Inter-session Network Coding in wireless network Long Hai 10/02/2012

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 P2 P3 P1, P2 P2, P3 P1+P2 2P1+3P2 P2+3P3

Example2 A C B CD F A B P1 P2 P1+P2 P2 P1 P2 P3 P4 P1 P4P3 P2 P1+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 C P1 P1+P3 2P1+3P3 P1+3P3

Inter-session Network Coding The gain of inter-session network is from reducing the transmitting slots. (xor coding) A C B CD F A B P1 P2 P1+P2 P1+P2+P3+P4 P1+P2

Side Information (SI) P 1 is called the SI for D, which is –overheard by receivers (D, B) –detected by coding nodes (R)

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

Nonlocal Detection 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.

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

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

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 Full rank

RLC in InteR-session NC (R 2 NC) Source: –Unicast –Batch transmission (maybe) Relay: Coding node –RLC –Multicast –Batch transmission Destination: Decoding node –Overhearing –Batch feedback

The Characters of R 2 NC

The Character of R 2 NC For successful decoding: both n1 and n2 have to receive X+Y NC packets. X+Y: coded packets and overheard packets n1n2 R

The Gain of R 2 NC If we set the gain of R 2 NC as, and let, then R 2 NC is not always effective. The maximal gain of R 2 NC is related to link state.

A Routing Method Using R 2 NC Gain (ETX_MG)

Summary Review of Network Coding An Overhearing Detection Method for DWN : POD –More feasible for dynamic networks Inter-session Network Coding in Lossy Networks –R 2 NC scheme –ETX_MG routing

Thank you for your attention!