Hi,
I am using STBC (Space Time Block Coding) 1 stream NICs like the AR9280.I would be very grateful someone can kindly advise on how exactly STBC(transmits multiple copies of a data across each of the antennas)?works in ath9k.
I ask this because when I enable STBC 1-stream, the driver seems to uses Space division multiplexing (can this be disabled/enabled?), since the rate is over 150Mbps.
When is STBC activated ?, ...Does Minstrel/ath9k rate adaptation?mechanism?find first check if Spatial multiplexing is better, if not uses STBC ?
Thank you for your time
I think things are a bit confusing, but here goes.
The earlier NICs only support either RX STBC (pre ar9280?) or TX
1-stream STBC (ar9280 or above). Multi-stream STBC isn't in any of the
AR9xxx NICs. It may be in the AR9287; it may be in the AR9300/AR9400.
I've not looked.
I bet what you're finding is:
* with STBC enabled, for single stream rates, it's tx'ing using STBC.
It just sets a bit in the TX descriptor.
* with STBC enabled, for multi-stream rates, it's not setting the STBC
TX bit and it's instead sending it as a 2 stream packet w/out STBC.
The AR9280 is not a one stream NIC - it's a two stream TX/RX NIC.
(Unless you're using the AR9281 - which is an AR9280 1T2R stream
device.) The AR9285 is a 1x1 stream device. The AR9287 is a 2x2 stream
device.
HTH,
Adrian
> I am using STBC (Space Time Block Coding) 1 stream NICs like the AR9280.I would be very grateful someone can kindly advise on how exactly STBC(transmits multiple copies of a data across each of the antennas)?works in ath9k.
> I ask this because when I enable STBC 1-stream, the driver seems to uses Space division multiplexing (can this be disabled/enabled?), since the rate is over 150Mbps.
> When is STBC activated ?, ...Does Minstrel/ath9k rate adaptation?mechanism?find first check if Spatial multiplexing is better, if not uses STBC ?
> Thank you for your time
> _______________________________________________
> ath9k-devel mailing list
> [email protected]
> https://lists.ath9k.org/mailman/listinfo/ath9k-devel
>
Hi,
Thanks for replying Adrian,
OK, just for clarity, you are saying for 1-stream STBC NICs
(AR9380/9280), when I enable STBC from hostapd, the driver only
transmits in STBC (transmits multiple copies of data to each antenna)
if it sending at MCSs 0-7 (1 stream rates), due to low signal quality
or via fixing the MCS to those values. For all other MCSs STBC is
disabled.
Does the rate adaptation (minstrel/ath9k) tell the driver to use STBC,
or is this done at automatically at a lower level?
Any other information about STBC would be appreciated.
Cheers
On Thu, Jun 30, 2011 at 1:57 AM, Adrian Chadd <[email protected]> wrote:
> I think things are a bit confusing, but here goes.
>
> The earlier NICs only support either RX STBC (pre ar9280?) or TX
> 1-stream STBC (ar9280 or above). Multi-stream STBC isn't in any of the
> AR9xxx NICs. It may be in the AR9287; it may be in the AR9300/AR9400.
> I've not looked.
>
> I bet what you're finding is:
>
> * with STBC enabled, for single stream rates, it's tx'ing using STBC.
> It just sets a bit in the TX descriptor.
> * with STBC enabled, for multi-stream rates, it's not setting the STBC
> TX bit and it's instead sending it as a 2 stream packet w/out STBC.
>
> The AR9280 is not a one stream NIC - it's a two stream TX/RX NIC.
> (Unless you're using the AR9281 - which is an AR9280 1T2R stream
> device.) The AR9285 is a 1x1 stream device. The AR9287 is a 2x2 stream
> device.
>
> HTH,
>
>
> Adrian
>
>> I am using STBC (Space Time Block Coding) 1 stream NICs like the AR9280.I would be very grateful someone can kindly advise on how exactly STBC(transmits multiple copies of a data across each of the antennas)?works in ath9k.
>> I ask this because when I enable STBC 1-stream, the driver seems to uses Space division multiplexing (can this be disabled/enabled?), since the rate is over 150Mbps.
>> When is STBC activated ?, ...Does Minstrel/ath9k rate adaptation?mechanism?find first check if Spatial multiplexing is better, if not uses STBC ?
>> Thank you for your time
>> _______________________________________________
>> ath9k-devel mailing list
>> [email protected]
>> https://lists.ath9k.org/mailman/listinfo/ath9k-devel
>>
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>
Hi all,
Please may someone kindly reply to my query regarding STBC (below),
Thanks!
On Mon, Jun 27, 2011 at 12:18 PM, Fred Matthews <[email protected]> wrote:
>
> Hi,
> I am using STBC (Space Time Block Coding) 1 stream NICs like the AR9280.I would be very grateful someone can kindly advise on how exactly STBC(transmits multiple copies of a data across each of the antennas)?works in ath9k.
> I ask this because when I enable STBC 1-stream, the driver seems to uses Space division multiplexing (can this be disabled/enabled?), since the rate is over 150Mbps.
> When is STBC activated ?, ...Does Minstrel/ath9k rate adaptation?mechanism?find first check if Spatial multiplexing is better, if not uses STBC ?
> Thank you for your time
> _______________________________________________
> ath9k-devel mailing list
> [email protected]
> https://lists.ath9k.org/mailman/listinfo/ath9k-devel
>
On Wed, Jun 29, 2011 at 6:17 PM, Fred Matthews <[email protected]> wrote:
>
> Hi,
> Thanks for replying Adrian,
>
> OK, just for clarity, you are saying for 1-stream STBC NICs
> (AR9380/9280), when I enable STBC from hostapd, the driver only
> transmits in STBC (transmits multiple copies of data to each antenna)
> if it sending at MCSs 0-7 (1 stream rates), due to low signal quality
> or via fixing the MCS to those values. For all other MCSs STBC is
> disabled.
>
> Does the rate adaptation (minstrel/ath9k) tell the driver to use STBC,
> or is this done at automatically at a lower level?
>
> Any other information about STBC would be appreciated.
>
You should really look at the 802.11n standard to understand how they
implement STBC. From the driver side, from what I can tell, there is
never a downside (rate-wise) to enabling STBC for transmissions at
MCS0--MCS7. Thus, minstrel_ht turns it on by default.
Dan