11.1. Functional architecture
The integration of Wi-Fi technology into the 4G mobile network results in the sharing of sessions between LTE (Long-Term Evolution) access (e.g. VoLTE session) and Wi-Fi access (e.g. Internet session). The aggregation of LTE and Wi-Fi access is done at the PDN gateway (PDN). The consideration of Wi-Fi access impacts the architecture of the evolved packet core (EPC).
The aggregation of the carriers results in a sharing of the IP (Internet Protocol) packets between the different accesses. For the downstream direction (respectively the upstream direction), the sharing is performed by the evolved node B station (eNB) (respectively the mobile) and the reassembly is provided by the mobile (respectively the entity eNB). This operation is performed exclusively in the enhanced universal terrestrial radio access network (E-UTRAN) and does not impact the EPC network (Figure 11.1).
LTE and Wi-Fi carrier aggregation can be implemented with collocated or remote eNB and AP (Access Point) entities. The Xw interface is the point of reference between the eNB and AP entities when they are distant (Figure 11.1).
The eNB entity is the anchor point for the data exchanged with the mobile, belonging to the user plane (the IP packets) and the control plane and connects to ...