Research On MU-MIMO Downlink Resource Allocation In LTE-A Systems

Multi-User MIMO(MU-MIMO)technology has drawn extensive attention in the industry due to its advantages of significant improvement in system capacity and spectrum efficiency.How to allocate limited time-frequency resources to users efficiently has an important impact on the performance of the MU-MIMO system.In this paper,the problem of resource allocation in MU-MIMO system is explored.Firstly,this paper introduces the research background,research status and key technologies in MU-MIMO downlink and the precoding technology against IUI and classical user scheduling algorithm are stressed.Then resource allocation in MU-MIMO systems based on user grouping is studied.The key of user grouping is to roughly estimate the possible inter-user interference when more than one users multiplexes the time-frequency resource according to the channel correlation among users.User grouping can effectively alleviate the complexity of MU-MIMO resource allocation algorithm.AUG algorithm and JUG-RA algorithm are deeply studied and compared.AUG and JUG-RA cannot balance sum data rate and fairness well.To make up the disadvantage,UGB-PF algorithm is proposed,which is combined user grouping with proportional fairness novelly.UGB-PF can make a better balance between sum data rate and user fairness than AUG and JUG-RA.After that,the user selection algorithms in MU-Massive-MIMO systems are studied.Typical SUS algorithm and GUS algorithm are studied.SUS algorithm does not consider user channel condition and GUS algorithm ignores the impact of latter users on former users resulting the unfairness among users.To make up these disadvantages,the concept of benefit loss ratio is introduced which can describe the effect mentioned above.Based that,Max B/L algorithm is proposed,in which maximum benefit of the system's spectral efficiency is obtained in the price of minimum rate loss of formerly selected users.Compared with SUS and GUS,Max B/L can achieve spectrum efficiency and user fair improvement simultaneously.Last,the paper is summarized and future research is prospected.