Cooperative Subcarrier Allocation for an OFDM Relaying System with Grouped Users

In this article, the problem of downlink subcarrier allocation in a cooperative wireless multiuser OFDM system is investigated. We consider a single-cell where all the users are paired in cooperative groups. The mobile users in each group amplify and forward their partner’s data stream using a time division protocol. Based on the capacity contribution from the relaying terminal, a new parameter called cooperation coefficient is introduced as a function of the relaying subchannel. This parameter is used to modify the objective parameter of the subcarrier allocation procedure. Fairness-oriented and throughput-oriented algorithms are selected from the literature to test the proposed technique. Both algorithms are modified to employ the mean of cooperation coefficient in the objective parameter of the subcarrier allocation procedure and shown to have a better total throughput without any sacrifice. Using the mean of cooperation coefficient eliminates the need for the feedback of the relaying channel to the base station. It is shown that by using the mean value of the cooperation coefficient, instead of its instantaneous value, throughput of the system would still improve compared to the non-cooperative case. Using the mean of cooperation coefficient leads to an implementable cooperative subcarrier allocation algorithm.