1. doc.: IEEE 802.11-10/1282r0 Submission November 2010 Eldad Perahia, Intel CorporationSlide 1 PLCP Rx Procedure Date: 2009-11-08 Authors:

2. doc.: IEEE 802.11-10/1282r0 Submission November 2010 Eldad Perahia, Intel CorporationSlide 2 Abstract PLCP Rx procedure for TGac

3. doc.: IEEE 802.11-10/1282r0 Submission November 2010 Eldad Perahia, Intel CorporationSlide 3 Background PLCP receive procedure is clause 20.3.24 in 11n First decision: Auto-detection between 11n MF and 11n GF preamble Second decision: Auto-detection between 11a/g and 11n MF HT-SIG processing and CRC –Check for unsupported preamble, unsupported mode, and Reserved HT-SIG indication Data symbol processing Signal extension: time alignment with 11b 2.4GHz devices

4. doc.: IEEE 802.11-10/1282r0 Submission November 2010 Eldad Perahia, Intel CorporationSlide 4 CCA Behavior in 11n Carrier lost –Before HT-SIG => Energy detect (ED) based on minimum sensitivity + 20dB –After HT-SIG => defer for TXTIME HT-SIG processing –Not HT-SIG => 11a/g processing –CRC fail => ED based on minimum sensitivity + 20dB –Unsupported preamble (GF) => ED based on minimum sensitivity + 10dB –Reserved HT-SIG indication (MCS of 77-127, or Reserved field = 0, or STBC field = 3) => ED based on minimum sensitivity + 20dB –Unsupported mode => defer for TXTIME L-SIG parity –Can be ignored

5. doc.: IEEE 802.11-10/1282r0 Submission November 2010 Eldad Perahia, Intel CorporationSlide 5 Overview of Rx Procedure in 11ac First decision: Auto-detection between VHT and 11n GF preamble (is the first SIG field L-SIG?) Second decision: Auto-detection between VHT and 11n MF preamble (does HT-SIG follow L-SIG?) Third decision: Auto-detection between VHT and 11a preamble (does VHT-SIG-A follow L-SIG?) VHT-SIG-A processing and CRC –Check for unsupported mode and Reserved VHT-SIG-A Indication VHT-SIG-B receiver decoding optional for SU, mandatory for MU VHT-SIG-B CRC checking in SERVICE field optional for both SU and MU Data processing for N_sym symbols

6. doc.: IEEE 802.11-10/1282r0 Submission November 2010 Eldad Perahia, Intel CorporationSlide 6 CCA Behavior in 11ac (1/2) Carrier lost –Before L-SIG => Energy detect (ED) based on minimum sensitivity + 20dB –After L-SIG => defer for RXTIME L-SIG processing –Compute RXTIME from L_Length –If Parity fail => ED VHT-SIG-A processing –Not VHT-SIG => 11a processing –defer for RXTIME for CRC fail, unsupported modes, Reserved VHT-SIG Indication –Examples of Reserved VHT-SIG Indication Reserved bits equal to 0 Short GI set to 01 Unsupported combinations of N_sts and MCS

7. doc.: IEEE 802.11-10/1282r0 Submission November 2010 Eldad Perahia, Intel CorporationSlide 7 CCA Behavior in 11ac (2/2) VHT-SIG-B processing –Optional if SU transmission (indicated by Group ID in VHT-SIG- A equal to 63) If processed and Reserved VHT-SIG Indication, defer for RXTIME –For MU transmission, defer for RXTIME if unsupported mode Optional VHT-SIG-B CRC checking in SERVICE field –If checked and failed, defer for RXTIME

8. doc.: IEEE 802.11-10/1282r0 Submission November 2010 Eldad Perahia, Intel CorporationSlide 8 RXTIME and Rx N_sym Predicted duration of the transmitted frame is computed from L-SIG Computation of number of symbols in the PSDU for BCC –Correction for short GI ambiguity

9. doc.: IEEE 802.11-10/1282r0 Submission November 2010 Eldad Perahia, Intel CorporationSlide 9 Summary Only one preamble in 11ac, auto-detect is only between single VHT preamble type and legacy formats Duration of the PPDU (RXTIME) computed from L- SIG After valid L-SIG, any error in processing results in deferral based on RXTIME VHT-SIG-B processing optional for SU Checking VHT-SIG-B CRC in SERVICE field optional for both SU and MU