Wireless Testbed Bonsai

This paper focuses on the spatial scaling of wireless network behaviors, ranging from low-level signals to network protocol executions to high-level application behaviors. This task is complicated as wireless channels exhibit complex fading patterns across space and time. And there have been several instances of "phase transitions", where wireless network protocols and applications that perform well at small scales fail to do so at higher scales. Presently, experimentation with wireless testbeds is preferred to simulations for obtaining high fidelity testing, but at the same time experimentation is also known to be more inconvenient and expensive, especially for large scale networks. We therefore investigate the ability of high fidelity spatial downscaling of such networks, for making more convenient the testing and predictability of designs for large scale networks. Specifically, we present necessary and sufficient conditions for high fidelity scaling of wireless networks and evaluate the feasibility of scaling an indoor multihop IEEE 802.11b network by reducing the separation between the nodes by a constant factor. Our validation is in terms of experimental studies of down-scaling performed in the Kansei testbed at Ohio State University, and compare the performance at the physical, link, and messaging/dissemination layers before and after scaling.