Research and Development of a Highly Reconfigurable OFDM MODEM for Shallow Water Acoustic Communication

Abstract

Orthogonal frequency division multiplexing (OFDM) provides an effective approach to combat multipath with high bandwidth efficiency for underwater acoustic communication, thus design and implementation of acoustic OFDM MODEMs draw more and more attention. Extensive work has been performed to mitigate multipath, Doppler shift, and peak average power ratio from the viewpoint of theoretical analysis. Meanwhile, design and implementation of a parameter-configurable OFDM to adapt to highly diverse underwater channels and various missions become more and more important. Traditional MODEM with fixed parameters cannot achieve the best tradeoff between data rate and bit error rate. In order to obtain the best communication performance under long time delay channels, Doppler channels, and frequency-selective channels, in this paper, we provide the design and implementation of a parameterconfigurable underwater acoustic OFDM MODEM with the purpose to achieve flexibility. Specifically, the reconfigurable parameters of the OFDM MODEM include the number of receivers, the number of null subcarriers, the number of pilot subcarriers, as well as the type of channel estimation algorithms. The number of pilot subcarriers and type of channel estimation methods are determined based on channel characteristics, the number of null subcarriers is determined based on the Doppler shift, and the number of the received channels is based on fading channel. Moreover, in this paper, the Doppler estimation performance under different number of null subcarriers, and the channel estimation performance under different number of pilot subcarriers and under different channel estimation algorithms, are analyzed in terms of bit error rate. Finally, the effectiveness of the proposed highly configurable OFDM MODEM is demonstrated by two sea trials corresponding to different communication scenarios. INDEX TERMS Shallow water acoustic communication, underwater acoustic OFDM MODEM, hardware and software design, parameter-configurable MODEM.

Sound Velocity Estimation of Seabed Sediment Based on Parametric Array Sonar

“…It can be seen from equations (1)- (2) and 7that the accurate thickness of the sediment is related to the sound velocity between the layers of sediment. erefore, when the actual sound velocity in the sediment is obtained, the stratum structure of the sediment can be accurately detected.…”

“…Geoacoustic parameters of submarine sediments are the basis of shallow sea communications, seabed resource detection, and other seabed scientific research studies [1][2][3][4]. In the traditional seabed sediment detection, the problem of the coupling between sediment depth and sound velocity cannot be solved [5].…”

Design of a General Hardware in the Loop Underwater Communication Emulation System

“…With the increasing demand for high-speed transmission of underwater voice and image, traditional modulation and demodulation technology can no longer adapt to such highspeed information transmission [8]. In recent years, Orthogonal Frequency Division Multiplexing (OFDM) technology has been gradually applied into underwater communication system because it can divide the limited spectrum, improve the spectrum utilization rate, and ensure high-speed data transmission.…”

“…Hai Yan, Lei Wan, Shengli Zhou et al have developed the underwater acoustic communication system based on SISO-OFDM and MIMO-OFDM on the floatingpoint TMS320C6713 DSP development kit [9]. Y. Zhou and F. Tong [8] has developed an underwater acoustic modem based on OFDM modulation in OMAP-L138. The system has a communication distance of 1km and a transmission rate of 4kbps.…”

Analytical Performance Evaluation of GFDM in Underwater Acoustic Communication Systems

“…Studies that can be found in the literature about acoustic modems include: Location algorithms [14,15], channel estimation [16,17], performance analysis [18,19], and implementation techniques [20,21]. At this point, it is important to note that most of these and other studies [22,23] consider the use of the Orthogonal Frequency Division Multiplexing (OFDM) as the main waveform for transmitting the information.…”