Date: Fri, 5 Aug 2011 08:24:53 +0530
From: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
To: Felix Fietkau <nbd@openwrt.org>
CC: <linville@tuxdriver.com>, <linux-wireless@vger.kernel.org>
Subject: Re: [PATCH v3 11/13] ath9k_hw: Disable Walsh spatial spreading for 2
 chains
Message-ID: <20110805025452.GA28266@vmraj-lnx.users.atheros.com> (sfid-20110805_045439_879451_6EFBED3A)
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On Thu, Aug 04, 2011 at 08:23:28PM +0200, Felix Fietkau wrote:
> On 2011-08-04 7:54 PM, Rajkumar Manoharan wrote:
> >The Walsh bit is disabled for regulatory consideration.
> >
> >As per the FCC rulings, only transmissions that are completely
> >non-coherent, are allowed to waive the array gain contribution
> >to EIRP for multi-transmit configurations. The use of 2-stream
> >with 2 transmit and use of 3-steam with 3 transmit qualifies
> >for this spatial multiplexing MIMO classification as long as
> >the streams are directly mapped to each radio (not Walsh spread
> >prior to splitting to multiple radios)
> I think ath9k does not waive the array gain contribution. I haven't
> checked AR9003, but on AR9002 and older, it explicitly includes the
> array gain contribution in the tx power limit calculation. I'm not
> sure that unconditionally disabling spatial spreading is the right
> way to deal with this.
>
We might violate the FCC rule with 2x2 config(3dB higher at 2-stream)
if this bit is enabled. Based on chainmask we can disable Walsh bit.
Any comments?

--
Rajkumar