Return-path: Received: from mail.neratec.com ([46.140.151.2]:45461 "EHLO mail.neratec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750926AbbCFMZB (ORCPT ); Fri, 6 Mar 2015 07:25:01 -0500 Message-ID: <54F99C9B.7000901@neratec.com> (sfid-20150306_132508_757411_978B4F52) Date: Fri, 06 Mar 2015 13:24:59 +0100 From: Zefir Kurtisi MIME-Version: 1.0 To: Henning Rogge , "linux-wireless@vger.kernel.org" Subject: Re: State of DFS with Mac80211/ath9k References: In-Reply-To: Content-Type: text/plain; charset=utf-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 03/06/2015 09:04 AM, Henning Rogge wrote: > [...] > > Second, we are seeing a huge amount of radar events on some nodes, but > not on a node on the same channel in the next room. What is the status > of the DFS detector in ath9k, is it reliable or is it still > "experimental". > Henning, the DFS detector on one hand still can be labeled as 'experimental' since it seems to be not used / tested all too much. On the other hand, our company got it DFS-ETSI certified for a ath9k based product - so it does what it was made for. As for the 'false' radar detections you observe: those are inherent for the detection method used. The ath9k's pulse detection engine reports anything that somewhat looks like a radar pulse - besides very rare cases where those were generated by real radar, most of them are EM-noise, WLAN traffic, other radio devices. Reality check: let two APs operate close to each other on adjacent DFS-channels, connect one station to one of them and generate continuous downstream traffic (e.g. 10Mbps). It will take only seconds until the other AP will detect a radar - simply because it is inevitable to spot some potential pattern within a lot of random pulses. If you performed the tests in a similar environment, your observation is what you have to expect. And unfortunately there is nothing to be done to prevent the false radar detections - rendering operation on DFS frequencies inapplicable under some environmental conditions. Cheers, Zefir