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Re: [802.19] 40MHz 802.11n Conference Call



The results show what can happen if there is an overlapp, so they are valid for the overlap case, as well as for the non-overlap 20 MHz operations.  If you compare the two, then the conclusion is that the BSSs shall operate in 20 MHz non-overlapping regions, which 11n draft states now (and this is one of the conclusions drawn in the earlier email by Bill).  

 

For the second reason, do you mean only 11n devices? If so, then “may” does not guarantee that they will set 40 MHz Intolerant bit. How can it be guaranteed that this bit will be set (by these devices) for other radios operating in 2.4 GHz then?

 

- Ariton


From: Perahia, Eldad [mailto:eldad.perahia@intel.com]
Sent: Monday, June 09, 2008 8:20 AM
To: Xhafa, Ariton; STDS-802-19@LISTSERV.IEEE.ORG
Subject: RE: [802.19] 40MHz 802.11n Conference Call

 

The results are not valid for 2.4 GHz for at least two reasons:

 

1) no partial overlap is allowed in 2.4 GHz

2) any device may transmit the 40 MHz Intolerant bit for any reason

 

Regards,

Eldad

 


From: Xhafa, Ariton [mailto:axhafa@TI.COM]
Sent: Sunday, June 08, 2008 9:41 PM
To: STDS-802-19@LISTSERV.IEEE.ORG
Subject: Re: [802.19] 40MHz 802.11n Conference Call

 

The latest draft on 802.11n enables CCA in secondary channel (earlier called extension channel) and also allows for transmission in 20 MHz primary channel (earlier called control channel) if the secondary channel is busy; thus it allows switching as well. If one wants to compare it with the latest draft then the results that use CCA and switching should be considered. The only other (major) difference is 40 MHz Intolerant bit, which would restrict the 20/40 MHz operating BSS in either 20 MHz only or 20/40 MHz. However, 40 MHz Intolerant bit does not apply to legacy BSSs (802.11a/g/b). Hence, the results are still valid when legacy BSSs are operating in the secondary channel, even for draft 5.0.

 

- Ariton


From: Perahia, Eldad [mailto:eldad.perahia@INTEL.COM]
Sent: Sunday, June 08, 2008 11:07 PM
To: STDS-802-19@LISTSERV.IEEE.ORG
Subject: Re: 40MHz 802.11n Conference Call

 

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]
Sent: Sunday, June 08, 2008 8:56 PM
To: STDS-802-19@LISTSERV.IEEE.ORG
Subject: Re: [802.19] 40MHz 802.11n Conference Call

 

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: Shellhammer, Steve [mailto:sshellha@QUALCOMM.COM]
Sent: Wednesday, June 04, 2008 12:17 AM
To: STDS-802-19@LISTSERV.IEEE.ORG
Subject: 40MHz 802.11n Conference Call

 

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