Researches On Key Techniques Of Differential Detection In Multiple-Input Multiple-Output

With the world wide increasing demand for wireless communications system capacity, the contradiction between the explosively increasing demand of capacity and limited bandwidth is the motivity and challenge to put researches on high spectral efficiency technologies. Among those emerging technologies, multiple-input multiple-output (MIMO) communication architecture has been proved to be one of the effective approaches to exploit maximum spatial resources and improve spectral efficiency dramatically. MIMO technology is one of the key techniques of future wide band wireless communications system.It is a difficult task to get exact channel estimation in MIMO system because of the time variation of channel or the fast movement of users. In these occasions, differential detection is an attractive scheme. Differential detection technique enables the receiver to detect the data symbols without knowledge of the channel, and the receiver is simple. Therefore, we apply ourselves to some research wok in this topic.Our researches focus on three types of MIMO signal differential detection techniques. The first one is the cretralized MIMO signal differential detection technique based on cretralized antenna systems. The second one is the MIMO signal differential detection technique based on asynchronism transmission manner. The last one is the distributed MIMO differential detection technique which is based on distributed transmit antenna systems.Firstly, we study the cretralized MIMO differential technique to resolve those problems of high computational complexity and low spectral efficiency of those existing schemes. The originalities are described as follows:(i) A low complexity differential detection scheme is proposed which is based on quasi-orthogonal space-time codes. Joint constellation pair mapping is used to construct quasi-orthogonal space-time codes at the transmitter. The symbol pairs can be detected in parallel manner. The ideas of joint constellation pair mapping and parallel differential detection reduce the detection complexity.(ii) A phase differential detection scheme based on Alamouti space-time code is presented through differential phase shift keying. It is very simple and applicable.(iii) A high spectral efficiency differential detection scheme is proposed, and thisscheme is also based on Alamouti space-time code. The proposed schemecan provide higher spectrum efficiency through angle rotation.Next, we study the differential MIMO system in asynchronism transmission manner to resolve those problems in cretralized MIMO system. The originalities are described as follows:(i) A baseband signal model of MIMO system in asynchronism transmissionmanner is considered, and we derive an expression in matrix form. Theproposed model makes the signal detection realizable.(ii) A differential detection scheme is presented for V-BLAST signal inasynchronism transmission scenario, and this scheme can implementdifferential detection with one receive antenna.Finally, we investigate the system model and differential detection technique for distributed MIMO system. The originalities are described as follows:(i) A baseband signal model for distributed MIMO in matrix form is derived,which makes the signal detection realizable.(ii) A differential scheme is proposed for V-BLAST signal in distributed MIMO,which is based on differential phase shift keying modulation. Only onereceive antenna is needed to implement differential decoding.(iii) A differential scheme is proposed for V-BLAST signal in distributed MIMO,which is based on differential amplitude phase shift keying modulation. Onlyone receive antenna is needed to implement differential decoding.(iv) A differential scheme based on Alamouti code is proposed. The idea ofdifferential encoding and decoding can also be extended to other types ofSTBC codes, such as quasi-orthogonal space-time codes.The research work in this dissertation enhances the studies of cretralized MIMO system, and makes advanced researches on MIMO system with asynchronism manner and distributed MIMO system. All these works lay the foundation for the application of differential detection technique in MIMO system.