Thus it can happen that only a MAP detects the radar. Unless you are using a dual-backhaul, all your Root mesh APs (RAPs) and Mesh child APs (MAPs) operate on the same channel. "Channel announcement" is a nice feature where the AP tells the client that it is excluding this channel and towards which channel it is now moving. When an AP hears a radar, it will change channel and ban the previous channel for 30 minutes. ![]() DFS in Cisco WLCĭFS is often linked to Mesh but it is simply related to outdoor (or even indoor areas hearing outdoor signals and operating on indoor/outdoor channels). However, some points might be of interest for everyone and are short enough to be briefly explained here below. The following topic are more related to troubleshooting in a Cisco environment rather than explanation about the standard. It then monitors another channel and can start using it after at least 1 minute if no radar was detected. When the radio detects a radar, it must stop using the channel for 30 minutes at least to protect that service. Also, because the energy reflected back to the radar is very weak, it could confuse it with other radio signals (like a wireless LAN to give an example).īecause the 2.4Ghz band is free of radar, the DFS rules only apply to the 5.250 -5.725 Ghz band. Because the energy reflected back to the radar is much weaker than the original signal, the radar has to transmit a very powerful signal. A radar station will transmit a set of powerful pulses periodically and observe the reflections. Radars may be fixed (often civilian airport or military base, but also weather radar) or mobile (ships). We will introduce that after we explain when they come into play. Information can be put in specific elements in the beacon or probe response but a specific frame can also be used to report information: the action frame. ![]() The American Federal Communication Commission (FCC) has now made it mandatory for UNII-2 and UNII-2 extended frequency range like ETSI.ĭFS operations use different ways of exchanging information between stations. It is not necessarily mandatory in other parts of the world and also depends on the frequency range. Therefore scanning parameters are not configurable.ĭFS has been required early on for European Telecommunication Standard Institute (ETSI) devices working in the European Union (and countries following ETSI regulations) in the ETSI 5ghz band. However, the detection itself is mandatory by the regulatory agency and defined clearly. Hence, wrong radar detections can occur and is an art that combines the Wi-fi vendor algorithm with the Wi-fi chip capabilities. The process for a radio to detect a radar is a complicated task that is actually not part of the standard. The general behavior of a device complying with the DFS protocol is to be able to detect when a radar is occupying the channel, to then stop using that occupied channel, monitor another channel and jump on it if it is clear. Now that regulatory agencies are opening those frequencies for other uses (like wireless LAN), there is a need for those devices to operate in accordance of the radars. ![]() In the past, the radars used to operate in frequency ranges where they were the only type of device operating there. Radar stands for “Radio detection and ranging”. ![]() DFS is all about radar detection and avoidance.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |