From mboxrd@z Thu Jan  1 00:00:00 1970
From: Luis R. Rodriguez <lrodriguez@atheros.com>
Date: Mon, 27 Sep 2010 13:53:29 -0700
Subject: [ath9k-devel] [AR9160]: 3 RX chain operation in 11abg
 legacy-only mode?
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	<alpine.LFD.2.00.1009271338590.20592@kishwoot.cs.washington.edu>
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On Mon, Sep 27, 2010 at 01:41:02PM -0700, Daniel Halperin wrote:
> 
> On Mon, 27 Sep 2010, Felix wrote:
> 
> > On Mon, 2010-09-27 at 11:19 -0700, Luis R. Rodriguez wrote:
> >> On Sat, Sep 25, 2010 at 08:14:43PM -0700, Adrian Chadd wrote:
> >>> Hi,
> >>>
> >>> FreeBSD's AR9160 support enables all three RX chains in legacy mode.
> >>> The ath9k codebase doesn't - it calibrates all three chains, but the
> >>> ADC calibration results in legacy mode give all 0x0's for chain 1 and 2.
> >>> (And seemingly invalid results for chain 0 in 11g mode, but that's another
> >>> issue which I am hoping someone will comment on.)
> >>>
> >>> Is there any benefit or detriment to leaving RX chains 1 and 2 enabled
> >>> when in 11a/11bg mode? Does the unit do any kind of multipath
> >>> discrimination?
> > Leaving all RX chains enabled will give a huge gain for all OFDM rates,
> > they get MRC combined
> > (http://en.wikipedia.org/wiki/Maximal-ratio_combining) in the frequency
> > domain(after the FFT).
> >
> >  Felix
> >
> 
> Strongly seconded.  With 3 antennas on and using MRC, you get something 
> like an average of 7--10 dB (i.e. a factor of 4 to 10) more useful signal 
> power in indoor environments, precisely because of the impact of diversity 
> on multipath fading.

Patches welcomed :D

  Luis