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Wireless Sensor and actor-network (WSAN) is the utmost significant research area in wireless communication technology. Actor nodes play a vital role during the processing and transmission of valuable data to the base station. WSAN performs its operations in a harsh environment and, therefore, prone to network failure. Moreover, an actor node’s failure causes the network into disjoint segments. Thus, the connectivity restoration of actor nodes is significant. This paper presents a novel technique, namely an efficient solution for connectivity restoration (ESCR), to detect the failure and ensure the connectivity among actor nodes. ESCR comprises two algorithms, i.e., assigning backup nodes and connectivity restoration process. The main objective of the proposed technique is to restore the network with efficient utilization of residual energy and minimum nodes movement. The effectiveness and performance of the ESCR technique are validated through extensive simulations and comparison with baseline approaches. The results show that the ESCR outperforms baseline approaches in terms of the number of nodes moved, total moved distance, reduction in the coverage area, and recovery time.

Node failures are inevitable in wireless sensor networks (WSNs) because sensor nodes in WSNs are miniature and equipped with small and often irreplaceable batteries. Due to battery drainage, sensor nodes can fail at any instance. Moreover, WSNs operate in hostile environments and environmental factors may also contribute to nodes failure. Failure of nodes leads to disruption of inter-node connectivity and might also lead to network partitioning. Failure to communicate with each other and with the base station can compromise the basic operation of the sensor network. For restoration of connectivity, a robust recovery mechanism is required. The existing connectivity restoration mechanisms suffer from shortcomings because they do not focus on energy-efficient operation and coverage-aware mechanisms while performing connectivity restoration. As a result, most of these mechanisms lead to the excessive mobility of nodes, which itself causes the utilization of excessive battery. In this work, we propose a novel technique called smart node relocation (SNR). SNR is capable of detecting and restoring the connectivity caused by either single or multiple node failures. For achieving energy efficiency, SNR relies on transmitting a lesser number of control packets. For achieving the goal of being coverage-aware, it tries to relocate only essential nodes while trying to restore connectivity. By performing extensive simulations, we prove that SNR outperforms the existing approaches concerning multiple performance metrics including but not limited to the total number of packets transmitted, total distance moved for connectivity restoration, the percentage reduction in field coverage.

Wireless Sensor Networks (WSNs) are widely used in most applications of the Internet of Things (IoT) for efficiently sensing the harsh environments, collecting important data, and sending them to the base station for further analysis. Therefore, the research community worldwide is actively participating in addressing and solving the challenges associated with WSNs. The common issue that is being studied and well-thought-out are how to increase the network's life span by resolving node failure problem and efficient energy utilization. This paper introduces a Cluster-based Node Recovery (CNR) connectivity restoration mechanism based on the concept of clustering. The proposed technique utilizes a distributed cluster-based approach to identify the failed nodes, while Cluster Heads (CHs) play a significant role in the restoration of connectivity. The simulation results show that the proposed technique efficiently addresses node failure and restores the connectivity by moving fewer nodes than other existing connectivity restoration mechanisms.

Wireless Sensor and actor networks (WSANs) are the most vital research area in the wireless communication field. It consists of sensors, actors, and the base station, where actor nodes work as these networks' spine. The network's main objective is to sense the critical information from the area of interest and then send it to the base station. After that, it can make accurate decisions. This project proposes an Energy-Efficient Routing Mechanism (EERM) technique for the effective routing process. It works in three phases, which are Network initialization, data gathering, and routing. Once the node senses the data and tries to forward it to the base station, it chooses the sensor/ actor nodes from its neighbors having more energy and less distance towards the base station, a final node. As a result, there are significantly fewer chances of data loss due to battery depletion. Moreover, it confirms that there is no data duplication. After successful data transmission, the node will be set as in sleeping mode to save energy. EERM evaluates with other gossiping routing techniques like FELGossiping, ELGossiping, and LGossiping. It notices that there is less data packet loss in it. More nodes are alive in additional iterations due to energy-efficient solutions, which increases the network lifetime.

Wireless Sensor Networks (WSNs) applications range across distinct application comprising of event detection at real-time. WSNs can be deployed for not only mobile nodes but also for static sensor nodes (SNs) for various applications which may include health care system, smart parking, environmental monitoring etc. Sensor nodes in WSN are constrained in terms of energy contents of each node and can be accessible by other nodes in a wireless medium are more likely to be susceptible to various categories of attacks. Wireless Network are more likely prone to various kinds of security attacks, one such type of attack caused by a malicious attacker, which can result to decay in the lifetime of the network and an adverse scenario can even lead to congestion in the entire network. This paper presents the overview of various attacks and their consequences on different layers and evaluates defense strategy used to mitigate the various categories of attacks on Wireless Sensor Networks. This study proposes a cluster-based approach for each node of a WSN where the nodes of network constrained by energy can organize and perform network duties as per the network performance for this one node performs the role of cluster head (CH) which is elected on the basis of the "Reputation" of a node which is an indicator of nodes individual behavior in the network and "Net_Credit_Score" which determines the cooperating behavior of sensor node in the cluster. Further, this study highlights few parameters which can be implemented to further enhance the defense strategy by taking into account the factors such as Cluster count, Stability factor of both the Cluster and Cluster Head and Intra-Cluster topology which can be crucial. This will result in formulating a road map for designing a secure and resistant reputation-based system for WSN to overcome the various security related attacks.

Sensor nodes in a sensor network often operate in harsh and challenging environments and this leads to frequent failure of sensor nodes. Failure of sensor nodes leads to partitioning in the network connectivity. For significant effectiveness of applications of sensor networks, the inter-sensor connectivity among sensors is vital. Some sensors are also involved in sustaining the flow of information from the sensor to unapproachable end users. The network can be split up into multiple incoherent blocks and cease working due to physical damage or onboard energy depletion. To deal with such scenarios, a plethora of node repositioning techniques are proposed in the literature. In this article, the recent and up to date mode of research on dynamic sensor repositioning in WSN is discussed. This article classifies sensor repositioning methods into on-demand and post-deployment repositioning based on whether the optimization is accomplished at deployment time or while the network is functioning.

Congestion control has a great importance in wireless sensor network (WSN), where efficient application of congestion control mechanisms can prolong the network lifetime. Thus, proper examination is needed to improve more refine way to address the congestion occurrence and resolution. While designing congestion control techniques, the maximum output can be achieved by efficient utilization of required resources within WSN. From last few years several approaches have been brought in, that consist of routing protocols which provide support with congestion control, congestion prevention, and reliable data routing. In old schemes the topology reset and extent traffic drop take place because sink node executes the congestion avoidance. Therefore, node level congestion avoidance, detection, congestion preventing, and resolution mechanisms have been proposed during past few years. Our paper provides a brief overview and performance comparison of centralized and distributed congestion control algorithms in WSN.

Wireless sensor and actor network’s connectivity and coverage plays a significant role in mission-critical applications, whereas sensors and actors respond immediately to the detected events in an organized and coordinated way for an optimum restoration. When one or multiple actors fail, the network becomes disjoint by losing connectivity and coverage; therefore, self-healing algorithm is required to sustain the connectivity and coverage. In this paper two algorithms; Permanent Relocation Algorithm for Centralized Actor Recovery (PRACAR) and Self-Route Recovery Algorithm (SRRA) for sensors have been proposed for connectivity and coverage. The effectiveness of proposed technique has been proved by realistic simulation results which ensure that our proposed technique better handles the connectivity and coverage.

Wireless sensor networks are envisioned to play a very important role in the Internet of Things in near future and therefore the challenges associated with wireless sensor networks have attracted researchers from all around the globe. A common issue which is well studied is how to restore network connectivity in case of failure of single or multiple nodes. Energy being a scarce resource in sensor networks drives all the proposed solutions to connectivity restoration to be energy efficient. In this paper we introduce an intelligent on-demand connectivity restoration technique for wireless sensor networks to address the connectivity restoration problem, where nodes utilize their transmission range to ensure the connectivity and the replacement of failed nodes with their redundant nodes. The proposed technique helps us to keep track of system topology and can respond to node failures effectively. Thus our system can better handle the issue of node failure by introducing less overhead on sensor node, more efficient energy utilization, better coverage, and connectivity without moving the sensor nodes.

Wireless Sensor and actor networks (WSANs) are the most promising research area in the field of wireless communication. It consists of large number of small independent sensor and powerful actor nodes equipped with communication and computation capabilities. Actors gather sensor’s data and react collaboratively to attain application particular assignments. A powerful connected inter-actor network is required to coordinate its operations. Actor node may fail due to the battery depletion or any hardware failure and this failure may divide the network into disjoint segments. This problem can degrade the network performance but also reduce the efficiency and effectiveness of the network. To restore the network into its original state, the researchers have proposed many connectivity restoration techniques during last few years. This paper provides a brief review of the existing connectivity restoration techniques for WSANs with their advantages and limitations.