It is an important issue for user terminals to perform network selection and thus enable traffi c offl oading for interworking between WLAN and 3GPP networks. Traditional solutions focused on core network without taking into account traffi c load on radio network

and will therefore lead to load unbalance and user experience degradation. To solve this problem

3GPP launched study item and work item on WLAN and 3GPP radio interworking in R12 phase

defi ning a series of RAN auxiliary parameters and rules to enhance access network selection and traffi c offl oading on radio network side

which can improve user experience and provide more effi cient administration capability of WLAN for operators thus achieving a deep convergence solution for interworking between WLAN and 3GPP.