| Summary: | 碩士 === 元智大學 === 通訊工程學系 === 95 === In this thesis, we tackle two problems in modern wireless communication system design. One is sounding with high path resolution, and the other is a single carrier GMSK system design with frequency-domain equalizer.
For the first problem, we propose a novel frequency-domain channel sounding technique based on T/2-spaced sampling sequence. Instead of adopting the entire frequency range for channel estimation, we simply utilize a segment of channel frequency response and exploit sinusoidal parameter estimation and detection to deal with this problem. Especially, we consider the pulse shaping effect, and determine the optimal frequency-domain estimation range through simulation analysis. Based on the proposed high path resolution channel sounding scheme, the resolution of the target channel can be as good as 0.2T (T: symbol time) with an NRMSE lower than 10% when SNR=30dB. Compared with the conventional time-domain correlation-based channel sounding, which can only attain a maximum resolution of 2T, the new technique improves the path delay resolution by 5 to 10 times, depending on the channel complexity.
For the second problem, a novel linearized Gaussian minimum shift keying (LGMSK) system is proposed for block data transmission. In each block, a known unique-word (UW) is inserted as guard interval, and a phase state return bit (PSRB) is also added to maintain LGMSK phase trellis consistency. It is shown that the transmit signal has near constant-envelope property. At the receiver, a frequency-domain decision-feedback-equalizer (FD-DFE) is designed to combat the joint effect of partial response signaling and the channel dispersion. With only a few feedback taps, the receiver can significantly outperform the FD linear equalizer. Compared with the Viterbi receiver, it has only 0.4-dB degradation at BER=10-6 over AWGN channel. Hence, the proposed system has the great merits of transmit power saving, high performance, and low receiver complexity, especially for high-rate application through long dispersion channel.
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