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

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 Calgary2/18

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 Calgary3/18

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 Calgary4/18

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 Calgary5/18

2. PNC-SA Scheme Introduction to Digital Network Coding Physical-Layer Network Coding Physical layer Network Coding with Signal Alignment Scheme Ruiting Zhou Univerisity of Calgary6/18

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 Calgary7/18

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  BPSK maps from{-1, 1} to {0, 1}  PNC demodulation maps from {+2, 0, -2} to {0, 1} Ruiting Zhou Univerisity of Calgary8/18

2. PNC-SA Scheme Physical layer Network Coding with Signal Alignment (PNC-SA) Align simultaneous transmissions from multiple MIMO senders. Figure 3: PNC-SA Ruiting Zhou Univerisity of Calgary9/18

3. Precoding and BER Analysis Precoding — Alignment constraint: Solution: Figure 3: PNC-SA Ruiting Zhou Univerisity of Calgary10/18

3. Precoding and BER Analysis Comparison of the BER performance of PNC-SA and IAC Figure 4: BER performance Ruiting Zhou Univerisity of Calgary11/18

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 Calgary12/18

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 Calgary13/18

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 Calgary14/18

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 Calgary15/18

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 Calgary16/18

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 Calgary17/18

Thanks! Questions? Ruiting Zhou Univerisity of Calgary18/18