A cluster‐based fault‐tolerant routing protocol for wireless sensor networks

Energy conservation and fault tolerance are two critical issues in the deployment of wireless sensor networks (WSNs). Many cluster‐based fault‐tolerant routing protocols have been proposed for energy conservation and network lifetime maximization in WSNs. However, these protocols suffer from high frequency of re‐clustering as well as extra energy consumption to tolerate failures and consider only some very normal parameters to form clusters without any verification of the energy sufficiency for data routing. Therefore, this paper proposes a cluster‐based fault‐tolerant routing protocol referred as CFTR. This protocol allows higher energy nodes to become Cluster Heads (CHs) and operate multiple rounds to diminish the frequency of re‐clustering. Additionally, for the sake to get better energy efficiency and balancing, we introduce a cost function that considers during cluster formation energy cost from sensor node to CH, energy cost from CH to sink, and another significant parameter, namely, number of cluster members in previous round. Further, the proposed CFTR takes care of nodes, which have no CH in their communication range. Also, it introduces a routing algorithm in which the decision of next hop CH selection is based on a cost function conceived to select routes with sufficient energy for data transfer and distribute uniformly the overall data‐relaying load among the CHs. As well, a low‐overhead algorithm to tolerate the sudden failure of CHs is proposed. We perform extensive simulations on CFTR and compare their results with those of two recent existing protocols to demonstrate its superiority in terms of different metrics.     

LRP: Link quality‐aware queue‐based spectral clustering routing protocol for underwater acoustic sensor networks

Recently, underwater acoustic sensor networks (UASNs) have been considered as a promising approach for monitoring and exploring the oceans in lieu of traditional underwater wireline instruments. As a result, a broad range of applications exists ranging from oil industry to aquaculture and includes oceanographic data collection, disaster prevention, offshore exploration, assisted navigation, tactical surveillance, and pollution monitoring. However, the unique characteristics of underwater acoustic communication channels, such as high bit error rate, limited bandwidth, and variable delay, lead to a large number of packet drops, low throughput, and significant waste of energy because of packets retransmission in these applications. Hence, designing an efficient and reliable data communication protocol between sensor nodes and the sink is crucial for successful data transmission in underwater applications. Accordingly, this paper is intended to introduce a novel nature‐inspired evolutionary link quality‐aware queue‐based spectral clustering routing protocol for UASN‐based underwater applications. Because of its distributed nature, link quality‐aware queue‐based spectral clustering routing protocol successfully distributes network data traffic load evenly in harsh underwater environments and avoids hotspot problems that occur near the sink. In addition, because of its double check mechanism for signal to noise ratio and Euclidean distance, it adopts opportunistically and provides reliable dynamic cluster‐based routing architecture in the entire network. To sum up, the proposed approach successfully finds the best forwarding relay node for data transmission and avoids path loops and packet losses in both sparse and densely deployed UASNs. Our experimental results obtained in a set of extensive simulation studies verify that the proposed protocol performs better than the existing routing protocols in terms of data delivery ratio, overall network throughput, end‐to‐end delay, and energy efficiency.     

Agent‐based secure routing for underwater acoustic sensor networks

The underwater networks have severe security implications and are vulnerable to various types of attacks such as selective forwarding, wormhole, and sinkhole. Neighbor discovery, a fundamental requirement for routing is vulnerable to wormhole attack, which enables false neighbor acceptance, thereby degrading the routing performance. The proposed agent‐based secured routing scheme enhances the quality of service by discovering the wormhole resilient secure neighbors and route the information through the secure path. This scheme uses 4 agencies, namely, security, routing, underwater gateway, and vehicle, which are embedded with static and mobile agents. (1) Agents in security agency of a node discover secured neighbors by using the direction of arrival estimation and authentication, (2) agents in routing agency of a node establish secured routes from source to surface gateway, (3) agents in Underwater Gateway Agency communicate with Autonomous Underwater Vehicles (AUVs) and underwater nodes for key distribution, and (4) vehicle traversing agency in AUV coordinates with Underwater Gateway Agency for changing AUVs traversal to cover the isolated network area. The proposed scheme depicts the improved performance compared to basic neighbor discovery and channel aware routing protocol in terms of failure detection, energy consumption, and overheads.     

A reliable and energy‐efficient routing protocol for underwater wireless sensor networks

Recently, underwater wireless sensor networks (UWSNs) have attracted much research attention to support various applications for pollution monitoring, tsunami warnings, offshore exploration, tactical surveillance, etc. However, because of the peculiar characteristics of UWSNs, designing communication protocols for UWSNs is a challenging task. Particularly, designing a routing protocol is of the most importance for successful data transmissions between sensors and the sink. In this paper, we propose a reliable and energy‐efficient routing protocol, named R‐ERP²R (Reliable Energy‐efficient Routing Protocol based on physical distance and residual energy). The main idea behind R‐ERP²R is to utilize physical distance as a routing metric and to balance energy consumption among sensors. Furthermore, during the selection of forwarding nodes, link quality towards the forwarding nodes is also considered to provide reliability and the residual energy of the forwarding nodes to prolong network lifetime. Using the NS‐2 simulator, R‐ERP²R is compared against a well‐known routing protocol (i.e. depth‐based routing) in terms of network lifetime, energy consumption, end‐to‐end delay and delivery ratio. The simulation results proved that R‐ERP²R performs better in UWSNs.Copyright © 2012 John Wiley & Sons, Ltd.     

Investigation of maximum lifetime and minimum delay trade‐off in underwater sensor networks

Underwater acoustic sensor networks (UASNs) are subjected to harsh characteristics of underwater acoustic channel such as severe path losses, noise, and high propagation delays. Among these constraints, propagation delay (more generally, end‐to‐end delay) is the most dominating limitation especially for time‐critical UASN applications. Although the minimization of end‐to‐end delay can be achieved by using the minimum hop routing, this solution cannot lead prolonged lifetimes since nodes consume excessive energy for transmission over long links. On the other hand, the maximization of network lifetime is possible by using energy efficient paths, which consist of relatively short links but high number of hops. However, this solution results in long end‐to‐end delays. Hence, there is a trade‐off between maximizing the network lifetime and minimizing the end‐to‐end delay in UASNs. In this work, we develop a novel multi‐objective–optimization (MOO) model that jointly maximizes the network lifetime while minimizing the end‐to‐end delay. We systematically analyze the effects of limiting the end‐to‐end delay on UASN lifetime. Our results reveal that the minimum end‐to‐end delay routing solution results in at most 72.93% reduction in maximum network lifetimes obtained without any restrictions on the end‐to‐end delay. Nevertheless, relaxing the minimum end‐to‐end delay constraint at least by 30.91% yields negligible reductions in maximum network lifetimes.     

Fuzzy-based unequal clustering protocol for underwater wireless sensor networks

Underwater wireless sensor network (UWSN) is a network made up of underwater sensor nodes, anchor nodes, surface sink nodes or surface stations, and the offshore sink node. Energy consumption, limited bandwidth, propagation delay, high bit error rate, stability, scalability, and network lifetime are the key challenges related to underwater wireless sensor networks. Clustering is used to mitigate these issues. In this work, fuzzy-based unequal clustering protocol (FBUCP) is proposed that does cluster head selection using fuzzy logic as it can deal with the uncertainties of the harsh atmosphere in the water. Cluster heads are selected using linguistic input variables like distance to the surface sink node, residual energy, and node density and linguistic output variables like cluster head advertisement radius and rank of underwater sensor nodes. Unequal clustering is used to have an unequal size of the cluster which deals with the problem of excess energy usage of the underwater sensor nodes near the surface sink node, called the hot spot problem. Data gathered by the cluster heads are transmitted to the surface sink node using neighboring cluster heads in the direction of the surface sink node. Dijkstra's shortest path algorithm is used for multi-hop and inter-cluster routing. The FBUCP is compared with the LEACH-UWSN, CDBR, and FBCA protocols for underwater wireless sensor networks. A comparative analysis shows that in first node dies, the FBUCP is up to 80% better, has 64.86% more network lifetime, has 91% more number of packets transmitted to the surface sink node, and is up to 58.81% more energy efficient than LEACH-UWSN, CDBR, and FBCA.     

Energy‐efficient void avoidance geographic routing protocol for underwater sensor networks

Underwater wireless sensor networks (UWSNs) consist of a group of sensors that send the information to the sonobuoys at the surface level. Void area, however, is one of the challenges faced by UWSNs. When a sensor falls in a void area of communication, it causes problems such as high latency, power consumption, or packet loss. In this paper, an energy‐efficient void avoidance geographic routing protocol (EVAGR) has been proposed to handle the void area with low amount of energy consumption. In this protocol, a suitable set of forwarding nodes is selected using a weight function, and the data packets are forwarded to the nodes inside the set. The weight function includes the consumed energy and the depth of the candidate neighboring nodes, and candidate neighboring node selection is based on the packet advancement of the neighboring nodes toward the sonobuoys. Extensive simulation experiments were performed to evaluate the efficiency of the proposed protocol. Simulation results revealed that the proposed protocol can effectively achieve better performance in terms of energy consumption, packet drop, and routing overhead compared with the similar routing protocol.     

DRP: An energy‐efficient routing protocol for underwater sensor networks

The features of transmissions in underwater sensor networks (UWSNs) include lower transmission rate, longer delay time, and higher power consumption when compared with terrestrial radio transmissions. The negative effects of transmission collisions deteriorate in such environments. Existing UWSN routing protocols do not consider the transmission collision probability differences resulting from different transmission distances. In this paper, we show that collision probability plays an important role in route selection and propose an energy‐efficient routing protocol (DRP), which considers the distance‐varied collision probability as well as each node's residual energy. Considering these 2 issues, DRP can find a path with high successful transmission rate and high‐residual energy. In fact, DRP can find the path producing the longest network lifetime, which we have confirmed through theoretical analysis. To the best of our knowledge, DRP is the first UWSN routing protocol that uses transmission collision probability as a factor in route selection. Simulation results verify that DRP extends network lifetime, increases network throughput, and reduces end‐to‐end delay when compared with solutions without considering distance‐varied collision probability or residual energy.     

Beacon‐based routing protocols for underwater acoustic sensor networks

Underwater Acoustic Sensor Networks (UW‐ASN) are provisioned with limited bandwidth, long variable propagation delay, limited available energy, highly unreliable acoustic channels, and random node mobility. Consequently, efficient data routing between source destination pair requires UW‐ASN to apply a technology different than terrestrial networks. For the past few years researchers have proposed many robust and efficient routing protocols for UW‐ASN, thus reviewing the challenges posed by stringent underwater environment. These protocols can be broadly categorized into localization based and localization‐free protocols. This paper presents a critical review of beacon‐based localization‐free routing protocols and suggest possible solution to improve the working of studied beacon based protocols. This work categorizes beacon based protocols into hop‐by‐hop, end‐to‐end, single, and multiple parameters based forwarding protocols. This categorization will help to differentiate and identify the requirements for the development of new beacon‐based protocols. Finally, this paper presents performance comparison based on simulation results and outlines the research gap and future directions.     

A fault‐tolerant energy‐efficient clustering protocol of a wireless sensor network

Energy efficiency in specific clustering protocols is highly desired in wireless sensor networks. Most existing clustering protocols periodically form clusters and statically assign cluster heads (CHs) and thus are not energy efficient. Every non‐CH node of these protocols sends data to the CH in every time slot of a frame allocated to them using the time division multiple access scheme, which is an energy‐consuming process. Moreover, these protocols do not provide any fault tolerance mechanism. Considering these limitations, we have proposed an efficient fault‐tolerant and energy‐efficient clustering protocol for a wireless sensor network. The performance of the proposed protocol was tested by means of a simulation and compared against the low energy adaptive clustering hierarchy and dynamic static clustering protocols. Simulation results showed that the fault‐tolerant and energy‐efficient clustering protocol has better performance than both the low energy adaptive clustering hierarchy and dynamic static clustering protocols in terms of energy efficiency and reliability. Copyright © 2012 John Wiley & Sons, Ltd.     

A novel fault detection and recovery technique for cluster‐based underwater wireless sensor networks

The performance of underwater wireless sensor network gets affected by the working of a cluster in the network. The cluster head (CH) or cluster member (CM) fails because of energy depletion or hardware errors that increase delay and message overhead of the network. To recover the affected cluster, a technique is required to identify the failed CH or CM. We propose a fault detection and recovery technique (FDRT) for a cluster‐based network in this paper. Primarily, while selecting the CH, a backup cluster head (BCH) is selected using fuzzy logic technique based on parameters such as node density, residual energy, load, distance to sink, and link quality. Then, failure of CH, BCH, and CM is detected. If fault is detected at CH, then the BCH will start performing the task of failed CH. Simultaneously, when BCH failed, any other CM will be elected as BCH. If any of the CM appears to be nonperforming, then CH will detect the communication failure and request BCH to transfer the data from the failed CM to CH. The comparison of proposed FDRT is performed with existing FDRTs EDETA, RCH, and SDMCGC on the basis of packet drop, end‐to‐end delay, energy consumption, and delivery ratio of data packets. By simulation results, it is shown that FDRT for cluster‐based underwater wireless sensor network results in quicker detection of failures and recovery of the network along with the reduction in energy consumption, thereby increasing the lifespan of the network.     

一种用于水声传感网的MAC层协议

针对分簇的水声传感网,提出了一种基于时分多址（TDMA）的MAC层协议——Cluster-TDMA。该协议主要由规划阶段和传输阶段组成。规划阶段,首先由网关节点规划能造成簇间干扰的子节点的传输,其次由各簇头节点分别规划本簇内其他子节点的传输;传输阶段,子节点根据规划表周期性地向簇头节点发送数据,这些数据最终汇聚到网关节点。该协议简单有效地解决了引起簇间干扰子结点的传输规划问题。C++仿真实验表明,该协议具有良好的吞吐率和能量效率性能。     

Coverage‐aware connectivity‐constrained unattended sensor deployment in underwater acoustic sensor networks

Careful deployment of nodes in underwater acoustic sensor networks in a distributed manner with the goal of maximized coverage and guaranteed connectivity is a challenging problem because it is very difficult and costly to access the 3D underwater environment. This paper presents a novel algorithm for self‐deployment of nodes in underwater acoustic sensor networks assuming that the nodes are randomly dropped to the water surface and form a densely populated connected network at the water surface. The idea of the algorithm is based on calculating an optimized depth for each node in the network in such a way that the possible sensing coverage overlaps are minimized and the connectivity of final topology is guaranteed. The algorithm has three main phases. In the first phase, nodes are organized in a tree structure that is rooted at the surface station. In the second phase, the depths for all nodes are computed iteratively at surface station. In the final phase, the calculated depths are distributed to nodes so that the nodes start sinking. The performance of the proposed approach is validated through simulation. We observed that the proposed approach performs at least 10% better in terms of network coverage than contemporary schemes in the literature. Copyright © 2016 John Wiley & Sons, Ltd.     

Graph‐based optimal asynchronous scheduling in large propagation delay underwater acoustic sensor networks

Optimal scheduling is essential to minimize the time wastage and maximize throughput in high propagation delay networks such as in underwater and satellite communication. Understanding the drawbacks of synchronous scheduling, this paper addresses an asynchronous optimal scheduling problem to minimize the time wastage during the transmission. The proposed scheduling problem is analyzed in both broadcast and non‐broadcast networks, which is highly applicable in high propagation delay networks. In broadcast networks, the proposed scheduling method reduces to a graph‐theoretic model that is shown to be equivalent to the classic algorithmic asymmetric traveling salesman problem (TSP) which is NP‐Hard. Although it is NP‐Hard, the TSP is well‐investigated with many available methods to find the best solution for up to tens of thousands of nodes. In non‐broadcast networks, the optimal solution to the scheduling problem considers the possibility of parallel transmission, which is optimized using graph coloring algorithm. The groups obtained through graph coloring are solved using Asymmetric Traveling Salesman algorithm to obtain the optimal schedule. The proposed method efficiently solves the scheduling problem for networks of practical size.     

Affinity propagation‐based interference‐free clustering for wireless sensor networks

Wireless sensor networks (WSNs), eg, industrial WSNs, require reliability and real‐time communication. Clustering technique together with schedule‐based access can provide the benefits, such as energy saving, reliability, and timeliness. However, integrating above two technologies into WSNs requires sophistical time slot allocation mechanism. To simplify the time slot allocation, the paper proposes a distributed interference‐free clustering algorithm for WSNs. The algorithm is inspired by affinity propagation (AP) clustering algorithm. By adapting and improving the original AP algorithm, the proposed clustering algorithm aims to jointly optimize energy saving and coverage issues while providing interference free between clusters. The performance analysis demonstrates that it can achieve high receiving rate (reliability), low delay (real time), and low‐energy consumption.     

DFR: an efficient directional flooding‐based routing protocol in underwater sensor networks

Unlike terrestrial sensor networks, underwater sensor networks (UWSNs) have salient features such as a long propagation delay, narrow bandwidth, and high packet loss over links. Hence, path setup‐based routing protocols proposed for terrestrial sensor networks are not applicable because a large latency of the path establishment is observed, and packet delivery is not reliable in UWSNs. Even though routing protocols such as VBF (vector based forwarding) and HHVBF (hop‐by‐hop VBF) were introduced for UWSNs, their performance in terms of reliability deteriorates at high packet loss. In this paper, we therefore propose a directional flooding‐based routing protocol, called DFR, in order to achieve reliable packet delivery. DFR performs a so‐called controlled flooding, where DFR changes the number of nodes which participate in forwarding a packet according to their link quality. When a forwarding node has poor link quality to its neighbor nodes geographically advancing toward the sink, DFR allows more nodes to participate in forwarding the packet. Otherwise, a few nodes are enough to forward the packet reliably. In addition, we identify two types of void problems which can occur during the controlled flooding and introduce their corresponding solutions. Our simulation study using ns‐2 simulator proves that DFR is more suitable for UWSNs, especially when links are prone to packet loss. Copyright © 2011 John Wiley & Sons, Ltd.     

RPCP‐MAC: Receiver preambling with channel polling MAC protocol for underwater wireless sensor networks

To design a reliable and energy efficient medium access control (MAC) protocol for underwater wireless sensor networks (UWSNs) is an active research area due to its variety of applications. There are many issues associated with underwater acoustic channels including long and variable propagation delay, attenuation, and limited bandwidth which pose significant challenges in the design of MAC protocol. The available sender‐initiated asynchronous preamble‐based MAC protocols for UWSNs are not reliable and energy‐efficient. This is due to the problems caused by transmission of preambles for longer duration and collision of preambles from hidden nodes in sender‐initiated preamble‐based MAC protocols. To resolve these issues, the paper proposed an asynchronous receiver‐initiated preamble‐based MAC protocol named Receiver Preambling with Channel Polling MAC (RPCP‐MAC) protocol for shallow underwater monitoring applications with high data rates. The protocol is proposed to resolve data packet collision and support reliability in an energy‐efficient way without using any transmission schedule. The proposed protocol is based on the following mechanisms. Firstly, receiver preambling mechanism is adopted to reduce idle listening. Secondly, channel polling mechanism is used to determine missing data frame during its sleeping period and to minimize the active time of node and reduces energy wastage. Finally, a back‐off mechanism is applied to resolve collision when preambles are received simultaneously. In addition, performance analysis through Markov chain together with its validation with simulation‐based studies is reported in the paper. Both the analytical and simulation results have demonstrated the reliability achievable with RPCP‐MAC while providing good energy efficiency.     

基于拓扑重构的水下移动无线传感器网络拓扑优化

针对水下移动无线传感器网络（MUWSN, mobile underwater wireless sensor networks）拓扑随洋流动态演化对其网络性能会产生很大影响,提出了一种基于拓扑重构的水下移动无线传感器网络拓扑优化方法,首先通过模拟鱼群行为对传感器节点位置进行调整,优化网络覆盖度;其次,利用冗余节点修复网络中不连通位置,消除关键节点,优化网络连通性,最后,通过仿真对比实验验证了该方法的合理性和有效性。实验结果表明,所提算法能在较低能耗下,保证网络覆盖度长期维持在97%左右,连通率达到89%以上。     

CT-TDMA：水下传感器网络高效TDMA协议

针对水下无线传感器网络(UWSN,underwater sensor networks)提出以发送端为中心以连续时间为计量单位的冲突状态模型——局部冲突状态图及其分布式构建算法,并在此基础上设计了基于启发式规则的水下传感器网络TDMA协议(CT-TDMA,continuous time based TDMA)。CT-TDMA利用UWSN中同一接收节点与不同发送节点之间链路时延的差异性,减少在目的端的接收帧之间的空闲时间,从而提高网络流量;基于启发式规则的分配算法,能有效缩短连续时间轴上的时刻分配所花费的时间。模拟实验证明:CT-TDMA与以ST-MAC为代表的按时隙分配的TDMA方案相比,网络流量提高了20%,数据分组的端到端时延降低了18%;与由全局知识所计算出的最优分配策略相比,网络流量达到了80%,端到端时延仅延长了12%。     

Localized and load‐balanced clustering for energy saving in wireless sensor networks

In this paper, the ‘localized and load‐balanced clustering (LLBC)’ protocol is proposed for the energy savings and lifetime increases of wireless sensor networks. LLBC contains two approaches. One is improved cluster head rotation (ICHR) and the other is modified static clustering (MSC). ICHR uses the present cluster heads to select most energetic sensors as the next‐round cluster heads and avoids the margin cluster heads being selected as cluster heads repeatedly. MSC is suitable when the network has a few very high energetic sensors. It uses the method of inter‐cluster load balance to adjust the cardinality of each cluster as close to the average cardinality as possible. The simulation results with respect to FND (the time when a node dies first), HND (the time when half of the total nodes have died), and energy consumption show that the orders of effectiveness are: for ICHR and low‐energy adaptive clustering hierarchy (LEACH)‐C, before 250 rounds of cluster head rotations, there is no significant difference between the two, but after 250 rounds, ICHR>LEACH?C; and in general, LEACH?C>LEACH>MSC>mini variance>direct communication. Copyright © 2008 John Wiley & Sons, Ltd.