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

8.1 INTRODUCTION

In sensor and mobile actuator networks, actuators operate autonomously with no fixed infrastructure or centralized control. They determine their own location by the use of global positioning system (GPS) or some other type of positioning system, and register with location service. Location service tracks actuators' location and enables sensors to discover actuators so that geographic routing or other position-based algorithms can be applied. As an active subject, location service has been studied for over a decade in wireless ad hoc networks. Existing solutions can be directly applied to emerging sensor and actuator networks.

Location service has two ingredients: location update and actuator search. After an actuator leaves its current position, it needs to update its location in the network so that others can find it and keep routing packets to it. There exist two basic approaches for routing toward an actuator. In the first approach, when a sensor wants to route a packet by a geographic routing protocol such as Greedy-Face-Greedy (GFG) (Bose et al., 1999) to an actuator, it first searches for that actuator's latest location. In most cases, the search ends up at destination location, followed by report from destination back to the source, containing the exact position of destination. Since the position of the source can be included in the search message, this report can be carried by a georouting task. Alternatively, the source may use currently available and ...