| Recent research has shown that MIMO technique can be used to improve the systemcapacity and spectral efficiency significant. Meanwhile, OFDM technique has attractedmuch attention for its high tolerance to multi-path fading. MIMO-OFDM technique, widelyregard as a most promising solution, is efficient for wideband multimedia transmissionbecause of its high ability of anti-fading, high channel capacity and high bit-rate data. Inorder to improve the system performance, many research aspects, such as synchronization,equalization, coding, multiuser interference suppression etc. has achieved great attention.Especially, in recent years, using spatial diversity has become very popular. The research ofMIMO channel, as one of most important aspects in mobile communication, has achievedits significant status for signal resume, transmiter-receiver strategy and resource allocation,etc. Based on the above analysis, this dissertation undertakes some research work onchannel estimation and optimal resource allocation based on the system design. First, a optimal pilots in the transmitter diversity based on the MSE of system SNRwas deduced, and we propose an improved robust frequency domain diversity timecombining(FDTC) channel estimation algorithm. Compared with the existing alternativetransmitting pilot methods in 802.16, the proposed pilots' algorithm can be scattered in allthe pilot subcarriers. Especially in mobile channels, the proposed algorithm shows lowerMSE. And the FDTC algorithm can farther improve the performance, and have betterrobust and lower calculating complexity. When the bias of synchronization exists, theFDTC algorithm can revise the error of the phase offset. Comparing with the trans-domainmethods, the FDTC algorithm can avoid the serious aberrance, which is chiefly caused bythe energy leakage induced by the zero bands corresponding to the rectangular windowing. We next discuss the STBC in the MIMO-OFDM system. In the transmitting diversitysystem, because the signal from each antenna is different, it is difficult to analysis thesystem performance efficiently. In this dissertation, we propose a SISO model of MIMO IVsystem for OSTBC, which simplify the analysis complexity. Furthermore, we propose anoptimal power resource allocation strategy between data and pilots. Usually, in order toachieve the accurate CSI, we increase the power of the pilot. On the other hand, for thesake of achieving the precise decoding, we usually increase the power of the data. So theconflict comes forth under the total power restriction. The power resource allocationstrategy must show great importation in future adaptive wireless link for high spectraefficiency. Considering the independence of real-image part, we propose a new decodingalgorithm for STBC, which can reduce the decoding complexity from 2b to2b . Especiallyin high order modulation, this method can show superioritycompare with the ML method. At last, we thoroughly analysis the diversity for STBC in the multi-antennascorrelation fading channel and propose an adaptive OFDMA algorithm. Previous work onSTBC for MIMO-OFDM system has been restricted to idealistic propagation conditions.However, correlation exists in practice, the research in correlation fading channel showsgreat important. The multi-antennas channel can be divided into several independentsubchannels, and we discuss the power allocation according the subchannel gains base onthe maximum capacity and minimum BER. In this paper, the diversity gain and coding gainare first analyzed in unknown or known CSI in the correlation fading channel, and then wepropose a union transmit-receiver model for MIMO STBC, and depict the relationshipbetween the SNR and the eigenvalues of the correlation channel matrix. Based on thisconclusion, we propose an adaptive OFDM access(OFDMA) algorithm for multi-users forMIMO-OFDM system. The simulation show the adaptive algorithm has optimalper...
|
PDF Full Text Request