1 / 8

CCA – CID 537 discussion

CCA – CID 537 discussion. Authors:. Date: 2011-05-03. 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

destiny-hurst
Download Presentation

CCA – CID 537 discussion

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CCA – CID 537 discussion Authors: Date: 2011-05-03 Eldad Perahia, Intel Corporation

  2. 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 Eldad Perahia, Intel Corporation

  3. 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) Eldad Perahia, Intel Corporation

  4. 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” Eldad Perahia, Intel Corporation

  5. 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 Eldad Perahia, Intel Corporation

  6. 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). Eldad Perahia, Intel Corporation

  7. 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 (< 4μs) and hold the CCA signal busy (PHY_CCA.indicate(BUSY,channel-list)) for the duration of the PPDU with >90% probability.” • This permits dropping CCA due to acquisition or L-SIG failure for up to 10% of the packets Eldad Perahia, Intel Corporation

  8. 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 Eldad Perahia, Intel Corporation

More Related