Evaluating WiMAX for Public Safety

Public safety agencies traditionally use mobile radio systems for communications although cell phones for voice and data are also now widely used. Most law enforcement officials would agree that these communications systems are not sufficient to meet the needs of law enforcement. Consequently there is significant interest in broadband wireless technology. In the research presented in this paper, we have evaluated WiMAX communications technology for use by public safety. Worldwide Interoperability for Microwave Access (referred to as WiMAX) is a MAC and physical layer wireless communications technology for outdoor broadband wireless coverage. We have deployed an 802.16d WiMAX network that operates at 4.9 GHz (spectrum reserved for public safety) at Clemson University. In this paper, we present the results from a performance analysis we have conducted of our WiMAX network. To the best of our knowledge the work reported in this paper is the first academic study of WiMAX in an operational network in which controlled experiments could be conducted. The WiMAX standard leaves key areas of the protocol, including packet scheduling, frame packing, and modulation/coding adaptation, unspecified. In order to accurately model and analyze WiMAX, realistic assumptions must be used. Because WiMAX systems have not been widely studied, there is a disconnect between theoretical WiMAX systems and real-world deployed systems. This motivates the research presented in this paper. Using knowledge of the equipment’s implementation choices, we derive theoretical application throughput for both TCP and UDP protocols and correlate expected results with empirical results.