Update: 3550-3650 MHz Replies Extended to August 15

No need to read the post; the headline says it all.

A recent item in in our series of posts on the FCC’s novel spectrum-management proposals for the 3550-3650 MHz band (and possibly 3650-6700 MHz as well) told you the reply comment date was … well, it doesn’t matter what we told you, because the FCC has now extended the reply comment date to August 15.

Resume your vacation.

Update: Comment Deadlines Set in 3.6 GHz Citizens Broadband Radio Service Proceeding

Back in April we reported on a sweeping Further Notice of Proposed Rulemaking (FNPRM) on the evolving creation of a Citizens Broadband Radio Service in the 3.5 GHz band. The proposal incorporates a new approach to how the world might handle spectrum use, including on-the-fly frequency coordination with priority up for sale via auction. The FNPRM has now been published in the Federal Register. As a result, we know the deadlines for comments and reply comments directed to the FCC’s proposals. Comments are due by July 14, 2014 and replies by August 1. Anyone wishing to comment now may do so by uploading their submissions in Proceeding No. 12-354 at the FCC’s ECFS filing site.

FCC Proposes New Approach to Spectrum Management

Out for comment: The Citizens Broadband Radio Service for the 3550-3650 MHz band, featuring multiple priority levels, an annual auction, and an unprecedented Spectrum Access System.

As we have known for years, the FCC – and the rest of us – face a daunting problem: too many spectrum users and not enough spectrum. Even the most ambitious reallocation (and associated re-packing) plans offer at most limited and impermanent responses to the problem. Now the FCC has a new idea that could completely remake how the world handles spectrum and, in the process, dramatically increase the efficiency with which spectrum is used.

But the FCC’s plan to create a new “Citizens Broadband Radio Service” (CBRS) in the 3.5 GHz band sure has a lot of moving parts.

The plan is, in a way, simplicity itself: it calls for spectrum users to take turns. But while the basic concept may be kindergarten simple, its implementation is not, by a long shot. After all, not all users’ communications are equally urgent or important. Is there a way to get the more urgent and important stuff through first, and still give everybody else a fair shot?

After a year and a half, a previous Notice of Proposed Rulemaking, a follow-up public notice, hundreds of comments, two full-scale workshops, and too many meetings to count, the FCC has come up with a highly promising approach that is almost ready to test.

The CBRS would be established at 3550-3650 MHz, possibly combined with the adjacent 3650-3700 MHz band. This is an odd choice, at first glance. The incumbents at 3550-3650 MHz are high-powered ground and airborne military radars, and earth stations that receive satellite signals – on the face of it, poor candidates for sharing. The 3650-3700 MHz segment is widely used for delivery of commercial broadband service. Both bands have long been regarded as so sensitive that they are closed to most unlicensed devices.

The FCC nonetheless thinks it has a way to introduce new users to these frequencies without causing interference either to incumbents or to each other. The details appear in a Further Notice of Proposed Rulemaking (FNPRM).

Like an earlier plan, the proposal would establish three priority levels to govern access to the shared spectrum – but there the similarities mostly end.

The new plan would give the highest priority to Incumbent Access (IA) use. As the name suggests, IA would be limited to incumbent users. They would be permitted to operate at any time, and would be free to cause interference to anybody (except, in some cases, to each other). They would also enjoy protection against interference from everybody else, using geographic “exclusion zones” within which no one else could operate on the incumbents’ frequencies.

Next in the pecking order would Priority Access (PA) use. PA users would have to protect the incumbents, and would in turn be protected against interference from General Authorized Access users (discussed below). PA use would be auctioned in ways that are novel for the FCC. Auction areas would be small census tracts – about 74,000 of them nationwide, each with only a few thousand people, generally following political boundaries such as city lines. Each auctioned license would cover 10 MHz and be valid for only one year. Bidders would be free to aggregate licenses so as to cover a greater geographic area, or more bandwidth (up to 30 MHz) or more time (up to five consecutive years in a single auction). The FCC would conduct auctions for the entire system annually.

The lowest priority would be General Authorized Access (GAA). GAA use would provide access, free of charge, to spectrum not occupied by the two categories above. How much spectrum remains available for GAA will depend in part on the success of the PA auctions. But the FCC proposes limiting PA auctions to no more than 50% of the bandwidth in each census tract, after accounting for the incumbents, with the other 50% reserved for GAA. Still, because multiple users may compete for that 50%, no single user could be assured of getting a signal through quickly.

Certain “critical facilities” such as hospitals, public safety organizations, and local governments would get an advantage: they could reserve up to 20 MHz of GAA spectrum, but for indoor use only. Other GAA users would not be permitted to operate on those frequencies in those buildings. The FCC expects the building walls to largely isolate the users in these critical facilities from the great mass of other GAA users outside.

The key to making all of this work is a Spectrum Access System (SAS) that, as envisioned by the FCC, will manage all users (except the incumbents) on the fly, in real time. Every device will have to check in with the SAS, report its own location, request permission to transmit, and wait to be assigned a specific frequency. The SAS’s job will be to keep everybody off the incumbent spectrum in the exclusion zones, prioritize PA users, and assign GAA slots to others. Although a PA license would entitle the user to 10 MHz (or more) at any time, it would not specify a particular slot. For maximum flexibility, the SAS would be able to move each user’s actual operating frequency around in the band as needed.

The proposed technical rules are complex; those interested will have to plow through the FNPRM. Power limits will be higher in rural than in non-rural areas, and higher still for fixed systems, ranging overall from 1 watt up to 200 watts EIRP. But tighter controls will apply at the boundaries of a license area. A licensee that buys just one or a few census tracts will often be close to a boundary, and so in practice may have less power available. Presumably the SAS will set power so as to protect the boundaries.

Taken together, the technical demands on the SAS are unprecedented. The FCC describes it as an extension of the database that controls TV white space devices, but the tasks that would be assigned to the SAS would be vastly more complex. The design and operation of a successful SAS will be a major technological achievement.

All of these considerations listed here, plus a great many more, are open to comment.

Of the FCC’s earlier proposal for the 3550-3650 MHz band, we said, “Not content with crossing that tightrope, the FCC wants to juggle at the same time.” Now it wants to do the whole thing balancing tiptoe on a unicycle. But if the FCC and its industry participants can bring this off, and then extend the same ideas to other bands, the day when we finally exhaust the spectrum may not come as soon as we had feared.

The deadlines for comments have not yet been established. Check back here for updates. Anyone wishing to comment now may do so by uploading their submissions in Proceeding No. 12-354 at the FCC’s ECFS filing site.

FCC Calls for Technical Papers on 3550-3650 MHz

Public is invited to help design a novel, on-the-fly frequency coordination system.

The FCC wants your help in designing its on-the-fly frequency coordination system for the 3550-3650 MHz band – a concept that has the potential to remake spectrum management for many other bands as well.

The central idea is to establish priorities among user groups that a “spectrum access system” enforces automatically in real time.

The FCC first floated the idea in a Notice of Proposed Rulemaking almost a year ago, and more recently refined its ideas in a highly detailed public notice. It announced (and then rescheduled) a workshop to discuss the public notice, now set for January 14.

And it has now issued a call for technical papers to be discussed at the workshop.

The request for papers is detailed and specific. We urge interested persons to consult it directly.

The deadline for papers to be considered in connection with the workshop is January 3, 2014. File submissions in GN Docket No. 12-354.  (You can do that through ECFS.) The FCC has promised to release an agenda prior to the workshop.

The requested papers, the workshop, and comments on the above-mentioned public notice will all help to form the basis of a forthcoming Further Notice of Proposed Rulemaking. But don’t count on waiting till then to change the FCC’s direction. If you have ideas on how it should proceed, submit them now.

New Date for FCC Workshop on 3550-3650 MHz

Event is rescheduled to January 14.

The FCC has rescheduled a workshop on proposed technical requirements, architecture, and operational parameters for the 3550-3650 MHz band. Originally set for December 11, the event is now on for January 14.

We originally posted on the workshop here, giving the old date. Now that the FCC has released a public notice that considerably revises and expands its original proposals, the workshop should take on added interest for those interested in the band.

Update: FCC Seeks Further Comment on 3550-3650 MHz

Public notice lays out ideas based on industry responses so far.

We reported a year ago on the FCC’s novel proposals for spectrum management in the 3550-3650 MHz band.

Following the receipt of comments and a workshop, the FCC is rethinking the details. Its evolving ideas, on which the FCC requests comment, are set out in a public notice.

Ordinarily at this point in a blog piece, we would summarize the public notice. Not this time. It runs to 18 single-spaced pages and is dense with information; an accurate summary would be almost as long as the document itself. We recommend that interested persons consult the public notice directly.

This is not the last word. The FCC has signaled that the next stage will be a Further Notice of Proposed Rulemaking, before it proceeds to adopt rules. Usually, this sequence means the FNPRM will be largely a formality, setting out whatever rules the FCC expects to adopt. Those who want to affect the course of the proceeding should consider submitting their views in response to the public notice.

Comments are due by December 5, 2013 and reply comments by December 20. File in GN Docket No. 12-354.

FCC Announces Workshop on 3.5 GHz Proposal

Session will explore technologies to govern interactions between and among devices.

Those interested in the FCC’s novel, on-the-fly spectrum management system proposed for the 3.5 GHz band may be interested in an FCC workshop, scheduled for December 11, on the technical requirements, architecture, and operational parameters of the system. Details are here.

Update: Reply Deadline Extended in 3.5 GHz Proceeding

Postponement allows time after March 13 workshop.

Last December we reported on a proceeding that proposes novel spectrum management techniques to accommodate small cell operation in the 3.55-3.65 GHz band.

The FCC has moved back the due date for reply comments until April 5. This will allow time for reflection following the FCC’s public workshop on the 3.5 GHz issues to be held on March 13.

Brave New Spectrum World: Proposal Would Accommodate Many More Users in a Sensitive Band

The FCC has proposed an innovation that might vastly increase the ability of multiple users to share the same band.

The FCC has proposed a set of rules that look innocuous enough, and would apply only to a single, underused band. But they may herald a new way of managing spectrum – a suite of techniques having the potential to vastly increase the number of users that can share a given range of frequencies.

All of the radio spectrum is occupied – at least, all of the most useful parts, below about 60 gigahertz. But the demand for spectrum continues to increase. What the FCC needs most is a way to squeeze new users into spectrum that is already in use, without causing interference to either the incumbents or the newcomers.

Current spectrum management relies on “allocating” each band of frequencies to (usually) several categories of users. Those categories, in turn, come in three different priorities. Those designated as “secondary” may not cause harmful interference to, and must accept all interference from, those called “primary.” Unlicensed users, permitted in most bands, must protect all other users (except each other) from interference, and must accept all interference that comes their way. A few bands, like that used for GPS reception, have only one active user category; a few have as many as seven or eight. Three to five is about typical.

Yet even supposedly occupied spectrum is quiet in most places, for much of the time. Some services, like those using two-way radios, occupy their frequencies only sporadically; others, like some types of satellite earth stations, operate only at wide separated locations. All such users, however, vigorously resist letting others into their bands. A police officer at the scene of an accident, picking up his microphone to request an ambulance, hopes to find an empty channel to make the call. The satellite operator may want the option of installing earth stations at new locations, without interference from other kinds of transmitters nearby.

As we explain below, the FCC thinks it can fully protect all such users while still letting new entrants share the same frequencies.

It proposes a scheme that prioritizes some classes of users over others, and – here’s the hard part – implements those priorities in real time, automatically, on the fly. A good trick, if the technology can be made sufficiently reliable.

This is not the FCC’s first foray into technical rules meant to protect users from each other. Unlicensed transmitters in the 5.25-5.35 and 5.47-5.725 GHz bands are required to sniff the air for certain radars, including those that detect adverse weather conditions at airports, and must avoid transmitting on radar frequencies in use. (In practice, though, sometimes even compliant equipment causes interference.) Similarly, the unlicensed “white space” devices that operate on vacant TV frequencies must avoid interfering with TV reception, some wireless microphones, and many other services. The rules for white space devices are complex, requiring self-geolocation, use of a central database to identify locally non-interfering frequencies, and spectrum sensing. Large-scale deployment having just begun, the jury is still out on how well the techniques will work in practice

Now the FCC proposes an ambitious expansion of these ideas. Its test bed is the 3550-3650 MHz band, possibly combined with an adjacent band at 3650-3700 MHz. Current users of 3550-3650 MHz are high-powered ground and airborne military radars, and non-federal earth stations that receive signals from satellites. Both of these applications are ordinarily ill-suited to sharing. Typically a radar combines a high-powered transmitter with a highly sensitive receiver, and is thus prone to both cause and receive interference. Downlink earth stations are also sensitive, as they must receive useable signals from tens of thousands of miles away. The 3650-3700 MHz segment is widely used for delivery of commercial broadband service. Both bands are part of a larger swath that the FCC has long kept closed to most unlicensed devices, out of interference concerns.

In short, this is not the first part of the spectrum one might look to for additional sharing.

Not content with crossing that tightrope, the FCC wants to juggle at the same time. It proposes to add in new users having urgent communications needs: hospitals, utilities, state and local governments – not usually good candidates for already-occupied spectrum. These will implement “small cell” applications; think of Wi-Fi service, but with better coverage at specific locations. Other new users are expected to offer additional small cell services over areas such as homes, office suites, stadiums, shopping malls, hospitals, and parks. These might be set up by consumers at home, by the management of a mall, say, or by a service provider trying to improve coverage in hard-to-reach places.

All such users will be “licensed by rule,” a legal fiction that entails no actual applications or licenses. This means the FCC will have no record of where the devices actually are. If one of them does cause interference, there will be no way of tracking it down.

The scheme rests on three levels of priority, comparable in some ways to the classic primary, secondary, and unlicensed partitions.

The highest priority, called “Incumbent Access,” consists of the federal radars and satellite downlink earth stations already in the band. Other users would be excluded from regions where they could cause interference to these facilities. Additional precautions, described below, would apply outside those regions.

The second level, called “Priority Access,” includes qualified users needing certain levels of service quality, like the hospitals and utilities mentioned above. Each of these users would be permitted to operate only in a specified geographic area: a utility, for example, might be restricted to regions where it provides service. The FCC expects Priority Access usage to be primarily indoors. These users might have access to half the band, leaving the other half for lower priority users. But no operation would be permitted in areas where the devices might cause interference to, or receive interference from, the Incumbent Access users.

The lowest priority, “General Authorized Access,” would comprise use by the general public. These operations would have to avoid causing interference to the other two categories and accept any interference received.

Keeping track of these levels and locations would be a “spectrum access system,” an ever-changing database that all Priority Access and General Authorized Access devices must consult on when, where, on what frequencies, and at what power they can operate. Devices would use geolocation (presumably via GPS) to report their whereabouts to the database. In some respects this system would be modeled after the database used to control white space devices; in practice, it might be an extension of that same database.

The FCC is considering whether to include the adjacent 3650-3700 MHz, which has been the topic of some controversy. Among other users, that band houses self-coordinated fixed links at more than 25,000 sites. But there is no proposal to explicitly grandfather these; instead, current users in the band might have to transition to operate under the new rules.

The FCC requests public input on all of the above, and on many possible variations. The Notice of Proposed Rulemaking is complex. Those interested should give it careful study. Comments are due on February 20, 2013, and reply comments on March 22.