Modeling and Analysis of Generalized Random Mobility Models for Wireless Ad Hoc Networks

Book excerpt: In wireless ad hoc networks, the ability to analytically characterize the long-run properties of the mobility profiles of communicating terminals plays a key role in understanding the fundamental network QoS measures such as throughput per source to destination pair, probability of successful transmission, connectivity, etc. Consequently, mobility models that are general enough to capture the major characteristics of a realistic movement profile, and yet are simple enough to mathematically formulate its long-run behavior, are highly crucial for the analytical or simulation based performance modeling of ad hoc networks. In this dissertation, we propose a generalized random mobility model capable of capturing several realistic mobility scenarios and give a mathematical framework for its exact analysis over one-dimensional and two-dimensional mobility terrains. The model provides the flexibility to capture hotspots where mobiles accumulate with higher probability and spend more time. The selection process of hotspots is random and correlations between the consecutive hotspot decisions can be successfully modeled. Furthermore, the times spent at the destinations can be dependent on the location of destination point, the speed of movement can be a function of distance that is being traveled, and the acceleration characteristics of vehicles can be incorporated into the model. Our solution framework formulates the model as a semi-Markov process using a special discretization technique. We provided long-run location and speed distributions by closed-form expressions for one-dimensional regions (e.g., a highway). From the utilization of the framework to random waypoint mobility model, we derive an approximation to the spatial distribution of terminals over rectangular regions. We validate the accuracy of this approximation via simulation, and by comparing the marginals with proven results for one-dimensional regions point out that it is insensitive to the proportion between dimensions of the terrain. In addition, we establish an example that demonstrates the applicability of the results derived to a scenario where mobile terminals are restricted to move on predefined paths.