 WLAN AP instead. The LTE RSRP and RSRQ parameters avoid offloading for a UE with good LTE signal quality (close to LTE eNodeB) and rather encourage off-loading for users at the cell edge area. The 't-Steering WLAN' parameter defines the timer value during which the rules should be fulfilled. This avoids moving back and forth very rapidly between LTE and WLAN; for example, when the WLAN AP load varies. The LTE eNodeB can signal the parameters individually for each user, if there is a need to address specific situation for a particular device. This makes it possible to have, for example, longer timer values for some UEs or even restrict the off-loading for some UEs due to frequent bearer changes. The Release 12 solution has some known shortcomings, and the 3GPP Release 13 is expected to address the further enhancements, for example, with the co-located WLAN AP with LTE eNodeB. The solutions on the table range from extending the Release 12 solution, defining the earlier rejected solution 3 (handover type operation) or go all the way to the radio-level aggregation where the data would be divided in the PDCP layer between LTE and WLAN based on the radio conditions and load conditions both on LTE- and WLAN-sided. The example of a possible aggregation framework is shown in Figure 3.8. The aggregation would move closer to the radio the approach currently available in the application layer where the same bearer would be divided between LTE and WLAN, but invisible to the radio layer. LTE-Advanced Evolution in Releases 12-13 eNodeB eNodeB-WLAN interface WLAN AP UE application Figure 3.9 Proposed Release 13 approach for WLAN/LTE radio-level aggregation Such an approach has the benefit of avoiding any changes to the WLAN infrastructure while the full aggregation would also require LTE eNodeB still to receive all the traffic going via WLAN AP as well, in contrast to full off-loading (and available only for the co-located case). To which extend such an aggregation would prove better than the application-level multipoint TCP op