From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail2.candelatech.com ([208.74.158.173]) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1Zz65Y-00007b-I2 for ath10k@lists.infradead.org; Wed, 18 Nov 2015 17:00:09 +0000 Subject: Re: TX-Power limits for ath10k based card on Linux 3.18.24 (offlist) References: <018201d12175$a4604d80$ed20e880$@tranzeo.com> <898991972.6790146.1447837274772.JavaMail.yahoo@mail.yahoo.com> From: Ben Greear Message-ID: <564CAE82.3090908@candelatech.com> Date: Wed, 18 Nov 2015 08:59:46 -0800 MIME-Version: 1.0 In-Reply-To: <898991972.6790146.1447837274772.JavaMail.yahoo@mail.yahoo.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "ath10k" Errors-To: ath10k-bounces+kvalo=adurom.com@lists.infradead.org To: Joerg Pommnitz , Michael Rex , "ath10k@lists.infradead.org" Cc: =?UTF-8?B?J01pa2UgSmFlY2tlcicg4oCO4oCO?= , Michael Schaefer On 11/18/2015 01:01 AM, Joerg Pommnitz wrote: > Michael, Ben, > thanks for the illuminating answers. From Michaels latest reply I gather that the hardware is actually capable of transmitting with full power on a single chain/antenna, but that the current firmware or driver limits the tx power on a single chain in a way that makes sure that the combined tx power of all available chains is within the regulatory limits. Is this correct? > What would it take to enable full tx power for a single chain? My firmware should at least ask the hardware to transmit at full requested power on a single chain when using legacy rates (or 1x1 HT/VHT rates). I think you need to test with fixed rates so that you know what rate you are sending, and make sure you are 99%+ duty cycle so that you can trust your measurement tools... Thanks, Ben > > -- Regards Joerg > > > >> Michael Rex schrieb am 21:22 Dienstag, 17.November 2015: >>> Ben, >> >> That is definitely a good way to do it. That seems to be the way lab >> engineers have been configuring ART during the tests, but as you can see >> from Compex datasheet, they are marketing the combined power of 2 and 3 >> chains, not making them the same regardless of chains. So they are marketing >> it higher than their approved certificate says... I think nearly all MFG's >> are doing that 'false' advertising. Well, perhaps maybe not your >> customer >> who went through approvals... >> >> Since an individual chain is capable of full power, and companies want to >> market and sell the highest power, I think it would be better (better >> meaning max power achievable) to allow all 3 chains to go full power rather >> than 1/3 power, but it would have to be done in time for the certification. >> Not sure how complex the code would have to be to allow both methods of >> target power setting, but you're kind of stuck for the people who already >> approved on that driver behaviour. It probably would increase power density >> and other things and perhaps fail unless target power decreased to pass the >> limit. >> >> Hard to say which way is better, but your method is the safer method of >> passing approvals. Given the expense of approvals, having it pass first try >> might be more critical than squeezing out every dBm for the datasheet (tech >> vs sales argument). >> >> Regards, >> Mike >> >> >> -----Original Message----- >> From: Ben Greear [mailto:greearb@candelatech.com] >> Sent: November 17, 2015 11:48 AM >> To: Michael Rex; pommnitz@yahoo.com >> Subject: Re: TX-Power limits for ath10k based card on Linux 3.18.24 >> (offlist) >> >> On 11/17/2015 11:20 AM, Michael Rex wrote: >>> Joerg, >>> >>> The power at 11g is 15-19dBm, not 20dBm as shown in this screenshot. >> There is no such thing as 2 chains power in 11g (they have diversity, which >> means A port >>> or B port, there is no MIMO processing going on there to sum the powers). >> That is a fallacy but they won't remove it from their datasheet. >>> >>> The power will fluctuate, depending on the data rate used. So when you >> had less attenuation, it likely transmitted at 54M. When you added >> attenuation, it >>> adapted to 6M and output 4dBm more. You'd have to see the received >> data >> rate on the receiver, or test equipment that can detect it (I believe there >> is still an >>> issue reporting data rate in Ath10k?). The power for 48M is likely 16, >> and 36M is likely 17dBm, so you kind of have to know what data rate is being >> sent to >>> know how close to expected you really are. Otherwise, you could be 4dBm >> off from your expectation, but its exactly as designed. >> >> You can force the data-frame transmit rate in ath10k firmware, and, at least >> with my hacked kernel and firmware, >> you can also force the management and broadcast/mcast frames to a specific >> legacy rate. >> >> So, you should be able to force to 6Mbps, do a test, and then force to >> 54Mbps, and do >> another test to verify the tx-power at different rates. >> >> The change I made to my firmware regarding tx power is something like this: >> >> Original code took total-requested-power, and basically divided by 3 if NIC >> was 3x3 capable. >> >> I changed it to set up tx-power based on the number of chains that a >> particular rate would use, so >> legacy rates got full power, 2x2 got 1/2 power, and 3x3 got 1/3 power per >> chain. >> >> I'm not 100% sure this is correct, but it seems to work, and at least one >> company using >> my firmware passed regulatory testing with no problems related to tx >> power... >> >> Thanks, >> Ben >> >> >>> >>> Power accuracy is also not guaranteed and commonly outside of +/- 2dBm. >> However, Compex is /usually/ one of the good ones you can usually count on >> within -2dBm >>> of accuracy (I wouldn't bet money on it, quality varies for all >> manufacturers). So it is important to have accurately calibrated test >> setups with measured >>> losses of cables and connectors, as NOTHING (short of $$$ parts) is ever >> their rating. For example, ALL my mini circuits 20dBm attenuators are >> closer to 21dBm >>> than 20dBm. All the cheap splitters have more than 4.3dBm of insertion >> loss where people often expect 3dBm. The attenuators like Aeroflex that are >> 6X the cost >>> will be like 10.1dBm and 20.2dBm on their respective ratings as a >> comparison of quality, in my experience. >>> >>> In an earlier previous gen 11n Compex card, when you put the card in 11g >> mode and used left chain (their firmware using the closed Qualcomm fusion >> driver), you >>> got full output power. When you used right chain, there was like 7dBm >> less. Compex couldn't explain it to me, we just had to note it and move on. >> Who knows if >>> something like that is part of the problem. It could have been an antenna >> misconfiguration in their calibration. Likely, they often just accept the >> Qualcomm >>> reference platform for the most part. >>> >>> How accurate is your test setup and measurements? If you don't have >> tested >> losses, you can probably only say +/- 3dBm on your numbers, or just relative >>> measurement testing. >>> >>> Best regards, >>> >>> Mike >>> >> >> >> -- >> Ben Greear >> Candela Technologies Inc http://www.candelatech.com >> > -- Ben Greear Candela Technologies Inc http://www.candelatech.com _______________________________________________ ath10k mailing list ath10k@lists.infradead.org http://lists.infradead.org/mailman/listinfo/ath10k