Wireless Sensor Networks: Active Mobility Models
In the previous chapter, we described models of passive mobility in WSNs. This chapter is devoted to the other type of possible mobility in sensor networks, that is, active mobility in which the mobile entity (typically, the sensor node, or the sink) can decide the direction, speed, and time of movement. Active mobility can be exploited in WSNs for different purposes, for instance, to improve sensing coverage after an initial, random sensor node deployment, or to optimize the data collection task. The former is an example of sensor node active mobility, while the latter is an example of sink node active mobility.
From a technological viewpoint, both sensor and sink node active mobility can be realized at reasonable costs with current technology. The feasibility and cost-effectiveness of sensor node mobility were first shown with the introduction of the Robomote platform (Sibley et al. 2002); more recently, sensor nodes have been mounted on cheap mobile robots such as the Roomba vacuum cleaner and Lego Mindstorm toy robots. Sink mobility can be realized in a similar way, possibly using more powerful robots, which is economically feasible given the limited number of sink nodes, or human operators.
In contrast to most types of mobility considered so far in this book, active mobility in WSNs is seen as a means of optimizing certain network-level properties, such as coverage, energy consumption, and so on. Given this, active ...