CBRS - Citizen's Broadband Radio Service

License Free, Low Latency Private Wireless for Industrial IoT

What is CBRS Band?

CBRS (Citizen’s Broadband Radio Service) is a very large swath of license free spectrum newly released by FCC to promote the development of new applications. The FCC calls it an “innovation band” with the intention that it will ignite the new use cases, like what WiFi did over 20 years ago.

Because CBRS band’s shared access is managed, it provides interference protection. The band access is managed by dynamic Spectrum Access Systems (SAS) administered by many 3rd party commercial organizations. Fig. 1 illustrates the three types of access: General Access, Priority Access and Grandfathered Access.

CBRS band’s managed shared access provides dynamic interference protection among users. Figure illustrates the three types of shared access methods.

  • The General Access is the most interesting. It provides license free access for the widest possible group of users. GA users are permitted to use any portion of the 3550-3700 MHz band not currently used by other users. This license free access is intended to promote the innovation of new use cases.
  • The Priority Access users are like the Business Class on an airplane. They buy licenses on a county-by-county basis. Only seven PALs are issued in any given county, assuring that at least 80 MHz is available to the GA users at any given time.
  • Grandfathered Access users are a handful of Satellite earth stations in USA and their licenses will sunset by 2023.
industrial high throughput transceiver

CBRS Anatomy

The key elements of the 3.5 GHz CBRS dynamic spectrum sharing are the cloud-based Spectrum Access System (SAS), the Citizens Broadband Radio Service Devices (CBSDs), and the End User Device (EUD). The SAS maintains a database of all CBSDs, their geographical location, and other pertinent information. These elements allow real-time knowledge of the spectrum being used at various locations, which helps to manage potential interference.

As required at power up, every CBSD must contact the Spectrum Access System (SAS) over the Internet and receive operating parameters like Channel # and RF power limits. The SAS provides this authorization in accordance with other CBSDs operating in the area. Once the CBSD receives the authorization from the SAS, it then instructs the downstream EUDs to begin their operation. 

high throughput wireless router

Here are some of the salient technical requirements that the CBRS equipment must satisfy –

  • All CBSD must use Time Division Duplex (TDD), Digital Modulation Scheme.
  • Maximum 10 MHz channel size.
  • No airborne applications are allowed.
  • The device category CBSD-A is defined for urban indoor/outdoor use cases and can transmit up to 30 dBm RF power (EIRP, including antenna gain).
  • High powered CBSD-B are defined for rural-outdoor settings.
  • End User Devices can transmit up to 23 dBm EIRP RF power.

Mesh Rider Technology

Mesh Rider is a Doodle Labs patented wireless technology optimized for Industrial IoT applications. It focuses on high speed communication over long distances. It can operate in licensed and license-free bands and can avoid interference. For more details, refer to the whitepaper: Mesh Rider – An Introduction.

Mesh Rider has an Ethernet like flat IP architecture to minimize latency. Mesh Rider borrows on the best features from the LTE and WiFi to provide a state-of-the-art wireless technology. The chart provides a quick comparative look at various technologies available for deploying private wireless networks.

high-throughput routing for multi-hop wireless networks and mimo radio system

Smart Radios for CBRS

Doodle Labs has extended it’s Mesh Rider technology to bring its capabilities to the CBRS band. The Smart Radio platform now supports the CBRS band also.

The CBRS band Smart Radios are an innovative dual role devices. They can be software configured for either the CBSD role or the EUD role to simplify network planning and execution.

The Smart Radios enable organizations to deploy license free private wireless as easily as WiFi. The RM-3625 Smart Radios are fully certified for regulatory compliance. The RM-3625 Smart Radios are per-configured to work with Federated Wireless SAS to make this a truly plug-and-play operation.

Additional Industry Resources

After almost 5 years of planning, the commercial CBRS deployments have just begun in Q1 2020. The industry is excited to take advantage of the opportunities presented by such a large swath of unlicensed spectrum becoming available (For reference, CBRS is 150 MHz while 2.4 GHz WiFi is only 70 MHz wide band). There are many things to learn and many experiences to share. Here we have curated some resources that we think may be useful in your research.

  1. An Overview of the Citizens Broadband Radio Service – Video Tutorial by Commscope (25 minutes)
  2. FCC’s Part 96 governing the use of CBRS band. For most users, the Subparts C and D are most relevant.
  3. CBRS Baseline Specifications Overview – A webinar explaining the details of the CBRS specifications. Wireless Innovation Forum.
  4. CBRS Standards committee – The Spectrum Sharing Committee (SSC) serves as a common industry and government standards body supporting the development and advancement of CBRS spectrum sharing technologies.

Doodle Labs

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