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Doc.: IEEE 802.11-11/1031r0 Submission July 2011 Hitoshi MORIOKA, ROOT Inc.Slide 1 Air-time Consumption by Beacon and Probe Date: 2011-07-20 Authors:

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Presentation on theme: "Doc.: IEEE 802.11-11/1031r0 Submission July 2011 Hitoshi MORIOKA, ROOT Inc.Slide 1 Air-time Consumption by Beacon and Probe Date: 2011-07-20 Authors:"— Presentation transcript:

1 doc.: IEEE /1031r0 Submission July 2011 Hitoshi MORIOKA, ROOT Inc.Slide 1 Air-time Consumption by Beacon and Probe Date: Authors:

2 doc.: IEEE /1031r0 Submission July 2011 Hitoshi MORIOKA, ROOT Inc.Slide 2 Abstract This presentation shows an example of the time occupied by Beacon and Probe Request/Response measured at IEEE mid-week plenary in Vancouver session, November This was presented at TGu in And some slides are added. This is just an information for AP discovery. (not include any proposal)

3 doc.: IEEE /1031r0 Submission July 2011 Hitoshi MORIOKA, ROOT Inc.Slide 3 Conditions Time –16 Nov(Wed) 10:51:00-10:56:00 (300sec) Place C, D (Mid-session Plenary) Channel 11 (11g) Equipment –Thinkpad X40 –Atheros WLAN I/F, monitor mode –NetBSD –tcpdump

4 doc.: IEEE /1031r0 Submission July 2011 Hitoshi MORIOKA, ROOT Inc.Slide 4 Result Observed BSSID: 12 (excluding ff:ff:ff:ff:ff:ff) Observed Src MAC Address: MAC Addresses (STAs) sent Probe Request 9 MAC Addresses (APs) sent Probe Response Observed Frames Bytes include MAC header and FCS.

5 doc.: IEEE /1031r0 Submission July 2011 Hitoshi MORIOKA, ROOT Inc.Slide 5 Result (Cont.) Frames Bytes Occupied time may be more important.

6 doc.: IEEE /1031r0 Submission July 2011 Hitoshi MORIOKA, ROOT Inc.Slide 6 Transmission Rate

7 doc.: IEEE /1031r0 Submission July 2011 Hitoshi MORIOKA, ROOT Inc.Slide 7 Transmission Rate (Cont.)

8 doc.: IEEE /1031r0 Submission July 2011 Hitoshi MORIOKA, ROOT Inc.Slide 8 Occupied Time Calculation (Probe Request) Probe Request Occupied Time DIFSCWTXTIME OccupiedTime = (DIFS + CW + aPreambleLength + aPLCPHeaderLength/DATARATE) * TotalFrames + (TotalBytes*8/DATARATE)) = (( /1.0) * (265168*8/1.0)) + (( /2.0) * (8316*8/2.0)) + (( /11.0) * (13175*8/11.0)) = 6,695,978us (2.23%) aSlotTime:20us aSIFSTime:10us aPreambleLength:144us aPLCPHeaderLength:48bits aCWmin:31 aCWmax:1023 DIFS:50us CW:620us

9 doc.: IEEE /1031r0 Submission July 2011 Hitoshi MORIOKA, ROOT Inc.Slide 9 Occupied Time Calculation (Probe Response) Probe Response Occupied Time DIFSCW ACK aSlotTime:20us aSIFSTime:10us aPreambleLength:144us aPLCPHeaderLength:48bits aCWmin:31 aCWmax:1023 DIFS:50us CW:620us ACKRate:1Mbps ACKLength:14Bytes TXTIME SIFS OccupiedTime = (DIFS + CW + aPreambleLength + aPLCPHeaderLength/DATARATE + aSIFSTime + aPreambleLength + aPLCPHeaderLength/ACKRate + ACKLength*8/ACKRate) * TotalFrames + (TotalBytes*8/DATARATE)) = (( / /1.0+14*8/1.0) * (576803*8/1.0)) + (( / /1.0+14*8/1.0) * 5 + (510*8/2.0)) + (( / /1.0+14*8/1.0) * 4 + (408*8/5.5)) + (( / /1.0+14*8/1.0) * ( *8/11.0)) = 12,762,928us (4.25%) TXTIME

10 doc.: IEEE /1031r0 Submission July 2011 Hitoshi MORIOKA, ROOT Inc.Slide 10 Occupied Time Calculation (Beacon) Beacon Occupied Time DIFSCWTXTIME OccupiedTime = (DIFS + CW + aPreambleLength + aPLCPHeaderLength/DATARATE) * TotalFrames + (TotalBytes*8/DATARATE)) = (( /1.0) * (331103*8/1.0)) + (( /11.0) * ( *8/11.0)) = 6,304,566us (2.10%) aSlotTime:20us aSIFSTime:10us aPreambleLength:144us aPLCPHeaderLength:48bits aCWmin:31 aCWmax:1023 DIFS:50us CW:620us

11 doc.: IEEE /1031r0 Submission July 2011 Hitoshi MORIOKA, ROOT Inc.Slide 11 Occupied Time Calculation Result

12 doc.: IEEE /1031r0 Submission Beacon vs Probe Active scan is faster than passive scan? –Duration of passive scan depends on the beacon interval. –Duration of active scan depends on timeout of probe response. If there are no AP matching SSID, STA will wait timeout. Air-time occupancy –Air-time occupied by beacon is fixed regardless of the number of STAs. –Air-time occupied by probe may be propotional to the number of STAs. July 2011 Hitoshi MORIOKA, ROOT Inc.Slide 12

13 doc.: IEEE /1031r0 Submission AP discovery time and scalability trade-off For fast AP discovery –Passive scan with short beacon interval –Active scan with short timeout For accomodating large number of STAs –Air-time occupied by management frames should be as short as possible. Please consider the balance of these two. July 2011 Hitoshi MORIOKA, ROOT Inc.Slide 13


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