FCC unveils rules for Unlicensed 6GHz – ready for WiFi by next year

The FCC has completed a year-long review, whereby it plans to extend US unlicensed bands, ostensibly for WiFi, and will bring a notice of proposed rulemaking to its October 23rd meeting, which will mean 1.2 GHz of extra spectrum can be released for unlicensed use. This almost trebles the amount of spectrum for most WiFi Access Points and chip makers, and software providers will be considering how they take advantage of this in the 2019 time frame.

Assuming the vote goes the way it is expected and there are no dissenting votes, the announcement will likely create an epidemic of copycat regulatory activity across the globe aiming to harmonize 6 GHz spectrum for WiFi, as well as adopt unlicensed usage for both LTE and 5G.

The FCC has identified 4 bands for usage listed at the side.

The two channels allocated for standard power Access Points are essentially outdoor and given how few outdoor APs there are in the US, we suspect that the largest use of this spectrum will be for LTE and in future 5G, using LAA or other unlicensed approaches, with the exception of some WiFi uses in stadiums, shopping malls, universities and campuses. Outdoor WiFi can travel a lot further and has far higher power limits to indoor (about 8 times stronger). And some likely implementations will be using SDN to offer both LTE and WiFi simultaneously, for instance in stadiums – pushing up the capacity that can be online at any point, or far more importantly, bringing down the costs of such installations.

However both of these outdoor segments will need a new mechanism for avoiding devices which are already in these channels – this includes many fixed point to point backhaul microwave cells, as well as Cable Television Relay Service and TV pickup and Broadcast Auxiliary Service. The idea is to create a US-wide map of these installations which will each have a surrounding exclusion zone where an Access Point cannot use key channels. For all Standard power APs, there has to be a lookup process, which either uses GPS to report where it is on a map, and the look-up database then informs it which spectrum it can use for service, or a professional installer has to key in the location data. The FCC has asked for comments and is clearly ironing out the kinks in its plan, while simultaneously powering ahead.

The technical issue here is that GPS is great at telling you where you are on the surface of the planet, but not so great at telling a device how high up it is from the planet’s surface, and height will be a key factor in interference for some fixed and mobile services. For satellite FSS services it doesn’t matter since all signals are at 90 degrees from one another and so interference is highly unlikely. It may be that all outdoor AP installations have to be carried out by certified engineers who promise to transmit its true location to a registered accurate database and get back the permitted channels, but really it is better if this system is automated.

Something very similar has been suggested for CBRS and has been in existence for White Spaces for some years, so the creation of such database lookup sounds quite feasible. There are issues of updating APs in the field when new fixed microwave services are installed, but the AP just needs a new set of spectrum sent to it and its DFS process can repeat and this time ignore any freshly used fixed service channels and there are plenty of channels with 850 MHz in this outdoor space.

But indoors this is looking like a done deal. It doesn’t quite double available spectrum, but it adds 350 MHz to what is probably 455 MHz already in play in 5 GHz, so it’s a considerable upgrade.

The standards committee of 802.11 may have a thing or two to say about how best to “embrace” the new spectrum and channel specifications may change in the coming WiFi standards, but most designs may only need a tweak to their antenna system – if even that, and then can simply search for acceptable channels adhering to the AC and AX standard. The IEEE 802.11 task group already put 6 GHz design into its 802.11AX standard, so pretty much all 802.11AX chips are ready for this move and will need no changes.

Most phones will perhaps need different radio chip to use this spectrum, but it will take chipmakers barely a year to put all this in place and they are doing it anyway for AX so pretty soon all standard phone WiFi chips will be able to take this extra spectrum in their stride. We would expect that home gateways shipping now with 802.11AX will be software upgradeable to this standard when it comes out.

Going back to the outdoor channels, this is a fantastic boost to the 5G brigade. As we know 5G will bring some small benefits in terms of spectral efficiency, an increase of 3 or 4 times, but the bulk of the benefits will come in more spectrum being available. Most people bang on about millimeter wave, but it will take more than a decade to backhaul and install the number of tiny localized cells that are needed for near line of site use of millimeter wave, and most phones won’t even have a radio that can speak millimeter wave for years. The big “con” of the cellular community has always been to take existing 5GHz unlicensed bands, add these 6 GHz bands, along with the CBRS band, and “pretend” this is 5G, so you actually get faster playing videos and such on your phone long before millimeter wave is brought to market in any meaningful way.

Carrier aggregation across 3 or 4 license bands, plus 5GHz, 6 GHz and CBRS will likely take next generation phones to multi Gbps in real performance terms, without millimeter wave. Mostly cellular promises 1 Gbps and all you get is 200-300 Mbps most of the time, but as this spectrum is filled out, and even if it uses WiFi and WiFi offload, phone performance will definitively improve, even if it is not 5G for real.

FCC Chairman Ajit Pai said this week the ruling will be finalized next year.  The Notice of Proposed Rulemaking opens up the 6 GHz proceeding for public comment, but this is being anticipated by the industry and there is very little change likely to the indoor component at least.