FCC Delivers Regulatory Certainty for Sub-700mHz Cloud-Directed Agile Radios

Wireless Wonk

FCC Delivers Regulatory Certainty for Sub-700mHz Cloud-Directed Agile Radios

By Barlow Keener, Attorney  |  July 08, 2014

On May 14, 2014, the FCC (News - Alert) finally provided some surety for the nascent cloud-directed, agile radio spectrum sharing industry (aka TV white spaces or TVWS) by committing new urban spectrum for unlicensed spectrum sharing use and giving assurance that rural sub-700mHz spectrum would be available into the future.

In 2010, the FCC issued the final database spectrum sharing order, authorizing the use of sub-700mHz (54mHz-698mHz) of spectrum for new agile, flexible radios links controlled by a cloud database. The spectrum was used by TV stations, wireless microphones, public safety two-way radios, and for astronomy. The spectrum was perfect for propagation delivering broadband in urban canyons and basements just like police two-way radios.   

In 2012, Congress ordered, in the Jobs Act, that the commission auction TV station spectrum for mobile use. After the 2012 Jobs Act, the FCC failed to issue definitive rules regarding what would happen with the new 2010 unlicensed spectrum, putting a cloud over spectrum sharing investors and chip makers. The failure to make a decision slowed investment into the industry, putting a drag on U.S. innovation, slowing equipment completion dates, and keeping equipment cost high and out of the reach of consumers. Now, the FCC has acted and provided the needed clarity.

In a recently released summary, the FCC stated it would designate a nationwide of guard band of 14 to 28mHz of spectrum.  This spectrum would be the unused spectrum gap between a 35mHz uplink and 35mHz downlink band to be auctioned for mobile use, a guard band between mobile use and the first TV station in each economic area, and Channel 37 – 6mHz – which is used in various locations for astronomy links to satellites with a 3mHz guard band. The total nationwide spectrum sharing available will be 20-34mHz.

Prior to the FCC order, there was little to no available spectrum in Los Angeles, New York City, Washington, D.C., and other large urban areas because of the number of TV stations in these areas. After the auction, this urban spectrum will be available for spectrum sharing broadband use. Breaking the nationwide spectrum down: the duplex gap is 11mHz between 652-663mHz (Channels 44 and 45).  The TV guard band, depending on the total spectrum in the particular economic area that is auctioned and TV stations moved, will vary between 7-11mHz (located around Channels 31-35).  Channel 37 and a 3mHz guard band next to it will also be available.  

In the near future, 24mHz of spectrum will deliver 100mbps of broadband throughput. Currently, 6mHz delivers 12-18mbps of throughput for a broadband link and 22-25mbps in the future. Using four channels, these radios will be able to deliver 100mbps through urban canyons, buildings, basements, and in rural areas deep into the woods.   Cell phone carriers could use the Sub-700mHz radios for delivering 100mbps of backhaul to small cells into urban canyons. The new nationwide spectrum allocation will open up urban areas for new broadband. 

In rural areas there will continue to be considerable spectrum available for cloud-directed spectrum sharing outside the spectrum auctioned for mobile use and not occupied by TV stations The FCC also set up more database sharing between broadband radios and wireless microphones and with RAS incumbent use. Google (News - Alert), Microsoft, White Space Alliance, and others received most of the minimum spectrum amounts they requested.  The group asked for use of guard bands with at least 10mHz, the use of a 11mHz duplex gap, and one or two channels (6-12mHz) per market for sharing between wireless microphones and broadband operations. 

Cloud-driven spectrum sharing gives the FCC the opportunity to open new available spectrum for use just by feeding the information to approved databases maintained by Google, iConectiv, Microsoft, and Spectrum (News - Alert) Bridge. In the old days, such a spectrum change would require manually changing radios and could take years instead of one day to make good use of the new spectrum. After the auction is completed, TV stations will have 3 years to clear the air and move. It will take many more years for the mobile industry to build out the spectrum it is licensing. 

As long as the spectrum is not used, a situation described by the term fallow spectrum, the FCC should continue to update the spectrum databases showing the spectrum as available for spectrum sharing broadband use.       

Edited by Maurice Nagle