LTE is based on a full IP (Internet Protocol) architecture. The visionaries of LTE looked at phone calls, as a Voice over IP application (they called it Voice over LTE), and created a component in the LTE Core, called IMS to handle those voice calls.
Service Operators need to invest a lot of money in getting their territories covered with bases stations. The usage of data is also increasing exponentially. Also, the frequency spectrum that the service operators paid for it (so called licenses frequencies) are being used to their extent today, and there is no place for expansion. In addition, there are many places (especially in home and at the office) that the base stations signal cannot reach.
On the other hand, WiFi technology is blossoming. Every office and almost all houses are now wired for WiFi. Wifi is now offered free in main cities, parks, malls and airports. Better, the WiFi uses the non -licensed spectrum of 5 GHz and 2.4 GHz, and its access technology and spread is getting better with every new release. Best of all the underlying networking technology is the same as LTE – IP (Internet Protocol)
This is all happening today, but back in 2004, long before LTE was envisioned, and WiFi was in its beginning stages, several scientists in Alvarion started working on the problem, of how we can merge between both technologies.
The advantages are great, both to the service operators, and to the users. Service operators do not have to increase their expansion of base stations to meet the increasing need of users, in places where public free WiFi is available. More than that, as WiFi uses the non-licensed frequency, the service operators has a way to double their capacity for free. Lower costs to service operators will mean lower cost to users. And many users that are located in places with no good LTE coverage, can still make phone calls from their native dialers using WiFi access which in offices and homes is generally available.
The technology is called WiFi offloading, and it is based on three legs:
- The LTE standards need to allow a “non 3GPP” “untrusted”, terminals to be able to reach the IMS component in the LTE core.
- The cellular phone manufacturers and in particular the chip producers (Qualcomm, Intel) need to support those new protocols and allow the native dialer of the cellular phone to use WiFi and reach the IMS of the LTE core
- The Wifi protocols should not be changed. This was a fundamental understanding, that there are many WiFi access points around from every generation, and they all should work with this new technology.
The Scientists of Alvarion worked hard to solve the issues of secure methods that allow “Non 3GPP” “untrusted” terminals to reach the IMS component in the LTE core and were rewarded a patent. It took several years, and the 3GPP standard committees adapted those secure methods. Slowly, this technology is now adapted in the US where all the main service providers announced they are supporting it, and allowing WiFi offload , both for data and for native calls to work on their systems.