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The development of wireless sensor and actuator network is leading to high complexity networks and subsequently, new challenges in task assignment for effective sensor–actuator coordination. This article proposes an adaptive auction protocol for task assignment in multi-hop wireless actuator networks, considering a scenario where all actuators are immobile and each of them can obtain the target information from sensors. Unlike existing methods that neglect the adaptive auction area required by dynamic networks, the proposed method uses an adaptive factor k o (reflects the adaptive auction area) that is deduced based on the relation between network characteristics and protocol performance. Simulation results show that the adaptive protocol can dynamically change the auction area during the network operation. In addition, comparison with existing methods, such as simple auction protocol, 1 hop simple auction aggregation protocol, and 1 hop simple auction aggregation protocol greedy extension, shows that the adaptive auction protocol can choose the optimal solution at a low communication cost with a high probability, irrespective of the changes in the network. [ABSTRACT FROM AUTHOR]

Nodes in a wireless sensor network are normally constrained by hardware and environmental conditions and face challenges of reduced computing capabilities and system security vulnerabilities. This fact calls for special requirements for network protocol design, security assessment models, and energy-efficient algorithms. Data aggregation is an effective energy conservation technique, which removes redundant information from the data aggregated from neighbor sensor nodes. How to further improve the effectiveness of data aggregation plays an important role in improving data collection accuracy and reducing the overall network energy consumption. Unfortunately, sensor nodes are normally deployed in an open environment and thus are subject to various attacks conducted by adversaries. Consequently, data aggregation brings new challenges to wireless sensor network security. In this article, we propose a novel secure data aggregation solution based on autoregressive integrated moving average model, a time series analysis technique, to prevent private data from being learned by adversaries. We leverage the autoregressive integrated moving average model to predict the data volume in sensor nodes, and update and synchronize the model as needed. The experimental results demonstrate that our model provides accurate predictions and that, compared with competing methods, our solution achieves better security, lower computation and communication costs, and better flexibility. [ABSTRACT FROM AUTHOR]

In this article, we propose a time division multiple access scheduling algorithm for end-to-end on-time packet delivery in multi-hop wireless sensor networks. Our proposed algorithm establishes a new communication path to substitute the old path including the link failed and schedules communication links on the new path by allocating timeslots satisfying end-to-end delay bound. Max-min optimization is employed to maximize the number of dedicated timeslots to establish the substitute path in the event of the next link failure. We evaluate the performance of the proposed algorithm using QualNet network simulator and compare it with the performance of the algorithm that minimizes the end-to-end delay. Our numerical results show that the path survival ratio of the proposed algorithm is approximately two times higher when large number of communication links fails. In addition, we apply the global recovery and local recovery schemes to observe the increase in the overhead message exchanges. Compared to the global recovery scheme, local recovery scheme requires six times less control messages to establish the substitute path when a small number of link failures occur, whereas more than 90% communication paths survive. [ABSTRACT FROM AUTHOR]

Various protocols have been proposed in the area of wireless sensor networks in order to achieve network-wide time synchronization. A large number of proposed protocols in the literature employ a message passing mechanism to make sensor node clocks tick in unison. In this paper, we first classify Message Passing based Time Synchronization (MPTS) protocols and then analyze them based on different metrics. The classification is based on the following three criteria: structure formation of the network affected by the synchronization protocol, frequency of synchronization process (synchronization interval), and synchronization message overhead. Proposed protocols are analyzed and evaluated from different perspectives based on available data. A comparison table of the reviewed protocols is presented according to the evaluation metrics. Finally, some potential methods will be proposed to improve the synchronization process. [ABSTRACT FROM AUTHOR]

This thesis presents a mural broadcast authentication protocol (MBAP) for wireless sensor networks based on Fourier series according to the issues of the main broadcast authentication protocol µTESLA being limited in authentication delay, more initial parameters, limited time, large key chain, and network congestion. Firstly, achieving the forward authentication work for common sensor nodes to base station is based on the characteristic of continuous-integrability function f(x) in [-π,π] which could be expanded into Fourier series, including entity authentication and source attestation. Secondly, assume that f(x) is the quadratic form function, and achieve the reverse authentication work for base station to common sensor nodes by detecting the security of f(x). The analysis results of safety performance in MBAP show that the captured nodes in WSN will not affect the security of broadcast authentication protocol and have low computation and communication cost, the base station can make broadcast randomly, and common sensor nodes can authenticate messages instantly, which solves the problem of network congestion well. The most important thing of MBAP is the mutual broadcast authentication method which ensures the security of the network greatly. [ABSTRACT FROM AUTHOR]

This paper proposes receiver-initiated X-MAC with tree topology (TRIX-MAC), an improved energy-efficient MAC protocol based on an asynchronous duty cycling for wireless sensor networks with tree topology. TRIX-MAC improves energy efficiency through utilizing short preambles and adopting the receiver-initiated approach that minimizes sender nodes’ energy consumption by enabling transmitters to predict receiver nodes’ wake-up times and reduces receiver nodes’ energy consumption by decreasing the number of control frames. In many sensor network applications, the data flow from source nodes to a sink forms a unidirectional tree. A property of tree topology, the parent-child relation, is also exploited to reduce the likelihood of collisions between frames sent by children nodes. We use the network simulator, ns-2, to evaluate TRIX-MAC’s performance. Compared to the prior asynchronous duty cycling approaches of X-MAC, RIX-MAC, and PW-MAC, the proposed protocol shows better performance in terms of throughput, energy efficiency, and end-to-end delay. [ABSTRACT FROM AUTHOR]

Secure key distribution is one of the most important building blocks to ensure confidentiality in wireless sensor and actor networks (WSANs). However, the key distribution becomes a challenging task when keys have to be relayed by compromised nodes in order to establish secure communication between distant nodes. To deal with this issue, we propose in this paper a key distribution scheme, named key distribution using fragmentation and assimilation (KDFA). In this scheme, the sender node splits the actual key into fragments and sends them through intermediate actor nodes towards the receiver node. The latter assimilates these key fragments using XOR operation to reconstruct the actual key. In this case, attacker cannot retrieve the actual key and only gets the key fragment. KDFA is composed of two parts: (a) key distribution protocol (KDP) to distribute the key using intra-actor and interactor communication scenarios and (b) key fragmentation algorithm (KFA) to slice the key using binary calculations. KDFA execution has been specified and formally verified using Rubin logic. Moreover, the performance and the resilience of the proposed protocol are further analyzed through extensive simulations using ns-2.35. Results show that KDFA is resilient against actor node compromise and key exposure. [ABSTRACT FROM AUTHOR]

Due to the imbalanced energy consumption among nodes in wireless sensor networks, some nodes die prematurely, which decreases the network lifetime. To solve this problem, existing clustering protocols usually construct unequal clusters by exploiting uneven competition radius. Taking their imperfection on designing the uneven competition radius and intercluster communication into consideration, this paper proposes an improved distributed unequal clustering protocol (IDUC) for wireless sensor networks, where nodes are energy heterogeneous and scattered unevenly. The cores of IDUC are the formation of unequal cluster topology and the construction of intercluster communication routing tree. Compared with previous protocols, IDUC is suitable for various network scenarios, and it can balance the energy consumption more efficiently and extend the lifetime of networks significantly. [ABSTRACT FROM AUTHOR]

A dynamic heterogeneous and multihop (DHMH) wireless health monitoring system (WHMS) as a three-tier semi-self-organizing health monitoring network was presented. From bottom to top, the first tire of the network is the mobile data acquisition layer (DAL), the second tire of the network is the data transporting layer (DTL), and the third tire of the network is the data collection layer (DCL). A RF power control based topology management mechanism is proposed to balance the network load and to improve the network throughput. A lightweight hierarchical routing protocol (LHRP) was designed to reduce the transmission delay and improve the network throughput. For the mobile DAL nodes, the seamless mobile access mechanism (SMAM) was designed to ensure the low packet loss ratio. To evaluate the network performance, the end-to-end delay, the averaged reception ratio, and the network throughput of the DHMH were tested and the results proved that the network performance of the DHMH was improved. [ABSTRACT FROM AUTHOR]

Wireless sensor networks (WSNs) are a family of wireless networks that usually operate with irreplaceable batteries. The energy sources limitation raises the need for designing specific protocols to prolong the operational lifetime of such networks. These protocols are responsible for messages exchanging through the wireless communications medium from the sensors to the base station (sink node). Therefore, the determination of the optimal location of the sink node becomes crucial to assure both the prolongation of the network’s operation and the quality of the provided services. This paper proposes a novel algorithm based on a Particle Swarm Optimization (PSO) approach for designing an energy-aware topology control protocol. The deliverable of the algorithm is the optimal sink node location within a deployment area. The proposed objective function is based on a number of topology control protocol’s characteristics such as numbers of neighbors per node, the nodes’ residual energy, and how they are far from the center of the deployment area. The simulation results show that the proposed algorithm reveals significant effectiveness to both topology construction and maintenance phases of a topology control protocol in terms of the number of active nodes, the topology construction time, the number of topology reconstructions, and the operational network’s lifetime. [ABSTRACT FROM AUTHOR]

Constructive interference (CI) is a synchronous transmission technique for multiple senders transmitting the same packet simultaneously in wireless sensor networks (WSNs). CI enables fast and reliable network flooding in order to reduce the scheduling overhead of MAC protocols, to achieve accurate time synchronization, to improve link quality of lossy links, and to realize efficient data collection. By achieving microsecond level time synchronization, Glossy realizes millisecond level CI-based flooding and 99% reliability. However, Glossy produces substantial unnecessary data forwarding, which significantly reduces the network lifetime. This is a very critical problem, especially in energy-limited large-scale wireless sensor networks for agriculture and forestry (WSN-AF) system. In this paper, we present an energy adaptive CI-based flooding protocol (EACIF) by exploiting CI in WSN-AF. EACIF proposes a distributed active nodes selection algorithm (ANSA) to reduce redundant transmissions, thereby significantly reducing energy consumption and flooding latency. We estimate the performance of EACIF both with real data traces and with uniformly distributed topology. Simulation results show that EACIF achieves almost the same packet reception ratio (PRR) as Glossy (e.g., 99%), while reducing 63.96% energy consumption. EACIF also reduces 25% flooding latency. When the packet interval is 30 seconds, EACIF achieves 0.11% duty cycle. [ABSTRACT FROM AUTHOR]

A 2.45 GHz active integrated ZigBee RFID system embedded with GPS is developed with an automated switching protocol algorithm utilizing wireless sensor network (WSN) platform to track the physical belongings or people in indoor and outdoor environments within a control area. In addition, to make the system contactless when the tag is not joining the network, the function of global system for mobile (GSM) communication is added to the integration. The communication between RFID reader and RFID tags is via WSN platform that supports mesh network and self-healing mechanism. Energy efficiency, robustness, and reliability are key factors in the design algorithm of the system. Comparisons are made between the existing active RFID system and the proposed active RFID system to study the performance of the proposed RFID system with an automated switching algorithm implemented on it. Based on the experimental study and statistical analysis done for all situations, a conclusion has been made where the proposed embedded RFID tag provided better signal propagation compared to the existing RFID tag and the battery lifetime for embedded RFID tag with switching mechanism is better than without switching mechanism. [ABSTRACT FROM AUTHOR]

Packet corruption caused by collision is a critical problem that damages the performance of wireless networks. Traditional medium access control (MAC) protocols resort to collision avoidance to improve the efficiency of channel utilization. According to our investigation, however, collision avoidance causes time delay, which also hurts channel utilization, especially in the dense networks or intensive traffic. Discovering the ability to tolerate collisions with the correlatable preamble at the physical layer implementations of wireless networks, we propose CWM in this paper, a MAC protocol that advocates simultaneous accesses from multiple senders to a shared channel, allowing collisions instead of avoiding them. With the correlatable sequences, CWM addresses the challenges in achieving collision tolerance, such as precise sender alignment and control of the transmission concurrency. We implement the experiments on USRP verifying the feasibility of our protocol and implement CWM in 802.15.4 networks and evaluate its performance with 100 nodes on MATLAB. The results demonstrate that our protocol significantly improves the spatial reuse of the wireless channel by at least 23% compared with the state-of-the-art protocols. [ABSTRACT FROM AUTHOR]

Traditional wireless sensor networks (WSNs) work over the unlicensed spectrum, and as the spectrum becomes increasingly crowded, they suffer from uncontrolled interference. Recently, cognitive radio based sensor networks (CRSNs) have been envisioned as a promising type of implementation that provides quality-of-service (QoS) features for data transmissions. However, key challenges remain in designing energy-efficient medium access control techniques that can achieve QoS. In this paper, we have developed a multiconstrained QoS aware MAC protocol, MQ-MAC, for a cluster based CRSN. In MQ-MAC, a data channel and a backup channel are assigned to a secondary user by the respective cluster head by using dynamic channel priorities. The user device can switch to the backup channel when a primary user appears to be operating over the data channel. Member nodes of a cluster are also prioritized with respect to the urgency of their generated data packets. Performance evaluations, carried out in NS-3 simulator, show that the proposed MQ-MAC protocol offers better performance than existing MAC protocols for CRSN. [ABSTRACT FROM AUTHOR]

Wireless Sensor Networks are a key element of the Internet of Things since they are one of the most interesting pervasive systems. However, they are battery-powered, so energy efficiency represents one of the primary design challenges to address. This goal can be primarily achieved through an optimization of the communication procedure, which is the most power-consuming component of a WSN node. Nevertheless, the poor resources of the embedded devices usually limit the complexity of protocol solutions, which thus are not sufficient to reach satisfactory results. For this reason, the current trend aims at integrating both hardware and software solutions. In this work, a cross-layer solution, based on the combined use of a duty-cycling MAC protocol and a reconfigurable beam-steering antenna, is presented and validated. It significantly reduces the nodes’ power consumption by exploiting scheduling techniques and directional communications. Specifically, a MAC scheduler manages the activation of the antenna sectors based on information coming from both MAC and network layers. This way, node awakenings occur only when an actual communication has to take place and only the interested antenna sector is activated. The effectiveness of the proposed cross-layer approach has been evaluated through OMNeT++ simulation tool. [ABSTRACT FROM AUTHOR]

Owning to the proliferation of cost-effective sensors, there has been an increased growth in a number of applications of wireless sensor networks (WSNs). In addition, the skyline operator as well as its variants such as the dynamic skyline and reverse skyline operator has attracted increasing attention since those are useful for multicriteria decision making applications. Since the energy efficiency is utmost important issue to prolong the network lifetime, in this paper, we proposed efficient algorithms to process a reverse skyline query over a sliding window in WSN environments. We first devise our algorithm for the data stream environments and extend it to WSN environments. To compute the reverse skyline, we partition the data space into several orthants with respect to a query point. And, in each orthant, we compute the reverse skyline independently using two buffers. In our experiment study, we demonstrate that our algorithm is much better than other algorithms. [ABSTRACT FROM AUTHOR]

Wireless sensor network (WSN) is built of many sensor nodes. The sensors can sense a phenomenon, which will be represented in a form of data and sent to an aggregator for further processing. WSN is used in many applications, such as object tracking and security monitoring. The objects in many situations need physical and location protection. In addition to the source location privacy, sink location privacy should be provided. Providing an efficient location privacy solution would be challenging due to the open nature of the WSN. Anonymity is a key solution for location privacy. We present a network model that is protected against local, multilocal, and global adversaries that can launch sophisticated passive and active attacks against the WSN. [ABSTRACT FROM AUTHOR]

Technological advances within the area of wireless sensor technology allow WSNs to be used in a increasing number of measurement scenarios. As new application areas are emerging, such as infrastructure monitoring and smart cities, the need for sensor mobility handling requires efficient and secure authentication protocols. This paper presents EAP-Swift, a novel EAP based authentication protocol with a focus on lightweight processing and faster response. It supports end-to-end session encryption key generation and mutual authentication. By utilizing lightweight hashing algorithms, the challenge-response authentication mechanism uses only two round trips to the AAA server for the complete authentication procedure leading to the reduction of latency by 33% compared to the baseline protocols. Further, using extensive experimentation, we validate that the authentication time can be kept below 250 ms and the power consumption can be kept below 15 mJ. Furthermore, we show that a battery lifetime of more than four years can be achieved when running the system on a regular button cell battery. Finally, the protocol was verified in terms of security using the AVISPA tool. [ABSTRACT FROM AUTHOR]

Applications based on video and image in wireless sensor network are highly attractive due to their wealth of information. In this context, application for object recognition and tracking using image and video information is one the attractive approaches that can be applied for event detection and localization, security processes, following of the rare animal species and control of road traffic, and so forth. However, the implementation of such approach with WMSN requires a specific image processing scheme and efficient transmission protocol. In fact, because of the limited energy of the batteries embedded in motes, the power consumption is the major constraint facing network life time and reliability in WMSN. The efficiency and the validity of these multimedia applications over wireless sensor networks are then dependent on the capabilities of the designer to provide low-power scheme for data processing and energy-aware transmission protocols. This paper presents a contribution to the design of low complexity scheme based on object identification for efficient sensing of multimedia information in wireless multimedia sensor networks. It proposes a new solution and explores the associated performances of this scheme. The presented results in this paper attest the high efficiency to achieve low-power objects identification when implemented in wireless motes. [ABSTRACT FROM AUTHOR]

Real-time applications are time and event critical, therefore they have strict constraint on delay, packet loss, and energy consumption in many wireless sensor networks (WSNs) scenarios, which demands the network to continue QoS operations for a preconfigured lifetime. Due to the scarce energy constraint sensor nodes in WSNs, guaranteed network lifetime is more desirable than unpredictable and uncertain prolonged lifetime. However, in spite of its importance and necessity in WSNs real-time deployment, no research work has been proposed to solve this complex problem. In this paper, we present a new centralized energy and coverage aware node scheduling scheme for WSNs to analyze energy usage as well as balancing energy consumption among nodes to survive for the reconfigured lifetime. Furthermore, the scheduling algorithm is extended to provide real-time routing by adjusting dynamic transmission range according to current energy state of a sensor node. Thus, the energy and coverage aware scheduling with dynamic range forwarding enables the unreliable WSNs to accomplish real-time routing for a guaranteed network lifetime. Simulation results show that the proposed scheme can achieve a 10% increase in real-time packets meeting their deadline and a significantly longer guaranteed network lifetime than protocols reported in the literature. [ABSTRACT FROM AUTHOR]

Owing to complementary characteristics of wireless networks, it is deserved to achieve automatic handoff on the modern smartphone for taking full exploitation of these accessible technologies. In this paper, we have proposed the closed loop model on smartphone switching heterogeneous wireless networks, which is full-client based without requiring additional support from the access points or gateways and modification of the network protocols. It only intuitively takes advantage of user scheme as the feedback adjustment approach to handoff policy. Furthermore, we have analyzed the closed loop handoff model to illustrate and evaluate how the user feedback of the policy acts on adapting to change context. In the experiment, we have evaluated four metrics on the closed loop handoff policy in real smartphone device: performance, energy saving, data offloading, and user experience. [ABSTRACT FROM AUTHOR]

Secure time synchronization is one of the key concerns for Underwater Wireless Sensor Networks (UWSNs).his paper presents a CLUster-based Secure Synchronization (CLUSS) protocol that ensures the security of synchronization under harsh underwater environments against various attacks, including Sybil attack, replay attack, message manipulation attack, and delay attack. The time synchronization process of CLUSS is divided into three phases: authentication phase, intercluster synchronization phase, and intracluster synchronization phase. During the authentication phase, cluster heads are authenticated to beacons and ordinary nodes are authenticated to cluster heads. During the process of intercluster and intracluster synchronization phases, CLUSS distinguishes the propagation delay of downlink from that of uplink caused by node movement in order to improve time synchronization accuracy. Moreover, part of these two phases can be executed concurrently for reducing the number of messages generated in synchronization. We demonstrate through simulations that CLUSS can reduce synchronization errors as well as energy consumption compared to traditional protocols in various circumstances. [ABSTRACT FROM AUTHOR]

Several strategies to evaluate the power consumption of of wireless sensor networks (WSNs) have been proposed. The limited amount of energy and the difficulty of recharging them have demanded the emerging of these strategies. However, to evaluate the lifetime of a WSN is not a trivial task due to the complexity of reproducing the environment, inherent dynamism, and complexity and size of WSNs. In this context, we present an approach for evaluating the WSN lifetime by simulating its power consumption using models. This approach consists of a fully automated process for evaluating the WSN lifetime, a set of reusable Coloured Petri Net (CPN) models that express the power consumption of WSN communication protocols, and a strategy for composing CPN models of WSN applications and protocols. In order to assess our power consumption models, we carried out an experimental evaluation that compares the results obtained by simulation against ones existing in the literature. [ABSTRACT FROM AUTHOR]

Healthcare service sector is one of the major applications of Wireless Sensor Networks (WSNs) acknowledged as Wireless Medical Sensor Network (WMSNs). It deploys tiny medical sensor-nodes (MS-nodes) on the body of the patient to sense crucial physiological signs which can be accessed and analyzed by registered medical professionals. Recently, Khan et al. analyzed Kumar et al.'s scheme proposed for healthcare applications using WMSNs and observed that the scheme is susceptible to many security weaknesses if an adversary extracts the information from the lost smart card of some user. The adversary can access patient's physiological data without knowing actual password, can deceive medical professionals by sending fake information about patients, can guess the password of a user from the corresponding smart card, and so forth. Besides, the scheme fails to resist insider attack, lacks user anonymity and the session key shared between the user and the MS-node is insecure. To overcome these problems, we propose an improved user authentication scheme for healthcare applications using WMSNs. We show that the scheme is free from the identified weaknesses and excels in performance and efficiency scheme. [ABSTRACT FROM AUTHOR]

IEEE 802.15.4 PHY has been widely used in wireless sensor networks. In-depth investigations on the link layer characteristics are important for WSN protocol design. In industrial environments, link reliability is vulnerable to various interferences; therefore, many schemes have been employed for reliability improvements such as multichannel access, frequency hopping, and multipath routing, which put forward the demand on link reliability models. Previous researches mainly focus on distance fading and irregularity of link reliability; however, little work analyses the temporal and frequency variations of the link reliability. The paper proposed a link layer statistical model (LTM) for time-varying of 16 channels based on packet drop rate (PDR) data collected from typical industrial environments. LTM descript packet drop intervals, PDR variation over times, PDR variation between different channels, link level switching probability and interference distribution. And also, a discussion of the influence of IEEE 802.15.4e MAC protocol simulation showed that LTM is closer to the realistic result. This paper provides a new metho d to model link reliability in industrial environment and is useful to the design of frequency diversity and upper layer protocols. [ABSTRACT FROM AUTHOR]

A wireless sensor network consisting of resources, size, and cost-limited sensors is used in many military and civil applications. This paper proposes an energy-efficient clustering algorithm that extends the lifetime of sensor networks. The proposed clustering algorithm is an extended hierarchical clustering protocol that minimizes the overall amount of consumed energy in the network. The proposed approach dynamically updates clusters and distributes the load on the heavily loaded cluster heads among different nodes. It also balances the remaining energy on nodes in the network, which leads to prolonged network lifetime. The performance is evaluated in terms of network lifetime, average energy consumption, and standard deviation of residual energy. [ABSTRACT FROM AUTHOR]

There have been increasing demands for research into multi-channel-based wireless sensor network protocols and applications to support requirements such as increased throughput and real-time or reliable transmission. Researchers or developers of these protocols and applications have to simultaneously analyze the exchanged packets for correctness of both their contents and message exchange timelines. However, if developers were to use multiple conventional single-channel packet sniffers for this purpose, debugging during development and the verification process becomes extremely tedious and difficult because of the need to check the correctness of the protocols over multiple channels individually. Therefore, we present a multi-channel packet-analysis system (MPAS) that helps in debugging and verification for multi-channel protocols or applications. Wireless packets are detected and timestamped by each sniffer module in the MPAS for each channel, and packets are preprocessed and transmitted to a GUI-based analyzer, which then parses the received packets and shows them in order. We present the design and implementation results of the MPAS and evaluate its performance by comparing it against a widely used packet sniffer. [ABSTRACT FROM AUTHOR]

We propose forwarding-function (FF) based routing protocol for underwater sensor networks (UWSNs): improved adaptive mobility of courier nodes in threshold-optimized depth-based-routing (iAMCTD). Unlike existing depth-based acoustic protocols, the proposed protocol exploits network density for time-critical applications. In order to tackle flooding, path loss, and propagation latency, we calculate optimal holding time (HT) and use routing metrics: localization-free signal-to-noise ratio (LSNR), signal quality index (SQI), energy cost function (ECF), and depth-dependent function (DDF). Our proposal provides on-demand routing by formulating hard threshold (Hth), soft threshold (Sth), and prime energy limit (Rprime). Simulation results verify effectiveness and efficiency of the proposed iAMCTD. [ABSTRACT FROM AUTHOR]

Wireless multimedia sensor networks (WMSNs) are more and more wildly used for a variety of applications nowadays. The quality-of-service (QoS), as a measure of system performance, is very important and attracts many researchers. The limited bandwidth should be adjusted for the packets with different priorities precisely. Even more, when the WMSNs are used for environment monitoring, besides the real-time video playing, the monitoring systems also need to record and playback the video after some time. So the necessary and proper retransmission should be added to the real-time video transmission, without affecting the normal data streams. To emphasize the problem, the paper provides a flexible and reliable traffic control protocol. According to the packet priorities, sensor nodes in one collision area can adjust their sending states adaptively. Variable retransmission tactics are provided for the packets with different priorities. The simulations show that the bandwidth adjustment can protect the packets with high priority effectively, and the performance of the retransmission is well positioned to meet the requirement of the multimedia applications. [ABSTRACT FROM AUTHOR]

We propose a TDMA-based protocol for mobile sensor networks. The proposed protocol overcomes the shortcomings of the other available TDMA-based protocols in a dynamic network where the cluster membership may change frequently. Unlike other existing TDMA-based protocols, we propose to vary the number of timeslots in the TDMA frame to allow underutilization of unused slots and successful allocation of timeslots to the newly joined sensors through minimizing collisions. The approach is fully decentralized and efficient to be used by the cluster head (leader) and the sensor nodes in a cluster. Simulations also show that the proposed mechanism provides significant performance improvements compared to the other existing approaches in terms of different network performance metrics. [ABSTRACT FROM AUTHOR]

While many protocols for sensor network security provide confidentiality for message content, contextual information usually remains exposed, which can be critical to the mission of the sensor network. In this paper, we propose an energy-efficient cyclic diversionary routing (CDR) scheme against global eavesdroppers for preserving location privacy and maximizing lifetime of wireless sensor networks (WSNs). To ensure no impact on lifetime of WSNs, we minimize the energy consumption of hotspots and generate abundant diversionary routing paths in areas far from sink. To enhance the location privacy preservation, we theoretically figure out the probability of the cyclic interference routings in different areas of the network and statistically achieve an energy consumption balance in the entire network. Analysis and simulation results show that CDR significantly improves the security in source-location privacy preservation without reducing the network lifetime. [ABSTRACT FROM AUTHOR]

Multichannel communication protocols have been developed to alleviate the effects of interference and consequently improve the network performance in wireless sensor networks requiring high bandwidth. In this paper, we propose a contention-free multichannel protocol to maximize network throughput while ensuring energy-efficient operation. Arguing that routing decisions influence to a large extent the network throughput, we formulate route selection and transmission scheduling as a joint problem and propose a Reinforcement Learning based scheduling algorithm to solve it in a distributed manner. The results of extensive simulation experiments show that the proposed solution not only provides a collision-free transmission schedule but also minimizes energy waste, which makes it appropriate for energy-constrained wireless sensor networks. [ABSTRACT FROM AUTHOR]

In wireless sensor networks (WSN), Sybil attack can destroy the routing and data distributed storage mechanisms through fabricating identity information of legitimate nodes. This paper presents a chain key predistribution based approach against Sybil attack. To enhance the security of common keys between neighboring nodes, during the chain key predistribution phase, our approach uses a lightweight hash function to generate several chain keys by hashing the unique identity information of every node sequentially in the trusted base station. These chain keys construct a pool of chain keys. During the pairwise key authentication establishment phase, a node-to-node chain key based authentication and exchange (CK-AE) protocol is proposed, by which each node can share the unique pairwise key with its neighboring node. The CK-AE protocol is provably secure in the universally composable security model (UCSM). Finally, we analyze our approach from the resilience of network and the performance overhead, and the results show that our approach can not only enhance the ability of resilience to Sybil attack, but also reduce the communication overhead significantly at the cost of a certain amount of computational overhead. [ABSTRACT FROM AUTHOR]

In industrial contexts, most of process control applications use wired communication networks. The reliability of wired networks is indisputable and extensively demonstrated by several studies in the literature. However, it is important to consider several disadvantages provided by the use of wired technologies, like high deployment and maintenance costs and low network scalability. Although it is difficult to fully replace wired networks, wireless communication protocols have features which could undeniably affect in positive way the production mechanisms in factories. The wireless networks (WNs) are effectively used to detect and exchange information. The main communication protocols, currently available for WNs, however, do not support real-time periodic traffic flows which, as known, mainly characterize industrial networks. In this paper, we will analyze a real-time scheduling algorithm for both periodic and aperiodic traffic management, applied to networks based on IEEE 802.15.4 and Bluetooth, respectively. The main purpose of this research is to reduce, as much as possible, the packet loss on the channel, increasing at the same time the reliability of the wireless technology. Furthermore, the comparison between IEEE 802.15.4 and Bluetooth will allow to identify the more suitable communication protocol for industrial process control systems. [ABSTRACT FROM AUTHOR]

Energy awareness is a vital design issue in wireless sensor networks. Since the amount of sensing data may be large and sensor nodes are usually battery-powered, it is critical to design energy-efficient routing algorithms to prolong network lifetime. Given a certain sensor deployment, the routing strategy of sensor data would have profound effects on the communication cost. In this paper, based on low-energy adaptive clustering hierarchy (LEACH) series protocols which are low-energy consumption adaptive clustering routing protocols, we propose the OVSF mechanism based routing protocol and EERPP (Energy-Efficient Routing Protocol based on Priority). Simulation results of OVSF mechanism based protocol and EERPP demonstrate a significant improvement on the network metrics such as the lifetime and the end-to-end delay. [ABSTRACT FROM AUTHOR]

Improving the end-to-end performance of TCP over wireless networks has been an active research area. When TCP operates in wireless networks, the performance of TCP degrades significantly. It is well known that frequent retransmission timeouts are the leading source of TCP performance degradation over wireless networks. Retransmission timeouts are unavoidable, when the fast retransmission of a lost packet fails to reach the destination. There have been many schemes developed for reducing the retransmission timeouts of TCP. However, these schemes have no mechanism to detect the loss of fast retransmitted packets over wireless networks. In this paper, we introduce an efficient TCP mechanism, called T-DLRP, which is able to detect the loss of fast retransmitted packets and react accordingly. To justify our contributions, we compared T-DLRP against TCP New Reno, Vegas, New Jersey, Veno, Cerl, and DAC via extensive simulations using Qualnet 4.5 simulator. The results demonstrate that our mechanism achieves significant improvement over existing TCP variants especially in a coexisted network with packet loss and fast retransmission losses. Compared to DAC, T-DLRP gains more than 70% improvement in terms of accuracy over wireless networks. Also, our experiments of multiple connections of the same TCP flows reveal that T-DLRP has better fairness compared to TCP NewReno. [ABSTRACT FROM AUTHOR]

Data broadcast is a fundamental operation in wireless sensor networks (WSNs). The existence of wireless interference makes it nontrivial to design a minimum-latency broadcast scheme, which is known to be NP-hard. Existing works all assume strict time synchronization and provide centralized TDMA scheduling algorithms. However, WSNs in practice are more likely to be distributed asynchronous systems. In this paper, we investigate the problem of data broadcast with minimum latency for distributed asynchronous WSNs. To this end, we propose a Distributed Asynchronous Broadcast (DAB) algorithm which crucially leverages an elaborately optimized carrier-sensing range together with collision-backoff schemes to coordinate the transmissions among the nodes on a predetermined broadcast backbone. Theoretical analysis shows that DAB is order-optimal and achieves constant factor approximation to the optimal delay. We then conduct extensive simulations to evaluate the practical capability of DAB in asynchronous WSNs and the results corroborate our theoretical analysis. [ABSTRACT FROM AUTHOR]

Target tracking is a typical and important application of wireless sensor networks (WSNs). In consideration of the network scalability and energy efficiency for target tracking in large-scale WSNs, it has been employed as an effective solution by organizing the WSNs into clusters. However, tracking a moving target in cluster-based WSNs suffers a boundary problem when the target moves across or along the boundaries of clusters, as the static cluster membership prevents sensors in different clusters from sharing information. In this paper, we propose a novel mobility management protocol, called hybrid cluster-based target tracking (HCTT), which integrates on-demand dynamic clustering into a cluster-based WSN for target tracking. By constructing on-demand dynamic clusters at boundary regions, nodes from different static clusters that detect the target can temporarily share information, and the tracking task can be handed over smoothly from one static cluster to another. As the target moves, static clusters and on-demand dynamic clusters alternately manage the target tracking task. Simulation results show that the proposed protocol performs better in tracking the moving target when compared with other typical target tracking protocols. [ABSTRACT FROM AUTHOR]

Traditional routing protocols are quite vulnerable under the attacks from both external and internal attackers. In this work, we examine the impact of a wide variety of attacks in malicious wireless sensor networks scenario. An Efficient and Secure Geographic Routing protocol ESGR is proposed to exploit the geographic location, cryptography mechanisms, and broadcast nature of the wireless channel. ESGR utilizes the geographic leashes and the TESLA scheme to provide resistance against the Sybil attack and wormhole attack. Meanwhile, it employs a distributed trust model and the packets opportunistic forwarding to prevent black hole and gray hole attacks. We demonstrate the results through analysis and simulations that ESGR effectively mitigates a specific variety of attacks and ensures high packet delivery rate in malicious sensor network environment. [ABSTRACT FROM AUTHOR]

Energy efficiency is one of the most important issues for WSNs, because the battery of each wireless sensor node cannot be recharged or replaced. Therefore, all batteries have to be well managed, in order to provide a long network lifetime, as well as to reduce energy consumption for WSNs, particularly in clustering and routing. In this paper, we propose an energy-efficient self-organized clustering model with splitting and merging (EECSM), which performs clustering and then splits and merges clusters for energy-efficient cluster-based routing. EECSM uses information of the energy state of sensor nodes, in order to reduce energy consumption and maintain load balance. We show the validity of splitting and merging of clusters and then compare the performance of the proposed EECSM with that of a well-known cluster-based self-organization routing protocol for WSNs. The results of our experiment show good performance of EECSM, in terms of network lifetime, residual energies, scalability, and robustness. [ABSTRACT FROM AUTHOR]

The areas of three-dimensional (3D) underwater wireless sensor networks (UWSNs) have attracted significant attention recently due to their applications in detecting and observing phenomena that cannot be adequately observed by means of two-dimensional UWSNs. However, designing routing protocols for UWSNs is a challenging task because path breakage occurs frequently due to uncertain node and link failures. In this paper, we present a Robust Routing Protocol (RRP) that aims to achieve robustness under harsh underwater conditions of 3D UWSNs. In RRP, each sensor has a data structure called backup bin, which allows to construct main backup links and auxiliary backup links for repairing failed links and ensuring normal data delivery. Moreover, sensor nodes can also enlarge their transmission range to build new links when the main routing path is not reachable through backup links. Simulation results show that the proposed protocol can reduce node and link failures' impact on metrics of packet delivery ratio, network throughput, energy consumption, and average end-to-end delay. [ABSTRACT FROM AUTHOR]

Neighbor discovery is one of the first steps to establish communication links between sensor nodes; thus it becomes a fundamental building block for wireless sensor networks (WSNs). Traditional neighbor discovery protocols mainly focus on static wireless networks or networks where all nodes operate on the same frequency. However, the proliferation of mobile devices and multichannel communications post new challenges to neighbor discovery problem. In this paper, we present a neighbor discovery protocol named EasiND for asynchronous duty-cycled multichannel mobile WSNs. First, we propose a neighbor discovery system based on quorum system, which can bound the discovery latency in multichannel scenarios with low power consumptions. Second, we design an optimal asynchronous neighbor discovery system for multichannel mobile WSNs based on cyclic difference set. It is optimal in the sense that it minimizes the power consumption with bounded discovery latency under desired duty cycles. Finally, we validate the performance of EasiND through both theoretical analysis and test-bed evaluations. EasiND provides a 33.3% reduction in power-latency product in theory compared to U-Connect. Meanwhile, test-bed evaluation results show that EasiND decreases average discovery latency by up to 86% compared to U-Connect and achieves at least 93.5% average fraction of discoveries in a predefined time limitation under various network conditions. [ABSTRACT FROM AUTHOR]

Energy efficiency is the main concern of research community while designing routing protocols for wireless sensor networks (WSNs). This concern can be addressed by using energy-harvesting scheme in routing protocols. In this paper, we propose a secure routing protocol that is based on cross layer design and energy-harvesting mechanism. It uses a distributed cluster-based security mechanism. In the cross-layer design, parameters are exchanged between different layers to ensure efficient use of energy. Energy-harvesting system is used to extract and store energy, which is used to take decisions for the node state and thus for the routing issues. Simulation results show that our routing protocol can perform better in many scenarios and in hostile attack-prone environment. [ABSTRACT FROM AUTHOR]

We suggest an enhanced approach for reliable bulk data transmission of image files, multimedia video files, and successive log files for monitoring systems over wireless sensor networks. Recently, some approaches have been proposed that use multiple blocks in a frame. These approaches simply drop the block that contains the error and the error-free blocks are transmitted to other nodes. This paper proposes an enhanced FEC scheme, called M-FEC, which reduces the overhead and the total number of transmissions. M-FEC fragments bulk data into many small blocks and these blocks are encoded using rateless codes. Only the erroneous blocks that are detected in a frame are dropped and a relay node waits for other incoming blocks in order to construct a full-sized frame. This simple approach can improve the performance of the FEC scheme over WSNs. Our experiments show that M-FEC reduces the number of received frames at the sink node by almost half compared to the previous approach. We compared our results for different degrees of Wi-Fi interference by choosing particular IEEE 802.15.4 channels and running our experiments for three different types of Wi-Fi interference. [ABSTRACT FROM AUTHOR]

Multichannel communication protocols have been developed to alleviate the effects of interference and consequently improve the network performance in wireless sensor networks requiring high bandwidth. In this paper, we propose a contention-free multichannel protocol to maximize network throughput while ensuring energy-efficient operation. Arguing that routing decisions influence to a large extent the network throughput, we formulate route selection and transmission scheduling as a joint problem and propose a Reinforcement Learning based scheduling algorithm to solve it in a distributed manner. The results of extensive simulation experiments show that the proposed solution not only provides a collision-free transmission schedule but also minimizes energy waste, which makes it appropriate for energy-constrained wireless sensor networks. [ABSTRACT FROM AUTHOR]

In order to achieve the equal usage of limited resources in the wireless sensor networks (WSNs), we must aggregate the sensor data before passing it to the base station. In WSNs, the aggregator nodes perform a data aggregation process. Careful selection of the aggregator nodes in the data aggregation process results in reducing large amounts of communication traffic in the WSNs. However, network conditions change frequently due to sharing of resources, computation load, and congestion on network nodes and links, which makes the selection of the aggregator nodes difficult. In this paper, we study an aggregator node selection method in the WSNs. We formulate the selection process as a top-k query problem, where we efficiently solve the problem by using a modified Sort-Filter-Skyline (SFS) algorithm. The main idea of our approach is to immediately perform a skyline query on the sensor nodes in the WSNs, which enables to extract a set of sensor nodes that are potential candidates to become an aggregator node. The experiments show that our method is several times faster compared to the existing approaches. [ABSTRACT FROM AUTHOR]

Traditionally, Wireless Sensor Networks (WSNs) are used for monitoring an extensive area. In these networks, a centralized server is usually used to collect and store the sensor information. However, new distributed protocols allow connections directly to the WSN nodes without the need of a centralized server. Moreover, these systems are able to establish communications among heterogeneous networks. The new protocols strategy is focused on considering several WSNs as a unique distributed one. This way, a user of the system is able to analyze a process under study as a whole instead of considering it as a set of different subsystems. This is the case in the evaluation of migratory waterbirds' environment. In this case, it is usual to deploy several WSNs in different breeding areas. They are all interconnected and they measure different environmental parameters. However, this improvement in the data access flexibility may result in a loss of network performance and an increase in network power consumption. Focused on this problem, this paper evaluates different communication protocols: distributed and centralized, in order to determine the best trade-off for environmental monitoring in different migratory areas of waterbirds. [ABSTRACT FROM AUTHOR]

Wireless sensor nodes with single chips may have insufficient resources for certain applications. We propose a resource management protocol for applications with constrained resources to improve effectiveness by borrowing resources from a resource management server. [ABSTRACT FROM AUTHOR]

In order to solve contradictions between real-time applications of wireless sensor networks and limited energy of nodes, Cross-Layer Power Control Algorithm (CLPCA) is proposed in this paper. Moreover, Power-Control-Based Real-Time Routing Protocol (PCBRRP) is designed capable with CLPCA. In this protocol, the transmission power of the node is adjusted dynamically to increase the energy efficiency The next hop node is selected via the link quality of the communication and the residual energy of every node. Simulation results show that the energy consumption of the network is reduced while real-time end-to-end data transmission is guaranteed. [ABSTRACT FROM AUTHOR]

Modern energy harvesting systems for WSNs involve power scavenging sources, rechargeable batteries, and supercapacitors. Typical energy-management systems calculate/predict the remaining energy stored in a node, and associated actions are dispatched involving the networking protocols. However, long-term characteristics of the mentioned hardware components are typically neglected preventing the achievement of very long maintenance-free lifetimes (e.g., >5 years) for the nodes. In this work, a systematic analysis of this problem is provided, and an open energy-management framework is proposed which promotes (a) the nontraditional combination of primary cells, supercapacitors, and harvesting systems, (b) the concept of a distributed system inside a node, and (c) the adoption of the dual duty-cycle (DDC) operation for the WSNs. The DDC's core component is a cross-layer protocol implemented as an application-layer overlay which maintains the operation of the network under very high energy efficiency Its trade-off is the reduction of the network throughput. Therefore, the DDC system has mechanisms that dynamically switch the WSN operational mode according to applications needs. Detailed guidelines are provided in order to allow the implementation of the solution on existing WSN platforms. The energy efficiency of the low duty-cycle mode of the solution is demonstrated by simulated and empirical results. [ABSTRACT FROM AUTHOR]