Research On Energy Efficient Resource Allocation In OFDMA System

The enormous energy consumption of wireless communication systems has aroused widespread concerns throughout the world,and the energy-efficient oriented design for green communications has become a hot research direction. In this thesis,we study the high energy efficient resource allocation strategy in multiuser for orthogonal frequency division multiple access(OFDMA) downlink system. The OFDMA downlink resource allocation algorithm is generally divided into three aspects: Weighted sum rate maximization(WSRmax), weighted sum power minimization(WSPmin) or weighted the ratio of sum rate and sum transmission power maximization. It is shown that more than 50% of voice calls and 70% of data traffic originate from indoors,but about 30% of business and 45% of household users experience poor indoor coverage. Therefore,this thesis propose resource allocation optimization algorithm based on energy efficiency optimal in three scenarios of OFDMA system.In this thesis, Lagrangia n dual decomposition(LDD) algorithm based on energy efficiency optimization for outdoor macrocell downlink OFDMA system with advanced objective function was proposed. The energy-efficient resource allocation problem can be converted into a more tractable convex optimization, and the computational complexity has been greatly reduced. First, the algorithm uses the iterative algorithm to dynamically allocate subcarrier and power, and then conduct the bisection search method to get the optimal energy efficiency. Simulation results show that our proposed algorithm can improve energy efficiency significantly for OFDMA system, and reduce the computational complexity.This thesis introduce a power control technique for downlink transmission in two-tier network MIMO OFDMA system consists of indoor Femtocell base station and outdoor macrocell base stations, considering cell interference and QoS constraint.The technique is an important part of radio resource management,the greater the power, the more serious interference to other base station service users.Simulation results show that the algorithm can effectively improve the energy efficiency of the system and reduce the computational complexity.This thesis propose LDD power allocation algorithm based on optimal ener gy efficiency in downlink OFDMA system for outdoor central macrocell interfered by indoor Femtocell, considering the two major issues of the cross-tier interference and user QoS constraint. The algorithm use LDD method decompose energy efficiency optimize dual problem into several sub-problems to solve separately on each subcarrier, the gradient algorithm is adopt to obtain optimal power allocation scheme,then solve dual variable convergence value by iteration and adjust user power allocation to obtain optimal energy efficiency.