Industry Groups Agree Gaps in 600 MHz Band Plan Should Be as Small as Possible

"In our expert view, a separation larger than 12 MHz provides no meaningful benefit from an engineering perspective and would unnecessarily decrease the amount of licensed spectrum available for auction,” the letter said. “There is no sound engineering justification for the extremely large (18-28 MHz) duplex gaps proposed by some commenters in this proceeding. ... Such a large duplex gap would decrease antenna efficiency and would unnecessarily consume as much as 15 MHz (i.e. three 5 MHz blocks) that could otherwise be auctioned.”

A wider duplex gap also “increases the amount of spectrum that the Commission would need to recover in the reverse auction in order to achieve a minimum auctionable bandwidth in every geographic market in the country for the forward auction,” the letter said. On the topic of the guard band between mobile downlink and TV broadcasters, “according to our engineering analysis, no more than 10 MHz of separation is needed between the highest remaining full power TV station and the adjacent downlink block to avoid saturation and blocking of the mobile device receiver or interference to TV broadcast services,” the letter said. It (http://bit.ly/YjXhS2) was also signed by Alcatel-Lucent, Ericsson, Intel and Qualcomm.

One of the key topics at the workshop was the extent to which unlicensed operations can be safely located into the various gaps in the band plan. “We strongly urge the commission to go ahead and try to maximize the licensed spectrum first and solve the issues with respect to licensed spectrum,” said Christian Bergljung, representing Ericsson.

Qualcomm has done “exhaustive analysis” and found that putting unlicensed operations in the guard bands “will cause mutual interference between the services, it’s not avoidable,” said Kent Walker, a Qualcomm engineer. “The issue basically comes down to the filters aren’t good enough.” Walker doesn’t see a technical solution under which unlicensed use of the bands won’t cause problems, he said. “It’s just a matter of degree.”

CTIA wants to see licensed and unlicensed spectrum prosper, said Wiley Rein’s Tom Dombrowsky, representing the association. “But until we get the licensed, paired, spectrum frequency bands sort of settled one way or another, it’s going to be very difficult to sort of figure out what goes into the guard bands when you don’t know what the size of the guard bands are, what the technical requirements or the guard bands are."

Tom Peters, the FCC official who moderated the panel, stepped in to note that there are many interest groups not represented on the panel and more discussions are likely at a future workshop. Public Knowledge Senior Vice President Harold Feld, who was on the panel, said he was concerned about the Qualcomm comments. “We're talking tradeoffs,” he said. “The thing I find rather startling about Qualcomm’s statement is the idea that no matter what the tradeoffs, it would somehow never work out to use unlicensed use in any of the guard bands, which strikes me as a rather profound feat of technical prognostication at this stage in the development.”

Unless the FCC gets scoring right, the incentive auction is headed for failure, said Preston Padden, head of the Expanding Opportunities for Broadcasters Coalition, prior to the workshop. Padden was one of the experts at the session. “The commission is having a workshop on the band plan and it’s not clear they're going to have the spectrum necessary to even have a band plan,” he said in an interview. “By proposing to score stations based on a non-existent standard and to impose onerous restrictions on sharing stations, the commission is driving away the very broadcasters they need to make this auction work."

Padden said he was in Washington last week for a series of meetings at the FCC and on Capitol Hill on the auction on behalf of the coalition, which represents TV station owners who may want to participate in the auction. “The staff tells us they want to score stations and pay more to big stations and less to little stations, but they cannot tell us what they mean by big and little,” he said. “At one point they had proposed population coverage. They now acknowledge that that doesn’t work, but they have not come up with any standard for the scoring they want to do. They're never going to get the affiliates of the big networks. All their talk about scoring is angering and driving away the very stations whose cooperation they're going to need to make this auction work."

Another big topic at the workshop was whether the FCC should approve a split band plan that divides TV broadcasters around spectrum sold for wireless broadband. Many panelists commented on the band plan proposed by the FCC in its NPRM on auction rules (http://bit.ly/YsPeVr). In January, a coalition representing broadcasters and wireless companies objected to a proposal to put some stations in the so-called duplexer gap, surrounded by wireless operations (CD Jan 25 p3).

"You have to think about TV receivers,” said Brian Markwalter, senior vice president at CEA. “Our belief is it’s going to be very hard to do reception of TV signals when you have wireless broadband on both sides.”

"We really do not like a split band plan,” said NAB Senior Vice President Victor Tawil. “That is a measure of concern.” If “we look at the NPRM plan, there are certainly parts in the duplex gap where you could locate a TV station and still get good intermodulation rejection,” Bergljung said. “However, the entire auction process is based on fungible blocks and that means that some blocks in the uplink may be less favorable in terns of intermodulation.”

"Coexistence issues between two incompatible systems is something not very easy to design a network to,” said Neeti Tandon of AT&T. “That is already in the record.” AT&T has lots of experience dealing with interference in other bands, Tandon said. “The fungibility of the blocks... is very important to us,” she said. “You do want a band plan that is fungible and that is easy to adopt, especially at the regional level."

Panelists also discussed antennas that will be used by mobile devices offered by carriers that buy licenses in the incentive auction. Bergljung said it would be helpful if the entire band used a single antenna. “That promotes interoperability,” he said. Prakash Moorut, senior research specialist at Nokia Siemens, said the FCC’s proposed band plan would require that an antenna work across more than 100 MHz, which would be difficult for a single antenna. “I don’t think we've come out and said it’s not doable,” he said.

"We've talked to some device manufacturers and reviewed the record of the study that was put forward,” said Darryl DeGruy, lead engineer at US Cellular. “It’s going to be difficult to fit additional antenna in a device. So we're more than likely facing a device design that has one antenna.” The band plan proposed by the FCC poses particular challenges, he said. The workshop also explored the benefits and problems of using Frequency Division Duplex versus Time Division Duplex technologies.