Strategies for Securing CBRS 3.5 GHz Spectrum


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Citizens Broadband Radio Service (CBRS) the 3GPP LTE Band Class 48 located at 3.5 GHz (3550-3700 MHz) is ready for shared commercial service. Public and private operators interested in the band should be asking: What spectrum do I need and where? Do I bid for high-cost priority licenses or request inexpensive shared spectrum? What am I willing to pay? How much do I need? What is the best approach?

Answers depend: What do you want to do? Operators have flexibility on what spectrum block(s) to access and where, and more importantly, the cost to secure that spectrum.

CBRS comprises three tiers: Incumbent users, Priority Access Licenses (PAL) and shared General Authorized Access (GAA). Five FCC-authorized Spectrum Access System (SAS) administrators are key to making it all work. SAS’s role ensures that no operator in any tier causes radio frequency (RF) interference to the others.

SAS’s frequency coordination is automated and dynamically manages spectrum sharing. SAS ensures PALs do not interfere with Incumbents and unlicensed GAA users do not interfere with higher tier PALs or Incumbents. Further, SAS can grant access to unused spectrum in any tier.

Consider this strategy: first, obtain GAA spectrum grants in your target area, then bid for PALs.

Say you plan to deploy a Private LTE network in a county adjacent to a metro area. For exclusivity, you could bid for one or more 10 MHz PALs in that county. Before bidding, though, request shared GAA spectrum for the same coverage. GAA utilizes the 80 MHz not allocated to PAL but can access any part of the full 150 MHz CBRS spectrum not already taken or in use.

Unlike county-wide PALs, GAAs are granted on a site/azimuth basis. A service provider or Enterprise can request 10 or 20 MHz of GAA spectrum coverage from its site (vertical asset), for example, in a 90-degree wide sector facing northeast, out to 10 km. If the SAS determines there are no protected devices in the coverage area, it can grant that spectrum. GAA annual fees are expected to run less then a few hundreds of dollars per transmitting radio on the tower.

Then you ask and are granted three more 10 or 20 MHz swaths for each in 90-degree sectors covering all other directions from the same site. Now you have 40-80 MHz of spectrum at very affordable rates.

For expanded coverage in the target area, say you establish four strategic sites, each with 4-azimuth GAA grants per site. This arrangement guarantees 160-320 MHz of spectrum, yet still very affordable.

The idea is to secure as many GAA grants as possible while requests still are relatively few. PAL bids can follow. If you do not win at the PAL auction, you still have spectrum. More important, SAS automatically conducts the necessary RF planning and frequency reuse plan to ensure there are no interference issues in that area. This service saves any operator significant time and expense.

By contrast, 10-year PALs available in upcoming Auction 105, comprise 70 MHz in seven 10 MHz blocks in the 3550-3620 MHz range. PALs are offered on a county level across the 22,000 U.S. counties. Bidders can aggregate up to four PALs for a total capacity of 40 MHz per site in any county.

While each 10 MHz block is exclusive, an operator may need a number of sites using the same PALs to cover a large county. Since that operator only can aggregate up to four PALs, multiple operators could deploy in the same county using different spectrum blocks.

PAL bid prices are expected to range from $0.05 per MHz-POP in rural counties to $0.25 per MHz-POP in dense metro areas with a national average around $0.20 per MHz-POP. Smaller, rural network providers could qualify for FCC bidding credits of 15 and 25 percent. Even so, PALs won’t come cheap.

You can never have too much spectrum. Garnering GAA grants, then bidding PALs, is a strategic approach to having spectrum needed for arising mobile or fixed wireless data-intensive applications.

by John Celentano, Inside Towers Business Editor

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