극천해 다중경로 환경에서 BFSK의 이미지 전송 성능

Abstract

Underwater acoustic communication system is highly sensitive to channel characteristic which depends on environmental parameters such as background noise, sea surface state, and depth dependent sound speed profile. Special emphasis on the bit error rate (BER) has been given to the effect of time-varying signal fluctuation due to sea surface roughness, which results in severe degradation of system performance by causing time and frequency spread of the transmitted signal. In highly absorptive sea bottom and rough sea surface in deep water, the effect of bottom and sea surface reflection may be ignored by operating the acoustic communication system under vertical channel. Under this channel, the multipath signal from the boundaries is relatively weak to the direct path signal since the subtend angle is high enough to reduce the amplitude of boundary reflected signal. However, in shallow water or in long range horizontal propagation channel, the boundary reflected multipath signals are high enough to interfere the direct path signal and to induce an inter-symbol interference (ISI). In this study, image transmission performance of Binary Frequency Shift Keying (BFSK) in very shallow water is examined to figure out the range dependent image quality based on BER.