Section 20.7. Summary

20.7. Summary

This last chapter focused on wireless sensor networks. Some applications of sensor networks are target tracking, environmental monitoring, system control, and chemical or biological detection.

The protocol stack for sensor networks concerned with power factor. The sensor network protocol stack combines two features: power-efficiency and least-cost- path routing. Thus, the protocol architecture integrates networking protocols and power efficiency through the wireless medium and promotes cooperative efforts among sensor nodes. The protocol stack consists of the physical, data-link, network, transport, and application layers , power-management, mobility-management, and task-management planes. The internal structure of an intelligent sensor node consists of three units for sensing, processing, and storage, respectively, and communications capabilities.

An energy model for a transceiver of a node can be developed. The energy consumption, E , for all components of a transceiver in watts can be modeled by E = + ·‰d ⁿ , where is the distance-independent term that accounts for the overhead of the radio electronics and digital processing, and ·‰d ⁿ is the distance-dependent term in which · represents the amplifier inefficiency factor, ‰ is the free-space path loss, and d is the distance.

Two clustering protocols in sensor networks are the Low-Energy Adaptive Clustering Hierarchy (LEACH) algorithm and the Decentralized Energy-Efficient Cluster Propagation (DEEP) protocol. DEEP is based on the idea of controlling the geographical dimensions of clusters and the distribution of cluster heads. Because of the balanced load among cluster heads, there is no need for frequent re-clustering, but after current cluster heads are out of energy, the protocol can rotate the cluster-head position among all the sensor nodes. Also, the identical distance between a pair of neighboring cluster heads leads to the ease of route set-up deployment. After establishing well-distributed cluster heads and clusters in a network, energy-conscious routing is essential in order to set communication routes among cluster heads. ZigBee technology , which is based on the IEEE 802.15.4 standard, is a related technology that uses low-power nodes.