Outage performance of cooperative relaying with fixed and best-selected mobile relays over non-identically distributed links

In multi-relay cooperative networks, selecting the best relay to cooperate is known to be spectrally efficient, provided that perfect channel state information (CSI) is available for relay selection. When relays are mobile, the time-varying nature of fading channels renders the provision of accurate CSI challenging and significantly degrades the performance of best relay selection. In this paper, the joint deployment of dedicated relay station (DRS) and mobile relay stations (MRSs) is considered, whereby the MRS selected based on CSI and the stationary DRS simultaneously forward the overheard signal to the destination within the total power constraint. Closed-form expressions for exact and asymptotic outage probability over non-identically distributed links are derived, and comparisons with related schemes are conducted to demonstrate the merits of the proposed scheme.