Communication Subsystem

1. Communication Subsystem

2. Introduction • Hardware • Protocol Description • Interface • Examples • Test • Link Budget • Conclusion

3. Table of Contents • Hardware • Protocol Description • Interface • Examples • Test • Link Budget • Conclusion

4. Hardware • OSSS • Vital Part • Testing • MIL-STD-1540 • Power Interface?

5. Specifications • Frequency: 430-450 MHz • Bitrate: 9600 baud • Voltage: 3.3-5 V and 7.5-12 V • Power output: 2W@9.6V • Current Drain: • Transmitting: 940mA@2W • Receiving: 60mA • Mass: 100 g

6. Interface

7. Ground Station • Modem from OSSS • No Final Solution • Yagi Antenna  16 dB gain • NOVA Rotor Control • Price  10.000 - 20.000 Kr. • Brian Lodahl from KOM

8. Table of Contents • Hardware • Protocol Description • Interface • Examples • Test • Link Budget • Conclusion

9. Requirements • Flawless Link • Support Call-names • Pause / Resume • Prioritizing • Channels • Half Duplex

10. Layer Structure

11. AX.25 • Error Detection • Supports Call-names • Supports Half Duplex • Connections • Widely Used • Well Documented

12. T55X Structure

13. T55X Transport Layer • Channels • 16 Channels • Priorities • Fixed Priorities • Pause / Resume

14. Data-A Packet-A1 Packet-A1 Packet-A1 Data-B Packet-A2 Packet-B1 Packet-B1 Packet-B1 Data-B Packet-A2 Packet-A2 Data-A Example Channel 1 Channel 2 Channel 1 Channel 2 Scheduler Application Application De-Mul

15. Table of Contents • Hardware • Protocol Description • Interface • Examples • Test • Link Budget • Conclusion

16. Interface • Callback Functions • Receive Data • Receive Events / Beacon • Send Connection Less Data • Send Data • Connect / Disconnect • Complete API on WWW • www.control.auc.dk/~01gr555/api/

17. Table of Contents • Hardware • Protocol Description • Interface • Examples • Test • Link Budget • Conclusion

18. Start Communication Satellite: while(true) do sendConLess(housekeeping) sleep(rtt+ct) if status=CONNECTED then break sleep(30 s) Ground Station: SetupCall-back(handleEvent(type, data)) handleEvent(type,data) { If type=DATA_RECEIVED then store(data) connect }

19. sendConLess Lost in space getStatus 30 sec sendConLess handleEvent connect getStatus Sequence Chart Ground Satellite Satellite Ground protocol protocol applications applications

20. Send/Receive Ground Station: Start: createChannel(8,receiveImage) createChannel(2,commandChannel) Main: ....... sendData(2,Take Picture) ........ Callback: receiveImage(data){ Save(data) sendEventToAdmin(Received Image) }

21. Send/Receive Satellite: Start: createChannel(8,imageChannel) createChannel(2,receiveCommand) Callback: receiveCommand(data){ if data=’take image’ then takeImage sendData(8,image) }

22. Time Synchronization • Several Solutions • Connection Less • Channel With Estimation • No Requirements Yet

23. Table of Contents • Hardware • Protocol Description • Interface • Examples • Test • Link Budget • Conclusion

24. Modelling and Verification • Why? • Short Implementation Test Time • New Protocol • Satellite • What: • SDL Modelling • Exhaustive Testing • Code Generation • Tools: • ObjectGeode

25. Table of Contents • Hardware • Protocol Description • Interface • Examples • Test • Link Budget • Conclusion

26. Link Budget • Link Budget equation or Ebno • EIRP: • (Equivalent Isotropically Radiated Power) • G/T: • Quality factor of receiver

27. Link Budget • Max distance to satellite • Using Pythagoras: • Inserting into the equation

28. Effective Throughput • I frame size: 24 - 276 bytes • 23 bytes overhead • S frame size: 19 bytes

29. Effective Throughput • Data: • Beacon:

30. Table of Contents • Hardware • Protocol Description • Interface • Examples • Test • Link Budget • Conclusion

31. Conclusion • Work So Far: • Analysis / Design / Modelling / API • Hardware • To Do: • Implementation • Verification / Test • Purchase from OSSS • Ground Station