Two-Way Coding by Beam-Forming for 802.11 WLAN May 2013 Two-Way Coding by Beam-Forming for 802.11 WLAN Date: 2013-05-16 Authors: Zhigang Wen (BUPT)

May 2013 Abstract This document is to propose a joint beam-forming and receiving design for 802.11 WLAN data exchanging service, which can effectively utilize interference as useful signal. Zhigang Wen (BUPT)

May 2013 Background (1/1) Device to device and wireless relaying are becoming very hot. Data exchanging service is becoming more frequent in WLAN. Co-channel interference strongly limits spectral efficiency. Application Scenarios: Packets exchanging in multi-hop relay. Peer to peer file sharing in WLAN. Communications among smart electrical equipment. 1 2 3 Zhigang Wen (BUPT)

Two-Way Coding (TWC) By Beam-Forming (1/3) May 2013 Two-Way Coding (TWC) By Beam-Forming (1/3) Two-Phase Procedure: First slot: two nodes send their own packets to the relay on the same channel resource simultaneously and thus a collided signal interpreted as a function of the two packets, e.g. xor or other linear/nonlinear combinations, is obtained at the AP side. Second slot: the AP broadcasts the combination and each node is able to detect the other's information using its own packet. From 4 slots to 2 slots for data exchanging. Improve by up to 100% efficiency! Key point: beam-forming and receiving design. Data streams from two-way communication terminals should be aligned to the same direction, while other streams will be adjusted to orthogonal direction for space diversion multiplexing. Zhigang Wen (BUPT)

Two-Way Coding (TWC) By Beam-Forming (2/3) May 2013 Two-Way Coding (TWC) By Beam-Forming (2/3) Changes to 802.11 WLAN PHY Beam-forming at STAs and two-way coding at AP. A Simple System Model. Zhigang Wen (BUPT)

Two-Way Coding (TWC) By Beam-Forming (3/3) May 2013 Two-Way Coding (TWC) By Beam-Forming (3/3) Changes to 802.11 WLAN MAC Create virtual and actual packet queues and several flags. STAs sense the opportunities for two-way coding from the queue. Update the wait-for-TWC flag. If wait-for-TWC flag is true, determine whether to use two-way coding. If the system decides to use TWC, the immediate node schedules to make source nodes transform data simultaneously using two-way beam-forming. The scheme can effectively solve the packet collision problem and makes very small changes to the current 802.11 standard. Zhigang Wen (BUPT)

Numerical Examples (1/1) May 2013 Numerical Examples (1/1) Channel: 100 random channels with Rayleigh fading. Monte-Carlo: for each channel, 10000 transmissions are done with uncorrelated symbols and noise. Noise: AWGN. Path loss: relative distance d=D/R. Modulation: BPSK. Channel Coding: N/A. OFDM: N/A. Channel Estimation: perfect. Time-Slot: uplink phase. NR=4, NT = 2. SIMULATION ASSUMPTIONS Zhigang Wen (BUPT)

May 2013 Conclusion (1/1) This presentation propose a two-way coding joint design of pre-coder and decoder for 802.11 WLAN. It can improve the network flexibility and channel efficiency for WLAN. Proposal 1: Two-way coding technology should be considered for exchanging services. Proposal 2: WLAN PHY and MAC protocol changes are not great and should be made to opportunistically use the TWC.   Zhigang Wen (BUPT)

May 2013 Thank You! Zhigang Wen (BUPT)