• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.8 no.6
• /
• pp.1243-1249
• /
• 2004

In this paper, the multipath effect on underwater acoustic channel bandwidth and BFSK and BPSK bit error dependancy on channel bandwidth are analyzed. The multipath is modeled as a discrete multipath and a continuous multipath and the channel bandwidth is expressed as a function of multipath delay spread constant. Bit error characteristics on the channel bandwidth and the criteria of the multipath delay spread constant are found through the numerical simulation. The transmission bit rate of less than 100bps in the water tank which has a channel bandwidth of 100Hz, is a consistent result with the numerical simulation.

• The Journal of the Acoustical Society of Korea
• /
• v.38 no.4
• /
• pp.371-377
• /
• 2019

In this paper, we present the sea trial results of long distance underwater acoustic communication in the East Sea, October 2018. One transmitter and sixteen vertical array receivers were used to collect underwater acoustic communication signals, and the maximum distance between the transmitter and the receiver was 90 km. Information was transmitted by BFSK (Binary Frequency Shift Keying) and BCSK (Binary Chirp Shift Keying) method, which are typical digital frequency modulation techniques. Experimental results show that there is no error in all cases at the transmission distance of 60 km, and BFSK and BCSK have average uncoded bit error rate of 0.0197 and 0.0007 respectively without channel coding at 90 km transmission distance.

• The Journal of the Acoustical Society of Korea
• /
• v.22 no.5
• /
• pp.418-424
• /
• 2003

In this paper we analyzed the performance of data transmission using BFSK modulation. The system performances were evaluated by the experiments in water tank. As a result we showed the influences of reverberation due to the multipath. In order to simplify the experiment procedure the channel coding etc. were omitted. The experimental result shows that the maximum transmission data rate in used water tank is about 800 bps. We also verified that the reverberation effect m reduced using a deconvolution with a measured channel impulse response. This method improved the bit rate by about 100 bps than simple noncoherent demodulator at bit error rate of 10/sup -3/.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.1
• /
• pp.1-8
• /
• 2011

In this paper, a water tank experiment using Binary Frequency Shift Keying (BFSK) method for text transmission performance by water surface fluctuation is conducted. Water surface fluctuation and delay spread which affect the channel coherence bandwidth is a limiting factor in underwater acoustic communication. The amplitude fluctuation and delay spread the smooth surface and fluctuation surface, were identified. The effective delay spread of both cases are 5ms, 4ms corresponding to the coherence bandwidth of 200Hz, 250Hz, respectively. The bit error rate of BFSK modulated text transmission is about $10^{-4}$ in less than 200bps in smooth surface but less than 250bps in fluctuation surface. Therefore, this experiment shows that the water surface fluctuation is important factor determining the performance of the underwater acoustic transmission.

• The Journal of the Acoustical Society of Korea
• /
• v.32 no.2
• /
• pp.95-103
• /
• 2013

An underwater acoustic (UWA) communication in shallow water is strongly affected by the water surface and the seabed acoustical properties. Every reflected signal to receiver experiences a time-variant scattering in sea surface roughness and a grazing-angle-dependent reflection loss in bottom. Consequently, the performance of UWA communication systems is degraded, and high-speed digital communication is disrupted. If there is a dominant signal path such as a direct path, the received signal is modeled statistically as Rice fading but if not, it is modeled as Rayleigh fading. However, it has been known to be very difficult to reproduce the statistical estimation by real experimental evaluation in the sea. To give an insight for this scattering and grazing-angle-dependent bottom reflection loss effect in UWA communication, authors conduct experiments to quantify these effects. The image is transmitted using binary frequency shift keying (BFSK) modulation. The quality of the received image is shown to be affected by water surface scattering and grazing-angle-dependent bottom reflection loss. The analysis is based on the transmitter to receiver range and the receiver depth dependent image quality and bit error rate (BER). The results show that the received image quality is highly dependent on the transmitter-receiver range and receiver depth which characterizes the channel coherence bandwidth.