Fair Resource Allocation in OFDMA Two-Hop Cooperative Relaying Cellular Networks

Joint bit allocation، relay selection and subcarrier assignment are critical for achieving full benefits of OFDM-based cooperative relay networks. In this paper، first such a problem is studied in a dual hop OFDMA cooperative network consisting in multi source nodes، multiple decode-and-forward (DF) relays and a single destination node. The aim is to minimize overall transmission power under the bit-error-rate (BER) and data rate constraints. However، the optimal solution to the optimization problem is computationally complex to obtain and may be unfair. Assuming knowledge of the instantaneous channel gains for all links in the entire network، an iterative three-step resource allocation algorithm with low complexity is proposed. It performs the privileged user selection based on fairness criterion first، and then allocates subcarrier-relay with the given constraints. Finally، power and bit are assigned to the selected subcarriers based on the water-filling algorithm. In order to guarantee the fairness of users، several fairness criteria are also proposed to provide attractive trade-offs between network performance (i. e. overall transmission power، average network lifetime and average outage probability) and fairness to all users. Numerical studies are conducted to evaluate the performance of the proposed algorithm in two practical scenarios. Simulation results show that the proposed allocation algorithm achieves an efficient trade-off between network performance and fairness among users.