longest time, or by bus through the longest path but with the shortest time. Obviously,
RWM fails to model this case, but our GMM can.
3.3.2 Resource Aware Movement
As mentioned before, in the general mobility model there might be potentially many
different paths between any two consecutive stops. Define PATH(I., -- (0),1~ 4. (J1 1))
as node i's path set which is the concatenation of all the paths 1., -- (j J., -- (j +t 1). In this
dissertation, we are interested in finding the optimal path sets for all the nodes such that
the total energy consumption for communications by all the nodes during the observation
period T is minimized (the objective function), while all the ordered lists of visited loca-
tions and the corresponding time instances should not be violated (the constraints). To help
better understand the importance of this problem, we utilize the movement of a single node
between two consecutive stops as an example. As shown in Fig. 3-1, suppose an B-node
A should move from the current location 1 to the next location 2. It can choose the shortest
straight path (the dashed one) as it does in the random waypoint model. However, con-
sidering that node A may forward or generate packets destined for other nodes during the
movement process, the shortest straight path is not necessarily the best one for achieving
the system-wide energy efficiency. Instead, the dotted and solid paths are much better can-
didates through which node A can take advantage of more P-nodes by forwarding to the
encountered P-nodes the packets destined for other nodes and letting them finish the rest of
the task. Due to this reason, we call this problem the resource-aware movement problem in
that nodes now are moving with the system-wide resource (energy) consumption in mind
instead of moving blindly as before.
The general resource-aware movement problem itself is far too complicated to be
solvable. To render it tractable, we make some approximation and decouple it into two
relatively simpler subproblems: the Waterhunter Movement problem and the Firehunter
Movement problem. In the former, we assume that only B-nodes are capable of moving