Dormant mode operation support for roaming from WLAN to UMTS

The paper addresses dormant mode operation support for wireless local area network (WLAN)-UMTS roaming for dual-mode users. Dormant mode operation means that the dormant MS stays in its dormant mode when it roams from WLAN to UMTS or UMTS to WLAN and keep its sessions open using mobile IP. Current technology doesn´t support dormant mode operation when users roam between inter-technologies. User may roam in one of the technologies only. We propose a methodology to support the dormant mode roaming between inter-technologies, namely wireless local area networks and UMTS (or GPRS). The methodology is based on letting the access point of WLAN or GGSN of UMTS perform necessary registration functions in lieu of the mobile.