ESA project 1300008360 UWB radio for cable replacement in Satellites

1. ESA project 1300008360UWB radio for cable replacement in Satellites Technical Note 1.1 “Hardware description, environment and test plan”

2. Introduction Feasibility study for use of UWB radio for cable-replacements in intra-satellite communication. Project contains 3 activities: • Hardware description, environment and test plan • Outcome: (TN1.1 = document) • Measurement campaign • Outcome: (TN1.2a=Zip-file) • Test report and analyses • Outcome: (TN1.2= > update of TN1.1) • 2 versions: with and without confidential information This presentation reports on TN1.2

3. Outline of the document 1 Introduction ................................................................................. 1 2 IEEE802.15.4a UWB air interface........................................... 3 3 Top-level description of IMEC UWB transceivers..... ......... 11 4 Methodology................................................................................ 27 5 Venus express Mock-up description ...................................... 29 6 Channel Measurements and Modelling ................................. 33 7 Simulation framework and results ......................................... 67 8 Conclusions and recommendations....................................... 73 9 Bibliography................................................................................... 75

4. 802.15.4a standard • 3 modes => mean Pulse repetition freq • 15.6 MHz • 3.9 MHz • 62.4 MHz • 4 submodes => PHY bitrate • 27Mb/s • 6.8 Mb/s • 850 kb/s • 110 kb/s • Off standard modes allow for other data rates as well • Use of ASIP/ASIC combination makes TX/RX flexible! • Unique to IMEC technology

5. Methodology

6. Environment & measurements Channel measurements showed the validity of these assumption • Parameters: • Satellite: • Highly reflective environment • Significant reflection up to one microseconds • BW: • 1-11 GHz (covers much communication standards) • Time resolution => 100 picoseconds • #FreqPoint > 1microsec/100picosec(=10k) • Nearest power of 2 => 16384 (DFT => FFT ) • FreqStep = 610 kHz. • Result: H[f] => H(f)

7. Freq to delay • Only valid if channel is constant • True if doors are closed • Not guaranteed if doors are opened Freq domain DFT Delay domain H[f,t] (=S21) <=> H[tau,t]

8. Measurement requirement • Measurement of H(f,t) takes approx 2 sec! • Nothing may move more than 0.5cm over 2 seconds in relevant area! • Relevant area = area relevant paths act. • Do relevant paths exit & return from Mock-Up? • True if doors are closed • False if doors are opened!

9. Measurement Setup =keyhole

10. Channel measurement resultsPath loss Channel gain as a function of carrier frequency with a sliding window.

11. Channel measurement resultsPath loss Path losses (units in dB) for inter cavity measurements. Channel gain as a function of the number of keyholes Large scale path loss

12. Channel measurement resultsImpact of antenna position LOS, Close proximity NLOS, Antennae at opposite Key holes Intra cavity measurements VNA channel 1 (Tx) and VNA channel 2 (Rx) in cavity 5 with 8 different antenna position configurations.

13. Channel measurement resultsImpact of open doors Effect of opening and closing of doors on the link-budget for inter cavity measurements VNA channel 1 (Tx) in cavity 2 and VNA channel 2 (Rx) in cavity 5 with many different door configuration. Doors 2 and 5 have the biggest impact. • The opening of doors may lead to a channel gain loss up to 18 dB

14. Channel measurement resultsDelay domain RMS delay spread (units in ns) for inter cavity measurements. Real measured data for inter cavity measurement of cavity 1 to cavity 3, and synthetically generated data with the aid of two exponential functions and a noise floor describing the envelope.

15. Channel measurement resultsDelay domain Ricean factors (units in dB) for inter cavity measurements. Histogram of received signal voltage from 4 - 5 GHz and the estimated Ricean and Rayleigh distribution for both VNA channel 1 (Tx) and VNA channel 2 (Rx) in cavity 2. Small scale fading is Rayleigh distributed

16. Channel measurement resultsMinimum and Maximum Path Losses The 2σ confidence intervals corresponding to the channel gain for the seven 1GHz windows for both intra and inter cavity measurements as a function of the number of 12 x 12 cm keyholes, i.e. hops. Intra cavity measurement in cavity 3 with 2σ confidence intervals over 1GHz windows. Solid line, UWB, striped line, WLAN, dotted line, Raw Data. • 2σ 5 dB mean power gain variation due to small scale fading. • Mean power mainly depends on cavity not on position

17. Simulation results Iff CRC passes Added CRC16 Flexible PSDU size non-coherent reception Flexible Data rate/ Modulation scheme Complex-valued BB equiv. system model Noise equal to measured RXFE noise-figure • Flexible 802.15.4a simulation environment • Matlab

18. Simulation results CRC check PHY HDR decoding Fine acquisition SFD detection Only successful reception if everything goes well. • PER as measure for performance: • most honest but worse-case performance criteria

19. PER with closed doors • Reasons: • Low average pathloss, • highly reflective environment • Keyholes are larger enough • Hardly no small-scale fading • UWB is able to resolve many multipath components • Many things can go wrong, but it does not;-)

20. PER with open doors • With 1 hop everything is fine • 3 hops is too much • Reason: • Energy leaks into environment, lowering RX power • But: • ‘only’ 10 dB improvement needed • Link improvement are possible • ↑TX power, ↓noise figure • Tailor BB processing • Network layer Many things can go wrong, and here it does;-(

21. conclusion • The satellite’s radio channel is a high reflective/multipath-rich environment in which radio signal are able to propagate from one cavity to the next. • The large scale path loss of the channel for a frequency range of 3-10 GHz varies between -25dB (intra-cavity) to-58dB (cavity 1 to cavity 6) with closed doors. • The RMS delay spread varies between 40.7 ns (intra-cavity) and 118.6 ns (cavity 1 to cavity 6). • The small-scale-fading for narrowband systems is Rayleigh distributed even in LOS conditions. An example of such a narrowband system is 802.15.4. To obtain robust communication links, some form of diversity will be needed. • UWB systems experience a mean power gain variation of at most 5 dB due to small-scale-fading, due to its inherent frequency diversity. • The mean power gain of the channel depends mainly on the cavities of TX and RX, i.e. the exact position of the TX/RX within these cavities has little impact.

22. Conclusion • Opening of the satellite doors may lead to a decrease of the channel gain in the order of 15-18 dB for intra cavity channel and 10-13 dBs for inter cavity channels; depending on the contribution of the door as reflective object to the overall channel transfer function. • The most difficult channels are measured from cavity 1 to cavity 6 with open doors at high frequencies (6-10 GHz), where a mean power gain of -70 dB was recorded. • Imec’s current 802.15.4a-compliantUWB radio technology is able to provide for robust communication links at 600 kb/s netto data rate without packet loss: • from each cavity to every other cavity, if the doors are closed. • Very likely from each cavity to adjacent cavities with open doors. • Imec’s current 802.15.4a-compliant UWB radio technology is not able to provide for robust communication links from each cavity to every other cavity at 600 kb/s netto data rate without packet loss, if all doors are open and the cavity distance (hops) is larger than 1.

23. Channel measurement results • The satellite’s radio channel is a high reflective/multipath-rich environment in which radio signal are able to propagate from one cavity to the next. • The large scale path loss of the channel for a frequency range of 3-10 GHz varies between -25dB (intra-cavity) to-58dB (cavity 1 to cavity 6) with closed doors. • The RMS delay spread varies between 40.7 ns (intra-cavity) and 118.6 ns (cavity 1 to cavity 6). • The small-scale-fading for narrowband systems is Rayleigh distributed even in LOS conditions. An example of such a narrowband system is 802.15.4. To obtain robust communication links, some form of diversity will be needed. • UWB systems experience a mean power gain variation of at most 5 dB due to small-scale-fading, due to its inherent frequency diversity. • The mean power gain of the channel depends mainly on the cavities of TX and RX, i.e. the exact position of the TX/RX within these cavities has little impact. • Opening of the satellite doors may lead to a decrease of the channel gain in the order of 15-18 dB for intra cavity channel and 10-13 dBs for inter cavity channels; depending on the contribution of the door as reflective object to the overall channel transfer function.

24. recommendations • EMC • Study ESA’s EMC requirement wrt FCC part 15 regulation for intentional radiators • EMC center Eindhoven could play a role!

25. recommendations • Centralized network topology • Only intra-cavity communication, • Inter cavity communication via wired bus system • Increased system capacity • Beneficial if one of few data-sink can be identified • Ad-hoc network topology • Each sensor/tag may communicate to any other sensor/tag • More complicated MAC (assuming no fixed addressing)