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

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)

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.

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.

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.

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

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

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

Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 9 Transmission Rate Rate [Mbps] BeaconProbe RequestProbe ResponseOthers Frames% % % % 113, , , , , , , , , Total13,871 7,139 24,687 46,462

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, , ,849, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,285, , , ,034, Total 1,689, ,797 2,941, ,581,63 4

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)) = (( / 1.0) * 13,861 + (1,688,640 * 8 / 1.0) + (( / 11.0) * 2 + (80 * 8 / 11.0) + (( / 24.0) * 7 + (280 * 8 / 24.0) + (( / 54.0) * 1 + (40 * 8 / 54.0) = 21,165,613 us (7.06%) Beacon

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)) = (( / 1.0) * 6,547 + (838,510 * 8 / 1.0) + (( / 2.0) * 21 + (10,019 * 8 / 2.0) + (( / 5.5) * 13 + (12,633 * 8 / 5.5) + (( / 6.0) * 2 + (1,590 * 8 / 6.0) + (( / 9.0) * 3 + (2,631 * 8 / 9.0) + (( / 11.0) * (76,565 * 8 / 11.0) + (( / 12.0) * 2 + (3,060 * 8 / 12.0) + (( / 18.0) * 7 + (10,198 * 8 / 18.0) + (( / 24.0) * 4 + (3,154 * 8 / 24.0) + (( / 48.0) * 10 + (13,509 * 8 / 48.0) + (( / 54.0) * 20 + (17,928 * 8 / 54.0) = 10,754,454us (3.58%) Occupied Time DIFSCWTX TIME Probe Request

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

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)) = (( / /1.0+14*8/1.0) * 24,606 + (2,849,896 * 8 / 1.0) + (( / / * 8 / 1.0) * 4 + (5,257 * 8 / 2.0) + (( / / * 8 / 1.0) * 7 + (10,710 * 8 / 5.5) + (( / / * 8 / 1.0) * 1 + (1,530 * 8 / 6.0) + (( / / * 8 / 1.0) * 1 + (1,530 * 8 / 9.0) + (( / / * 8 / 1.0) * 15 + (13,848 * 8 / 11.0) + (( / / * 8 / 1.0) * 4 + (6,120 * 8 / 12.0) + (( / / * 8 / 1.0) * 7 + (8,212 * 8 / 18.0) + (( / / * 8 / 1.0) * 6 + (5,279 * 8 / 24.0) + (( / / * 8 / 1.0) * 3 + (4,590 * 8 / 36.0) + (( / / * 8 / 1.0) * 2 + (2,259 * 8 / 48.0) + (( / / * 8 / 1.0) * 31 + (32,100 * 8 / 54.0) = 44,215,439us (14.74%)

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) Beacon Probe Req Probe Res Others Total

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.

Submission doc.: IEEE 11-11/1413r4January 2012 Katsuo Yunoki, KDDI R&D LaboratoriesSlide 17 Example of retry frames (Probe Response) No.TimeSourceDestinationInfoSN XXXX_c5:83:c 1 XXXX:16:4c:f2 Probe Response, SN=2066, FN=0, Flags=..m.....C, BI=100, SSID=ABC XXXX_c5:83:c 6 XXXX:16:4c:f2 Probe Response, SN=2067, FN=0, Flags= C, BI=100, SSID=\000"" XXXX_c5:83:c 6 XXXX:16:4c:f2 Probe Response, SN=2067, FN=0, Flags=....R...C, BI=100, SSID=\000"" XXXX_c5:83:c 6 XXXX:16:4c:f2 Probe Response, SN=2067, FN=0, Flags=....R...C, BI=100, SSID=\000"" XXXX:c5:58:91XXXX:16:4c:f2 Probe Response, SN=71, FN=0, Flags= C, BI=100, SSID= XXXX_c5:83:c 0 XXXX:16:4c:f2 Probe Response, SN=2068, FN=0, Flags=..m.....C, BI=100, SSID=XYZ XXXX_c5:83:c 1 XXXX:16:4c:f2 Probe Response, SN=2069, FN=0, Flags=..m.....C, BI=100, SSID=ABC XXXX_c5:83:c 1 XXXX:16:4c:f2 Probe Response, SN=2069, FN=0, Flags=..m.....C, BI=101, SSID=ABC XXXX_c5:83:c 1 XXXX:16:4c:f2 Probe Response, SN=2069, FN=0, Flags=..m.....C, BI=102, SSID=ABC XXXX_c5:83:c 6 XXXX:16:4c:f2 Probe Response, SN=2070, FN=0, Flags= C, BI=100, SSID=\000"" XXXX:42:60:c4Broadcast Probe Response, SN=3699, FN=0, Flags= C, BI=100, SSID= XXXX:c5:58:91XXXX:16:4c:f2 Probe Response, SN=72, FN=0, Flags= C, BI=100, SSID= XXXX:c5:58:91XXXX:16:4c:f2 Probe Response, SN=72, FN=0, Flags=....R...C, BI=100, SSID= XXXX:c5:58:91XXXX:16:4c:f2 Probe Response, SN=73, FN=0, Flags= C, BI=100, SSID= XXXX_c5:83:c 0 XXXX:16:4c:f2 Probe Response, SN=2071, FN=0, Flags=..m.....C, BI=100, SSID=XYZ XXXX_c5:83:c 0 XXXX:16:4c:f2 Probe Response, SN=2071, FN=0, Flags=..m.....C, BI=101, SSID=XYZ XXXX_c5:83:c 0 XXXX:16:4c:f2 Probe Response, SN=2071, FN=0, Flags=..m.....C, BI=102, SSID=XYZ XXXX_c5:83:c 0 XXXX:16:4c:f2 Probe Response, SN=2071, FN=0, Flags=..m.....C, BI=103, SSID=XYZ XXXX:c5:58:91 XXXX:54:de:0 a Probe Response, SN=74, FN=0, Flags= C, BI=100, SSID= XXXX:c5:58:91 XXXX:54:de:0 a Probe Response, SN=74, FN=0, Flags=....R...C, BI=100, SSID= XXXX:c5:58:91 XXXX:54:de:0 a Probe Response, SN=74, FN=0, Flags=....R...C, BI=100, SSID= XXXX:c5:58:91 XXXX:54:de:0 a Probe Response, SN=74, FN=0, Flags=....R...C, BI=100, SSID= XXXX_c5:83:c 0 XXXX:54:de:0 a Probe Response, SN=2080, FN=0, Flags=..m.....C, BI=100, SSID=XYZ XXXX_c5:83:c 1 XXXX:54:de:0 a Probe Response, SN=2081, FN=0, Flags=..m.....C, BI=100, SSID=ABC 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

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 a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=11, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=5, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=6, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=6, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=6, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=11, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=7, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=7, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=9, FN=0, Flags= C, SSID=Broadcast a0:dd:e5:XXXXBroadcastProbe Request, SN=0, FN=0, Flags= C, SSID=Broadcast a0: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.

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.

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.

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