The 2012 President’s Council of Advisors on Science and Technology report strongly encouraged more sharing of federal spectrum as a way to solve our insatiable demand for using wireless to connect. Now, the FCC (News - Alert) in the 5gHz rulemaking is starting to take steps toward efficiently sharing more federal (used by radar) and non-federal (used for satellite communication) spectrum. On March 31, 2014, the FCC made 100mHz more spectrum available for utilization. The 5gHz spectrum includes 5.15-35gHz and 5.47-85gHz.
As users of Wi-Fi know, 5gHz range signals propagate longer distances than at 2.4gHz, delivering lots of bandwidth. But that requires line of sight – in other words, no buildings and no trees. Almost every Wi-Fi router uses 5gHz spectrum now. The IEEE (News - Alert) standards used for unlicensed devices in 5gHz are 802.11a, 802.11n, and 802.11ac. FCC Chairman Tom Wheeler pointed out that unlicensed and licensed are playing well together, making the user experience better and better: "They are less oil and vinegar and more peanut butter and jelly." The FCC's technical solutions, contained in the order, for sharing spectrum in 5gHz are more about creating methods of efficiently using lightly-used spectrum by all users, licensed and unlicensed, and less about a unlicensed versus licensed battle.
In 1997, the FCC gave the name Unlicensed National Information Infrastructure to radios using unlicensed 5gHz spectrum. That was about the same time IEEE was working on making 802.11 a standard for unlicensed wireless local access network sharing and settling on 2.4gHz as the first spectrum to be used. Each part of the 5gHz spectrum has a different UNII band assigned to it for a different unlicensed use.
Licensed users in the UNII band include airport FAA Doppler weather radar that uses 5.250-5.350 gHz and 5.470-5.725gHz. Because the radar helps planes safely use airports, something we all care about, the FCC issued new rules to ensure that unlicensed Wi-Fi outdoor users do not interfere with the radars. In 2009, the FAA discovered that unlicensed broadband radios were open all through the 5gHz band and were interfering with the radars. The new FCC order requires UNII devices to have software that locks the device out of the radar's 5.6-5.65gHz spectrum. Hacking radio spectrum use is now eliminated by software.
The other licensed use is for satellite communications. In 1997, the FCC limited UNII-1 to indoor use and lower power because, five years earlier, 5.096-250gHz had been assigned by the ITU, then followed by the FCC, to mobile satellite service. The unlicensed spectrum allowed use inside buildings but not outdoors. The cable industry wanted to open up outdoor use without interfering with MSS satellite communications. If the UNII-1 and UNII-2 devices could use all the spectrum, the 802.11ac could approach, outdoors, gig Wi-Fi speeds on 160mHz in the bands. Cable companies like Comcast (News - Alert) have deploy more than 100,000 Wi-Fi outdoor access points. This new growth in outdoor Wi-Fi could greatly benefit from using the UNII spectrum. The FCC solved the UNII-1 dilemma by saying that UNII-1 outdoor radios can have an antenna pointing up in the sky as long as the devices operate at a lower power of 250mW (a typical indoor Wi-Fi device uses 50mW of power). If a company, like Comcast, deploys more than 1,000 UNII devices outdoors, the provider is required to notify the FCC and take actions to eliminate interference if found. UNII-1 outdoor Wi-Fi devices could operate at a higher power level, 1W, if the antennas do not point above 30 degrees.
The FCC is moving toward spectrum sharing that will use a database in the cloud to deliver location and power information, just like that used in the lower 700mHz bands. The radio could switch automatically to another available spectrum. The database would automatically inform a MSS or the FCC when more than 1,000 radios are operating and where they are operating, giving enough information to power the radios down, up, or off and protect the safety critical satellite communication signal.
Using a database in the cloud decoupled from the radios, with all radios connected to it, would ensure more efficient use of spectrum than the more manual methods deployed in the new 5gHz order.
Barlow Keener (News - Alert) is the principal with Keener Law Group (www.keenerlawgroup.com) out of Boston.
Edited by Maurice Nagle