Wireless Sensor and Actuator Networks: Algorithms and Protocols for Scalable Coordination and Data Communication

1.1 WIRELESS SENSORS

We will elaborate first on wireless sensors; then on wireless sensor networks (WSNs) (with a single sink), their properties, models, and application types. Afterwards, we will add actuators to the model and discuss various combinations of sensors and actuators that can form a heterogeneous network with different levels of complexity.

Recent technological advances have enabled the development of small-sized (a few cubic centimeters), low-cost, low-power, and multifunctional sensor devices. There are different types of sensors. Sensors are normally specialized, but sometimes a few capabilities may be available in a single sensor. They may measure distance, direction, speed, humidity, wind speed, soil makeup, temperature, chemical composition, light, vibration, motion, seismic activity, acoustic properties, strain, torque, load, pressure, and so on.

Traditionally, sensors are attached to the environment and their measurements are sent to a base station (BS) with wired communication. There exists a large body of knowledge on such models and applications of sensors which have been studied by a huge community of researchers. During the last decade, a new vision of sensor nodes as autonomous devices with integrated sensing, processing, and communication capabilities has emerged. Attaching antenna for receiving signals and a transmitter enables wireless communication of sensors. Sensors also have a small processor and a small memory for coding and decoding signals, ...