Research On Fairness Of Multi-user Massive MIMO Systems

With the continuous innovation and advancement of wireless communication technology,future core application scenarios require lower error control rate and higher user access.Therefore,resource allocation and user fairness have become the focus of research.This is a complete challenge for wireless communication system.Wireless multimedia multicast is a technology that effectively utilizes wireless communication-related resources.It can transform inefficient pointto-point transmission into efficient point-to-multipoint transmission.In addition,the increasingly constrained spectrum is a key obstacle.The current orthogonal multiple access scheme is difficult to satisfy more user connections with limited resources.Therefore,the wireless multimedia multicast technology and Non-orthogonal Multiple Access(NOMA)technology provide a new solution to the above problems.This paper focuses on the study of precoding-based NOMA multicast technology in multi-user massive Multiple-Input Multiple-Output(MIMO)systems.It investigates how to achieve a balance between user fairness,system error rate,sum rate and other performance factors.The specific contents are as follows:First,this paper proposes an omnidirectional fairness-based multiuser multicast precoding algorithm,which aims to solve the problem of adjacent base station interference in conventional multiuser multicast systems in order to improve the reception reliability of users,while alleviating the contradiction of differences between users with poor channel quality and those with better channel quality.Specifically,this paper first introduces three transmission design requirements for omnidirectional fairness precoding.Secondly,the construction scheme of complementary sequences and complete complementary sequence sets that can be used to construct omnidirectional precoding is described in detail,and two transmission schemes based on complementary sequences and complete complementary sequences are proposed.Subsequently,the NOMA multicast transmission system implementing omnidirectional fairness precoding is studied.Firstly,the transmission system model and codebook of sparse code division multiple access multicast based on omnidirectional fairness precoding are presented,followed by the study of decoding for sparse code division multiple access multicast based on omnidirectional fairness coding.Finally,through simulation and testing of the bit error rate,the proposed two transmission schemes are demonstrated to provide better reliability than traditional schemes,demonstrating that the multi-user multicast precoding algorithm based on omnidirectional fairness can greatly enhance the received signal strength of multicast group users,especially those on the edge of the cell.Second,this paper proposes a multi-user multicast precoding algorithm based on maximum minimum fairness,aiming to resolve the contradiction between the difference between multicast group throughput and user throughput and to balance them while ensuring cell throughput and user fairness.Specifically,this paper first introduces the principle of maximum minimum fairness of massive MIMO-NOMA multicast and discusses the problem modeling method of this scheme.Secondly,it describes in detail the system model of the downlink in massive MIMO-NOMA based on maximum minimum fairness precoding,and focuses on the design of precoding and power allocation.Then,the objective function and constraints in this scenario are analyzed,and convex optimization techniques are used to solve the problem,thereby achieving the sharing of data signals transmitted by the base station between the central and edge users in the cell,improving the throughput of edge users with poor channel quality,and improving user fairness in the cell.Finally,this article verifies through numerical simulation that the proposed maximum minimum fairness precoding algorithm can achieve the goal of maximizing the minimum user rate,demonstrating that the multi-user multicast precoding algorithm based on maximum minimum fairness can not only improve the reception reliability of users with poor channel quality but also meet the requirements of overall system reliability.