Performance Research On The Coherent And Noncoherent Space-time Code

This dissertation studies several key issues of coherent and noncoherent space-time code. The structure of the dissertation is classified into following parts:1.Propose the ordered sphere decoder so that it can process the constellation with any shape and quicken the decoding time. Spatial multiplexing can markedly improve the spectrum efficiency. V-BLAST is a kind of efficient decoding method devised by Bell Lab, but its defect lies in lessening the diversity order due to nulling operation for each layer. Sphere decoding can achieve the performance of maximum likelihood decoding at the expense of lower computation complexity. The original sphere decode algorithm of Viterbo can only tackle the real constellation, and this dissertation adapts it to tackle complex constellation with any shape. Because it's coherent demodulation, the CSI of each layer may be utilized. The decoding sequence of each layer is sorted according to its CSI value, which means the layer with good quality is decoded first, and the layer with bad quality is decoded second. Some heuristic rules are added to make the final decoding time decrease sharply. Compared with V-BLAST, OSD can apparently improve performance with a little additional complexity.2.Deduce the error probability formulation of noncoherent unitary code under spatial fading correlation. For the noncoherent demodulation, Hochwald get the pair-wise error probability (PWEP) of unitary space-time code under flat fading and no fading correlation condition. In practical MIMO system, the distance between each antenna element cannot be very large, so there exists spatial fading correlation between antennas. This dissertation considers the impact of the fading correlation on the performance of unitary code. Beginning with the decision variable of unitary code, the moment generation function is obtained, then the Fourier transformation of moment generation function is deduced, its PWEP is achieved as well. The property of unitary code is utilize in the deducing process to achieve the Chernoff upper bound and union bound of PWEP. Hochwald's conclusion is included in the final formulation, which signifies no fading correlation is only a special case of fading correlation. The degradation level of block error rate incurred by fading correlation is obtained according to this formulation. Various degradation levels owing to various fading correlation matrix are simulated, and the simulation result tally with the...