Performance analysis of multi-path relay channels with source power adaptation

A cooperative multi-path relay channel (MPRC) with multiple decode-and-forward relay terminals is considered in this paper. In order to enhance the system reliability, the source is encouraged to transmit at a higher power such that more relays can successfully decode the source symbol. This, however, may lead to unnecessary energy waste. For reliable symbol delivery while improving the system energy efficiency, we propose power adaptation schemes at the source and relays depending on the availability of channel state information (CSI). In order to minimize the energy consumption for successfully delivering a source symbol, both the source and relay adaptively select a suitable transmit power from a finite set of discrete power levels. The outage probability and energy efficiency of the cooperative MPRC are analyzed and simulated. Simulation results demonstrate a tradeoff between the outage performance and energy efficiency. Under the same outage performance, the system energy efficiency can be significantly improved by the proposed power adaptation schemes compared to a benchmark case with blind source transmissions.