Different shades of spectrum sharing: Mun

“Coordinated” spectrum sharing like CBRS is different from the “dynamic” spectrum sharing method like Wi-Fi. (Pixabay)
Kyung Mun

All spectrum is fundamentally shared – even the licensed bands. 

Licensed spectrum is shared across tens of thousands of radios nationwide and hundreds of millions of mobile users – coordinated by a single operator. Similarly, unlicensed spectrum is shared across Wi-Fi access points and end user devices for example. 

So, why would a mobile operator spend billions of dollars for rights to use a particular spectrum? For example, the ongoing C-band auction is projected to raise as much as $55 billion in winning bids.

Of course, the answer is that operators want to have exclusive use of the licensed bands to control the quality of service. To scale network operation and maintain quality of service, having exclusive use is of utmost importance. In unlicensed operation, there is no guarantee of predictable service quality since a “rogue” device can tap into the same unlicensed band in a given geographic area. It is critical to keep the number of “coordinators” to a minimum – ideally a single entity – to make spectrum sharing effective, especially for wide-area, at-scale networks.

RELATED: With 100,000 CBRS access points already, spectrum sharing is eyed for other bands

When the CBRS spectrum was “born” through the FCC report and order back in 2015, it was touted as an “innovation band” to facilitate spectrum sharing between incumbent government users and private and carrier networks. CBRS, in our view, is the third type of spectrum sharing scheme – “Coordinated” sharing versus:

  • “Exclusive” sharing – licensed spectrum use by a single entity (i.e., a licensee)
  • “Dynamic” sharing – unlicensed spectrum use by a theoretically unlimited number of users (e.g., Wi-Fi, Bluetooth, Zigbee, etc.)

“Coordinated” spectrum sharing like CBRS is different from the “dynamic” spectrum sharing method like Wi-Fi in that the number of entities is limited, and more importantly, the spectrum access is actively managed (through database-driven SAS) so that a potential contention is kept to a minimum and the spectral efficiency is maximized.

The commercial use of the CBRS band has picked up pace since the PAL auction concluded in August 2020. Verizon has been deploying CBRS radios to expand network capacity in targeted macro and small cell sites. Also, both large and small operators are using the band for fixed wireless home broadband services.

Meanwhile, private wireless networks across myriad industries and use cases, ranging from utilities to school districts connecting underserved households, are just now underway. As noted in our recent CBRS Infrastructure and Devices 2020 report, the CBRS equipment market is dominated by the fixed wireless access and mobile broadband use today, with the private wireless segment making up only a mid-single-digit percentage share of the CBRS equipment market. 

While OnGo infrastructure deployments for mobile and fixed wireless use will continue, we see a higher volume of private wireless networks taking advantage of “coordinated” CBRS spectrum access for specific mission-critical enterprise applications needing predictable and secure wireless connectivity. The private wireless segment will make up almost half of the CBRS infrastructure and device market (excluding smartphones) in the next five years in our view.

Mobile Experts chart

For mobile operators managing nationwide networks, traditional licensed spectrum bands like the C-band will remain their #1 priority. Having exclusive access to licensed spectrum will be critical to ensure service quality and to improve spectral efficiency through the latest technical innovations like 5G, massive MIMO, etc. 

For a growing number of private wireless networks that need to support mission-critical applications, “coordinated” spectrum sharing like CBRS provides a better option than relying on “dynamic” sharing in the unlicensed bands without any coordination, which is counter to predictable service quality. CBRS is a good compromise for a growing number of private wireless networks that don’t need to operate at a nationwide scale but need predictable and secure wireless connectivity across larger coverage footprints than Wi-Fi local area networks.

There is a cost to coordination. On one end of the spectrum (no pun intended), there is no monetary spectrum cost for the “dynamic” spectrum sharing in the unlicensed bands. For “coordinated” spectrum sharing like CBRS, the Priority Access License (PAL) spectrum cost can average around $0.22 per MHz-Pop. On the other end of the spectrum sharing range, past licensed spectrum auctions suggest that “exclusive” spectrum sharing can cost 2-5x the average PAL spectrum cost on per MHz-Pop basis. 

There is a clear cost to different spectrum sharing methods. For large nationwide mobile operators, “exclusive” sharing, in which they can be a sole coordinator, is a preferred method. For enterprises seeking private wireless, coordinated sharing like CBRS is an excellent and cost-effective alternative, as compared to purely “dynamic” sharing method in the unlicensed bands.

Kyung Mun is a senior analyst at Mobile Experts LLC, a network of market and technology experts that provides market analysis on the mobile infrastructure and mobile handset markets. 

"Industry Voices" are opinion columns written by outside contributors—often industry experts or analysts—who are invited to the conversation by FierceWireless staff. They do not represent the opinions of FierceWireless.