInfo shall contain at least one Tap with the TapUse value of BIOP_OBJECT_USE. This Tap shall point to the network connection on which the Modules are broadcast. The semantics of the fields of this Tap are described in clause 4.7.2.5. The userInfo field of BIOP::ModuleInfo shall be structured as a loop of descriptors which enables the use of Module descriptors as defined in DVB Data Carousels. DVB Guideline: The receiver shall support especially the compressed_module_descriptor (tag 0x09) used to signal that the module is transmitted in compressed form. The use of the privateDataLength and privateDataByte fields is not defined by this specification. DVB Guideline: DVB compliant receivers shall be able to skip over the private data field. |
8772ed7b648c8fdde57091f4305eefdf | 101 202 | 4.7.5.2 DownloadServerInitate | The IOR of the Service Gateway is broadcast by means of DownloadServerInitiate() messages. The following semantics apply on the fields of the DownloadServerInitiate() message: The serverId field shall be set to 20 bytes with the value 0xFF. The Carousel Specifier is defined below. The compatibilityDescriptor() field is not used and has a zero length. The privateDataLength field of the DownloadServerInitiate() message defines the length in bytes of the privateDataByte fields that follow this field. The data in the privateDataByte field of the DownloadServerInitiate() message shall contain the BIOP::ServiceGatewayInfo structure. The syntax and semantics of the BIOP::ServiceGatewayInfo structure are defined in table 4.15: Table 4.15: ServiceGatewayInfo() syntax Syntax bits Type Value Comment ServiceGatewayInfo () { IOP::IOR() + (see table 4.3) downloadTaps_count 8 uimsbf N1 software download Taps for (i=0; i<N1; i++) { Tap() 8 uimsbf + } serviceContextList_count 8 uimsbf N2 serviceContextList for (i=0; i<N2; i++) { context_id 32 uimsbf context_data_length 16 uimsbf N9 for (j=0; j<N9; j++) { context_data_byte 8 uimsbf + } } userInfoLength 16 uimsbf N3 user info for (i=0; i<N3; i++) { userInfo_data_byte 8 uimsbf + } } The objectRef field contains the IOR of the ServiceGateway. ETSI ETSI TR 101 202 V1.2.1 (2003-01) 44 The semantics of the Taps field and serviceContextList is not defined in the present document. The user info field shall be structured as a descriptor loop. The descriptors in this loop shall be either descriptors as defined in the DVB Data Broadcasting Specification or private descriptors. |
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