Error tolerant dual-hydrophone localization in underwater sensor networks

Underwater sensor network nodes typically detect and communicate through the propagation of acoustic waves. To localize an unknown noise-source with an underwater sensor network, one can combine bearing estimates from various sensors while taking into account their respective position. As the battery life of each underwater sensor dictates the overall network endurance, each sensor must make sense of the various propagated signals and derive a likely bearing estimate to pass to neighbouring nodes while consuming as little power as possible. Most publications presenting distributed noise-source localization approaches performed by underwater sensor networks are inadequate in that their assumptions do not usually apply to an underwater setting and only use simulated scenarios. Unlike these publications, the proposed distributed noise-source localization scheme is tailored to and tested with real underwater acoustic detections. In particular, we present simple computational schemes for the sake of extending the operational life of the overall network. Those schemes monitor and estimate the main bearing characteristics while simplifying their representation. In general, the proposed techniques outperform the traditional approach of selecting bearings based on an intensity-only threshold.

Underwater sensor networks (UWSN) are widely used in many applications, such as oceanic resource exploration, pollution monitoring, tsunami warnings and mine reconnaissance. In UWSNs, determining the location information of each sensor node is a critical issue, because many services are based on the localization results. In this paper, we introduce a novel underwater localization approach based on directional signals, which are transmitted by an autonomous underwater vehicle (AUV). Our method utilizes directional beacons (UDB) to replace traditional omni-directional localization which provides more accurate and efficient ways to locate the sensors themselves by simple calculations. The advantage of this novel scheme is that the communications between AUV and sensors are not necessary because the AUV broadcasts signals and sensors only need to passively listen to the signals. Since the energy consumption for transmissions in underwater environments is a nontrivial factor, our localization scheme not only supports accurate positioning, but also reduces energy consumption of sensors. We evaluate our scheme by simulations. The results show that our new approach is very precise in a strap area. At the same time, we minimize the number of beacons issued from the AUV.

We propose a localization scheme for underwater acoustic sensor networks (UWSN) that does not require a priori infra-structure or synchronization between nodes. An autonomous underwater vehicle (AUV) aids in localizing the sensor nodes while roaming across the underwater sensor field. The objectives of this paper are to describe how to localize nodes using AUV and to describe the tradeoffs involved, i.e. ratio of localized nodes and localization accuracy. We show that localization success improves as the duration of the AUV localization process increases. In addition, we investigated localization using two methods, bounding-box and triangulation. The former achieves a higher localization ratio but with a higher error. In certain scenarios, we achieved 100% nodes localized with 3% error.

Underwater Sensor Networks (UWSNs) are significantly different from terrestrial sensor networks in the following aspects: low bandwidth, high latency, node mobility, high error probability, and 3-dimensional space. These new features bring many challenges to the network protocol design of UWSNs. The communication range of underwater wireless sensor networks (UWSNs) is limited, and the nodes are equipped with limited power battery whose replacement is expensive due to underwater harsh environment. Moreover, the networks including small number of nodes have communication problems for long ranges. In this paper, we evaluate the performance of three classical location-based routing protocols (namely, VBF, HH-VBF, and VBVA) for underwater wireless sensor networks in terms of three critical performance metrics for dynamic network topology. Our comparison includes energy consumption, end-to-end delay, and packet delivery ratio.

Underwater sensor networks are physical networks containing acoustic,magnetic,and static electric field.It has got widely application in ocean data acquisition,pollution forecasting,ocean exploitation,and ocean supervision.And in future it will show its advantages in the battlefield.The state-of-the-art underwater wireless sensor networks are overviewed,and several typical structures of underwater wireless sensor networks are also described.Taking account of the requirements of underwater applications several fundamental key aspects in the design of underwater sensor networks,such as node localization,energy,source localization and other challenges are investigated.Finally open issues in underwater sensor networks are discussed.

Packet collision in underwater wireless sensor networks (UWSNs) can create inconsistent time stamps leading to inaccurate time synchronization in underwater sensor networks. Most extant time synchronization techniques do not model for the probability of packet collision in UWSNs. This paper proposes a novel non-homogenous Poisson process (NHPP)-based back-off technique that estimates probability of packet collision in UWSN over a set period of time and allows sending of data packets only when probability of collision in a network is low. Any inconsistent time stamps are further identified and removed using Mahalanobis distance technique before linear regression is run. The proposed method performs better in extensive simulations as compared to two similar time synchronization techniques in literature.KeywordsUWSNsNon-homogenous Poisson processPacket collisionTime synchronization

This paper proposes cooperative routing algorithms to improve the performance of underwater acoustic sensor networks (UW-ASNs). With the consideration of the poor acoustic link quality, a cross-layer design of physical layer and network layer is described for selecting simultaneously routing relays (RR) for forwarding data on routing paths and cooperative relays (CR) for one-hop cooperative communications. In the networks, sources that have data to transmit independently selects their own relays (i.e., both RR and CR) among their neighbors based on their link quality indicators (i.e., signal-to-noise ratio (SNR), time of arrival (ToA)) and their physical distances represented by hop count (HC) to the destination. Exploiting packet receiving or overhearing in the networks, these parameters are averaged and updated frequently to adapt to the unreliable and varying characteristics of acoustic channel over the time. By this way, the "best" relays with the "best" estimated measurements are selected reliably. Our simulation results show that the proposed algorithms improve the network performance in terms of end-to-end delay, energy consumption and packet delivery ratio.

Owing to the rapid development of underwater applications, the research on underwater wireless sensor networks (UWSNs) is becoming more and more significant. Low bandwidth, high latency, limited energy and node float mobility are basic challenges for underwater sensor networks. Most of the theories for terrestrial sensor networks can not be applied to underwater sensor networks. In this paper, we focus on the localization and routing issues for dynamic UWSNs. Location based routing protocols can suit the dynamic situation of UWSNs well. However, most research assumes that the nodes know their locations, which may be not appropriate for some applications. This paper combines these two aspects together to design a localization based routing protocol for dynamic UWSNs. The simulation results show our method can effectively route data from the source nodes to the sink nodes in a dynamic environment.

Underwater wireless sensor networks nodes deployment optimization problem is studied and underwater wireless sensor nodes deployment determines its capability and lifetime. If no underwater wireless sensor node is available in the monitoring area of underwater wireless sensor networks due to used up energy or any other reasons, the monitoring area where is not detected by any underwater wireless sensor node forms coverage holes. In order to improve the coverage of the underwater wireless sensor networks and prolong the lifetime of the underwater wireless sensor networks, based on the perception model, establish nodes detection model, combining with the data fusion. Because the underwater wireless sensor networks nodes coverage holes appear when the initial randomly deployment, a nodes deployment algorithm based on perception model of underwater wireless sensor networks is designed in this article. The simulation results show that this algorithm can effectively reduce the number of deployment underwater wireless sensor networks nodes, improve the efficiency of underwater wireless sensor networks coverage, reduce the underwater wireless sensor networks nodes energy consumption, prolong the lifetime of the underwater wireless sensor networks.

Water covers more than 70 % of the entire planet, contains much of its natural resources. With the increasing use of underwater sensors for the exploitation and monitoring of vast underwater resources, underwater wireless sensor network (UWSN), mostly based on acoustic transmission technologies, have been developing steadily in terms of operation range and data throughput. In an energy-constrained underwater system environment it is very important to find ways to improve the life expectancy of the sensors. Compared to the sensors of a terrestrial Ad Hoc Wireless Sensor Network (WSN), underwater sensors cannot use solar energy to recharge the batteries, and it is difficult to replace the batteries in the sensors. This paper reviews the research progress made to date in the area of energy consumption in underwater sensor networks (UWSN) and concentrates on developing routing algorithms that support energy efficiency. These algorithms are designed to carry out data communication while prolonging the operation time of WSNs.

Study Framework: The system of geographical information (GIS) is a computerized method for collecting, storing, disseminating, querying, updating, processing and analyzing geographic data. (GIS) enables the collection of diverse spatial data from various sources and transforms it into an information board for multiple users to boost productivity. Intelligent techniques, remote sensing, and underwater Wireless sensor networks are applied to improve GIS dramatically. Remote sensing data sources for GIS come from underwater sensor networks, The implementation of effective sensing devices, intelligent mobile nodes, and a multi-hop routing system can facilitate the efficient and optimal routing of traffic towards the basin or base station. They have been using GIS, which has revolutionized response scenarios with its ability to collect, analyze and manipulate spatial points. The objective of the study: The aim of this research is to differentiate the significant routing protocol issues that are relevant to underwater sensor networks. These networks serve as key transceivers that have established mechanisms for seamless and efficient data transmission. The mechanisms: The article presented a performance evaluation simulation based on a comparison of five different routing protocols that perform to promote GIS execution. A rigorous comparison of the outcomes varied by five routing protocols, where it evaluated with random mobility UnderWater sensor model based on the varied network parameters, was performed to validate this work. The continued to improve results: The suggested study in this manuscript contains spatial-information services universal to routing protocols to aid a group of navigators in harsh circumstances. According to the findings of the study, the CTP-ABS-SEEC routing protocol demonstrated superior performance compared to the other four routing protocols (CTP-SEEC, SEEC, EEDBR, and DBR) in the specified network configuration.

This paper explores energy-efficient ways of retrieving data from underwater sensor fields using autonomous underwater vehicles (AUVs). Since AUVs are battery-powered and therefore energy-constrained, their energy consumption is a critical consideration in designing underwater wireless sensor networks. The energy consumed by an AUV depends on the hydrodynamic design, speed, on-board payload and its trajectory. In this paper, we optimise the trajectory taken by the AUV deployed from a floating ship to collect data from every cluster head in an underwater sensor network and return to the ship to offload the data. The trajectory optimisation algorithm models the trajectory selection as a stochastic shortest path problem and uses reinforcement learning to select the minimum cost path, taking into account that banked turns consume more energy than straight movement. We also investigate the impact of AUV speed on its energy consumption. The results show that our algorithm improves AUV energy consumption by up to 50% compared with the Nearest Neighbour algorithm for sparse deployments.

DAP-MAC: A delay-aware probability-based MAC protocol for underwater acoustic sensor networks

Underwater sensor networks (UWSNs), the enabling technology for a broad range of aquatic applications, rely on acoustic communication for long-range transmissions. However, underwater acoustic communication suffers from several adverse features, such as long propagation delay and low bandwidth, making the networking design for UWSNs much more challenging than their terrestrial counterparts. Medium access control (MAC), a crucial component in networking design, coordinates among multiple agents that share the same channel resource and is responsible to schedule packet transmissions efficiently and fairly. However, due to the long propagation delay, the traditional handshaking-based random-access MAC protocols are not channel efficient for UWSNs.

Underwater sensor networks will find many oceanic applications in near future, and the topology recovery problem in 3D sensor networks has not been paid enough attention at present. In order to maximize the network lifetime, a topology recovery algorithm (UTR) for underwater sensor networks in ocean environment is proposed. UTR will restore connectivity by amplifying the communication power of nodes around failure region as far as possible, and migrate AUVs to recovery topology when necessary. The simulation results suggest UTR can extend the UWSN lifetime effectively.