WiMAX performance at 4.9 GHz

Worldwide Interoperability for Microwave Access (referred to as WiMAX) is a MAC and physical layer wireless communications technology for outdoor broadband wireless coverage. In collaboration with the Clemson University Police Department, we have deployed an 802.16d WiMAX network that operates at 4.9 GHz at Clemson University. In this paper, we present the results from a performance analysis we have conducted of the WiMAX network. To the best of our knowledge the work reported in this paper is the first academic study of an operational 4.9 GHz WiMAX in which controlled experiments could be conducted. While neither the 4.9 GHz spectrum nor the current WiMAX profiles settings might be optimal for space or lunar communications, a study of WiMAX at any frequency is of value to both the aerospace industry and the research community. 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. We also summarize results from a coverage analysis of the system. The combined results lead to an important point: although equipment implementation choices contribute to the achieved performance of WiMAX, the physics surrounding 4.9 GHz RF propagation will likely have the most significant impact on system performance.