On the Capacity of Relay-Selection Cooperative-Diversity Networks under Adaptive Transmission

In this paper, the use of adaptive source transmission with amplify-and-forward best relaying selection scheme is proposed. Three different adaptive techniques are considered: (i) optimal simultaneous power and rate adaptation; (ii) constant power with optimal rate adaptation; (iii) channel inversion with fixed rate. The capacity upper bounds of these adaptive protocols are derived for the relay-selection amplify-and-forward cooperative network over independent and identical (i.i.d) and independent and non-identical (i.n.d) Rayleigh fading channels. The capacity analysis is based on an upper bound on the effective received signal-to-noise ratio (SNR). It is shown that at high SNR the optimal simultaneous power and rate adaptation and the optimal rate adaptation with constant power provide roughly the same capacity. Channel inversion is shown to suffer from a deterioration in capacity relative to the other adaptive techniques.