Energy-efficient data gathering remains a fundamental challenge in Underwater Wireless Sensor Networks (UWSNs) due to the inherent limitations of multi-hop communication, which often result in excessive energy depletion near the sink, premature network partition, and degraded data collection performance. This paper proposes GA-UPNR (Genetic Algorithm Approach for UGV Path and Node Routing), a novel shoreside data collection framework that decomposes the problem into two optimization subproblems. The first genetic algorithm constructs energy-balanced multi-hop routing trees from surface nodes to distributed shoreside nodes to maximize network lifetime. The second genetic algorithm determines the optimal set of stopping points for an Unmanned Ground Vehicle (UGV), minimizing the travel distance required to collect data from all shoreside nodes. The two algorithms operate independently and are executed sequentially, providing a scalable solution for efficient data retrieval. Simulation results with 500 nodes indicate that GA-UPNR-Routing achieves longer network lifetime and higher connectivity compared to BMBS, SS-Dijkstra, and MS-Dijkstra. Specifically, GA-UPNR-Routing achieves a network lifetime of 40.14 rounds, in contrast to 21.16, 17.01, and 5.25 rounds for BMBS, MS-Dijkstra, and SS-Dijkstra, respectively. For the UGV stopping point selection, GA-UPNR-Path requires an average of 9.37 stops, whereas MCF and NPS require 11.07 and 105.61 stops, respectively. These results suggest that the GA-UPNR framework is suitable for scalable data collection in long-term marine monitoring applications.

In Wireless Rechargeable Sensor Networks (WRSNs), prolonging the sensors’ lifetime is a crucial issue that requires attention. Most studies in the field have focused on path planning for mobile chargers to replenish energy supply for static sensors. Different from the most existing studies, this paper explores the energy replenishment problem in WRSNs with mobile sensors. The paper addresses two issues to extend the network’s lifetime:$1$) how to balance energy consumption between mobile sensors using their mobility capabilities; and$2$) how to dispatch redundant mobile sensors, charged and calibrated, to replace low-energy sensors. For the first issue, an energy balancing algorithm is proposed that uses cascaded movement to better the cascading schedule. For the second issue, a redundant mobile sensor dispatch algorithm is proposed that prioritizes mobile sensors most in need of energy replenishment for replacement by a charged and calibrated redundant mobile sensor. The proposed algorithms are extensively evaluated through simulation and have demonstrated their effectiveness in achieving energy balance and prolonging the network lifetime.Note to Practitioners—Industrial automation applications often involve harsh and hazardous environments with high temperatures, dirt, dust, corrosive materials, and chemical risks. To ensure the longevity of sensors in such conditions, in addition to considering charging, sensors must also be regularly maintained and calibrated for accurate data sensing. However, maintaining and calibrating sensors requires the use of precise instruments that cannot be handled by mobile chargers. To address this issue, we propose studying how mobile sensors can cooperate with each other to complete monitoring tasks and return to the base station for charging, maintenance, and calibration before they run out of energy. The proposed algorithms are applicable to real-life precision monitoring applications in harsh or hazardous environments. This paper provides pseudo code, mathematical expressions, performance evaluation, and results, which can serve as a practical implementation guide for practitioners.

Due to the rapid development of the Internet of Things, cloud computing, big data, and software-defined networks technologies, vehicular ad hoc networks have evolved into software-defined Internet of Vehicles (IoV). In software-defined IoV, messages transmitted by vehicles are transferred using wireless communication technology, so attackers can easily attack specific vehicles and Road-Side Units (RSUs) within the wireless communication range. When any vehicle or RSU is under attack or control, the entire network may collapse and produce incorrect computing results, which in the worst case, can lead to car accidents. Therefore, building a highly reliable and fault-tolerant software-defined IoV is of high importance. In this paper, we visit the consensus problem in software-defined IoV. Software-defined IoV is built with infrastructures, that is, RSUs. RSUs have a backhaul capacity and a powerful computing capacity. Thus, in software-defined IoV, we will focus on how to use RSUs to assist vehicles in reaching a consensus.

The combination of the Internet of Things (IoT) and Cloud computing are both popular applications that are based on the Internet. However, the traditional networking structure can no longer support the transmission of the huge number of packets required by cloud computing and IoT. Therefore, a new‐generation architecture, software‐defined networking (SDN), came into being. The new‐generation SDN can control routing through software, making flexible and convenient management a key feature of SDN. However, attacks and threats are prevalent in today’s networking environment. When an SDN controller encounters a hacker attack or virus infection, it will not function properly. Hence, we need to design a fault‐tolerant mechanism for the above environment. In this paper, a fault‐tolerant consensus protocol is proposed to improve the fault tolerance of SDNs with multiple controllers.

Abstract High-utility itemset mining (HUIM) is considered as an emerging approach to detect the high-utility patterns from databases. Most existing algorithms of HUIM only consider the itemset utility regardless of the length. This limitation raises the utility as a result of a growing itemset size. High average-utility itemset mining (HAUIM) considers the size of the itemset, thus providing a more balanced scale to measure the average-utility for decision-making. Several algorithms were presented to efficiently mine the set of high average-utility itemsets (HAUIs) but most of them focus on handling static databases. In the past, a fast-updated (FUP)-based algorithm was developed to efficiently handle the incremental problem but it still has to re-scan the database when the itemset in the original database is small but there is a high average-utility upper-bound itemset (HAUUBI) in the newly inserted transactions. In this paper, an efficient framework called PRE-HAUIMI for transaction insertion in dynamic databases is developed, which relies on the average-utility-list (AUL) structures. Moreover, we apply the pre-large concept on HAUIM. A pre-large concept is used to speed up the mining performance, which can ensure that if the total utility in the newly inserted transaction is within the safety bound, the small itemsets in the original database could not be the large ones after the database is updated. This, in turn, reduces the recurring database scans and obtains the correct HAUIs. Experiments demonstrate that the PRE-HAUIMI outperforms the state-of-the-art batch mode HAUI-Miner, and the state-of-the-art incremental IHAUPM and FUP-based algorithms in terms of runtime, memory, number of assessed patterns and scalability.

Unlike traditional networking structures, the new-generation software-defined network (SDN) separates the network control and forwarding and enables the network control to be software programmable, making flexible and convenient management a key feature of SDN. The early structure of SDN relies on centralized control, that is, the entire network is managed by only one controller. However, SDN managed by only one controller may suffer single point of failure (SPOF) problems. Besides, if the network is large in size, the scalability problem will make it hard to ensure the stability and performance of the network. Thus, later researchers have proposed to use multiple controllers to control the network collaboratively. A distributed control structure involving collaboration of multiple controllers can effectively enhance the performance and stability of SDNs. However, attacks and threats are prevalent in today's networking environment. SDN controllers may lose its normal functions when it is attacked by hackers or infected with viruses. In order to provide a fault-tolerant and reliable computing environment in distributed SDNs, we design a fault-tolerant consensus protocol to improve fault tolerance of distributed SDNs.

The energy replenishment problem is an important issue in Wireless Rechargeable Sensor Networks (WRSNs). In this paper, we discuss how to make use of the mobility capability of sensors to balance energy consumption among mobile sensors before they get assistance from fully charged redundant mobile sensors.

Sensing data gathering is an important and fundamental issue in the Internet of Things. However, for battery-powered sensors, energy depletion is unavoidable. Using mobile sinks to collect sensing data by one-hop transmission is an effective way to prolong the lifetime of wireless sensor networks but will inevitably cause an excessive long delay time of data gathering. In order to reduce the delay time of mobile data gathering, it is necessary to incorporate multihop transmission into mobile data gathering. In this paper, a new mobile data gathering algorithm with multihop transmission is proposed to reduce the delay time of data gathering. The proposed algorithm is called the bounded relay combine-TSP-reduce (BR-CTR). The BR-CTR algorithm visits the convergence area of sensors' communication ranges to reduce the number of visiting points. The BR-CTR algorithm is integrated with a path adjustment mechanism, which can further shorten the planned traveling path effectively. In performance evaluation, we compare the BR-CTR algorithm not only with the existing mobile data gathering algorithms with onehop transmission but also with the existing mobile data gathering algorithms with multihop transmission in terms of the length of traveling path, delay time, network lifetime, and buffer size requirement. Experimental results indicate that the proposed algorithm has high performance on all the above-mentioned indices.

In this paper, we define a new type of coverage problem named target-barrier coverage problem in wireless sensor networks. A target-barrier is a continuous circular barrier formed around the target. The target-barrier has a dboundconstraint that is set depending on applications and needs, where dboundis the minimum distance of the constructed barrier from the target. Target-barrier coverage is very suited for application in defense surveillance, including detection of intrusion from outside and prevention of barrier breaching from inside. For instance, in a jail scenario, sensors can be deployed to enclose a jail with the constraint of dboundto detect the escape of prisoners or unauthorized entry into the jail for rescuing prisoners. We focus on how to minimize the number of members required to construct target-barriers in a distributed manner while satisfying the dboundconstraint and minimizing the amount of message exchange required. In performance evaluation, we compare our solution with the solution of related work and the Brute-Force algorithm which can find the minimum number of target-barrier members required. Our experimental results show that the proposed algorithm delivers satisfactory results in terms of the number of target-barrier members required and the amount of message exchange required.

In this paper, we propose a new geographic holebypassing routing algorithm based on virtual convex model in Wireless Ad hoc Networks (WANETs). Our method is to convert an actual hole into a basic virtual convex first and then use line segments that are parallel to the basic virtual convex to find candidates of anchor points. Later, among these candidates, we choose appropriate anchor points to be the turning points in the packet forwarding process. The advantage of using turning points to relay packets is that the problem of local minimum phenomenon can be avoided. Besides, packets will not be forwarded along the hole boundary. Thus, the hole-diffusion problem will not get worse, and the number of relay hop counts of packets can be effectively reduced.

In some applications, the moving path of the mobile sink is unpredictable. For sensors that have detected an event of interest, it is necessary to find the location of the mobile sink first before they can report the data. In this paper, we will discuss how source sensors can locate the constantly moving mobile sinks and send data packets through a less number of forwarding hop counts. The effectiveness of the proposed algorithm is verified by comparing with other data gathering via uncontrolled mobile sink algorithms. Moreover, our experimental results also confirm that the proposed algorithm can ensure that all source sensors can find the location of the mobile sink and reduce the average forwarding hop counts of data packets.

In the cloud computing environment, resources are distributed among processors of a computing cluster. When performing a task, processors have to request needed resources that do not exist in them from other processors in the network. If the requested resource is currently used by another processor, they have to wait until the resource is released. If the resource is not released, a deadlock may occur. Deadlocks can be avoided if the order of jobs is properly arranged in advance. However, there may exist malicious faulty components in the cloud computing environment. Malicious faulty components may disturb job scheduling of fault-free servers, causing them to generate inconsistent schedules. In this paper, we investigate the Interactive Consistency (IC) problem in the cloud computing environment to develop a protocol that can exclude influences from malicious faulty components to help servers achieve consistent job scheduling. The proposed IC protocol is called Efficient Interactive Consistency Protocol with Weight Consideration (EICPweight). In this problem, each server will collect job requests from end-users first, then give a weighted value to each job according to its amount, and finally generate a consistent schedule of jobs based on their weighted values. Moreover, we also propose a new Cutoff-test mechanism to enhance the performance of the proposed protocol.

The Sensor Relocation (SR) problem is an important issue in Wireless Sensor Networks (WSNs). For WSNs with an ongoing surveillance task, it is necessary to follow a strict response time requirement when relocating redundant sensors to the requesting places. In this study, we revisit the SR problem in mobile WSNs. The proposed algorithm can find the redundant sensor nearest to the requesting place with low message overhead. The performance evaluation done in this research has confirmed its superior performances.

In a cooperative network, we need a mechanism that allows all correct processors to reach a common agreement. Hence, more and more attention has been drawn on the agreement related problems (Byzantine Agreement (BA) problem and Consensus problem). In previous results, the goal of BA and Consensus is obtaining a common value no matter this value is good or bad. To address this problem, Correia, Bessani and Veríssimo proposed the Byzantine Generals with Alternative Plans (BGAP) protocol that requires the common value come from the good plan set. BGAP is a graceful and practical protocol. They also pointed out that the BA problem with alternative plans is unsolvable if correct processors have different good plans and bad plans. In this paper, we propose the Plan_Consensus Protocol (PCP) to ensure that all correct processors obtain a consistent good plan set and a consistent bad plan set in the network.

Convergecast is a fundamental operation in wireless sensor networks. This paper uses ZigBee tree-based, beacon-enabled networks to support convergecast. In the network, ZigBee routers form a tree backbone and ZigBee end devices connect to routers. Some previous works have discussed to use ZigBee tree networks to support regular data reporting. In this work, we further consider the event data reporting scenario, where the network may randomly have urgent events. We assign each router a regular mode slot and several event mode slots. To support regular data reporting, routers and their child devices periodically wake up in their regular mode slots to sense and to report. When an event happens, devices nearby the event can wake up more times in their event mode slots, and routers can collect more event data from child devices and report more frequently. In this paper, we design tree formation algorithms, slot assignment rules, and event mode operations to support event data reporting. Simulation results show that our designs can indeed support both regular and event data reporting.

Previous research of barrier coverage did not consider breadth of coverage in Wireless Visual Sensor Networks (WVSNs). In this paper, we consider breadth to increase the Quality of Monitor (QoM) of WVSNs. The proposed algorithm is called Distributed β-Breadth Belt-Barrier construction algorithm (D-TriB). D-TriB constructs a belt-barrier with β breadth to offer β level of QoM, we call β-QoM. D-TriB can not only reduce the number of camera sensors required to construct a barrier but also ensure that any barrier with β-QoM in the network can be identified. Finally, the successful rate of the proposed algorithm is evaluated through simulations.

In wireless mobile sensor networks, spatial full-coverage only can be achieved when the surplus mobile sensors contribute a larger coverage area than the hole size. The temporal full coverage problem asks to monitor every point of a given monitoring region within a specific time interval. This paper considers a mobile WSN that contains holes but exists no redundant mobile sensor to heal the hole. To achieve the temporal full-coverage purpose, a distributed hole-movement mechanism is proposed to balance the energy consumptions of mobile sensors. Simulation study reveals that the proposed hole-movement mechanism enhances the coverage ratio of WSN and balance the energy consumption of mobile sensor nodes.

In previous results, most existing Byzantine agreement (BA) protocols are designed for pure wired or pure wireless networks. In practice, most current networks are combined wired and wireless environments. In this paper, we extend the BA problem over combined wired/wireless network, consisting of both powerful computing processor and low-power mobile processor. Furthermore, the communication overhead of the BA protocol is inherently large because the BA protocol requires numerous rounds to exchange messages. Secure group communications over a combined wired/wireless network is very important. The protocols proposed in this paper use the hierarchical model concept to reduce the communication overhead and provide secure group communications well suited for combined wired/wireless networks

The Byzantine agreement (BA) problem has been widely discussed in the literature concerned. Most BA protocols can reach a common agreement by way of fault masking. However, in a highly reliable fault-tolerant distributed system, just reaching a common agreement is not enough. We need to take into consideration another related problem called the fault diagnosis agreement (FDA) problem. The goal of solving the FDA problem is to make each fault-free processor detect/locate the common set of faulty components in the distributed system. We shall solve the FDA problem with the dual failure mode over a multicasting network system. The proposed FDA protocol can detect/locate the maximum number of faulty components with the dual failure mode to solve the FDA problem in a synchronous multicasting network

Under many circumstances, reaching a common agreement in the presence of faulty components is the central issue of fault tolerant distributed computing. So the Byzantine agreement (BA) problem has become more and more important in distributed systems. Traditionally, the BA problem was visited in a fully connected network (FCN), broadcasting network (BCN) and generalized connected network (GCN). Subsequently, malicious fault assumption with processors or communication media was extended to a hybrid fault model on both processors and communication media. However, the network structures (topologies) of FCN, BCN and GCN are not practical. In this study, we lighten restrictions of the network structure to revisit the BA problem with multicasting network (MCN). The proposed protocol uses the minimum number of rounds of message exchange and can tolerate the maximum number of allowable faulty components to make each fault-free processor reach a common agreement in an MCN.