Resource Allocation Algorithm For MU-MIMO Systems With Double-Objective Optimization Under The Existence Of The Rank Deficient Channel Matrix

In order to meet the rapidly increasing needs of people and social requirements for energy saving and environmental protection,wireless communication technology has become one of the research hotspots in the communications field.In the Long Term Evolution(LTE)era,Wireless to The x(WTTx)has become the new radio access technology.Meanwhile,in order to support a higher transmission data rate,next-generation mobile systems are broadening their spectrum to higherfrequency bands(above 6 GHz).The high frequency spectrum offers many advantages for wireless communication systems such as broad bandwidths for high data rate information transfer,higher directivity and spatial resolution,low probability of interference due to narrow antenna beamwidths,and etc.But the high frequency spectrum also brings new challenges to the development of wireless communication,that is,the non-rich scattering environment.In a non-rich scattering environment,correlation between transmission channels due to the lack of obstacles and scatter,and the channel matrices are rank deficient.Multiple-Input Multiple-Output(MIMO)technology is one of the most important components of LTE system,which has many significant advantages in resisting channel fading and improving the data transmission rate.In particular,the remarkable advantage of MultiUser MIMO technology is that it can significantly improve system throughput through space resources rather than spectrum resources,thus becoming one of the key technologies of 5G(5thGeneration).In the MU-MIMO system,as the number of antennas increases,the system throughput increases,but the consumption of electric energy also increases.Thus,the concept of energy efficiency(EE,represented by transmission data rate per unit energy)has emerged as one of the optimization goals in wireless telecommunication systems.Therefore,how to efficiently optimize the energy efficiency and system throughput of MU-MIMO system through resource allocation has become one of the research hotspots in the wireless communication field.In addition,the QoS(Quality of Service)guarantee must be taken into account when designing the resource allocation algorithm,including delay requirements and rate requirements,and different kinds of services have different QoS requirements.The paper analyzes the factors that affect the rank of MIMO channel matrix and proposes ideas on how to increase rank of MIMO channel matrix.In addition,the paper research how to improve the performance of MIMO system by resource allocation when the rank of MIMO channel matrix is not full(we call it as rank deficient)and cannot be increased.To improve the performance of MIMO system in the rank deficient environment,the paper proposes a double-objective optimization resource allocation algorithm.The proposed algorithm simultaneously optimizes the effective system throughput(effective system throughput only counts users' data rates between their required upper and lower bounds)and the energy efficiency while guaranteeing the QoS requirements,including the upper and lower bounds of the data rate requirements and delay requirements.Since the optimization problem established in this paper has two optimization objectives and many constraints,it is not a standard convex optimization problem and cannot be directly solved by convex optimization method.The paper utilizes the Lagrange dual method to solve the doubleobjective optimization problem.The simulation results show that the proposed two-objective optimization algorithm has significant advantages over other existing algorithms in terms of simultaneous optimization of system throughput and energy efficiency.Numerical results shown that the proposed double-objective optimization algorithm is superior to the existing single-objective optimization algorithms in terms of energy efficiency and effective system throughput.