Grouping and partner selection in cooperative wireless networks

Various results to date have demonstrated the advantages of one or several relay nodes assisting transmissions in a wireless network. In many practical scenarios, not all nodes in the network are simultaneously involved in every transmission; therefore, protocols are needed to form groups or subsets of nodes for the purposes of cooperation. We consider this problem in the context of regenerative nodes and non-altruistic cooperation (all nodes have data of their own to transmit). For a network-wide diversity advantage, the protocol must provide each transmitting node with enough "partners" that can decode its message with high-enough probability. Assuming that the nodes cannot communicate their control decisions (distributed scenario), and that each node chooses to help n other nodes, we point out a simple, static selection strategy that guarantees diversity n+1 for all transmissions. We then consider centralized control strategies and study the additional gains that arise from a central control, under various amounts of information being available to the central controller.