Architectural options for the WLAN integration at the UMTS radio access level

Integration of UMTS and WLAN networks can be done at different levels. A promising interworking approach, expected to support seamless vertical handovers, is the one where the WLAN is embedded in the UMTS radio access network. It is suitable for 3G operators, which are provided with extra license-free bandwidth in hot spots. This paper addresses this type of integration, discussing two types of network architecture. These architectures differ in the UMTS interface at which the WLAN is integrated. The focus is put on the WLAN integration at the Iub interface. Several possible architectural options and necessary modifications are discussed. An Iub-based option, where user data is transferred via the WLAN, while the signalling is exchanged over the WCDMA interface is presented more in detail.