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Proceedings ArticleDOI

The WHOI micro-modem: an acoustic communications and navigation system for multiple platforms

18 Sep 2005-pp 1086-1092
TL;DR: The micro-modem is a compact, low-power, underwater acoustic communications and navigation subsystem which has the capability to perform low-rate frequency-hopping frequency-shift keying, variable rate phase-coherent keying and two different types of long base line navigation, narrow-band and broadband.
Abstract: The micro-modem is a compact, low-power, underwater acoustic communications and navigation subsystem. It has the capability to perform low-rate frequency-hopping frequency-shift keying (FH-FSK), variable rate phase-coherent keying (PSK), and two different types of long base line navigation, narrow-band and broadband. The system can be configured to transmit in four different bands from 3 to 30 kHz, with a larger board required for the lowest frequency. The user interface is based on the NMEA standard, which is a serial port specification. The modem also includes a simple built-in networking capability which supports up to 16 units in a polled or random-access mode and has an acknowledgement capability which supports guaranteed delivery transactions. The paper contains a detailed system description and results from several tests are also presented
Citations
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Journal ArticleDOI
TL;DR: There are no standardized models for the acoustic channel fading, and experimental measurements are often made to assess the statistical properties of the channel in particular deployment sites, but the channel capacity depends on the distance, and may be extremely limited.
Abstract: Acoustic propagation is characterized by three major factors: attenuation that increases with signal frequency, time-varying multipath propagation, and low speed of sound (1500 m/s). The background noise, although often characterized as Gaussian, is not white, but has a decaying power spectral density. The channel capacity depends on the distance, and may be extremely limited. Because acoustic propagation is best supported at low frequencies, although the total available bandwidth may be low, an acoustic communication system is inherently wideband in the sense that the bandwidth is not negligible with respect to its center frequency. The channel can have a sparse impulse response, where each physical path acts as a time-varying low-pass filter, and motion introduces additional Doppler spreading and shifting. Surface waves, internal turbulence, fluctuations in the sound speed, and other small-scale phenomena contribute to random signal variations. At this time, there are no standardized models for the acoustic channel fading, and experimental measurements are often made to assess the statistical properties of the channel in particular deployment sites.

1,493 citations

Journal ArticleDOI
TL;DR: The conclusion is that building scalable mobile UWSNs is a challenge that must be answered by interdisciplinary efforts of acoustic communications, signal processing, and mobile acoustic network protocol design.
Abstract: The large-scale mobile underwater wireless sensor network (UWSN) is a novel networking paradigm to explore aqueous environments. However, the characteristics of mobile UWSNs, such as low communication bandwidth, large propagation delay, floating node mobility, and high error probability, are significantly different from ground-based wireless sensor networks. The novel networking paradigm poses interdisciplinary challenges that will require new technological solutions. In particular, in this article we adopt a top-down approach to explore the research challenges in mobile UWSN design. Along the layered protocol stack, we proceed roughly from the top application layer to the bottom physical layer. At each layer, a set of new design intricacies is studied. The conclusion is that building scalable mobile UWSNs is a challenge that must be answered by interdisciplinary efforts of acoustic communications, signal processing, and mobile acoustic network protocol design.

732 citations


Cites background from "The WHOI micro-modem: an acoustic c..."

  • ...Among the four types of sensor activities (sensing, transmitting, receiving, and computing), transmitting is the most expensive in terms of energy consumption (In WHOI Micro-Modem [8], the transmit power is 10 Watts, and the receive power is 80 milliwatts....

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Journal ArticleDOI
TL;DR: Key applications and the main phenomena related to acoustic propagation are summarized, and how they affect the design and operation of communication systems and networking protocols at various layers are discussed.
Abstract: This paper examines the main approaches and challenges in the design and implementation of underwater wireless sensor networks. We summarize key applications and the main phenomena related to acoustic propagation, and discuss how they affect the design and operation of communication systems and networking protocols at various layers. We also provide an overview of communications hardware, testbeds and simulation tools available to the research community.

728 citations


Additional excerpts

  • ...Underwater Sensor Networks: Applications, Advances, and Challenges...

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Journal ArticleDOI
TL;DR: The authors aim to provide an overview, spanning this decade, of key underwater networking protocol and point-to-point communication technique developments.
Abstract: There has been a growing interest in underwater acoustic communications over the past 30 years because of its defense, offshore oil industry, marine commercial operations, oceanography, and marine research applications. As compared to initial communication systems, improved performance and robustness have resulted from continued research over the years. The authors aim to provide an overview, spanning this decade, of key underwater networking protocol and point-to-point communication technique developments. Insight into some of the open challenges and problems researchers in this field will face in the near future is also provided by the authors.

585 citations


Cites background or methods from "The WHOI micro-modem: an acoustic c..."

  • ...AUVs are sometimes equipped with multiple modems or a single modem with multiple frequency band transducers (Freitag et al., 2005)....

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  • ...The WHOI micro-modem supports a NMEA 0183 protocol (Freitag et al., 2005)....

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  • ...The physical layer of the WHOI micro-modem was published as a standard (Freitag and Singh, 2000) and a commercial modem maker Benthos implemented compatible modems (Freitag et al., 2005)....

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Proceedings ArticleDOI
25 Sep 2006
TL;DR: This survey highlights a number of important practical issues that have not been emphasized in recent surveys of underwater networks, with an intended audience of researchers who are moving from radio-based terrestrial networks into underwater networks.
Abstract: Underwater sensor networks are attracting increasing interest from researchers in terrestrial radio-based sensor networks. There are important physical, technological, and economic differences between terrestrial and underwater sensor networks. Previous surveys have provided thorough background material in underwater communications, and an introduction to underwater networks. This has included detail on the physical characteristics of the channel [1], on underwater acoustic communications [2, 3, 4], and surveys of underwater acoustic networks [5, 6, 7, 8]. In this survey, we highlight a number of important practical issues that are not emphasized in the recent surveys of underwater networks, with an intended audience of researchers who are moving from radio-based terrestrial networks into underwater networks. We focus on issues relevant to medium access control (MAC) protocols, which are an area of continuing work both in terrestrial sensor networks and especially in underwater networks. Underwater networks are often characterized by more expensive equipment, higher mobility, sparser deployments, and different energy regimes when compared with terrestrial sensor networks. We discuss the role of these factors in the different set of challenges that face underwater networks. We identify several of these points in the outline below, and we expand upon them in later sections. In Section 2, we provide a classification scheme for underwater networks. Link-layer range, node density, and geographic coverage of nodes are key factors in determining the type of network deployed. The key differentiating factor for underwater net-

573 citations


Cites background from "The WHOI micro-modem: an acoustic c..."

  • ...2W to detect, 2W during equalization and decoding) [67]....

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References
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Proceedings ArticleDOI
05 Nov 2001
TL;DR: Integrated acoustic communication and navigation for underwater vehicles provides dual functionality in a single system which reduces cost, size, power and potential acoustic interference.
Abstract: Integrated acoustic communication and navigation for underwater vehicles provides dual functionality in a single system which reduces cost, size, power and potential acoustic interference. A combination of time and code division multiplexing is used to allow long baseline navigation and bidirectional communication for a number of vehicles operating simultaneously in the same area. The communication system uses multi-rate phase coherent modulation to maximize throughput for the uplink from a vehicle to a central node, and code-division multiple-access using a simple frequency-hopping scheme. The data rate and modulation methods are completely programmable and may be selected based on the application requirements and the propagation conditions present between the different vehicles in the network. While one or several vehicles may use time-multiplexed long-baseline (LBL) navigation, when the number of vehicles grows large, the time between fixes becomes unacceptably long. Thus in addition to LBL, a second mode of navigation is also available for use with swarms of vehicles such as the surf-zone crawlers proposed for mine counter-measure applications. This second mode employs navigation broadcasts initiated by the central controller and incorporates three additional fixed nodes that transmit in response. The time differences of arrival measured at the vehicle are used to determine its location.

65 citations


"The WHOI micro-modem: an acoustic c..." refers background in this paper

  • ...The first description of the network capability was described in [1]....

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Proceedings ArticleDOI
20 Jun 2005
TL;DR: A buoy-based observatory that uses acoustic communication to retrieve data from water column and seafloor instruments has been developed and deployed in 2362 m of water offshore Vancouver Island as discussed by the authors.
Abstract: A buoy-based observatory that uses acoustic communication to retrieve data from water column and seafloor instruments has been developed and deployed in 2362 m of water offshore Vancouver Island. The system uses high-rate (5000 bps) acoustic modems that are power-efficient (on order 1000 bits per joule) to telemeter data from an ocean bottom seismometer and a sensor monitoring a cold seep site near the Nootka fault. The buoy includes a Linux-based embedded controller, the modem base station and meteorological sensors. Data is off-loaded from the buoy using ftp, and remote login capability allows the acoustic communication schedule to be modified when instruments are added or removed from the network. The system has been operational for one year, typically transferring more than 500 Kbytes of data per day from two seafloor instruments.

25 citations


"The WHOI micro-modem: an acoustic c..." refers methods in this paper

  • ...Figure 12 shows the location of the plates and faults in the North East Pacific....

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  • ...The system was deployed and operated for more than a year on the Nootka Fault, in the northeast Pacific [5]....

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Proceedings ArticleDOI
01 Sep 2003
TL;DR: Test results proved that the fusion reliably classified bottom mine-like objects while significantly reducing the false alarm rate relative to that of a single CAD/CAC algorithm.
Abstract: The fusion of multiple computer aided detection/computer aided classification (CAD/CAC) algorithms has been shown to be effective in reducing the false alarm rate associated with the automated classification of bottom mine-like objects when applied to side-scan sonar images taken in the littoral environment Real-time operation of the CAD/CAC fusion algorithms from Raytheon, Lockheed Martin, and NSWC Coastal Systems Station (CSS) on board an unmanned underwater vehicle has recently been successfully demonstrated as part of a littoral test sponsored by the Office of Naval Research (ONR) in 2002 Test results proved that the fusion reliably classified bottom mine-like objects while significantly reducing the false alarm rate relative to that of a single CAD/CAC algorithm This paper discusses the hardware and software architecture for the real-time implementation of the CAD/CAC algorithms, and presents the real-time performance results obtained during the experiment Additional post processing performance results are also discussed for alternate fusion approaches, and the overall performance benefit through a significant reduction of false alarms at high correct classification probabilities is quantified

21 citations