Relay Node Placement in Wireless Sensor Networks With Respect to Delay and Reliability Requirements

Abstract

Wireless sensor networks are gradually employed in many applications that require reliable and real-time data transmission. As hop count is an important factor affecting end-toend delay and reliability, we investigate the hop constrained relay node placement (HCRNP) problem in this paper. First, to achieve connectivity requirement, we study the connected HCRNP problem. Then, to design survivable network topologies against node failures, we study the 2-connected HCRNP problem. Correspondingly, two polynomial-time algorithms: cover-based 1-connected node placement (C1NP) and cover-based 2-connected node placement (C2NP) are proposed, respectively, to address the above two problems. Through rigorous analysis, we show that 1) C1NP has an approximation ratio better than existing algorithms for the connected HCRNP problem (i.e., O(1) for special settings and O(ln n) for arbitrary settings, where n is the number of SNs) and 2) C2NP is the first algorithm that can provide an explicit performance guarantee for the 2-connected HCRNP problem, i.e., whenever C2NP finds a feasible solution, the ratio of this solution to the optimal solution is guaranteed to be O(ln n). Finally, we verify the effectiveness of the proposed algorithms through extensive simulations. Index Terms-Approximation algorithm, quality of service, relay node placement (RNP), set cover, wireless sensor networks (WSNs). I. INTRODUCTION W IRELESS sensor networks (WSNs) have been employed in various applications, such as battlefield surveillance, environmental monitoring, industrial automation, and scientific observation. Typically, WSNs are composed of spatially distributed sensor nodes (SNs) gathering certain information and at least one sink collecting the information from SNs. Normally, an SN has a very limited communication range mainly due to its constrained power supply and antenna height [1]-[4]. As a result, some additional nodes are placed to build the network connectivity, and these nodes function as relay nodes Manuscript

Energy-Efficiency of Selective Relaying in a MIMO Network-Coded Cooperative System

“…3. In this figure, ''Simulation'' is the result obtained by means of Monte Carlos simulations, ''Exact'' is the EE obtained from (13) by means of the exact outage probability from (4), while ''Approximation'' refers to the EE obtained also from (13) but adopting the high-SNR approximation from Corollary 1. Even though MRC needs less transmit power to achieve the predefined target outage probability, the consumption of the receiver circuitry compromises its EE when compared to SC.…”

“…However, the reliability is also increased as presented in (8) and (9), such that the required transmit power to achieve a target outage probability is reduced. Thus, one could expect that there is an optimal maximum number of selected relays L that minimizes (13), as discussed in what follows.…”

“…Since cooperation usually relies on multiple orthogonal channels, relay selection protocols have been proposed to improve spectral efficiency [12], [13], being recently considered also in the scope of internet-of-things (IoT) [14], [15] and 5G [16], [17]. From a reliability perspective, it is shown in [8] that multiple relay selection (MRS) improves the diversity order of a NCC network.…”

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“…The number of hops is also an important factor affecting the end-to-end delay and reliability. The core of the literature [14] is the placement of relay nodes with limited hops for 1 connection and the placement of relay nodes with limited hops for 2 connections. The simulation results show that the complexity of the proposed 1-connected placement algorithm is lower than existing 1-connected placement algorithm, the proposed 2-connected relay node placement problem can provide clear performance guarantee.…”

Method for Handling Massive IoT Traffic in 5G Networks

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