MANET performance in urban environments

This paper investigates the affect of pathloss and mobility in an urban environment on MANETs. Specifically, this investigation employs mobility and pathloss that resembles the mobility of pedestrians and pathloss in urban environments. We study the behavior of MANETs on a university campus and in the Paddington area of London England. The model utilizes ray tracing to provide realistic radio wave propagation. A constrained random waypoint mobility is used where mobile nodes move from building to building (along sidewalks and through hallways) and then remain in a randomly selected office for a random pause time. The behavior of MANETs in these environments is compared to the behavior provided by the popular random waypoint and free-space models. Several observations are made. These include that the random waypoint/free-space model greatly over estimates the connectivity of a network in an urban environment. Also, it is shown that the distribution of the degree of a node (i.e., the number nodes that a node can directly communicate with) in the urban environment is bimodal and that there are more nodes with large degree as well as more nodes with smaller degree than predicted by free-space pathloss. The dynamics of links is investigated and it is shown that the heterogeneity of the urban environment produces complicated behavior. Lastly, the behavior of DSR in the free-space and urban environments is compared. It is shown that the urban environment is significantly different from the free-space model.