Linear wireless sensor networks: Classification and applications

Abstract

Wireless sensor networks (WSNs) constitute a rapidly growing technology, taking advantage of advances in electronic miniaturization that consume less energy for both processing and communication. The cost of these devices is also constantly decreasing, making it possible to use a large number of sensor devices in a wide array of commercial, environmental, military, and health care fields. Many of these applications involve placing the sensors in a linear form, making a special class of these networks which we define as a Linear Sensor Network (LSN). In this paper, the concept of LSNs is expanded, along with a set of applications for which this type of network is appropriate. In addition, motivation for designing specialized protocol is provided that explores linearity of the network to increase the communication efficiency, reliability, fault tolerance, energy savings and network lifetime. Furthermore, classification of LSNs from both topological and hierarchical points of views, is presented and various characteristics, research challenges and underlying opportunities are discussed. Simulation experiments are also presented to compare the performance and reliability of LSNs.

Introduction

The advent of technology in computing and electronics evolving innovation of tiny wireless sensors has opened an unprecedented opportunity for a wide array of real-time applications. In recent years, wireless sensor networks (WSNs) have been emerging as a new suitable tool for a spectrum of new applications. These tiny sensor nodes are low cost, low power, easily deployable, and are self-organizing. They are usually capable of doing limited local processing. However, information collected from a large number of such nodes at a central location known as base stations (BSs) or sink nodes, before reaching a network control center (NCC) enables detailed representation of a given physical environment. Thus, a WSN can be described as a collection of sensor nodes which collaborate to arrive at some specific decision. Unlike traditional networks, a WSN depend on dense deployment and adequate co-ordination of data transfer to a BS. These unique characteristics make it very useful. WSNs were initially introduced for defense applications such as target detection, surveillance of enemy activities in a battlefield environment and counterterrorism. However, their advantages over traditional networks have resulted in many other potential civilian applications that range from infrastructure security to industrial control. Some examples are environment and habitat monitoring, health applications, home automation, traffic control, etc. Another possible example is protecting and monitoring a large pipeline system.

Research in the field of WSNs is relatively active and involves a number of interrelated issues, including efficient routing protocols (Akkaya and Younis, 2005, Akkaya and Younis, 2003, Akyildiz et al., 2002, Chong and Kumar, 2003, He et al., 2003, Schurgers and Srivastava, 2001, Soharabi and Pottie, 2000), QoS support (Jawhar and Wu, 2005), security (Fernandez et al., 2005), and middleware (Hadim et al., 2006). Most of these are investigated under the assumption that the network used for sensors does not have any infrastructure support. Fortunately, WSN needed for a monitoring linear infrastructures ought to be a structured network in which all sensor nodes are to be placed in a line. This characteristic can be utilized for enhancing the communication sequencing and reliability of the network.

We define LSNs as a new category of WSNs where the nodes are placed in a strictly linear or semi-linear form. A WSN is considered linear if one of the following conditions are true: (1) if all the nodes are aligned on a straight line, strictly forming a line, or thin LSN; (2) if all of the nodes exist between two parallel lines that extend for a relatively long distance as compared to their transmitting range and the distance separating them constitute a semi-linear or thick LSN. We introduced a general concept of LSNs along with some specialized routing protocols and addressing scheme in Jawhar et al., 2007, Jawhar et al., 2009.

The alignment of sensor nodes in a linear form can be used in many applications such as monitoring and surveillance of international boundaries for illegal crossing, or smuggling activities, monitoring of roads, or long pipelines carrying oil, gas and water resources, river environmental monitoring, etc. (Jawhar et al., 2007). This architecture utilizes a linear structure to address communication sequencing, reliability, and security problems. The objective of the design is to reduce the installation and maintenance costs, increase the network reliability and fault tolerance, enhance the battery life for sensors, and reduce end-to-end communication delay for better quality of service (QoS) support of sensitive data.

The contributions of this paper can be summarized as follows:

• Identify and define LSNs, which constitute special class of WSNs.

• Present sample applications of LSNs.

• Outline the reasons and motivation behind the need for new architectures and protocols for LSNs.

• Distinguish different possible control classes that indicate different types of LSNs from a topological and hierarchical points of views.

• Present a case study which illustrates a design with associated protocols that increase the efficiency and robustness of routing.

The rest of the paper is organized as follows. Section 2 provides an overview of related work in this field. Section 3 introduces some important applications for wireless LSNs. Section 4 discusses the reasons why new architectures and protocols are desirable for LSNs. Section 5 provides a topological and hierarchical classification of LSNs. Sections 6 offers a basic algorithm for routing messages in LSNs and Section 7 presents simulation experiments, which evaluate its performance under various network conditions. The last section concludes the paper and provides future directions for further research.