| Summary: | 碩士 === 國立臺灣海洋大學 === 電機工程學系 === 98 === In underwater channels, advanced signal processing techniques are needed to increase data transmission rate and reliability due to limited available bandwidth, serious Doppler spread, and multipath fading. MIMO systems can provide multiplexing and diversity gains to improve communication quality and increase data transmission rate. The technique of orthogonal frequency division diversion multiplexing (OFDM) is able to confront frequency selective fading, thus making intersymbol interference insignificant. Although MIMO-OFDM systems have been proposed lately for underwater acoustic communications in the literatures, they were limited to single user environments. For an underwater sensor network of multiple users, the techniques of combating multiple access interference (MAI) among users require further investigation.
In this thesis, the techniques of MIMO, OFDM, and multiuser detection are employed in the design of acoustic transceiver for underwater sensor networks. The Jakes model is utilized as an underwater channel simulator in which parameters are adjusted according to the sea-trial data. Multiuser linear and widely linear detectors are investigated by computer simulation and performance evaluation to see if they are feasible to underwater communication networks. Simulation results show that the widely linear minimum mean-square error (MMSE) detector has the minimum bit error rate, while maintaining the same level of operational complexity, as compared to linear detectors.
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