Mobile worldwide interoperability for microwave access (WiMAX) is a technology that has received much attention for next-generation mobile broadband systems. In this paper, we focused on the physical layer of mobile WiMAX and performed field experiments. We show the performance of a WiMAX base station in the field using the error vector magnitude (EVM) performance measure experimentally and theoretically. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.