Although there are some legitimate concerns over the different usages of WiMAX networks (e.g., licensed or license-exempt concerns), from the technical aspect, three usage types, fixed, nomadic, and mobile users, are the target cus tomers of WiMAX networks. The first goal of this chapter is to review the standards of WiMAX technologies to support these usage types. Furthermore, from a practical point of view, before the deployment of WiMAX networks achieves its popularity, a hybrid environment of WiMAX and WiFi networks is more likely to coexist for a while. Th erefore, one of the primary concerns is to design a seamless handover process in this hybrid network environment. Th e second goal of this chapter is to dedicate to this issue.