Research On Secure Energy Efficiency Of Millimeter-Wave Massive MIMO-NOMA System

Recently,millimeter wave(mm Wave)massive multiple input multiple output(MIMO)non-orthogonal multiple access(NOMA)system is regarded as one of the promising technologies in the future beyond 5th generation mobile communication technology(B5G)and 6th generation mobile communication technology(6G)communication network due to its ability to provide higher system capacity and user fairness.However,massive antennas bring huge energy loss.Therefore,the energy efficiency of millimeter wave system is one of the urgent problems to be solved in the future communication network.In addition,due to the openness of wireless communication transmission,the secure transmission of communication networks with massive access devices will face greater challenges in the future.Therefore,in order to achieve a better balance between secure communication and green communication in the mm Wave network,secure energy efficiency(SEE)research is of great significance.Based on the Internet of Things with massive wireless devices and satellite terrestrial integrated network(STIN),secure spectrum efficiency(SSE)and SEE maximization of mm Wave MIMO-NOMA system is studied.Aiming at the new application scenarios,new system models and optimization problems are constructed,and corresponding solutions are proposed.This motivates our thesis.1.Aiming at the security problem of mm Wave MIMO-NOMA system with eavesdroppers(Eve),a multi-user system model using NOMA technology is constructed.And a SSE maximization problem is formed under transmitting power constraints.In order to improve system security and reduce the complexity of solution,the user clustering and power allocation are divided into two stages to optimize.Firstly,a security-based user clustering scheme is proposed to make the generated beam avoid Eve and increase the coverage of legitimate users(LRs).Secondly,for the non-convex security rate maximization problem,a power allocation algorithm based on SCA is proposed to obtain the feasible solution.The simulation results show that the proposed user clustering scheme can better suppress the eavesdropping rate and improve the system security.And compared with conventional digital precoding,the hybrid precoding scheme S improve SEE by up to 60% at the same security rate.Meanwhile,NOMA system based on hybrid precoding has higher SSE and SEE than OMA system.2.Considering simultaneous wireless information and power transfer(SWIPT)technology can provide significant energy saving potential for the system,and aiming at the problem of low SEE for mm Wave MIMO-NOMA system,a system model combined with SWIPT was constructed.Under the constraints of transmitting power and energy harvesting,a SEE maximization problem is formed.In order to obtain the feasible solution,a joint optimization algorithm for power allocation and power splitting based on BI-section is proposed.Considering the computational complexity,an algorithm for power allocation and power splitting based on update iteration is proposed too.Simulation results compare the convergence of the two algorithms.The relationship between SSE and SEE is also verified,if only the improvement of SSE is pursued,the SEE of the system will decrease sharply.Moreover,when the power limit reaches a certain threshold,the increase of the SSE cannot compensate the power consumption,and the SEE does not increase with the power limit.Meanwhile,it is verified that under the same transmitting power constraints,the SEE of the hybrid precoding scheme is improved by more than 50% compared with the conventional digital precoding scheme.3.Considering the future integration of satellite network and terrestrial network,the SEE is introduced into the evaluation index of mm Wave MIMO-NOMA STIN.A system model in which primary satellite network and secondary terrestrial network share the same millimeter wave frequency band is constructed.In order to reduce the interference from base station to earth station,a new user clustering scheme based on suppression of co-frequency interference is proposed.Aiming at the SEE maximization problem,a joint optimization algorithm of power allocation and power splitting based on S-Procedure was proposed under the condition of imperfect Eve channel state information(CSI).The simulation results show that the interference of earth station is suppressed by the improved user clustering scheme.Compared with conventional digital precoding,full-connected hybrid precoding achieves up to 30%SEE improvement with less than 3% SSE loss.Under the same power constraints,the SEE of sub-connected hybrid precoding are at least 40% higher than that of conventional digital precoding.