| Wireless relays offer benefits such as coverage extension and improving robustness. Selection of relays may provide further benefits. The best relays are selected based on the channel state information. However, due to feedback or scheduling delays, in practise, the relay and/or the source node can have outdated channel state information. This outdated information will cause a performance degradation, and in this thesis its impact on dual-hop relay systems is investigated. The performance of amplify-and-forward (AF) relays under partial relay selection and opportunistic relay selection is analyzed. Both variable gain AF and fixed gain AF schemes are considered. Expressions for the outage probability and the average bit error rate and simplified high signal-to-noise ratio approximations are derived. The effect of parameters such as the number of relays, the rank of chosen relay, and the correlation between the delayed and current channel state information are analyzed. |
