Research On Resource Allocation Algorithm Based On OFDM Two-way Relay Network System

Two-way relay technology has attracted much attention as a key technology in wireless communication systems.It has the advantage of improving the coverage of wireless communication system and solving the characteristics of traditional one-way relay spectrum inefficiency.At the same time,orthogonal frequency-division multiplexing(OFDM)is known as a powerful technique to combat frequency selective fading channels and,it can achieve high data rates over broadband wireless networks when combined with relay architecture.On the other hand,the design of efficient wireless resource allocation schemes have been recognized as an important measure to fully exploit the potential of modern wireless communication systems.In the OFDM two-way relay networks,the combination of OFDM technique with two-way relay can further improve the overall system performance while also renders optimal resource allocation problem more crucial and challenging.Consequently,it is valuable to investigate the resource problem in the OFDM two-way relay networks.The main research contents and results are as follows:(1)Aiming at the problem of resource allocation in single-user OFDM two-way relay network system,and considering the complexity of system computation,the step strategy is applied in this paper to solve the optimization problems.First,the equivalent channel gain function related to the channel gain of the two slots phase is derived with the high signal-to-noise ratio of the system.Based on the channel gain function,a sub-carrier pairing algorithm is proposed with O(N2)computational complexity.Then the power of the system is optimized on the basis of the sub-carrier pairing,and a node power optimization model is need to be established for the specific sub-carrier pair.According to this model,we can calculate the power of each node in the system.Finally,the power of each sub-carrier is calculated based on the principle of water-filling algorithm.Experimental results show that the proposed algorithm can effectively enhance the system capacity.(2)Considering the multi-user situation in the actual communication environment,due to the multi-user resource competition problems,the problem of sub-carrier allocation and power optimization is considered in this paper.In order to balance the total capacity of the system and the fairness between users,a joint resource allocation strategy based on proportional fairness is proposed.It is difficult to solve the optimization model of the joint resource optimization problem directly.Considering the complexity of the system calculation,a simplified model is achieved by the step solving method.Firstly,the sub-carrier of the system is allocated according to the optimal sub-carrier allocation criteria,then we introduce the fairness threshold,and iteratively adjust the sub-carrier until the the fairness requirement of the system is achieved.Based on the allocated sub-carriers,the power of the sub-carrier can be solved by Lagrange dual theory and sub-gradient algorithm.Then adjusting the power of the user pair with the largest proportion rate under the limit of the system fairness threshold.The simulation results show that the proposed algorithm can not only improve the total capacity of the system,but also can dynamically adjust the trade-off between the fairness of the system and the system capacity according to the requirements of the user.