Re: [PATCH] Per chain RSSI reporting

From: Matthias May <matthias.may@neratec.com>
To: Ben Greear <greearb@candelatech.com>,
	Norik Dzhandzhapanyan <norikd@ethertronics.com>,
	Adrian Chadd <adrian@freebsd.org>
Cc: "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
	"ath10k@lists.infradead.org" <ath10k@lists.infradead.org>
Subject: Re: [PATCH] Per chain RSSI reporting
Date: Tue, 30 May 2017 15:23:05 +0200	[thread overview]
Message-ID: <2bc35b78-97b4-bdd8-d8dd-6ec59fa9dbd0@neratec.com> (raw)
In-Reply-To: <82088c50-f800-9d5c-8ccf-879f4b425e66@candelatech.com>

On 27/05/17 23:49, Ben Greear wrote:
> On 05/27/2017 02:41 PM, Norik Dzhandzhapanyan wrote:
>> Yes ~6dB
> 
> If a packet is sent on 1 chain with ath10k firmware (9880 hardware, specifically, but probably
> others as well), it will be around 6db higher on that particular chain
> than if the rate-control sends it on all three chains.
> 
> Are you measuring on a single chain, or on all of the chains at once and adding
> the power?
> 
> I think we would need more detailed reporting using a good third-party device before
> smoothing and RSSI.
> 
> Thanks,
> Ben
> 
>>

Also noteworthy is that if you measure in a cabled environment and add the signal from multiple chains with a combiner
you will probably measure the power wrong.
The reason for this is that the cyclic shift diversity doesn't work well in a 2 dimensional environment (cable) compared
to the 3 dimensional environment (air).

BR
Matthias

>>
>> From: Ben Greear
>> Sent: Saturday, May 27, 2:38 PM
>> Subject: Re: [PATCH] Per chain RSSI reporting
>> To: Norik Dzhandzhapanyan, Adrian Chadd
>> Cc: ath10k@lists.infradead.org, linux-wireless@vger.kernel.org
>>
>>
>> On 05/27/2017 12:25 PM, Norik Dzhandzhapanyan wrote: > We see this inconsistent/incorrect reporting in our RF chamber.
>> How different are the values, and did you sniff with a third-party device to see if it sees the same spikes in RSSI?
>> Thanks, Ben > > Norik > > On 05/27/2017 09:39 AM, Adrian Chadd wrote: >> On 27 May 2017 at 09:07, Ben Greear wrote:
>> >>> At low encoding rates, especially if it switches to a single-chain encoding, >>> maybe the on-air signal really is
>> stronger? >>> >>> Have you verified in some other manner than the signals reported by ath10k >>> are >>> wrong? >>
>> Hiya, >> >> So yeah, multipath, higher TX rates == weaker TX signal, TPC, etc are >> all interesting to know about at
>> the receiver. it's hard to separate >> that out from the noise sometimes, but in some controlled deployments >> its
>> really obvious. >> >> >> >> -adrian >> >> > > > The contents of this transmission are Ethertronics Inc. Confidential
>> and may contain proprietary or legally privileged
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>> Technologies Inc http://www.candelatech.com
>>
> 

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