Current Projects• Network Coding File System

– first NC-based data storage prototype– hold the First Workshop on NC and Data Storage in HK (Jul

21-22, 2011)• Physical-Layer Network Coding

– first realization on software radio (USRP)• Wireless Network Coding Applications

– a demo of NC protocol on iPhones• BATched Sparse Code (BATS Code)

– generalization of fountain code– used in conjunction with network coding– Can out perform fountain code in a multihop network

2

Network Coding File System• NCFS: Network-coding-based distributed file system

– Use network coding to speed up repair while preserving fault tolerance of storage

– No intelligence required on storage nodes– Data is transparently striped across nodes. Clients only see a mount drive

`

NCFSproxyclient

storagenodes

/mnt/ncfs

Network

3

Network Coding File System

• Apply network coding in proxy to improve repair throughput

NCFSproxy

storagenodes

C

failednodenew

node

ABC=A+B

A B

NCDS 2011

• First Workshop on Network Coding and Data Storage

• Hosted by INC• Hong Kong, July 21-22, 2011• Free registration• http://www.ncds2011.inc.cuhk.edu.hk/

Nov 2010 Soung Liew, CUHK 5

Traditional Multi-hopping

1 3 2S1 S1

S2 S2

Time slot 1

Time slot 3

Time slot 2

Time slot 4

Transmissions non-overlapping in time

Nov 2010 Soung Liew, CUHK 6

Symbol-Level Network Coding

2 3 1S S S 1 3 2S S S

3 1 2S S S 1 3 2

S1 S2

Time slot 1

Time slot 3

Time slot 2

3 1 2S S S

Node 3 uses one time slot to broadcastTransmissions by nodes 1 and 2 still non-overlapping

Nov 2010 Soung Liew, CUHK 7

Physical-Layer Network Coding

2 3 1S S S 1 3 2S S S

3 1 2S S S 1 3 2

S1 S2

Time slot 1 Time slot 2

3 1 2S S S

Transmissions by nodes 1 and 2 are simultaneous!

Wireless Network Coding Applications

Relay Network with Packet Loss

BATS Code• Network coding at relay (Avalanche) can achieve

network capacity asymptotically.• Network coding at relay destroys the structure of

the fountain code, i.e., fast decoding not possible.

• BATS code, a generalization of fountain code, provides a solution.

• Advantages of BATS code:– achieve network capacity asymptotically– no delay at relay– fast encoding and decoding, like fountain code