Some Clarification on LTE in Unlicensed Spectrum

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After writing two posts on potential carrier use of LTE technology in unlicensed spectrum (see here and here), I came across some information that helps clarify the functionality of and relationship between LTE Unlicensed (LTE-U) and License-Assisted Access (LAA).  In those posts I referred to these as if they were different names for the same technology. A more accurate statement would be that:

1) LTE-U is an earlier iteration of “LTE in unlicensed spectrum” technology that conforms to the less stringent spectrum sharing requirements of countries like the U.S., South Korea, China and India;

2) LAA will provide a standardized technology that goes further than LTE-U by satisfying the more demanding spectrum-sharing requirements in other markets, including Europe and Japan.

The clarification comes courtesy of the Qualcomm web site, which provides a summary of LTE-U here, and of LAA here.  As noted in an earlier post, Qualcomm is a leading advocate of carrier deployment of LTE in unlicensed spectrum, having introduced the idea in late 2013. Selected excerpts from both descriptions are below.

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“LTE Unlicensed” Deployments Planned for 2016

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In the last post in this series I reviewed several different points of view regarding the pros and cons of cellular carriers using “LTE Unlicensed” (LTE-U) to expand their network capacity. In this post I’ll take a closer look at movement in this direction among U.S. carriers.

[Note: The deployment of LTE in unlicensed bands is referred to by multiple names, including “LTE Advanced in unlicensed spectrum,” “LTE Unlicensed” (LTE-U) and, most recently “Licensed Assisted Access” LTE (LAA). In this post I’ll refer to it as LTE-U, though other names may appear in some excerpts included in the post.]

The two U.S. cellular providers that have so far expressed most enthusiasm for LTE-U are Verizon and T-Mobile.

Reporting from the Mobile World Congress held March 2-5 in Barcelona, Spain, Mike Dano wrote the following in the March 3 FierceWireless online newsletter:

[B]ased on the discussions I’ve had this week, it appears that Verizon…, Vodafone and other carriers last year decided they wanted to make LTE-U a reality–and they decided they didn’t want to wait for the 3GPP to standardize the technology. So they teamed up with some network technology companies to design real-world tests of the technology…

Verizon clearly has high hopes for the tests and the technology–it has said that it plans to commercially deploy it in the 5 GHz and 3.5 GHz bands in 2016. Verizon is not the only carrier that supports LTE-U/LAA. T-Mobile announced this year that it too will deploy what it calls LAA in the 5 GHz band in 2016. T-Mobile CTO Neville Ray said he believes the carrier can get LAA-capable handsets this year.

As Dano notes, “[h]owever, not all carriers are on board.” Specifically, he points to comments from Tom Keathley, senior VP of wireless network architecture and design for AT&T. As one might expect from a carrier that has invested in a network of more than 30,000 WiFi hotspots, AT&T’s concerns include the risk that LTE-U deployments will not share unlicensed spectrum fairly and efficiently with WiFi.

Keathley said that current approaches to LTE-U are vague about how exactly to check for existing users in unlicensed bands, and how long LTE users can occupy unlicensed spectrum.

Dano also cites comments from Eric Parsons, an executive at Ericsson, a leading wireless network equipment vendor, regarding how these spectrum sharing issues might be dealt with in different regions of the world. As Parsons explains, “there are very specific guidelines in Europe and Japan that cover these areas, but countries like the United States don’t have specific guidelines.”

T-Mobile, which has less licensed spectrum to work with than its competitors (see here for T-Mobile CEO John Legere’s perspective on this issue), seems particularly interested in LTE-U. In anticipation of commercial deployments in 2016, it has announced plans for multiple tests of the technology, in cooperation with Alcatel-Lucent and Qualcomm, Ericsson and Nokia.

In a January 5, 2015 blog post T-Mobile chief technology officer Neville R. Ray shed some light on the company’s plans:

Currently, there is approximately 550 MHz of underutilized spectrum in the 5 GHz Unlicensed National Information Infrastructure (UNII) band, which is available for any use within the FCC’s rules for the UNII band. LAA is a new and innovative approach that allows for licensed and unlicensed spectrum to work seamlessly together. And, we’ve already begun work with our various chipset, radio infrastructure and device partners to bring LAA production trials to life this year and bring the technology to our customers in the near-future.

During T-Mobile’s February 19, 2015 yearend earnings call, Ray provided an update on the company’s LTE-U plans:

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A Range of Views on LTE in Unlicensed Spectrum

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A key theme in this “unlicensed spectrum” series of blog posts has been the potential negative impacts on wireless carriers of lower-cost services built on WiFi connectivity, either in a “WiFi-first” or “WiFi-only” mode.

In this two-part post the focus will shift to potential LTE deployments in unlicensed spectrum by licensed carriers, as they seek to increase network capacity while retaining tighter integration with their existing LTE-based networks than they can achieve with WiFi technology.

The prospect of carriers deploying LTE in unlicensed bands marks a new phase in the history of unlicensed spectrum. In this new phase licensed carriers and their preferred technologies (e.g., LTE) could play a much bigger role in the unlicensed space, potentially disrupting the existing spectrum sharing model embodied in WiFi standards and familiar to users of WiFi technology.

The deployment of LTE in unlicensed bands is referred to by multiple names, including “LTE Advanced in unlicensed spectrum,” “LTE Unlicensed” (LTE-U) and, most recently “Licensed Assisted Access” LTE (LAA). In this post I’ll refer to it as LTE-U, though other names will appear in some excerpts included in the post.

Not surprisingly, there exists a fairly broad range of views on the balance of benefits and harms likely to occur from carrier deployment of LTE-U.  As one might expect, Qualcomm, the wireless tech giant that first proposed the idea in late 2013, is enthusiastic. In a November 20, 2013 blog post, Prakash Sangam, Director, Technical Marketing summarized his company’s perspective:

Consider the length that operators are going to address increasing data traffic with small cells and utilizing all spectrum assets….Wouldn’t it be ideal for them to deploy small cells that support LTE not only in their regular licensed spectrum but also in unlicensed spectrum?…[I]nstead of managing two separate networks for licensed and unlicensed spectrum, and dealing with the complexities of interworking between them, they will have one unified network accomplishing the tightest possible interworking. How cool is that?

Okay, the operators are covered. What about the mere mortals like us, the users? Well, remember all the juggling between LTE and Wi-Fi networks; making sure you are connected, and connected to the right technology to get the best speed; worries about the media not seamlessly moving over between the networks, and tolerating video freezing, breaks, restarts etc.? All of that will be over with LTE Advanced in unlicensed spectrum…Because it’s one network, with an anchor in the highly reliable licensed band, you are always in safe hands. Add to that carrier aggregation, across licensed and unlicensed bands, and you, the user, get higher data rates and an enhanced broadband experience.

This is all good, but one natural question someone might ask (we asked it ourselves) is, “will it affect the Wi-Fi networks out there now?” Well, LTE Advanced in unlicensed spectrum has been carefully designed to protect Wi-Fi, so that both can co-exist harmoniously. So, when an operator switches from Wi-Fi (“carrier Wi-Fi” as it is called in the industry) [to] LTE in unlicensed, not only do LTE Advanced users in the unlicensed spectrum benefit but also, in many cases, the neighboring Wi-Fi users.

Moreover, LTE Advanced in unlicensed can be brought to fruition in countries such as the United States, Korea and China using the existing standards (Rel 10) and, of course, by leveraging the existing LTE core networks.

Given the cable industry’s growing enthusiasm for a WiFi-based wireless strategy (see here and here), it’s not surprising that they are less enthusiastic than Qualcomm about wireless carriers deploying LTE in unlicensed spectrum. In a May 21, 2014 post on the CableLabs blog, Ian MacMillan expressed some of their concerns:

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