Cooperative relay networks using rateless codes

1. A method for communicating information in a wireless cooperative relay network of nodes, the nodes including a source, a set of relays, and a destination, comprising the steps of:

encoding a code word as a data stream using a rateless code;

broadcasting, from a source, the data stream;

receiving, in each relay of a set of relays, the data stream;

decoding, in each relay, the received data stream to recover the code word;

reencoding, in each relay, the recovered code word as the data stream with the rateless code;

transmitting, from each relay to a destination, the reencoded data stream;

receiving, in the destination, the reencoded data streams; and

decoding, in the destination, the reencoded data streams to recover the code word.

2. The method of claim 1 , further comprising:

encoding and reencoding the code word using a spreading code.

3. The method of claim 2 , in which each relay uses a different rateless code and a different spreading code.

4. The method of claim 2 , in which each relay uses a different rateless code and the destination uses multi-user detection to distinguish the different rateless codes.

5. The method of claim 1 , in which the code word is an arbitrary accumulation of bits.

6. The method of claim 1 , in which the data stream is broadcast as packets.

7. The method of claim 1 , further comprising:

transmitting, from each relay to the source, an acknowledgement, after the code word has been recovered.

8. The method of claim 7 , further comprising:

terminating the broadcasting after a predetermined number of acknowledgements have been received by the source.

9. The method of claim 1 , in which each relay uses the same rateless code for the reencoding as the source used for the encoding.

10. The method of claim 1 , further comprising:

broadcasting, from the destination, a signal to terminate the transmitting, as soon as the destination has recovered the code word.

11. The method of claim 1 , in which the set of relays transmit the reencoded data stream after all of the relays have recovered the code word.

12. The method of claim 1 , in which each relay starts transmitting the reencoded data stream as soon as the relay has recovered the code word, and further comprising:

receiving, in other relays of the set of relays, the reencoded data stream and the data stream broadcast by the source, and decoding the broadcast data stream and the reencoded data stream to recover the code word.

13. The method of claim 1 , in which the source terminates the transmitting as soon as all of the relays are transmitting.

14. The method of claim 1 , in which intermediate relay nodes in a multi-hop relay network are intermediate destinations, and further comprising:

broadcasting, from the source to the intermediate destinations, the data stream; and

forwarding, from the intermediate destinations to the destination.

15. The method of claim 1 , in which each relay uses a different rateless code and a different spreading code, and each relay performs mutual information accumulation.

16. The method of claim 1 , in which each relay uses a different rateless code and the destination uses multi-user detection to distinguish the different rateless codes, and further comprising:

accumulating mutual information at each relay and the destination.

17. A system for communicating information in a wireless cooperative relay network of nodes, the nodes including a source, a set of relays, and a destination, comprising the steps of:

means for encoding a code word as a data stream using a rateless code;

a source configured to broadcast the data stream;

a set of relays, each relay configured to receive and decode the data stream to recover the code word, and further configured to reencode and transmit the recovered code word as the data stream with the rateless code; and

a destination configured to receive and decode the reencoded data streams to recover the code word.