Handover Schemes for Mobile WIMAX Networks: Review, Challenge and the State of Art

Handover (HO) mechanism is one of the critical operations in Mobile WIMAX. It takes place when a mobile station (MS) moves from a serving base station (BS) to another BS.The handover procedure is comprised of several stages; network topology advertisement, MS scanning, cell selection, handover initiation and decision and network re-entry including ranging, authorization, authentication and re-registration. During these stages, still some issues, such as unnecessary scanning, handover delay and MAC overhead, ping-pong handover and handover failure which may affect real-time applications. In this article, we present mobility features in WiMAX systems and survey the handover mechanism along with their schemes, strategies and protocol categories, and elaborate in each stage upon the classification and comparison among various handover schemes. Furthermore, it identifies and discusses several issues and challenges facing mobility management along with an evaluation and comparison of several relevant mobility studies.