Resource Allocation for Dynamic Intra-Cell Subcarrier Reuse in Cooperative OFDMA Wireless Networks

Resource reuse schemes in relay-enhanced cooperative orthogonal frequency-division multiple access (OFDMA) networks have been well studied in the literature from an interference mitigation perspective and with cell-partitioning being the basis. In this paper however, we study dynamic intra-cell subcarrier reuse in cooperative OFDMA networks in which the users are allowed to share any subcarrier in the relay links provided that the resultant intra-cell interference is managed; an option not available in non-cooperative networks. Specifically, when the target data-rates of the users are not reachable in a conventional cooperative OFDMA network, dynamic intra-cell subcarrier reuse enables the users to achieve their target data-rates, even when the number of users surpasses the number of subcarriers. We formally define the problem of maximizing the system sum-rate subject to per node power and target data-rate constraints in a cooperative OFDMA single-cell network in which subcarriers are allowed to be reused in the relay links. After analyzing the problem in the dual domain and deriving the performance bounds, we propose a suboptimal resource allocation algorithm where subcarriers and links (relay and/or direct) are assigned to the users. Simulation results show that by employing our resource allocation algorithm, the system sum-rate and the outage ratio are significantly improved, specially in an overpopulated network.