Large, Small Wireless Carriers Spar on Device Interoperability

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By Paul Barbagallo  

The wireless industry remains divided on whether new regulations are needed to ensure that mobile devices used in the lower 700 megahertz band of spectrum can operate on airwaves used by different carriers, including Verizon Wireless and AT&T Inc.

In comments filed with the Federal Communications Commission, carriers large and small staked out familiar positions on an issue that will factor heavily in the agency's effort to reclaim hundreds of megahertz of spectrum for mobile broadband and similar applications over the next decade.

“The commission should act quickly to make interoperability in the lower 700 MHz band--and eventually across the entire 700 MHz band--a reality,” RCA--The Competitive Carriers Association wrote in a filing dated June 1. “The commission has the legal authority to implement an interoperability mandate, and doing so is strongly in the public interest.”

The association and a number of its members--wireless carriers serving mostly smaller, more rural parts of the country--have alleged that Verizon and AT&T are pressuring manufacturers of handsets, chipsets, and network equipment to make their products compatible only with Verizon- and AT&T-occupied spectrum in the 700 MHz band.

No 4G Phones Without Interoperability, Small Carriers Say.

The carriers have argued that absent FCC action, their customers will be deprived of the latest smartphones and the ability to roam on Verizon and AT&T networks.

“The persistent lack of interoperability in the lower 700 MHz band since the close of Auction 73 has significantly impacted the availability and cost of equipment and devices to A Block licensees,” wrote Vulcan Wireless LLC.

In that auction, in 2008, Verizon acquired most of what is known as the “C” Block, paying $9.6 billion for 108 licenses. AT&T bought 227 licenses for $6.6 billion in the “B” and C blocks. A number of smaller mobile network operators purchased licenses in the lower A, B, and C blocks.

After the auction, the 3rd Generation Partnership Project, an industry standards-setting body known as the 3GPP, created four band classes within the 700 MHz band--12, 13, 14, and 17. Band class 13 was designated for Verizon's upper C Block spectrum; band class 17 for AT&T's lower B and C block spectrum; and band class 12 for the smaller operators' lower A, B, and C block spectrum. Band class 14 was created for the upper B Block and spectrum allocated for public safety use.

Compatibility an Issue.

As of right now, all handsets, chipsets, and network equipment made for band class 13 are incompatible with band class 17 or band class 12, and vice versa. And most manufacturers are making gear only for Verizon and AT&T.

To remedy the situation, Vulcan is urging the FCC to require wireless carriers to upgrade their base stations to support interoperability across the entire lower 700 MHz band within six months of a final FCC ruling.

With nine months of that ruling, any carrier offering at least one mobile device “that is capable of operating on any paired spectrum block within the lower 700 MHz band” would have to commercially offer and support, in each market in which the carrier offers service, at least one mobile device that can operate across all paired spectrum blocks in the lower part of the band, under Vulcan's recommendation.

Then, within 18 months, all devices would have to be interoperable in the lower 700 MHz band.

“Without readily available equipment that works across the lower 700 MHz band, lower A block licensees cannot attract potential retail or wholesale customers or provide commercially viable service on their lower A block spectrum,” Vulcan said.

Interference Issues Real: Verizon, AT&T.

But to Verizon and AT&T, regulatory mandates would undermine the standards processes at the 3GPP.

In rebutting the claims of smaller carriers, both companies argued that one of the underlying reasons for separating the 700 MHz blocks into different band classes is interference--the proximity of A Block spectrum pairs to TV broadcast transmissions on one hand, and high-power broadcast transmissions in the unpaired 700 MHz D Block and E Block on the other.

“The high power broadcasts permitted in broadcast TV channel 51 and in the 700 MHz lower 'E' Block create the potential for debilitating interference into the lower A and B blocks that could dramatically degrade wireless service. Indeed, these interference concerns led to the creation of 3GPP Band 17, which allows carriers to operate in the B and C blocks while filtering out the interference from the high-power transmissions adjacent to the A block,” AT&T explained in a blog post June 1.

AT&T Sees No Need for Mandate.

In official comments, AT&T said that an interoperability mandate is “unnecessary.”

“Manufacturers can and already do create Band 12 variants of LTE devices designed for other 700 MHz bands at negligible additional cost,” AT&T said. One carrier, US Cellular, has already announced the introduction of a number of Band 12 devices and its intention to bring more on line this year, the company noted.

But even if it did exist, an AT&T “Band 12 device” would be unusable anyway, it said.

AT&T's LTE devices will all “fall back” to GSM technologies (GSM is short for Global System for Mobile Communications, the world's most common wireless communications standard).

Most A Block carriers use the CDMA standard, or Code Division Multiple Access.

CDMA Standard.

For this reason, AT&T said, US Cellular's Band 12 LTE devices are “variants” of Verizon's Band 13 devices, since Verizon uses the CDMA standard.

But some smaller wireless carriers believe that without interoperability, not only will they lack 700 MHz band handsets to sell to their customers, their customers will not be able to roam onto Verizon's and AT&T's 4G LTE networks.

AT&T disagrees, noting that 4G devices are “increasingly multi-band devices.”

“Indeed, no carrier is likely to offer LTE on a single band and thus all will have to develop devices that support multiple bands,” AT&T said.

Like AT&T, Verizon advocated for a industry-led solution, rather than new regulations.

Broadcaster Relief?

To Verizon, the FCC could enable greater interoperability of devices by encouraging broadcasters on Channel 51 to relocate voluntarily in advance of so-called “voluntary incentive auctions” authorized by the Middle Class Tax Relief and Job Creation Act of 2012.

The FCC could offer broadcasters “first choice” in the relocation process and, for those broadcasters that elect to participate in the auctions, a premium on their bids to sell, Verizon said.

“Once the issues arising from Channel 51 operations are eliminated, an industry solution is likely to emerge for interoperable equipment in the lower 700 MHz band without the need for equipment mandates,” Verizon wrote in comments.

Weighing in with the manufacturer's perspective, Qualcomm told the commission that is working to design chipsets that “support the entire Lower 700 MHz band, mitigate interference, and improve interoperability.”

'Interference Challenges.'

At the same time, Qualcomm warned the agency that the lower 700 MHz band presents “unprecedented interference challenges.” Without proper filtering, the company said, a consumer device operating in B and C blocks would suffer blocking interference from E Block signals, intermodulation interference when the E Block signal combines with its transmit signal, and reverse intermodulation interference because of TV Channel 51.

“Qualcomm has not found an acceptable solution to these interference challenges,” it wrote. “Furthermore, unfortunately, the mitigation techniques suggested by A Block licensees will not work and studies purporting to show that these interference concerns are manageable are deeply flawed.”

Qualcomm said that the FCC should conclude that harmful interference from both the E Block and Channel 51 would “unacceptably degrade” consumer devices operating in the B and C Bands without the Band 17 filter in place.

“The company still does not have an interoperability solution that protects consumers from harmful interference--and creating one, if this outcome were mandated by the Commission, would take years, increase costs, and still yield consumer device degradation,” Qualcomm said.

To read the comments, visit and type in Docket No. 12-69.

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