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

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

3. 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)

4. 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)

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

6. Two-Way Coding (TWC) By Beam-Forming (3/3)
May 2013
Two-Way Coding (TWC) By Beam-Forming (3/3)
Changes to 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 standard.
Zhigang Wen (BUPT)

7. Numerical Examples (1/1)
May 2013
Numerical Examples (1/1)
Channel: 100 random channels with Rayleigh fading.
Monte-Carlo: for each channel, 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)

8. May 2013
Conclusion (1/1)
This presentation propose a two-way coding joint design of pre-coder and decoder for 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)

9. May 2013
Thank You!
Zhigang Wen (BUPT)