The Broadband Expo … Connecting Rural America to the World Nov. 1-3, 2010
Wireless Without Limits Cruise Nov. 14 -19, 2010
Mikrotik Users Meeting MUM, Sept. 30, 2010 – Oct. 1, 2010
Do Your Part to Share the Air
What TDWRs Do
49 Terminal Doppler Weather Radar (TDWR) systems are located near U.S. airports to detect severe weather such as sudden updrafts and downdrafts. TDWR information improves aviation safety by allowing pilots to take corrective action and continue safe flight.
TDWR Frequency Range
TDWRs operate in the frequency range from 5600 MHz (5.6 GHz) to 5650 MHz (5.65 GHz). These frequencies are also part of the 5470 to 5725 MHz (5.470 to 5.7525 GHz) band used by outdoor wireless network operators, including many wireless ISPs (WISPs).
DFS
Wireless equipment that operates in the 5470 to 5725 MHz band is required to use Dynamic Frequency Selection (DFS). DFS automatically detects the presence of nearby radar systems and prevents operation on radar frequencies. DFS allows outdoor network operators to share the band with radar systems and not cause interference to (or receive interference from) radar systems.
Recently the Federal Communications Commission (FCC) advised that they are working to resolve interference to TDWR systems from some outdoor wireless systems operating in the 5.4 GHz (5470 MHz – 5725 MHz) band. These wireless systems are required to implement radar detection and DFS functions when operating as a master device and are subject to Section 15.407 of the FCC Rules.
The FCC, Federal Aviation Administration (FAA), National Telecommunications and Information Administration (NTIA) and the wireless industry are working together to develop long-term equipment authorization procedures that will ensure that new wireless devices comply with FCC rules and protect TDWR operations. Manufacturers have an obligation to ensure that their equipment complies with FCC rules and does not cause harmful interference. Section 15.5 of the FCC rules also places an obligation on Part 15 wireless users to avoid causing interference and to correct any interference that may occur. It is incumbent on users to cooperate with manufacturers and to implement any changes necessary to facilitate compliance.
Until the long term equipment authorization procedures are available and in wide use, outdoor wireless operators are being asked to “Do Your Part to Share the Air” by voluntarily avoiding operation on nearby TDWR frequencies.
Do Your Part to Share the Air
Avoiding nearby TDWR frequencies is easy. Check the list of TDWR locations and frequencies. If your base station is NOT within 22 miles (35 km) of a TDWR location, then do nothing. If you ARE within 22 miles of one or more TDWR locations, please exclude any frequencies from your base station with a center frequency that is within 30 MHz of a nearby TDWR frequency. For example, if a nearby TDWR is using 5605 MHz, please configure your base station to exclude any channels with center frequencies from 5575 MHz (30 MHz below 5605) to 5635 MHz (30 MHz above 5605). Soon, an online database will be available to automatically calculate the distance between your base station and nearby TDWR systems. If that distance is 22 miles or less, you will have an opportunity to voluntarily register your base station information in the database. Your cooperation to “Do Your Part to Share the Air” by avoiding TDWR interference will be greatly appreciated by the wireless industry, the FAA, FCC, NTIA and the pilots and passengers flying into and out of your local airport. Thank you in advance for your help. If you need additional information, please contact <junger@ask-wi.com>.
