Research On Energy Efficiency Algorithm Of Cooperative NOMA With Hardware Impairments

With the development of wireless communication,1G-4G multiple access appears continuously,which brings great convenience to the society.With the coming of 5G era,new multiple access technology also comes into being.Among them,non-orthogonal multiple access(NOMA)has attracted much attention because it can achieve more user connections and higher spectrum efficiency(SE).The research shows that the combination of cooperative communication and NOMA can effectively improve the SE and energy efficiency(EE),thus realizing green communication.The traditional cooperative NOMA system is usually studied under the ideal hardware condition,while the actual communication nodes suffer from different degrees of hardware impairments(HI),which degrade the system performance.Therefore,under the condition of hardware impairments,this thesis studies the EE of cooperative NOMA system with efficient resource allocation algorithm.Firstly,the energy-efficient of the downlink single-carrier cooperative NOMA system is studied,and the HI at the source node,relay node and user node is fully considered.Under the constraints of the transmission power of the base station and relay and the minimum rate at the user,the EE optimization model is established.Then,the optimization problem is replaced by the Fractional Programming,and based on the Lagrange dual and Dinkelbach method,an internal and external iterative optimization algorithm is proposed to maximize the system EE.Finally,simulation results show that HI will reduce the system EE,and the proposed algorithm has higher EE than the traditional orthogonal multiple access(OMA).Secondly,for downlink cooperative multi-carrier NOMA system,the energy efficienct optimization problem is studied by considering the HI of transceiver.Since the EE optimization problem is a nonlinear hybrid programming problem,the optimization problem is decoupled into two sub problems: user subcarrier matching and power allocation.Then,a user subcarrier two-way matching algorithm is proposed to solve the matching problem.After the user subcarrier matching is completed,the variable substitution and Fractional Programming are used to optimize the resource allocation,and a Quadratic Transform Power Allocation algorithm(QTPA)is proposed,then the EE is maximized through multiple iterations.Finally,simulation results show that the proposed power allocation algorithm can achieve higher EE than fractional transmit power allocation(FTPA)algorithm,equal power allocation(EPA)algorithm and traditional OMA scheme.