Date: Wed, 22 Aug 2012 13:14:13 +0800 From: "Wright, Brett" <Brett.Wright@cooperindustries.com> To: "Adrian Chadd" <adrian@freebsd.org>, "Kim Culhan" <w8hdkim@gmail.com> Cc: freebsd-wireless@freebsd.org Subject: RE: Atheros DFS radar detection Message-ID: <475A4E02EFF4724A9E58F55A56AC13160661E6AC@APEVS1.ap.ci.root> In-Reply-To: <CAJ-Vmon=NfyZW9vJRSNxTLZvJhobeCP-S1O3TxopNzArWunCCQ@mail.gmail.com> References: <CAKZxVQU-%2BW9AP4a9W0PGyLmBOa1GVOrGcLC8bp5zW_=K%2Bv3tHA@mail.gmail.com><475A4E02EFF4724A9E58F55A56AC13160641D618@APEVS1.ap.ci.root><CAKZxVQWeOnw_kZWzuXfHSS-ssQfGVG=ybYK%2B%2B8EaqnFVe-rLpg@mail.gmail.com> <CAJ-Vmon=NfyZW9vJRSNxTLZvJhobeCP-S1O3TxopNzArWunCCQ@mail.gmail.com>
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> -----Original Message----- > From: adrian.chadd@gmail.com [mailto:adrian.chadd@gmail.com] On Behalf > Of Adrian Chadd >=20 > Brett, did you have any luck? >=20 > I'll be in a position to test out with some AR5212 era NICs this week. >=20 > Adrian > Hi Adrian, I have been mucking around with the radar parameters for several days now. In order to get reasonably low levels of false detects I need very aggressive (at least I *think* they are aggressive) values for the radar parameters. For example: FIRPWR: -33 RRSSI: 45 HEIGHT: 28 PRSSI: 22 INBAND: 6 However, the meaning of these parameters is still a little unclear to me. I have read the patent document many times but there is still a lot of information I do not know. I would be prepared to bet that Atheros has documentation describing the above parameters with a lot more clarity. For example , just to pick one of the parameters FIRPWR: According to the comment for this field it is a threshold that the signal power must exceed, but it's default value is -41dBm. Now -41dBm is VERY strong! Also, my experimentally derived value of -31dBm is way stronger still. Certainly in my test environment the strongest signals are around -55dBm (way weaker than either of these values). This really highlights to me that I am "missing" something... Also, the parameter I found makes the biggest difference to my false detects is RRSSI which is "the threshold that the RSSI must exceed when AGC is OK..." etc. Is this a SNR? If so 45dB (my setting for this parameter) with a noise floor around -95dBm would equate to an absolute RSSI of -50dBm. Am I reading this correctly? And if it is an SNR, then why is FIRPWR apparently an actual RSSI (i.e. absolute level). Is everything other than FIRPWR an SNR?=20 Finally, I haven't yet taken the next step of actually injecting radar pulses, but my suspicion is that with such aggressive parameters that actual radar detection according to the regulatory test patterns will fail. I do realize that the difficulties I'm having are due to my lack of information and understanding, however any light you may be able to shed would be greatly appreciated. Thanks=20 Brett
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