Investigations On Energy Efficiency Optimization Techniques In Wireless Networks

The energy consumption of mobile communication network has been drawing increasing attention.Energy efficiency has become one of the key performance indicators of wireless communication network.For mobile communication systems where spectrum is limited,it is necessary to improve their spectral efficiency.However,in some cases,energy efficiency and spectral efficiency are conflicting.A disproportionate increase in one may lead to a decrease in another.Therefore,the tradeoff between them is a key issue.In this thesis,a brief review of state-of-the-art in related area is given.Then,two algorithms for trading off energy efficiency and spectral efficiency are proposed.In the LTE(Long Term Evolution)multi-cell downlink scenario,a power allocation algorithm aiming to trading off energy efficiency and spectral efficiency is proposed.A single objective optimization problem of the proposed metric is given,and is solved iteratively since the power allocation problem in multi-cell scenario is NP-hard(Non-deteministic Polynomial Hard).The proposed problem is decomposed into two sub-problems as the optimization problem of the transmit power of the base station and the power allocation problem.Transmit power of the base station is firstly renewed through gradient method;then optimal power allocation among users are given based on the given total transmit power of the base station.After that,SINR of users is updated until the power allocation converges.Simulations results show the proposed algorithm effectively tradeoff the energy efficiency and spectral efficiency by adjusting the weighted parameter.In the HetNet(Heterogeneous Network)CoMP(Coordinated multipoint Processing)scenario,resource allocation strategies for simultaneously optimizing energy efficiency and spectral efficiency,considering fairness among users is proposed.The optimization problem is solved iteratively to yield the balancing point of energy efficiency and spectral efficiency.In each iteration,duality taking data rates of users as new variables as constrained conditions to simplify the relation between data rate and power allocation is adopted.Resources in CoMP spectrum and non-CoMP spectrum are allocated respectively.For subcarrier allocation,isolation of subcarrier resources is considered to yield the optimal power allocation among users.Then the optimal subcarrier allocation based on the optimal power allocation is presented.Simulation results show that the algorithm is effective.