Minimum Relay Research Articles

Relay Node Selection Methods for UAV Navigation Route Constructions in Wireless Multi-Hop Network Using Smart Meter Devices

Unmanned aerial vehicles (UAVs) offer solutions to issues like traffic congestion and labor shortages. We developed a distributed UAV management system inspired by virtual circuit and datagram methods in packet-switching networks. By installing houses with wireless terminals, UAVs navigate routes in a multi-hop network, communicating with ground nodes. UAVs are treated as network packets, ground devices are treated as routers, and their connections are treated as links. Activating all nodes as relays increases control message traffic and node load. To optimize connectivity, we minimize relay nodes, connecting non-relay nodes to the nearest relay. This study proposes four relay node selection methods: random selection, two adjacency-based methods, and our innovative approach using Multipoint Relay (MPR) from the Optimized Link State Routing Protocol (OLSR). We evaluated these methods according to their route construction success rates, relay node counts, route lengths, and so on. The MPR-based method proved most effective for UAV route construction. However, fewer relay nodes increase link collisions, and we identify the minimum relay density needed to balance efficiency and conflict reduction.

Connectivity Recovery Based on Boundary Nodes and Spatial Triangle Fermat Points for Three-Dimensional Wireless Sensor Networks.

In recent years, wireless sensor networks have been widely used, especially in three-dimensional environments such as underwater and mountain environments. However, in harsh environments, wireless sensor networks may be damaged and split into many isolated islands. Therefore, restoring network connectivity to transmit data effectively in a timely manner is particularly important. However, the problem of finding the minimum relay nodes is NP-hard, so heuristics methods are preferred. This paper presents a novel connectivity recovery strategy based on boundary nodes and spatial triangle Fermat points for three-dimensional wireless sensor networks. The isolated islands are represented as the boundary nodes, and the connectivity recovery problem is modeled as a graph connectivity problem. Three heuristics algorithms-the variant Kruskal algorithm, the variant Prim algorithm, and the spatial triangle Fermat point algorithm-are proposed to solve this problem. The variant Kruskal algorithm and the variant Prim algorithm connect the isolated islands by constructing the minimum spanning tree to link all the boundary nodes and placing relay nodes along the edges of this tree. We derive an accurate formula to determine the coordinates of spatial triangle Fermat points. Based on this formula, the spatial triangle Fermat point algorithm constructs a Steiner tree to restore network connectivity. Extensive simulation experiments demonstrate that our proposed algorithms perform better than the existing algorithm.

Adaptive Directional Overcurrent Relay Coordination in Microgrid Considering Optimal Full Setting Parameters

This article proposes a novel approach for the optimal coordination of adaptive directional overcurrent relay (ADOCR) for modernized active distribution system (ADS) with microgrid (MG) functions. The goal is to keep the coordinating circumstances while reducing the protective relay operation time, as much as possible. With the proposed round-off mixed-integer particle swarm optimization (ROMI-PSO), the setting parameters are not limited to only relay time multiplier setting (TMS) and pickup current setting (PS) but can include the discrete parameter as relay characteristic curve setting (CS). In the proposed framework, The CS can be both IEC and IEEE standard curves in the proposed framework. Four buses radial system and IEC-benchmark MG system were used in a number of simulation experiments. Comparing the suggested methodology to other current methods revealed that it is more effective at determining the minimum relay operating times and ensuring the proper operation of protections under various fault allocations and operating circumstances.

Partition detection and recovery by UAVs in damaged WSANs using N‐angle clustering

SummaryConnectivity is essential in wireless sensor and actor networks (WSANs) deployed for data collection and monitoring applications. WSANs serving in inhospitable environments are prone to damage, and sometimes, the concurrent multiple node failures in the same area may cause network partitioning. The autonomous network recovery in harsh environments is challenging because the nodes in different partitions cannot determine the scope of the damage. This paper proposes an approach called partition detection and recovery by unmanned aerial vehicles (UAVs) in damaged WSANs using N‐angle clustering (N‐anglePDRU), which consists of all the phases required to accumulate information about the network partitions and reconnect them successfully. The algorithm is evaluated for different randomly generated network topologies according to various state‐of‐the‐art parameters such as detection and recovery time, messages transmitted, relay node count, and distance traveled by UAVs. The proposed approach is also compared with the existing algorithms, and the obtained results demonstrate that N‐anglePDRU recovers the partitioned network in less recovery time with minimum relay nodes and distance traveled.

UAVs assisted Network Partition Detection and Connectivity Restoration in Wireless Sensor and Actor Networks

Wireless sensor networks have been extensively employed in different data collection and monitoring applications because of their serviceability in harsh environments. The interconnected network is a fundamental requirement for these applications. The simultaneous failure of multiple nodes causes connectivity loss and can partition the network into various segments. It is crucial to identify the partitions in the partitioned network and reconnect them to achieve application-related goals. This paper provides a new Unmanned Aerial Vehicles (UAVs) assisted Network Partition Detection and Connectivity Restoration (UAV-NetRest) solution encompassing all phases from failure detection to network partition recovery. The proposed algorithm is tested according to detection and recovery time, distance traveled by UAVs in detection and recovery phases, the number of messages transmitted, and the number of deployed relay nodes. The performance of the UAV-NetRest's recovery algorithm is compared with the existing recovery techniques proposed in the literature. The simulation results demonstrate that the UAV-NetRest recovers the network with significantly less recovery time and minimum distance traveled by UAVs. The algorithm deploys minimum relay nodes as compared to other techniques. Network partitioning is an unpredictable incident, and simulation results entirely depend on the number of failed nodes, proximity and topology of network partitions, and the number of UAVs employed. The paper provides a new framework that covers all the aspects required for network partition recovery. This proposed work can be a seed source for future researchers to further optimize the detection and recovery phases.

Centralized Multi-Hop Routing Based on Multi-Start Minimum Spanning Forest Algorithm in the Wireless Sensor Networks.

Wireless sensor networks (WSNs) are widely applied in environmental monitoring, target tracking, military, and industrial fields. However, the battery energy of sensor nodes in WSNs is limited, which limits its development. Previous studies have shown that clustering protocols and multi-hop communication are beneficial to reduce nodes energy consumption. The multi-hop protocol based on low energy adaptive clustering hierarchy (LEACH) has been proven to significantly reduce energy dissipation. However, LEACH-based multi-hop protocols generally have the problem of unbalanced energy dissipation and data conflicts. In this paper, we propose a centralized multi-hop routing based on multi-start minimum spanning forest (LEACH-CMF) to optimize LEACH. In order to realize multi-hop communication, we introduced a multi-start minimum spanning tree algorithm to select relay nodes with the minimum relay cost and generate appropriate multi-hop paths. To avoid data collision in multi-hop communication and make nodes including the cluster heads sleep as much as possible in the non-working state, we design a bottom-up continuous time slot allocation method to improve the time division multiple access (TDMA) cycle. We performed simulation in NS2. The simulation results show that the network lifetime is approximately doubled compared to LEACH and centralized low energy adaptive clustering hierarchy (LEACH-C). The simulation results show that the proposed protocol can effectively balance the energy dissipation of nodes and prolong network lifetime.

Optimal Protection Coordination of Nonstandard Overcurrent Relays Using Hybrid QCQP Method

The optimal protection coordination (OPC) problem of directional overcurrent relays (OcR) in power system networks is a complex, highly constrained nonconvex optimization problem because of the nonlinear inverse nature of the OcR characteristics. Finding the best OcR settings by solving OPC is a challenging task because of its nonconvex nature. Although various heuristic, hybrid heuristic, and traditional optimization-based solution methods are suggested in the literature, such methods are just far enough to provide better optimal solutions to the OPC problem. Besides, the standard inverse characteristics of the OcRs with fixed characteristic coefficients limit the OPC problem from finding the best settings. As digital relaying technology has the feasibility to embed more relay settings, nonstandard relay characteristics can be developed to achieve minimum relay operating times. To find the best OcR operating times, a nonstandard characteristic based OPC problem is formulated in this work by parameterizing the OcR characteristic coefficients along with the OcR settings. By setting two variables of the proposed OPC using particle swarm optimization (PSO), the rest of OPC is formulated as a quadratic programming problem with quadratic constraints (QCQP). The proposed method is developed in MATLAB programming platform, and results are found to be satisfactory.

Relay Selection Algorithm for Cognitive Relay Network

In the cognitive relay network, due to the different fading characteristics of communication links, not all relay nodes have constructive impacts on the system performance. A relay selection algorithm is proposed to obtain the minimum relay transmission power while satisfying the secondary user SINR requirements and interference temperature constraints. The algorithm first introduces l1 norm as the approximation of l0 norm, then constructs a minimum relay transmission power constraint problem to select appropriate relays. Simulation results show that the algorithm can efficiently conduct relay selection with mild system transmission power increase over traditional full cooperation cognitive relay network.

Variable-dimension swarm meta-heuristic for the optimal placement of relay nodes in wireless sensor networks

A wireless sensor network is a network consisting of wireless sensor nodes. There are usually requirements that need to be met when deploying a wireless sensor network, one being the placement of nodes. Due to placement requirements and limited node transmission range, a network might be partitioned initially. Therefore, additional relay nodes are added to the network to form an interconnected network. In this article, the minimum relay nodes placement problem in wireless sensor networks is addressed. This problem addresses the placement of relay nodes: the minimum number needed and where the nodes should be placed. The problem is formulated as a Steiner tree problem with minimum Steiner points and a bounded edge length problem, which is NP-hard. In this article, we present a variable-dimension meta-heuristic based on particle swarm optimization called multi-space particle swarm optimization to address the problem. We tested multi-space particle swarm optimization using randomly generated instances of the Steiner tree problem with minimum Steiner points and a bounded edge length problem of varying sizes and found that multi-space particle swarm optimization is effective in addressing the Steiner tree problem with minimum Steiner points and a bounded edge length problem.

Toward Robust Relay Placement in 60 GHz mmWave Wireless Personal Area Networks with Directional Antenna

Multimedia streaming applications with stringent QoS requirements in 60 GHz mmWave wireless personal area networks (WPANs) demand high rate and low latency data transfer as well as little service disruption. In this paper, we consider the problem of robust relay placement in 60 GHz WPANs with directional antenna. Relays forward traffic from transmitter devices to receiver devices facilitating i) the primary communication path for non-line-of-sight (NLOS) transceiver pairs, and ii) secondary (backup) communication path for line-of-sight (LOS) or NLOS transceiver pairs. By incorporating a classic directional antenna model and characterizing the link contention, we formulate the robust minimum relay placement problem and the robust maximum utility relay placement problem with the objective to minimize the number of relays deployed and maximize the network utility, respectively. Efficient algorithms are developed to solve both problems and have been shown to incur less service disruption in presence of moving subjects that may block the LOS paths in the environment.

Restoring Virtual Backbone of Wireless Sensor Network Using Position Restricted Relay Nodes

Abstract In Wireless Sensor Network (WSN), sensor nodes send sensed data through multi-hops involving intermediate relay nodes. Construction of virtual backbone (VB) of sensor network is preferred to reduce the energy depletion of the WSN. The VB brings substantial benefits by simplifying routing and topology control. In WSN, sensors are prone to failure, due to power depletion or some other reasons. Therefore, the existing VB may be partitioned into segments after failure. Hence, re-construction of VB is an important issue in sensor network. This can be achieved either by discovering alternate backbone or by redeployment additional new relay nodes to restore the VB. This paper proposes an efficient strategy for restoring VB by connecting disconnected VBs using minimum relay nodes. Finding the optimal number of relay nodes and their positions is NP-hard, heuristic algorithms are proposed to minimize the repairing cost.

Instantaneous Relaying: Feasibility Conditions for Interference Neutralization

In this letter, we study the feasibility of interference neutralization (IN) for a two-user interference channel (IC) with a multi-input-multi-output (MIMO) instantaneous relay. With this channel model, Lee et al. show that instantaneous relaying is a promising approach to neutralize interference and increase the degrees of freedom (DoF). However, only the scenario where each node has the same number of antennas has been studied yet, for general antenna configuration at the relay, the maximum achievable DoF remains unknown. Assuming linear transceivers with an amplify-and-forward (AF) relay, we first present the necessary condition for generalized IN. Then, we derive the necessary and sufficient conditions for pure IN and coordinated IN. The derived sufficient conditions give rise to the minimum relay antenna configuration to support interference-free transmission. Our proof throws lights on how to use the relay resources to neutralize the interference efficiently.

A Review on Methodologies for CapacityImprovement with Minimum Delay in WMN

In recent years there is explosive growth towards wireless broadband technologies which accelerating the need to design an efficient “last mile” access network in a cost-effective manner. Wireless Mesh Network (WMN) is emerging as promising technology for many useful applications. Over the past decade the size, cost and power requirements of radios has declined, enabling multiple radios to be contained within a single mesh node, thus allowing for greater modularity each can handle multiple frequency bands and support a variety of functions as needed such as client access, packet forwarding and scanning with minimum relays between nodes in wireless network. In order to making cost –efficient network different routing protocols are proposed. In this paper after analysing the different methodologies we use improved methodology that will not only find the shortest path but also making an efficient network by minimizing the delay from source to destination nodes in wireless network.

Energy Efficient Unequal Clustering Algorithm with Disjoint Multi-hop Routing Scheme for Wireless Sensor Networks

The main aim of this paper is to avoid hotspot problem in wireless sensor network with uniform energy dissipation among cluster heads in the network. It proposes an energy efficient unequal clustering mechanism to form limited and equivalent number of clusters across different levels of wireless sensor network to enable invariable energy consumption among them. Concentrated cluster formation near base station ensures minimum relay burden on cluster heads to avoid hot-spot problem in multi-hop data forwarding model. Equivalent number of clusters at each level ensures in-common network load on each cluster head among different data forwarding routes. In addition, a simple disjoint multihop routing technique is proposed for smooth data forwarding process. Simulation results evidence that the proposed unequal clustering algorithm overcomes hotspot problem with invariable energy dissipation among cluster heads across the network and elevates sensor network lifetime.

Approximation Algorithms for Constrained Relay Node Placement in Energy Harvesting Wireless Sensor Networks

The constrained relay node placement problem in a wireless sensor network seeks the deployment of a minimum number of relay nodes (RNs) in a set of candidate locations in the network to satisfy specific requirements, such as connectivity or survivability. In this paper, we study the constrained relay node placement problem in an energy-harvesting network in which the energy harvesting potential of the candidate locations are known a priori. Our aim is to place a minimum number of relay nodes, to achieve connectivity or survivability, while ensuring that the relay nodes harvest large amounts of ambient energy. We present the connectivity and survivability problems, discuss their NP-hardness, and propose polynomial time ${\mbi{\cal O}}$ (1)-approximation algorithms with low approximation ratios to solve them. We validate the effectiveness of our algorithms through numerical results to show that the RNs placed by our algorithms harvest 50% more energy on average than those placed by the algorithms unaware of energy harvesting. We also develop a unified-mixed integer linear program (MILP)-based formulation to compute a lower bound of the optimal solution for minimum relay node placement and demonstrate that the results of our proposed algorithms were on average within 1.5 times of the optimal.

Fuzzy Logic Overcurrent Relay Using Sugeno Technique

The overcurrent relay is the simplest and most economical type of protective relay, the relay is designed to operate when more than a predetermined amount of current flows into a particular portion of the power system. Time delay between relay's main zone and it's backup will keep the selectivity of the system, The inverse definite minimum time relay will calculate the time delay inversely proportional to the fault current level. This technique has some weaknesses where the time delay provided for a given case maybe too high and if the fault is not isolated immediately then damage could be caused to other connected equipment in the power system. This paper presents the fuzzy logic relay using Sugeno technique to determine the time delay, and using of symmetrical components application in detecting fault type, also it presents a comparison between times calculated by other techniques.

Feasibility Conditions for Interference Neutralization in Relay-Aided Interference Channel

Interference neutralization (IN) is a new interference management mechanism found from and inherent in interference networks with relays. In this paper, we study the feasibility of IN for relay-aided multi-input-multi-output (MIMO) interference broadcast channel (MIMO-IBC) without symbol extension. Assuming linear transceiver with multiple amplify-and-forward relays, we consider fully connected symmetric systems, where each base station (BS), relay, and user is equipped with multiple antennas, and each user desires multiple data streams. We first present the necessary condition of generalized IN, which is the proper condition to ensure interference-free transmission with linear transceivers for general relay-aided MIMO-IBC. We then find and prove the necessary and sufficient condition of the feasibility of coordinated IN and pure IN for a class of relay-aided MIMO-IBC, where the sufficiency is proved by constructing a full rank coefficient matrix of interference-free transmission equation with sub-matrices of special structures. We show that when each BS and user has the minimal antenna configuration for data transmission, the sufficient and necessary condition for coordinated IN is the same as the necessary condition for generalized IN. When there is an arbitrary number of antennas at the BSs and users, the derived sufficient conditions give rise to the minimum relay configuration required by the coordinated IN and pure IN to support a given number of data streams without interference. Our proof sheds lights on how to use the relay resources to neutralize the interference in an efficient way. The results are applicable for both relay-aided MIMO-IBC and relay-aided interference channel (MIMO-IC).

Backbone construction with relay node placement for energy‐efficient wireless sensor networks

ABSTRACTIn this paper, we address the energy‐efficient connectivity problem of a wireless sensor network (WSN) that consists of (1) static sensor nodes that have a short communication range and limited energy level, and (2) relay nodes that have a long communication range and unlimited power supply, and that can be added or relocated arbitrarily. For such a WSN, existing studies have been focused on the design of efficient approximation algorithms to minimize the number of relay nodes. By contrast, we propose a unified backbone construction framework that can be performed in a centralized manner with two objectives: (1) to minimize the number of nodes in the backbone and (2) to maximize the lifetime of the network. To solve such a challenging problem, we formulate three subproblems: (1) partial dominating set with energy threshold (PDSET); (2) partial dominating set with largest residual energy (PDSLE); and (3) minimum relay node placement (MRNP). For these three subproblems, we develop polynomial‐time algorithms. We also prove that our algorithm for PDSLE is optimal, and our algorithm for the PDSET and MRNP problems have small approximation ratios. Numerical results show that the proposed framework can significantly improve energy efficiency and reduce backbone size. Copyright © 2012 John Wiley & Sons, Ltd.

Towards augmenting federated wireless sensor networks in forestry applications

Environmental Monitoring (EM) has witnessed significant improvements in recent years due to the great utility of wireless sensor networks (WSNs). Nevertheless, due to harsh operational conditions in such applications, WSNs often suffer large-scale damage in which nodes fail concurrently and the network gets partitioned into disjoint sectors. Thus, reestablishing connectivity between the sectors, via their remaining functional nodes, is of utmost importance in EM, especially in forestry. In this regard, considerable work has been proposed in the literature tackling this problem by deploying Relay Nodes (RNs) aimed at reestablishing connectivity. Although finding the minimum relay count and positions is NP-Hard, efficient heuristic approaches have been anticipated. However, the majority of these approaches ignore the surrounding environment characteristics and the infinite 3-dimensional (3-D) search space that significantly degrades network performance in practice. Therefore, we propose a 3-D grid-based deployment for RNs in which the relays are efficiently placed on grid vertices. We present a novel approach, named fixing augmented network damage intelligently, based on a minimum spanning tree construction to re-connect the disjointed WSN sectors. The performance of the proposed approach is validated and assessed through extensive simulations, and comparisons with two main stream approaches are presented. Our protocol outperforms the related work in terms of the average relay node count and distribution, the scalability of the federated WSNs in large-scale applications, and the robustness of the topologies formed.

Towards Augmenting Federated Wireless Sensor Networks

Environmental Monitoring (EM) has witnessed significant improvements in recent years due to the great utility of Wireless Sensor Networks (WSNs). Nevertheless, due to harsh operational conditions in such applications, WSNs often suffer large scale damage in which nodes fail concurrently and the network gets partitioned into disjoint sectors. Thus, reestablishing connectivity between the sectors, via their remaining functional nodes, is of utmost importance in EM; especially in forestry. In this regard, considerable work has been proposed in the literature tackling this problem by deploying Relay Nodes (RNs) aimed at re-establishing connectivity. Although finding the minimum relay count and positions is NP-Hard, efficient heuristic approaches have been anticipated. However, the majority of these approaches ignore the surrounding environment characteristics and the infinite 3-Dimensional (3-D) search space which significantly degrades network performance in practice. Therefore, we propose a 3-D grid-based deployment for relay nodes in which the relays are efficiently placed on grid vertices. We present a novel approach, named FADI, based on a minimum spanning tree construction to re-connect the disjointed WSN sectors. The performance of the proposed approach is validated and assessed through extensive simulations, and comparisons with two main stream approaches are presented. Our protocol outperforms the related work in terms of the average relay node count and distribution, the scalability of the federated WSNs in large scale applications, and the robustness of the topologies formed.