Implications of Large-size RU Aggregation on RTS/CTS in IEEE 802.11-17

Addressing implications of large-size RU aggregation on RTS/CTS in IEEE 802.11-17, focusing on the signaling of Enhanced High Throughput Format PPDU Bandwidth and puncturing in RTS/CTS frames. Proposing the use of HE MU-RTS Trigger frame to elicit CTS response from STAs, along with different CTS formats based on the number of responding STAs. Exploring CCA rules for MU-RTS/(eht)CTS. Discussing punctured RTS transmission rules and options regarding CTS transmission logic.

• IEEE 802.11-17
• RTS/CTS frames
• RU aggregation
• Enhanced High Throughput
• CTS formats

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1. April 2020 doc.: IEEE 802.11-17/xxxxr0 RTS/CTS frames in 11be Date: 2020-03-20 Authors: Name Lochan Verma Affiliations Apple Address Phone email lochan_verma@apple.com Yong Liu Jarkko Kneckt Qi Wang Tianyu Wu Jinjing Jiang SK Yong Submission Slide 1 Lochan Verma, et al., Apple

2. April 2020 doc.: IEEE 802.11-17/xxxxr0 Abstract Large-size RU Aggregation rules have implications on RTS / CTS Also, signaling EHT PPDU BW and puncture in RTS / CTS needs attention New PPDU Bandwidth(BW) : 320, 160+160, 240, 160+80 MHz We propose Using only the HE MU-RTS Trigger frame to elicit CTS from one or more STAs CTS uses Legacy CTS format when MU-RTS elicits CTS response from >1 STA CTS uses new ehtCTS format when MU-RTS elicits CTS response from one STA CCA rules for MU-RTS / (eht)CTS Submission Slide 2 Lochan Verma, et al., Apple

3. April 2020 doc.: IEEE 802.11-17/xxxxr0 Large-size RU Aggregation Rules Implications on RTS / CTS Limited large-size RU ( ??? ?????) aggregation modes for a STA in an OFDMA transmission and in a non-OFDMA transmission defined in 11be For e.g., in an 80MHz OFDMA and non-OFDMA transmission a single puncture of 20MHz sub channel is allowed Should RTS / CTS be transmitted on all eligible 20MHz sub channels within the PPDU BW or only on those 20MHz sub channels that yield a valid large-size RU aggregation mode? Next, we answer this question by providing Punctured RTS / CTS transmission rules Submission Slide 3 Lochan Verma, et al., Apple

4. Mar 2020 doc.: IEEE 802.11-17/xxxxr0 Punctured RTS Transmission Rules Option 1 (Preferred) RTS transmitted only on 20MHz sub channels that have CCA Idle and that yield a valid large-size RU aggregation mode Avoids unnecessary medium reservation Option 2 RTS transmitted on all 20MHz sub channels that have CCA Idle May result in unnecessary medium reservation May accommodate cases such as CTS is returned on 80/160MHz BW, wherein 20MHz puncturing is allowed Options illustrated through an example of 320MHz PPDU Min. puncture of 40MHz in 320MHz PPDU [2] Lochan Verma, et al., Apple Submission Slide 4

5. Mar 2020 doc.: IEEE 802.11-17/xxxxr0 Punctured CTS Transmission Rules Option 1 (Preferred) CTS transmitted on all 20MHz sub channels on which RTS was received and that have CCA Idle Simplicity of CTS transmission logic Option 2 CTS transmitted only on 20 MHz sub channels on which RTS was received and that have CCA Idle and that yield a valid large-size RU aggregation mode Next, BW and Puncture signaling in RTS/CTS Options illustrated through an example of 320MHz PPDU Min. puncture of 40MHz in 320MHz PPDU [2] Lochan Verma, et al., Apple Submission Slide 5

6. April 2020 doc.: IEEE 802.11-17/xxxxr0 EHT PPDU BW and Puncture Indication in RTS / CTS Possible approaches include 1. Extending BW Signaling TA method Cons: feasibility issue due to lack of bits available for repurposing 2. Define new EHT RTS / new EHT CTS frame format [1] Cons: HE devices cannot reset NAV set by an EHT RTS 3. Reuse HE MU-RTS Trigger frame Pros: HE devices can reset NAV set by a MU-RTS, i.e., MU-RTS + no CTS + no Data => clear NAV Next is detailed description of 3 Submission Slide 6 Lochan Verma, et al., Apple

7. April 2020 doc.: IEEE 802.11-17/xxxxr0 BW & Puncture Indication in HE MU-RTS by EHT STA MU-RTS can carry a special User Info field indicating BW: 320, 160+160, 240, 160+80 MHz Puncture Pattern; E.g., bitmap; 1-bit maps to each of the 20MHz sub channel in 320MHz A reserved AID value identifies this special User Info field UL BW in Common Info field indicates BW of PPDU carrying MU-RTS Set to 20, 40, 80, 160/80+80, if MU-RTS PPDU BW 160MHz Set to 160/80+80, if MU-RTS PPDU BW > 160MHz MU-RTS carried in a non-HT or a non-HT DUP PPDU Next, CTS response rules Submission Slide 7 Lochan Verma, et al., Apple

8. April 2020 doc.: IEEE 802.11-17/xxxxr0 CTS Frame Response to MU-RTS Trigger Frame CTS uses Legacy CTS frame format when MU-RTS indicates that this MU- RTS is eliciting response from more than one STA CTS sdon t indicate reserved BW because CTS s transmitted by STAs must be identical CTS uses a new ehtCTS frame format when MU-RTS indicates that this MU-RTS is eliciting response from one STA ehtCTS indicates reserved BW allowing any STA to determine reserved BW by receiving ehtCTS on at least primary 20MHz channel (eht)CTS carried in non-HT or non-HT DUP PPDU One bit in the Common Info field on the MU-RTS indicates to the STA, which CTS frame format to use in response to the MU-RTS E.g., repurpose a bit from UL HE-SIG-A2 Reserved Next, ehtCTS frame format Slide 8 Submission Lochan Verma, et al., Apple

9. April 2020 doc.: IEEE 802.11-17/xxxxr0 An example of ehtCTS Frame Format ehtCTS frame format builds upon legacy CTS chBitmap indicates 20MHz sub channel on which ehtCTS is transmitted the Next, AID value setting in MU-RTS Lochan Verma, et al., Apple Submission Slide 9

10. April 2020 doc.: IEEE 802.11-17/xxxxr0 AID Setting in User Info field of MU-RTS Trigger Frame MU-RTS Trigger frame transmission by an 11be AP and non-AP STA In MU-RTS transmitted by an AP the AID value is set to the AID of the non-AP STA that is being triggered for CTS response In MU-RTS transmitted by a non-AP STA the AID value is set to the AID of the non-AP STA that is transmitting the MU-RTS Or, AID value set to 0 (reserved) or some other pre-defined value Next CCA rules for (eht)CTS Submission Slide 10 Lochan Verma, et al., Apple

11. April 2020 doc.: IEEE 802.11-17/xxxxr0 CCA Rules for (eht)CTS frame response to MU-RTS Carry over HE CCA Rules for CTS frame response to MU-RTS to EHT Combination of virtual Carrier Sense (CS) and ED-based CCA during SIFS after MU-RTS Trigger frame used to determine medium state on non punctured 20MHz sub channels Only non-primary channels are punctured If MU-RTS is eliciting response from more than one STA CTS transmitted by a STA only when all the 20MHz sub channels contained in the allocated RU that are CCA Idle (Option 1 from Slide-5) If MU-RTS is eliciting response from one STA ehtCTS transmitted by a STA on the primary 20MHz channel and on any other 20MHz sub channels contained in the allocated RU that are CCA Idle (Option 1 from Slide-5) Submission Slide 11 Lochan Verma, et al., Apple

12. April 2020 doc.: IEEE 802.11-17/xxxxr0 An example MU-RTS and CTS frame exchange MU-RTS 160MHz carried in non-HT DUP PPDU MU-RTS requests non-AP STA1 to transmit CTS response in non- HT PPDU on P80 and non-AP STA2 to transmit CTS response in non-HT DUP PPDU on 160MHz No transmission in puncture zones is transmitted on Lochan Verma, et al., Apple Submission Slide 12

13. April 2020 doc.: IEEE 802.11-17/xxxxr0 Summary We describe punctured RTS / CTS transmission rules as a result of limited large-size RU aggregation modes in 11be We propose using only the HE MU-RTS Trigger frame to elicit CTS from one or more STAs Preserves the property that HE devices can reset NAV set by a MU-RTS MU-RTS signals if it is eliciting CTS response from 1 or more than 1 STA CTS uses Legacy CTS format when MU-RTS elicits CTS response from > 1 STA CTS uses new ehtCTS format when MU-RTS elicits CTS response from one STA CCA rules for MU-RTS / (eht)CTS Submission Slide 13 Lochan Verma, et al., Apple

14. April 2020 doc.: IEEE 802.11-17/xxxxr0 References [1] 11-19-2125-00-00be-EHT-RTS-and-CTS-procedure [2] 11-19-1262-08-00be-specification-framework-for-tgbe Submission Slide 14 Lochan Verma, et al., Apple

15. April 2020 doc.: IEEE 802.11-17/xxxxr0 Backup Submission Slide 15 Lochan Verma, et al., Apple

16. April 2020 doc.: IEEE 802.11-17/xxxxr0 NAV Reset Rule for (MU)RTS/CTS [802.11ax D6.0, P/L:319/43] Submission Slide 16 Lochan Verma, et al., Apple

17. April 2020 doc.: IEEE 802.11-17/xxxxr0 NAV Reset Rule RTS/CTS [802.11 REVmd3.1, P/L:1734/45] Submission Slide 17 Lochan Verma, et al., Apple