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Research On Hybrid Beamforming Method For Millimeter Wave Massive MIMO Systems

Posted on:2020-02-28Degree:MasterType:Thesis
Country:ChinaCandidate:S FengFull Text:PDF
GTID:2428330590974093Subject:Information and Communication Engineering
Abstract/Summary:PDF Full Text Request
With the rapid development of communication technology,the evolution of wireless communications is driven by the increasing demand for mobile data service.5G is expected to achieve a transmission rate of 1 Gb/s,which is more than ten times faster than that of 4G.Millimeter wave(mmWave)communications has been regarded as a key enabling technology for 5G networks,as it offers orders of magnitude greater spectrum than current cellular bands.In contrast to conventional multiple-input–multiple-output(MIMO)systems,beamforming in mmWave MIMO cannot be performed entirely at baseband using digital beamformers,as only a limited number of signal mixers and analog-to-digital converters can be supported considering their cost and power consumption.As a cost-effective alternative solution,a hybrid beamforming transceiver architecture,combining a digital beamformer and an analog beamformer,has recently received considerable attention.However,the optimal design of such hybrid precoders has not been fully understood.In this paper,a hybrid beamforming algorithm is designed for single-user narrow-band millimeter-wave systems.We treating the hybrid beamformer design as a matrix factorization problem,the characteristics of the digital beamforming matrix and the analog beamforming matrix are analyzed and their closed expressions are obtained respectively.Effective alternating minimization algorithms are proposed for the fully-connected hybrid precoding structures,which helps decouple the precoder design problem into two subproblems,i.e.,the analog and digital precoder design.The proposed algorithm avoids the iterative search process and does not require candidate sets has lower complexity and can be generally applied to both narrowband and broadband OFDM systems.Simulation results will demonstrate that the algorithm efficiently identifies a near-optimal solution.The research of hybrid beamforming method is further extended to multi-user system.In multi-user system,all user share one analog beamformer,but each user has its own digital beamformer.The design of multi-user hybrid beamforming is transformed into multiple single-user designs,and the objective function expressions of the simplified multi-user hybrid beamforming design are derived.We initialize the analog beamforming matrix at first and then iteratively optimize the hybrid beamforming matrix by the alternate minimization optimization algorithm.Simulation results shows that the performance of the proposed hybrid beamforming algorithm is close to that of the all-digital precoding algorithm.
Keywords/Search Tags:mmWave communications, massive MIMO, hybrid beamforming
PDF Full Text Request
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