| Because of enabling to provide high-rate and high-quality wireless and mobile communication service, Orthogonal Frequency Division Multiplexing (OFDM) system is becoming a very hot research topic recently, and it is especially one of the technical difficulties to estimate and equalize the time-varying (TV) dispersive channels. In this thesis, we are working on the topic based on some of the precedents' results.According to wireless and mobile communication system's background, this thesis study on estimation of time-varying dispersive channel from four respects: (1) aid of pilots, (2) cyclic prefix(CP), (3) blind method, and (4) OFDM system with multiple transmitting antenna, in which the typical ways is decision-feedback algorithm and self-adaptive block algorithm.The main works and innovations of this thesis are as follows:(1)Based on the oversampling of OFDM frequency response, this paper proposes a channel estimator which combines the comb-pilot-tones partitioning and the Fourier Transform with the same pilot symbol samples. Comparing with si(sin(x)/x) interpolator, cubic interpolator with low pass filter, and Winner interpolator in 16QAM OFDM system both in mean square error and bit error rate without encoding, the results of the method proposed by this thesis show that the performance is better than si interpolator and cubic interpolator with low pass filter, and close to the Winner interpolator but the complexity is much lower than the latter.(2) Estimation and equalization of multipath fading wireless channel which was modeled as complex-taps FIR have been done using cyclic prefix under I/Q modulation. The simulation results show that our algorithm is effective in tracking the changing of channel without deep fading under the condition that transmission efficiency has been double compared with [113] with the same sub-carriers; It is also effective to track the channel with deep fading under the condition that transmissionefficiency has been increased obviously when linear precoded technology is used.(3) A blind channel estimator based on the aid of Pseudo-Pilot-Symbols(PPS) is proposed in term of the two characters of OFDM system: the finite alphabet property of information symbols and independent property between subchannels. Unlike pilots which are used for estimation of channel and must waste some useful bandwidth, the PPSs, whose power can be boosted 3dB or 6dB to suppress efficiently the additive noise, is useful data transmitted, thus efficiency of the OFDM has been increased. Performance simulation of the proposed estimator including Mean Squares Error (MSE) of channel and uncoded Bit Error Rate(BER) have been taken, and the results show the estimator is efficient and very flexible.(4)A channel estimator using the aid of pilot-symbol is proposed in OFDM system with multiple transmitting antennas. The simulation results shows that the performance comparison among OFDM system with two transmitter antennas and single receiver antenna, OFDM system with single transmitter antenna and two receiver antennas and OFDM system with two transmitter and receiver antennas is given, the result shows that the performance of OFDM with independent multi-antenna pair is better than that with single pair. At the same time, a simple channel estimator that can suppress the peak-to-average power ratio (PAPR) for OFDM system with multiple transmitter antennas is proposed, its simulation proves again the result.(5) OFDM receiver is proposed with multiple transmitter antenna and Alamouti scheme. In term of the orthogonal property of Alamouti scheme and the character of the OFDM system equivalent model expression of receiver signal for STBC-OFDM system was obtained by flexible transform method so that the inverse of matrix was avoided using direct-decision mode and the complexity of computation and receiver was decreased. The simulation results show the validity and efficiency of the proposed receiver.(6) An adaptive equalization algorithm used in Space-Time Block Coded OFDM (STBC-OFDM) syst...
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