On the effect of radio channel propagation models to the ad hoc network performance

Abstract

In this paper, we study the behavior of ad hoc network performance under different propagation models. Ad hoc networks are often studied with unrealistic cut propagation models, where the propagating signal is completely cut to some predefined distance. The worst drawback in this kind modeling is that it fails to include the effect of multiple access interference (MAI). Since cut propagation model is taken as a point of comparison, free space propagation model will provide the simplest enhancement to enable realistic MAI calculation. In addition, we also use a forest propagation loss model, which provides a more realistic environment for military scenarios. We study the performance in two cases: nodes equipped with our BCCA (bi-code channel access) and BC-MAC (bi-code MAC), and nodes with IEEE 802.11. The study shows that there are significant differences in the absolute performance between scenarios with different propagation models. This clearly shows the importance of lower layer modeling, although the focus would be on the upper layer performance (e.g., on the application layer quality of service (QoS)). The study also shows that BC-MAC outperforms IEEE 802.11 regardless of the propagation modeling. Despite the fact that the ranking of the performance between BC-MAC and 802.11 was unchanged in this study, the great differences in the absolute performance questions the generality of the results obtained with simplified lower layer models. This should be taken into consideration especially in military related studies, where the focus often is in the absolute performance of a certain scenario and not only in the relative difference between some methods