Lifetime maximization in AF cooperative networks with energy-harvesting relays

In this paper, a relay selection method based on the minimum opportunity cost (MOC) is proposed to prolong the lifetime of amplify-and-forward (AF) cooperative networks with multiple radio frequency energy-harvesting (RFEH) relays, where lifetime is defined as the longest period in which outage probability of the network is lower than a predefined threshold. Compared with existing relay selection strategies which take channel state information(CSI), residual energy information(REI) into account, the proposed scheme outperforms others when the outage requirement is stringent. This is because the proposed scheme considers harvested energy information(HEI) additionally. Moreover, since the relay selection strategies require simply local CSI, REI, and HEI, they can be implemented in a distributed manner through opportunistic carrier sensing without extra overhead.