Inter-session Network Coding in wireless network

Long Hai10/02/2012

Outline

• Network Coding

• Intra- and Inter-session Network Coding

• My Main Work– Overhearing Detection for Inter-session

Network Coding in Dynamical Network– Inter-session Network Coding in Lossy

Network

What is Network Coding?

• Network coding is a technique where, instead of simply relaying the packets of information they receive, the nodes of a network will take several packets and combine them together for transmission.

Example1

A

B1

B2

B3

C

P1

P1

P1

P2

P2

P2

P3

P3

P3

P1, P2

P1, P2

P2, P3

P1+P2

2P1+3P2

P2+3P3

332

221

121

3

32

B

B

B

PPP

PPP

PPP

Example2

A

C

B

CD

F

A BP1P1

P2

P1+P2P1+P2

P2

P1

P1P1

P2

P2

P2

P3

P3

P3

P4

P4P4

P1

P4 P3

P2

P1+P2+P3+P4P1+P2+P3+P4P1+P2+P3+P4P1+P2+P3+P4

Outline

• Network Coding

• Intra- and Inter-session Network Coding

• My Main Work– Overhearing Detection for Inter-session

Network Coding in Dynamical Network– Inter-session Network Coding in Lossy

Network

Intra-session Network Coding

• The gain of intra-session network coding is from decreasing the retransmission times. (linear coding)

A

B1

B2

B3

CP1

P1+P3

2P1+3P3

P1+3P3

331

231

121

3

32

B

B

B

PPP

PPP

PPP

Inter-session Network Coding

• The gain of inter-session network is from reducing the transmitting slots. (xor coding)

A

C

B

CD

F

A BP1

P2

P1+P2P1+P2+P3+P4

P1+P2

Side Information (SI)

• P1 is called the SI for D, which is– overheard by receivers

(D, B)– detected by coding

nodes (R)

P1 P2

P1⊕P2

A

R

B

C

D

Outline

• Network Coding

• Intra- and Inter-session Network Coding

• My Main Work– Overhearing Detection for Inter-session

Network Coding in Dynamical Network– Inter-session Network Coding in Lossy

Network

The Overhearing Detection (Local vs. Nonlocal) in Dynamical Network

• Local Detection: Cope methods (Katti, 2006)– Opportunistic Listening– Learning Neighbor State

P1 P2

P1⊕P2

A

R

B

C

D

Nonlocal Detection

A

G

B

E

F

C

D

P1

P2

P1⊕P2

P1⊕P2

P1

P1 P2

Flow 1: A->D

Flow 2: E->G

• Nonlocal Detection: Dcar method (Jilin Le, 2008)– Routing Overhearing + Learning Neighbor State

Relative Merits of Cope and Dcar

• More coding opportunities by Dcar than by Cope

• Dcar is not robust.

Flow F1

Flow F21 4

6

7

3

2

5

1

4

67

3

2

5

Packet Overhearing Detection

• The SI is piggybacked by every data packet.

– Dcar: Routing control packet

– Cope: Report control packet

• It is – a NLD method.

– more coding opportunities than Cope.

– more robust than Dcar.

An example

A

D

J

C

G

B

H

E

K

I

F

P1 route

P2 route

Packet

}Overheard informationC D

BA

P1

C D

BA

P1

HJI

P2

C DA B

KE G

P1

P1

P2

H GJI

P2

Simulation

• Two dynamic scenarios: bloat, open

The TPT of dynamic scenarios

Outline

• Network Coding

• Intra- and Inter-session Network Coding

• My Main Work– Overhearing Detection for Inter-session

Network Coding in Dynamical Network– Inter-session Network Coding in Lossy

Network

Inter-session Network Coding in Lossy Network

• Unreliable Overhearing Problem– Irresponsible transmission: no ACK– Free ride: no RTS/CTS

• Overhearing Feedback Problem– Periodical report: bandwidth profligacy– Learning neighbor state: UOP

P1 P2

P1⊕P2

A

R

B

C

D

Linear coding

• Linear Coding– Xe: output– Xg: input– Kg,e: coding coefficient

• Random Linear Coding (Tracey Ho, 2006)– Random coding coefficient– Lemma 1:

• On an acyclic network, the successful decoding probability of the network is at least where |F|>δ

Tgege XKX ,

EF )1(

Full rank

RLC in InteR-session NC (R2NC)

• Source: – Unicast – Batch transmission

(maybe)

• Relay: Coding node– RLC– Multicast– Batch transmission

• Destination: Decoding node– Overhearing– Batch feedback

The Characters of R2NC

The Character of R2NC

• For successful decoding: both n1 and n2 have to receive X+Y

NC packets.• X+Y: coded packets and

overheard packets

X

yX r

YOXT

)1(

YOX

Xr Yr

n1 n2

R YXO

YXx

YXx

rTXOY

rTXOY

)1(

)1(

The Gain of R2NC

• If we set the gain of R2NC as , and let , then

• R2NC is not always effective.• The maximal gain of R2NC is related to link

state.

C

C

T

TTG

te

etr

et

erG

x

yt

y

yt

1

,

Oer

rr

Y

Xt

Y

Xt 1,,

A Routing Method Using R2NC Gain (ETX_MG)

1,,0.5

,.4

),(.3

.2

.1

..1

min

,,

1

,

,,

,

yxyixi

yx

yx

te

etry

ytii

yixii

i

i

eerr

fYfX

ffFi

et

erAG

r

Y

r

XT

tsG

T

x

yti

Summary

• Review of Network Coding

• An Overhearing Detection Method for DWN : POD– More feasible for dynamic networks

• Inter-session Network Coding in Lossy Networks– R2NC scheme – ETX_MG routing

Thank you for your attention!