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

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

2011/2/16 Brian Prodoehl <bprodoehl@gmail.com>

> On Wed, Feb 16, 2011 at 9:47 AM, 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).
>
>
> If you can operate beyond MCS7 (MCS8-15), then you are using two
> spatial streams over two antennas.  I have seen this with HT IBSS and
> ath9k.
>
> -Brian
>

I get the following results, so based on your comments I suppose the two
antennas are being used:

It is a scp transmission between two laptops joined at the same HT IBSS
network.
(The first parameter shows the file transmitted percentage, the second is
the amount of MB transmitted and the third one the estimated time of arrival
(or expected time to finish the transmission).

5%   51MB  10.9MB/s   01:22 ETA signal:  -33 dBm tx bitrate: 300.0 MBit/s
MCS 15 40Mhz short GI
10%  100MB  12.3MB/s   01:09 ETA signal:  -33 dBm tx bitrate:    300.0
MBit/s MCS 15 40Mhz short GI

This results belong to one of the laptops, the other one I don't know why is
not using HT rates (although both of them are similar).
Are you having HT rates bidirectionally? Sometimes it happens to me that one
of the HT laptops shows legacy 2.4 or 5 rates, and there is no way of
upgrading its data rates. I'm going to dig into this right now.

Baldo
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