주파수 선택적인 수중 음향 채널에서 고속 정보전송 기법 연구

Abstract

UWA (Underwater acoustic) communication is essential technology for seabed mineral resource exploration, harbor defense and underwater unmanned undersea vehicle control and so on. It is highlighted future industrial technology bringing national interest. Acoustic wave is only means of information transfer in the underwater. However, UWA communication performance is affected by time varying environmental factors of channel such as doppler effect, ambient noise, transmitted loss and multipath and so on. In underwater environment, QPSK (Quadrature Phase Shift Keying) method is generally adopted to improve the data rate. Also, OFDM (Orthogonal Frequency Division Multiplexing) method is suggested for high-speed data transmission in frequency selective channel. In particular COFDM (Coded OFDM) with FEC (Forward Error Correction) is applied to solve degradation in frequency selective multipath channel. In this study, performance of QPSK and QPSK with FEC code is evaluated in water tank and performance of OFDM and COFDM for high underwater data transmission is also evaluated. It is found that COFDM shows 8 times more in data rate than QPSK under same SNR (Signal to Noise Ratio), COFDM is also effective to decrease BER (Bit Error Rate) in frequency selective deep fading channel even if channel bandwidth is less than sub-channel bandwidth of OFDM.