Considerations for early NAV indication
This document explores the potential for improved packet protection through the use of early NAV indication within the ACK indication bits of the SIG field. It proposes leveraging the reserved "11" value in the ACK indication to signal additional NAV settings beyond standard ACK or Block Acknowledgment (BA). This enhancement seeks to address issues arising from hidden node problems where an STA may miss critical packets, offering a method to defer medium access based on NAV settings to prevent disruptions during ongoing transmissions.
Considerations for early NAV indication
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Presentation Transcript
Considerations for early NAV indication Authors: • Date:2012-05-11 Sudheer Grandhi, InterDigital Communications
Abstract • This document discusses possibility of additional packet protection using NAV indication in the ACK indication field. Sudheer Grandhi, InterDigital Communications
Early ACK indication • ACK indication field (2 bits) In the SIG or SIGA field • Indicate whether an immediate response is requested right after the PPDU, and also the type of the response (00: ACK; 01: BA; 10: No ACK; 11: reserved) • If a STA decodes the SIG correctly, but 1) decides to skip the remaining fields after SIG for power saving, or 2) is not able to decode /verify the MAC header, it can determine whether to defer medium access for ACK protection based on the ACK Indication in SIG Sudheer Grandhi, InterDigital Communications
Issues in Packet Protection • Due to hidden node problem, a STA cannot always hear all packets in a packet exchange • Frames could have no ACK but contains NAV setting in the Duration Field of the MAC header • RTS • CTS Sudheer Grandhi, InterDigital Communications
Proposal: further NAV Indication using ACK Indication bits (1/2) • Use the reserved “11” in the ACK indication bits in SIG field as NAV setting indicator for NAV settings other than Normal ACK or BA • If there is NAV setting in the MAC header other than Normal ACK or BA, an unintended receiving STA should • decode the MAC header to obtain the Duration Field and set NAV accordingly • or if the STA cannot decode the MAC header, it candefer medium access by a default value (TBD) to prevent premature medium access that would interrupt ongoing packet transmission or receptions Sudheer Grandhi, InterDigital Communications
Summary • The current ACK Indication may be extended for additional packet/NAV protection other than ACK or BA • Proposal: • Use of “11” value of ACK Indication bits to offer packet/NAV protection for frames other than Normal ACK or BA Sudheer Grandhi, InterDigital Communications
Questions / Comments ? Thank You! Sudheer Grandhi, InterDigital Communications
Straw Poll 1 • Do you think that the use of the reserved “11” value of the ACK Indication in the SIG field should be further studied to allow additional packet/NAV protection? • Yes • No • Abstain Sudheer Grandhi, InterDigital Communications
References • [1] IEEE Std 802.11™-2012: Wireless LAN MAC and PHY Specifications • [2] IEEE 802.11-11/1482r4, “Preamble Format for 1 MHz,” Qualcomm and et. al. • [3] IEEE 802.11-12/0119r0, “Early ACK Indication,” Marvell and et. al. Sudheer Grandhi, InterDigital Communications