  In this paper we study the dynamic aspects of the coverage of a mobile sensor
network resulting from continuous movement of sensors. As sensors move around,
initially uncovered locations are likely to be covered at a later time. A
larger area is covered as time continues, and intruders that might never be
detected in a stationary sensor network can now be detected by moving sensors.
However, this improvement in coverage is achieved at the cost that a location
is covered only part of the time, alternating between covered and not covered.
We characterize area coverage at specific time instants and during time
intervals, as well as the time durations that a location is covered and
uncovered. We further characterize the time it takes to detect a randomly
located intruder. For mobile intruders, we take a game theoretic approach and
derive optimal mobility strategies for both sensors and intruders. Our results
show that sensor mobility brings about unique dynamic coverage properties not
present in a stationary sensor network, and that mobility can be exploited to
compensate for the lack of sensors to improve coverage.
