On April 17, 2015, the FCC (News - Alert) was expected to adopt rules for new, innovative, spectrum sharing using the 3.5gHz Band. FCC Chairman Wheeler calls it the Innovation Band. The FCC order will open up 150mHz for sharing that is now occupied in part and at various times by Navy radar, fixed satellite services, and fixed broadband.
The 3.5gHz spectrum is located above Wi-Fi 2.4gHz and below Wi-Fi 5gHz. Wi-Fi will not operate in the spectrum, yet. The spectrum is in two separate blocks. A 100mHz block is located from 3550mHz to 3650 mHz (3.5gHz band). And a second 50mHz block from 3650 to 3700 mHz. Selling spectrum licenses in the Innovation Band will be a brand-new, not normal auction.
The FCC is proposing to auction 10mHz blocks for priority use. Each 10mHz channel will be limited to micro-geographies matching U.S. census tract boundaries. The licenses are called priority access licenses, or PALs, and will have priority over unlicensed use but will be subject to potential incumbent access by the federal government. Each of the 74,134 census tract areas contain around 4,000 people each. The normal auction uses 717 cellular market areas, which are many times larger than these small geographies. The FCC proposes a limit of 30mHz for each licensee in a census track.
The principal use for the licensed auctioned PAL will be to deliver backhaul via fixed broadband wireless connections for the carriers’ new small cells that will soon populate our buildings and streetlights. For example, a small cell located on a streetlight may not have fiber available to connect back to the network but could use a 3.5gHz spectrum sharing agile broadband radio to connect the small cell to the cloud network.
The PAL auction will be a major evolutionary step in the FCC’s auction process. Unlike any auctions previously conducted, the FCC PAL auction will limit the license to one year. And unlike any previous auction the license sold will be for 10mHz of spectrum that could be located in one portion of the 3500-3650mHz one day and another portion the next day. The PAL license can be renewed for 5 years but paid for year by year. The FCC has proposed reserving 50 percent of the census tract spectrum for unlicensed use, which means that there will be at least 70mHz sold in each census tract, or 518,938 channels of 10mHz each, an unprecedented number.
Another major difference is that the PAL channels will be subject to inference from high-powered Navy radar that will be moving up and down the coast on ships and turning on and off at different unexpected times. The FCC order will require that the PAL radios connect to a spectrum access system, or SAS (News - Alert), which will direct the agile PAL radios to use different spectrum, or possibly turn off at times if necessary to prevent interference with the government radar. Never before have auctioned licenses been subject too such real-time, FCC-directed control. Using a cloud database modeled from the TV White Space database system, the FCC will dramatically increase spectrum efficiency for carriers and the economy.
There is something exciting about the 3.5gHz spectrum proceedings because the DOD is now supporting the spectrum sharing. The give-back to the U.S. economy, as envisioned in 2012 President’s Council of Advisors on Science and Technology report, is that there will be new spectrum available that has been off limits because of government use. The spectrum will generate auction revenue, deliver advanced SAS, spectrum mask, and sensor technology, and deliver shared but protected use for the mobile industry. When PAL radios are not operational, the SAS will authorize unlicensed broadband radios to operate in within the PAL channel in the census tract, potentially increasing unlicensed use from 80mHz to 150mHz in a census tract when no PAL channels are operational.
While it will be difficult for all the players in the playground to agree that the new rules are beneficial, the 3.5gHz PAL auction is an exciting frontier for opening up locked-up government spectrum.
Edited by Stefania Viscusi