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Network-Coded Multiple Access

Network-Coded Multiple Access. Presented by Soung Liew (Joint Work with Lu Lu, Lizhao You, Shenghao Yang) Institute of Network Coding The Chinese University of Hong Kong. Background on PNC. First proposed in Mobicom 06 [1] A subfield of Network Coding building up momentum in recent years:

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Network-Coded Multiple Access

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  1. Network-Coded Multiple Access Presented by Soung Liew (Joint Work with Lu Lu, Lizhao You, Shenghao Yang) Institute of Network Coding The Chinese University of Hong Kong Soung Liew, CUHK

  2. Background on PNC • First proposed in Mobicom 06 [1] • A subfield of Network Coding building up momentum in recent years: • Google scholar citations: 1000+ (annual growth ~300) • A main topic in special journal issues and numerous conferences. • A main topic in an upcoming IEEE JSAC issue on wireless network coding • Half-day workshop in IEEEWNCN 2013: New Advances for PNC • Invited talks [1] S. Zhang, S. C. Liew, P. P. Lam, “Physical-Layer Network Coding,” ACM Mobicom 2006 . Similar idea in [2] P. Popovski and H. Yomo, “The anti-packets can increase the achievable throughput of a wireless multi-hop network,” ICC 2006. Soung Liew, CUHK

  3. SA SB A R B Simplest Set-up: Two-Hop Linear Network • Two-way Relay Channel (TWRC) • No direct channel between nodes A and B. • Half duplex: nodes cannot transmit and receive at the same time. • What is the minimum number of time slots needed for nodes A and B to exchange one packet via relay R? Soung Liew, CUHK

  4. PNC SA SB A R B Time slot 2 Time slot 1 Transmissions by nodes A and B are simultaneous! Soung Liew, CUHK

  5. PNC for Multiple Access (Non-Relay Setting)? • Access point wants to get both Message A and Message B, not just their XOR • Does PNC have a role to play? Access Point Relay Network Wireless LAN Soung Liew, CUHK

  6. A AP B PNC In Non-Relay Network: Network Coding Multiple Access (NCMA) • Nodes A and B send CA and CB to AP simultaneously • AP tries to decode packets CA, CB, and Soung Liew, CUHK

  7. PHY-Layer Decoders of NCMA Soft Information (Log Likelihood Ratio: , k=1,2,… ) Soung Liew, CUHK

  8. PHY-layer Bridging Soung Liew, CUHK

  9. Are Lone XOR Packets Useful? Complementary XOR Lone XOR • Do lone XOR packets have a role to play? Soung Liew, CUHK

  10. MAC-Layer Erasure Code + PHY-Layer Channel Code Soung Liew, CUHK

  11. MAC-Layer Bridging with L = 3 Soung Liew, CUHK

  12. Experiments: Layout of Indoor Environment for 9 USRP N210 Nodes Institute of Network Coding (INC) Soung Liew, CUHK

  13. PHY-Layer Packet Decoding Statistics(Balanced Power Case) AB: Both A and B decoded AX|BX: A and XOR decoded or B and XOR decoded A|B: Either only A or only B decoded X: Only XOR decoded Soung Liew, CUHK

  14. PNC decoding works but MUD does not when phases are aligned Received Signal Decode Outcomes Soung Liew, CUHK

  15. PNC does add value when phases are severely misaligned Received Signal Decode Outcomes Soung Liew, CUHK

  16. Combination of PNC and MUD is effective when phases are moderately misaligned Received Signal Decode Outcomes Soung Liew, CUHK

  17. Overall Throughputs of Different Schemes for Different SNRs LA = 1.5×LB= 24. Soung Liew, CUHK

  18. Pairing Strategies Scenario: Four users at locations 2, 3, 4, 5. How to form pairs? Strategy 1: pair 2 with 3; 4 with 5 Strategy 2: pair 3 with 4; 2 with 5 12.3dB 9dB 7dB 7.4dB Pair “strong with weak” rather than “strong with strong and weak with weak” Soung Liew, CUHK

  19. Linearly Coupled Codes at MAC Layer • Single-equation System: Soung Liew, CUHK

  20. Linearly Coupled Raptor Codes • Near optimal and availability of fast decoding Soung Liew, CUHK

  21. Dynamic Equation Soung Liew, CUHK

  22. Degree Optimization Problem For some positive integer Soung Liew, CUHK

  23. Use SIC at low SNR Regime • Suppose an (N,3) RS code PHY-layer SIC 1 2 3 Cross-layer SIC 4 5 Message decoding Soung Liew, CUHK

  24. Overall Throughputs of Different Schemes for Different SNRs LA = 1.5×LB= 24. Soung Liew, CUHK

  25. NCMA: Conclusion • First venture into non-relay (multiple-access) setting for PNC • PNC may have a role to play in the multiple access scenario: • To simplify decoder design • For delivering jumbo messages • Ongoing NCMA Investigations: • Better performance for high and low SNR regime • Investigation of linearly-coupled code for MAC layer of NCMA Soung Liew, CUHK

  26. The End Soung Liew, CUHK

  27. Throughputs of Four User Pairs Soung Liew, CUHK

  28. Overall Throughputs of Different Schemes with RS code parameter LA= 4, 8, 16, 32, and fixed SNR = 9dB. Soung Liew, CUHK

  29. PNC Implementation: Wireless • Frequency-Domain PNC (FPNC) in GNU Radio testbed, A R B Soung Liew, CUHK

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