The key difference with respect to Solution 1 is that the 3GPP RAN decides when a UE should connect to the WLAN and how traffic should be steered to/from 3GPP network. The figure below illustrates the process.
- RAN configures a measurement for WLAN. It may provide measurement object & reporting configuration if UE supports WLAN interworking and RAN wants to interwork with WLAN
- After receiving measurement configuration, the UE measures WLAN. If there is a WLAN that satisfies the reporting configuration, the UE reports the measured result to RAN.
- If RAN finds that offloading is necessary & the reported WLAN is appropriate, it transmits offloading command to steer traffic from RAN to WLAN. Alternatively, if RAN finds that the WLAN is not appropriate for offloading any more, it transmits reverse offloading command.
- When the UE receives the forward offloading command, it connects to the indicated WLAN and continues data transmission and reception with it. If bearer info is also received from RAN, UE continues data transmission/reception of the bearer with WLAN
- When a reverse offloading command is received by the UE, it continues data transmission/reception with RAN instead of using WLAN.