Chapter 20. Wireless Sensor Networks

Self-organizing sensor networks hold the potential to revolutionize many segments of public security, environmental monitoring, and manufacturing. Sensors can be networked to form a network to enhance sensing capability. Like a computer network, a sensor network has a packet with a header flowing in a network of nodes (sensor nodes). This chapter presents the architectures and protocols of such networks, discussing the following topics:

• Sensor networks and protocol structures

• Communication energy model

• Clustering protocols

• Routing protocols

• Case study: Simulation of a sensor network

• Other related technologies

We begin with an overview of sensor networks and explain some popular applications. We also provide an overview of a protocol stack for sensor networks and explain how the power factor distinguishes the routing protocols of sensor networks from those of computer networks. The protocol stack combines power efficiency and least-cost- path routing. Networking protocols and power efficientcy are integrated through the wireless medium, and cooperative efforts of sensor nodes are promoted.

Clustering protocols in sensor networks specify the topology of the hierarchical network partitioned into nonoverlapping clusters of sensor nodes. Typically, a robust clustering technique is essential for self-organizing sensor networks. Two clustering protocols are the Low-Energy Adaptive Clustering Hierarchy (LEACH) algorithm and the Decentralized Energy-Efficient Cluster Propagation (DEEP) protocol. After well-distributed cluster heads and clusters have been established in a network, energy-conscious routing is essential in order to set communication routes among cluster heads.

This last chapter also offers a detailed numerical case-study on the implementation of a clustering protocol, as well as a discussion of ZigBee technology , which is based on the IEEE 802.15.4 standard. This technology uses low-power nodes and is a well-known low-power standard.