A Study of Dispersion-based Measurement Methods in IEEE 802.11 Ad-hoc Networks

In this article we discuss how dispersionbased measurements are affected by multiple-access networks, such as IEEE 802.11-based ad-hoc networks. We study four topics: variable link capacity, movement of wireless nodes, loss rate and timing issues. We show by simulations that the link capacity in a wireless topology is changing due to cross traffic generated from nodes using the same radio frequency channel. Further, we address the problem of moving nodes. Moving nodes may cause route changes during a dispersion-based measurement session. Since all dispersion-based measurement methods are running during a time interval, moving nodes will cause problems. We extend the term available bandwidth to cope with losses in shared medium access networks. Losses will lower the available bandwidth that can be used by applications. Finally we study the problem of time jitter induced between successive probe packets by multiple-access networks.