Title: Cooperative Turbo-Coded Diversity
Authors: Stephen G. Wilson, Oguz Dogan, Radivoje Zarubica (Poster I, 17)

ABSTRACT

Cooperative diversity methods have recently been advocated for ad hoc sensor networks, and for other mobile wireless applications as well, as a means of providing diversity against link fading, and thereby offering lower power operation, or better system coverage. Sendonaris et al proposed the concept of cooperative diversity, also known as distributed space-time transmission, and subsequent work by Janani et al, Laneman et al, and Zhao, among others, has further developed the protocols and performance for small clusters of cooperating users, normally assuming Rayleigh fading path gains.

In this paper, we propose a simple repetition turbo cooperative diversity method for two cooperating nodes, and show its frame error probability (on 640-bit messages) is within 1 dB of the outage probability at the same rate on the quasi-static Rayleigh channel model. The scheme outperforms the distributed turbo approach of Zhao et al by about 1 dB, albeit with greater complexity required of the relay terminal. As expected, the performance exhibits a slope of -2 on log-log format, consistent with an assumption of independent, identically distributed fading from source to destination and relay to destination. To date, this scheme performs as well as a more general (non-repetition) turbo approach, with lower complexity, though information theory allows a gain of about 0.5 dB when repetition is avoided.