AT&T Laboratories is asking the FCC for permission to evaluate the 28 GHz and 39 GHz bands for potential 5G communications, deploying radio units at various outdoor locations around the AT&T office facilities in Middletown, New Jersey.
The radio transmitters that AT&T plans to use may use frequency hopping in wide band channels (100 MHz to 800 MHz) or digital QAM modulation in narrower band channels (5 MHz to 14 MHz). Different transmitters also may use the same or different channels as each other, and the total conducted power of any transmitter will not exceed 23 dBm (0.2 Watts), with the maximum ERP of any radio not to exceed 50 dBm (100 watts), according to AT&T's application.
The radio systems in the tests will be constructed from various commercially available millimeter wave components and/or modified existing millimeter wave radios, but the application doesn't specify any particular manufacturer.
Each radio unit will consist of a transmitter, a receiver and a directional antenna. With the antennas, much of the experimentation will be centered around the evaluation of different antenna and propagation path configurations that may use different antennas of various gains and beamwidths. Multiple radios could also be used to investigate MIMO channel characteristics.
While AT&T awaits the FCC's verdict on these tests, rival Verizon just got the green light from the FCC last week to lease 93 LMDS (28 GHz) licenses and nine 39 GHz licenses from Nextlink Wireless, a wholly owned subsidiary of XO Holdings. Verizon has said the lease of these licenses will be important in its development of 5G technologies. In granting the OK, the FCC said it determined that the deal didn't raise any particular competitive concerns. The lease of the millimeter wave spectrum by Verizon Wireless will be for a maximum of two-and-a-half years.
T-Mobile has 200 MHz of high-band spectrum in the 28-39 GHz range that it acquired as part of its acquisition of Metro PCS, and analysts at Wells Fargo Securities have said that spectrum might give T-Mobile a first-mover advantage in 5G trials. But T-Mobile CTO Neville Ray didn't overpromise anything when asked about 5G during the company's second-quarter conference call last week.
"When you come to 5G, I mean it's the current debate on steroids, right? 28-gig and with everything that will happen with massive MIMO and beam forming, sure the physics will help. But it's going to be very, very difficult to match 28-gig to even 2.5-gig spectrum performance," Ray said, according to a Seeking Alpha transcript.
"The industry is working very hard on those things, but I think early 5G rollouts will be pretty much capacity-type offloads. You'll see them in small dense areas of network, maybe core areas in big cities. That's why you'll see this stuff happen in urban footprints to begin with. But it's going to be years, decades, maybe even never when you're going to see 28-gig deployed on a broad scale basis. The physics just don't work and the costs to make it work across that type of range," he said.
"If Sprint can't make it work in 2.5-gig, how is the industry going to break the back of it in 28 gigahertz or 70 gigahertz? And so, I think your question about what does that all cost from a 5G vision perspective? Right now, this game, right, in the next three years to four years in this industry, it's all about what you do on LTE, and LTE Advanced. That's the game. And as I mentioned at the beginning of my comments, we're the most advanced LTE network in the U.S.," he added.
For more:
- see this application and this exhibit (PDF)
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Analyst: T-Mobile's 28-39 GHz spectrum could give it advantage in 5G trials