Realizing Cooperative Multiuser OFDMA Systems with Subcarrier Resource Allocation

Cooperative multiuser OFDMA is an important technology for current and future wireless communications systems. A critical part of this technology is performing multiuser subcarrier resource allocation and a wide variety of techniques have been suggested that can increase overall throughput, decrease total transmit power or improve other key performance measures. A particular subcarrier resource allocation approach that is of interest in this paper is a method based on nodes that transmit and receive on adjacent OFDM subcarriers simultaneously. This approach has shown significant promise, but its feasibility has not been fully investigated. In particular there will be a performance tradeoff in realistic systems as adjacent subcarriers will not be completely isolated and there will be interference on the receiving subcarriers that are adjacent to those that are transmitting. In this paper we look into the performance of such cooperative OFDMA systems under realistic conditions. We propose a transceiver structure to reduce the interference between transmitting subcarriers and receiving subcarriers. Its performance in terms of signal to interference and noise ratio (SINR) is evaluated by both analysis and simulation and is incorporated into a recently proposed cooperation strategy for OFDMA systems to examine its performance under the realistic structure. It is shown that although the cooperation strategy suffers from performance degradation due to the residual interference between the transmitting and receiving subcarriers, it still outperforms the conventional cooperation schemes.