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RTS CTS Rule Amendment

RTS CTS Rule Amendment. Authors:. Date: 2011-01-17. RTS/CTS and NAV Updating Rules in 802.11 Baseline.

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RTS CTS Rule Amendment

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  1. RTS CTS Rule Amendment Authors: Date: 2011-01-17 L. Chu et al

  2. RTS/CTS and NAV Updating Rules in 802.11 Baseline • A STA shall save the TXOP holder address for the BSS in which it is associated, which is the MAC address from the Address 2 field of the frame that initiated a frame exchange sequence except when this is a CTS frame, in which case the TXOP holder address is the Address 1 field. If an RTS frame is received with the RA address matching the MAC address of the STA and the MAC address in the TA field in the RTS frame matches the saved TXOP holder address, then the STA shall send the CTS frame after SIFS, without regard for, and without resetting, its NAV. (Revmb 6.0 subclause 9.19.2.2 P527 L56) Normal RTS Normal RTS A-MPDU A-MPDU HT AP RA=STA1 RA=STA2 CTS BlkAck HT STA1 BlkAck CTS 11a STA2 Set NAV with TXOP holder AP RTS’s TA matches NAV’s TXOP holder. STA2 sends CTS. L. Chu et al

  3. RTS to Legacy STA Protected by RTS with Group TA • In a TXOP protected by RTS with group TA, if the TXOP Holder transmits a RTS to a legacy STA, the legacy STA will discard the RTS since the TA (uncast MAC address) does not match the group TXOP holder. • Per 802.11 baseline specification, the VHT AP may transmit RTS again to the legacy STA after the CS mechanism indicates that the medium is idle at the TxPIFS slot boundary before the expiry of the TXNAV timer since the AP does not receive the responding CTS from the legacy STA. • This will waste channel bandwidth and AP’s power. So it should be avoided. RTS of group TA Normal RTS A-MPDU VHT AP BlkAck RA=STA1 CTS VHT STA1 11a STA2 TA does not match group TXOP holder. Discard RTS. Set NAV with group TXOP holder VHT AP VHT STA1 11a STA2 L. Chu et al

  4. RTS/CTS Rule Amendment • A STA shall save the TXOP holder address for the BSS in which it is associated, which is the MAC address from the Address 2 field of the frame that initiated a frame exchange sequence except when this is a CTS frame, in which case the TXOP holder address is the Address 1 field. If an RTS frame is received with the RA address matching the MAC address of the STA and the MAC address in the TA field in the RTS frame matches the saved TXOP holder address, then the STA shall send the CTS frame after SIFS, without regard for, and without resetting, its NAV. • If a VHT STA initiates a TXOP by transmitting a RTS with the Multicast/Unicast bit being set to Multicast in TA, the VHT STA shall not send a RTS to a legacy STA in the TXOP. • When a VHT STA receives a RTS with group TA, the VHT STA uses the unicast TA of the TXOP holder to identify TXOP holder of the NAV timer. L. Chu et al

  5. Pre Motion • Do you support RTS/CTS rule amendment in slide 4: “If a VHT STA initiates a TXOP by transmitting a RTS with the Multicast/Unicast bit being set to Multicast in TA, the VHT STA shall not send a RTS to a legacy STA in the TXOP”. • Yes • No • Abstain L. Chu et al

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