A major advantage of cooperative communications is the potential for forming distributed antenna arrays, that is arrays whose elements are not collocated, but carried by independent relaying terminals. This allows for a study and design of cooperative communications under a novel perspective, where the inherent end-to-end paths between the source and destination terminal constitute the multiple branches of a virtual, distributed diversity receiver. As a result, the well-known combining methods used in conventional diversity receivers can be implemented in a distributed fashion, resulting in novel relaying protocols and, generally, in new ways for exploiting the resources available in cooperative relaying setups. This chapter provides an overview of this distributed diversity concept, as well as a performance analysis of the corresponding distributed diversity schemes, with particular emphasis on the analysis of distributed switch-and-stay combining. Further insights regarding the potential of implementing the distributed diversity concept in practical applications are obtained.
Ultra-reliable short message cooperative relaying protocols under Nakagami-m fading