Research On Energy-efficient Resource Allocation Scheme In NOMA System

In recent years,due to the rapid development of the mobile Internet and the Internet of Things,the requirements for data transmission by individuals and enterprises have grown exponentially.The fourth-generation mobile communication system is gradually unable to meet the growing business needs.The research of the fifth-generation communication system becomes the key to solve these issues.As one of the key technologies of the fifth-generation communication system,non-orthogonal multiple access technology can achieve higher spectrum efficiency,enable large-scale user access,and increase system capacity,but at the same time,it will also bring huge energy consumption,which goes against the idea of green communication.Therefore,this thesis studies the resource allocation of non-orthogonal multiple access systems from the perspective of energy efficiency.Firstly,the energy-efficient power allocation scheme of multi-carrier non-orthogonal multiple access system is studied.The problem of maximizing energy efficiency of multi-carrier non-orthogonal multiple access system is established with the minimum rate constraint and maximum transmit power constraint.We decompose inner sub-channel power allocation and inter sub-channel power allocation from each other.First,the power allocation on multi-user in each sub-channel is studied and we obtain the optimal closed-form solution of the power allocation coefficient,which maximizes the energy efficiency of each sub-channel.Then,a novel power allocation algorithm across sub-channels is proposed to further maximize the total energy efficiency of the system.Since the original optimization problem is non-convex,a sequential convex approximation method is introduced to find a sub-optimal solution of the non-convex one.Secondly,the energy-efficient resource allocation scheme of the multiple-input multiple-output non-orthogonal multiple access system is studied.We conduct research from two aspects: user grouping and power allocation.To ensure the effectiveness of the non-orthogonal multiple access scheme,we propose a user grouping algorithm based on the equivalent channel gain of each user.In order to maximize the energy efficiency of the system,we study the power allocation problem of the system.Since the original optimization problem has a non-convex fractional form,we cannot solve it directly,so we resort to the sequential convex approximation method to transform the original problem into a standard fractional programming problem.Then we propose an energy-efficient power allocation algorithm based on the fractional programming theory and obtain a sub-optimal solution for the original power allocation problem,which improves the energy efficiency of the system.Numerical results verify the superiority of the algorithm we proposed.