Security analysis of a relay selection system under outdated CSI

For a cooperative communication system in which the feedback delay exists, the channel state information (CSI) of the link at the time of relay selection may be outdated with respect to the time of data transmission. The use of outdated channel state information for the selection of relay node will inevitably affect the reliability of selection. Considering the existence of feedback delay, our paper analyzes two kinds of optimized strategy for relay selection.