A Feedback Based Solution to Emulate Hidden Terminals in Wireless Networks

Mobile wireless emulation allows the test of real applications and transport protocols over a wired network mimicking the behavior of a mobile wireless network (nodes mobility, radio signal propagation and specific communication protocols). Two-stage IP-level network emulation consists in using a dedicated offline simulation stage to compute an IPlevel emulation scenario, which is played subsequently in the emulation stage. While this type of emulation allows the use of accurate computation models together with a large number of nodes, it currently does not allow to deal with dynamic changes of the real traffic. This lack of reactivity makes it impossible to emulate specific wireless behaviors such as hidden terminals in a realistic way. In this paper we address the need to take into account the real traffic during the emulation stage and we introduce a feedback mechanism. During the simulation several emulation scenarios are computed, each scenario corresponding to alternative traffic conditions related to e.g. occurrence or not of hidden terminals. During the emulation stage, the traffic is observed and the currently played emulation scenario can be changed according to specific network conditions. We propose a solution based on multiple scenarios generation, traffic observers and a feedback mechanism to add a trafficbased dynamic behavior to a two-stage emulation platform. The solution will be illustrated with a simple experiment based on hidden terminals.