PROJECT DESCRIPTION, MOTIVATION, & RELATED WORK
Wireless ad-hoc networks consist of a number of terminals communicating with each other on a peer-to-peer basis without the assistance of wired network or planned infrastructure. The capacity of such wireless networks is limited both by the interference between different transmissions and by the impairments of the wireless channel, such as fading.

This proposal suggests using cooperative diversity to overcome the limitations of wireless networks. In cooperative diversity, several terminals form a kind of coalition to assist each other with the transmission of their messages. The sources jointly act like a multi-antenna transmit array, and the destinations act like a multi-antenna receive array through interchange of messages. There are three advantages from this: diversity, since different paths might fade independently, a power gain through beamforming, and interference mitigation through cooperation on messages transmission.

The gain from cooperative diversity is both an increase in rate, measured for example by ergodic (average) capacity, and diversity, measured for example by outage or outage capacity. Preliminary results already show very large gains while still hinting at the further considerable gains that can be obtained by optimum signaling.

The methodology of the proposed research is to start by thoroughly analyzing simple networks in a variety of channel conditions and network conditions. The networks considered initially are the 3-terminal relay network and the 4-terminal cooperative diversity network. The variables include slow and fast fading, duplexing (full duplex or time-division duplex) and buffering capabilities of terminals, and delay. The results will then be extended to multi-relay networks, multiuser relay networks, and larger cooperative diversity networks.

REFERENCES:

X. Wang and A. Høst-Madsen: “Group-Blind Multiuser Detection for Uplink CDMA,” IEEE Jour. Selected Areas in Communications,” Vol. 17, No. 11, Nov. 1999, pp. 1971-1984.

P. Spasojevic, X. Wang, and A. Høst-Madsen: “Non-linear Group-Blind Multiuser Detection,” IEEE Trans. Communications, vol. 49, no. 9, pp. 1631-1641, Sept. 2001.