Connectivity maintenance and coverage preservation in wireless sensor networks

In wireless sensor networks, one of the main design challenges is to save severely constrained energy resources and obtain long system lifetime. Low cost of sensors enables us to randomly deploy a large number of sensor nodes. Thus, a potential approach to solve lifetime problem arises. That is to let sensors work alternatively by identifying redundant nodes in high-density networks and assigning them an off-duty operation mode that has lower energy consumption than the normal on-duty mode. In a single wireless sensor network, sensors are performing two operations: sensing and communication. Therefore, there might exist two kinds of redundancy in the network. Most of the previous work addressed only one kind of redundancy: sensing or communication alone. Wang et al. [Intergrated Coverage and Connectivity Configuration in Wireless Sensor Networks, in: Proceedings of the First ACM Conference on Embedded Networked Sensor Systems (SenSys 2003), Los Angeles, November 2003] and Zhang and Hou [Maintaining Sensing Coverage and Connectivity in Large Sensor Networks. Technical report UIUCDCS-R-2003-2351, June 2003] first discussed how to combine consideration of coverage and connectivity maintenance in a single activity scheduling. They provided a sufficient condition for safe scheduling integration in those fully covered networks. However, random node deployment often makes initial sensing holes inside the deployed area inevitable even in an extremely high-density network. Therefore, in this paper, we enhance their work to support general wireless sensor networks by proving another conclusion: “the communication range is twice of the sensing range” is the sufficient condition and the tight lower bound to ensure that complete coverage preservation implies connectivity among active nodes if the original network topology (consisting of all the deployed nodes) is connected. Also, we extend the result to k-degree network connectivity and k-degree coverage preservation.     

Homing‐pigeon‐based messaging: multiple pigeon‐assisted delivery in delay‐tolerant networks

In this paper, we consider the applications of delay‐tolerant networks (DTNs), where the nodes in a network are located in separated areas, and in each separated area, there exists (at least) an anchor node that provides regional network coverage for the nearby nodes. The anchor nodes are responsible for collecting and distributing messages for the nodes in the vicinity. This work proposes to use a set of messengers (named pigeons) that move around the network to deliver messages among multiple anchor nodes. Each source node (anchor node or Internet access point) owns multiple dedicated pigeons, and each pigeon takes a round trip starting from its home (i.e., the source) through the destination anchor nodes and then returns home, disseminating the messages on its way. We named this as a homing‐pigeon‐based messaging (HoPM) scheme. The HoPM scheme is different from the prior schemes in that each messenger is completely dedicated to its home node for providing messaging service. We obtained the average message delay of HoPM scheme in DTN through theoretical analysis with three different pigeon scheduling schemes. The analytical model was validated by simulations. We also studied the effects of several key parameters on the system performance and compared the results with previous solutions. The results allowed us to better understand the impacts of different scheduling schemes on the system performance of HoPM and demonstrated that our proposed scheme outperforms the previous ones. Copyright © 2011 John Wiley & Sons, Ltd.     

无线传感网两种中继选择策略的中断概率分析

无线传感网发射功率受限,采用中继通信的方式可以扩展通信覆盖区域,中继选择是其关键技术之一。不同的中继选择策略会对中断概率产生不同的影响,其一是选择候选集合中的所有节点作为中继节点,其二是选择候选节点中的信噪比最大的节点作为中继节点。为了比较这两种中继选择策略的性能,推算了两种策略下的中断概率闭合表达式,并进行数值分析。结果表明,在不考虑功耗平衡的前提下,策略二的性能优于策略一。     

Design of Probability Density Function Targeting Energy Efficient Network for Coalition Based WSNs

Energy consumption is one of the important issues in wireless sensor network that rely on non chargeable batteries for power. Also, the sensor network has to maintain a desired sensing coverage area along with periodically sending of the sensed data to the base station. Therefore, coverage and the lifetime are the two important issues that need to be addressed. Effective deployment of wireless sensors is a major concern as the coverage and lifetime of any wireless sensor network depends on it. In this paper, we propose the design of a Probability Density Function (PDF) targeting the desired coverage, and energy efficient node deployment scheme. The suitability of the proposed PDF based node distribution to model the network architecture considered in this work has been analyzed. The PDF divides the deployment area into concentric coronas and provides a probability of occurrence of a node within any corona. Further, the performance of the proposed PDF is evaluated in terms of the coverage, the number of transmissions of packets and the lifetime of the network. The scheme is compared with the existing node deployment schemes based on various distributions. The percentage gain of the proposed PDF based node deployment is 32\(\%\) more than that when compared with the existing schemes. Thus, the simulation results obtained confirm the schemes superiority over the other existing schemes.     

An energy-efficient optimization deployment scheme for wireless sensor networks

Most of the current deployment schemes for Wireless Sensor Networks (WSNs) do not take the network coverage and connectivity features into account, as well as the energy consumption. This paper introduces topology control into the optimization deployment scheme, establishes the mathematical model with the minimum sum of the sensing radius of each sensors, and uses the genetic algorithm to solve the model to get the optimal coverage solution. In the optimal coverage deployment, the communication and channel allocation are further studied. Then the energy consumption model of the coverage scheme is built to analyze the performance of the scheme. Finally, the scheme is simulated through the network simulator NS-2. The results show the scheme can not only save 36% energy averagely, but also achieve 99.8% coverage rate under the condition of 45 sensors being deployed after 80 iterations. Besides, the scheme can reduce the five times interference among channels.     

ZBFR: zone based failure recovery in WSNs by utilizing mobility and coverage overlapping

Wireless sensor networks are more prone to failures as compared to other traditional networks. The frequent faults and failures sometime create large holes causing loss of sensing and connectivity coverage in the network. In present work, a zone based failure detection and recovery scheme is presented to reliably handle such node failures. We first propose a consensus and agreement based approach to elect a suitable monitor node called as zone monitor (ZM). ZM is responsible for coordinating failure recovery activities and maintaining desired coverage within a zone. In order to overcome failure overhead due to false failure detection, a consensus is carried out amongst neighboring nodes of a suspicious node to confirm the correct status with high accuracy. On confirmation of a node failure, the impact of resulting hole on coverage is analyzed and if impact exceeds beyond a particular threshold, a recovery process is initiated. The recovery process utilizes backup nodes having overlapping sensing coverage with failed node and may also relocate some nodes. Firstly a backup node is probed and activated if available. If no backup node is found, the solution strives to recover coverage jointly by recursively relocating some mobile nodes and probing backup nodes. The proposed scheme is analyzed and validated through NS-2 based simulation experiments.     

A collaborative node management scheme for energy-efficient monitoring in wireless multimedia sensor networks

Clustering in sensor networks provides energy conservation, network scalability, topology stability, reducing overhead and also allows data aggregation and cooperation in data sensing and processing. Wireless Multimedia Sensor Networks are characterized for directional sensing, the Field of View (FoV), in contrast to scalar sensors in which the sensing area usually is more uniform. In this paper, we first group multimedia sensor nodes in clusters with a novel cluster formation approach that associates nodes based on their common sensing area. The proposed cluster formation algorithm, called Multi-Cluster Membership (MCM), establishes clusters with nodes that their FoVs overlap at least in a minimum threshold area. The name of Multi-Cluster Membership comes from the fact that a node may belong to multiple clusters, if its FoV intersects more than one cluster-head and satisfies the threshold area. Comparing with Single-Cluster Membership (SCM) schemes, in which each node belongs to exactly one cluster, because of the capability of coordination between intersected clusters, MCM is more efficient in terms of energy conservation in sensing and processing subsystems at the cost of adding complexity in the node/cluster coordination. The main imposed difficulty by MCM, is the coordination of nodes and clusters for collaborative monitoring; SCMs usually assign tasks in a round-robin manner. Then, as second contribution, we define a node selection and scheduling algorithm for monitoring the environment that introduces intra and inter-cluster coordination and collaboration, showing how the network lifetime is prolonged with high lifetime prolongation factors particularly in dense deployments.     

An efficient privacy-preserving scheme for secure network coding based on compressed sensing

Network coding (NC) provides an elegant solution for improving capacity and robustness in computer networks. Different to traditional “store-and-forward” transmission paradigm, each intermediate node linearly combines received data packets, and the original files can be decoded at the sink nodes in NC settings. This brand-new paradigm is vulnerable to pollution attack, which means that some malicious nodes inject fake data packets into the network and this will lead to incorrect decoding. There are some information-theoretical solutions and cryptographic solutions for solving this security issue, and most existing schemes can thwart data pollution attacks. However, the privacy of the original files are vital to some application environments (e.g. military network). To the best of our knowledge, there is not a secure scheme which can thwart pollution attack and can protect the privacy of transmitted data simultaneously. In this paper, we present an efficient privacy-preserving scheme for secure network coding based on compressed sensing (CS), which has attracted considerable research interest in the signal processing community. Specifically, we embed CS into the general NC framework, i.e., the source node needs to compress each original data packet using the sensing matrix before creating the augmented vector and the sink nodes require to perform an additional CS reconstruction algorithm for reconstructing the original file. In addition, we construct a simple key distribution protocol and each intermediate node just needs two secret keys for verifying the integrity of received data packets. Such novel hybrid construction enables the privacy-preserving guarantee, and the performance comparison shows the high-efficiency of our scheme in terms of the computational complexity and communication overhead.     

Polytype target coverage scheme for heterogeneous wireless sensor networks using linear programming

Sensing coverage is one of fundamental problems in wireless sensor networks. In this paper, we investigate the polytype target coverage problem in heterogeneous wireless sensor networks where each sensor is equipped with multiple sensing units and each type of sensing unit can sense an attribute of multiple targets. How to schedule multiple sensing units of a sensor to cover multiple targets becomes a new challenging problem. This problem is formulated as an integer linear programming problem for maximizing the network lifetime. We propose a novel energy‐efficient target coverage algorithm to solve this problem based on clustering architecture. Being aware of the coverage capability and residual energy of sensor nodes, the clusterhead node in each cluster schedules the appropriate sensing units of sensor nodes that are in the active status to cover multiple targets in an optimal way. Extensive simulations have been carried out to validate the effectiveness of the proposed scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

Connectivity-Guaranteed and Obstacle-Adaptive Deployment Schemes for Mobile Sensor Networks

Mobile sensors can relocate and self-deploy into a network. While focusing on the problems of coverage, existing deployment schemes largely oversimplify the conditions for network connectivity: they either assume that the communication range is large enough for sensors in geometric neighborhoods to obtain location information through local communication, or they assume a dense network that remains connected. In addition, an obstacle-free field or full knowledge of the field layout is often assumed. We present new schemes that are not governed by these assumptions, and thus adapt to a wider range of application scenarios. The schemes are designed to maximize sensing coverage and also guarantee connectivity for a network with arbitrary sensor communication/sensing ranges or node densities, at the cost of a small moving distance. The schemes do not need any knowledge of the field layout, which can be irregular and have obstacles/holes of arbitrary shape. Our first scheme is an enhanced form of the traditional virtual-force-based method, which we term the connectivity-preserved virtual force (CPVF) scheme. We show that the localized communication, which is the very reason for its simplicity, results in poor coverage in certain cases. We then describe a floor-based scheme which overcomes the difficulties of CPVF and, as a result, significantly outperforms it and other state-of-the-art approaches. Throughout the paper our conclusions are corroborated by the results from extensive simulations.     

Efficient deployment quality analysis for intrusion detection in wireless sensor networks

The intrusion detection in a Wireless Sensor Network is defined as a mechanism to monitor and detect any intruder in a sensing area. The sensor deployment quality is a critical issue since it reflects the cost and detection capability of a wireless sensor network. The quality of deterministic deployment can be determined sufficiently by a rigorous analysis before the deployment. However, when random deployment is required, determining the deployment quality becomes challenging. In the intrusion detection application, it is necessary to define more precise measures of sensing range, transmission range, and node density that impact overall system performance. The major question is centred around the quality of intrusion detection in WSN, how we can guarantee that each point of the sensing area is covered by at least one sensor node, and what a sufficient condition to guarantee the network connectivity? In this paper, we propose an appropriate probabilistic model which provides the coverage and connectivity in k-sensing detection of a wireless sensor network. We have proved the capability of our approach using a geometric analysis and a probabilistic model.     

A Distributed Node Localization Scheme for Wireless Sensor Networks

A distributed node localization scheme for wireless sensor networks (WSNs) is presented in this paper, and it includes three generic phases: (1) determine node-beacon distances, (2) compute node positions, and (3) refine the positions. Different from previous researches, we propose an algorithm combination Min–max + LI for the position derivation and SD method for the refinement in our scheme. Simulation shows that our proposed scheme can perform more robust than some representative distributed node localization schemes presented in previous researches in terms of the trade-off among accuracy, coverage, computation cost, and communication overhead.     

异构传感器网络覆盖势力剖分算法

对于普遍存在的异构传感器网络,目前尚缺乏有力的方法解决其覆盖势力的剖分问题。对此,该文提出一种本地化的覆盖势力剖分算法CFA(Coverage Force Algorithm)。该算法根据节点感应能力的差异,构建基于感应异构性的通用Voronoi图,能有效对网络中异构节点的覆盖势力范围进行剖分。实验证明,CFA算法解决了异构网络覆盖性能分析问题,和传统的Voronoi图方法相比,具有广普性和本地化的特点。     

Square partition‐based node scheduling algorithm for wireless passive sensor networks

Wireless passive sensor networks play an important role in solving the energy limitation of nodes in the Internet of Things, and node scheduling is a significant method used to improve the energy utilization of nodes. In this work, an unused energy model based on analyzing the energy consumption characteristics of passive nodes is proposed because no unified model of passive sensor nodes is reported in previous studies. A rapid square partition clustering method is proposed according to the analysis of the relation between the sensing and communication radii of nodes, and the secondary grouping and node scheduling in each cluster are implemented to ensure the coverage rate of networks. Experimental results show that the state distribution of nodes in the proposed algorithm is favorable. The performance of the proposed algorithm is significantly affected by the P ratio between the working and charging powers of nodes. When the value of P is less than 100, the network coverage and connectivity rate are maintained at more than 95% and 90%, respectively, and are both higher than the existing algorithm.     

A secure broadcasting scheme to provide availability,reliability and authentication for wireless sensor networks

Reliability and security of broadcasting is critical in Wireless Sensor Networks (WSNs). Since reliability and security compete for the same resources, we are interested in jointly solving for error control coding (to achieve reliability) and integrity for a broadcast scenario. We assume Byzantine attacks in which the adversary can compromise nodes and then drop (or modify) the legitimate packets or inject its own packets. For reliable and efficient multihop broadcasting, it is critical to reduce the energy consumption and latency. To prevent the adversary from consuming the scarce network resources by injecting bogus packets, each receiver node should make sure that packets it receives are authentic and it filters out malicious packets immediately. We build our authentication scheme, on top of a reliable and energy efficient broadcasting protocol called Collaborative Rateless Broadcast (CRBcast) to improve efficiency and reliability. On contrary to the previous schemes, our scheme is resilient with respect to Byzantine adversary as well as routing and flooding attacks and protocol exploits. Moreover, we compared our scheme with the previously proposed broadcast authentication schemes and showed that our scheme outperforms them in terms of efficiency and data availability. This is a crucial improvement over the previous schemes that ensure availability by flooding, introducing very large communication overhead and latency.     

Strongly unforgeable threshold multi‐proxy multi‐signature scheme with different proxy groups

In the majority of threshold multi‐proxy multi‐signature (TMPMS) schemes, only one proxy group is authorized to sign on behalf of all the original members. However, the original signers in various practical applications are often from different organizations. Each original signer should be able to designate a proxy group in his own organization; thus, each original signer could have distinct proxy members. However, this practical requirement of TMPMS schemes is seldom considered. To satisfy this requirement, we propose a new TMPMS scheme in which each original member can designate a proxy group in his own organization. Moreover, the threshold value of each proxy group is unique. We develop a security model to prove the high security and strong unforgeability of the proposed scheme. We analyze the security of our scheme based on the four types of adversaries tested in the security model. Compared with previous schemes, the new scheme offers higher security and superior computational efficiency. Copyright © 2013 John Wiley & Sons, Ltd.     

一种同时保障隐私性与完整性的无线传感器网络可恢复数据聚合方案

该文针对无线传感器网络(WSNs)数据聚合与安全目标之间的矛盾,基于隐私同态和聚合消息验证码技术提出一种同时保障数据隐私性与完整性的可恢复数据聚合方案。该方案支持由聚合结果恢复出各感知数据,从而一方面能够验证感知数据和聚合数据的完整性,另一方面能够对原始数据进行任意所需的处理,不受聚合函数类型的限制。安全分析表明该方案不仅支持数据隐私性、完整性,还能够抵抗未授权聚合攻击,聚合节点俘获攻击,且能够在一定范围内检测及定位恶意节点。性能分析表明,该方案相比其他算法在通信和计算开销方面具有显著优势。为了评估方案性能和可行性,基于TinyOS给出了算法的原型实现。实验结果表明,该方案开销较低,对于资源受限的WSNs是高效可行的。     

基于感知距离调节的无线传感器网络节能区域覆盖

传感器节点能够感知的物理世界的最远距离称为节点的感知距离。该文研究了基于节点感知距离调节的无线传感器网络节能区域覆盖方案,该方案通过设定合理的节点感知距离,使得传感器网络在满足区域覆盖要求的同时,能量消耗最低。首先将区域覆盖性能和网络能量消耗模化成网络节点感知距离的函数,然后将节能覆盖问题模化成带约束条件的优化问题,最后给出了基于网络区域划分的优化模型求解方法。仿真结果表明,与传统覆盖方案比较,所提方案在满足覆盖要求的同时,有效降低了网络能量消耗。     

LNT: A logical neighbor tree secure group communication scheme for wireless sensor networks

Secure group communication is a paradigm that primarily designates one-to-many communication security. The proposed works relevant to secure group communication have predominantly considered the whole network as being a single group managed by a central powerful node capable of supporting heavy communication, computation and storage cost. However, a typical Wireless Sensor Network (WSN) may contain several groups, and each one is maintained by a sensor node (the group controller) with constrained resources. Moreover, the previously proposed schemes require a multicast routing support to deliver the rekeying messages. Nevertheless, multicast routing can incur heavy storage and communication overheads in the case of a wireless sensor network. Due to these two major limitations, we have reckoned it necessary to propose a new secure group communication with a lightweight rekeying process. Our proposal overcomes the two limitations mentioned above, and can be applied to a homogeneous WSN with resource-constrained nodes with no need for a multicast routing support. Actually, the analysis and simulation results have clearly demonstrated that our scheme outperforms the previous well-known solutions.     

Energy Efficient Non-uniform Clustering Division Scheme in Wireless Sensor Networks

Wireless sensor networks can be used to monitor the interested region by multi-hop communication. Since sensor nodes are equipped with energy-limited batteries, energy conservation in such networks is of paramount importance in order to prolong the network lifetime. In this paper, considering the constrained radio range of node, we propose an energy efficient clustering division scheme from the viewpoint of energy consumption. The difference between our scheme and previous schemes is that ours is a non-uniform clustering hierarchy. With the algorithm that is proposed by this paper, we can divide the cluster into multiple non-uniform concentric rings and obtain the optimal thickness of each ring. Motivated by the derived results, every sensor node can adjust its radio range for transmission. Our extensive simulation results indicate that the proposed non-uniform clustering division scheme outperforms the conventional uniform clustering division schemes in terms of energy consumption and lifetime. The future research that should be explored is also discussed finally.