1Joint Localization and Data Gathering over Small World WSN with Optimal Data MULE Allocation
Localization of sensor nodes and efficient data gathering over a wireless sensor network (WSN) is vital in applications like cyber-physical systems, Internet of things and context-aware pervasive systems. In WSNs, sensor nodes transfer the data cooperatively using multiple hops over a network. The large number of hops required for data transmission leads to erroneous distance estimation between node pairs resulting in large localization error. In this paper, we utilize a recent development in social networks called small world characteristics for proposing a novel method of joint localization and data gathering over WSN. A small world WSN is developed by introducing data MULEs (mobile ubiquitous LAN extensions) into a conventional WSN. Small world WSN exhibits low average path length and high average clustering coefficient. Such a small world WSN when designed with novel routing strategies leads to reduced hop counts in sensor data transmission. Additionally, a method for optimal data MULE allocation is also developed. This method minimizes an objective function which is a normalized weighted sum of network parameters like bandwidth requirement and localization error. The optimal data MULE allocation method computes both the optimal number of data MULEs and their placement in the network. On the other hand the joint localization and data gathering method which utilizes a multidimensional scaling based cooperative localization method is also developed for this purpose.
2ROOMMATEs: An Unsupervised Indoor Peer Discovery Approach for LTE D2D Communications
Recently, there has been an increasing interest in offloading the 3GPP LTE data by using device-to-device (D2D) communications between devices. However, the peer discovering is challenging, especially in the indoor environment, since traditional users use a cellular signal to find peers, leading to incurring interference to other cellular users. In this paper, we propose ROOMMATEs, a novel approach for indoor peer discovery process, which is the enabler for indoor D2D communications in long term evolution (LTE) networks. It is a centralized approach utilizing, but not limited to, the ubiquitous WiFi network/femtocell network, combining with eNodeB in order to deliver the best results. ROOMMATEs is an unsupervised, yet energy efficient algorithm that can find surrounding user equipments (UEs) while minimizing interference and consuming much less energy. Based on the results, ROOMMATEs proves to be highly energy efficient, saving on average 24% per UE and improving signal-to-interference-plus-noise ratio in order of tens of decibels compared to other approaches. Moreover, ROOMMATEs provides indoor place identification for UEs with high accuracy using a small number of observations. ROOMMATEs is robust to missing and noisy data, works with various UEs’ brands/models, and requires no user interactions.
3Optimal Deployment of Energy-Harvesting Directional Sensor Networks for Target Coverage
The technology of harvesting energy from the natural environment can be used to overcome the energy limitation of wireless sensor networks. In this paper, we consider the problem of deploying energy-harvesting directional sensor networks for optimal target coverage. It involves the directional sensing coverage, communication route selection, and energy neutral operation. We formulate it as a mixed integer linear programming model, and propose three heuristics to solve it, i.e., a linear program-based heuristic (LPBH), a two-stage heuristic (TSH), and a sensing- and routing-integrated greedy heuristic (SRIGH). Their approximation upper bounds and time complexities are analyzed. Finally, we conduct extensive simulation experiments to evaluate and compare them. Simulation results show that TSH is the fastest one among them, but achieves the lowest success rate and solution quality. LPBH and SRIGH can achieve roughly equal success rate and solution quality, and LPBH is the most time-consuming.
4A Quality-oriented Data Collection Scheme in Vehicular Sensor Networks
Considerable research attention has been dedicated to Vehicular Sensor Networks (VSNs) because of its great potential in traffic monitoring. By taking advantage of sensors embedded in vehicles, a VSN harvests data while vehicles are traveling along the roads and then updates the collected data to the infrastructure to support Intelligent Transportation System (ITS) applications. To meet the data collection requirements of different ITS applications, a huge number of update packets are generated, which may exhaust the available wireless communication bandwidth. To improve the efficiency of utilization of wireless communication bandwidth, in this study, we propose a Quality-oriented Data Collection (QDC) scheme which aims to effectively support both the accuracy and real-time requirements stipulated by ITS applications, while reducing communication overhead. We formulate a Minimized Communication Overhead (MCO) problem and propose two algorithms, Mixed Integer Linear Programming (MILP) and Deviation-Detection (DD), to solve the MCO problem. MILP can obtain the optimal solution to the MCO problem by having all the data collected by every vehicle while DD could achieve an efficient solution without this impractical assumption. We conducted extensive experiments by using SUMO to simulate vehicle traces in freeway and downtown environments. The experimental results have demonstrated the effectiveness of the proposed solutions.
5Resource Allocation Robust to Traffic and Channel Variations in Multihop Wireless Networks
In a multihop wireless network, the traffic at each node and the channel over each link may fluctuate with time. Thus, traditional optimal resource allocation needs to be computed for each moment with instantaneous information of channel states over all links and the traffic rates at all nodes, leading to huge communication overhead and computation cost. To solve this challenge, in this correspondence, we propose to use robust resource allocation, in which the only needed information is the mean and variance of the wireless channels and the traffic rates. In the formulated problem, there are probabilistic constraints, which are difficult to handle. Effective methods are provided that can transform the probabilistic constraints to convex constraints. As the resource allocation does not need instantaneous channel state information or instantaneous traffic rate information, it is robust to channel and traffic variations, with very little communication and computation overhead.
6TMED: A Spider Web-Like Transmission Mechanism for Emergency Data in Vehicular Ad Hoc Networks
The Vehicular Ad Hoc Network (VANET) is an emerging mobile Ad Hoc network, which is an important component of the Internet of Things (IoT) and has been widely applied in intelligent transportation systems in recent years. For large scale VANETs, it is important to design efficient transmission schemes for time critical emergency data. Greedy Perimeter Stateless Routing Protocol is a typical geographic-based routing protocol and Greedy Perimeter Coordinator Routing Protocol is typical for map-based but they don't consider the QoS of the transmission link and hence are not suitable for emergency data transmissions. Some bio-inspired protocols and situation-aware protocols are more suitable for emergency situations. However, they have some limitations in terms of the computational complexity and convergence rate which can cause large time delays. In this paper, we propose a novel Spider Web-Like Transmission Mechanism for Emergency Data (TMED) in vehicular ad hoc net- works, in which a spider web-like transmission model combining GIS and electronic maps is established. In this mechanism, the request-spiders and confirmed-spiders are sent out to obtain the transmission path from a source vehicle to a destination vehicle to improve the packet delivery ratio and average transmission delay of emergency data. TMED combines a dynamic multi-priority message queue management method with a restricted greedy forwarding strategy based on position prediction to significantly reduce the end-to-end delay of packets.
7ASGR: An Artificial Spider-Web-Based Geographic Routing in Heterogeneous Vehicular Networks
Recently, vehicular ad hoc networks (VANETs) have been attracting significant attention for their potential for guaranteeing road safety and improving traffic comfort. Due to high mobility and frequent link disconnections, it becomes quite challenging to establish a reliable route for delivering packets in VANETs. To deal with these challenges, an artificial spider geographic routing in urban VAENTs (ASGR) is proposed in this paper. First, from the point of bionic view, we construct the spider web based on the network topology to initially select the feasible paths to the destination using artificial spiders. Next, the connection-quality model and transmission-latency model are established to generate the routing selection metric to choose the best route from all the feasible paths. At last, a selective forwarding scheme is presented to effectively forward the packets in the selected route, by taking into account the nodal movement and signal propagation characteristics. Finally, we implement our protocol on NS2 with different complexity maps and simulation parameters. Numerical results demonstrate that, compared with the existing schemes, when the packets generate speed, the number of vehicles and number of connections are varying, our proposed ASGR still performs best in terms of packet delivery ratio and average transmission delay with an up to 15% and 94% improvement, respectively.
8Evaluation Models for the Nearest Closer Routing Protocol in Wireless Sensor Networks
Wireless sensor networks have been pushed to the forefront in the past decade, owing to the advert of the Internet of Things. Our research suggests that the Reliability and Lifetime performance of a typical application in wireless sensor networks depend crucially on a set of parameters. In this paper, we implemented our experiments on the Nearest Closer protocol with the J-Sim simulation tool. We then analyze the closure relationships among the Density, Reliability and Lifetime, and reveal the trade-off among them based on our analysis on the experiment results. Next, we propose five intelligent evaluation models that are applicable to such situations. Our research allows the wireless sensor network users to predict the significant evaluation parameters directly from the settings while costly simulations are no longer necessary.
9Index Modulation for Cluster-based Wireless Sensor Networks
Index Modulation is applied to cluster-based wireless sensor networks (WSNs) in this study. The aim is to design an efficient decision gathering scheme for target-detection cluster-based WSNs. The proposed scheme implies that only a single node reports all the local decisions from cluster-members toward the central entity. Unlike conventional clustering, the reporting node is not fixed as it varies based on the obtained local decisions. Consequently, the local decisions of all cluster members are divided into two groups. The first one is modulated and the other one determines the index of the reporting node. The decision error rate of the proposed scheme is analyzed and an upper bound is derived. The derived bound is shown to precisely matches simulation results at pragmatic signal to noise ratio values. Furthermore, the detection threshold for the global decision is optimized for minimizing the decision error rate, and formulated in a closed-form expression.
10Fault-Tolerant Clustering Topology Evolution Mechanism of Wireless Sensor Networks
Wireless sensor networks (WSNs) are often subject to failures caused by energy depletion, software or hardware fault of nodes, environmental events, hostile attacks, and other reasons. It is critical to ensure a WSN application system is available during some presence of fault or interruption. Recent work in topology control has shown that a reasonable topology can improve the robustness of WSN. However, due to the limited resource of sensor nodes, topology control cannot easily tradeoff between fault tolerance and energy saving. To address this issue, we present a regular hexagonal-based clustering scheme (RHCS) and a scale-free topology evolution mechanism (SFTEM) for WSNs, which increases network survivability as well as maintains energy balance. RHCS uses a regular hexagonal structure for clustering sensor nodes, which satisfies at least 1-coverage fault-tolerance. SFTEM combines the reliability of RHCS with scale-free properties to connect clusters to form a robust WSN, which exploits the synergy between reliable clustering scheme and topology evolution, and can tolerate comprehensive faults including random failure and energy failure. In addition, to evaluate the performance of SFTEM, the simulation experiments were carried out to compare three factors including fault-tolerance, intrusion-tolerance, and energy balance with other methods in literature. The simulation results show that, the performance of SFTEM is superior to those of the referenced topology evolution mechanisms of WSNs.
11Co-EEORS: Cooperative Energy Efficient Optimal Relay Selection Protocol for Underwater Wireless Sensor Networks
Cooperative routing mitigates the adverse channel effects in the harsh underwater environment and ensures reliable delivery of packets from the bottom to the surface of water. Cooperative routing is analogous to sparse recovery in that faded copies of data packets are processed by the destination node to extract the desired information. However, it usually requires information about the two or three position coordinates of the nodes. It also requires the synchronization of the source, relay, and destination nodes. These features make the cooperative routing a challenging task as sensor nodes move with water currents. Moreover, the data packets are simply discarded if the acceptable threshold is not met at the destination. This threatens the reliable delivery of data to the final destination. To cope with these challenges, this paper proposes a cooperative energy-efficient optimal relay selection protocol for underwater wireless sensor networks. Unlike the existing routing protocols involving cooperation, the proposed scheme combines location and depth of the sensor nodes to select the destination nodes. Combination of these two parameters does not involve knowing the position coordinates of the nodes and results in selection of the destination nodes closest to the water surface. As a result, data packets are less affected by the channel properties. In addition, a source node chooses a relay node and a destination node.
12Genetic Fuzzy Tree Based Node Moving Strategy of Target Tracking in Multimodal Wireless Sensor Network
Multimodal wireless sensor networks (WSNs) consist of variable types of sensor nodes can do many important applications, such as environment monitoring, health care, and target tracking. In this paper, we utilize the multimodal WSN to keep track of targets in 3-D space. All the nodes in the network are different. They can be pyroelectric infrared nodes, radio frequency nodes, nodes with cameras, and so on. Based on this, we assume each of them varies in battery, mobility, and target recognition performance. To achieve a better performance of target tracking in the multimodal WSN, we propose a node moving strategy. Genetic fuzzy tree is employed in this paper. It is a two-layer fuzzy tree system (FTS) optimized by the genetic algorithm. The first layer gives a score to each node and selects the moving nodes. The second layer then controls the moving distances. The Pittsburgh genetic algorithm is used to optimize the whole rule base and data base of the FTS. Simulation results prove that the tracking error can be reduced applying our approach.
13Design of a Wireless Sensor Network-Based IoT Platform for Wide Area and Heterogeneous Applications
Internet of Things (IoT) is not only a promising research topic but also a blooming industrial trend. Although the basic idea is to bring things or objects into the Internet, there are various approaches, because an IoT system is highly application oriented. This paper presents a wireless sensor network(WSN)-based IoT platform for wide area and heterogeneous sensing applications. The platform, consisting of one or multiple WSNs, gateways, a Web server, and a database, provides a reliable connection between sensors at fields and the database on the Internet. The WSN is built based on the IEEE 802.15.4e time slotted channel hopping protocol, because it has the benefits such as multi-hop transmission, collision-free transmission, and high energy efficiency. In addition to the design of a customized hardware for range extension, a new synchronization scheme and a burst transmission feature are also presented to boost the network capacity and reduce the energy waste. As a result, the proposed platform can fulfill the high throughput requirement for high-rate applications and the requirement of long battery life for low-rate applications at the same time. We have developed a testbed in our campus to validate the proposed system.
14Polar Coordinate-Based Energy-Efficient-Chain Routing in Wireless Sensor Networks Using Random Projection
Random projection based on compressed sensing can reduce the amount of data transmitted in a wireless sensor network (WSN), and efficient routing can reduce the network traffic. Thus, this paper presents a Random projection-Polar coordinate-Chain routing (RPC) method. The method uses polar coordinates to locate nodes, establishes a chain structure to form a route, and applies random projection to achieve the compressed data collection. In a WSN, the sink is the center of the data collection. With the sink as the pole, the polar coordinates can be used to determine the orientation of each node relative to the sink so that nodes can be searched under certain conditions. By adopting the chain topological structure, the establishment of the chain through the greedy algorithm reduces the energy consumption and complexity. Based on the comparative analysis, a four-quadrant chain routing method combining the polar radius and polar angle is proposed for smaller networks. For large-scale networks, a routing algorithm combining the sector and inner circle is proposed. Then, according to the random projection theory, the weighted sum of the random projections of each row of the corresponding measurement matrix in each partition is transmitted to the sink. The sink has collected all measurements of each partition to complete the signal reconstruction. In this method, the route is formed by searching in the zones according to the polar radius and the polar angle, which avoids the roundabout route between distant nodes and reduces the energy consumption of the network.
15Compressive Data Gathering Based on Even Clustering for Wireless Sensor Networks
Compressive data gathering (CDG) based on compressed sensing (CS) theory for wireless sensor networks (WSNs) greatly reduces the amount of data transmitted compared with the traditional acquisition method that each node forwards the collected data directly to the next node. CDG combined with sparse random projection can further reduce the amount of data and thus prolong the lifetime of the WSN. The method of randomly selecting projection nodes as cluster heads to collect the weighted sum of sensor nodes outperforms the non-CS (without using CS) and hybrid-CS (applying CS only to relay nodes that are overloaded) schemes in decreasing the communication cost and distributing the energy consumption loads. However, the random selection of projection nodes causes the overall energy consumption of the network to be unstable and unbalanced. In this paper, we propose two compressive data gathering methods of balanced projection nodes. For WSN with uniform distribution of nodes, an even clustering method based on spatial locations is proposed to distribute the projection nodes evenly and balance the network energy consumption. For WSN with unevenly distributed nodes, an even clustering method based on node density is proposed, taking into account the location and density of nodes together, balancing the network energy and prolonging the network lifetime. The simulation results show that compared with the random projection node method and the random walk method, our proposed methods have better network connectivity and more significantly increased overall network lifetime.
16Hybrid MAC Protocol Design for Mobile Wireless Sensors Networks
With the rapid proliferation of mobile wireless sensors networks (WSNs), which are widely deployed in the Internet of things, the Internet of vehicles, and flying ad hoc networks, more and more researchers are making the effort to improve energy efficiency and throughput of WSNs. In recent years, many protocols have been proposed to solve the energy shortage problem. Some of the protocols are based on cooperative or allocation schemes, some are based on contending schemes, and others are based on the foundation of hybrid schemes. However, it is still difficult to improve the energy efficiency and networks throughput simultaneously. In this article, we present a novel carrier sense multiple access/collision avoidance and time division multiple access hybrid scheme protocol medium access control (MAC) on the MAC layer to improve the throughput and reduce energy consumption at the same time for mobile WSN with position prediction algorithms in 3-D space. Compared to existing protocols, the proposed protocol can efficiently reduce the energy consumption and significantly improve the throughput, especially for high-speed mobile WSN in the many-to-one communication paradigm. Extensive simulation results prove the performance of the protocol.
17Joint Resource Allocation for Wireless Energy Harvesting Enabled Cognitive Sensor Networks
In this paper, we consider a cognitive relaying network, where the cognitive sensor transmitter (CST) is capable of harvesting energy from the radio frequency signals with a power splitting scheme. Specifically, the primary transmitter (PT) broadcasts its signal to primary receiver (PR) and CST in the first transmission slot. After receiving PT's signal, CST splits the received signal into two parts, one for information decoding and the other for energy harvesting. In the second transmission slot, CST allocates a part of the accessed bandwidth to forward PT's signal to PR with amplify-and-forward or decode-andforward relaying protocols by using the harvested energy in the first transmission slot. As a reward, CST can utilize the remained bandwidth to transmit its own signal to the cognitive sensor receiver. The main object is to maximize cognitive network transmission rate by jointly optimizing the power splitting ratio and bandwidth subject to the primary transmission rate constraint. Simulation results are presented to illustrate the performance improvement of both primary and cognitive systems.
18Analysis of Internet Protocol Based Multicast on Duty-Cycled Wireless Sensor Networks
Many Internet protocol -based multicast protocols for Wireless Sensor Networks (WSNs) rely on the routing tree obtained through the Routing Protocol for Low power and lossy networks, to reach subscribers of a multicast group. WSNs often activate radio duty cycling (RDC) to save energy. Our purpose is to examine the effect of the link layer (LL) transmission mode, on the performance of those multicast protocols in function of RDC and multicast protocol parameters. First, the average packet delay in function of the LL transmission mode and the radio channel check rate (CCR), is investigated for restricted topologies through mathematical modeling and simulation. Both show that LL broadcast produces equal or less delay for reaching its interested children in the first hop compared with LL unicast. However, LL broadcast suffers from higher delays, inversely proportional to the CCR, for subsequent hops. LL unicast's delay per hop increases linearly with the number of interested children. Second, the simulation model is used to study the effect of using a mix of LL unicast and broadcast for different CCRs in randomly generated topologies. Average delay, energy consumption and packet delivery ratio are determined in function of hop distance. The average delay can be optimized by using a mixed mode, in which a threshold determines from how many interested children onwards a LL broadcast should be used. The results indicate which optimal threshold, in function of the CCR, should be chosen to optimize delay and energy consumption.
19FuMAM: Fuzzy-Based Mobile Agent Migration Approach for Data Gathering in Wireless Sensor Networks
A mobile agent (MA) was recently proposed to provide an alternative solution for traditional data gathering in wireless sensor networks. An MA is a software component that can migrate among network nodes by following an assigned itinerary (or path). Instead of transporting data from the nodes to the processing unit (e.g., sink) for data gathering, the MA visits each node, and thus, it performs data gathering locally. The MA has two types of itinerary planning: single-agent itinerary planning (SIP) and multi-agent itinerary planning (MIP). The MIP was introduced to address the drawbacks of the SIP in terms of task duration, energy consumption, and reliability. Despite the advantages of the MIP, determining the optimal itinerary for each MA in the MIP poses a considerable challenge. Most proposed itineraries adopt a static itinerary in which the nodes to be visited by the MA are predetermined at the sink node. The distance among nodes is the only parameter that has been used to determine the itinerary of the MA. Other parameters, such as the remaining energy and a number of neighbors, have not been considered. This omission can negatively impact MA migration and result in an unsuccessful MA round-trip, particularly when the remaining energy of the node is insufficient to transfer an MA to the next hop.
20QTSAC: An Energy-Efficient MAC Protocol for Delay Minimization in Wireless Sensor Networks
Millions of sensors are deployed to monitor the smart grid. They consume huge amounts of energy in the communication infrastructure. Therefore, the establishment of an energy-efficient medium access control (MAC) protocol for sensor nodes is challenging and urgently needed. The Quorum-based MAC protocol independently and adaptively schedules nodes' wake-up times and decreases idle listening and collisions, thereby increasing the network throughput and extending the network lifetime. A novel Quorum time slot adaptive condensing (QTSAC)-based MAC protocol is proposed for achieving delay minimization and energy efficiency for the wireless sensor networks (WSNs). Compared to previous protocols, the QTSAC-based MAC protocol has two main novelties: 1) It selects more Quorum time slots (QTSs) than previous protocols in the area that is far from the sink according to the energy consumption in WSNs to decrease the network latency and 2) It allocates QTSs only when data are transmitted to further decrease the network latency. Theoretical analyses and experimental results indicate that the QTSAS protocol can greatly improve network performance compared with existing Quorum-based MAC protocols. For intermediate-scale wireless sensor networks, the method that is proposed in this paper can enhance the energy efficiency by 24.64%-82.75%, prolong the network lifetime by 58%-27.31%, and lower the network latency by 3.59%-29.23%.
21A Slotted Sense Multiple Access Protocol for Timely and Reliable Data Transmission in Dynamic Wireless Sensor Networks
A wireless medium access control protocol that uses a topology-dependent slot schedule is vulnerable to link failures. This becomes severer in industrial fields due to node mobility and various obstructions unfriendly to wireless communication. The proposed protocol allocates a big sharable slot (SS) to each tree level, producing a topology-independent schedule that makes the protocol highly responsive to the changes of topology. Then, the nodes at the same level use carrier sense multiple access (CSMA)/CA for data transmission and channel hopping to cope with the varying condition of a channel. The use of CSMA/CA and channel hoping makes data transmission reliable against internal and external interferences. Another feature is that every node gets its SS using a slot generation function independently of other nodes. Simulations and experiments verify that the proposed protocol achieves good performance in terms of packet delivery ratio and energy efficiency against the variation of multipath fading, various external sources of interference, and node mobility.
22Performance Comparison of Multi-Agent Middleware Platforms for Wireless Sensor Networks
Despite the numerous possible applications of wireless sensor networks (WSNs), there is a key disadvantage related to the high complexity in programming WSNs, which is a result of their distributed and built-in features. To overcome this shortcoming, software agents have been identified as a suitable programming paradigm. The agent-based approach commonly uses a middleware for the execution of the software agents. In this regard, the present paper aims at comparing Java-based agent middleware platforms in their performance for the WSN application domain. Experiments were performed to analyze two versions of tracking applications, based on different agent models implemented for a given set of middleware platforms that support programming at a high-level of abstraction. The results highlight the differences in the resource consumption (CPU, memory, and energy) and in the communication overhead, providing an indication of suitability for each type of analyzed middleware, considering specific concerns while developing WSN applications.
23Collaborative Link-Aware Protocols for Energy-Efficient and QoS Wireless Body Area Networks Using Integrated Sensors
Integrated sensor systems are the promising solutions to the multiprobe design of biomedical sensors for energy efficient wireless body area networks (WBANs). To improve energy efficiency and communication quality-ofservice (QoS) of integrated sensor hubs, a cross-layered energyaware resource allocation (CLEAR) is proposed to exploit the characteristics of medium access control (MAC) and physical (PHY) layers of WBANs. The proposed MAC protocol applies a twin-token bucket model and real-time scheduling to the active superframe interleaving and beacon shifting techniques defined in the IEEE 802.15.6 standard. In addition, the proposed period transformation controlling task end-to-end delay improves the QoS while reducing packet collisions. The proposed PHY protocol is a hybrid of the transmit power control (TPC) and link adaption (LA) strategies, which coordinates the receiver and transmitter with link parameters including data rate, bit error ratio, receiver sensitivity, transmission power, modulation, etc. It adapts the link quality due to human postures or movements to meet the required QoS while minimizing the energy consumption of the transceiver front-end. Experimental results show that CLEAR outperforms existing methods in terms of packet delivery ratio, delay, bandwidth utilization, and energy consumption.
24EAPC: Energy-Aware Path Construction for Data Collection Using Mobile Sink in Wireless Sensor Networks
Data collection is one of the paramount concerns in wireless sensor networks. Many data collection algorithms have been proposed for collecting data in particular monitoring regions. However, the efficiency of the paths for such data collection can be improved. This paper proposes an energy-aware path construction (EAPC) algorithm, which selects an appropriate set of data collection points, constructs a data collection path, and collects data from the points burdened with data. EAPC is intended to prolong the network lifetime, it accounts for the path cost from its current data collection point to the next point and the forwarding load of each sensor node. Performance evaluation reveals that the proposed EAPC has more efficient performance than existing data collection mechanisms in terms of network lifetime, energy consumption, fairness index, and efficiency index.
25Secure Knowledge and Cluster-Based Intrusion Detection Mechanism for Smart Wireless Sensor Networks
Wireless sensor networks, due to their nature, are more prone to security threats than other networks. Developments in WSNs have led to the introduction of many protocols specially developed for security purposes. Most of these protocols are not efficient in terms of putting an excessive computational and energy consumption burden on small nodes in WSNs. This paper proposes a knowledge-based context-aware approach for handling the intrusions generated by malicious nodes. The system operates on a knowledge base, located at the base station, which is used to store the events generated by the nodes inside the network. The events are categorized and the cluster heads (CHs) are acknowledged to block maliciously repeated activities generated. The CHs can also get informational records about the maliciousness of intruder nodes by using their inference engines. The mechanism of events logging and analysis by the base station greatly affects the performance of nodes in the network by reducing the extra security-related load on them.
26Energy-Efficient Sensor Data Collection Approach for Industrial Process Monitoring
The use of wireless sensor network for industrial applications has attracted much attention from both academic and industrial sectors. It enables a continuous monitoring, controlling, and analyzing of the industrial processes, and contributes significantly to finding the best performance of operations. Sensors are typically deployed to gather data from the industrial environment and to transmit it periodically to the end user. Since the sensors are resource constrained, effective energy management should include new data collection techniques for an efficient utilization of the sensors. In this paper, we propose adaptive data collection mechanisms that allow each sensor node to adjust its sampling rate to the variation of its environment, while at the same time optimizing its energy consumption. We provide and compare three different data collection techniques. The first one uses the analysis of data variances via statistical tests to adapt the sampling rate, whereas the second one is based on the set-similarity functions, and the third one on the distance functions. Both simulation and real experimentations on telosB motes were performed in order to evaluate the performance of our techniques. The obtained results proved that our proposed adaptive data collection methods can reduce the number of acquired samples up to 80% with respect to a traditional fixed-rate technique. Furthermore, our experimental results showed significant energy savings and high accurate data collection compared to existing approaches.
27Distributed Deployment Algorithm for Barrier Coverage in Mobile Sensor Networks
The deployment of sensor nodes (SNs) to form a network with coverage ability is one of the most important challenges of wireless sensor networks. In this paper, we study an efficient distributed deployment algorithm for barrier coverage improvement with mobile sensors, in which the SNs can be relocated after the initial deployment. To achieve the maximum number of barriers, we propose a distributed algorithm to construct k-barrier coverage by relocation of the SNs. Different from existing approaches, we propose a novel clustering technique based on the network area to reduce the information exchange messages. Then, based on the SNs clusters, we propose a heuristic method to assign the SNs evenly into each cluster with regard to the required number of SNs of each cluster and decide the moving SNs by computing the optimal relocation, considering moving distance minimization. The main goal of this approach is to relocate the SNs to form the maximum number of barriers with a minimum relocation cost, in terms of sensor energy consumption of communication and movement. The simulation results demonstrate the effectiveness of our algorithm when compared with other competing approaches.
28Delay-Efficient Energy-Minimized Data Collection with Dynamic Traffic in WSNs
Data collection is one of the most important applications in wireless sensor networks where sensed data are gathered from sensor nodes to the base station. Reporting redundant data leads to the wastage of time and energy, the sensors therefore report only meaningful information to the base station, which are independent and distinct with the lasted ones. This assumption leads to unpredictable changes of data traffic over different sampling intervals in data collection process. In this paper, we first formulate the tight constraints of the problem and then propose a delay-efficient traffic adaptive (DETA) scheme for collecting data from sensor nodes with minimum energy consumption. The DETA scheme minimizes data collection delay by constructing delay-efficient, collision-free schedule, and by using a special mechanism to enable every node to self-adapt with the changes of data traffic. We also conducted simulations to evaluate the performance of the proposed scheme, and the results shown that the proposed scheme significantly decreases data collection delay and energy consumption compared with the existing schemes.
29Energy Efficient Consecutive Packet Transmissions in Receiver-Initiated Wake-Up Radio Enabled WSNs
In wake-up radio (WuR)-enabled wireless sensor networks, data communication among nodes is triggered in an on-demand manner, by either a sender or a receiver. For receiver-initiated WuR (RI-WuR), a receiving node wakes up sending nodes through a wake-up call. Correspondingly sending nodes transmit packets in a traditional way by competing with one another multiple times in a single operational cycle. In this paper, we propose a receiver-initiated consecutive packet transmission WuR (RI-CPT-WuR) medium access control (MAC) protocol, which eliminates multiple competitions to achieve higher energy efficiency. Furthermore, we develop two associated discrete time Markov chains (DTMCs) for evaluating the performance of RI-CPT-WuR and an existing RI-WuR MAC protocol. Using the solutions from the DTMC models, closed-form expressions for network throughput, average delay, packet reliability ratio, energy consumption and lifetime, and energy efficiency for both protocols are obtained. Numerical results demonstrate the superiority of the RI-CPT-WuR protocol.
30Mobility Load Balancing Method for Self-Organizing Wireless Networks Inspired by Synchronization and Matching With Preferences
Mobility load balancing (MLB) aims to resolve the mismatch between the distribution of network resources and the traffic demands. In this paper, we identify two key policies that characterize jointly an MLB method and propose algorithms for them to stabilize a network and increase the resource efficiency of a network. We adopt the synchronization model observed in nature to devise the first policy called a load assignment policy that determines the amount of loads tradable among cells. We design the second policy called a target selection policy by using the matching theory with preferences to determine the optimal pairs of user equipment (UE) and their new serving cells when the UE in an overloaded cell need to be handed over to its neighboring cells. Through mathematical analysis, we show the stability and the optimality of the proposed MLB method. We also show through simulation studies that the proposed method can distribute loads among cells more evenly than the conventional methods, which increases the total network throughput and the quality of service provided to UE.
31Adaptive Full-Duplex Communications in Cognitive Radio Networks
In this paper we propose a novel adaptive scheme for full duplex communication of secondary users (SU) in a cognitive radio network. The secondary network operates adaptively in three modes; Cooperative Sensing (CS), Full Duplex Transmit and Sensing (FDTS), and in-band bidirectional Full Duplex Transmit and Receive (FDTR). In the CS mode, the secondary nodes will detect the signal of a primary user (PU) through a novel cooperative MAC protocol and will decide the system's mode of operation in the subsequent spectrum hole. This adaptive decision is based on dual-threshold detection (DTD) introduced for the first time. When the primary's signal at SU's receivers is weak, the system switches to the FDTS mode to avoid higher collisions probability and long or endless collision durations. In the FDTS mode, one of SUs senses the PU activity continuously whilst transmitting to another node. When the channel conditions allow, the system switches to the FDTR mode, in which the secondary users would communicate bidirectionally in an asynchronous full duplex manner. The novel idea of asynchronous transmission in this mode will result in decreased maximum and average collision durations. Analytical closed forms for probability of collision, average collision duration and cumulative collision duration, as well as throughput of the SU network are derived, and performance of the proposed scheme in terms of the above-mentioned metrics, its effectiveness, and advantages over conventional methods of sensing and transmission are verified via simulations.
32Data Integrity Attacks against Dynamic Route Guidance in Transportation-based Cyber-Physical Systems: Modeling, Analysis, and Defense
Real-time route guidance schemes, as one of the critical services in Transportation-based Cyber-Physical Systems (TCPS), have been introduced to assist travelers in determining optimal routing with low traffic congestion and travel time. To secure the route guidance process, which enables traffic efficiency and safety, in this paper we first investigate security issues of route guidance schemes via modeling and analysis of data integrity attacks on the route guidance process, and then develop corresponding mitigation mechanisms to combat the investigated attack. Via the manipulation of traffic state data measured or generated by compromised vehicles, the data integrity attack can give rise to erroneous predictions of traffic states and induce improper determination of guided routes for vehicles, increasing traffic congestion, and reducing traffic efficiency and safety. We formally model the attack and analyze its impacts on the effectiveness of route guidance schemes. Our results show that the data integrity attack can effectively disrupt route guidance schemes, leading to significant traffic congestion, increased traveling time, and imbalanced use of transportation resources. To mitigate the data integrity attack, we investigate the forged data filtering scheme, in which the forged traffic state data can be filtered out during data delivery in vehicular networks.
33Bid Privacy Preservation in Matching Based Multi-Radio Multi-Channel Spectrum Trading
Spectrum trading with secondary users (SUs) for monetary gains improves the inefficient spectrum utilization of primary users (PUs) in the cognitive radio networks (CRNs). It is an efficient way of dynamic spectrum sharing that enhances accessing opportunities of SUs and escalates revenue of PUs. In the spectrum trading market, bidding privacy is a serious concern for SUs, since untrustworthy PUs or spectrum traders may leverage bidding information to manipulate the trading or leak SU's bids to other SU competitors for illegal gains. Current centralized privacy preserving spectrum trading designs may incur extra infrastructure deployment, miss many instantaneous spectrum accessing opportunities, and have scalability issues. In this paper, we propose a privacy-preserving semi-distributed spectrum trading scheme for Multi Radio Multi Channel (MRMC) CRNs, which has joint consideration of spectrum reuse, SUs' bidding privacy preservation, and PUs' revenue maximization.We use the conflict graph to characterize SUs' interference relationships, and jointly employ the Paillier Cryptosystem and dynamic matching to conduct the spectrum trading in a semi-distributed manner. Through security, complexity and performance analysis, we show that the proposed scheme (i) effectively preserves the privacy of SUs' bidding values, and (ii) notably increases the PUs' revenue and improves spectrum utilization with limited overhead.
34Securing Cooperative Spectrum Sensing against Collusive False Feedback Attack in Cognitive Radio Networks
Cooperative spectrum sensing (CSS) is considered as a powerful approach to improve the utilization of scarce spectrum resources. However, CSS assumes all secondary users (SU) always are honest, and thus offering opportunities for attackers to launch spectrum sensing data falsification (SSDF) attack. To combat such threat, recent efforts have been made to trust mechanism. In this paper, we argue that powering CSS with trust mechanism is not enough. A vulnerability for trust mechanism is found, that is, the feedback data from initiator SUs are generally unchecked. Such feedback data corresponding to the spectrum status of primary users (PU) can be exploited by attackers to disturb trust mechanism in a collusive manner. Specially, collusive false feedback (CFF) attackers would form a clique to help with each other. One of CFF attackers can disguise as an initiator SU who sends the feedback in accordance with the sensing data of their conspirators who play the role of cooperating SUs, result in promoting their conspirators' sensing trust quickly. With high sensing trust, attackers can avoid the detection of trust mechanism, and hence launch SSDF attack (fake sensing data) more easily. We conduct an in-depth investigation on CFF attack and propose a two-level defense scheme called FeedGuard from the design ideas of feedback trust and I-C frequency correlation analysis. Simulation results show that the FeedGuard scheme can enhance the accuracy of sensing trust evaluation, and thus successfully reducing the power of CFF attack against CSS.
35Secure cooperative communication with non-dedicated relays
The security issue is considered for a cooperative communication system with multiple non-dedicated relays which have their own information to transmit. To prevent the eavesdropper from intercepting the source information and guarantee the transmission of the relays, a secure distributed spatial modulation (SDSM) scheme is proposed in this paper. In the broadcasting phase, the relays which can successfully decode the source signal form a decoding set. In the relaying phase, the source information is carried by the indices of some selected relays in the decoding set. In conventional distributed spatial modulation systems, only the selected relay is activated, and any receiver in the relays' coverage can decode the source information by examining the status of the relays. In order to prevent eavesdropping, in the proposed scheme, all the relays in the decoding set are activated simultaneously to transmit their own information. The destination can extract the source information in the spatial domain by designing a precoder for the relays' signals. The secrecy rate analysis shows that the mutual information from the source to the eavesdropper is zero. The aggregate mutual information of the cooperative communication system is also analyzed. Simulation results validate the superiority of the proposed SDSM scheme compared with the competing candidates.
36Secure ARQ Protocol for Wireless Communications: Performance Analysis and Packet Coding Design
In this paper, we consider secure transmission of a private file which comprises multiple packets. A Network-Coding assisted automatic-repeat-request (ARQ) scheme is proposed to improve the security at both file level and packet level. Specially, the ARQ protocol degrades the intercept probability of the whole file at the eavesdropper, while the Network Coding guarantees the per-packet security. The closed-form intercept probability and outage probability of the whole file and each packet are analytically presented, and we then investigate the trade-off between the security performance and the outage probability. The proposed scheme is further extended to the cooperative ARQ scenario, and simulation results are provided to corroborate our theoretical findings.
37Bus Trajectory-Based Street-Centric Routing for Message Delivery in Urban Vehicular Ad hoc Networks
This paper focuses on the routing algorithm for the communications between vehicles and places in urban VANET. As one of the basic transportation facilities in an urban setting, buses periodically run along their fixed routes and widely cover city streets. The trajectory of bus lines can be seen as a sub map of a city. Based on the characters of bus networks, we propose a bus trajectory-based street-centric routing algorithm (BTSC), which uses bus as main relay to deliver message. In BTSC, we build a routing graph based on the trajectories of bus lines by analyzing the probability of bus appearing on every street. We propose two novel concepts, i.e. the probability of street consistency (PSC) and the probability of path consistency (PPC) which is used as metrics to determine routing paths for message delivery. This aims to choose the best path with higher density of busses and lower probability of transmission direction deviating from the routing path. In order to improve the bus forwarding opportunity, we design a bus-based forwarding strategy with ant colony optimization (FACO) to find a reliable and steady multi-hop link between two relay buses in order to decrease end-to-end delay. BTSC makes the improvements in the selection of routing path and the strategy of message forwarding. Simulation results show that our proposed routing algorithm has a better performance in transmission ratio, transmission delay and adaptability to different networks.
38Resource Allocation Robust to Traffic and Channel Variations in Multihop Wireless Networks
In a multihop wireless network, the traffic at each node and the channel over each link may fluctuate with time. Thus, traditional optimal resource allocation needs to be computed for each moment with instantaneous information of channel states over all links and the traffic rates at all nodes, leading to huge communication overhead and computation cost. To solve this challenge, in this correspondence, we propose to use robust resource allocation, in which the only needed information is the mean and variance of the wireless channels and the traffic rates. In the formulated problem, there are probabilistic constraints, which are difficult to handle. Effective methods are provided that can transform the probabilistic constraints to convex constraints. As the resource allocation does not need instantaneous channel state information or instantaneous traffic rate information, it is robust to channel and traffic variations, with very little communication and computation overhead.
39A Secure and Efficient Authentication Technique for Vehicular Ad-Hoc Networks
Vehicular ad-hoc networks (VANETs) are under active development, thanks in part to recent advances in wireless communication and networking technologies. The most fundamental part in VANETs is to enable message authentications between vehicles and roadside units. Message authentication using proxy vehicles has been proposed to reduce the computational overhead of roadside units significantly. In this message authentication scheme, proxy vehicles that verify multiple messages at the same time improve roadside units’ efficiency. In this paper, first we show that the only proxy-based authentication scheme (PBAS) presented for this goal by Liu et al. cannot guarantee message authenticity, and also it is not resistant against impersonation and modification attacks and false acceptance of batched invalid signatures. Next, we propose a new identity-based message authentication scheme using proxy vehicles (ID-MAP). Then, to guarantee that it can satisfy the message authentication requirement, existential unforgeability of underlying signature against adaptively chosen-message and identity attack is proved under elliptic curve discrete logarithm problem in the random oracle model. It should be highlighted that ID-MAP not only is more efficient than PBAS since it is pairing-free and identity-based, and also it does not use map-to-point hash functions, but also it satisfies security and privacy requirements of VANETs. Furthermore, analysis shows that the required time to verify 3000 messages in ID-MAP is reduced by 76% compared to that of PBAS.
40Design and Performance Analysis of Multichannel MAC protocol for Cognitive WLAN
Dynamic spectrum access (DSA) allows the spectrum to be utilized efficiently through opportunistic access. Cognitive radio (CR) is a technology used to enable DSA. Unlike a wireless local area network (WLAN) that operates in unlicensed band, cognitive WLAN allows CRs to identify spectrum holes in licensed bands and opportunistically use it. DSA makes the design of the medium access control (MAC) layer in the cognitive WLAN challenging. In this paper, we design and carry out performance analysis of IEEE 802.11 DCF based MAC protocol for multichannel cognitive WLAN. Our main contributions are as follows: 1) A Markov chain model for CRs and 2) another Markov chain to model the joint usage of the channel by the licensed users and CRs. These coupled Markov chain models are then solved for stationary probability distribution. Using the above models, we derive throughput and delay of the CRs and study their variation against the number of CRs, the number of channels, and spectrum availability. Theoretical results are validated using simulation and compared with results from existing literature.
41Performance of Incremental Relaying Protocols for Cooperative Multi-Hop CRNs
Multi-hop relaying is used for increasing the communication range of cognitive radio networks (CRNs). To circumvent the implied loss in throughput due to multi-hop relaying, in this paper, we propose incremental relaying (IR) for cooperative multi-hop cognitive radio networks (CMHCRNs). Two IR protocols that select a relay from the qualified relays (the relays whose received signal-to-noise-ratio (SNR) values are greater than a predefined threshold) in each hop are proposed to study the performance of the considered CMHCRN. The first protocol is named as IR based highest SNR (IR-HSNR) protocol that selects a relay with best SNR to the destination. Another one, termed as IR based highest transmit power (IR-HTP) protocol, selects a relay with highest available transmit power. Expressions for the exact outage probability and throughput are derived for both routing protocols by considering both peak-power and peak-interference constraints. Moreover, closed-form expressions for floor values of outage probability and throughput are derived for both the protocols. It is shown through numerical results that throughput of the considered system shows a concave behavior with respect to number of relaying hops for both the proposed protocols. It is further observed that the performance of the IR-HSNR is superior to that of the IR-HTP, whereas the latter has lower implementation complexity.
42Swift resource allocation in wireless networks
Multiple linear constraint Water Filling problem (MLWFP) is solved innovatively in this paper, in which powers allotted to the T resources of the transmitting user maximize the capacity of the transmitting user while controlling the interference to all the surrounded users of the wireless network. MLWFP is solved previously using iterative algorithms that take more number of iterations, thus increasing the computational complexity. Unlike prior algorithms, the uniqueness of the proposed algorithm is in detecting the tight bounds for the number of non-zero powers, S. Subsequently, S is calculated from its bounds. This makes it possible for the proposed algorithm to compute S non-zero powers alone (using the closed-form solution), whereas all the prior algorithms find powers iteratively for all T (> S) resources. Thus, the worst case computational complexity of the proposed algorithm is reduced manyfold and is considerably lower than that of the prior algorithms by a factor of O(T_{2}). Simulation results justify the analysis of the proposed algorithm.
43SS-MAC: A Novel Time Slot-Sharing MAC for Safety Messages Broadcasting in VANETs
Efficient and scalable media access control (MAC) protocol design is crucial to guarantee the reliable broadcast of safety messages in vehicular ad hoc networks. To devise a MAC for safety message broadcasting with reliability and minimum delay, in this paper, we propose a novel time slot-sharing MAC, referred to as SS-MAC, which can support diverse periodical broadcasting rates. In specific, we first introduce a circular recording queue to online perceive time slot occupying status. We then design a distributed time slot sharing (DTSS) algorithm and random index first fit (RIFF) algorithm, to efficiently share the time slot and make the online vehicle-slot matching, respectively. We prove theoretically the efficacy of DTSS algorithm, and evaluate the efficiency of RIFF algorithm by using MATLAB simulations. Finally, we conduct extensive simulations considering various driving scenarios and resource conditions to demonstrate the SS-MAC performance.
44Performance Analysis of Opportunistic Cooperation Schemes in Cognitive Radio Networks
In this paper, we propose an opportunistic cooperation scheme in a two-user buffer-aided cognitive radio network. In each time slot, the secondary user (SU) will either transmit its own packets, or help the primary user to forward packets, based on a priority factor α. According to previous cooperation schemes, some time slots will be wasted if the selected buffer is empty. However, under the proposed scheme, these time slots will be handed over to the nonempty buffer's transmission, which increases the average service rates of buffers at the SU. Considering the bursty nature of sources, we characterize the evolution of buffer states by using the Markov chain. By calculating the probability of time slot handing over, the increased service rates can be theoretically analyzed, so as to the improvements on the stable throughput region and the average end-to-end transmission delay. Moreover, we further discuss the throughput and delay tradeoffs between the two users, which indicates that we can control the traffic load by adjusting the priority factor. Simulations validate our analysis, and reveal that the proposed cooperation scheme with time slot handing over offers a far larger throughput while maintaining a shorter transmission delay compared with previous schemes.
45Evaluation Models for the Nearest Closer Routing Protocol in Wireless Sensor Networks
Wireless sensor networks have been pushed to the forefront in the past decade, owing to the advert of the Internet of Things. Our research suggests that the Reliability and Lifetime performance of a typical application in wireless sensor networks depend crucially on a set of parameters. In this paper, we implemented our experiments on the Nearest Closer protocol with the J-Sim simulation tool. We then analyze the closure relationships among the Density, Reliability and Lifetime, and reveal the trade-off among them based on our analysis on the experiment results. Next, we propose five intelligent evaluation models that are applicable to such situations. Our research allows the wireless sensor network users to predict the significant evaluation parameters directly from the settings while costly simulations are no longer necessary.
46Packet Size Optimization for Lifetime Maximization in Underwater Acoustic Sensor Networks
Recently, underwater acoustic sensor networks (UASNs) have been proposed to explore underwater environments for scientific, commercial, and military purposes. However, long propagation delays, high transmission losses, packet drops, and limited bandwidth in underwater propagation environments make realization of reliable and energy-efficient communication a challenging task for UASNs. To prolong the lifetime of battery-limited UASNs, two critical factors, i.e., packet size and transmission power, play vital roles. At one hand, larger packets are vulnerable to packet errors, while smaller packets are more resilient to such errors. In general, using smaller packets to avoid bit errors might be a good option. However, when small packets are used, more frames should be transmitted due to the packet fragmentation and hence, network overhead and energy consumption increases. On the other hand, increasing transmission power reduces frame errors, but this would result in unnecessary energy consumption in the network. To this end, packet size and transmission power should be jointly considered to improve network lifetime. In this study, an optimization framework via integer linear programming (ILP) has been proposed to maximize network lifetime by joint optimization of transmission power and packet size. In addition, a realistic link-layer energy consumption model is designed by employing physical layer characteristics of UASNs. Extensive numerical analysis through the optimization model has been also performed to investigate the trade-offs caused by the transmission power and packet size quantitatively.
47Traffic and Energy Aware Routing for Heterogeneous Wireless Sensor Networks
The energy-efficiency of routing algorithm is crucial for improving the lifetime of battery constrained Wireless Sensor Networks (WSNs). The consideration of nodes heterogeneity in routing is essential for achieving optimal resource utilization. This letter considers sensor nodes with random initial energies and random disparities in data generation rate (traffic) to model a realistic clustering based WSN suited for heterogeneous sensing applications. The letter presents an energy model for the scenario and proposes a Traffic and Energy Aware Routing (TEAR) scheme to improve the stability period. The simulation results indicate that TEAR outperforms other clustering based routing algorithms under the scenario.
48Zone Probabilistic Routing for Wireless Sensor Networks
This article modeled the data routing problem in Wireless Sensor Networks as an in-zone random process. The data packets are randomly routed from the source to the sink within the defined Routing Zone via any-path. The proposed "Zone Probabilistic Routing (ZPR)" is a distributed probabilistic and randomized anycast routing protocol. In ZPR, The forwarding probability distribution is defined by multiplying the Four Probability Distributions (4PD) namely: direction, transmission distance, perpendicular distance and residual energy. In order to meet different performance requirements for different applications, these probability distributions are completely controllable via a set of exponential control-parameters (direction control, transmission distance control, perpendicular distance control and residual energy control). This set of parameters is user-oriented and can be modified prior to nodes deployment to achieve different performances. Through extensive simulations and experimental results, the optimal values for these exponential control-parameters have been obtained to meet different performance requirements in terms of energy consumption, energy balancing, network lifetime and delay. Furthermore, through an extensive performance evaluation study and simulation of large-scale scenarios, the results showed that our proposed ZPR protocol achieved better performance compared to the state-of-the-art solutions in terms of network lifetime, energy consumption and data routing efficiency.
49Adaptive Consensus-Based Distributed Target Tracking With Dynamic Cluster in Sensor Networks
This paper is concerned with the target tracking problem over a filtering network with dynamic cluster and data fusion. A novel distributed consensus-based adaptive Kalman estimation is developed to track a linear moving target. Both optimal filtering gain and average disagreement of the estimates are considered in the filter design. In order to estimate the states of the target more precisely, an optimal Kalman gain is obtained by minimizing the mean-squared estimation error. An adaptive consensus factor is employed to adjust the optimal gain as well as to acquire a better filtering performance. In the filter's information exchange, dynamic cluster selection and two-stage hierarchical fusion structure are employed to get more accurate estimation. At the first stage, every sensor collects information from its neighbors and runs the Kalman estimation algorithm to obtain a local estimate of system states. At the second stage, each local sensor sends its estimate to the cluster head to get a fused estimation. Finally, an illustrative example is presented to validate the effectiveness of the proposed scheme.
50Optimal Deployment of Energy-Harvesting Directional Sensor Networks for Target Coverage
The technology of harvesting energy from the natural environment can be used to overcome the energy limitation of wireless sensor networks. In this paper, we consider the problem of deploying energy-harvesting directional sensor networks for optimal target coverage. It involves the directional sensing coverage, communication route selection, and energy neutral operation. We formulate it as a mixed integer linear programming model, and propose three heuristics to solve it, i.e., a linear program-based heuristic (LPBH), a two-stage heuristic (TSH), and a sensing- and routing-integrated greedy heuristic (SRIGH). Their approximation upper bounds and time complexities are analyzed. Finally, we conduct extensive simulation experiments to evaluate and compare them. Simulation results show that TSH is the fastest one among them, but achieves the lowest success rate and solution quality. LPBH and SRIGH can achieve roughly equal success rate and solution quality, and LPBH is the most time-consuming.