Towards a Mobility Metric for Comparable & Reproducible Results in Ad Hoc Networks Research (poster abstract)

The performance of a mobile ad hoc network depends on its ability to adapt to changes in the
network topology. It is therefore important to understand the relation between node mobility and
topology dynamics. While the input parameters of a mobility model allow for generating different
simulation scenarios (e.g., by selecting the speed, pause time, system area, and number of
nodes), the relation to the actually generated degree of topology dynamics is usually not
immediate. Thus, a translation of the mobility model to the resulting topology dynamics is
required. A natural way to do this is to introduce the topology change rate (TCR), defined as
the number of link changes per time unit as observed by a single node. If we measure the
network performance versus the TCR instead of versus ‘incidental’ input parameters of a mobility
model, a higher level of abstraction of the results will be achieved, and the reproducability
and comparability of the results will be enhanced. This short paper derives in an analytical
manner the TCR in a scenario where nodes move according to the random waypoint (RWP)
model [5], being the most heavily used mobility model in reseach on ad hoc networks. ... mehr
Recent insights into RWP mobility have shown some unexpected behavior, e.g., with respect
to the spatial node distribution [2] and the average velocity over time [8]. These results do
not mean that RWP as a mobility model is ‘invalid’, but show the importance of proper use
due to thorough understanding of the model. This contribution now provides the link between
RWP mobility and the corresponding TCR. We

• derive in an analytical manner the TCR as observed by a static node located at the center of a circular area in which mobile nodes move according to RWP model.

• show via simulation that our expression takes over to the TCR as observed by a moving node and to other shapes of the system area.

We see this result as a step towards establishing TCR as a ‘generic’ mobility metric that can help to improve the reproducability and comparability of simulation results on ad hoc networking.