Power control in decode-and-forward cooperative systems

In this paper, a decode-and-forward cooperative communication system is considered with errors forwarded by relays. Maximum ratio combining is performed at the destination without considering whether the forwarded symbols from the relays are incorrect. We analyze the performance of different transmission power strategies at the relays and the source node. We investigate the optimal transmission power control strategy under a fixed total power constraint. Compared with the conventional transmission power distribution where the source and the relays transmit with the same power, the optimal strategy enables significant performance gain at the destination. With a given target probability of error, large power saving can be obtained at the relays. A near-optimal approximation to achieve the performance of the optimal strategy is also given in the paper.