First are determined which relays are available between at least one source and at least one destination, and from them are selected a subset of those relays for an activation interval under a constraint of equal transmit energy per selected relay across the activation interval. A matrix is formed, using CSI received from the relays, to evaluate each effective channel between source and destination that goes through each of the relays, including multi-relay hops, and the relays are selected from that matrix. Utility of source-relay pairing is evaluated in view of the relay-destination channel and the pairing enables relays to multiplex multiple sources where feasible.