Research On Multi-User Interference Management Technology Based On Interference Alignment And Non-Orthogonal Multiple Access In Wireless Networks

With the rapid development of wireless communication networks,scarce spectrum resources are decreasing day by day,while the number of user equipments is growing by leaps and bounds,and the requirements for the data rate,system capacity,transmission delay and the connective feature of wireless communication networks by people is becoming more stringent.The next generation mobile communication network has to face many challenges.In addition,its various complicated application scenarios and highly intensive network deployment make the interference problem more and more severe and also prominent,which has become the key to restrict the performance of the networks.Traditional interference management technology and ideas can not follow the rapid development of wireless communications.In the future opportunities and challenges,there is an urgent need for advanced interference management technology to change these severe situations.In view of this,based on interference alignment(IA)and non-orthogonal multiple access(NOMA)technologies,combined with opportunistic communication,device-to-device(D2D)communication and full duplex(FD)communication,this paper studies the technical scheme of multi-user interference management in different scenarios of wireless communication networks.Firstly,in the two-cell uplink multiple-input multiple-output(MIMO)interference multiple access channel(IMAC),from the perspective of desired signal,in two scenarios of perfect feedback and limited feedback of channel information,considering the alignment of interference signals and the enhancement of the power of desired signal,the iterative maximum-power IA(MP-IA)and maximum signal to interference and noise ratio IA(MSINR-IA)algorithms are proposed,and the provable convergence and complexity analysis are provided.The proposed iterative algorithms not only effectively suppress the interference at each receiver,but also further enhance the power or signal-to interference and noise ratio(SINR)of the received desired signal.Simulation results show that compared with the traditional IA algorithms,the proposed algorithms not only improve the average sum rate of the system,but also improve the BER performance.Second,in the -cell single input multiple output(SIMO)interference channel(IC),a FD MIMO Relay is selected to assist the transmission so as to reduce the burden of the transmitters.New IA algorithms are proposed in perfect channel state information(CSI)and imperfect CSI scenarios,which respectively termed iterative optimized reference vector IA(IORV-IA)and robust mean square error(MSE)algorithm.Different from the traditional IA schemes,the proposed IORV-IA not only achieves IA at each receiver,but also iteratively optimizes the IA reference vector to avoid the power reduction of the received desired signal.The MSE based robust algorithm aims at minimizing the sum of MSE of the users in the worst case,iteratively optimizing the relay processing matrix and interference suppression vector.Simulation results show that,compared with the traditional IA schemes,the proposed two algorithms have outstanding advantages in the number of relay antennas,sum rate performance and BER performance,greatly improve the system performance.Then,the OIA in cellular wireless networks is investigated.In K-cell MIMO-IMAC and three-cell MIMO interference broadcast channel(IFBC),considering the effective power of the received desired signal and the leakage of interference coming from transmitter,precoding matrix and user scheduling scheme are designed.Then,signal-to leakage of interference ratio OIA(SLIR-OIA)scheme is proposed in the uplink,SLIR user selection(SLIR-US)scheme as well as mean square error based OIA(MSE-OIA)scheme are proposed in the downlink.Simulation results show that the sum rate and BER performance of the proposed SLIR-OIA scheme are better than those of the traditional OIA schemes in both perfect feedback and limited feedback scenarios.For downlink communication,when each base station(BS)transmits a single or multiple data symbols,the average sum rate performance of the proposed SLIR-US and MSE-OIA schemes is still better than that of the traditional OIA schemes,while when the base station transmits a single data symbol,the BER performance of the proposed SLIR-US and MSE-OIA schemes is also better than that of the traditional OIA schemes.Finally,based on cooperative NOMA,combined with D2 D communication and FD technology,a new interference management scheme is proposed,which is termed FD-D2D-NOMA scheme in a three-user downlink NOMA system.To facilitate the comparison,we further design two variants of the proposed FD-D2D-NOMA system.Changing the FD mode to HD and removing the D2 D transmission,we get HD-D2D-NOMA and non-D2D-FD-NOMA,respectively.Considering that in practical NOMA systems,due to the limitation of decoding ability,the near user can not always perform successive interference cancellation(SIC)successfully.Therefore,in perfect SIC and imperfect SIC scenarios,the close-form expressions for outage probability and ergodic sum capacity of the proposed FD-D2D-NOMA scheme are derived,and the corresponding theoretical analysis results of HD-D2D-NOMA and non-D2D-FD-NOMA schemes in perfect SIC scenario are also presented.On the one hand,the simulation results of the proposed FD-D2D-NOMA verify the correctness of the theoretical analysis in perfect SIC and imperfect SIC scenarios.On the other hand,compared with the existing cooperative NOMA schemes,the proposed FD-D2D-NOMA has great advantages in ergodic sum capacity and outage probability.The ergodic sum capacity and outage probability under different levels of residual self-interference at the FD user and residual interference at the far/near user due to imperfect SIC are investigated,and the results show that,such interferences have significant impact on the performance of the proposed scheme.We also discuss the impacts on performance exerted by channel conditions and design parameters in this paper.