Ergodic and Outage Capacity Analysis of Cooperative Diversity Systems under Rayleigh Fading Channels

In this paper, assuming the channel state information (CSI) is only known at the receivers, the ergodic and outage capacity of cooperative diversity systems with an arbitrary number of half-duplex relays are analyzed under independently not necessarily identically distributed Rayleigh fading channels. Approximated closed-form analytical expressions for the calculation of ergodic and outage capacity are derived for both the amplify-and-forward (AF) protocol and decode-and-forward (DF) protocol. Numerical results show that all the derived analytical expressions are very tight and are valid for the evaluations of the ergodic and outage capacity with arbitrary number of relays and in any practical SNR regions. Our study shows that with low SNR, AF offers higher ergodic and outage capacity than the DF protocol while with high SNR, DF provides higher capacity performance.