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Ariton, Thanks for posting the coexistence paper. It
has some very interesting results. Here are my
conclusions:
1) Clearly without the Ext. CCA it would be much better to
keep the two networks on separate 20 MHz channels.
2) If the Ext. CCA is used without switching, the
throughput for the 802.11n network using 40 MHz is roughly the same as the
throughput for the 11n network in 20 MHz, while the throughput for the legacy
BSS drops from 28.3 Mbps for an unshared channel to 12 Mbps. So the
802.11n network sees no gain, while the legacy network sees a drastic 58% drop
in throughput. So again, it looks like it would be better to keep the
the two networks on separate 20 MHz channels.
3) In
the case with Switching and CCA (and reduced TXOP for 40 MHz transmissions), the
802.11n network sees a 10% throughput increase from 60 mbps to 66 Mbps, while
the legacy network sees a 14.5% decrease, from 28.3 Mbps to 24.2
Mbps. This seems like a case of robbing Peter to pay Paul.
I
think that it is important to note how poor the performance is without Ext. CCA
and how with Ext. CCA but without switching, there is no increased throughput
for the 11n network, while the legacy network throughput is badly
degraded. The only option that appears to have any merit is the
one with Switching and Ext. CCA, but even in that case the gain
for the 802.11n network comes at the price of a larger relative
(percentage) decrease in the throughput for the legacy network. So
even then it can be argued that it is better, or at least more fair, to
keep the two networks on separate 20 MHz channels.
My
conclusion from this paper is that the 802.11n network should use 20 MHz mode in
a clear 20 MHz channel rather than using 40 MHz mode where 20 MHz is shared
with a legacy network. I would be interested to hear if others come to the
same conclusion. Thanks again.
Regards,
Bill
From: Xhafa, Ariton [mailto:axhafa@TI.COM] Sent: Sunday, June 08, 2008 10:33 PM To: STDS-802-19@LISTSERV.IEEE.ORG Subject: Re: [802.19] 40MHz 802.11n Conference Call Ivan, Attached is some
earlier work that I did with a couple of colleagues at TI (Anuj Batra and Artur
Zaks) on the 20/40 MHz coexistence of overlapping BSSs in WLANs. I do not plan
to make a presentation on it; however, I just wanted to provide 802.19 members
with some information on 40 MHz operation impact on WLAN networks, and more
specifically, overlapping BSSs. Regards, -
Ariton From:
All,
We will be having a conference call on 40 MHz 802.11n Coexistence. The
call is on Monday June 9 at 1 PM EDT (10 AM PDT).
I will be traveling so Ivan Reede, the 802.19 vice chair, will chair the
call.
At this point we have not had any volunteers to present any material. It
would be good if we could have a few volunteers to prepare some material to lead
focus the discussion. If anyone wants to volunteer please notify Ivan
Reede I_reede@amerisys.com
I would ask that the 802.11 liaison (Eldad) and 802.15 (Sheung) make those
working groups aware of this meeting. Agenda
TO ATTEND THE
AUDIO CONFERENCE: 1. Call +1 858-845-5000
2. After the greeting press 1 to attend
meeting. 3. Enter Meeting ID 80219 4. Enter Meeting Password 80219 followed by the #
sign. 5. Follow the remaining prompts for
recording the callers name and joining the meeting. For assistance, dial #0 at any
time. Steve |