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Precoding For Downlink Non-orthogonal Multiple Access

Posted on:2018-11-15Degree:DoctorType:Dissertation
Country:ChinaCandidate:Z Y ChuFull Text:PDF
GTID:1318330512482672Subject:Communication and Information System
Abstract/Summary:PDF Full Text Request
As the rapid development of modern information society,high-speed mobile mul-timedia services have replaced the traditional voice and low-speed data transmission services,and have became one of the most important mobile communications services.To cope with the explosive growth of mobile data traffic,the fifth generation(5G)mo-bile communication system encounters many challenges,including providing better us-er experience,affording higher data transmission speed,and improving users' quality of service,with limited spectrum resources.To meet these challenges,the most important thing is to improve spectrum efficiency.Recently,many studies have shown that the use of multiple input multiple output(MIMO)can improve the spectrum efficiency and reliability of wireless communications.Under the assumption of perfect channel state information at transmitter(CSIT),the overall performance can be further enhanced by developing proper precoding strategies.On the other hand,different from conventional orthogonal multiple access(OMA)technologies,non-Orthogonal multiple access(NO-MA)can further improve the spectrum efficiency,and has attracted extensive attention,and has been recognized as a promising candidate for 5G mobile communication sys-tems.In this dissertation,taking 5G and its requirements as the background,by combin-ing MIMO technology with NOMA technology,low-complexity precoding algorithms for MIMO broadcast channel(BC)are studied.Specifically,the research work can be summarized as follows:1)The design of precoding for two-user MIMO BC is considered,under the con-straint of the symbol error rate(SER)performance.Firstly,MED precoding algorithm for MIMO unicast scenario is proposed,by utilizing Lattice theory and recursive construction method.Then,by combining the idea of generalized sin-gular value decomposition(GSVD)and alternative optimization,NOMA-MED precoding algorithm for two-user MIMO BC is also proposed.2)The design of precoding for two-user MISO BC is considered,under the con-straint of the achievable transmission rate performance.Firstly,the optimum NOMA precoders for two-user MISO BC is proposed,by using convex optimiza-tion theory.The properties and performance are also profoundly analyzed.Then,a new concept,termed as quasi-degradation,is proposed,by studying the perfor-mance gap between the optimum NOMA and DPC schemes.Moreover,a low-complexity H-NOMA(hybrid NOMA)precoding algorithm for two-user MISO BC is developed,by taking the advantage of the concept of quasi-degradation.Fi-nally,the performance of H-NOMA,optimum NOMA,conventional ZFBF(zero-forcing beamforming)and DPC are analyzed and compared.3)The design of precoding strategies for multi-user hybrid multiple access MI-MO BC is considered,under the constraint of the SER performance and achievable transmission rate performance,respectively.In hybrid multiple access systems,users are grouped into small-size clusters,and NOMA was im-plemented for the users within one cluster,while OMA was used inter cluster to cancel interference.These precoders are developed to minimize the overall trans-mission power under the constraint of guaranteeing each user's performance,i.e.,SER performance or achievable transmission rate performance.This work main-ly includes the following two aspects.Firstly,under the constraint of the SER performance,MED precoders for two-user MIMO BC are used in one cluster,by designing the corresponding user pairing algorithms,the proposed precoding schemes for multi-user hybrid multiple access MIMO BC are obtained.Secondly,under the constraint of the achievable transmission rate performance,H-NOMA precoding algorithm is adopted in one cluster,by designing the corresponding user pairing algorithms,the proposed precoding schemes for multi-user hybrid multiple access MISO BC are obtained.
Keywords/Search Tags:Multiple Input Multiple Output, Non-orthogonal Multiple Access, Broad-cast Channels, Precoding, Hybrid Multiple Access Systems
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