Physical Layer Network Coding with Signal Alignment

1. Physical Layer Network Coding with Signal Alignment Ruiting Zhou+,Zongpeng Li+, Chuan Wu*, Carey Williamson+ +University of Calgary *University of Hong Kong

2. Outline • 1. Introduction • 2. PNC-SA Scheme • 3. Precoding Design and BER Analysis • 4. General Applications of PNC-SA and Throughput • 5. Conclusion Ruiting Zhou Univerisity of Calgary

3. 1. Introduction • MIMO: Multi-input multi-output • Throughput is limited by the number of antennas per AP Figure 1: MIMO LANs Ruiting Zhou Univerisity of Calgary

4. 1. Introduction • Second client-AP pair, transmit >2 packets? No! • Interference Alignment and Cancellation (IAC) breaks through this bottleneck • IAC allows 3 concurrent packets • Transmitters can control the alignment of their signals at a receiver • APs are typically connected to a backend Ethernet Ruiting Zhou Univerisity of Calgary

5. 1. Introduction • IAC treats the second and third packets as one unknown • AP1 sends on the Ethernet to AP2 Figure 2: IAC example Ruiting Zhou Univerisity of Calgary

6. 2. PNC-SA Scheme • Introduction to Digital Network Coding • Physical-Layer Network Coding • Physical layer Network Coding withSignal Alignment Scheme Ruiting Zhou Univerisity of Calgary

7. 2. PNC-SA Scheme • Traditional Transmission Scheduling: 4 time slots. • Digital Network Coding: 3 time slots • It is applied on digital bits that have been correctly received: Ruiting Zhou Univerisity of Calgary

8. 2. PNC-SA Scheme • Physical-Layer Network Coding (PNC): 2 time slots • Additions of the EM signals are mapped to additions of digital bit streams • BPSKmaps from{-1, 1} to {0, 1} • PNC demodulation maps from {+2, 0, -2} to {0, 1} Ruiting Zhou Univerisity of Calgary

9. 2. PNC-SA Scheme • Physical layer Network Coding withSignal Alignment (PNC-SA) • Align simultaneous transmissions from multiple MIMO senders. Figure 3: PNC-SA Ruiting Zhou Univerisity of Calgary

10. 3. Precoding and BER Analysis • Precoding — Alignment constraint: • Solution: Figure 3: PNC-SA Ruiting Zhou Univerisity of Calgary

11. 3. Precoding and BER Analysis • Comparison of the BER performance of PNC-SA and IAC Figure 4: BER performance Ruiting Zhou Univerisity of Calgary

12. 4. Applications and Throughput • General applications of PNC-SA and their throughput: • PNC-SA for Info Exchange • PNC-SA for Multi-Sender Multicast Ruiting Zhou Univerisity of Calgary

13. 4. Applications and Throughput • PNC-SA for Info Exchange: Alice-and-Bob communication Figure 5: PNC-SA with three antennas per node Ruiting Zhou Univerisity of Calgary

14. 4. Applications and Throughput • PNC-SA for Info Exchange • PNC-SA: 6 packets in 2 time slots • Digital network coding: 3 time slots, No coding: 4 time slots Figure 6: Packet-level throughput for information exchange Ruiting Zhou Univerisity of Calgary

15. 4. Applications and Throughput • PNC-SA for Multi-Sender Multicast • PNC-SA: 6 packets in 4 time slots Figure 7: Multicast from top layer to bottom layer Ruiting Zhou Univerisity of Calgary

16. 4. Applications and Throughput • Digital network coding: 5 time slots • Straightforward multicast scheme without coding: 7 time slots Figure 8: Packet-level throughput for multicast Ruiting Zhou Univerisity of Calgary

17. 5. Conclusion • PNC-SA, SA coupled with PNC, can open new design spaces for routing in MIMO wireless networks • Study the optimal precoding and BER performance • Demonstrate the general applications Ruiting Zhou Univerisity of Calgary

18. Thanks! • Questions? Ruiting Zhou Univerisity of Calgary