Outage probability and adaptive power allocation in wireless cooperative communications

In this paper we develop an adaptive power allocation algorithm to minimize the outage probability in a two-hop single-relay wireless cooperative communication system under the average transmit power constraint. The adaptation is carried out in the time domain according to the channel state information (CSI), so a priori information of the channel is assumed. We analyze the outage performance in two different cooperation modes, i.e., amplify-and-forward (AF) and decode-and-forward (DF). We also study the impact of spectral efficiency and distance between nodes on outage performance. To facilitate the comparison, the outage performance of direct transmission is also analyzed as a baseline. Numerical results show that compared with fixed power allocation, adaptive power allocation has much better outage performance.