Effect of fading correlation and time delay on the performance of scan and wait combining

This paper investigates the effects of correlated fading and outdated channel estimation on scan and wait combining (SWC) which is an alternative form of switch and examine combining (SEC). With this scheme, the combiner waits for one channel coherence time if all the available diversity paths fail to meet a predetermined minimum quality requirement. The scanning through the available diversity paths followed by waiting is repeated indefinitely until a path with an acceptable quality is found. This paper looks into the average probability of error, delay statistics, and the number of diversity paths estimated per channel access of these SWC diversity systems when correlation and outdated channel estimates are taken into account. Selected numerical examples compare the performance results of SWC with traditional SEC along with the corresponding complexity and delay statistics.