Real Air-time Occupation by Beacon and Probe January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 Real Air-time Occupation by Beacon and Probe Date: 2012-01-16 Authors: Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 Abstract This document shows retry numbers of Probe Response as the answer for discussion in Atlanta. (Slide 16) Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 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. Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

Real world (1) Number of Smart-phone is increasing. January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 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. Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 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. Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

Conditions Time/Date: Around 18:00 / October 11(Tue), 2011 January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 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) <Equipment> Thinkpad X200 Windows XP USB Wireless Monitor Adoptor (Air Pcap NX) Wireshark Measured CH Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

Result Observed frames January 2012 Frames Bytes Count % Beacon 13,871 doc.: IEEE 802.11-11/1413r4 January 2012 Result Observed frames Frames Bytes Count % Beacon 13,871 15.05 1,689,040 9.82 Probe Request 7,139 7.75 989,797 5.75 Probe Response 24,687 26.79 2,941,331 17.10 Other 46,462 50.42 11,581,634 67.33 Total 92,159 17,201,802 Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

Result (cont.) Frames Bytes Time occupation is more important. January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 Result (cont.) Frames Bytes Time occupation is more important. Doc. IEEE802.11-11/1031r0 was referred for time occupation analysis. Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

Transmission Rate January 2012 January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 Transmission Rate Rate [Mbps] Beacon Probe Request Probe Response Others Frames % 1 13,861 99.93 6,547 91.71 24,606 99.67 12,956 27.89 2 0.00 21 0.29 4 0.02 504 1.08 6 13 0.18 7 0.03 467 1.01 113 0.24 9 3 0.04 230 0.50 11 0.01 510 7.14 15 0.06 2,766 5.95 12 288 0.62 18 0.10 341 0.73 24 0.05 13,793 29.69 36 1,309 2.82 48 10 0.14 1,953 4.20 54 20 0.28 31 0.13 11,742 25.27 Total 13,871 7,139 24,687 46,462 Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

Transmission Rate (cont.) January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 Transmission Rate (cont.) Rate [Mbps] Beacon Probe Request Probe Response Others Bytes % 1 1,688,640 99.98 838,510 84.72 2,849,896 96.89 871,812 7.53 2 0.00 10,019 1.01 5,257 0.18 466,650 4.03 6 12,633 1.28 10,710 0.36 531,043 4.59 1,590 0.16 1,530 0.05 127,094 1.10 9 2,631 0.27 301,819 2.61 11 80 76,565 7.74 13,848 0.47 687,560 5.94 12 3,060 0.31 6,120 0.21 215,459 1.86 18 10,198 1.03 8,212 0.28 287,119 2.48 24 280 0.02 3,154 0.32 5,279 805,136 6.95 36 4,590 967,971 8.36 48 13,509 1.36 2,259 0.08 1,285,716 11.10 54 40 17,928 1.81 32,100 1.09 5,034,255 43.47 Total 1,689,040 989,797 2,941,331 11,581,634 Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

Occupied Time Calculation (Beacon) January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 Occupied Time Calculation (Beacon) Occupied Time Beacon DIFS CW TX 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%) Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

Occupied Time Calculation (Probe Request) January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 Occupied Time Calculation (Probe Request) Occupied Time Probe Request DIFS CW TX TIME 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%) Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

Occupied Time Calculation (Probe Response) January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 Occupied Time Calculation (Probe Response) Occupied Time Probe Response ACK DIFS CW TX TIME SIFS TX TIME aSlotTime: 20us aSIFSTime: 10us aPreambleLength: 144us aPLCPHeaderLength: 48bits aCWmin: 31 aCWmax: 1023 DIFS: 50us CW: 310us ACKRate: 1Mbps ACKLength: 14Bytes Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

Occupied Time Calculation (Probe Response) (Cont.) January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 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%) Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

Occupied Time Calculation Result January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 Occupied Time Calculation Result Packet type Occupancy rate (%) Occupied time (sec) Beacon 7.06 21.17 Probe Req. 3.58 10.75 Probe Res. 14.74 44.22 Others 74.62 223.86 Total 100.00 300.00 Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

Retry of Probe Response January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 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. Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

Example of retry frames (Probe Response) January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 Example of retry frames (Probe Response) Sequence Number No. Time Source Destination Info SN 1 0.503998 XXXX_c5:83:c1 XXXX:16:4c:f2 Probe Response, SN=2066, FN=0, Flags=..m.....C, BI=100, SSID=ABC 2066 2 0.5054 XXXX_c5:83:c6 Probe Response, SN=2067, FN=0, Flags=........C, BI=100, SSID=\000"" 2067 3 0.506277 Probe Response, SN=2067, FN=0, Flags=....R...C, BI=100, SSID=\000"" 4 0.507278 5 0.521844 XXXX:c5:58:91 Probe Response, SN=71, FN=0, Flags=........C, BI=100, SSID=12345678 71 6 0.523116 XXXX_c5:83:c0 Probe Response, SN=2068, FN=0, Flags=..m.....C, BI=100, SSID=XYZ 2068 7 0.524523 Probe Response, SN=2069, FN=0, Flags=..m.....C, BI=100, SSID=ABC 2069 8 0.525524 Probe Response, SN=2069, FN=0, Flags=..m.....C, BI=101, SSID=ABC 9 0.526525 Probe Response, SN=2069, FN=0, Flags=..m.....C, BI=102, SSID=ABC 10 0.52778 Probe Response, SN=2070, FN=0, Flags=........C, BI=100, SSID=\000"" 2070 11 0.53265 XXXX:42:60:c4 Broadcast Probe Response, SN=3699, FN=0, Flags=........C, BI=100, SSID=12345678 3699 12 0.544779 Probe Response, SN=72, FN=0, Flags=........C, BI=100, SSID=12345678 72 13 0.545903 Probe Response, SN=72, FN=0, Flags=....R...C, BI=100, SSID=12345678 14 0.565153 Probe Response, SN=73, FN=0, Flags=........C, BI=100, SSID=12345678 73 15 0.566405 Probe Response, SN=2071, FN=0, Flags=..m.....C, BI=100, SSID=XYZ 2071 16 0.571022 Probe Response, SN=2071, FN=0, Flags=..m.....C, BI=101, SSID=XYZ 17 0.573148 Probe Response, SN=2071, FN=0, Flags=..m.....C, BI=102, SSID=XYZ 18 0.574025 Probe Response, SN=2071, FN=0, Flags=..m.....C, BI=103, SSID=XYZ 19 0.575399 XXXX:54:de:0a Probe Response, SN=74, FN=0, Flags=........C, BI=100, SSID=9876543 74 20 0.576649 Probe Response, SN=74, FN=0, Flags=....R...C, BI=100, SSID=9876543 21 0.578148 22 0.579281 23 0.594025 Probe Response, SN=2080, FN=0, Flags=..m.....C, BI=100, SSID=XYZ 2080 24 0.595282 Probe Response, SN=2081, FN=0, Flags=..m.....C, BI=100, SSID=ABC 2081 25 0.596399 Probe Response, SN=2082, FN=0, Flags=........C, BI=100, SSID=\000"" 2082 Retry Retry Retry Retry Retry Retry Retry Retry Retry Retry Retry Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

Example of Active Scanning (Probe Request) January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 Example of Active Scanning (Probe Request) This is my personal smart-phone  No. Time Source Destination Info 1 a0:dd:e5:XXXX Broadcast Probe Request, SN=0, FN=0, Flags=........C, SSID=Broadcast 2 0.239642 Probe Request, SN=9, FN=0, Flags=........C, SSID=Broadcast 3 0.34641 4 0.57052 5 0.637521 Probe Request, SN=11, FN=0, Flags=........C, SSID=Broadcast 6 7.956037 7 8.103645 Probe Request, SN=5, FN=0, Flags=........C, SSID=Broadcast 8 8.216269 9 42.444982 10 42.589602 Probe Request, SN=6, FN=0, Flags=........C, SSID=Broadcast 11 42.669104 12 59.414604 13 59.610478 14 59.68948 15 76.896361 16 77.057485 17 77.116107 18 77.162501 19 94.449135 20 94.644904 Probe Request, SN=7, FN=0, Flags=........C, SSID=Broadcast 21 94.690512 22 111.747534 23 111.962168 24 111.987446 25 119.520411 26 119.73995 Multiple shots of Probe request were transmitted for a timing. It may be vender implementation. The second timing is around timestamp=8.00. Katsuo Yunoki, KDDI R&D Laboratories

Considerations (Opinion) January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 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. Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

January 2012 doc.: IEEE 802.11-11/1413r4 January 2012 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. Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories

References doc. IEEE802.11-11/1031r0 January 2012 Katsuo Yunoki, KDDI R&D Laboratories Katsuo Yunoki, KDDI R&D Laboratories