1. doc.: IEEE 802.11-11/0562r0 Submission May 2011 Eldad Perahia, Intel CorporationSlide 1 CCA – CID 537 discussion Date: 2011-05-03 Authors:

2. doc.: IEEE 802.11-11/0562r0 Submission Overview Receive Procedure (22.3.22) describes how to set PHY-CCA.indication when various conditions occur, such as –Signal loss before validating L-SIG –check of the L-SIG parity bit is not valid Language in these two conditions borrows the phase “missed preamble” from 11n, however it is not defined in 11ac CID 537 states: –"missed preamble" language is not used anymore Further discussion questioned whether CCA indication applies to primary or secondary channels May 2011 Eldad Perahia, Intel CorporationSlide 2

3. doc.: IEEE 802.11-11/0562r0 Submission Initial Steps in Receive Procedure “… A PHY-CCA.indication(BUSY, channel-list) shall also be issued as an initial indication of reception of a signal.” “The channel-list parameter of the PHY- CCA.indication is absent when the operating channel width is 20 MHz and includes the element “primary” when the operating channel width is 40 MHz, 80 MHz, 160 MHz or 80+80 MHz.” –The channel-list DOES NOT include secondary channels, only primary channel (or absent with 20 MHz) May 2011 Eldad Perahia, Intel CorporationSlide 3

4. doc.: IEEE 802.11-11/0562r0 Submission Error Conditions in Receive Procedure “If signal loss occurs before validating L-SIG, the VHT PHY shall maintain PHY-CCA.indication(BUSY, channel-list) until the received level drops below the CCA sensitivity level (for a missed preamble) specified in 22.3.20.5 (CCA sensitivity).” “If the check of the L-SIG parity bit is not valid… The VHT PHY shall maintain PHY-CCA.indication(BUSY, channel-list) until the received level drops below the CCA sensitivity level (for a missed preamble) specified in 22.3.20.5 (CCA sensitivity).” No definition in 22.3.20.5 for “missed preamble” May 2011 Eldad Perahia, Intel CorporationSlide 4

5. doc.: IEEE 802.11-11/0562r0 Submission Example Assume we define “missed preamble” to -62 dBm as in 11n Then consider the case where we have an invalid check of L-SIG parity bit and the level of the signal is -65 dBm on both primary and secondary In this case, PHY-CCA.indication on the primary switches to IDLE However according to the CCA sensitivity section (22.3.20.5), the PHY shall issue a PHY-CCA.indication(BUSY, {secondary}) at -72 dBm So we have a condition in which the PHY-CCA.indication is IDLE on the primary and BUSY on the secondary for the same signal May 2011 Eldad Perahia, Intel CorporationSlide 5

6. doc.: IEEE 802.11-11/0562r0 Submission Possible Solution Delete error conditions from Receiver Procedure and simply refer to 22.3.20.5 for CCA sensitivity rules, as follows “… A PHY-CCA.indication(BUSY, channel-list) shall is also be issued as an initial indication of reception of a signal, as specified in 22.3.20.5 (CCA sensitivity).” “After the PHY-CCA.indication(BUSY, channel-list) is issued, the PHY entity shall begin receiving the training symbols and searching for L-SIG and VHT-SIG-A in order to set the maximum duration of the data stream. If signal loss occurs before validating L-SIG, the VHT PHY shall maintain PHY-CCA.indication(BUSY, channel-list) until the received level drops below the CCA sensitivity level (for a missed preamble) specified in 22.3.20.5 (CCA sensitivity). If the check of the L-SIG parity bit is not valid, a PHYRXSTART.indication is not issued. The PHY shall issue the error condition PHY-RXEND.indication(FormatViolation). The VHT PHY shall maintain PHY-CCA.indication(BUSY, channel-list) until the received level drops below the CCA sensitivity level (for a missed preamble) specified in 22.3.20.5 (CCA sensitivity). May 2011 Eldad Perahia, Intel CorporationSlide 6

7. doc.: IEEE 802.11-11/0562r0 Submission CCA Sensitivity Modification (1/2) Replace “The start of a PPDU that occupies at least the primary 20 MHz channel under the conditions listed in Table 22-22 shall be detected with >90% probability within a period of aCCATime (< 4μs).” with “The PHY shall detect the start of a PPDU that occupies at least the primary 20 MHz channel under the conditions listed in Table 22-22 within a period of aCCATime ( 90% probability.” This permits dropping CCA due to acquisition or L- SIG failure for up to 10% of the packets May 2011 Eldad Perahia, Intel CorporationSlide 7

8. doc.: IEEE 802.11-11/0562r0 Submission CCA Sensitivity Modification (1/2) Remove “Any signal within the primary 20 MHz channel at or above -62 dBm” from Table 22-22 Add “The receiver shall hold the CCA signal busy for any signal 20 dB or more above the minimum modulation and coding rate sensitivity (–82 + 20 = –62 dBm) in the primary 20 MHz channel.” after Table 22- 22 May 2011 Eldad Perahia, Intel CorporationSlide 8