[ath9k-devel] Progress on Ath9k HT support on Adhoc mode

[Baldomero Coll <baldo.ath9k@gmail.com>]

Thank you for your illustrative answer adrian.
I've sent an email today to the mailing list showing my performance in HT
IBSS mode.

What happens now is that my ad-hoc link don't support HT in both directions.
One of the stations seems to stay in legacy IBSS mode, although sometimes it
upgrades to HT mode.

I suppose it is due to the link adaptation mechanism (Minstrel HT?), but I
would also investigate if the station that stay in legacy IBSS mode is the
one who creates the HT network, the one who joins the HT network, or if it
don't really depend on that.

2011/2/16 Adrian Chadd <adrian@freebsd.org>

> Hi,
>
> From my understanding:
>
> * If your RX chainmask has >1 radio enabled, you'll always be doing
> receive-side "diversity" (which is really "combining" (MRC) if I
> understand the technology correctly on multi-radio atheros 11n cards);
> * If your TX chainmask has >1 radio enabled and the TX descriptor has
> the relevant chainmask bits set, you should be transmitting on both
> antennas regardless of the rate. I honestly haven't verified it (I've
> only verified that behaviour for transmitting legacy rates out of the
> 11n chips);
>
> * For rates < MCS8 (and legacy rates) there's further TX-side trickery
> that can be going on which I'm not too up-to-date on. For example,
> some (all?) of the 11n chips allow you to optionally transmit MCS0-7
> using STBC. But iirc, STBC is only enabled for 1-stream TX.
>
> In short, if you've got all the radios enabled  for RX and ath9k is
> enabling both/all radio chains when TX'ing, I think the answer is
> "yes" for you. :)
>
> Adrian
>
> On 16 February 2011 22:47, Baldomero Coll <baldo.ath9k@gmail.com> wrote:
> > I'm not sure, but I've read somewhere that by default the two antennas
> are
> > used.
> > It is true that I'm not interested in selecting the number of antennas,
> what
> > I really want is that the MIMO capability is exploited if I'm using
> 802.11n
> > HT IBSS operation mode.
> > Can someone confirm that by default the two antennas (spatial diversity)
> are
> > being used when we create the HT IBSS network?
> >
> > 2011/2/16 Mohammed Shafi <shafi.ath9k@gmail.com>
> >>
> >> On Tue, Feb 15, 2011 at 2:35 PM, Baldomero Coll <baldo.ath9k@gmail.com>
> >> wrote:
> >> > Hello,
> >> >
> >> > Can you please tell me how do you select one o two antennas?
> >>
> >> I don't know why you should do that. I guess changing the tx/rx
> >> chainmask will do after it was read from eeprom.
> >>
> >> >
> >> > I'm using a similar setting than you:
> >> > Linux kernel: 2.6.32-28-generic-pae.
> >> > Driver: compat-wireless-2011-01-17 and iw-0.9.21 with the patch
> >> > suggested by
> >> > Alex.
> >> > Radio card: Ubiquiti SR71x
> >> >
> >> > Thanks in advance,
> >> > Baldomero
> >> >>
> >> >> Hi all,
> >> >>
> >> >> I would like to confirm my findings. My test platform configurations
> >> >> are
> >> >> follow.
> >> >> Board: pcengine alix3d2
> >> >> Linux kernel: 2.6.35 from linux-wireless git
> >> >> Driver: compat-wireless-2011-01-17 and iw-0.9.21 with the patch
> >> >> suggested by Alex.
> >> >> Radio card: Ubiqiti SR71a on channel 36 with HT40+
> >> >> Measurement tool and settings: Iperf, UDP, 100Mb offered load
> >> >>
> >> >> Recored throughput: 50-54Mbps (one antenna); 78-80Mbps (two or three
> >> >> antennas).
> >> >
> >> >
> >> > _______________________________________________
> >> > ath9k-devel mailing list
> >> > ath9k-devel at lists.ath9k.org
> >> > https://lists.ath9k.org/mailman/listinfo/ath9k-devel
> >> >
> >> >
> >
> >
> > _______________________________________________
> > ath9k-devel mailing list
> > ath9k-devel at lists.ath9k.org
> > https://lists.ath9k.org/mailman/listinfo/ath9k-devel
> >
> >
>
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