CBRS (Citizens Broadband Radio Service)

What is CBRS?

Citizens Broadband Radio Service, or CBRS, is the set of operational rules given to a slice of the shared wireless spectrum and the technologies used in that spectrum.

An incredible range of wireless technologies is in play in the modern business environment, from purely utilitarian services such as Zigbee and Long-Range WAN to a growing number of client access options that go far beyond Wi-Fi. But CBRS is an access technology of particular interest.

There are two parts to consider when we contemplate CBRS.

First are the operational rules given to a discrete slice of spectrum and the particular technologies used in that spectrum -- frequently referred to as CBRS components. From the frequency perspective, it helps to consider that there are hundreds of frequency bands, including amateur radio bands, FM broadcast bands, various military bands and more. Each covers a range of frequencies and may overlap or share frequencies with other bands. CBRS, as a spectrum band, occupies a 150-MHz-wide swath from 3.55 GHz to 3.7 GHz in the United States. Sometimes CBRS is used interchangeably with 3.5 GHz band and innovation band.

Second, there is the technology that works in the CBRS spectrum -- the CBRS gear and applications. This is where private cellular networking lives, with companies able to deploy their own 4G or 5G mobile networks for various applications and access use cases, abiding by CBRS rules of use set forth by the Federal Communications Commission (FCC).

How does CBRS work?

To answer that, we need to be specific about each aspect of CBRS. In the spectrum domain, CBRS must carefully participate in spectrum sharing, as there are other users of the same frequencies. These users are geographically scattered with enough lack of density that the FCC felt it was worth also letting CBRS share the spectrum with some safeguards in place. CBRS needs to fit into this spectrum-sharing framework as part of the 3.5 GHz frequency ecosystem:

• Incumbent users. These longtime users of the 3.5 GHz band include military radars, satellite services and some wireless ISPs. These are the highest priority users in the band, and other services like CBRS need to plan their channels to not interfere with the incumbents.
• Priority Access License users. The FCC devised a system whereby so many licenses for 10 MHz channels in each U.S. county could be bid on. It's a complicated topic, but PAL users must not interfere with incumbents, and General Authorized Access (GAA) users must not interfere with PALs or incumbents. PAL is higher priority than GAA and lower priority for spectrum use than incumbents.
• General Authorized Access. This is where CBRS can be found, and individual CBRS-enabled networks do not need to be individually licensed if the equipment in use conforms to FCC rules for CBRS. But CBRS radio access hardware does connect to a back-end system that automatically prevents their channels from stepping on higher priority users in the band based on specific location. It's all highly variable, based on local and regional activities in the U.S. with incumbents and PALs.

Despite the complexity, so far the framework works well.

CBRS equipment, regardless of specific technology in play, also has limits on output power levels for both indoor (1 W) and outdoor (50 W) use. Aside from the regulatory workings, the "how" of CBRS is dependent on what technology is used in a given deployment -- usually 4G LTE or 5G.

Use cases and benefits of CBRS

The use cases for CBRS are potentially endless, as long as there are client devices compatible with the 3.5 GHz band. CBRS is generally contention-free compared to Wi-Fi that operates in unlicensed bands, which are fraught with competing technologies.

Wi-Fi in a crowded stadium can be an unpredictable train wreck due to various interference sources and countless hotspots in fans' pockets. In the same environment, CBRS has the luxury of no spectral competition and greater efficiency in handling many users. Thus, it is a great application for point-of-sale terminals, facility operational communications and even portable video applications.

In large production facilities such as factories and distribution centers, Wi-Fi may be challenging due to the size of a given building. Even fiber optic cable can only be run so far for connecting switches to 802.11 access points. CBRS equipment, on the other hand, covers a larger area while typically providing lower latency and more reliable service-level agreements for machines, robots and vehicles like forklifts that need network connectivity.

Essentially, any vertical can make use of CBRS if it makes economic sense. Enterprise equipment is based on requirements, so in some situations CBRS will be the best fit for access and security. In other situations, CBRS would be an expensive solution looking for a problem. Though the OnGo Alliance -- formerly the CBRS Alliance -- frequently positions CBRS as a complement to Wi-Fi rather than a replacement, not every enterprise will be able to afford both systems.

CBRS vs. LTE vs. 5G

It can be hard to keep the various cellular technologies straight, but for CBRS remember that it's all about frequency. CBRS is in the 3.5 GHz band, period. When used outside of the CBRS framework, 4G LTE and 5G are supported in a wide range of discrete licensed frequency slices that start below 1 GHz and range all the way up to 40 GHz. Each band has its own operational characteristics for LTE and 5G, and not all client devices support all of the allowed bands. CBRS equipment can include LTE and 5G for private cellular networking. Alternatively, Verizon, AT&T and T-Mobile, for example, also use LTE and 5G for public carrier networks.

Total cost of ownership

When it comes to CBRS adoption for private cellular networks, there is no free lunch when it comes to installation of the various components. From access point hardware in the radio access network (RAN) part of the system to the rack-mounted nodes that go in the telecom closets, CBRS brings new power, cabling and cooling costs that must be considered when budgeting for the system. In this regard, CBRS is no different than Wi-Fi, with the exception that not as many RAN devices are needed for CBRS compared to Wi-Fi access points in a given area.