Research On NOMA-based D2D Network Resource Management

With the development of society,a variety of advanced communication equipment and services continue to emerge.In practical environments,due to limited spectrum resources and complex wireless environments,it is difficult to meet the surge in traffic demand with existing technologies.In order to solve these problems,some wireless communication technologies have emerged at the right moment.For example,in order to improve capacity and spectrum efficiency,non-orthogonal multiple access technology(NOMA)stands out.In order to realize heterogeneous mobile networks,further increase network capacity and enhance user experience.Device-to-device(D2D)communication technology and cooperative relay transmission technology have once again become research hotspots.Although the integration of NOMA technology,D2D communication technology and cooperative relay transmission technology can further improve the system performance,at the same time,these three technologies will bring many complex interferences to the system.Therefore,this thesis mainly studies the resource allocation strategy of NOMA-based D2D communication system and the power allocation problem of NOMA-based D2D cooperative relay transmission communication system.In this thesis,imperfect channel state information(CSI)will be considered in the resource allocation algorithm,which makes the algorithm proposed in the thesis more realistic and effective.Specific research work is as follows:1.First,this thesis discusses the characteristics of NOMA technology,D2D communication technology,and cooperative relay transmission technology.And then the adverse effects of imperfect CSI on the system are summarized.The mathematical model of the imperfect CSI is derived in this thesis.2.After that,this thesis studies the problem of interference that occurs when the NOMA-based D2D network shares cellular resources,and proposes a channel assignment and power allocation scheme for NOMA-based D2D communication system.In the single-cell network scenario,the sum rate of the D2D system is optimized,while considering the fairness factor.In this system,imperfect CSI is fully considered,and the outage probability of the D2D communication link is reduced by proposing a mathematical approximation method.This thesis divides the problem of resource allocation into two sub-problems,and solve the sub-problems step by step through the designed channel allocation algorithm and Lagrange multiplier method.3.In order to further improve the data transmission rate and the service quality of cell-edge users,this thesis combines the cooperative relay transmission technology on the basis of the above two technologies.The power allocation strategy of NOMA-based D2D cooperative relay transmission communication system with imperfect CSI is proposed,which improves the data transmission rate of cell users and considers the fairness factor of the system.In this thesis,a convex approximation method is proposed to decouple this problem,and the Lagrange multiplier method is used to obtain the optimal solution of the power allocation coefficients.