1. 80MHz/160MHz Protection Date: 2010-09-14 Authors: Date: September 2010
Feb, 2008
doc.: IEEE /xxxx
Date: September 2010
80MHz/160MHz Protection
Date:
Authors:
L. Chu et al
Liwen Chu, STMicroelectronics

2. HT TXOP Protection and Truncation
Date: September 2010
HT TXOP Protection and Truncation
802.11n introduces features that a legacy STAs can not understand: 40MHz transmission, frame aggregation, short GI etc.
40MHz non-HT duplicate mode is used to protect the 11n transmission:
Non-HT duplicate frames (e.g. RTS/CTS) are used to establish protection of its TXOP in two 20MHz channels, and
Non-HT duplicate CF-End frame are used to truncate the protect TXOP protected by non-HT duplicate frames.
To get a 40MHz EDCA based TXOP, a STA does EDCA backoff procedure in the primary channel, and detects the second channel being idle during PIFS interval before the TXOP.
FC HT-STA1
RTS
ch0
A-MPDU
(HT frame)
FC HT-AP1
ch0+ch1
RTS
ch1
CTS
ch0
BLKACK
11a-STA3
ch0+ch1
FC HT-AP1
11a-AP2
FC HT-STA1
11a-AP3
CTS
ch1
11a-STA2
ch1
ch0+ch1
ch0
11a –STA2
NAV
ch0
“ch0(primary channel)+ch1” is a 40MHz channel.
ch0 is a 20MHz channel.
11a –STA3
NAV
ch1
ch1 is a 20MHz channel.

3. 802.11ac TXOP Protection and Truncation
Date: September 2010
802.11ac TXOP Protection and Truncation
802.11ac uses 80/160 MHz channels.
802.11ac introduces new features that legacy a STAs and n STAs can not understand: DL-MU MIMO, new ac preamble etc.
802.11ac TXOP should be protected by frames which can be understood by a STAs and n STAs in each 20MHz channel.
80MHz/160MHz non-HT duplicate frames are used for such TXOP protection/truncation:
80MHz/160MHz non-HT duplicate frame duplicates 20 MHz non-HT transmission in each 20 MHz channel of a 80MHz/160MHz channel.
80MHz/160MHz Non-HT duplicate frames (e.g. RTS/CTS) are used to establish protection of its TXOP in four 20MHz channels or in eight 20MHz channels, and
80MHz/160MHz Non-HT duplicate CF-End frame is used to truncate the protect TXOP protected by non-HT duplicate frames in four 20MHz channels or in eight 20MHz channels.

4. 802.11ac TXOP Protection and Truncation (Cont’d)
Date: September 2010
802.11ac TXOP Protection and Truncation (Cont’d)
To get a 80MHz/160MHz EDCA based TXOP, a STA does EDCA backoff procedure in the primary channel, and detects the other 20MHz channels being idle during PIFS interval before the TXOP.
RTS
A-MPDU
(VHT frame)
ch3
RTS
ch2
ch0+ch1+ch2+ch3
RTS
ch1
VHT-AP1
RTS
ch0
VHT-STA1
CTS
ch0
ch1
ch2
ch3
BLKACK
FC HT-STA3
Ch0+ch1+ch2+ch3
VHT-STA1
VHT-AP1
11a-AP2
FC HT-AP3
11a-STA2
ch0+ch1
ch0+ch1+ch2+ch3
ch3
11a–STA2
NAV
ch3
“ch0(primary channel)+ch1+ch2+ch3” is a 80MHz channel.
“ch0(primary channel)+ch1” is a 40MHz channel.
FC HT–STA3
NAV
ch0
ch3 is a 20MHz channel.

5. Negotiation of Used Channel Bandwidth (TBD)
Date: September 2010
Negotiation of Used Channel Bandwidth (TBD)
The TXOP holder and the TXOP responder notify the peer STA of the usage of channels for the following frame transmission through non-HT duplicate frame handshake. We call the two frames the non-HT duplicate initiating frame, the non-HT duplicate responding frame.
Another option method is that the TXOP responder gets the TXOP holder’s available channel through the non-HT duplicate transmission channels and then notify the available 20MHz operating channels to the TXOP holder, the TXOP holder decides the transmit channels in the following transmission.
The TXOP holder transmits CF-End frame to truncate the TXOP through the same channel set that it transmits the non-HT duplicate initiating frame. And the TXOP responder transmits CF-End frame to truncate the TXOP through the same channel set that it transmits the non-HT duplicate responding frame.
The TXOP responder may transmit the non-duplicate responding frame by the subset of the channels that the TXOP holder transmits the non-HT duplicate initiating frame for TXOP-protection.

6. Updated RTS/CTS method (TBD)
Date: September 2010
Updated RTS/CTS method (TBD)
A RTS includes the candidate subchannel set in the reserved bits of Service field or PHY padding.
The TXOP holder selects the candidate subchannel set from the idle 20MHz operating channels that it detects.
A legacy STA may just set its NAV timer when it receive the updated RTS frame.
A CTS includes final subchannel set in the reserved bits of Service field or PHY padding.
The final subchannel set must be the same as or subset of the candidate subchannel set. The final subchannel set must only include the idle 20MHz operating channels that the TXOP responder detects.
The final subchannel set is used for the following frame transmission in the TXOP.
If a VHT STA that receives updated RTS does not receive the following updated CTS, it will reset the NAV timer.
If a legacy STA does not receive the following CTS, it may not reset its NAV timer since it may not thinkthe NAV timer is not set by RTS frame.
If the TXOP holder does not receive the responding control frame, it transmits CF-End to reset the legacy STA’s NAV timer. This can guarantee the fairness.

7. New Control Frame Method (TBD)
Date: September 2010
New Control Frame Method (TBD)
A new control frame that uses non-HT duplicate format to initiate the TXOP includes candidate subchannel set by control frame body.
The TXOP holder selects the candidate subchannel set from the idle 20MHz operating channels that it detects.
A legacy STA will just set its NAV timer when it receive the new control frame.
A new control frame that uses non-HT duplicate format to respond the initiating frame which includes final subchannel set in frame body.
The TXOP responder does not transmit respond frame if its NAV timer is not 0 or all the channels in the candidate subchannel set are busy.
The final subchannel set must be the same as or subset of the candidate subchannel set. The final subchannel set must only include the idle 20MHz operating channels that the TXOP responder detects.
The final subchannel set is used for the following frame transmission in the TXOP.
If a VHT STA can not receive the non-HT duplicate responding frame, it will reset the NAV timer set by the non-HT duplicate initiating frame.
If a legacy STA does not receive the following non-HT duplicate responding frame, it may not reset its NAV timer since it may not thinkthe NAV timer is not set by RTS frame.
If the TXOP holder does not receive the responding control frame, it transmits CF-End to reset the legacy STA’s NAV timer. This can guarantee the fairness.

8. Channel Negotiation of DL-SDMA (TBD)
Date: September 2010
Channel Negotiation of DL-SDMA (TBD)
Multiple DL-SDMA destinations may have different available channels.
If the AP can get the available channel information from the DL-SDMA destination, it can avoid interference in the following transmission in the TXOP.
Possible methods:
Transmit multiple RTS/CTS pairs to DL-SDMA destinations before data frame transmission to get available channel information from multiple DL-SDMA destinations.
Define a new RTS control frame to allow multiple DL-SDMA destinations to report available channel information by responding CTS.

9. 80MHz/160MHz non-HT Duplicate Transmission
Date: September 2010
80MHz/160MHz non-HT Duplicate Transmission
80MHz/160MHz Non-HT duplicate transmission is used to transmit to a, n STAs that nay be present in a 20MHz/40MHz channel covered by 80MHz/160MHz channel.
The L-STF, L-LTF and L-SIG shall be transmitted in the same way as in the ac 80MHz/160MHz VHT transmission.
The VHT-SIG, VHT-STF, VHT-LTF are not transmitted.

10. Date: September 2010
Straw Poll 1
Do you support adding the following item into the specification framework document, 11-09/0992?
R5.X: 80MHz/160MHz duplicate mode shall be included in the specification to protect 80MHz/160MHz transmission.

11. Date: September 2010
Straw Poll 2
Do you support to add channel negotiation information in non-HT duplicate initiating frame and/or non-HT duplicate responding frame?

12. Date: September 2010
Straw Poll 3
Do you support to add candidate channel set in non-HT duplicate initiating frame and to add final channel set in non-HT duplicate responding frame?

13. Date: September 2010
Straw Poll 4
Do you support to add available channel set in non-HT duplicate responding frame?