Optimal Relay Node Placement Research Articles

Towards optimal wireless sensor network lifetime in three dimensional terrains using relay placement metaheuristics

In wireless sensor networks, sensor nodes located close to the base station or sink are more susceptible to energy loss, leading to premature disconnection of the network or energy holes. This is due to the fact that all traffic is forwarded towards the sink, increasing the workloads for these closer nodes. One solution for this issue is to shorten the hop distance a sensor’s data has to travel until reaching the sink, by deploying additional relay nodes. This paper considers the problem of optimal relay node placement for maximizing the network lifetime of wireless sensor networks in three-dimensional terrains. We first design a mathematical model of the problem and reformulate it as a mixed-integer programming model to provide a basis for finding lower bound solutions. We divide the problem into two phases and show that the second phase can be solved exactly using an algorithm based on maximum flow and binary search. We then propose a local search algorithm for the first phase, utilizing the exact algorithm to create full solutions. Experimental validation on 3D datasets has been carried out to demonstrate the performance of our algorithms.

Multi Interference Analysis of Two-Way Full-Duplex Decode and Forward Relay System

Abstract A number of new technologies have been designed for cooperative communication due to the advancement in wireless communication. High throughput, data rates and high quality of service are required by current generation like 4G and future generation like 5G wireless communication. MIMO antennas have few limitations like hardware complexity, resource requirements when it uses simplex or half duplex mode of operations. To overcome its drawback like self interference, the outage performance analysis of Two way full duplex (FD) decode and forward relay system is carried out by considering residual self interference caused due to the mode called FD when compared to traditional analysis with perfect self interference cancellation. This article investigated the outage performance of a two way network with decode and forward technique in the presence of multi interferers at the source and or destination terminals. Anyway, it was not taken into account in the previous research papers due to the strong self interference (SI) which occurred from the transmitting antenna (Tx) to the local receiving antenna (Rx). The SI has been highly eliminated using various self interference cancellation (SIC) techniques. To improve the outage performance, further optimal power allocation schemes and optimal relay node placement strategies are proposed. Then, simulation results are shown for symmetrical and asymmetrical situations.

Optimal Placement of CRNs in Manned/ Unmanned Aerial Vehicle Cooperative Engagement System

Aiming at the optimal placement of communication relay nodes (OPCRN) problem in manned/unmanned aerial vehicle cooperative engagement system, this paper designed a kind of fully connected broadband backbone communication topology. Firstly, problem description of OPCRN was given. Secondly, based on problem analysis, the element attributes and decision variables were defined, and a bi-level programming model including physical layer and logical layer was established. Thirdly, a hierarchical artificial bee colony (HABC) algorithm was adopted to solve the model. Finally, multiple sets of simulation experiments were carried out to prove the effectiveness and superiority of the algorithm.

Optimal Relay Node Placement and Flow Allocation in Underwater Acoustic Sensor Networks

In recent years, underwater acoustic sensor networks (UASNs) have attracted widespread attention in academia. Prolonging the network lifetime is a crucial issue for UASNs. Compared with traditional wireless sensor networks (WSNs), stringent energy becomes more critical in UASNs because the battery equipped at sensor nodes has the limited amount of energy and it is much more difficult to replace or recharge in underwater circumstance. This fact motivates us to pursue the solutions to reduce power consumption by using relay nodes and flow allocation mechanism in order to extend the network lifetime. In this paper, the issues of relay node placement and the flow allocation have been considered as a joint problem and are formulated into an integer nonlinear programming problem, which is node placement-hard in general. To solve the problem efficiently, this paper proposes a novel heuristic scheme for UASNs, which works based on a 3-D architecture. The proposed scheme consists of three algorithms, named as Alternative Flow and Relay-node Adjustment as a whole. Extensive simulation experiments demonstrate that the proposed scheme offers a simple yet attractive solution to the problem.

Outage Analysis of the Full-Duplex Decode-and-Forward Two-Way Relay System

Contrary to the traditional theoretical analysis with perfect self-interference cancellation, this paper studies the outage performance of a full-duplex (FD) decode-and-forward two-way relay system with the consideration of the residual self-interference incurred by the FD mode. The exact closed-form outage probability expressions are derived in this paper. In addition, the asymptotic outage performance is investigated when the transmit powers increase to infinity, and the result demonstrates that the outage probabilities monotonically increase and finally converge to 1 as the transmit power exceeds a certain threshold. Furthermore, optimal power allocation schemes and optimal relay node placement strategies are then proposed to improve the outage performance. Finally, simulation results are conducted to verify the accuracy of the theoretical analysis.

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.

Outage Performance of the Full-Duplex Two-Way DF Relay System Under Imperfect CSI

Contrary to the most existing works about the full-duplex (FD) relaying with perfect channel state information (CSI), this paper studies the outage performance of the two-way FD decode-and-forward relay network under the joint effects of the residual self-interference and imperfect CSI. We first derive the exact closed-form expressions of the system outage probability, based on which we obtain the outage probability under the perfect self-interference cancellation to investigate the impacts of the imperfect CSI on the system performance. In addition, to gain more insights about the imperfect CSI, we analyze the optimal power allocation scheme and an optimal relay node placement strategy, which minimize the system outage probability. The results reveal that the imperfect CSI will only affect the optimal power allocation, and the optimal relay node placement is related to the power ratio between the user nodes. Finally, analytical evaluations are performed to verify the theoretical results, and Monte Carlo simulations guarantee the correctness of the analytical evaluations.

Optimal placement of relay nodes in wireless sensor network using artificial bee colony algorithm

Deploying sensor nodes randomly most of the time generates initial communication hole even in highly dense networks. These communication holes cannot be totally eliminated even when the deployment is done in a structured manner. In either case, the resulting inter-node distances may degrade the performance of the network. This paper proposes an enhanced deployment algorithm based on Artificial Bee Colony (ABC). The ABC-based deployment is guaranteed to extend the lifetime by optimizing the network parameters and constraining the total number of deployed relays. Simulations validate the effectiveness of the proposed strategy under different cases of problem complexity. Results show that the proposed approach improves the network lifetime considerably when compared to solutions reported in the literature such as Shortest Path 3-D grid Deployment (SP3D) algorithm.

Relay node placement to heal partitioned wireless sensor networks

The wireless sensor networks deployed in hostile environments suffer from a high rate of node failures. Such failures may convert a fully-connected sensor network into multiple disjoint sub-networks, leading to the network partition problem. The placement of relay nodes is the only way to restore the lost connectivity because these devices, compared to the sensor nodes, have a higher energy backup, with a longer communication range. In this paper, a new solution is proposed to heal the network partition problem in the wireless sensor network. The solution is based on a zero gradient point inside the convex hull polygon. The proposed solution is compared with various naive approaches, along with existing state-of-the-art solutions, that is, the Spider Web-1C heuristic and Steiner-minimum-tree based optimal relay node placement algorithm. The simulation experiment results confirm the effectiveness of our proposed approach.

Restoration Strategy Based on Optimal Relay Node Placement in Wireless Sensor Networks

In wireless sensor networks (WSNs), connecting disjoint segments is significant for network restoration, especially in some mission critical applications. However, the variability of distances between disjoint segments has tremendous influence on relay nodes deployment. In fact, finding the optimal solution for connecting disjoint segments in terms of the number and positions of relay nodes is NP-hard. To address this issue, plenty of heuristics, such as STP-MSP (Cheng et al., 2008), MST-1 tRN (Lloyd et al., 2007), and CORP (Lee and Younis, 2010) are deeply pursued. In this paper, we propose a distributed restoration algorithm based on optimal relay node placement (simply, ORNP). It aims at federating separated segments by populating the minimum number of relay nodes in a WSN that has suffered a significant damage. In addition, both of complexity and upper bound of the relay count for ORNP are explored. The simulation results show that ORNP performs better than STP-MSP, MST-1 tRN, and CORP in terms of relay count and the connectivity of resulting topology.

Optimal relay node placement in delay constrained wireless sensor network design

The Delay Constrained Relay Node Placement Problem (DCRNPP) frequently arises in the Wireless Sensor Network (WSN) design. In WSN, Sensor Nodes are placed across a target geographical region to detect relevant signals. These signals are communicated to a central location, known as the Base Station, for further processing. The DCRNPP aims to place the minimum number of additional Relay Nodes at a subset of Candidate Relay Node locations in such a manner that signals from various Sensor Nodes can be communicated to the Base Station within a pre-specified delay bound. In this paper, we study the structure of the projection polyhedron of the problem and develop valid inequalities in form of the node-cut inequalities. We also derive conditions under which these inequalities are facet defining for the projection polyhedron. We formulate a branch-and-cut algorithm, based upon the projection formulation, to solve DCRNPP optimally. A Lagrangian relaxation based heuristic is used to generate a good initial solution for the problem that is used as an initial incumbent solution in the branch-and-cut approach. Computational results are reported on several randomly generated instances to demonstrate the efficacy of the proposed algorithm.

Performance of vehicular delay‐tolerant networks with relay nodes

AbstractDelay‐tolerant networking (DTN) is an architecture to enable data communications between isolated or remote regions, where long delays and intermittent connectivity can be tolerated. An emerging class of DTN, called Vehicular DTNs (VDTN), exploits transportation systems as the transport layer to transfer data. In these networks, vehicles (e.g., buses, boats, and trains) act as mobile nodes and carry data messages around. Mobile nodes can exchange data messages using devices called relay nodes. Relay nodes, placed in strategic positions along vehicle routes, have the capability to download, store, and upload the data messages from/to the mobile nodes. An important issue in VDTN is the optimal placement of the relay nodes such that delay‐tolerant connectivity in VDTN is ensured at minimum cost. In this paper we show that the problem of optimal relay node placement is an NP‐hard problem. Other contributions of this paper are the formulation of the relay node placement problem using integer linear programming (ILP) formulation and the proposal of heuristic algorithms solving the optimization problem. Using simulation results, we compare the performance of each algorithm under different network constraints, such as node storage capability and network topology. Copyright © 2009 John Wiley & Sons, Ltd.

Relay node placement with energy and buffer constraints in wireless sensor networks using mobile data collector

Higher-powered relay nodes, used as cluster heads in hierarchical sensor networks, can improve network performances. Most existing relay node placement strategies consider only stationary nodes, where data are routed to the base station(s), possibly using multiple hops. We consider a relay node based network, where a Mobile Data Collector (MDC) collects data from each relay node and delivers the collected data to the base station. This reduces the energy dissipation of the relay nodes by relieving them of the burden of transmitting data over longer distances. The issue is to find the minimum number of relay nodes, along with their locations, such that network coverage and lifetime requirements are satisfied. We present an integrated Integer Linear Program (ILP) formulation that determines an optimal relay node placement scheme, which ensures that there is no data loss due to buffer overflow and the energy dissipation does not exceed a specified level.

On optimal placement of relay nodes for reliable connectivity in wireless sensor networks

The paper addresses the relay node placement problem in two-tiered wireless sensor networks. Given a set of sensor nodes in Euclidean plane, our objective is to place minimum number of relay nodes to forward data packets from sensor nodes to the sink, such that: 1) the network is connected, 2) the network is 2-connected. For case one, we propose a (6+e)-approximation algorithm for any e > 0 with polynomial running time when e is fixed. For case two, we propose two approximation algorithms with (24+e) and (6/T+12+e), respectively, where T is the ratio of the number of relay nodes placed in case one to the number of sensors. We further extend the results to the cases where communication radiuses of sensor nodes and relay nodes are different from each other.