WiMAX envisions four mobility-related usage scenarios −
Nomadic − The user is allowed to take a fixed subscriber station and reconnect from a different point of attachment.
Portable − Nomadic access is provided to a portable device, such as a PC card, with expectation of a best-effort handover.
Simple mobility − The subscriber may move at speeds up to 60 kmph with brief interruptions (less than 1 sec) during handoff.
Full mobility − Up to 120 kmph mobility and seamless handoff (less than 50 ms latency and < 1% packet loss) is supported.
It is likely that WiMAX networks will initially be deployed for fixed and nomadic applications and then evolve to support portability to full mobility over time.
The IEEE 802.16e-2005 standard defines a framework for supporting mobility management. In particular, the standard defines signaling mechanisms for tracking subscriber stations as they move from the coverage range of one base station to another when active or as they move from one paging group to another when idle.
The standard also has protocols to enable a seamless handover of ongoing connections from one base station to another.
The standard also has protocols to enable a seamless handover of ongoing connections from one base station to another. The WiMAX Forum has used the framework defined in IEEE 802.16e-2005, to further develop mobility management within an end-to-end network architecture framework. The architecture also supports IP-layer mobility using mobile IP.