Strategy Of Resource Allocation In OFDM-based Two-way Relay Cooperative System

As the key technology in the next generation mobile communication system, wireless relay transmission technology has been widely applying. By using the analog network coding technology, the two-way relay system cost only two slots during the communication process between two users. The spectrum utilization rate will be increased obviously while the two-way relay can also provide diversity gain and better transmission capacity compared with the traditional one-way relay system. Orthogonal frequency division multiplexing(OFDM) can resist the frequency selective fading in high performance and improve the utilization of spectrum effectively, so the combination of two-way relay channel model with OFDM has been getting widely attention of the academic circles. Relay selection、subcarrier pairing and power allocation is the key technology to improve system performance and the system resource utilization.Since the major optimization objective is amplify-and-forward two-way relay system, after a brief introduction of the basic principle of two-way relay model and OFDM, the system capacity is analysed first under the condition of CSI on the AF-TWR system with multiple relay system, then an approximate upper bound on the outage probability is derived and closed form expressions of the average symbol error rate by MPSK modulation is obtained. After that a resource allocation method is proposed to minimize the overall power as the target for OFDM two-way relay system. In order to select the best relay among subcarriers, a relay selection method based on maximing the harmonic average is proposed, then a bit and power allocation method based on Fisher adaptive algorithm is employed according to the optimization principle. Finally, the resource allocation strategy for a multi-relay and multi-user AF OFDM-Based two-way relay system is considered to maximize the system sum rate involved subcarrier assignment and power allocation. The subcarrier-relay assignment strategy is obtained by using the optimal equivalent channel gain, and then a optimal power allocation solution is proposed combining with the gradient iteration method. The simulation results prove the effectiveness of the optimization of resources allocation method.