Question on tx-power and number of chains.

Question on tx-power and number of chains.

[Ben Greear]

Suppose a NIC wants to decrease TX power for certain rates based on the
number of chains (ie, subtract amount A from requested rate for 2 chains,
and B for 3 chains).

I assume the NIC wants to do this is because if the pkt is transmitted out each antenna,
then there is ~3x the power put onto the air.

Now, the question is, should this power-decrease be per rate,
and perhaps different for each rate, or can all rates use all
tx-chains (and so tx-power should be decreased the same maximum amount
based on the hardware's number of chains for each rate).

I am thinking that CCK rates can only ever be transmitted by a single
chain, so in that case those rates would not need their power decreased
from the requested?

And if that is so, what about the /a/g/ rates, and lower-speed HT/VHT
rates as well?

Is there a table somewhere that explains how many chains are used by each
rate?

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

Re: Question on tx-power and number of chains.

[Johannes Berg]

On Wed, 2015-02-25 at 10:51 -0800, Ben Greear wrote:

> Is there a table somewhere that explains how many chains are used by each
> rate?

mcsindex.com?

Re: Question on tx-power and number of chains.

[Arend van Spriel]

On 02/25/15 20:10, Johannes Berg wrote:
> On Wed, 2015-02-25 at 10:51 -0800, Ben Greear wrote:
>
>> Is there a table somewhere that explains how many chains are used by each
>> rate?
>
> mcsindex.com?

Nice. Adding that to my bookmarks. What happened to that quirky MCS32.

Regards,
Arend

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Re: Question on tx-power and number of chains.

[Johannes Berg]

On Wed, 2015-02-25 at 20:21 +0100, Arend van Spriel wrote:
> On 02/25/15 20:10, Johannes Berg wrote:
> > On Wed, 2015-02-25 at 10:51 -0800, Ben Greear wrote:
> >
> >> Is there a table somewhere that explains how many chains are used by each
> >> rate?
> >
> > mcsindex.com?
> 
> Nice. Adding that to my bookmarks. What happened to that quirky MCS32.

It's the unloved stepchild ;-)

They also removed all the other higher HT ones (>32) when adding VHT.
You can still find an old version on archive.org IIRC.

johannes

Re: Question on tx-power and number of chains.

[Ben Greear]

On 02/25/2015 11:10 AM, Johannes Berg wrote:
> On Wed, 2015-02-25 at 10:51 -0800, Ben Greear wrote:
> 
>> Is there a table somewhere that explains how many chains are used by each
>> rate?
> 
> mcsindex.com?

What about OFDM and CCK.  Are those always 1 chain?

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

Re: Question on tx-power and number of chains.

[Johannes Berg]

On Wed, 2015-02-25 at 11:50 -0800, Ben Greear wrote:
> On 02/25/2015 11:10 AM, Johannes Berg wrote:
> > On Wed, 2015-02-25 at 10:51 -0800, Ben Greear wrote:
> > 
> >> Is there a table somewhere that explains how many chains are used by each
> >> rate?
> > 
> > mcsindex.com?
> 
> What about OFDM and CCK.  Are those always 1 chain?

They're 1 stream at least, so only one chain is needed. I'm not entirely
sure you couldn't transmit them on multiple chains but I don't think
it'd make that much sense?

johannes