![]() When we think about this change, we need to remember that the three channels included in the TDWR band represent 60 MHz of bandwidth. Although the new test procedure is still being defined it is anticipated to include additional radar profiles along with more stringent traffic loading requirements.īut what does this mean, especially in terms of 802.11ac? New test requirements mean a new test procedure (and certification) so that access points can prove themselves to detect and avoid radar (of course, this also means firmware modifications and recertification of existing access points). ![]() The primary new requirement is that an access point (or any device acting as a master) must sense for radar signals at 100% of its emission bandwidth (the previous requirement was 80% of emissions bandwidth). The FCC ruling is re-opening the Terminal Doppler Weather Radar (TDWR) band (channels 120, 124, 128) with new test requirements for DFS protection. This is completely understandable and defensible since the TDWR system largely contributes to the safe arrival and departure of commercial aircraft at airports across the country.Īt this point you may be thinking “great history lesson Chris, but what exactly is changing and why should I care?” The bottom line is that the flaws of a distinct minority resulted in the FCC being obligated to forbid wireless equipment operation in the TDWR band for everyone. It’s important to note that “wireless equipment” was not only Wi-Fi. Many of you reading this will recall that the FCC closed the use of the TDWR band several years ago as the result of numerous reports of wireless equipment creating interference with TDWR. If you’re curious for more information on TDWR, then please click here and/or here. In brief, Terminal Doppler Weather Radar (TDWR) “is a Doppler weather radar system used primarily for the detection of hazardous wind shear conditions, precipitation, and winds aloft on and near major airports situated in climates with great exposure to thunderstorms in the United States.” TDWR uses the frequency band from 5600-5650 MHz which is why wireless network equipment needs to be proven to “do no harm” to TDWR. ![]() Hold on, let’s backtrack a bit before diving into what this means: On the topic of interference, a particularly interesting component of the same FCC ruling that opened the U-NII1 band for outdoor AP’s is that it also re-opened the Terminal Doppler Weather Radar (TDWR) band (channels 120, 124, 128) with new test requirements for DFS protection. Therefore, it is imperative that Wi-Fi not create harmful interference to these incumbent systems. It contains incumbent uses that are important for national security and public safety. As mentioned last time, there are significant technical challenges to using the 5 GHz band. In my last blog on 5 GHz spectrum, I discussed the recent FCC ruling that permitted outdoor access points to use the U-NII 1 band (5150-5250 MHz).īut the story doesn’t stop there.
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