The following Federal Communications Commission (FCC) guidelines required for operation of WLAN systems were created to help mitigate interference to Federal Aviation Administration (FAA) Terminal Doppler Weather Radar (TDWR) from Wireless LAN systems operating outdoors in the 5470-5725-MHz band. The FAA has reported interference to many of their radar systems from WLANs operating specifically in the 5600-5650-MHz TDWR band, as well as from operation of WLANs on adjacent channels.
The FCC, FAA, and National Telecommunications and Information Administration (NTIA) have been investigating the issues, and have reported to industry that the cases of interference stem from many different causes. In addition to temporarily stopping new equipment certification for outdoor devices, the FCC has asked the industry to help address the issue by applying these guidelines to customer installations and ensuring customers are aware of the guidelines and how to comply.
Note: These installation and operation guidelines apply to new systems being installed outdoors as well as current systems already installed and operating.
The following requirements for installation and operation of outdoor systems must be addressed:
1. Operation in the 5600-5650-MHz band is not authorized for 5-GHz WLAN systems, whether operating indoor or outdoors. This does not pose a problem for Cisco® WLAN since this band is not accessible for Cisco products.
Use of indoor-only equipment outdoors can lead to FCC enforcement action, such as fines or requirements to disable the system. This includes installations where the access point is placed indoors and the antenna is placed outdoors, as well as installations involving retractable roofs (for example, football stadiums).
2. For WLAN systems being installed outdoors, the following requirements must be met.
a) Systems must be professionally installed by a qualified engineer familiar with WLAN, including Cisco trained partners and resellers.
b) Operation in the 5600-5650-MHz band is prohibited.
c) It is recommended that the installer register the installation of their system in the Wireless Internet Service Providers Association (WISPA database). This is especially important for systems that are installed within 35 km of the FAA TDWR. (Please see the links later in this document to WISPA database with TDWR locations.)
d) When within 35 km distance of a TDWR, the center frequency of the WLAN must be separated from the TDWR center frequency by 30 MHz.
a. If the radar is operating from 5600-5610 MHz, disable the use of channel 116 (5580 MHz).
b. If the radar is operating from 5630-5650 MHz, disable the use of channel 132 (5660 MHz).
Note: Cisco will be disabling channels 116 and 132 for outdoor systems in the future, the instructions in (d) only applies to systems that currently have the channels enabled.
e) Additional mitigation techniques can include first, not orienting the antennas in the main beam of the weather radar, and second, ensuring that the antenna is not positioned in line-of-sight of the FAA TDWR.
f) Verify that the antennas used are approved for use with Cisco WLAN systems. Installers or operators using nonapproved antennas or making any unauthorized changes may be subject to enforcement action.
In conjunction with industry, the Wireless Internet Service Providers Association (WISPA) has created a database for installers and operators for registration of these outdoor systems including Mesh installations. This database, accessible from the WISPA website http://www.spectrumbridge.com/udrs/home.aspx, should be used by the installer or operator to determine if they are within 35 km of the TDWR, as well as to register the system if operating within this range of the TDWR.
This will help the FCC and FAA address interference issues in the future. Cisco strongly urges our customers to register their outdoor systems in this database:
2. On the main page, select Search at the upper-left. This will take you to the TDWR radar page. Enter the requested information to find the proximity of specific WLAN systems to TDWR systems.
3. If you need to register one or more WLANs, you will need an account. Click the User Signup button on the page and create a registration for your company. There is no charge for registration.
4. Once you are registered user or if already registered log in using your username and password.
5. Select "device management" - to start process to register your device.
6. Enter all information and follow procedure as instructed to complete registration. Once you complete your registration for that device, you can repeat the process for other devices needing to be registered.
Table 1 shows the TDWR information provided by NTIA, this information is here to use as a quick reference, please see WISPA web page for any changes or additions.