Despite the high excitement in the US about millimeter wave spectrum, for most mobile services and mainstream devices, the short term focus will be on expanding capacity in the midrange bands. These do not require the same levels of engineering innovation or new regulation to make them practical and affordable for mass market services, beyond the fixed wireless area where Verizon and AT&T are experimenting with high frequencies. But they can significantly add to the device capacity and bandwidth that an operator can support with LTE or 5G (or a combination).
The FCC recently voted to adopt a Notice of Inquiry (NOI) to explore opportunities in spectrum bands between 3.7 GHz and 24 GHz, and initiated comment periods related to three midrange bands – 3.7-4.2 GHz, 5.925-6.425 GHz and 6.425-7.125 GHz. This was the signal for a broad coalition of vendors and service provider to come out of the shadows, aiming to campaign for expanded access for wireless broadband in the 3.7-4.2 GHz and 6 GHz bands.
Founding members of the group – which as yet does not have a name – include AT&T, Verizon, T-Mobile, Google/Alphabet Access, Ericsson, Nokia, CTIA, Samsung, WiFi Alliance, Intel, Cisco, Comsearch, Broadcom, HPE and Information Technology Industry Council (ITI). They hope to build on some of the advances in spectrum sharing, and protection for incumbents, which are being proposed for the 3.5 GHz CBRS band.
In its press release, the ad hoc coalition praised the latest FCC NOI, saying: “We applaud FCC chairman Ajit Pai for his foresight in launching the NOI, FCC commissioner Michael O’Reilly for his recent blog post recognizing the importance of midband spectrum, and commissioner Mignon Clyburn for her support of the NOI and as a long-time advocate for unlicensed spectrum. The FCC’s efforts also align with Senate Commerce Committee chairman John Thune’s statement in a recent letter to Chairman Pai that called for the FCC to begin a rulemaking proceeding focused on opening midband spectrum for both licensed and unlicensed networks.”
Another group, the Broadband Access Coalition, set up in June by over 20 companies, is also focused on midband spectrum, specifically on lobbying the FCC to allow a new, licensed, point-to-multipoint (P2MP) fixed wireless service in the 3.7-4.2 GHz band. Co-founders are fixed wireless vendor Mimosa Networks, the Wireless Internet Service Providers Association (WISPA), Cincinnati Bell, and the Open Technology Institute (OTI) at New America.
Michael Calabrese, director of the OTI, said in a statement that underused satellite bands above 3.7 GHz have “enormous potential” to reduce the digital divided in rural and small town areas, and called for “the immediate sharing of the 3.7 GHz band for high capacity fixed wireless service where trenching fiber is too expensive, and to do so in a way that neither interferes with satellite incumbents nor forecloses the long term potential for mobile use of all or part of the band”.
Such efforts may be helped by a bipartisan effort in Congress to open up more midband spectrum, under the AIRWAVES (Advancing Innovation and Reinvigorating Widespread Access to Viable Electromagnetic Spectrum) Act, introduced by Senators Cory Gardner of Colorado and Maggie Hassan of New Hampshire. This includes a proposal to use some of the proceeds of an auction to fund wireless infrastructure in unserved and underserved areas.
Pai welcomed the Act in a statement, saying: “This bipartisan bill addresses an issue that’s critical to continued American leadership in wireless innovation: making available more spectrum for commercial use.”
The AIRWAVES Act aims to encourage industry and federal agencies to find ways to use spectrum more effectively and lay the foundations for 5G, as well as freeing up more
unlicensed spectrum and address the rural digital divide.
Pai continued in his response: “I’m also very pleased that they have proposed a ‘rural dividend,’ under which 10% of proceeds from spectrum auctions would be devoted to increasing wireless Internet access in rural areas. This provision would go a long way toward closing the digital divide, which has left too many rural Americans in the analog era. I look forward to working with Senators Gardner and Hassan on their forward-thinking legislation.”
Calabrese added: “We look forward to working with the senators to improve the bill’s potential impact on the rural broadband gap. There is an immediate opportunity to share 500 MHz of underutilized satellite spectrum above 3.7 GHz for more affordable rural and small town broadband that will be lost if the sole focus is raising one-time auction revenue that requires clearing satellite incumbents off the band and takes a decade to implement.”
Google is one of the organizations which is studying the satellite spectrum in 3.7-4.2 GHz. Andrew Clegg, the search giant’s spectrum engineering lead, told a recent conference: “We think that point-to-multipoint could be deployed in the band very rapidly even given the existing fixed satellite service earth stations that exist in the band, and that the band could also be used for other things.” Taking part in a panel debate in Washington DC, hosted by the Open Technology Institute, he added: “One of the things to remember here is it’s 500 MHz worth of spectrum in 3.7 to 4.2 GHz – that’s more bandwidth than the cellular, PCS, AWS-1, AWS-2, AWS-3, the 600 MHz and both 700 MHz bands combined.”
Necessary steps, to protect satellite incumbents, would be to clean up the FCC’s existing database of sites in the band, and to adopt a geolocation database to prevent interference and support multiple tiers of access, as in the three-layered CBRS scheme. While that has been ground-breaking in many ways, it is still the subject of controversy. Some companies, such as T-Mobile USA, think the 3.5 GHz band – and its sharing systems, which gives priority to federal incumbent users – should be focused on 5G, not LTE, in line with many efforts in Asia and other regions.
And there are many arguments about how the second tier of access – for operators which will buy spectrum licences at auction – will work in reality. Most of the industry work has been focused on the third tier, unlicensed access, but new arguments are breaking out now, around the auction process.
Mobile operators want conventional licences with long terms – 10 years instead of the three years proposed by the FCC – saying that would encourage investment in networks and services. Other factions want flexible usage in this tier, and two service provider groups, WiFiForward and WISPA, recently commissioned Stanford University professor Paul Milgrom – who devised the process for the recent 600 MHz incentive auction – to outline a new auction structure for CBRS.
In a letter to the FCC, Milgrom argues that three-year licence terms are achievable and a process could be devised which would encourage both incumbents and new entrants to take part. He refuted claims, by some parties, that it would be impractical to conduct a conventional auction because there are so many licences. Echoing comments by Google a decade ago, he suggested a marketplace system, pointing out that eBay can handle one billion active listings at any time. A simple auction process, somewhat akin to that on eBay, could be easy and quick to encourage smaller bidders. He suggests making three-year licences available on a staggered schedule. Licences would “depreciate” periodically by a factor of X and licensees would need to repurchase that fraction to maintain full license rights.
“Even with tens of thousands of census-tract-sized regions, licenses to use the 3.5 GHz spectrum can be sold in a simple and efficient auction, without complexity for bidders or computational burden for the FCC,” he concluded. “The characteristics of the 3.5 GHz spectrum and the FCC’s priority licensing scheme obviate the need for the relatively complex auction designs that have been used to sell licenses for other frequencies.”
Such proposals are partly designed to hit back at proposals from the mobile industry – led by CTIA, GSMA and T-Mobile – to change the CBRS rules. The GSMA joined the debate most recently, but took a similar line to that of the other two – that the focus should be on global harmonization in 3.5 GHz, around 5G. China has thrown its weight behind this as a 5G band, and regulators in Japan, Singapore and Hong Kong are also starting to open up this spectrum. The GSMA also points to plans to auction various airwaves between 3.4 GHz and 3.8 GHz in some European countries, such as the UK, Germany and Ireland.
The GSMA says that adopting the proposals made by CTIA and T-Mobile would have several good effects. It would make the CBRS band’s Priority Access Licences (PALs) available on a ‘Partial Economic Area’ basis (larger than the census tract system proposed by the FCC), with 10-year licence terms and a renewal expectancy. It would also help to harmonize 3.5 GHz band 5G use in the US with other countries.
T-Mobile CTO Neville Ray said on the operator’s Q2 earnings call that he has “huge interest” in the 3.5 GHz band, and that the range from 3.5 GHz to 4 GHz is “the most formative” block of spectrum emerging globally for 5G. He indirectly hit out at rival Sprint, which has said the 2.5 GHz band (in which it has major holdings) is effectively the low band for 5G. “I don’t think about 2.5 that much,” Ray said.
“If you want to talk about where is the most formative block of spectrum emerging globally for 5G, it’s in the 3.5 to kind of 4 GHz range,” he said.
The danger is that, amid all the arguing about rules for CBRS, the opportunity to launch new services will be lost. The three-tiered structure opens doors for new entrants, at least in the general access layer, where a technology like MulteFire (supporting LTE in unlicensed spectrum without a licensed anchor network) could allow enterprises, private network operators and small service providers to support 4G subnets. Although Pai and FCC commissioner Michael O’Rielly have been open about their reservations about the 3.5 GHz “experiment”, the rules were finalized and approved late last year, and that was expected to drive a wave of activity in devices and the geolocation databases. That has been happening, but commercial success may be limited if the FCC is persuaded to revisit the rules.
At a session run recently by the CBRS Alliance in San Diego, O’Rielly said that, since the start of the 3.5 GHz process in 2012, circumstances have changed. “Although many entities are willing to explore unlicensed GAA [General Authorized Access] use, those interested in more extensive, next generation builds require greater certainty that investment would not be stranded, and this is precisely why they want the protections afforded licences,” he said. “To be clear, it is not just the four nationwide wireless providers seeking changes; in fact, I recently met with a mid-sized fixed wireless broadband provider who seeks the same assurances.”
He believes the structure of the auctioned Priority Access Licenses is flawed, based on leading the recent review of the rules. He said: “In conducting this review, I have met with many of the entities represented in this room. While a few said make no changes, many agreed that the PALs could use some serious improvements and one provider wanted a do over to license the entire band.”
He does not want to change the three-tier structure, just ensure each of the tiers works well. His aim is that the FCC should vote on a notice of proposed rulemaking (NPRM) of “proposed enhancements” to CBRS in the fall and finalize them at the start of 2018.