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Fast Moving Scan Channel

Fast Moving Scan Channel. Authors:. Date: 2013-01-07. Abstract. The presentation proposes an improvement to the Active Scanning mechanism in 2.4GHz ISM band to reduce the scanning time on unused channels. Conformance w/ TGai PAR & 5C. Motivation.

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Fast Moving Scan Channel

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  1. Fast Moving Scan Channel Authors: Date: 2013-01-07 YonghoSeok, LG Electronics

  2. Abstract • The presentation proposes an improvement to the Active Scanning mechanism in 2.4GHz ISM band to reduce the scanning time on unused channels. Yongho Seok, LG Electronics

  3. Conformance w/ TGai PAR & 5C Yongho Seok, LG Electronics

  4. Motivation • In 2.4GHz ISM band, a STA scans the channel from Channel Number 1 to Channel Number 13. • For each channel to be scanned: • Wait until the ProbeDelay time has expired or a PHYRxStart.indication primitive has been received. • Perform the Basic Access procedure as defined in 9.3.4.2. • Send a probe request to the broadcast destination address, with the SSID and BSSID from the MLME-SCAN.request primitive. When the SSID List is present in the MLME-SCAN.request primitive, send one or more probe request frames, each with an SSID indicated in the SSID List and the BSSID from the MLME-SCAN.request primitive. • Set to 0 and start a ProbeTimer. • If PHY-CCA.indication (busy) primitive has not been detected before the ProbeTimer reaches MinChannelTime, then set NAV to 0 and scan the next channel, else when ProbeTimer reaches MaxChannelTime, process all received probe responses. • Set NAV to 0 and scan the next channel. Yongho Seok, LG Electronics

  5. Motivation • If other BSSs occupy adjacent channels of a scan channel, the transmission from other BSSs may trigger the PHY-CCA.indication (busy) primitive. • If there is no BSS occupying the current scan channel, the scan time overhead is increased to MaxChannelTime - MinChannelTime. Yongho Seok, LG Electronics

  6. Proposed FILS Active Scanning Procedure • For each channel to be scanned: • Wait until the ProbeDelay time has expired or a PHYRxStart.indication primitive has been received. • Perform the Basic Access procedure as defined in 9.3.4.2. • Send a probe request to the broadcast destination address, with the SSID and BSSID from the MLME-SCAN.request primitive. When the SSID List is present in the MLME-SCAN.request primitive, send one or more probe request frames, each with an SSID indicated in the SSID List and the BSSID from the MLME-SCAN.request primitive. • Set to 0 and start a ProbeTimer. • If PHY-CCA.indication (busy) primitive has not been detected before the ProbeTimer reaches MinChannelTime, then set NAV to 0 and scan the next channel, else when ProbeTimer reaches MaxChannelTime, process all received probe responses. • If PHY-RxStart.indication primitive has not been received before the ProbeTimer reaches MinChannelTime, then STAs with dot11FILSActivated equal to true sets NAV to 0 and scans the next channel • Set NAV to 0 and scan the next channel. Yongho Seok, LG Electronics

  7. Probe Request PHY-CCA.indication (busy) • If PHY-CCA.indication (busy) primitive has been detected before the ProbeTimer reaches MinChannelTime, then STA scans the channel until ProbeTimer reaches MaxChannelTime. DATA MinChannelTime ACK MaxChannelTime Probe Request PHY-RxStart.indication& PHY-CCA.indication (busy) • If PHY-CCA.indication (busy) primitive has been detected before the ProbeTimer reaches MinChannelTime, then STA scans the channel until ProbeTimer reaches MaxChannelTime. DATA MinChannelTime ACK Probe Response MaxChannelTime <Current Scanning Procedure> Yongho Seok, LG Electronics

  8. Probe Request PHY-CCA.indication (busy) • If PHY-RxStart.indication primitive has not been received before the ProbeTimer reaches MinChannelTime, then STAs with dot11FILSActivated equal to true sets NAV to 0 and scans the next channel DATA MinChannelTime ACK Probe Request PHY-RxStart.indication& PHY-CCA.indication (busy) • If PHY-RxStart.indication primitive has been received before the ProbeTimer reaches MinChannelTime, then STA scans the channel until ProbeTimer reaches MaxChannelTime. DATA MinChannelTime ACK Probe Response MaxChannelTime <Proposed FILS Scanning Procedure> Yongho Seok, LG Electronics

  9. Proposed FILS Active Scanning Procedure • In many countries, the non-overlapping channel set (1, 5, 9, 13 or 1, 6, 11) is recommended. • When only 1, 5, 9, 13 channels are occupied, the proposed FILS active scanning procedure can reduce the scanning time from MaxChannelTime*13 to MaxChannelTime*4 + MinChannelTime*9 • MinChannelTime: 5ms • MaxChannelTime: 10ms • The gain of the scanning time is about 34% (from 130ms to 85ms) Yongho Seok, LG Electronics

  10. Conclusion • In 2.4GHz ISM band, as IEEE 802.11n 40MHz BSS is more crowded, PHY-CCA.indication (busy) probability on adjacent channels is more increasing. • This presentation proposes to scan the next channel if a STA does not receive a valid PLCP header during MinChannelTime. Yongho Seok, LG Electronics

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