Comparison of Cooperative Path Selection Techniques

Relay selection (RS) is the one of the proposed methods in the literature to utilize cooperative diversity. When the source-relay channel information is not available at the destination, the RS technique does not exploit user diversity efficiently. The proposed solution of this problem in the literature is that the relays monitor all channels "end-to-end" and the mobile unit with the highest channel gain informs the destination and other relays. This is called path selection and is not a practical solution, since, each relay mobile unit consumes additional power for monitoring, synchronization and protocol overhead. In this paper, we propose an alternative solution in that each mobile unit quantizes its partial source-relay channel information and transmits to the destination. Since the destination is usually a base station, power consumption and synchronization is not a problem. Proposed method provides important performance gains with a few feedforward bits. New path selection algorithm does not require relay monitoring of all paths, and eliminates synchronization and protocol overhead.