Dedicated-Relay vs. User Cooperation in Time-Duplexed Multiaccess Networks

The performance of user cooperation that results when users forward packets for each other in a multiaccess network is compared to that of dedicated-relay cooperation which results from using a dedicated wireless relay when the users do not cooperate. Using the total transmit and processing power consumed at all nodes as a cost metric, the outage probabilities achieved by dynamic decode-and-forward (DDF) and amplify-and-forward (AF) are compared for the two networks. A geometry-inclusive high signal-to-noise ratio (SNR) outage analysis in conjunction with area-averaged numerical simulations shows that in a K-user time-duplexed multiaccess network, user and dedicated-relay cooperation achieve a maximum diversity per user of K and 2, respectively, under both DDF and AF. However, when accounting for energy costs of processing and communication, dedicated-relay cooperation can be more energy efficient than user cooperation, i.e., dedicated-relay cooperation achieves coding (SNR) gains, particularly in the low SNR regime, that override the diversity advantage of user cooperation.