On April 17 the FCC approved the use of a 150 MHz continuous band of spectrum that will be available for public use within the 3.5 MHz band, which they designated as Citizens Broadband Radio Service. This is not necessarily a replacement for traditional CB radio, but that is one of the possible uses of the spectrum.
The spectrum already has some existing users, mostly federal government use of radar and a few users who transmit to and from satellites. These existing users sit in the bands between 3550 and 3650 MHz. Additionally, this new offering will add a 50 MHz band up to 3700 MHz. There are also existing commercial users, including a handful of rural wireless ISPs using the higher end of the spectrum.
The FCC will be implementing a new way to share this spectrum among potential users. They want to implement a two-tiered approach to reduce interference with existing spectrum users. First, a radio that wants to use the spectrum must check with an FCC database to see if there is an existing user in their geographic neighborhood. Second, the radio must use what the FCC is calling ‘sensing technology’ that would first listen to be sure no one else is using the spectrum before transmitting. These two requirements differentiate this spectrum from other public bands used for WiFi where unlimited numbers of users are allowed to transmit simultaneously, and where interference is accepted.
The FCC hopes that this spectrum can support a wide variety of uses such as small cell deployment, fixed wireless broadband, and a category the FCC is calling general consumer use. The spectrum could be used to support CB-like radios, leading to the chosen name of the spectrum block. It’s anticipated that the spectrum could be used by wireless providers to extend LTE. There are already a few users that have been allowed to use the spectrum in rural markets to provide point-to-point data services.
The existing radar is mostly at naval bases near the coast. The FCC is not particularly worried about these bases being affected by the new users since they broadcast high-powered, strong signals. It’s likely the radar sites would overwhelm any attempted commercial use of the spectrum.
This announcement is part of the FCC’s response to widespread request for more public spectrum, and it furthers one of the goals set in the National Broadband Plan to have 500 MHz of spectrum available for wireless data. In many areas, the current public spectrum bands, such as those used for WiFi, are getting congested. At a time when there is a major proliferation of wireless devices and applications in the marketplace, the pressure is going to stay on the FCC to continue to find new slices of spectrum for public use.
There are several steps needed now that this order has been issued. First, somebody must be chosen to administer the geographic database of existing users. Verizon has already volunteered to take that role. Next, the FCC will be issuing a Further Notice of Proposed Rulemaking that will define the specific rules for using the spectrum. There is still a bit of a tug of war going on and the CTIA doesn’t want the spectrum to available to everybody, but the FCC seems somewhat determined on that point. Finally, vendors will need to get radios certified to meet the new requirements. Fortunately, many of them say that they now have radios that meet the expected final requirements.
This is a very interesting spectrum to consider for rural broadband deployment. The operating characteristics of the spectrum provide for long distance transmission and the deployment of significant bandwidth 5–8 miles from a transmitter. Further, it’s unlikely that in rural places there will be other users of the spectrum, particularly if using it for point-to-point connections to customers. Rule-compliant radios for the spectrum are expected to be affordable and this could be used to provide rural broadband links from 20–50 Mbps download. That is pretty good broadband for places that have no broadband alternatives today.