Research On Non-codebook Based Beamforming Technology In TD-LTE-Advanced Downlink

As the mobile communications standard with independent intellectual propertyfor China, TD-LTE-Advanced standard has been accepted as one of InternationalMobile Telecommunications-Advanced (IMT-Advanced) compliant systems and willbe deployed in China in the future. Enhanced MIMO and related beamformingtechniques have been introduced to TD-LTE-Advanced to meet the requirement ofhigh spectrum efficiency and transmission rate. Among the techniques,non-codebook based beamfoming techniques have attract more and more attentionas they have the advantages of smart antenna technique in TD-SCDMA and are verysuitable for TD-LTE-Advanced downlink. Appropriate beamforming techniques candecrease the co-channel interference of users and increase the system performance,and especially in the TD-LTE-A downlink, the downlink transmit beamforming canalso help to reduce the design complexity and energy consumption of user terminal.In this paper, we mainly focus on the research of non-codebook basedmulti-user beamforming of the TD-LTE-A downlink. In the second chapterbeamforming theory and multi-user beamforming algorithms are introduced. And itis showed by simulation that signal to leakage and noise ratio (SLNR) basedalgorithm has a better performance than zero-forcing (ZF) and block diagonalization(BD) algorithms for multiuser beamforming. In addition, SLNR based algorithm iseasy to realize. Then in the third chapter, beamforming are combined withscheduling and a suboptimal maximum minimum SLNR (MMSLNR) schedulingstrategy is proposed and compared with conventional strategies. Simulations showthat the proposed strategy has a better performance than conventional strategies andis very close to the performance of exhaustive traversal, while it can decrease thecomplexity of the scheduling process by almost two magnitudes compared with theexhaustive traversal strategy. Then power allocation with SLNR beamforming isresearched in the second part of the third chapter. The power allocation algorithmsbased on the users’ requirement are proposed for the same kind of servicetransmission and different kinds of service transmission, respectively. In the firstscenario, the proposed algorithm can balance the system performance and userfairness while in the second scenario the proposed algorithm can reach the differentrequirement of Quality of Service (QoS) of users effectively.Finally, different mobile communication services and their QoS requirementare introduced in TD-LTE-Advanced. Then a kind of satisfaction parameter isdescribed and SLNR beamforming algorithms weighted by SINR and satisfaction parameter are given. Simulation shows the weighed beamforming algorithms canincrease the system performance of SINR and satisfaction parameter, respectively.Then the satisfaction parameter based MMSLNR algorithm is proposed forscheduling of different services and users. In the algorithm, guaranteed bit rate(GBR) services are scheduled preferentially, and the satisfaction parameter isadjusted dynamically, and as a result the average satisfaction level of all users areobviously improved and the fairness of users and transmission efficiency areensured.