Global gateway-based UMTS/WLAN integration for improved delay performance

Abstract

This paper proposes a loose coupling-based integration between universal mobile telecommunication system (UMTS) and wireless local area networks (WLANs) using mobile Internet protocol (MIP)-based vertical handoff between the two networks. In loose coupling, an integrated network must provide home agent (HA) functionality when a UMTS subscriber moves to WLAN. The position of HA effects the performance of an integrated network. If HA is deployed at gateway GPRS (general packet radio service) support node (GGSN), delay for data as well as control packets increases when both receiving and transmitting mobile stations (MSs) reside in WLAN. Because each packet travels to GGSN through Gi interface, and routed back to WLAN through the same interface. HA can also be deployed in WLAN Internet protocol (IP) network. This improves delay for data packets, but handoff delay from WLAN to UMTS increases because an MS cannot send MIP registration request to HA before the establishment of packet data protocol context in UMTS network. We propose an efficient integration by fixing the position of HA in a global gateway router which is deployed in WLAN IP network. The proposed interworking technique reduces packet delay when both sending and receiving MSs are in WLANs. The methods also update location of a user in UMTS as well as WLAN so that he/she is always reachable from each network irrespective of current position. ns-2-Based simulation results show that our new handoff methods reduce handoff delay from UMTS to WLAN by 10% and that from WLAN to UMTS by 18%.