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The exchange of information in Wireless Sensor Networks (WSNs) across different environments, whether they are above the ground, underground, underwater, or in space has advanced significantly over time. Among these advancements, precise localization of nodes within the network remains a key and vital challenge. In the context of Underwater Wireless Sensor Networks (UWSNs), localization plays a pivotal role in enabling the efficient execution of diverse underwater applications such as environmental monitoring, disaster management, military surveillance and many more. This review article is focusing on three primary aspects, the first section focuses on the fundamentals of localization in UWSNs, providing an in depth and comprehensive discussion on various localization methods. Where we have highlighted the two main categories that are anchor based and anchor free localization along with their respective subcategories. The second section of this article examines the diverse challenges that may emerge during the implementation of the localization process. To enhance clarity and structure, these challenges have been carefully analyzed and categorized into three main groups and that are, (i) Algorithmic challenges, (ii) Technical challenges, and (iii) Environmental challenges. The third section of this article begins by presenting the latest advancements in UWSNs localization, followed by an exploration of how Machine Learning (ML) and Deep Learning (DL) models can contribute in enhancing the localization process. To evaluate the potential benefits of the ML and DL techniques, we have assessed their performance through simulations, focusing on metrics such as localization error, velocity estimation error, Root Mean Square Error (RMSE), and energy consumption. This review also aims to provide actionable insights and a guideline for future research directions and opportunities for practitioners in the field of UWSNs localization. Which will ultimately help in enhancing the performance and reliability of underwater applications by advancing localization techniques and promoting seamless integration. [ABSTRACT FROM AUTHOR]

The underwater wireless sensor networks (UWSNs) area is a developing area of research since there are tremendous opportunities like surveying marine life, installing and monitoring optical cables, detecting earthquakes, and surveillance of territorial borders. Though many applications exist, underwater research explored to date is less than five percent as it poses many issues and challenges like water currents, temperature, pressure, water salinity, disturbance by aquatic animals, and many more factors that affect the performance of sensors deployed inside water. A significant issue UWSNs face is focusing on energy efficiency to extend the life of submerged sensors placed in isolated areas. Resolving localization concerns is a primary additional concern. In this comprehensive survey, the basics of UWSNs are covered in the introduction, followed by a thorough literature review of the existing works mainly focusing on localization, energy efficiency, Bio-inspired algorithms (BIA), and the impact of implementing Machine Learning (ML) are discussed. In concurrent sections, we have discussed attributes, parameters useful for analysis, issues and challenges in UWSN, soft computing techniques, software and hardware tools available for extended research, and opportunities in UWSN. The researchers could gain perspective pathways at the end of this survey.Article highlights: Architectures, Applications, Issues, and Challenges of UWSN are mentioned in detail. Range-based, Range-free algorithms for Localization and various Energy Efficiency algorithms are analyzed. PSO, Artificial fish swarm optimization, Hybrid grass hopper algorithm, Firefly, Dolphin swarm, and twenty-three other Bio-inspired optimization algorithms are reviewed. [ABSTRACT FROM AUTHOR]

In Underwater Wireless Sensor Networks, ensuring precise localization of sensor nodes is crucial. Existing localization algorithms heavily rely on pre-deployed and known anchor nodes to compute and determine the positions of other nodes. However, anchor nodes may be compromised or misled in practical scenarios, resulting in localization inaccuracies. To address this challenge, a proficient iterative localization algorithm is proposed in Garg and Varna (IEEE Trans Inf Forensics Secur 7: 717–730, 2012), which selects known nodes as reference anchors to locate unknown nodes and analyzes their performance under non-collaborative attacks. Therefore, a novel localization algorithm is introduced to counter collaborative attacks, utilizing time difference of arrival ranging mapping and selective minimum gradient principles from the AdaDelta Gradient Descent (AGD) algorithm to iteratively eliminate deceptive information transmitted by interfering nodes, thereby enhancing localization accuracy. Validations demonstrate its efficacy in combating collaborative network attacks under certain conditions and significantly improving localization performance. Simulation experiments confirm its robustness even under network attacks, ensuring the reliable operation of UWSNs. [ABSTRACT FROM AUTHOR]

For efficient monitoring of marine environments using underwater wireless sensor networks (UWSNs), a fundamental issue is to maximize network coverage as well as connectivity by appropriate deployment of the nodes within a given sensing area. Most of the existing node deployment schemes proposed for UWSNs, assume that sensor nodes are static and their location after deployment are fixed. However, due to ocean current and the contact of the underwater creatures, these deployed static sensor node moves from its original locations to other locations, which disrupts the network connectivity with the base stations as well as most of the targets remain uncovered. To find a solution to this issue, authors propose a coverage and connectivity aware deployment scheme for optimal placement of a set of autonomous underwater vehicles (AUVs) within UWSNs. The proposed scheme uses an improved Non-dominated Sorting Genetic Algorithm-II based metaheuristic technique with a novel fitness function which contains three parameters namely coverage quality, connected cost and network lifetime. Further, proposed scheme applies an effective encoding scheme for the population representation and devises a novel fitness function for upgrading the quantity of the AUVs as well as their location. Performance estimation of the proposed scheme and its comparison with the existing schemes with respect to convergence rate, coverage quality, connected cost, average energy consumption and network lifetime are discussed in detail. The simulation outcome confirm that the proposed approach upgrades the coverage of the network. [ABSTRACT FROM AUTHOR]

The stratification effect underwater can lead to the localization errors in underwater acoustic sensor network. In order to compensate the stratification effect and improve the localization accuracy, we propose a localization algorithm based on the improved particle swarm optimization. Firstly, instead of approximating seawater as a homogeneous medium, this paper builds the layered medium model. Then the ray theory method is employed to compensate stratification effect. And the ranging with compensating for stratification effect is analyzed. Based on the ranging, the particle swarm optimization is improved to introduced into localization. Lastly, the optimal position of unknown nodes in underwater acoustic sensor network is obtained. Simulation results show that the proposed algorithm can effectively compensate the stratification effect and improve localization accuracy. [ABSTRACT FROM AUTHOR]

The balance energy consumption of nodes is a key factor to prolong network lifetime. A sensor node in Underwater Wireless Sensor Networks (UWSNs), has very limited power battery, therefore, utilizing the power battery in efficient manner is still a challenging task. To enhance network lifetime, we proposed an Energy-Efficient Regional base Cooperative Routing (EERBCR) protocol with sink mobility for UWSNs. In EERBCR, we divided the network field in 12 regions, three by four vertically and horizontally respectively. Total numbers of four mobile sinks are positioned, having equal distance to each other while 100 sensors nodes are deployed randomly. Each mobile sink travels on pre-defined straight path and covers 3 regions. All the sensor nodes are in sleeping mode, until the sink arrives to their region, upon the arrival of sink node to a region, it broadcasts a hello message. All the nodes in that region receive that message and activate themselves. When the sink is about to leave the region, it broadcasts another packet, informing the nodes about its departure so that the nodes go back into sleeping mode. The simulation results show the validity of EERBCR as it performed better than Depth-Based Routing (DBR), Energy Efficient Depth-Based Routing (EEDBR) and depth and energy-aware dominating set (DEADS) protocols. [ABSTRACT FROM AUTHOR]

The Underwater Internet of Things (UIoT) has emerged as one of the prominent technologies in the development of future ocean monitoring systems, where mobile edge elements (such as autonomous underwater vehicles (AUVs)) provide a promising method for the data collection from sensor nodes. However, as an important part of the UIoT, underwater wireless sensor networks (UWSNs) are severely affected by the underwater dynamic environment. For instance, node locations change continuously, which significantly increases the difficulty of data collection. To solve this problem, the concept of an inevitable communication space (ICS) is proposed. The ICS is calculated by analyzing the variation in the position of nodes and the communication range. Furthermore, an ICS-based dynamic data collection algorithm (ICS-DDCA) for UIoT is proposed to collect underwater data. This method utilizes the ICS instead of the initial location of the node for data collection to further improve the performance of the algorithm and shorten the data collection time. The simulation results demonstrate that compared with the energy-efficient data collection over AUV-assisted (EEDA) and data collection algorithms based on probabilistic neighborhood (PNCS-GHA), ICS-DDCA can effectively reduce the collection time, while ensuring the full completion of data collection. [ABSTRACT FROM AUTHOR]

In underwater wireless sensor networks, distance-related localisation technologies rely on acquiring distance information between nodes to complete node location. Currently, ranging algorithms generally have the problems of high energy consumption and low accuracy. Therefore, a new ranging algorithm is proposed. In this algorithm, an information transmission mechanism is designed to transmit ranging information efficiently. Based on this mechanism, when the network clock is asynchronous, the information propagation time between nodes is obtained by a small number of asymmetric information sending and receiving operations. Furthermore, a selection method for the master beacon node is designed to balance the energy consumption of the nodes. To solve the problem of signal propagation path non-linearity caused by stratification effect, a signal emergence angle fast iterative method based on the known sound speed profile information is developed to calculate the distance between nodes. Simulation experiments demonstrate that the proposed algorithm is better than other state of the art algorithms in terms of energy consumption and network lifetime. In addition, the proposed algorithm can quickly solve the signal emergence angle, effectively reduce the impact of seawater sound speed layering and has good ranging accuracy in shallow seas. [ABSTRACT FROM AUTHOR]

Underwater Wireless Sensor Network (UWSN) is a popular technique for monitoring marine environments. It consists of several acoustic channels, sink nodes, sensor nodes and base stations. Source nodes are deployed at different depth levels of oceans for monitoring purposes. Acoustic channels communicate between a source node and a sink node. After that, the information from the sink node is delivered to the base station using an RF signal. Limited Bandwidth, Energy Consumption and propagation delay are major challenges faced by UWSN. Battery consumption of sensor nodes leads to a great impact on the performance of the underwater wireless network. Void-hole occurrence and duplication of packets from sensor nodes to sink nodes increases energy dissipation and reduces the lifespan of the UWSN. Hence energy-efficient opportunistic routing with emperor penguin optimized Q learning method (EPO-Q) for UWSN was introduced to avoid the void-hole problem and reduce energy dissipation. The proposed work was implemented in the MATLAB platform and improved performance in terms of end-to-end delay, network overhead, energy consumption, accumulated propagation distance, battery power, packet loss ratio, absorption loss, throughput, energy efficiency and packet delivery ratio. [ABSTRACT FROM AUTHOR]

The location of nodes is critical in underwater wireless sensor networks (UWSNs), which is an ocean monitoring platform. UWSNs are motivated by the popular usage of localization and play a major role in several technologies that depend primarily on innovations and localization of these nodes. Underwater node localization is a critical technology that enables the deployment of a variety of underwater applications. In this study, the underwater nodes are divided into two levels. Firstly, a clock asynchronous localization system (LS-AC) for base layer's node localization is presented. In order to eradicate the original ranging strategy's dependence on active nodes and address the problem of energy consumption, LS-AC performs in-network situation-based monitoring by relying on asynchronous clocks. Secondly, we propose a backtracking search algorithm (OTKL-BSA) based on optimal topology and knowledge learning. It is used to address the issues associated with traditional algorithms' lack of diversity and the imbalance between exploration and exploitation. Thirdly, to solve the problems that the traditional gray wolf optimizer (GWO) is prone to falling into local optimal values and has a low search efficiency, this paper proposes a GWO scheme based on hunting step size (GWO-HSS). Finally, simulation results show that the proposed algorithm outperforms SLMP, MCL-MP, MP-PSO, and MGP in aspects of localization performance. [ABSTRACT FROM AUTHOR]

Underwater sensor networks (UWSN) include a set of sensor nodes equipped with limited batteries. These batteries are not rechargeable and replacement of them is difficult and costly due to difficult access and condition of the underwater environment. So, the optimization and management of energy are the most important issues for UWSNs. Many studies have been presented in this field that the most focus of them has been on improving and optimizing routing and data transmission because of the highest energy consumption for routing and sending data. While each of these studies was effective in improving energy-related issues, the need to develop an energy-efficient and reliable routing protocol for UWSNs is still under investigation. In this paper, a method called an energy-efficient grid-based routing protocol for underwater wireless sensor networks (EEGBRP) using TOPSIS technique and 3-dimensional cell division is introduced. EEGBRP is a multi-hop method which in the first step the network is divided into three-dimensional cells. In the second step head-cell nodes or gateways are selected and data routing and communication is performed in the third step. The simulation results using NS2 indicated the successful performance and significant superiority of EEGBRP compared to previous researches. This improvement for different scenarios compared to EMGGR method was 10.65% for successful delivery, 9% for the optimization of energy consumption and 8.8% for end-to-end delay. [ABSTRACT FROM AUTHOR]

The innovative concept of Internet of Underwater Things (IoUT) has a huge impact in different sectors including a small scientific laboratory, to a medium sized harbor, and to monitor vast undiscovered oceans. Internet of Underwater Things (IoUT) has become a powerful technology to support various applications such as collecting real-time aquatic information, naval military applications, maritime security, natural disaster prediction and control, archaeological expeditions, oil and gas exploration, shipwrecks discovery, water contamination, marine life observation and smart Ocean. IoUT is referred as smart intricately linked underwater objects to monitor these underwater operations. The IoUT framework incorporates several underwater communication technologies based on magnetic induction, optical signals, radio signals and acoustic waves. It is an emerging communication ecosystem which can reveal a new era of research, business and naval applications. It is a novel and vibrant paradigm for the Blue Economy sector bringing the ability to communicate autonomous underwater vehicles (AUVs), sensing, actuating and transferring this data to control centers using regular internet speeds through low cost technologies. It is anticipated to support future networking systems which can bring tremendous improvement in previous generations in terms of stable networking, high coverage, massive connectivity, low latency, high data rate and low power consumption. This study introduces the possible network framework of IoUT which is naturally heterogeneous and must be flexible enough to work under unpredicted ocean conditions. In this study, we examine channel models, routing protocols, networking topologies and simulation tools. Furthermore, we discussed recent advancements in IoUT in terms of smart devices, consumer electronics, communication and role of AUVs. In addition, edge computing, optical wireless communication (OWC), data analytics, blockchain, intelligent reflecting surfaces (IRS) and machine learning were viewed as promising techniques to support IoUT. We have dedicated a complete section to applications of IoUT. Finally, numerous open research challenges and future directions were presented. We believe this survey will be helpful to aggregate the research efforts and eliminate the technical uncertainties towards breakthrough novelties of IoUT. [ABSTRACT FROM AUTHOR]

The localization of underwater sensors is the most crucial task in underwater wireless sensor networks (UWSNs). The sensors which are situated under the water sense information from the earth and detected information is transmitted to the observing station. Although the monitoring station receives the sensed information, the data is meaningless without knowing the exact position of the sensors. So, in UWSN, localization is the major issue to be resolved. The Range-Based Whale Optimization Algorithm (WOA) is introduced in this paper to discover this issue. To evaluate the valued location of the sensors, localization error is further reduced. The localization error is reduced by applying the WOA in this work. Reproduction results exhibit that presentation measurements of the planned methodology beats that of the current work as far as limitation mistake and restriction inclusion. Besides, the proposed scheme achieves better localization coverage, delivery ratio, delay and energy consumption than the existing algorithms. [ABSTRACT FROM AUTHOR]

Acoustic modem is one of the key elements of an underwater wireless sensor network (UWSN). Compared to a terrestrial wireless sensor network (WSN), designing a UWSN is more time consuming and expensive due to harsh conditions of the aquatic environment. Commercial modems provide better characteristics, but they consume more energy and are more expensive, while research modems have exploited diverse alternatives with varying success. The main contribution of the article is a comparative analyses of commercial and research modems based on their characteristics and design constraints, in order to describe the current trends and more promising techniques. This paper is focused on the state-of-the-art underwater acoustic modems designed, developed and implemented in the last few years. Various parameters of the modems are considered and analyzed: operating range, data-rate, modulation schemes, center frequency, bandwidth, power consumption, bit error rates, etc. Finally, design challenges, which need to be addressed, are identified. This study is useful for the engineering community to comprehend the characteristics, trends and design challenges of state-of-the-art underwater acoustic communication modems. [ABSTRACT FROM AUTHOR]

In underwater wireless sensor networks, routing play a vital role in selecting an optimal path for packet forwarding. In routing scheme, most of the existing work is suffering from both load balancing and void node issue. This is due to the environmental interference, overloaded data, energy depletion, random deployment and mobility of the nodes. However, it causes loss of packet, high energy depletion and bad network quality. We have resolved this issue by implementing load balancing and void healing routing using cuckoo search optimization (CSO) scheme. In this scheme, first we placed the parent node and identify their child node within the transmission range in each level of the network. Then, we applied load balancing with priority based packet forwarding to maintain the uneven distribution of the load and reduces the end-to-end delay. Next, void healing routing with CSO scheme is addressed to recover the convex and concave void issue in the network. A novel multi-objective fitness function is also formulated for selecting the optimal number of nodes. In packet routing, each child node is responsible for receiving the packets from their neighbor nodes and transferred to the parent node. After receiving the packets at parent node, autonomous underwater vehicle is used for collecting the relevant packets from each parent node through minimum travelling time and send towards the base station. The performance evaluation of proposed scheme shows better network quality, packet delivery ratio, less energy consumption and delay over the existing solutions. [ABSTRACT FROM AUTHOR]

Fault resilient routing is a typical issue for underwater wireless sensor networks ( UWSNs ) due to contact of underwater creatures, mobility of nodes and natural disaster. In the existing studies, most of the researchers introduced routing scheme for routing the packets towards the base station through a cluster head. However, these schemes use static or mobile nodes for deployment, but nodes move from its original position to another position and get stuck in a particular region due to ocean current, natural disaster and environmental interference. Therefore, this leads to high energy depletion, link failure, disjoint path and overloaded data. To resolve this issue, we have proposed fault resilient routing based on moth flame optimization ( MFO ) scheme for transferring the packets towards the base station through autonomous underwater vehicles ( AUVs ). In this scheme, AUVs is used instead of cluster head to avoid the reclustering, overloading problem and it also feasible for large scale networks. There may be a disjoint path issue, so we have deployed additional mobile nodes with the help of AUVs within the network. Further, a novel fitness function is integrated with the MFO scheme to overcome the link failure problem. The proposed scheme is applied to select the best forwarding node for transmitting the packets towards the nearest AUVs using multi-hop acoustic links. In UWSNs , AUVs is placed to move the packets towards the BS from lower level to upper level. Performance evaluation of proposed scheme shows better result in terms of fault resilient, residual energy, network lifetime, packet delivery ratio and convergence rate than the existing scheme under the different network scenario. [ABSTRACT FROM AUTHOR]

Recently, underwater wireless sensor networks were proposed to explore underwater environment for scientific, commercial and military purposes. However, the limited energy of nodes is a challenge for underwater wireless sensor networks. To prolong the lifetime of battery-limited underwater wireless sensor networks, in this paper, a fault-tolerant topology that can effectively extend the network lifetime is proposed. Initially, the influence of node residual energy and load on node lifetime is analysed. Later the lifetime model of underwater wireless sensor networks is established, and the value range of node load adjustment coefficient satisfying network lifetime is obtained. Finally, the scale-free fault-tolerant evolution model with network lifetime optimization is built based on node residual energy and load case. In addition, simulation experiments are performed to validate performances of the new topology generated by the evolution model built. The results show that the new topology structure can balance the energy consumption of the nodes and prolong the network lifetime effectively, and has good fault tolerance. [ABSTRACT FROM AUTHOR]

Most existing works on barrier coverage assume that sensors are deployed in a two-dimensional (2D) long thin belt region, where a barrier is a chain of sensors from one end of the region to the other end with overlapping sensing zones of adjacent sensors. However, the 2D assumption cannot cover all application scenarios, e.g., underwater wireless sensor networks, where sensors are finally distributed over three-dimensional (3D) underwater environment. In this paper, we investigate weak k-barrier coverage problem in underwater wireless sensor networks. We first analyse how to determine whether a deployed underwater wireless sensor network provides 3D weak k-barrier coverage, and propose a novel and effective scheme to transform the 3D weak k-barrier coverage problem into 2D complete k-coverage problem, based on which we devise an O(n2) time algorithm for the 3D weak k-barrier decision problem. Furthermore, we propose a parallel movement manner, based on which an effective algorithm called Hungarian Method-based sensor assignment algorithm (HMB-SAA) is proposed for constructing weak k-barrier coverage while minimizing the total movement distance of all sensors in underwater wireless sensor networks. Simulation results validate the correctness of our analysis, and show that the proposed algorithm outperforms the GreedyMatch algorithm. To the best of our knowledge, this is the first result for 3D weak k-barrier coverage problem in underwater wireless sensor networks. [ABSTRACT FROM AUTHOR]

The imbalance energy consumption and high data traffic at intermediate nodes degrade the network performance. In this paper, we propose: energy grade and balance load distribution corona, EG without corona and DA without corona based schemes to distribute data traffic across the network nodes for efficient energy consumption. The dynamic adjustment of transmission range in first scheme helps in reducing data load. Additionally, the transmission range is purely based on distance, energy and data load of the receiver node for achieving maximum network lifetime. Second scheme divides a data packet into three fractions; small, medium and large for transmitting from various paths to evenly distribute the data load on the network nodes. In third scheme, depth adjustment of void node is performed to resume network operations, whereas, the load distribution and transmission range mechanisms are the same. The extensive simulations are carried out to show the effectiveness of proposed schemes in terms of PDR, energy consumption, and load distribution against the baseline scheme. [ABSTRACT FROM AUTHOR]

Underwater wireless sensor networks (UWSNs) applications for ocean monitoring, deep sea surveillance, and locating natural resources are gaining more and more popularity. To monitor the underwater environment or any object within a certain area of interest, these applications are required to deploy underwater node sensors connected for obtaining useful data. For thriving UWSNs, it is essential that an efficient and secure node deployment mechanism is in place. This paper presents a novel node deployment scheme, which is based on evidence theory approach and caters for 3D USWNs. This scheme implements sonar probability perception and an enhanced data fusion model to improve prior probability deployment algorithm of D–S evidence theory. The viability of our algorithm is verified by performing multiple simulation experiments. The simulation results reveal that our algorithm deploys fewer nodes with enhanced network judgment criteria and expanded detection capabilities for a relatively large coverage area compared to other schemes. In addition, the generated nodes are also less resource intensive, i.e., low-power sensor nodes. [ABSTRACT FROM AUTHOR]

In this paper, depth and reliability aware delay sensitive (DRADS), interference aware DRADS (iDRADS) and cooperative iDRADS (Co-iDRADS) routing protocols are proposed for maximizing network good-put while minimizing end-to-end delay. We have introduced a new metric called depth threshold to minimize the number of hops between source and destination while ensuring successful packet delivery. Our interference aware and co-operative routing based algorithms select the best relay node at each hop. Extensive simulation results validate that the proposed routing techniques perform better than the selected existing ones in terms of good-put and energy cost of the network. [ABSTRACT FROM AUTHOR]

An underwater acoustic modem (UAM) is an essential component of an underwater wireless sensor network (UWSN). The applications of UWSNs include, but are not limited to, monitoring of aquatic environments and coral reefs, coastal surveillance, etc. The design of UAMs is a challenging research problem due to the varying water environment. Moreover, the cost of UAM is an impediment to use it in a large UWSN. Hence, an economical UAM is required to encourage research in this area. In this paper, a low-cost modem prototype for short-range underwater acoustic communications is presented. As compared to the available solutions, cost-effectiveness is novelty of the modem. Furthermore, design parameters are available that could be modified or replicated for further research. Each module is tested individually and the overall performance of the modem is evaluated by experiments in an aquatic environment. The outcomes of the research are useful for the scientific community and provide guidelines to design a low-cost underwater acoustic modem. [ABSTRACT FROM AUTHOR]

Underwater wireless sensor networks (UWSNs) can provide a promising solution to underwater target tracking. Due to limited energy and bandwidth resources, only a small number of nodes are selected to track a target at each interval. Because all measurements are fused together to provide information in a fusion center, fusion weights of all selected nodes may affect the performance of target tracking. As far as we know, almost all existing tracking schemes neglect this problem. We study a weighted fusion scheme for target tracking in UWSNs. First, because the mutual information (MI) between a node’s measurement and the target state can quantify target information provided by the node, it is calculated to determine proper fusion weights. Second, we design a novel multi-sensor weighted particle filter (MSWPF) using fusion weights determined by MI. Third, we present a local node selection scheme based on posterior Cramer-Rao lower bound (PCRLB) to improve tracking efficiency. Finally, simulation results are presented to verify the performance improvement of our scheme with proper fusion weights. [ABSTRACT FROM AUTHOR]

Underwater wireless sensor networks are significantly different from terrestrial wireless sensor networks in that sound is mainly used as the communication medium. The limited bandwidth, long propagation delay and high bit error rate pose great challenges in Media Access Control (MAC) protocol design for underwater wireless sensor networks. In this paper, we propose a Slotted-FAMA based MAC protocol for underwater wireless sensor networks with data train, called SFAMA-DT. It improves the channel utilization by forming a train of data packets of multiple transmission pairs during each round of simultaneously handshakes, which overcomes the multiple RTS attempts problem of Slotted-FAMA in high traffic environments and greatly reduces the relative proportion of time wasted due to the propagation delays of control packets. Our simulations show that the SFAMA-DT is able to achieve much higher throughput than the Slotted-FAMA protocol. [ABSTRACT FROM AUTHOR]

With the advances in technology, there has been an increasing interest both from research and industrial communities in the use of Underwater Wireless Sensor Networks (UWSNs). These networks are vulnerable to a wide class of security attacks. In fact, UWSNs are particularly more susceptible to attacks than their ground-base counterparts due to the challenges imposed by their deployment environment. This paper proposes a distributed approach to detect and mitigate routing attacks in such networks. An analytical model is provided to capture the interactions between various contributing parameters. Our simulation experiments validate the correctness and efficiency of the proposed approach. [ABSTRACT FROM AUTHOR]

Routing in underwater wireless sensor networks (UWSN) is an important and a challenging activity due to the nature of acoustic channels and to the harsh environment. This paper extends our previous work [Al-Salti et al. in Proceedings of cyber-enabled distributed computing and knowledge discovery (CyberC), Shanghai, pp 331-336, 2014] that proposed a novel multipath grid-based geographical routing (MGGR) protocol for UWSNs. The extended work, EMGGR, viewed the network as logical 3D grids. Routing is performed in a grid-by-grid manner via gateways that use disjoint paths to relay data packets to the sink node. The algorithm consists of three main components: (1) a gateway election algorithm; responsible for electing gateways based on their locations and remaining energy level (2) a mechanism for updating neighboring gateways' information; allowing sensor nodes to memorize gateways in local and neighboring cells, and (3) a packet forwarding mechanism; in charge of constructing disjoint paths from source cells to destination cells, forwarding packets to the destination and dealing with holes (i.e. cells with no gateways) in the network. The performance of EMGGR has been assessed using Aqua-Sim, which is an NS2 based simulator for UWSNs. Results show that EMGGR is an energy efficient protocol in all simulation setups used in the study. Moreover, EMGGR can also maintain good delivery ratio and end-to-end delay. [ABSTRACT FROM AUTHOR]

Underwater Wireless Sensor Networks (UWSNs) consume a significant amount of energy because of high transmission power and lengthy data packet transmission time. Sensors of UWSNs, which perform numerous tasks like target tracking, intrusion detection etc. can preserve energy and attain longer network life time by appropriate selection of cluster head (CH), cluster size (CS), and routing scheme. In order to achieve this, an Intra and Inter Cluster Communication (IICC) for data aggregation in UWSN have been proposed here. In our approach, the CH selection and CS are determined by using fuzzy logic. The main strength of our paper is to provide an optimal selection for CH as well as optimal intra and inter cluster communications based on energy and multiple paths. Minimum Average Routing Path Clustering Protocol method is implemented for intra-clustering communication in the network. Hierarchical Multi-path Routing-LEACH method is implemented for inter-cluster communication in the network. Experimental simulation shows that IICC improves the performance of UWSN in terms of end-to-end packet delay, energy consumption and packet delivery ratio. The proposed approach is adaptive in nature as it reduces the average energy consumption and end-to-end delay, thereby improving the packet delivery ratio. [ABSTRACT FROM AUTHOR]

With the advance and wide applicability of the Internet of Underwater Things, smart things are deployed under the water and form the underwater wireless sensor networks, for the exploration of vast ocean volume. Generally, a sub-region, rather than the whole network region, may be interested by a certain application in a certain time duration. To address this challenge, a sub-region query processing mechanism is proposed. Specifically, a routing tree is constructed where a sensor node corresponds to a tree node. A sensor node acknowledges the fact that whether it lies within the sub-region of interest or not through the localisation techniques. Sensory data are routed to the sink node leveraging the parent-child relation of sensor nodes specified in the routing tree. Experimental evaluation shows that our technique is more energy efficient when the network topology is relatively steady. [ABSTRACT FROM AUTHOR]

Wireless Sensor Networks (WSN) consist of small battery-limited devices called sensor nodes. The communication between sensor nodes is a type of peer-to-peer communication, since each node has the same capability and role. One of the recent application areas of these nodes is underwater sensing. Communication in Underwater Wireless Sensor Networks (UWSN) is challenging since radio frequencies cannot be used. Instead acoustic waves, which cause extra challenges, are used in UWSN. Since UWSNs are deployed in hostile environment, nodes can be captured by an adversary. In order to secure UWSNs, key distribution problem must be addressed. Moreover, UWSNs are inherently mobile since the nodes may be drifted in the sea. In this paper, we propose a key distribution model which is applied for two group mobility models, namely nomadic mobility model and meandering mobility model. In both schemes hierarchical structure is used and communication is handled via well-known Blom's key distribution scheme. Our simulation results show that mobility causes some temporary decreases in the connectivity, but our schemes help to heal the connectivity performance in time. Moreover, our schemes show good resiliency performance such that capture of some nodes by an adversary only causes very small amount of links between uncaptured nodes to be compromised. [ABSTRACT FROM AUTHOR]

Underwater Wireless Sensor Networks (UWSNs) have distinctive characteristics due to the use of acoustic signals as its physical medium for communications, including high propagation delay, limited bandwidth and high error rates. Hence, designing communication protocols, particularly, an efficient routing protocol for UWSNs is a challenging issue. Routing protocols can take advantage of the localization of sensor nodes. However, the localization itself is not impeccable in UWSNs. In this paper, we therefore propose a localization-free routing protocol named MRP (multi-layered routing protocol) for UWSNs. MRP utilizes super nodes in order to eliminate the need of localization. MRP works in two phases: Layering phase and Data forwarding phase. During layering phase, different layers are formed around the super nodes. In data forwarding phase, data packets are forwarded based on these layers. Through simulation study using NS-2 simulator, we proved that MRP contributes significant performance improvements against representative routing protocols. [ABSTRACT FROM AUTHOR]

In order to increase the localization coverage while keeping the localization error small in a unique network architecture in which there are not evenly distributed anchor nodes with great ability of communication or additional infrastructure, a Top-down Positioning Scheme (TPS) for underwater acoustic sensor networks is proposed. By defining node's confidence reasonably, TPS insures the quality of the new reference nodes. TPS also refines the nodes which have just been positioned via the gradient method and helps non-localized nodes search for more reference nodes via the new scheme for 3D Euclidean distance estimation. By comparing the new scheme for 3D Euclidean distance estimation with the existing scheme, the new scheme is shown to have greater ability to estimate two-hop Euclidean distance in 3D space. Simulation results show that TPS which integrates node's confidence defined reasonably, the gradient method, and the new scheme for 3D Euclidean distance estimation can increase the localization coverage ratio, while keeping the localization error small. [ABSTRACT FROM AUTHOR]

In recent times, Underwater Wireless Sensor Networks (UWSNs) have involved various applications in oceanographic data collection, pollution revealing, environmental monitoring, offshore exploration, disaster prevention, military surveillance, etc. nevertheless the unique characterization of UWSNs are designed for the grid division on geographical system with polar tracing function to attain the shortest- path and minimizing the energy consumption for end – to – end transmission. In this paper, we proposed a Grid Division Polar Tracing (GDPT) routing protocol function using greedy algorithm for reducing the energy consumption by incorporating into cubic grids and polar tracing functions. The NS2 simulation results proved that the optimal distance of the found path, packet delivery ratio, network lifetime, energy consumption and propagation delay are the performance metrics in the routing protocols. In proposed case used for application of underwater sensor based health monitoring system for wireless in under water environment. [ABSTRACT FROM AUTHOR]