5G: CBRS license bids top $2.4 billion in FCC auction

The CBRS window is open as bidders battle for choice parts of a unique chunk of U.S. airwaves.

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The FCC's Auction 105 continues into its third week Monday, having sold off more than $2.4 billion worth of priority access to the Citizen's Broadband Radio Service since kicking off on July 23.

CBRS is a hot topic in the wireless world for several reasons, not least of which is its unique three-tiered access system that carries with it the potential for an almost endless array of new services. Enterprises can use the spectrum – which sits between 3550MHz and 3700MHz – to roll their own IoT networks, MSPs can offer various services like smart buildings, and the carriers can fold it into their networks.

The tiered system is what makes CBRS different from other regulated spectrum in the U.S. First, there are incumbent users in this frequency band, most notably the U.S. Navy, which uses it for radar. Incumbents always take priority over other users. The second tier is Priority Access, which is what Auction 105 covers. Priority Access Licenses (PAL) have to accept interference from incumbents, and must not interfere with their signals, but otherwise take priority over the third tier of users, called General Authorized Access. GAA users can still use CBRS frequencies, but have to give way to signals from PAL holders and incumbents.

All of this is managed by a spectrum access system, which is licensed by the FCC but operated by the private sector. The SAS uses environmental sensors to detect signals in a given CBRS access area and assigns channels and prioritizes traffic based on a given user's access tier. At least in theory, this ensures that any kind of CBRS user can access the spectrum without interference, subject to the rules involved.

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