FAQ: What in the wireless world is CBRS?

Explainer on the Citizens Broadband Radio Service (CBRS) shared spectrum in the 3.5 GHz "innovation band"

FAQ: What in the wireless world is CBRS?
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First off, CBRS is an acronym for Citizens Broadband Radio Service, and the upshot for IT pros is that it could enable enterprises to build their own private 4G/5G networks and result in improved 4G/5G offerings from service providers. Here’s a primer on CBRS — because you are going to want to know about this.

Citizens Band/CB, as in CB radio?

No, good buddy, this has nothing to do with the Citizens’ Band radio service used by truckers for two-way voice communications and that lives in the 27MHz band in the U.S.  CBRS lives in the 3.5GHz band.

What is CBRS then?

CBRS is a band of radio-frequency spectrum from 3.5GHz to 3.7GHz that the Federal Communications Commission has designated for sharing among three tiers of users: incumbent users, priority licensees and generally authorized, which is unlicensed.

The incumbents are those who have historically held exclusive rights to the band: satellite ground stations and the Navy. Priority licenses will be auctioned off June 25 and will allow licensees to use the band in particular U.S. counties so long as they don't interfere with the incumbents and tolerate interference from the incumbents. Generally authorized access gives users the right to use the band as long as they don't interfere with the other two categories of users.

Who's making sure there's no interference among users?

A network of sensors – the Environmental Sensing Capability (ESC) – detects use of CBRS. Devices that want to use the CBRS band put in requests to a cloud-based Spectrum Access System (SAS) to reserve unused channels in a particular geographic area. If channels are free, SAS can grant the requests. When devices with permission to use channels are done with them, they are put back into the pool that the SAS can draw from to grant further requests.

How did the 3.5 GHz band suddenly become available for new commercial services? Isn’t spectrum a super scarce resource?

The freeing up of the 3550-3700 MHz band stems from the 2010 National Broadband Plan issued by the FCC, which set out to make 500 MHz of additional spectrum available for new mobile uses. The FCC zeroed in on the 3.5 GHz band (which has dubbed the "innovation band") in rules issued in April of 2015, then reaffirmed those rules about a year later. In the meantime, it has worked out the details of implementation.

So who’s going to use this spectrum?

Carriers look forward to using it to extend coverage and capacity of their 4G LTE and 5G networks. As we know from their efforts to horn in on the 5 GHz band used for Wi-Fi via a technology called LTE-U, carriers seek access to more spectrum. But cable operators looking to get into wireless also want in on this action, as will assorted managed service providers, which could include building management companies. What’s more, enterprises could use the spectrum to set up their own 4G and 5G networks with which they could connect their IoT devices. Including. The services work both indoors and outdoors.

What sort of applications will CBRS be used for?

Service providers are expected to use CBRS to replace last-mile fiber access, deliver fixed wireless services and even point-to-multipoint offerings. Enterprises and managed service providers could exploit it for IoT connectivity and even for Wi-Fi replacement or supplementary services. LTE services could hit 1Gbps indoors and maybe 5 or 10 times that for outdoor uses with line-of-sight access. 5G could be 10 times LTE.

How expensive is it?

CBRS backers say the economics of this technology are much better than those of distributed antenna systems, and they contend the speed and consistency of service will be much better than Wi-Fi. CBRS supporters also say imaginative new services will be enabled by the availability of more cheap spectrum. Federated Wireless has introduced a 4G/5G service being sold through AWS and Microsoft Azure as connectivity to the cloud. 

Where will software, equipment and services come from to support all this?

Here’s one clue: Almost 40 vendors, from the Big 4 carriers to service provider equipment vendors Ericsson and Nokia to enterprise equipment companies like Cisco and Ruckus to chipmakers like Intel and Qualcomm have banded together in the CBRS Alliance. Look for smartphone and computer makers to join too, once carriers make their requirements clear. Samsung already belongs to the CBRS Alliance.

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