碩士 / 國立海洋大學 / 電機工程學系 / 89 / Undersea communication has received much attention in recent years. The undersea environment is varying and inhomogeneous. The propagation loss of electromagnetic or light wave in the water is very high, therefore, electromagnetic and light waves are not suitable for underwater communications. The propagation loss of sound wave in the water, however, is acceptable. Therefore, sound wave becomes the main choice for underwater communications. Since the bandwidth of the underwater communication channel is very limited, for transmitting high data rate signals such are speech, data compression is essential.
In this thesis, the standards of G.729 speech coder is studied. By increasing the frame length in G.729, the required bit rate can be reduced. However, this also decrease the quality of the speech signal. By incorporating the concept of fixed algebraic codebook in G.723.1, the quality of the speech signal can be improved. To justify the feasibility of the resulting speech coder/decoder, we used the TI C6211 fixed-point DSP (Digital Signal Processor) chip to implement the developed decoder. Real time decoding of the speech signal showed that the speech quality is acceptable.
| Identifer | oai:union.ndltd.org:TW/089NTOU0442009 |
| Date | January 2001 |
| Creators | HinPeng Teoh, 張興平 |
| Contributors | 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 | 60 |
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