What is CBRS?

CBRS refers to the Citizens Broadband Radio Service defined by the FCC in Title 47 Part 96 subpart F, which specifies the use of a 150MHz wide block of spectrum 3550–3700 MHz.  This block of spectrum resides within the highly coveted mid-band spectrum, combining high throughput and high propagation through objects such as walls and floors.  In the US, this spectrum has been allocated for LTE and 5G deployments.  CBRS is not a protocol, instead it is a reference to the 3500 MHz band.  An organization known as the CBRS Alliance is dedicated to promoting the development, commercialization, and adoption of LTE solutions for the US 3500 MHz band.

 

While CBRS is a US-specific term, the 3500 MHz band is being considered for use in Canada.  Before jumping into what is happening in Canada, let’s take a moment to briefly explain the CBRS framework in the US.

 

Incumbent users of the 3500 MHz band require protection as new users are licensed.  As a result, there are three tiers of licensees.

 

CBRS Licence Tiers

 

All deployments must be registered with a SAS – either automatically (typically Category A) or manually (typically Category B).  The SAS (Spectrum Access System) is responsible for managing and assigning spectrum on an as-needed basis by registering and authenticating CBSDs.  SASs share information with each other and the FCC databases.  ESCs (Environmental Sensing Capabilities) are used to detect sources of interference and communicate this information to an approved SAS. CBSDs (Citizen Broadband Service Devices) are the devices providing access to end users.

CBRS Framework

There are two categories of CBSDs – A and B.

Category A CBSDs – can be used indoor or outdoor with EIRP limited to 30 dBm per 10 MHz channel.  Outdoor deployments are limited to 6m or below HAAT (Height Above Average Terrain).  Cat A CBSDs may automatically register with a SAS or must be installed by a CPI (Certified Professional Installer) if they are not capable of detecting and identifying their locations automatically (e.g. GPS).

Category B CBSDs – are mostly used for point-to-point or point-to-multipoint.  They must be deployed outdoors with EIRP limited to 47 dBm per 10 MHz channel.  Cat B CBSDs must be installed by a CPI.

End User Devices – must communicate through a CBSD with EIRP limited to 23 dBm per 10 MHz channel.  EUDs are not required to register with a SAS to transmit in the CBRS band.

 

Now that we understand a little about what is happening in the US, let’s uncover what is happening in Canada.

 

3500 MHz in Canada

Currently, use of the 3500 MHz band in Canada is being ‘explored’ via the historical consultation process run by ISED, the regulatory body in Canada responsible for managing spectrum allocation.  Details of the consultation process can be found at the Auction of Spectrum Licenses in the 3500 MHz Band website along with a Table of Key Dates.  Recently, on June 5th, 2020, ISED announced the auction date originally scheduled for Dec. 15, 2020 will be delayed until June 15, 2021.

 

The following policy objectives regarding use of the 3500 MHz band are identified by ISED:

  • foster innovation, investment, and the evolution of wireless networks by enabling the development and adoption of 5G technologies
  • support sustained competition, so that consumers and businesses benefit from greater choice
  • facilitate the deployment and timely availability of services across the country, including rural areas

 

For deployment across Canada, wireless service areas have been divided into four tiers:

  • Tier 1 is a single national service area
  • Tier 2 consists of 14 large service areas covering all of Canada
    • eight Tier 2 service areas that have provincial/territorial boundaries and
    • six that are sub-provincial within Ontario and Quebec
  • Tier 3 contains 59 smaller regional service areas
  • Tier 4 contains the smallest licensing area and comprises 172 localized service areas  
    • current licenses in the 3500 MHz band are based on Tier 4 service areas

 

At the moment, the Canadian band plan for spectrum from 3475-3650 MHz consists of 3 paired 25 MHz blocks and one unpaired 25 MHz block.  Frequency Division Duplex (FDD) equipment was primarily anticipated to use this band, however at present, Time-Division Duplex (TDD) technology is predominantly deployed.  Upon reflection, this makes sense as most 4G and expected 5G equipment is based on TDD. 

 

After consultation with industry and citizens, ISED proposed implementation of new band allocation of 200 MHz using 20 unpaired blocks of 10 MHz from 3450-3650 MHz, providing channel spacing and width to support LTE and future 5G technologies.

 

3500 MHz band from ISED

 

As previously mentioned, incumbent licenses were issued in blocks of 25 MHz.  Moving forward, spectrum allocation may be issued in updated widths as reflected in the table below.

 

Current Spectrum Allocation (MHz)

May apply for (MHz)

>=75

60

50

50

<=25

20

 

The lower end of the 3500 MHz band has been set aside and protected for special use.  The 3400-3475 MHz band traditionally supported radiolocation, primarily with maritime radar.  Even now, there is still maritime radar in use across the US in the 3400-3650 MHz band.  Areas in Canada including cities of Halifax, Dartmouth, Vancouver, and nearby coastal communities may be susceptible to neighbouring interference in this band due to occasional radar use.  The 3400-3450 MHz is used for aeronautical and maritime radiolocation with high levels of confidentiality requirements across Canada and the US.  For this reason, this band is treated separate from the rest of the band. 

 

3500 MHz band from ISED

 

With CBRS in the US, a SAS logs CBSD deployments.  In addition, environmental sensing capabilities (ESC) and CBSD sensing is used to detect dynamic interference.  Once detected, this system re-allocates spectrum to protect incumbents and minimize interference to general authorized access (GAA) licensees.  Details of such a co-ordination system in Canada are yet to be specified, however ISED believes technical measures can be adopted to reduce the impact of any interference and plans to work with the FCC on a new cross-border arrangement.

 

Details that are still outstanding with indications they will be sorted in a future standard include:

  1. Co-ordination procedure between operators and technical limits.
  2. Standard radio system plans (SRSP) for band and related equipment.
  3. Radio Standard Specification (RSS) for band and related equipment.
  4. Technical limits and co-ordination procedures to minimize interference between systems.

 

Slàinte

 

References:

Timetable of key dates for 3500 MHz band

http://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf11586.html

Decision on Revisions to the 3500 MHz Band

https://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf11437.html

Framework for Spectrum Auction in Canada

https://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf01626.html

 

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