What if wireless operators had the ability to add substantial capacity to their networks without having to pay billions of dollars for additional spectrum? And what if this also made your WiFi work better? Well, there has been quite a bit of work going on behind the scenes on something called LTE Unlicensed (LTE-U) and 2016 is going to be a pivotal year. Just this week, the LTE-U community cleared an important hurdle, with the FCC authorizing live tests of LTE-U at two Verizon facilities. So what is LTE-U, what is its status, who is it for, and what are its prospects for success?
LTE-U is a proposal to use commercial 4G LTE cellular services as we know them today, in 500 MHz of the 5 GHz unlicensed band, which is also used for WiFi. It is considered ‘unlicensed’ because the operators would not have to buy separate, licensed spectrum in order to operate LTE-U services. However, LTE-U only works alongside licensed wireless services. LTE-U is also referred to as Licensed Assisted Access (LAA), which represents the 3GPP’s effort to incorporate LTE-U into Release 13 by requiring Listen Before Talk, which is a standardized effort to ensure there is no interference with WiFi before LTE is invoked. LTE-U is sort of a “pre-LAA version” of LAA that might be permitted in the U.S. and some other countries.
LTE-U promises about 2x the range and capacity of current WiFi. The idea is it would work like WiFi but better (hence the term “carrier WiFi”) and as a seamless extension of cellular services on LTE-U equipped phones. For operators, LTE-U is part of their overall “carrier aggregation” strategy, which combines channels across their spectrum holdings to deliver higher speeds and more capacity. Operators gain the capacity at LTE-U venues while keeping traffic on their network, with the additional benefit of offloading traffic from the macro. LTE-U would be used mainly for indoor locations and venues such as hotels, stadiums, universities, and casinos. On the equipment side, LTE-U compliant small cells/APs would have to be installed by the operator or venue owner. Only new phones and other devices equipped with an LTE-U chipset would work.
Qualcomm has been spearheading the LTE-U movement, clearly with the objective of selling more chipsets (on the transceiver and user equipment sides). The LTE-U Forum and a consortium called Evolve, consisting of leading equipment vendors including Qualcomm, Ericsson, Samsung, and several carriers, have been pushing to move things along in industry and with the FCC. The main obstacle is the potential interference with WiFi in the 5 GHz band. The WiFi crowd has been instrumental in securing increased channels for WiFi at 5 GHz from the FCC over the past couple of years and is concerned about the potential for interference from LTE-U. This is a valid concern, especially because LTE-U is the “stronger party” — sort of like a 6 foot, 250 pound football player getting on a field where everyone else is 5’8″ and 175 pounds. Qualcomm and others have done a lot of work to address the potential for interference and have shown many LTE-U simulations in an attempt to dispel these concerns. At a high level, the idea is LTE would dynamically shut itself on & off in the unlicensed band, depending on the level of contention for WiFi.
In the U.S., Verizon and T-Mobile are the two operators leading the charge on LTE-U. It appears 2016 will be a year of testing and proving. There are still contentions between the LTE-U community (which has formed the Evolve alliance) and the WiFi community (WiFi Alliance, WiFi Forward) in terms of who is doing the testing, how it will be done, and what are the parameters required to make LTE-U acceptable on both the network and the user experience side. Then there is the FCC approval process, where the exact procedures, requirements, and timing are still uncertain. It’s not even that clear to me the extent to which the FCC would actually have to approve LTE-U.
On the equipment side, it looks like some of the network products will be available in 2Q/3Q. Another key is whether—and when—LTE-U will be available in handsets. The device OEMs have said very little publicly. Between the tests, approvals, and equipment commitments, certifications, and lead times, commercial LTE-U services aren’t likely before mid-2017 and probably into 2018.
But the real question is what the market is for LTE-U and what its role is given the continued expansion of alternatives, such as the better coexistence of WiFi and cellular with Hotspot 2.0/Passpoint and the deployment of more small cells, both indoor and outdoor. Certainly for the operators, LTE-U represents a cost effective way to expand capacity, especially for video, which is highly consumptive of the downlink bandwidth. It’s also a way to more fully leverage the Carrier Aggregation capabilities of LTE Advanced, which is an important part of the LTE roadmap for the next few years, in advance of 5G. And if Sprint (which is not a backer of LTE-U) is truly able to roll out a high-speed, high capacity ‘LTE Plus’ wireless network in certain cities, leveraging its 2.5 GHz spectrum, then LTE-U could be a counter weapon available to its competitors.
The full business case for LTE-U has still not been fleshed out. For example, what will be the division of cost responsibilities between the operator and the venue/enterprise for equipment? This is an issue that has held up the deployment of indoor small cells and other coverage/capacity enhancers. On the other hand, small cells that incorporate LTE-U in addition to LTE and WiFi could expand the use cases and market potential of small cells.
Even though the business case is a bit tenuous, we should also view LTE-U as a solution not in isolation, but in the increasingly Venn Diagram-esque world of wireless network solutions that include and incorporate cellular macro cells, small cells, and WiFi. For example, more work needs to be done to improve the user experience of moving between cellular and WiFi (see my November piece, “Cellular and WiFi Need to Get Along Better”), which is hopefully being incorporated into some of the work on LTE-U.
Additionally, the work being done on interference mitigation by Qualcomm and others will likely have broader benefits in a world of denser, heterogeneous wireless networks that include macro cells, small cells of various stripes, and WiFi. Mutual coexistence between licensed and unlicensed services, more effective management of traffic between cellular and WiFi, and a more seamless customer experience might be the ultimate beneficiaries.