CUHK-SZU Joint Lab on Network Coding Implementation

Network-Coded Multiple Access

Presented by Soung Liew

(Joint Work with Lu Lu, Lizhao You, Shenghao Yang)

Institute of Network Coding

The Chinese University of Hong Kong

March 2014

culogo

Soung Liew, CUHK

1

culogo

March 2014

2

Background on PNC

First proposed in Mobicom 06 [1]

A subfield of Network Coding building up momentum in recentyears:

-Google scholar citations: 1000+ (annual growth ~300)

-A main topic in special journal issues and numerous conferences.

-A main topic in an upcoming IEEE JSAC issue on wireless networkcoding

-Half-day workshop in IEEE WNCN 2013: New Advances for PNC

-Invited talks

[1] S. Zhang, S. C. Liew, P. P. Lam, “Physical-Layer Network Coding,” ACM Mobicom 2006 .

Similar idea in

[2] P. Popovski and H. Yomo, “The anti-packets can increase the achievable throughput of a wireless multi-hop network,”ICC 2006.

Soung Liew, CUHK

culogo

March 2014

Simplest Set-up: Two-Hop LinearNetwork

Two-way Relay Channel (TWRC)

No direct channel between nodes A and B.

Half duplex: nodes cannot transmit and receive at thesame time.

What is the minimum number of time slots neededfor nodes A and B to exchange one packet via relay R?

A

R

B

SA

SB

Soung Liew, CUHK

3

culogo

PNC

March 2014

A

R

B

SA

SB

Time slot 1

Time slot 2

Transmissions by nodes A and B are simultaneous!

Soung Liew, CUHK

4

culogo

March 2014

PNC for Multiple Access(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?

Relay Network

Soung Liew, CUHK

5

Wireless LAN

Access Point

culogo

PNC In Non-Relay Network:Network Coding Multiple Access (NCMA)

Nodes A and B send CA and CB to AP simultaneously

AP tries to decode packets CA , CB, and

March 2014

Soung Liew, CUHK

6

A

AP

B

culogo

PHY-Layer Decoders of NCMA

March 2014

Soft Information (Log Likelihood Ratio: , k=1,2,… )

Soung Liew, CUHK

7

culogo

PHY-layer Bridging

March 2014

Soung Liew, CUHK

8

culogo

Are Lone XOR Packets Useful?

March 2014

Complementary XOR

Lone XOR

Soung Liew, CUHK

9

•Do lone XOR packets have a role to play?

culogo

March 2014

MAC-Layer Erasure Code + PHY-Layer Channel Code

Soung Liew, CUHK

10

culogo

MAC-Layer Bridging with L = 3

March 2014

Soung Liew, CUHK

11

culogo

Experiments: Layout of Indoor Environment for 9 USRPN210 Nodes

Institute of Network Coding (INC)

March 2014

Soung Liew, CUHK

12

culogo

PHY-Layer Packet Decoding Statistics(Balanced Power Case)

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

March 2014

Soung Liew, CUHK

13

culogo

PNC decoding works but MUD doesnot when phases are aligned

March 2014

Soung Liew, CUHK

14

ReceivedSignal

Decode Outcomes

culogo

PNC does add value when phases areseverely misaligned

March 2014

Soung Liew, CUHK

15

Decode Outcomes

ReceivedSignal

culogo

Combination of PNC and MUD is effective whenphases are moderately misaligned

March 2014

Soung Liew, CUHK

16

ReceivedSignal

Decode Outcomes

culogo

March 2014

Soung Liew, CUHK

17

Overall Throughputs of Different Schemes forDifferent SNRs LA = 1.5×LB = 24.

culogo

Pairing Strategies

March 2014

Soung Liew, CUHK

18

Scenario: Four users at locations 2, 3, 4, 5.

How to form pairs?

Pair “strong with weak” rather than “strong with strong and weak with weak”

Strategy 1: pair 2 with 3; 4 with 5

Strategy 2: pair 3 with 4; 2 with 5

12.3dB 9dB 7dB 7.4dB

culogo

Linearly Coupled Codes at MAC Layer

Single-equation System:

March 2014

Soung Liew, CUHK

19

culogo

Linearly Coupled Raptor Codes

Near optimal and availability of fastdecoding

March 2014

Soung Liew, CUHK

20

culogo

Dynamic Equation

March 2014

Soung Liew, CUHK

21

culogo

Degree Optimization Problem

March 2014

Soung Liew, CUHK

22

For some positive integer

culogo

Use SIC at low SNR Regime

Suppose an (N,3) RS code

March 2014

Soung Liew, CUHK

23

SlotIndex

PHY-layerSIC

Cross-layerSIC

Messagedecoding

1

2

3

4

5

culogo

Overall Throughputs of Different Schemes forDifferent SNRs LA = 1.5×LB = 24.

March 2014

Soung Liew, CUHK

24

culogo

NCMA: Conclusion

First venture into non-relay (multiple-access)setting for PNC

PNC may have a role to play in the multipleaccess scenario:

To simplify decoder design

For delivering jumbo messages

Ongoing NCMA Investigations:

Better performance for high and low SNR regime

Investigation of linearly-coupled code for MAC layerof NCMA

March 2014

Soung Liew, CUHK

25

culogo

The End

March 2014

Soung Liew, CUHK

26

culogo

Throughputs of Four User Pairs

March 2014

Soung Liew, CUHK

27

culogo

Overall Throughputs of Different Schemes with RS codeparameter LA = 4, 8, 16, 32, and fixed SNR = 9dB.

March 2014

Soung Liew, CUHK

28

culogo

Throughputs of Nodes A and B, with SNR of Node A fixedat 9.5dB, and SNR of Node B Varied.

March 2014

Soung Liew, CUHK

29

culogo

March 2014

30

Frequency-Domain PNC (FPNC) in GNU Radio testbed,

PNC Implementation: Wireless

Soung Liew, CUHK

$D:\Thesis\slice\picture of usrp\DSC02658.JPG$

A

B

R