A Cluster-Based Multiuser Cooperative Network

A novel cluster-based coherent multi-user (MU) relaying system is proposed, where a number of source/destination pairs communicate concurrently over the same physical channel and a set of amplify-and-forward relays assist them. A secondary short-range wireless system with single/multi-hop unicast or broadcast ability is considered for the channel state information (CSI) dissemination. To reduce the CSI dissemination overhead, the relays are grouped in several independent clusters. Distributed diversity gain is attained at the destinations by applying phase rotations between clusters. The CSI dissemination is analyzed thoroughly, and compared with that of previous works on MU relaying. It is shown that for a given number of clusters and relays, the most uniform distribution of relays to clusters is optimum to minimize the CSI exchange traffic overhead and transmit energy consumption for CSI dissemination; besides it maximizes the average achievable rate for source/destination links. Furthermore, a new solution for a maxmin fairness based relay gain allocation is proposed and formulated as a semidefinite program.