FCC Looking at Bandplan Changes Needed in a Broadband World

Despite the changing world, band plans have remained static, Genachowski warned. “There have been some changes of course, but we're still kind of operating in the same assumptions and parameters,” he said. “The world has changed. … How should our thinking around band plans change?” Genachowski noted that some of the first changes will have to come soon for 600 MHz spectrum, as a result of a pending incentive auction of broadcast spectrum. “We're going to have to do a band plan for the spectrum that gets freed up,” he said.

Also on tap quickly could be a new band plan for the 3.5 GHz band, the topic of a pending FCC rulemaking notice, Genachowski said. “We'll certainly raise … the possibility that thinking of 3.5 as a small-cell band could lead to enormous opportunities and create another area where the U.S. leads the world. So that’s another concrete example of where on the spectrum chart your work will have real impact soon.”

Genachowski reiterated there’s been lots of good news in recent years for the U.S. on broadband. “We've now regained global leadership in mobile,” he said. “Everyone around the world is using American operating systems, American apps. … We are on track to lead the world to roll out of 4G LTE at scale. We have 69 percent of the 4G LTE subscribers today, making the U.S. the world’s testbed for 4G LTE.” But “our successes are producing some of our most significant challenges,” Genachowski said. “We have this wonderful demand for high speed, which is incentivizing remarkable innovation on our broadband networks. Well, we need speeds to continue to go up and up and up and capacity to go up. We need to have a world of broadband abundance to maximize the incentive for innovators to continue to innovate.” Smartphones produce a data stream 24 times as big as from a traditional cellphone and, a tablet a stream 140 times larger, he said. “It’s a very real challenge."

"It’s inspiring to see a group of people with disparate interests get together … working hard and solving specific problems,” said Marty Cooper, chairman of Dyna and a TAC member. He was the lead speaker at the workshop after Genachowski, and is best known as the father of the cellphone. “I hope that we're setting an example for the Congress, but I'm not optimistic about that,” Cooper said. People are “fundamentally mobile,” he said. “When we talk about broadband and broadband solving problems, it is going to have to be ultimately wireless broadband and we're going to need multitudes of spectrum at much, much lower costs than we have today.”

Cooper suggested that TAC recommend to the FCC a national, spectrum technology roadmap. “We have to start looking at what is going to happen over the coming years and have the FCC have the tools available so that they can create policy that’s consistent with what’s happening in technology,” he said. Cooper said the TAC should recommend the commission make a push for better measurement of spectral efficiency. “We are getting more spectrally efficient,” he said. “But if we don’t actually measure what we're doing, how will we ever measure whether we're succeeding? How will we ever be able to set goals?” Technology is moving so quickly at this point that LTE will be obsolete in 15 years, Cooper said. “It is going to be replaced by, I predict, whether my prediction is right or not we'll find out, by dynamic spectrum access, which is a combination of all the technologies that we know about."

The workshop offered three panels of experts to discuss technical questions, touching on such issues as optimal channel sizes, the role of guard bands and standard setting. FCC officials asked whether too much flexibility could in some cases slow build out.

Change is Hard

Band plan changes won’t be easy, said Bill Aberth, chief technical officer at Motorola Mobility, who spoke on a panel of LTE trends and their implications for band planning. “Mark Twain used to say, ‘Buy land. They don’t build it anymore,’ and if he were here today he'd probably say, ‘Buy spectrum. They don’t make that anymore,'” Aberth said. “We all would love to be able to take the spectrum and wipe everybody off it and be able to allocate it like we want, make it perfect so that it fits with existing technology. That’s just not the case. We've got legacy deployments [worth] billions of dollars.” Guard bands will remain important, he said. “It takes about 6 MHz to drop a good filter skirt at 700 MHz, and it takes about 12 MHz to drop a good filter skirt at 2.6 GHz,” he said. “You can violate any or all of these numbers, and as you do then we have to get to more esoteric filters, to more boutique solutions and it will force us more towards tunable solutions.”

Al Jette, Nokia Siemens Networks head of North America industry environment, recommended a revised FCC band plan recognize the need to allocate more spectrum to downlink than uplink traffic, reflecting user patterns. With paired spectrum, “if you're allocating a lot more resource blocks for downlink and less for the uplink, you have some uplink resource blocks that just go unused,” he said. “The FCC should look at and study possibly having two or three times as much downlink spectrum as uplink spectrum, and I think that would help operators with their needs today."

"We're seeing a great asymmetry in the demands for the uplink and downlink traffic,” agreed Stephen Wilkus, a member of the technical staff at Alcatel Lucent. A study of a year’s worth of traffic by one of the major carriers found 17-30 times as much downlink traffic as uplink, he said. “We see that there’s this great increased load in the downlink. A few years ago with voice traffic it was [a] one-to-one ratio.” Some application could come along and change things overnight, “but this is a big boat and it’s going to be hard to turn around,” he said. Abert noted that while uplink and downlink data flows are different, neither goes to zero. “If you fire up YouTube and you're watching a concert or something,” he said, “your handset is still firing messages back to the base, acknowledging the packets of data that are received, managing the channel, managing the link and keeping the link alive."

Jette said the growing number of bands being used for LTE could also cause problems down the road. “Different operators throughout the globe, if they've got spectrum they're saying, ‘Gee, we'd like it to be able to support LTE and we want to add a new band,'” he said. Most devices and chipsets are limited 12-14 different bands, he said. “If you start adding more and more bands, it’s going to be difficult to get devices that support all of these bands,” Jette said. “It also would be good if the bands could be more global, instead of ‘Gee, we've got this band for the county of Morocco and this band for the Philippines.'"

Another panel offered operator perspectives on band plan changes. Tom Sawanobori, Verizon vice president of technology, was asked whether band plans should provide more bandwidth for downloads. He noted that mobile VoIP is growing, as are file sharing and use of mobile phones to manage energy use and for mobile healthcare, all of which mean growing uplink traffic. “There’s a lot of different applications that I think will change,” he said. “We need to be flexible.” Sawanobori said a lot of the proposals discussed Monday “take a lot more time and energy to engineer, develop, implement, optimize than sometimes is understood."

The size of spectrum blocks and whether new band plans should allow more flexibility should be based on some practical considerations, said Iyad Tarazi, Sprint Nextel vice president of network development and engineering. “When can you get access to the spectrum?” he asked. “How do you use it? How do you align it with the current spectrum? How do you align it with the global spectrum?” Ultimately, he said, “We do need some flexibility.”

"Given the broadband technologies that we see, we'd like to see a minimum of 5 by 5 [MHz] paired blocks,” said Dan Wilson, principal engineer at T-Mobile. “Anything less than that doesn’t really make sense … going forward with LTE.”

Doug Hyslop, representing the Rural Cellular Association, was asked about geographic spectrum sharing, where some spectrum would be made available only in areas where it’s not used by federal users. Most spectrum carriers use today is available nationwide, “and that fuels an ecosystem behind it, all of the operators are buying common equipment, which works across all of the blocks, so scale is there for the devices and interoperability is automatically built in,” he said. “You need to make sure that those different blocks fit in with some kind of a band class so that equipment can be built within a band class which will cover enough population … so that you have scale.” Small carriers will also need to be able to buy devices that are “interoperable across bands including those that are geographically shared,” he said.

FCC Office of Engineering and Technology Chief Julius Knapp, speaking last, said the workshop took on a number of key issues. “What this is really all about is providing access to spectrum for enabling the growth of broadband wireless services,” he said. “We, together with the NTIA, have been spending a lot of time identifying spectrum bands that could be made available for wireless broadband. We've talked about some of them today, whether it’s 1755 [MHz] or the spectrum that we recover from the incentive auction in the TV bands, 3550, etc. You're moving from the point of just identifying spectrum to start thinking seriously about how do you use it in a way that makes it the most efficient and valuable access for … existing services to grow, new services to be introduced."

Knapp said he couldn’t help thinking “how much simpler it was for analog cellular” more than 30 years ago. “We had one band,” he said. “We worried about out-of-band emissions and we had a bit of spectrum to decide how to divide it in two. It’s just a marvel what the equipment and the networks do today just in coping with all of the different bands that are available and here we are, looking to add more.”