Capacity comparison of opportunistic relaying system with outdated channel information

In this paper, we investigate the impact of outdated channel state information (CSI) on the capacity of an opportunistic relaying system. We derive the analytical expressions of the channel capacity and its associated outage probability of reactive relay selection for four adaptive transmission techniques. Analytical and numerical results show that the rate adaptation policy achieves better performance compared to the sub-optimal channel inversion in the presence of outdated CSI. In addition, design insights and useful observations for relay selection can be deduced from these results, implying that CSI accuracy in the source-relay link plays a significant role in determining the relay selection strategy for given system parameters.