A Case Study of UTMesh: Design and Impact of Real World Experiments with Wi-Fi and Bluetooth Devices

This paper presents UTMesh -- a test bed for wireless mesh networking and delay (or disruption) tolerant networking developed in the University of Tokyo. We have customized 51 embedded Linux computers for experiment-oriented use cases, and let them powered by rechargeable batteries in order to flexibly deploy everywhere depending on the experiment scenarios. This paper summarizes the requirements for our test bed design, identifies an operation model of real world experiments, and presents a sample experiment and its results. UTMesh allows many types of real world experiments in a lightweight manner with Linux consoles, software importability and physical portability. This paper describes a link-level measurement study as a sample experiment. It has measured the differences of Wi-Fi multicast/unicast links and Bluetooth links. One of the lessons we must learn from the result is that Wi-Fi unicast sockets sometimes work poorly even if the node can communicate with multicast sockets especially when the network scale becomes large.