The achievable average rate- outage probability trade off curve in two-hop block fading channels

This paper concerns transmission over a two-hop quasi-static Rayleigh block fading channel in which communication is made through the use of a Decode and Forward (DF) relay. It is assumed that the channel state information (CSI) associated with both hops are only available at the corresponding receivers, while they are unknown to the transmitters. Considering an outage event occurs if the destination can not receive a target rate, the optimal achievable average rate- outage probability tradeoff curve is obtained through the use of a multi-layer code at both hops, termed the broadcast strategy. In order to maximize the average rate, we propose an optimum power allocation scheme of both hops. Numerical results show that the maximum achievable average rate for the specific outage probability is obtained when the threshold layer of both hops are equal.