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

doc.: IEEE /0562r0 Submission Overview Receive Procedure ( ) 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

doc.: IEEE /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 MHz.” –The channel-list DOES NOT include secondary channels, only primary channel (or absent with 20 MHz) May 2011 Eldad Perahia, Intel CorporationSlide 3

doc.: IEEE /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 (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 (CCA sensitivity).” No definition in for “missed preamble” May 2011 Eldad Perahia, Intel CorporationSlide 4

doc.: IEEE /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 ( ), 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

doc.: IEEE /0562r0 Submission Possible Solution Delete error conditions from Receiver Procedure and simply refer to 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 (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 (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 (CCA sensitivity). May 2011 Eldad Perahia, Intel CorporationSlide 6

doc.: IEEE /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 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 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

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