We investigate in this paper the impact of mobility on the capacity of an OFDMA-based mobile WiMAX network in the presence of two types of flows : streaming and elastic, under a dynamic configuration where users come to the system following a Poisson process and leave it after a finite duration. This duration is independent on the amount of resources for streaming flow, such as voice, and proportional to the amount of resources they receive for elastic ones, such as data. Our analysis makes it possible to quantify several performance measures such as blocking/dropping probabilities as well as mean transfer time. Our results show that mobility decreases the blocking rate, introduced some dropping and increases the overall cell throughput