碩士 / 國立臺灣海洋大學 / 電機工程學系 / 99 / The objective of this thesis is to use the orthogonal frequency-division multiplexing (OFDM) technique to construct an underwater acoustic modem. In this research, we conduct both simulation and actual experiment to justify the goodness of the proposed OFDM underwater acoustic modem. In the simulation, we use the LabVIEW software to design the one-on-one OFDM underwater acoustic modem. The channel used for the simulation is a simulated time-varying shallow water channel with additive white Gaussian noise. In the receiving end, channel estimation and channel equalization are performed to combat the channel impairments. The resulting bit error rate and the normalized mean square error of the symbol are measured to verify the effectiveness of the design. Based on the simulation result, we construct the proposed underwater acoustic modem and conduct actual experiments to test its performance using a large experimental water tank as the underwater channel. The performance of the proposed modem is evaluated using the bit error rate. The result indicates that, when the distance between the transmitting and receiving transducers is small, an error-free transmission can be achieved. In addition, the bit error rate increases with the distance between the transmitting and receiving transducers. However, the bit error rate can be improved by increasing the transmitting power of the underwater modem. This result justifies the potential of applying the proposed OFDM underwater modem to real underwater environments.
Keywords: Orthogonal frequency-division multiplexing, channel estimation, equalizer, underwater modem.
| Identifer | oai:union.ndltd.org:TW/099NTOU5442021 |
| Date | January 2011 |
| Creators | Che-Yi Lin, 林哲億 |
| Contributors | Ching-Hsiang Tseng, 曾敬翔 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 72 |
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