Research On Space-Time Adaptive Receiver Of Wireless Communications

As viewed from signal processing, communications is a process to fulfill transport and detection of structural signal in the presence of interference case. The final aim and requirement of communications are the effectiveness of energy and the effectiveness of information. There is difference for the effect of signal structure in the different mobile communication environment. Two major factors that limit the performance of DS-CDMA systems are multipath channel distortion and multiple-access interference (MAI). To combat multiparth channel distortion and MAI, it is necessary to study the structure and algorithm of receiver. At first, wireless channel and characteristic of radio propagation are investigated in order to learn them. Then smart antenna, which will be adopted widely, is researched. Finally, the space-time receiver technology under multipath slow fading channels and multipath fast fading channels is studied emphatically, this content is the core of this paper. Contributions in this paper mainly show four points:1 The structure characteristic of the received DS-CDMA signal is analyzed in the presence of multi-path slow fading effect case for wireless mobile communication. According to this characteristic, four data-selected schemes based on chip-matched filter are presented from the perspective of energy and structure of signal. And the impact of these schemes on multiple-access interference (MAI) and inter-symbol interference (ISI) is analyzed.2 Both least mean-square (LMS) and least-square (LS) blind space-time receivers methods based on the Rosen's gradient projection are presented for space-time receiver that merge with the idea of smart antenna, and combined with the different data-selected schemes. The effect of these schemes on the computational complexity of two detection methods is analyzed. The simulations illustrate that those methods are effective.3 A novel recursive least-square (RLS) blind space-time receiver algorithm based on the constrained condition, which can completely avoid the matrix inversion introduced into by constraints (comparing with the normal RLS), is proposed for multi-path slow fadingCDMA channels. The computational complexity of this method is not only lower than that of the normal RLS, but also lower than that of both LMS and LS blind space-time receiver methods that are realized based on the Rosen's gradient projection. And the speed of convergence of the presented RLS blind space-time receiver algorithm is better than that of both LMS and LS blind space-time receiver methods. Combined with the data-selected schemes proposed, the computational complexity of this method can be lowered. The performance of the presented RLS method is analyzed by simulations, and it is shown that this method is interesting for application.4 Time-selective channel signal model based on multipath-Doppler diversity representation is given in multi-path fast fading channel, and RLS space-time receiver algorithm based on time-varied constraint condition is presented and the computational complexity of this method is analyzed. Simulations show that the performance (including convergence and detection) is well.