On 2011-08-05 10:36 AM, Rajkumar Manoharan wrote:
On Fri, Aug 05, 2011 at 08:24:53AM +0530, Rajkumar Manoharan wrote:
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.
This change does not affect 3x3, since we don't use 2-chain for 2-stream.
And Walsh mode would follow INI setting for 2x2 or 3x3 config.
The thing is, on many channels the the card is allowed to transmit at up
to 27 dBm, and often the hardware does not even get close to that. Why
limit tx power by disabling this bit in cases where it's not even close
to going over the limit.
How about disabling it only if the combined txpower is within x dBm of
the regulatory limit, or simply adding the same kind of multi-chain
limit calculation that is being used on AR9280?
- Felix
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