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Please keep in mind that this paper is
based on 802.11n draft 1.0. The coexistence mechanisms for 40 MHz in 2.4 GHz
in draft 5.0 are much different. Regards, Eldad From: Bill Shvodian
[mailto:bill.shvodian@IEEE.ORG] 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] 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 |