| With the increasing development of various services via wireless communications such as mobile voice, data, image, multimedia and internet applications in the recent years, the wireless communication is required to provide higher transmission rate with higher reliability, so that anti-multipath-fading techniques have been a hot point in this research area.This dissertation researches on block transmission system, paying great attention to the frequency band efficiency as well as the transmission performance in the multipath fading channels. The main contributions of the dissertation are as follows.A multiple blocks joint modulation technique is proposed. Through analyzing the spectral property of quasi-orthogonal time division multiplexing (QOTDM) system, a modified QOTDM system scheme and a blind equalizer for the system are proposed. Then, aiming at the problem of how to reduce the redundancy of the cyclic prefix (CP) in single carrier block transmission (SCBT) and orthogonal frequency division multiplexing (OFDM) systems, a QOTDM based block modulation (BM) algorithm is proposed, where multiple blocks are jointly modulated together to share a CP, which remarkably increases its band efficiency. When the BM frame is decomposed at the receiver, the multiple blocks can be obtained from the received signal without inter-block interference (IBI). The BM algorithm can be applied not only to SCBT and OFDM systems, but also to multi-input multi-output (MIMO) or MIMO-OFDM systems. Theoretical analysis and simulations show that the proposed system scheme for slow-fading channels has much higher band efficiency without performance degradation compared with the existing algorithms.A novel bidirectional arbitrated decision feedback (BAD) equalizer is presented for two-path fading channels, which can effectively improve the bit-error performance by acquiring diversity gains from combining the output of the forward and reversal infinite impulse response (IIR) equalizers with decision feedback architectures using maximal ratio combining (MRC) rule. The combining procedure needs only linear complexity rather than so high complexity of the local maximal likelihood sequence estimation (MLSE) as employed in the existing BAD equalizers. Simulations show that the proposed BAD algorithm obviously over-performs the existing bidirectional IIR equalizer with decision feedback in both channel conditions of minimum and non-minimum phase systems. Aiming at the defect of losing diversity gain in SCBT systems with time domain or frequency domain equalization, a RAKE receiver scheme for non-spectrum-spreading SCBT system is proposed, which can improve the bit-error performance by taking advantage of the multipath diversity gains. The RAKE receiver is realized by means of reconstruction of the multipath signals and multi-stage interference cancellation equalizer. Theoretic analysis and simulation results show that the proposed algorithms can effectively improve the performance of the single-carrier equalizer; moreover, it can also be combined with other equalizers since its initial solution can be obtained by using various commonly used equalizers.A scheme of space-time two dimensional (2D-) RAKE receiver is proposed for non-spectrum-spreading MIMO systems. Firstly, the single carrier frequency domain equalization combined with space-time block codes (STBC-SC-FDE) is investigated, and the scheme applied to the MIMO system with four transmit antennas is deduced. Then, similar to the interference cancellation (IC) technique in single antenna systems, the space time IC technique is employed to improve the performance of STBC-SC-FDE. Further, the 2D-RAKE receiver is accomplished in the system by decomposing the received signal and combining the multipath components based on STBC combination and multipath combination rules. Finally, the proposed 2D-RAKE is introduced into the multiuser MIMO systems to achieve both the spatial and multipath diversity gains for each user. Simulation results show that the proposed algorithms behave well.
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