Non-Primary Channel Access (NPCA) Follow Up
This document, dated May 2024, provides an update on Non-Primary Channel Access (NPCA) as per slides presented by Minyoung Park and others from Intel Corporation. The content discusses the latest developments and insights related to NPCA in the context of IEEE 802.11 standards. It aims to address key considerations and advancements in channel access mechanisms for enhanced wireless communication.
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May 2024 doc.: IEEE 802.11-24/0495r0 Non-Primary Channel Access (NPCA) Follow Up Date: 2024-05-10 Authors: Name Minyoung Park Affiliations Intel Corporation Address Phone email Laurent Cariou Juan Fang Dibakar Das Po-Kai Huang Dmitry Akmetov Danny Alexander Submission Slide 1 Minyoung Park, et.al., Intel Corporation
May 2024 doc.: IEEE 802.11-24/0495r0 NPCA primary channel In 11-24/2005, to manage the complexity of the NPCA operation, we proposed to limit the number of secondary channels on which the non-primary channel access can take place while the primary channel is busy to one Define one NPCA primary channel One of the secondary channels of the BSS on which channel access is performed while the primary channel is busy AP announces the location of the NPCA primary channel Any available secondary channels of the BSS can be used for the NPCA operation Accessing the secondary channels of NPCA follows the same PIFS rules defined in the baseline frequency Potential NPCA operation Secondary channels of NPCA NPCA primary channel (P2) Secondary channels of BSS BSS Primary channel (P1) time Submission Slide 2 Minyoung Park, et.al., Intel Corporation
May 2024 doc.: IEEE 802.11-24/0495r0 Switching to NPCA primary channel and operating on NPCA primary/secondary channels Switching to the NPCA primary channel after detecting an OBSS HE/EHT/UHR PPDU (i.e., after detecting inter-BSS PPDU) Switching to the NPCA primary channel after a Control frame exchange of an OBSS is detected Switch delay Switch delay Data BA Data BA IR IR ICF ICF PIFS PIFS Secondary for P2 Secondary for P2 NPCA Primary(P2) NPCA Primary(P2) Secondary for P1 Secondary for P1 (AIFS+RBO) (AIFS+RBO) CTS Secondary for P2 Secondary for P2 Switch back to BSS primary before NAV expires or before the end of PPDU Switch back to BSS primary before NAV expires BSS Primary(P1) BSS Primary(P1) Data RTS or Data BA BA NAV set by RTS NAV set by CTS MU-RTS Switch to NPCA primary Switch to NPCA primary TXOP field aRxPHYStartDelay (20 usec) HE PPDU: HE-SIG-A EHT/UHR PPDU: U-SIG TXOP field OBSS frames OBSS frames 128 usec granularity if TXOP_Duration >= 512 usec My BSS frames My BSS frames ICF: initial control frame IR: immediate response Submission Slide 3 Minyoung Park, et.al., Intel Corporation
May 2024 doc.: IEEE 802.11-24/0495r0 Switching to NPCA primary channel 1. Switching after a control frame exchange (e.g., (MU-)RTS/CTS) Simple but may miss opportunities when TXOP doesn t start with a control frame exchange Switching based on the PHY header information of a PPDU This can cover the frame exchanges that don t start with a control frame exchange (e.g., (MU-)RTS/CTS) but needs to define rules for different types of PPDU as follows: HE PPDU: HE-SIG-A field carries: BSS Color, Bandwidth, TXOP fields BSS Color used to detect inter-BSS PPDU Bandwidth field: the bandwidth of the PPDU TXOP field used to set the duration of the duration of the NPCA operation on the NPCA primary/secondary channels (TXOP duration value is 128 usec granularity for TXOP Duration >=512 usec) EHT/UHR PPDU: U-SIG field carries: BSS Color, Bandwidth, TXOP fields Usage is same as the HE PPDU case VHT PPDU: VHT-SIG-A field carries: BW, Group ID, Partial AID fields Group ID and Partial AID fields can be used to detect inter-BSS PPDU (i.e., OBSS PPDU) BW field: the bandwidth of the PPDU LENGTH field of L-SIG field may be used to set the duration of the NPCA operation on the NPCA primary/secondary channels but doesn t provide TXOP information Non-HT or HT PPDU: Doesn t have the information in the PHY preamble to detect inter-BSS PPDU and the duration, thus only way is to decode the MAC header, but this is a problem since the timing of when the MAC header information is available is implementation dependent and has to check FCS at the end of the PPDU. When switching is based on the PHY preamble of an OBSS PPDU, we suggest to include HE/EHT/UHR PPDUs that contain necessary information (OBSS, BW, TXOP) for the NPCA operation 2. Submission Slide 4 Minyoung Park, et.al., Intel Corporation
May 2024 doc.: IEEE 802.11-24/0495r0 EDCA parameters on the NPCA primary channel For simplicity, same EDCA parameters (CWmin/max/TXOP limit ) defined in (MU) EDCA Parameter Set are applied on the BSS primary channel and the NPCA primary channel Submission Slide 5 Minyoung Park, et.al., Intel Corporation
May 2024 doc.: IEEE 802.11-24/0495r0 Summary Define one NPCA primary channel One of the secondary channels of the BSS on which channel access is performed while the primary channel is busy The event that triggers switching to the NPCA primary channel An OBSS control frame exchange (e.g., (MU-)RTS/CTS) OBSS HE/EHT/UHR PPDU Upon switching to the NPCA primary channel Same EDCA parameters of the BSS primary channel apply to the NPCA primary channel Submission Slide 6 Minyoung Park, et.al., Intel Corporation
May 2024 doc.: IEEE 802.11-24/0495r0 SP1 Do you support the following in the NPCA operation? In 802.11bn, the event that triggers switching to the NPCA primary channel shall be OBSS Control frame exchange (e.g., (MU-)RTS/CTS) or OBSS HE/EHT/UHR PPDU Submission Slide 7 Minyoung Park, et.al., Intel Corporation
May 2024 doc.: IEEE 802.11-24/0495r0 SP2 Do you support the following in the NPCA operation? In 802.11bn, the NPCA operation shall use the same EDCA parameters ((MU) EDCA Parameter Set, EPCS EDCA Parameters), on both the BSS primary channel and the NPCA primary channel. Submission Slide 8 Minyoung Park, et.al., Intel Corporation
