Design of OFDM Underwater Acoustic Modem

• Main Authors: Wei, Chih-Ling, 魏志陵
• Other Authors: Hung, Hsien-Sen
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/44825399682280153812

碩士 === 國立臺灣海洋大學 === 電機工程學系 === 102 === In the thesis, we design an OFDM-based acoustic underwater communication system, which can improve communication efficacy. Performance of underwater acoustic communication is greatly affected by factors of very limited bandwidth, severe multipath fading as well as the inter-carrier interference due to Doppler- induced carrier frequency offset. Therefore, the proposed receiver involves Doppler compensation, different channel estimation and equalization schemes for slowly- changing and fast-changing channels. In addition, a low-density parity-check (LDPC) code is also incorporated to significantly reduce bit error rate (BER) at the price of reduced data rate. This thesis uses the measured impulse responses of specific north-eastern sea region, provided by the MACHO project, as a reference to Jakes model for the underwater channel simulator. Computer simulation results show that the adaptive and pilot-based equalizer are effective, respectively, in slowly- changing channels and fast-changing channels, whereas the pilot-based equalizer can cause a reduction of bandwidth efficiency. Furthermore, the insertion of a LDPC code can greatly improve the BER performance.