The Research On The Detection In VLST-OFDM System In Wireless Communications

Multiple Input Multiple Output (MIMO) system and Orthogonal Freqency Division Multiplex (OFDM) are widely recognized as a revolutionary technology for providing higher data rate in wireless communication system. This dissertation mainly concerns the following MIMO and OFDM technologies:We firstly introduced the background of capacity, and and space-time signal processing technology of MIMO system. The propogation property of the wireless channel is analyzed, and the MIMO channel modeling of frequency selective multi-path Rayleigh fading channel is presented.Secondly, we focus the research on the detection algorithm, especially the iterative detection algorithm of VLST system. The quasi-maximum a posteriori probability (QMAP) detection method, a low complexity iterative detection method, is proposed. By exploiting the structure of VLST detection method based on QR decomposition and cancellation, the a posteriori probability of the symbol vector is recursively calculated. In contrast to the optimum MAP detector, which performs an exhaustive search over the complete set of possible transmitted symbol vectors, the new scheme evaluates only symbol vectors that contribute significantly to the output of the detector. As a suboptimal detection method, the QMAP scheme has a high performance, with low complexity. For high-order QAM modulation formats, the complexity of the QMAP detector can be further reduced with the aid of multi-level searching.Carrier interferometry (CI) may be used to spread OFDM symbols over all N subcarriers to exploit frequency diversity without loss in throughput. In this paper, we implement the OFDM system incorporated with the carrier interferometry and VLST to undertake performance comparison in frequency selective fading channel. It is shown that the VLST-CI/OFDM system, offers considerable high throughput provided by VLST architecture. The novel system simultaneously achieves dramatic performance gains by taking advantage of large frequency diversity inherent in the CI/OFDM technique. The...