An improved interworking architecture for UMTS-WLAN tight coupling

The paper proposes an interworking architecture, TCWA (tight coupling with wireless access), for integrating Universal Mobile Telecommunications System (UMTS) and wireless local area networks (WLAN). Based on a tight coupling interworking architecture, TCWA creates an additional wireless link between the base station of a UMTS cell and the gateway router of a WLAN located within this UMTS cell. In TCWA, signaling is routed according to the original tight coupling to preserve network security. However, the data traffic in the inter-network communications can be dynamically distributed as the added wireless link provides alternative routes. The issue of seamless vertical handoff in the TCWA architecture is also addressed in detail. To reduce handoff latency, a fast handoff algorithm is adopted. Based on detailed analysis and numerical results, we show that TCWA can reduce the traffic cost, relieve the burden of the core UMTS network, and enhance fault tolerance.