On the Invariance of Spatial Node Density for Realistic Mobility Modeling

Abstract

In this paper we show that human mobility exhibits "persistent" behavior in terms of the spatial density distribution of the mobile nodes over time. Using real mobility traces, we observe that the original non-homogeneous node spatial density distribution, where some regions may be quite dense while others may be completely deserted, is maintained at different instants of time. We also show that mobility models that select the next node position based on the position of other nodes, a la "preferential attachment", do not preserve the original spatial node density distribution and lead to behavior similar to random mobility as exemplified by the Random Waypoint model. To the best of our knowledge, this is the first time that these phenomena have been reported. Based on these observations, we propose a simple mobility model that preserves the desired spatial density distribution. Moreover, when simulating the operation of a network moving according to the proposed model, we found that performance results expressed by a number of network metrics also match closely results obtained under mobility governed by real traces. We also compare our results to models whose steady-state do not preserve the original non-homogeneous density distribution and show that network performance under such regimes deviates from performance under real trace mobility.

Modeling spatial node density in waypoint mobility

“…More specifically, our model shows that, at steady state, the original spatial node density distribution is not preserved and exhibits behavior similar to random mobility a la Random Waypoint regime. This behavior has been observed empirically in [7], where we show that, instead, real human mobility exhibits "persistent" density heterogeneity.…”

“…The main goal of these preferential attachment based approaches is to try to maintain the non-homogeneity of the spatial node density observed in real live mobility traces, also maintaining the clusters of nodes naturally formed in real applications. Our model can be used to study the steadystate of such mobility regimes to show how the long run, they are very similar to the RWP model in terms of node density distribution [7].…”

MANET protocol simulations considered harmful: the case for benchmarking

“…For these kinds of situations, we urge readers to reference research such as [13] which analyzes and compares the use of WLAN, GPS, and synthetic traces in the context of producing realistic human mobility models.…”

Saga

“…In our previous work, we have shown that using the preferential attachment principle to model human mobility leads to undesirable long-term behavior [15]. More specifically, preferential attachment based mobility regimes do not preserve the original spatial node density distribution and lead to steady-state behavior similar to random mobility as exemplified by the Random Waypoint model.…”

“…More specifically, preferential attachment based mobility regimes do not preserve the original spatial node density distribution and lead to steady-state behavior similar to random mobility as exemplified by the Random Waypoint model. Instead, real human mobility exhibits persistent density heterogeneity as shown in [15].…”