Discovering Variables that Affect MANET Protocol Performance

Mobile Ad Hoc Networks (MANETs) are usually studied through simulation. Network simulators allow users, in principle, to set values for several hundred variables. A few of these variables, including node speed, node pause time, and packet size, receive much of the attention in MANET simulation studies, because their values are generally believed to have an important effect on simulation results (e.g., delivery ratio). There are, however, a number of variables that are less discussed, but which have a substantially greater effect on simulation results than those more commonly considered. Given a typical simulation scenario, we demonstrate that variables such as the number of sources and random versus fixed destinations, which have received comparatively little attention in the literature, have a substantially greater impact on delivery ratio than do variables such as node speed and pause time, which have received significant attention in the literature. Failure to consider the values of these variables in simulation studies can result in misleading conclusions regarding the performance of routing protocols. We conclude that before investigators draw firm conclusions about the performance of a MANET routing protocol, they should examine the effects of a wider variety of variables than has generally been the practice.