CitySense : The Design and Performance of an Urban Wireless Sensor Network Testbed

This paper 1 describes the design of a wireless urban sensor network testbed, CitySense. This first-of-its-kind testbed enables wireless networking researchers to perform repeatable experiments in a real-world environment. Studies that were previously limited to simulation and the laboratory can be validated through long-lived experiments in real-world environments. Unlike prior, mote-based sensor networks, CitySense nodes have a high powered CPU with large persistent storage and highbandwidth radios to support multiple user applications. First, we describe the testbed and the unique design considerations required by its urban deployment. Second, we present results from a measurement study to characterize the performance of the radio-frequency links. Our results show that: (a) existing empirical models accurately predict the bounds on RF link lengths (b) the 2.4 GHz radio exhibits a lower pathloss exponent than the 900 MHz radio (α = 3.4 vs. α = 3.75); and (c) RSS is only a modest predictor of link throughput, R = 0.77. Finally, we describe future studies planned for the testbed.