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Innovations in Physical-layer Network Coding: Prototyping and Applications

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This workshop explores the advancements in Physical-layer Network Coding (PNC) and its real-time applications. Participants will gain insights into the background of PNC, challenges in its realization, and the implementation of a real-time PNC prototype. The workshop will cover both relay and non-relay settings, showcasing experimental setups, performance evaluations, and video demonstrations. Attendees will learn how PNC can optimize throughput and exploit network coding in wireless networking. Join us to discover the potential of PNC in enhancing communication systems.

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Innovations in Physical-layer Network Coding: Prototyping and Applications

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  1. Network Coding Innovation Technology Workshop Physical-layer Network Coding: Prototyping and Application Lu Lu 30th August 2013

  2. Outlines • 1. Background of Physical-layer Network Coding (PNC) • 2. Real-time PNC Prototype • Demo Video • PNC Realization Challenges • 3. PNC in Non-relay Setting • Experimental Setup • Performance Evaluation • 4. Conclusion PNC Prototyping & Application

  3. What is PNC? • Traditional view in wireless networking: interference is bad. • PNC turns things around by exploiting network coding (NC) performed by nature. • When electromagnetic waves superimpose, they add, a form of NC. • Benefits of PNC: • boost throughput PNC Prototyping & Application

  4. Simplest Set-up: Two-Hop Relay Network R • System Model: 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 node R? B A PNC Prototyping & Application

  5. Time slot 1 Traditional Scheduling (TS) • Transmissions non-overlapping in time PA PA A R B PB PB Time slot 2 Time slot 4 Time slot 3 PNC Prototyping & Application

  6. Straightforward Network Coding (SNC) • Transmissions by nodes A and B still non-overlapping • Relay R uses one time slot to broadcast PA PB A R B Time slot 2 Time slot 1 Time slot 3 PNC Prototyping & Application

  7. Physical-layer Network Coding (PNC) • Transmissions by nodes A and B are simultaneous! PA PB A R B Time slot 2 Time slot 1 PNC Prototyping & Application

  8. Outlines • 1. Background of Physical-layer Network Coding (PNC) • 2. Real-time PNC Prototype • Demo Video • PNC Realization Challenges • 3. PNC in Non-relay Setting • Experimental Setup • Performance Evaluation • 4. Conclusion and Future Works PNC Prototyping & Application

  9. Specifics • Frequency-domain PNC (FPNC) for TWRC • Build on OFDM technology as used in Wi-Fi • First PNC implementation in 2012 • First real-time PNC implementation in 2013 • Support “real” application in real-time through API PNC Prototyping & Application

  10. PNC Implementation: Wireless • Frequency-Domain PNC (FPNC) in GNU Radio testbed A R B PNC Prototyping & Application

  11. Demo Video: Real-Time File Exchange with PNC • A short video followed by a demo See demo video in http://www.youtube.com/watch?v=HmRBm_IIBQQ PNC Prototyping & Application

  12. PNC Realization Challenges • Asynchrony • Signals from nodes A and B may arrive at the relay R with symbol and carrier-phase misalignments • Solution: PNC with OFDM (FPNC) • Channel Estimation • Relay needs to estimate two channels based on simultaneous signals • Solution: FPNC Frame Format Design PNC Prototyping & Application

  13. Frame format for RPNC Data Totally Overlap User Detection Channel Estimation PNC Prototyping & Application

  14. PNC Realization Challenges • Channel-decoding and Network Coding (CNC) • Tradeoff between optimality and simplicity • Solution: Opt for simplicity; adopt 802.11 convolutional code and XOR-CD CNC. Reduced constellation approach • ARQ for Retransmission • End-to-end ARQ or Relay-assisted ARQ • Solution: Opt for simplicity; adopt end-to-end ARQ PNC Prototyping & Application

  15. Single-user Channel Decoder and PNC Channel Decoder in Overall RPNC System PNC Decoder Soft Information (Log Likelihood Ratio: , k = 1, 2,… ) PNC Prototyping & Application

  16. Reduced Constellation Approach to Computing Soft Information on XOR bit Received sample with noise Mapping four constellation points to two Constellation points for log likelihood computation • BPSK for both nodes A and B • Between two points of the same XOR, choose the one with the shorter Euclidean distance PNC Prototyping & Application

  17. PNC Realization Challenges • Long Latency between USRP-PC • The turn-around time for USRP-PC may be long and unpredictable • Solution: Burst Transmission Mode PNC Prototyping & Application

  18. Burst Transmission Mode in RPNC Uplink Downlink PNC Prototyping & Application

  19. Normalized throughput of PNC and TS PNC can double the throughput PNC Prototyping & Application

  20. Outlines • 1. Background of Physical-layer Network Coding (PNC) • 2. Real-time PNC Prototype • Demo Video • PNC Realization Challenges • 3. PNC in Non-relay Setting • Network Coding Multiple Access (NCMA) • Performance Evaluation • 4. Conclusion and Future Works PNC Prototyping & Application

  21. PNC in 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 Wireless LAN PNC Prototyping & Application

  22. PNC In Non-Relay Network: Network Coding Multiple Access (NCMA) A AP B • Nodes A and B send to AP simultaneously • AP uses three decoders to separately decode packet A, packet B, and packet A B • Eight possible events: • Packets A, B, and A B decoded • Packets A and B decoded • … • Packet A B decoded • None decoded PNC Prototyping & Application

  23. PHY-Layer Decoders of NCMA Soft Information (Log Likelihood Ratio: , k = 1, 2,… ) PNC Prototyping & Application

  24. Alternatives for MUD Decoding MUD Decoder PNC Prototyping & Application

  25. NCMA: PHY-layer Bridging PNC Prototyping & Application

  26. Are Lone XOR Packets Useful? Complementary XOR Lone XOR • Do lone XOR packets have a role to play? PNC Prototyping & Application

  27. MAC-Layer Erasure Code + PHY-Layer Channel Code PNC Prototyping & Application

  28. NCMA: MAC-Layer Bridging with L = 3 PNC Prototyping & Application

  29. Experiments: Layout of Indoor Environment for 9 USRP N210 Nodes Institute of Network Coding (INC) PNC Prototyping & Application

  30. PHY-Layer Packet Decoding Statistics(Balanced Power Case) Solo XOR packets 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 PNC Prototyping & Application

  31. Overall Throughputs of Different Schemes with RS code parameter LA = 4, 8, 16, 32, and fixed SNR = 9dB. PNC Prototyping & Application

  32. Overall Throughputs of Different Schemes for Different SNRs LA = 1.5×LB= 24. PNC Prototyping & Application

  33. Throughputs of Four User Pairs PNC Prototyping & Application

  34. Pairing Strategies Scenario: Four users at locations 2, 3, 4, 5. How to form pairs? Strategy 1: P2 and P4 Strategy 2: P3 and P5 Pair “strong with weak” rather than “strong with strong and weak with weak” PNC Prototyping & Application

  35. NCMA: Overall Summary A AP B • First venture into non-relay setting for PNC • PNC may have a role to play in the multiple access scenario • for simplification of decoder design • for jumbo messages PNC Prototyping & Application

  36. Outlines • 1. Background of Physical-layer Network Coding (PNC) • 2. Real-time PNC Prototype • Demo Video • PNC Realization Challenges • 3. PNC in Non-relay Setting • Experimental Setup • Performance Evaluation • 4. Conclusion PNC Prototyping & Application

  37. Conclusions • There has been a lot of theoretical work on PNC • Relatively few experimental investigations • RPNC: The first real-time PNC prototype • NCMA: PNC can be applied in a non-relay setting to boost system throughput • Future: apply PNC and NCMA to commercial wireless networks: cellular (e.g., LTE-A) and WLAN PNC Prototyping & Application

  38. PNC Prototyping & Application

  39. To Probe Further • “Implementation of Physical-layer Network Coding,” in ICC ’12 and Phycom, Mar. 2013. • “Real-time Implementation of Physical-layer Network Coding,” in SRIF ’13, an ACM SIGCOMM Workshop. • “Network-coded Multiple Access,” Technical Report, http://arxiv.org/abs/1307.1514. PNC Prototyping & Application

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