Research On The Resource Allocation Algorithm In OFDM Two-Way Relay System

Two-way relaying system has the advantages to improve the spectral efficiency and the coverage area of cell edge; as the OFDM can effectively against the depth fading and achieve high spectral efficiency, it has become one of the key technologies of the 4G wireless networks, so the two-way relaying combination with the OFDM has important research value. In the two-way relaying OFDM network, the reasonable allocation of resources plays a central role to improving system performance, especially subcarrier matching, optimal power allocation and multi-user multi-relay cooperation. This thesis introduces the basic principle of the OFDM and the two-way relaying technology, focusing on researching the resource allocation algorithms in the scenario with single-user single-relay and the multi-user single-relay and multi-user multi-relay.Firstly, a power allocation algorithm with low complexity is proposed for the scenario with single-user single-relay. It gives the sub-carrier pairing method which bases on the sorted channel coefficient. Then this thesis proposes to build a linear power relation between S-R and R-S to simplify the optimization problem from three layers to a layer, so the power allocation problem could obtain the power proportion of between each node and the sub-carrier with low complexity; then under the total power constraint, it employed the Primal-Dual Interior-Point methods to obtain the power allocation of each sub-carrier pair, and finally it allocated the power of each sub-carrier pair to all nodes. Simulation results show that the proposed power allocation strategy can significantly improve the total system rate, and the performance is improved as the number of sub-carrier is increasing.Secondly, a greedy matching algorithm of the rate proportional rough fairness and iterative adjusting power allocation algorithm is proposed for the scenario with the multi-user single-relay. This thesis firstly proposed the greedy matching algorithms of the rate proportional rough fairness; then obtaining the power proportion of between each node and combining the Lagrange dual and interior point method achieve the optimal allocation of power resources; finally, using the "binary search" iterative adjust power allocation among users. Simulation results show that the proposed strategy enhances the overall rate of the system with ensuring the fairness.Finally, a the subcarrier matching and optimal power allocation algorithm of ensuring the lowest rate which users expect is studied for the scenario with a multi-user multi-relay. This thesis considers the subcarrier pairing and the relaying selection strategy and the optimal power allocation and the fairness among users. It firstly proposes the sub-carrier pairing algorithm of meeting the lowest rate which users expect. Then combining the Lagrange dual and sub-gradient algorithm achieve the optimal allocation of power resources; Simulation analysis show that the proposed algorithm not only get a good resource utilization, but also achieve high fairness.