[ath9k-devel] Question about antenna throughput.

[Ben Greear <greearb@candelatech.com>]

On 07/15/2012 02:39 AM, Adrian Chadd wrote:
> On 12 July 2012 07:11, Ben Greear <greearb@candelatech.com> wrote:
>> We have a 3x3 NIC (wpea-127n).  A user reports that when using
>> a single antenna cable to directly connect to an AP (with attenuator),
>> that one of the antenna can do about 30Mbps download from AP, the
>> other about 25Mbps, and the third cable can only do about 1Mbps.
>>
>> Is that expected results?
>
> If I recall what's going on, the actual signal sent out the antennas
> isn't necessarily a mirrored copy from each antenna, even for 1 stream
> and legacy signals. Definitely for 2 and 3 stream signals that is
> absolutely to be expected.
>
> The baseband may decide to "scramble" it so part of the wireless
> transmission goes out each antenna. Don't ask me about the details, I
> don't know them.
>
> There's also STBC for 1 stream 11n rates.
>
> If you want to connect a single cable to an AP, you have to put it
> into a single chain TX/RX mode and use the correct chain. On that NIC
> you can configure it to be a single chain on any of chain 0, 1 or 2.
> (It doesn't have to be 0.) But you have to choose a single chain.
>
> So, yes. I think that's totally understandable behaviour.

Ok, I'm going to look into this chain configuration.

This user is also reporting that our box can only communicate
down to about -72dBm, whereas some off-the-shelf USB dongles
are providing around 100kbps at -78 to -80dBm.

Are there any published rate v/s range results for ath9k available?

Perhaps the chaining issue is also involved in this?

Thanks for the detailed answers on this....this is new
territory for me!

Ben

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