T-Mobile Pushes Wi-Fi Alternative Tech for Three-Tiered 3.5 GHz Spectrum Band

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By Brandon Ross

March 16 — T-Mobile US Inc. urged use of alternative technologies to Wi-Fi in the 3.5 gigahertz (GHz) spectrum band, and requested that FCC rules accommodate a range of technologies in the band in a filing.

The Federal Communications Commission is considering access to the band for shared federal, commercial and public use—a three-tiered spectrum access system (SAS). Parts of the 3.5 GHz spectrum band, also known as the innovation band, are currently only allocated to federal and non-federal incumbent users.

Licensed Assisted Access (LAA) “allows unlicensed spectrum to be aggregated with licensed spectrum to enhance the capacity of [wireless] carrier systems while providing highly reliable services,” T-Mobile said in a ex-parte filing to the FCC posted March 16, which described its vision for carrier use of the 3.5 GHz band. “Unlike current carrier use of Wi-Fi, LAA works with an operator’s existing spectrum and network design in a robust and integrated fashion.”

“We explained that while T-Mobile is, and will continue to be, a significant user of Wi-Fi technology, it is also exploring the use of Licensed Assisted Access in, among others, the 3.5 GHz band,” T-Mobile said in the filing. “We noted the benefits of LAA and that it is compatible with other technologies, including Wi-Fi.”

Benefits of LAA

LAA would bring faster speeds to mobile phones and other mobile devices and reduce network latency, according to the filing.

It will also give significantly better coverage performance, the filing said. LAA offers the same complex quality of service controls as Long-Term-Evolution (LTE) technology, T-Mobile's filing said.

LAA is a “good neighbor” to other technologies, including Wi-Fi technology, the T-Mobile filing said. Compatibility with Wi-Fi technology is an important component for use in the 3.5 GHz band because the band is meant to operate on small cell technology.

Small cells act, essentially, as mini cellular towers, but they can be installed with significantly greater ease. While a single small cell device doesn't offer the same large coverage area as a cell tower, small cells can be installed on light poles, for instance, and wouldn't require the large undertakings involved with the environmental impact studies needed before a cell tower can be erected. They are meant to be deployed in bulk and are generally more efficient, in most respects, to cell towers.

LAA incorporates various features to make spectrum sharing, the FCC's goal of the so-called innovation band, easier. According to the filing, LAA's spectrum sharing features incorporate:

• reserving “time slots for other technologies”;

• selecting the “cleanest” channel based on Wi-Fi and LTE measurements;

• creating on-off time pattern when energy is sensed above specified level; and

• Deactivating “particular small cells when not in use.”


Flexible Technology Standards

The tiered access system would give highest-priority to federal incumbent users, medium-priority access to licensed users and lowest-priority access to unlicensed general access users.

Past FCC decisions have shown that rules tailored with the minimum level of technology restrictions generally work best, T-Mobile's filing said.

“The FCC should not adopt rules that would require or restrict particular technologies in the 3.5 GHz band – Additional rules could have the effect of locking in outdated technologies,” T-Mobile's filing said. “As long as the FCC establishes basic parameters designed to allow all technologies to work together as it has in Section 96.38 (i.e., power, emission limits, etc.), there should be no further restrictions or specifications on how unlicensed spectrum can be used.”

To contact the reporter on this story: Brandon Ross in Washington at bross@bna.com

To contact the editor responsible for this story: Heather Rothman at hrothman@bna.com

The full T-Mobile filing is available here: http://op.bna.com/der.nsf/r?Open=kfex-9unrxm.

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