This invention provides a method and apparatus that uses a mobility
management server (MMS) device for supporting mobility management in
wireless networks. With the MMS device for services of resource
management and packet relay, this invention speeds up the handover
procedure for a mobile device switching from a first network domain to a
second network domain in a wireless network environment having a session
initiation protocol (SIP) server. When the mobile device needs to switch
to the second network domain, the MMS allocates the required resources
for packet relay, provides the related information for the second network
domain, and takes care of the packet relay. This invention shortens the
inter-domain handover latency and reduces the number of lost packets
during the handover procedure. Thereby, the transmission efficiency of
the present invention meets the requirement for real-time multimedia
applications.