1. Submission doc.: IEEE 11-11/1413r4 January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 1 Real Air-time Occupation by Beacon and Probe Date: 2012-01-12 Authors:

2. Submission doc.: IEEE 11-11/1413r4 January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 2 Abstract This document shows retry numbers of Probe Response as the answer for discussion in Atlanta. (Slide 9)

3. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 3 Motivation 3G mobile operators have demand to offload their data traffics to WLAN network. Especially, they have higher demands for the locations where many people meet or stay for data offloading, because high data traffics occur at those locations. It’s highly expected that FILS will realize transition from 3G to WLAN in very short time.

4. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 4 Real world (1) Number of Smart-phone is increasing. iPhone, Android, Windows-phone, Blackberry… Smart-phone holders always touch its screen. While its screen is activated (backlight turned on), Smart-phone starts searching surrounding WLAN-APs.

5. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 5 Real world (2) Many Smart-phone holders are in the crowded commuter train. Imagine what happens when the train arrives at the station. Air monitoring was executed at a train station in Tokyo. Results are explained in the following slides.

6. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 6 Conditions Time/Date: Around 18:00 / October 11(Tue), 2011 Location: Shinjuku station (Keio line), Tokyo Monitoring CH: 6CH(2,437MHz) Monitoring period: 300 seconds (5 minutes) Measured CH Thinkpad X200 Windows XP USB Wireless Monitor Adoptor (Air Pcap NX) Wireshark

7. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 7 Result Observed frames FramesBytes Count% % Beacon13,87115.051,689,0409.82 Probe Request7,1397.75989,7975.75 Probe Response24,68726.792,941,33117.10 Other46,46250.4211,581,63467.33 Total92,159 17,201,802

8. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 8 Result (cont.) Time occupation is more important. Doc. IEEE802.11-11/1031r0 was referred for time occupation analysis. BytesFrames

9. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 9 Transmission Rate Rate [Mbps] BeaconProbe RequestProbe ResponseOthers Frames% % % % 113,86199.936,54791.7124,60699.6712,95627.89 200.00210.2940.025041.08 600.00130.1870.034671.01 600.0020.0310.001130.24 900.0030.0410.002300.50 1120.015107.14150.062,7665.95 1200.0020.0340.022880.62 1800.0070.1070.033410.73 2470.0540.0660.0213,79329.69 3600.000 30.011,3092.82 4800.00100.1420.011,9534.20 5410.01200.28310.1311,74225.27 Total13,871 7,139 24,687 46,462

10. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 10 Transmission Rate (cont.) Rate [Mbps] BeaconProbe RequestProbe ResponseOthers Bytes% % % % 1 1,688,64 0 99.98838,51084.72 2,849,89 6 96.89871,8127.53 200.0010,0191.015,2570.18466,6504.03 600.0012,6331.2810,7100.36531,0434.59 600.001,5900.161,5300.05127,0941.10 900.002,6310.271,5300.05301,8192.61 11800.0076,5657.7413,8480.47687,5605.94 1200.003,0600.316,1200.21215,4591.86 1800.0010,1981.038,2120.28287,1192.48 242800.023,1540.325,2790.18805,1366.95 3600.000 4,5900.16967,9718.36 4800.0013,5091.362,2590.081,285,71611.10 54400.0017,9281.8132,1001.095,034,25543.47 Total 1,689,04 0 989,797 2,941,33 1 11,581,63 4

11. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 11 Occupied Time Calculation (Beacon) Occupied Time DIFSCWTX TIME aSlotTime:20us aSIFSTime:10us aPreambleLength:144us aPLCPHeaderLength:48bits aCWmin:31 aCWmax:1023 DIFS:50us CW:310us Occupied Time = ∑((DIFS + CW + aPreambleLength + aPLCPHeaderLength/DATARATE) * TotalFrames + (TotalBytes * 8/DATARATE)) = ((50 + 310 + 144 + 48 / 1.0) * 13,861 + (1,688,640 * 8 / 1.0) + ((50 + 310 + 144 + 48 / 11.0) * 2 + (80 * 8 / 11.0) + ((50 + 310 + 144 + 48 / 24.0) * 7 + (280 * 8 / 24.0) + ((50 + 310 + 144 + 48 / 54.0) * 1 + (40 * 8 / 54.0) = 21,165,613 us (7.06%) Beacon

12. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 12 Occupied Time Calculation (Probe Request) Occupied Time = ∑((DIFS + CW + aPreambleLength + aPLCPHeaderLength/DATARATE) * TotalFrames + (TotalBytes * 8/DATARATE)) = ((50 + 310 + 144 + 48 / 1.0) * 6,547 + (838,510 * 8 / 1.0) + ((50 + 310 + 144 + 48 / 2.0) * 21 + (10,019 * 8 / 2.0) + ((50 + 310 + 144 + 48 / 5.5) * 13 + (12,633 * 8 / 5.5) + ((50 + 310 + 144 + 48 / 6.0) * 2 + (1,590 * 8 / 6.0) + ((50 + 310 + 144 + 48 / 9.0) * 3 + (2,631 * 8 / 9.0) + ((50 + 310 + 144 + 48 / 11.0) * 510 + (76,565 * 8 / 11.0) + ((50 + 310 + 144 + 48 / 12.0) * 2 + (3,060 * 8 / 12.0) + ((50 + 310 + 144 + 48 / 18.0) * 7 + (10,198 * 8 / 18.0) + ((50 + 310 + 144 + 48 / 24.0) * 4 + (3,154 * 8 / 24.0) + ((50 + 310 + 144 + 48 / 48.0) * 10 + (13,509 * 8 / 48.0) + ((50 + 310 + 144 + 48 / 54.0) * 20 + (17,928 * 8 / 54.0) = 10,754,454us (3.58%) Occupied Time DIFSCWTX TIME Probe Request

13. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 13 Occupied Time Calculation (Probe Response) Occupied Time DIFSCWTX TIME Probe ResponseACK TX TIMESIFS aSlotTime:20us aSIFSTime:10us aPreambleLength:144us aPLCPHeaderLength:48bits aCWmin:31 aCWmax:1023 DIFS:50us CW:310us ACKRate:1Mbps ACKLength:14Bytes

14. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 14 Occupied Time Calculation (Probe Response) (Cont.) Occupied Time = ∑((DIFS + CW + aPreambleLength + aPLCPHeaderLength/DATARATE +aSIFSTime + aPreambleLength + aPLCPHeaderLeangth / ACKRATE + ACKLength * 8 / ACKRATE) * TotalFrames + (TotalBytes * 8/DATARATE)) = ((50 + 310 + 144 + 48 / 1.0 +10+ 144+48/1.0+14*8/1.0) * 24,606 + (2,849,896 * 8 / 1.0) + ((50 + 310 + 144 + 48 / 2.0 + 10+144+48/1.0+14 * 8 / 1.0) * 4 + (5,257 * 8 / 2.0) + ((50 + 310 + 144 + 48 / 5.5 + 10+144+48/1.0+14 * 8 / 1.0) * 7 + (10,710 * 8 / 5.5) + ((50 + 310 + 144 + 48 / 6.0 + 10+144+48/1.0+14 * 8 / 1.0) * 1 + (1,530 * 8 / 6.0) + ((50 + 310 + 144 + 48 / 9.0 + 10+144+48/1.0+14 * 8 / 1.0) * 1 + (1,530 * 8 / 9.0) + ((50 + 310 + 144 + 48 / 11.0 + 10+144+48/1.0+14 * 8 / 1.0) * 15 + (13,848 * 8 / 11.0) + ((50 + 310 + 144 + 48 / 12.0 + 10+144+48/1.0+14 * 8 / 1.0) * 4 + (6,120 * 8 / 12.0) + ((50 + 310 + 144 + 48 / 18.0 + 10+144+48/1.0+14 * 8 / 1.0) * 7 + (8,212 * 8 / 18.0) + ((50 + 310 + 144 + 48 / 24.0 + 10+144+48/1.0+14 * 8 / 1.0) * 6 + (5,279 * 8 / 24.0) + ((50 + 310 + 144 + 48 / 36.0 + 10+144+48/1.0+14 * 8 / 1.0) * 3 + (4,590 * 8 / 36.0) + ((50 + 310 + 144 + 48 / 48.0 + 10+144+48/1.0+14 * 8 / 1.0) * 2 + (2,259 * 8 / 48.0) + ((50 + 310 + 144 + 48 / 54.0 + 10+144+48/1.0+14 * 8 / 1.0) * 31 + (32,100 * 8 / 54.0) = 44,215,439us (14.74%)

15. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 15 Occupied Time Calculation Result Packet type Occupancy rate (%) Occupied time (sec) Beacon7.0621.17 Probe Req.3.5810.75 Probe Res.14.7444.22 Others74.62223.86 Total100.00300.00

16. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 16 Retry of Probe Response Probe Response frames: 24,687 Retry frames in these: 12,274 (49.7%) Almost all retry frames are transmitted in a few msec after the original transmission. The percentage of retry frames may be increased in more congested situation. See Slide 17 for detailed example.

17. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 17 Example of retry frames (Probe Response) No.TimeSourceDestinationInfoSN 10.503998 XXXX_c5:83:c 1 XXXX:16:4c:f2 Probe Response, SN=2066, FN=0, Flags=..m.....C, BI=100, SSID=ABC 2066 20.5054 XXXX_c5:83:c 6 XXXX:16:4c:f2 Probe Response, SN=2067, FN=0, Flags=........C, BI=100, SSID=\000"" 2067 30.506277 XXXX_c5:83:c 6 XXXX:16:4c:f2 Probe Response, SN=2067, FN=0, Flags=....R...C, BI=100, SSID=\000"" 2067 40.507278 XXXX_c5:83:c 6 XXXX:16:4c:f2 Probe Response, SN=2067, FN=0, Flags=....R...C, BI=100, SSID=\000"" 2067 50.521844XXXX:c5:58:91XXXX:16:4c:f2 Probe Response, SN=71, FN=0, Flags=........C, BI=100, SSID=12345678 71 60.523116 XXXX_c5:83:c 0 XXXX:16:4c:f2 Probe Response, SN=2068, FN=0, Flags=..m.....C, BI=100, SSID=XYZ 2068 70.524523 XXXX_c5:83:c 1 XXXX:16:4c:f2 Probe Response, SN=2069, FN=0, Flags=..m.....C, BI=100, SSID=ABC 2069 80.525524 XXXX_c5:83:c 1 XXXX:16:4c:f2 Probe Response, SN=2069, FN=0, Flags=..m.....C, BI=101, SSID=ABC 2069 90.526525 XXXX_c5:83:c 1 XXXX:16:4c:f2 Probe Response, SN=2069, FN=0, Flags=..m.....C, BI=102, SSID=ABC 2069 100.52778 XXXX_c5:83:c 6 XXXX:16:4c:f2 Probe Response, SN=2070, FN=0, Flags=........C, BI=100, SSID=\000"" 2070 110.53265XXXX:42:60:c4Broadcast Probe Response, SN=3699, FN=0, Flags=........C, BI=100, SSID=12345678 3699 120.544779XXXX:c5:58:91XXXX:16:4c:f2 Probe Response, SN=72, FN=0, Flags=........C, BI=100, SSID=12345678 72 130.545903XXXX:c5:58:91XXXX:16:4c:f2 Probe Response, SN=72, FN=0, Flags=....R...C, BI=100, SSID=12345678 72 140.565153XXXX:c5:58:91XXXX:16:4c:f2 Probe Response, SN=73, FN=0, Flags=........C, BI=100, SSID=12345678 73 150.566405 XXXX_c5:83:c 0 XXXX:16:4c:f2 Probe Response, SN=2071, FN=0, Flags=..m.....C, BI=100, SSID=XYZ 2071 160.571022 XXXX_c5:83:c 0 XXXX:16:4c:f2 Probe Response, SN=2071, FN=0, Flags=..m.....C, BI=101, SSID=XYZ 2071 170.573148 XXXX_c5:83:c 0 XXXX:16:4c:f2 Probe Response, SN=2071, FN=0, Flags=..m.....C, BI=102, SSID=XYZ 2071 180.574025 XXXX_c5:83:c 0 XXXX:16:4c:f2 Probe Response, SN=2071, FN=0, Flags=..m.....C, BI=103, SSID=XYZ 2071 190.575399XXXX:c5:58:91 XXXX:54:de:0 a Probe Response, SN=74, FN=0, Flags=........C, BI=100, SSID=9876543 74 200.576649XXXX:c5:58:91 XXXX:54:de:0 a Probe Response, SN=74, FN=0, Flags=....R...C, BI=100, SSID=9876543 74 210.578148XXXX:c5:58:91 XXXX:54:de:0 a Probe Response, SN=74, FN=0, Flags=....R...C, BI=100, SSID=9876543 74 220.579281XXXX:c5:58:91 XXXX:54:de:0 a Probe Response, SN=74, FN=0, Flags=....R...C, BI=100, SSID=9876543 74 230.594025 XXXX_c5:83:c 0 XXXX:54:de:0 a Probe Response, SN=2080, FN=0, Flags=..m.....C, BI=100, SSID=XYZ 2080 240.595282 XXXX_c5:83:c 1 XXXX:54:de:0 a Probe Response, SN=2081, FN=0, Flags=..m.....C, BI=100, SSID=ABC 2081 250.596399 XXXX_c5:83:c 6 XXXX:54:de:0 a Probe Response, SN=2082, FN=0, Flags=........C, BI=100, SSID=\000"" 2082 Retry Sequence Number

18. Submission doc.: IEEE 11-11/1413r4January 2012 Slide 18 Example of Active Scanning (Probe Request) No.TimeSourceDestinationInfo 1 0a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags=........C, SSID=Broadcast 2 0.239642a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags=........C, SSID=Broadcast 3 0.34641a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags=........C, SSID=Broadcast 4 0.57052a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags=........C, SSID=Broadcast 5 0.637521a0:dd:e5:XXXXBroadcastProbe Request, SN=11, FN=0, Flags=........C, SSID=Broadcast 6 7.956037a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags=........C, SSID=Broadcast 7 8.103645a0:dd:e5:XXXXBroadcastProbe Request, SN=5, FN=0, Flags=........C, SSID=Broadcast 8 8.216269a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags=........C, SSID=Broadcast 9 42.444982a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags=........C, SSID=Broadcast 10 42.589602a0:dd:e5:XXXXBroadcastProbe Request, SN=6, FN=0, Flags=........C, SSID=Broadcast 11 42.669104a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags=........C, SSID=Broadcast 12 59.414604a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags=........C, SSID=Broadcast 13 59.610478a0:dd:e5:XXXXBroadcastProbe Request, SN=6, FN=0, Flags=........C, SSID=Broadcast 14 59.68948a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags=........C, SSID=Broadcast 15 76.896361a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags=........C, SSID=Broadcast 16 77.057485a0:dd:e5:XXXXBroadcastProbe Request, SN=6, FN=0, Flags=........C, SSID=Broadcast 17 77.116107a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags=........C, SSID=Broadcast 18 77.162501a0:dd:e5:XXXXBroadcastProbe Request, SN=11, FN=0, Flags=........C, SSID=Broadcast 19 94.449135a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags=........C, SSID=Broadcast 20 94.644904a0:dd:e5:XXXXBroadcastProbe Request, SN=7, FN=0, Flags=........C, SSID=Broadcast 21 94.690512a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags=........C, SSID=Broadcast 22 111.747534a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags=........C, SSID=Broadcast 23 111.962168a0:dd:e5:XXXXBroadcastProbe Request, SN=7, FN=0, Flags=........C, SSID=Broadcast 24 111.987446a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags=........C, SSID=Broadcast 25 119.520411a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags=........C, SSID=Broadcast 26 119.73995a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags=........C, SSID=Broadcast This is my personal smart-phone Multiple shots of Probe request were transmitted for a timing. It may be vender implementation. The second timing is around timestamp=8.00.

19. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 19 Considerations (Opinion) Multiple shots of Probe request were transmitted every some seconds. Because the STA didn’t know any SSIDs from surrounding APs. If the STA were in the area of the target AP, the STA would receive Beacons from the AP before sending Probe requests at the second timing. Active scanning with wildcard SSID shall be just for the first shots. Repetition of sending Probe requests isn’t effective. It only brings packet congestion.

20. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 20 Conclusion Because of WLAN enabled devices increasing, especially Smart-phones, WLAN air circumstances are getting more crowded. In this packet monitoring, probe responses existed 5 times more than probe requests. Retry transmissions of Probe Response are frequently happened. Repetition of Probe requests is not effective. It brings packet congestion. To see the benefits of effective FILS, improvement of air circumstances would be needed by reducing unnecessary packet exchanges.

21. Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 21 References doc. IEEE802.11-11/1031r0