Operators have been increasingly using 802.11 Wi-Fi access points (APs) in unlicensed spectrum for opportunistic offloading of mobile traffic. To cost-effectively leverage Wi-Fi where cellular small cells are installed and vice versa, LTE/3G small cell and Wi-Fi APs infrastructure will be more tightly integrated in the future.
To further integrate Wi-Fi APs with cellular infrastructure, operators will manage access to their Wi-Fi APs via LTE/3G. 3GPP Rel-12 worked on control plane interworking between Wi-Fi and LTE/3G, which will allow more dynamic and reliable control of Wi-Fi offloading. The RAN network will make better offload decisions assisted by reports from the devices, and Wi-Fi will appear just as another carrier managed by operator to convey traffic.
Qualcomm Research has been working on LTE/3G and Wi-Fi convergence for some time. In 3GPP, along with other participants, we have been contributing to the LTE-Wi-Fi interworking standardization. Going forward, the focus will be on aggregation of LTE and Wi-Fi at PDCP layer. While it is possible to aggregate the 2 technologies at higher layers, doing so at the RAN level such as the PDCP layer benefits all applications and gives more control to operators. By allowing users to simultaneously connect to LTE and Wi-Fi, user experience will improve and load on both networks can be balanced dynamically.
In practical networks, LTE coverage is generally ubiquitous while Wi-Fi is deployed selectively at hotspots. As users move in and out of Wi-Fi coverage, the LTE connection is maintained and the addition and removal of Wi-Fi connection should be seamless to the users.
PDCP aggregation can be supported with legacy Wi-Fi APs together with non-collocated LTE eNBs provided a link exists between them for the AP to report information such as loading and MCS to the eNB. Operators interested in deploying this feature do not have to replace their existing Wi-Fi infrastructure. For optimal performance, the latency of the link between the LTE eNB and Wi-Fi AP should be kept low.
Qualcomm Research has an over-the-air network in San Diego with multiple eNBs and Wi-Fi APs. This network is used to validate LTE-Wi-Fi PDCP layer aggregation and will also be used to showcase the improvement in user experience from this feature at MWC 2015