1. RTS CTS Rule Amendment Date: 2011-01-17 Authors: Date: January 2011
Feb, 2008
doc.: IEEE /xxxx
Date: January 2011
RTS CTS Rule Amendment
Date:
Authors:
L. Chu et al
Liwen Chu, STMicroelectronics

2. RTS/CTS and NAV Updating Rules in 802.11 Baseline
Feb, 2008
doc.: IEEE /xxxx
Date: January 2011
RTS/CTS and NAV Updating Rules in 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 P527 L56)
Normal
RTS
A-MPDU
Normal
RTS
A-MPDU
HT AP
RA=STA1
CTS
BlkAck
RA=STA2
HT STA1
CTS
BlkAck
11a STA2
Set NAV with TXOP holder AP
RTS’s TA matches NAV’s TXOP holder. STA2 sends CTS.
L. Chu et al
Liwen Chu, STMicroelectronics

3. RTS to Legacy STA Protected by RTS with Group TA
Feb, 2008
doc.: IEEE /xxxx
Date: January 2011
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 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
A-MPDU
Normal
RTS
VHT AP
RA=STA1
CTS
BlkAck
VHT STA1
11a STA2
Set NAV with group TXOP holder
TA does not match group TXOP holder.
Discard RTS.
VHT AP
11a STA2
VHT STA1
L. Chu et al
Liwen Chu, STMicroelectronics

4. RTS/CTS Rule Amendment
Feb, 2008
doc.: IEEE /xxxx
Date: January 2011
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
Liwen Chu, STMicroelectronics

5. Feb, 2008
doc.: IEEE /xxxx
Date: January 2011
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
Liwen Chu, STMicroelectronics