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1af665171ad5782d3c09f2faccdce1eb | 101 956 | 2 References | For the purposes of this Technical Report (TR) the following references apply: [1] E. Kaplan, "Understanding GPS, Principals and Applications", Artech House Publishers, 1996. [2] J.K. Holmes, "Coherent Spread Spectrum Systems", New York, NY. Wiley Interscience, 1982. [3] ITU-R Recommendation SA.363-5: "Space operation ... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 3 Definitions and abbreviations | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 3.1 Definitions | For the purposes of the present document, the following terms and definitions apply: Processing Gain: gain processing indicates the performance of the spreading of a jammer NOTE 1: For PSK systems (power Psignal) and a particular interfere (power Pjammer), we define the processing gain as: jammer signal on implentati b... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 3.2 Abbreviations | For the purposes of the present document, the following abbreviations apply: ACU Antenna Control Unit (in TCR station) AGC Automatic Gain Control AMF Apogee Manoeuvre Firing BB Base-Band processor (in TCR station) BER Bit Error Rate BSS Broadcast Satellite Service CDMA Code Division Multiple Access CEC Collocation Equi... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4 Operational Scenario | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.0 General considerations | The following phases/scenarios which are foreseen to be supported by the TCR standard are defined: • Phase 1: LEOP 1st Phase (perigee) - acquisition - tracking • Phase 2: LEOP 2nd Phase (apogee) - acquisition - tracking • Phase 3: LEOP drift - acquisition - tracking • Phase 4: On-Station - acquisition - tracking ETSI E... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.1 Phase 1: LEOP 1st Phase (perigee) | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.1.1 Phase 1: LEOP 1st Phase (perigee) | frequency RF compatibility power Doppler Jamming due to COM Jamming due to Standard TCR Jamming due to N co-located satellites Power at TC receiver input kDoppler = 2,2 × 10-5 (realistic case, for anomaly higher than 40°) rateDoppler = 1,66 × 10-6 Hz Yes, from other satellites N/A N/A High (due to small S/L-station dis... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.1.2 Downlink: acquisition and tracking | frequency RF compatibility power Doppler Jamming due to COM Jamming due to Standard TCR Jamming due to N co-located satellites C/N0 at ground receiver input Worst case Doppler: Same as uplink Yes, from other satellites N/A N/A High (due to small S/L-station distance) |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.2 Phase 2: LEOP 2nd Phase (apogee) | For this phase, a dedicated station for the satellite is considered. No benefit due to the orbit inclination is expected, as apogee and orbit node are coincident. |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.2.1 Uplink: acquisition and tracking | frequency RF compatibility power Doppler Jamming due to COM Jamming due to Standard TCR Jamming due to N co-located satellites Power at TC receiver input Very few Doppler kDoppler = 6,9 × 10-7 rateDoppler = 5,9 × 10-10 Hz Yes, from other satellites applicable N/A Low (due to high S/L-station distance) ETSI ETSI TR 101 ... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.2.2 Downlink: acquisition and tracking | frequency RF compatibility power Doppler Jamming due to COM Jamming due to Standard TCR Jamming due to N co-located satellites C/N0 at ground receiver input Same as uplink Yes, from other satellites applicable N/A Low (due to high S/L-station distance) |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.3 Phase 3: LEOP drift | The main difference between this phase and phase 2 is the orbit. In phase 2 (apogee phase of the LEOP), the orbit is elliptical, for phase 3, the orbit is circular. So this phase is very similar to phase 2, except concerning slight Doppler variation. |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.3.1 Uplink: acquisition and tracking | frequency RF compatibility power Doppler Jamming due to COM Jamming due to Standard TCR Jamming due to N co-located satellites Power at TC receiver input Very few Doppler kDoppler = 1,3 × 10-8 rateDoppler = 0 Yes, from other satellites applicable N/A Low (due to high S/L-station distance) |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.3.2 Downlink: acquisition and tracking | frequency RF compatibility power Doppler Jamming due to COM Jamming due to Standard TCR Jamming due to N co-located satellites C/N0 at ground receiver input Same as uplink Yes, from other satellites applicable N/A Low (due to high S/L- station distance) |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.4 Phase 4: On station phase | It is considered that all the stations controlling collocated satellites from a same system, will have the same geographical location. |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.4.1 Uplink: acquisition and tracking | frequency RF compatibility power Doppler Jamming due to COM Jamming due to Standard TCR Jamming due to N co-located satellites Power at TC receiver input Very few Doppler kDoppler = 1 × 10-8 rateDoppler = 0 Yes, Self-interference applicable applicable Nominal (note) NOTE: During acquisition phase, it can be accepted fo... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.4.2 Downlink: acquisition and tracking | frequency RF compatibility power Doppler Jamming due to COM Jamming due to Standard TCR Jamming due to N co-located satellites C/N0 at ground receiver input Same as uplink Yes, Self-interference applicable applicable Nominal |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.5 Phase 5: 1 satellite in emergency | The case of two or more satellites in non-nominal on-station phase is not considered. Same remark as in clause 4.4 for the ground station configuration. |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.5.1 Uplink: acquisition and tracking | It shall be tolerable to allow TDMA (no simultaneous uplink signal in the TCR bandwidth). |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.5.2 Downlink: acquisition and tracking | It shall be tolerable to allow TDMA (no simultaneous downlink signal in the TCR bandwidth). |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.6 Phase 6: De-orbitation phase | One ground station is dedicated to the satellite in de-orbitation phase. |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.6.1 Uplink: acquisition and tracking | frequency RF compatibility power Doppler Jamming due to COM Jamming due to Standard TCR Jamming due to N co-located satellites Power at TC receiver input kDoppler = 1,3 × 10-8 rateDoppler = 0 rateDoppler = 0 N/A applicable applicable Nominal (note) NOTE: During acquisition phase, it can be accepted for a short time to ... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 4.6.2 Downlink: acquisition and tracking | frequency RF compatibility power Doppler Jamming due to COM Jamming due to Standard TCR Jamming due to N co-located satellites C/N0 at ground receiver input Same as uplink N/A applicable N/A Nominal ETSI ETSI TR 101 956 V1.1.1 (2001-09) 12 |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5 Analysis | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.1 Ranging trade-off | This analysis compares different ranging techniques: • Ranging method using a PN pattern and built on spread-spectrum techniques. • Ranging method using tones (unmodulated sub-carrier on a PM/FM carrier). In clause 5.1.3, the ESA MPTS is presented separately, because it is a "compound" method: although it uses a PN pat... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.1.1 Ranging with PN code | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.1.1.1 Introduction | Ranging determination is performed by comparing transmitted code phase and received code phase. This comparison is performed by ground equipment. From several techniques which can be used to retrieve code phase difference two are assessed: • DS/SS with on-board processing; • Transparent DS/SS (in communication channel)... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.1.1.2 PN code (DS/SS) with on-board processing | Presentation Figure 1 shows the ground and space segment configuration for ranging assuming a spread spectrum TCR transponder. A ranging PN sequence is generated at the TCR ground terminal, modulated onto a carrier and transmitted to the spacecraft. At the spacecraft, the signal and its ranging sequence are tracked by ... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.1.1.3 Transparent DS/SS (in communication channel) | Presentation Figure 2 shows the ground and space segment configuration for ranging assuming no need for spread spectrum TCR transponder. The ranging signal passes through satellite communication transponders in a transparent way. A ranging PN sequence is generated at the TCR ground terminal, modulated onto a carrier an... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.1.2 Ranging with tones | Presentation Ranging with tones is the conventional ranging method used for geo-stationary satellites. Two standards exist. They are based on the same principle: • ESA-100K standard: (PM on uplink and PM on downlink, frequency of major tone at 100 kHz). • TELESAT-27K standard: (FM on uplink and PM on downlink, frequenc... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.1.3 ESA MPTS standard | Presentation The MPTS is an ESA standard which uses ranging tones technique to issue the ranging measurement (see clause 5.1.2). The main difference is on minor tone management. The MPTS uses a code sequence over the minor tone to set distance ambiguity. The MPTS standard is scalable: • The major tone frequency is sett... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.1.5 Pros and cons of each RG solution | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.1.5.1 Ranging with code | This method gives the best results in terms of accuracy and meets operators' requirements. Transparent: • The advantage of the transparent method is that the communication channel can be used (independent of TCR band, no need for a dedicated bandwidth). • Moreover, for the transparent method, signal processing is fully... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.1.5.2 Ranging with tones | The main advantage of this method is that it is a well-known method which proves to be accurate enough to control geostationary satellites even if it does not meet operators' requirements for accuracy needs (see annex B) (it is not foreseen in the base-line to set the major tone frequency above 100 KHz). But its main d... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.1.5.3 ESA MPTS standard | The ESA MPTS ranging seems to have few advantages over ranging tone standards; it does however allow Ranging and Telecommand to be performed simultaneously, and can be applied to all types of satellite mission (from LEO to Deep Space). However, for GEO missions of commercial communications satellites, this functionalit... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.1.5.4 Hybrid RG system | These solutions avoid the use of SS CDMA on the downlink, while keeping SS CDMA on the uplink. This particularity allows: • No update of the ground TCR station receive section (Standard modulation receiver already exists); • No update of all the COM stations using TM signal as a beacon for the tracking. But this soluti... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.2 Power Control | Power balance between multiple users shall be assumed by the system. It has impact on ground equipment for transmission of TC signal and it has impact on board equipment if TM signal uses SS/DS techniques. |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.2.1 Ground equipment | The parameter to be controlled on-station is the EIRP for TC signal. The value of the EIRP transmitted to the satellite shall be controlled with 1 dB accuracy (TBC: value directly given by capacity analysis calculation where 1 dB is the worst case for power imbalance). The control of transmitted power on-ground can be ... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.2.1.1 Open-loop control | The EIRP in the ground station is specified with 1 dB and can be controlled using Amplifier variable gain on Up-Converter to adjust the power. The major drawback of this method is that there is no control on the effective power received by the satellite. If the ground station suffers bad climatic environmental conditio... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.2.1.2 Close-loop control | If ground station environmental conditions create too much power unbalance on the co-located satellite, a close-loop control shall be implemented. The ground station shall be able to estimate the power received by the satellite and consequently estimate the environmental degradation. In a first approach, two means can ... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.2.1.3 Conclusion | The close-loop solution is very costly and open-loop control shall be considered as the base-line in standard definition. The close-loop control implies additional hardware and complexity. |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.2.2 Space equipment | The TM downlink EIRP is fixed on existing satellites, and cannot be changed (as it can be for the uplink TC ground station EIRP). For this reason, no power control is possible on existing satellites. The only power control strategy that can be applied on future satellites is to fix a typical TM EIRP for all the satelli... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.2.3 Collocation Equivalent Capacity (CEC) concept | To integrate the power imbalance of every signal of a multiple access system, the concept of Collocation Equivalent Capacity (CEC) is introduced below. The Collocated Equivalent Capacity (C.E.C) is defined as the number of collocated satellites that can be controlled with a perfect power balanced link between the groun... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.3 Modulation and Filtering Trade-off | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.3.1 Requirements | In order that TCR spread spectrum systems can be used along side communication channels at RF, some form of band limiting of the signal is required. Band limiting the signal at RF with very narrow bandwidth analogue filters is not generally practicable. Consequently control of the spectrum is generally implemented by p... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.3.2 Choice of Modulation | The following modulation schemes have been considered for band limited direct sequence spread spectrum systems application: • SRRC BPSK • SRRC QPSK • SRRC OQPSK • GMSK Where SRRC stands for Square Root Raised Cosine filtering or pulse shaping and GMSK is Gaussian pulse shaped Minimum Shift Keyed modulation. The impulse... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.3.3 TM downlink Modulation and Processing Gain | Three different implementations of the SS TM downlink in coherent mode are possible, for the channel allocation in QPSK. TM odd symbol + PN RG code 1 TM even symbol + PN RG code 1 delayed TM full symbol + PN RG code 1 TM full symbol + PN RG code 1 delayed I channel TM full symbol + PN RG code 1 PN RG code 1 I channel I... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.3.3.1 Option 1: OQPSK, even and odd data at half the rate in I and Q channel | The RF link budget performance is identical to BPSK. Impact on Processing gain is described below. Demodulator: Signal power in I CH 2 S I P S = ICH S ICH I ICH R P R S E 2 = = where RICH = RQCH = data rate in the channel = 2 b R Jammer spectral density is channel C j OI R P N 2 = ICH C J S J C ICH S OI ICH R R P P P R... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.3.3.2 Option 2: same data at full bit rate in both channels | From the RF link budget point of view, if the data bits are voltage added from each channel, there is no power share problem. The impact on Processing gain is described below. Demodulator : Signals: The I and Q channel bits are added voltage use (coherently) after detection in the filters. Jammer: The channel jammer no... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.3.4 Recommendations | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.3.4.1 General recommendation: | It is recommended that the TC and TM data shall be modulo 2 added to the appropriate spread spectrum uplink or downlink PN codes. Pulse shaping on the I and Q channels will be root raised cosine. Roll of factors vary typically between 1 and 0,2, a roll off factor of 0,5 is judged to feasible without undue complexity. T... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.3.4.2 Specific recommendation for SS TM | For the standard, option 2 (see clause 5.3.3.2) is recommended, as the best compromise performances/implementation. This enables a 3 dB improvement on the processing gain wart option 1. |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.4 PN CODE ACQUISITION | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.4.1 Introduction on PN code Acquisition | LOCAL PN GENERATOR LNA BAND PASS FILTER B (Hz) SQUARE FUNCTION INTEGRATE AND DUMP OVER T (sec) OUTPUT RECEIVED PN CODE CODE PHASE ADJUSTMENT Figure 12: simplified acquisition process at the satellite Figure 12 shows a very simplified PN code acquisition configuration for a satellite command spread spectrum receiver. Si... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.4.2 Integrate and Dump Dwell Time and Doppler Offset | Worst case Doppler offset for a GTO are estimated to be ±600 KHz at 18 GHz. During the acquisition process Doppler offset also appears proportionately on the PN code chip rate and is given by: s chip f c fR c R / ∆ = ∆ Where f ∆, f and c R are the RF Doppler offset frequency, the carrier frequency and the PN code chip ... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.4.3 Approximate Probabilities of Detection and False Alarm | The discussion here on probabilities of detection and false alarm of a PN code acquisition are based on [2], p. 422. The discussion applies to a fixed dwell integrate and dump detector following square law detection as depicted above. Figure 14 shows the probability density functions (PDF) at the output of the integrat... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.4.3.1 Case 1: Mean of the signal plus noise PDF equals the threshold level | PD = 0,5 in this case (i.e. the integral under the curve from the mean = threshold to plus infinity) therefore: 2 2 = = C N B and B o β τ ρ τ β For a false alarm probability of 1 % we obtain: C/N0 (dB) Bandwidth (B) Dwell Time 30 1 KHz 5,4 ms 30 1 MHz 5,4 s 45 1 MHz 5,4 ms |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.4.3.2 Case 2: Very good C/N0 | For this case we have: B of t independan P and dBHz B N C implies Say provided N C B B z D o o 1 ) log( 10 44 01 ,0 2 1 2 2 2 ) 2 1( 2 / 1 2 / 1 → + ≥ ≤ << − = − → + − = ρ β ρ β τ τρ ρ ρ τ β That is if the condition ) log( 10 44 B N C o + ≥ is met then good probability of detection is assured. |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.4.3.3 Case 3: Intermediate values of C/N0 | Have: 2 / 1) 2 1( ρ ρ τ β + − = B z Choose: iable B ms dBHz N C o var 1 33 ,2 45 = = = = τ β K By varying B we can obtain z and PD for the other fixed parameters. Examples are given in the table below. Bandwidth B (Hz) Normalized Variable z Probability of Detection PD 103 -3,65 0,9999 104 -2,83 0,9977 105 -0,65 0,7422 ... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.4.4 Long Code Acquisition | The ranging code or long code provides the ambiguity resolution for ranging. The long code modulates the Q channel of the unbalanced QPSK up link (no data modulation is present). Both the short code (command code) and the long code have to be epoch synchronized at the ground terminal. It is advantageous to have the lon... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.4.5 Preliminary Conclusions on PN code acquisition | The above results on acquisition are approximate and have to be ultimately determined by simulation and measurement. However, trends in the results demonstrate that: • Narrow filter bandwidths give good performance without Doppler or with Doppler aided carrier tracking loops. Otherwise with Doppler uncertainty many Dop... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.5 DS/CDMA code trade-off | Different codes can be used for DS/CDMA techniques. Each code has its own characteristics. |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.5.1 Description of different codes family | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.5.1.1 M sequences | • few polynomials available. • even cross correlation: ≈1/N. • ideal for synchronization with sequence of 1 1 1 1 1 1 1 1. |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.5.1.2 Gold codes | • (N+2) polynomials available • even cross correlation: ≈1/√N |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.5.1.3 Kasami codes | • ≈√N polynomials available (better than Gold). • even cross correlation: ≈1/√2N. |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.5.1.4 Walsh Hadamard codes | • synchronized codes. • unbalanced number of "1"and 0": necessity to add another spreading code. • perfectly orthogonal code. ETSI ETSI TR 101 956 V1.1.1 (2001-09) 40 |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.5.1.5 Gold code with preferential phase | • synchronized codes. • similar to Gold, but quasi orthogonal codes. • ≈N polynomials available. |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.5.2 Pros and cons of code synchronization | • Advantage: - theoretically perfect correlation between codes. • Drawback: - very complex to implement for the uplink (different TCR stations are used for a group of co-located satellites); - very complex to implement for the downlink (all the co-located satellites clock would have to be perfectly synchronized); - ver... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.6 Tracking Receiver on Spread Spectrum (SS) signal | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.6.1 Hypothesis | Spread spectrum signal for TM is used by antenna tracking receiver. The tracking receiver uses mono-pulse technique, which reveals to be well suited for meeting pointing accuracy requirements for Ku-Band signals. |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.6.2 Analysis | Need for de-spreading the error signal: As the TM signal is spread, the tracking receiver will not be able to lock on the signal. A de-spreading/demodulator module shall be implemented to recover error signals (∆Az/∆El) from sum (Σ) signal and delta (∆) signal (orthomode coupler), then the tracking receiver will be abl... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 5.6.3 Conclusion | It is possible to use spread-spectrum signals to track satellites using mono-pulse antenna system, using TM acquisition module. Nevertheless, today, no engineering model exists to validate this analysis. As a consequence, achieving an antenna tracking system using satellite spread spectrum signals will require addition... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6 Trade-off between different solutions | The trade-off between the solutions will be done, depending of the performance of: • Capacity • Operational constraints • RF compatibility with the COM signal • Equipment feasibility |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.1 Description of the potential solution | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.1.1 Telecommand function | Three possible command solutions are envisaged: • Wide band SS TC: The TC is spread over a COM channel (typically over 36 MHz). • Narrow band SS TC: the TC is spread in a bandwidth adjacent to the COM channel, in edge of the COM channels frequency bandwidth. Typically, this bandwidth left for TCR is a few MHz wide. • S... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.1.2 Telemetry function | Three possible TM solutions are envisaged: • Wide band SS TM: the TM is spread over a COM channel (typically over 36 MHz). • Narrow band SS TM: the TM is spread in a bandwidth adjacent to the COM channel, in edge of the COM channels frequency bandwidth. Typically, this bandwidth left for TCR is a few MHz wide. • STD TM... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.1.3 Ranging function | 4 possible RG solutions are envisaged: • Wide band SS RG: the RG is spread over a COM channel (typically over 36 MHz) and the RG signal is directly down converted and amplified by the COM repeater. • Wide band SS RG: the RG is spread over a COM channel (typically over 36 MHz) and the RG regenerated on-board. • Narrow b... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.1.4 Selection of the potential solutions | The detailed analysis of all the combinations of telemetry, command and Ranging solutions cannot be performed (3 × 3 × 4 cases = 36 cases). Certain configurations have to be directly discarded, as explained in table 3. Table 3: selection of the potential solution TM STD modulation TM SS NB TM SS WB RG SS WB Transparent... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.2 Hypothesis and principle of the analysis: | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.2.1 General hypothesis on the system | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.2.1.1 Satellite configuration | Figure 15 shows just one possible satellite configuration. Features include: • Communication antennas covering TCR stations locations. • Transparent transponder for communication traffic. • TC signals are tapped off after amplification from the LNA. • TM signals added into the downlink path after HPA. INPUT FILTER IMUX... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.2.1.3 TCR frequency plan adjustment for narrow band Spread Spectrum | The location of the TCR frequencies in the frequency plan can affect the inter-compatibility properties of the system. Six cases are possible for narrow band Spread Spectrum (see figure 18). COMMS CH’S TC UPLINK TM DOWNLINK COMMS CH’S TC UPLINK TM DOWNLINK NRZ-L SP-L OR BI-PHASE COMMS CH’S TC UPLINK TM DOWNLINK 1 2 3 C... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.2.2 RF hypothesis | The standard shall be applicable for C and Ku band; but all the simulations are performed in the worst case in terms of band, that is the Ku band. In this clause, RF link budgets results will be presented. Those RF budgets are given for TCR signals, and for COM signals, to evaluate any interference between both signals... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.2.2.1 Principle of the analysis | Parameters that are fixed COM signal characteristics (power at repeater input, on board EIRP, bandwidth). Architecture of the TCR of existing satellite (standard modulation). This architecture defines typical losses between repeater input and TC receiver. It defines also TC threshold , and TM on board EIRP. Parameters ... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.2.2.2 RF Assumptions for the COM signals | No generic COM signal exists that can represent every COM scenario. To show something representative of real system, three typical COM scenarios have been envisaged. The technical parameters associated to those scenarios are presented in table 4. Table 4: Description of the different COM scenarios COM uplink characteri... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.2.2.3 RF Assumptions for the TCR signals | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.2.2.3.1 Uplink | For the TC uplink SS signal Assume PSK modulation (BPSK or QPSK with RG), occupied bandwidth of the main lobe = 2 x chip_rate). For narrow band SS TCR, the main lobe of the PN spreading sequence is NOT in the communication channel. Then the highest PSD will be at the 1st side lobe, which is 13 dB down from that at the ... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.2.2.3.2 Downlink | SS TM downlink TCR Ground station G/T = 25 dB/K SS modulation implementation losses = -3 dB The required Eb/N0 of the TM data at TM ground receiver output shall correspond to a BER better than 10-5. If FEC is present, it corresponds to an Eb/N0 ratio up to 4,6, otherwise, it corresponds to an Eb/N0 ratio up to 9,6. STD... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.2.3 Success criteria | Success criteria for the jamming of the COM The analysis will have to prove that, for each of this scenario, the COM will not be degraded by more than 3 %. Success criteria for the jamming of the STD TC uplink signal The C/N0 (N0 being the contribution of every jammer, including spread spectrum link, COM link, thermal ... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.3.1 Description of the solution | Uplink: modulation SRRC-UOQPSK, ratio I(TC)/Q(RG) = 10/1 dB, roll-off factor α = 0,5 • TC bit rate: 500 bit/s or 1 kbit/s • TC code length = 210 -1 = 1 023, Gold code • TC chip rate: 500 kchip/s to 3 Mchip/s • synchro bit TC/chip TC: not foreseen • RG code length: compatible with a 5 000 km ambiguity • RG chip rate = T... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.3.2 RF performances | |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.3.2.1 Specific hypothesis for solution 1 | As explained in clause 6.2.2.1, some parameters shall be adjusted for the RF link budget: • It is decided, arbitrarily, to fix the on-board losses between COM LNA and TC SS receiver to -5 dB. • The SS TC EIRP is adjusted between 44,5 dBW (no FEC) and 39,5 dBW (FEC present). • The SS TM EIRP is adjusted between 9 dBW (n... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.3.2.2 Parametric analysis results | Parameters being modified during the parametric analysis: • Capacity • Chip rate • SS TC Data rate • FEC coding for SS TC (and depending of this option, SS TC EIRP is adjusted) • FEC coding for SS TM (and depending of this option, SS TM EIRP is adjusted) Parameters that are analysed, as result of the analysis: • STD TC... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.3.2.2.1 No SS TC FEC, no SS TM FEC | SS TC bit rate: 500 bit/s, no SS TC FEC coding -2,0 0,0 2,0 4,0 6,0 0 5 10 15 20 CECup SS TC margin (dB) 0,5 Mchip/s 1 Mchip/s 3 Mchip/s no SS TC FEC coding -1,0 0,0 1,0 2,0 3,0 0 5 10 15 20 capacity STD TTC margin (dB) 0,5 Mchip/s 1 Mchip/s 3 Mchip/s no SS TC FEC, no SS TM FEC coding 0,0% 5,0% 10,0% 15,0% 0 5 10 15 20... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.3.2.2.2 SS TC FEC, SS TM FEC | SS TC FEC coding 0,0 1,0 2,0 3,0 0 5 10 15 20 CECup STD TTC margin (dB) 0,5 Mchip/s 1 Mchip/s 3 Mchip/s SS TC bit rate: 500 bit/s, SS TC FEC coding -2,0 0,0 2,0 4,0 6,0 0 5 10 15 20 CECup SS TC margin (dB) 0,5 Mchip/s 1 Mchip/s 3 Mchip/s SS TM FEC coding 0,0 2,0 4,0 6,0 8,0 10,0 0 10 20 30 40 50 60 CECdown STD TM margi... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.3.2.2.3 No SS TC FEC, SS TM FEC | no SS TC FEC, SS TM FEC coding 0,0% 2,0% 4,0% 6,0% 8,0% 10,0% 0 5 10 15 20 CECup COM degradation (%) 0,5 Mchip/s 1 Mchip/s 3 Mchip/s The results shown below are given for different configurations. ETSI ETSI TR 101 956 V1.1.1 (2001-09) 53 6.4 Solution 2: any RG, TC SS (narrow or wide band), TM wide band SS |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.4.1 Description of the solution | Uplink: like solution 1, for example. Downlink: modulation UQPSK, ratio I(TM)/Q(RG) = 10/1 dB. • TM bit rate: 2 048 bit/s to 4 096 bit/s. • TM code length = 1 023 chips (non coherent) or as RG code length (in coherent mode). •• FEC optional. •• TM chip rate: compatible with the use of the COM channel: 18 Mchip/s max. I... |
1af665171ad5782d3c09f2faccdce1eb | 101 956 | 6.4.2 RF performances |
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