Scalable Emulation of Dynamic Multi-hop Topologies

Communication in wireless networks is affected by uncontrollable disturbances in the channel. Effects of these disturbances are exacerbated in networks with dynamic topologies and multiple hops. Lack of control of the channel complicates testing of such networks as test conditions are hard, or impossible, to reproduce. This paper describes how to create reproducible test conditions for these networks by emulating the wireless links. Emulation is performed by a topology emulator to which end-nodes are connected using wired links. In real-time, the emulator imposes packet drops and delays onto traffic between end-nodes. The imposed properties are based on simulations of node mobility, loss and delay models. Evaluation confirms that the testbed is capable of emulating links in real time and transparent to upper layer protocols. Additionally, the impact on test results is evaluated, such as increased network delays and reduction of bandwidth when loading the emulator. Finally, an outlook on advancing capabilities and how to integrate such in the emulator is presented.