The promise of the USA’s multi-tiered CBRS spectrum band has been discussed for so long that it is easy to forget that there are still no commercial services in the 3.5 GHz band, either in its licensed or shared tiers; and still barriers to full deployment, though most of them are political rather than technical. And with the timing of 5G in shared spectrum uncertain, there is likely to be plenty of time for CBRS to make its mark on the mo-bile services landscape, even if impatience is rising for it to kick off its activities.
So much is riding on the success of the FCC’s bold experiment with opening up a formerly federal band for mobile broadband, with three different levels of priority access – guaranteed top priority for federal incumbents; followed by holders of licences (Priority Access Licensing or PAL); and then by General Authorized Access or GAA – unlicensed, subject to being assigned vacant channels by a spectrum allocation system (SAS), which will manage all the priority levels. Round the world, supporters of a more open ecosystem of mobile service providers, including industrial specialists, are hoping that CBRS will be sufficiently successful to encourage similar schemes elsewhere.
Most focus on the potential opportunity for new mobile entrants has focused on the general access tier, but PAL could also encourage new players, because the licences are likely to be shorter term, and more localized, than most mainstream mobile franchises, and so more affordable for non-traditional MNOs. Wireline or industrial providers have shown interest, since they might want more assured performance and capacity than the shared system would support, but of course, the mobile operators are also keen to snap up the airwaves, to add affordable capacity to their networks, and to fend off those new players.
CBRS Alliance conducts interoperability tests:
As a relatively high frequency band with power limitations, the shared access portion of CBRS will be best suited to small cells and to ‘hotzones’ of urban or rural coverage and capacity, especially indoors. To support scalability, and eventually the potential for nationwide services, interoperability between these networks, and between the SAS systems, will be important.
That is a central remit of the CBRS Alliance, which recently held an interoperability event at CableLabs’ facility in Louisville, Colorado, where over 55 different CBRS combinations were tested. The Alliance said there was a 98% completion rate across all these test scenarios, and no failures – an optimistic sign of a maturing ecosystem. GAA services are expected to start late this year, even while the FCC continues to mull over the final terms and conditions for the auctions in the PAL portion.
The stabilizing of a commercially ready ecosystem in GAA is highlighted by a rising number of FCC certifications for CBRS equipment. Ruckus Networks, now part of Arris, received the FCC’s first CBRS Device (CBSD) authorization earlier this month, for its Q710 and Q910 small cell products.
And last week, Ericsson said it had received this green light for its CBRS portfolio, which include indoor and outdoor small cells under its Ericsson Radio System banner. In CBRS, it offers the Radio 2208 for outdoor and a version of its Radio Dot indoor distributed radio system. The latter is significant, for those supporting new entrants and neutral host models in shared spectrum, because it is built for multi-operator deployment.
Of course, MNOs will use CBRS too, as they are looking to use 5 GHz spectrum for LTE-Unlicensed or LTE Licensed Assisted Access (LAA) in many parts of the world – adding affordable open spectrum to boost their overall airwaves. AT&T recently said it would use Samsung equipment for its initial CBRS fixed wireless deployment, harnessing CommScope’s SAS, and putting in place a migration plan to 5G when shared spectrum standards emerge. AT&T will test CBRS equipment in its labs early next year and plans commercial roll-out in certain US cities from late 2019.
This is an example of using current spectrum and technology for a particular application – fixed wireless – to complement 5G FWA plans in mmWave, and the wireline business.
But some believe the use of shared spectrum will become less necessary in 5G, because there will be higher capacity bands available to MNOs, and early auction results, especially in millimeter wave, indicate their plentiful capacity will make them affordable. This is one factor that reduces the risk, to new open models, that 5G-Unlicensed will not appear for several years, although that also suggests that most of the innovation in flexible and neutral host platforms will take place, for a considerable time, in LTE enhancements.
That is particularly likely, because there has been development of many specialized, vertically-focused offshoots of LTE standards recently, such as LTE-V for vehicles and NB-IoT for low power WANs, and it is unlikely that providers which invest in those now will want to change their technology for at least five years.
Of course, outside North America, those high frequency 5G bands include 3.5 GHz – which in most regions has been mainly used for fixed wireless but will now be a 5G band. Opponents of the flexible LTE framework of CBRS, notably T-Mobile USA, have argued that the FCC has put the USA out of step with the world, and restricted its 5G options, by not also making 3.5 GHz a 5G allocation).