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The use of orthogonal waveform can offer many advantages in covert underwater acoustic communication, including improved symbol detection ability. In this paper, we derive a new orthogonal code design. The proposed code has a good autocorrelation property compared to other codes. We present some results of a lake trial to evaluate the performance of the proposed method.
Underwater acoustic channels usually suffer from the extended multipath propagation which causes inter symbol interference (ISI). At the receiving end, serious ISI would result in the decrease of the reliability of underwater acoustic communication systems. In this paper, Turbo equalization is applied to increase the reliability of communication systems. The realization of the channel equalizer in...
Blind channel estimation methods normally use the statistical properties of received signals to restore the original waveform without a priori information. However, these methods need a high computational complexity especially in multipath environments, and their performances are not good enough. A blind channel estimation method utilizing acoustic propagation physics via normal mode is proposed in...
A novel code division multiple access (CDMA) using cyclic shift keying (CSK) signaling, namely CSK-CDMA, has been proposed for multiuser underwater acoustic communication. The proposed method uses the cyclic correlation characteristic of spread spectrum signals and time reversal processing to increase the data rate each user and to reduce the complexity of the receiver. In CSK-CDMA system, multiple...
Cylindrical shell transducers are widely used in underwater acoustic engineering. For example, free-flooded ring transducers are often used as transmitters in underwater acoustic communication devices. However, there are few papers about the transient sound field generated by cylindrical shell transducers in a shallow ocean. In this study, the problem of the transient sound generated by a cylindrical...
The purpose of this paper is to introduce a new beamforming method for sonar imaging, which is proposed based on the plane wave decomposition combine with back-propagation method and with transverse oscillations. This method was initially proposed for ultrasound Doppler imaging using transverse oscillations in linear geometry. The plane wave decomposition theory is used to decompose in different directions...
A direct-adaption based bidirectional turbo equalizer (DA-BTEQ) is proposed for multiple-input multiple output (MIMO) underwater acoustic (UWA) communications. Abandoning the traditional channel estimation process, the proposed DA-BTEQ works in a direct-adaption mode and is implemented with bidirectional soft-decision feedback equalizer (SDFE) to suppress error propagation. The diversity gain is exploited...
Dolphins have a very powerful sonar system for finding food, communicating with each other and escaping from predators. Recently there has been an increasing research interest on dolphin sonar signals. For most wild dolphins, e.g., Chinese white dolphins (Sousa chinensis), the recorded sound signal is a combination of the dolphin's bioacoustic signal and the effect of a multipath shallow-water acoustic...
In-band full duplex (IBFD) can theoretically double the throughput of communication systems, and its feasibility has been demonstrated in wireless radio design. It is a promising alternative for the severely bandwidth-limited underwater communication system since it exploits both the temporal and spectral efficiency to the most. Self-interference cancelation is the primary challenge in IBFD's implementation...
Multicarrier code-division multiple-access (MC-CDMA) is considered to be a very promising and suitable scheme for underwater acoustic networking communication systems due to its high spectrum utilization efficiency, strong anti-multipath interference ability, and prominent multiple access ability. In this paper, we propose a multi-objective transmission power allocation scheme based on genetic algorithm...
Bearing-time-record (BTR) is widely used in sonar signal processing as an important display formats which may benefit the subsequent processing. The general way to get a BTR display is to parallel the outputs of the beamformer along time axis. This paper proposes a method to generate the BTR display which uses the L1 norm regularization and the total variation (TV) regularization to enhance the point-based...
The past few years have witnessed a significant progress in research of underwater acoustic networks. Some MAC and routing protocols tailored for underwater acoustic networks have been proposed. However, it is difficult and costly to build real underwater network systems as well as conduct field experiments, and most researches are based on theoretical analysis and simulations. To facilitate evaluating...
Recently, underwater acoustic communication system has been received a great interest due to its wide application areas. Since acoustic modem is one of the core technologies for underwater communication systems, there have been many efforts to improve the performance of acoustic modem in terms of data rate, working range, power consumption, size and cost by utilizing state-of-the-art physical layer...
Underwater speech communication plays an important role in many marine missions, such as oceanographic investigation, environmental monitoring, underwater rescuing and sightseeing. However, the difficulties of underwater acoustic channels such as multipath, time varying and Doppler shifting pose significant challenges to the design of high performance underwater acoustic speech communication. In this...
Multicarrier code division multiple access (MC-CDMA) can be applied in underwater acoustic communication networks to combat the narrow bandwidth of the underwater acoustic channel and multipath fading. Power control is one of the key technologies for the MC-CDMA communication networks. In this paper, we propose a multi-objective power control scheme based on improved particle swarm optimization (PSO)...
The high frequency Chirp signal in underwater acoustic communication usually submerged in various noise produced by ocean waves, ships, etc. In this paper, based on the principle of stochastic resonance for weak signal detection, the extraction and energy enhancement of high frequency weak signal are achieved by using bistable stochastic resonance system. The genetic algorithm is additionally used...
Underwater acoustic (UWA) channel was one of the most complex wireless communication channel because of extensive multipath problem. Multipath problem will lead to severe inter-symbol interference (ISI) and frequency selective fading. To build a reliable high rate UWA communication system in multipath environment, Sweep-Spread Carrier (SSC) system based on Virtual Time Reversal Mirror (VTRM) was introduced...
Given a middle-scale underwater acoustic network, to collect data from the multiple underwater nodes, the surface destination node need to be working on mobile data collection mechanism. In this paper, compared to traditional automatic-repeat-request (ARQ) protocol, we proposed node cooperation (NC) to increase the data collection efficiency for the surface node, utilizing the fact that underwater...
Based on Gibbs sampling technology, this paper puts forward a new semi-blind joint channel estimation and equalization algorithm that used in signal carrier coherent underwater acoustic communication system. First of all, we estimate the channel by using the train sequence with a loop structure before the data, and according to the sparse characteristics of underwater acoustic channel, this paper...
Unmanned Surface Vehicle (USV) is a novel kind of oceanic platforms, which is potential to be an effective platform for acoustic applications. Active and passive underwater acoustic experiments using our USV called USBV at Ji-hong-tan reservoir in Qingdao on July 15–17, 2015 and at Wu-zhi-zhou Island in the South China Sea on January 3–6, 2016 are presented to quantify this potential. The acoustic...
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