In the previous post, I had written about the scope of the Release 12 Study Item (SI) on 3GPP-WLAN Interworking. As with any other SI, the first step was define the requirements and scenarios for this study. While the focus is on Carrier WiFi deployments only, this includes the case where an independent WLAN provider partners with a 3GPP operator to provide WLAN access to the latter’s subscribers. The requirements for the candidate solutions have been captured in 3GPP TR 37.834 and they are reproduced below:
1. Solutions should provide improved bi-directional load balancing between WLAN and 3GPP radio access networks in order to provide improved system capacity.
2. Solutions should improve performance (WLAN interworking should not result in decreased but preferable in better user experience).
3. Solutions should improve the utilization of WLAN when it is available and not congested.
4. Solutions should reduce or maintain battery consumption (e.g. due to WLAN scanning/discovery).
5. Solutions should be compatible with all existing CN WLAN related functionality, e.g. seamless and non-seamless offload, trusted and non-trusted access, MAPCON and IFOM.
6. Solutions should be backward compatible with existing 3GPP and WLAN specifications, i.e. work with legacy UEs even though legacy UEs may not benefit from the improvements provided by these solutions.
7. Solutions should rely on existing WLAN functionality and should avoid changes to IEEE and WFA specifications.
8. Per target WLAN system distinction (e.g. based on SSID) should be possible.
9. Per-UE control for traffic steering should be possible.
10. Solutions should ensure that access selection decisions should not lead to ping-ponging between UTRAN/E-UTRAN and WLAN.
The candidate solutions should be based on the understanding that there is no RAN level information exchange between H(e)NBs/eNBs/RNCs and APs via standardized interface. Based on these requirements and the working assumption, a set of solutions are being currently discussed by 3GPP RAN2. These will be described in the next post.