1. doc.: IEEE 802.11-09/0562r0 Submission May 2009 L. Chu et alSlide 1 MCF Issues Date: 2009-05-10 Authors:

2. doc.: IEEE 802.11-09/0562r0 Submission May 2009 L. Chu et alSlide 2 MCCAOP MCF EDCA

3. doc.: IEEE 802.11-09/0562r0 Submission May 2009 L. Chu et alSlide 3 MCCAOP and EDCA TXOP A MCCAOP may includes multiple EDCA TXOPs. RAV makes the processing complicated. –A MCCA-capable mesh STA needs to maintain NAV and RAV. –RAV creates further unfairness among MCCA-capable mesh STAs and legacy mesh STAs. Duration MCCAOP TXOP Limit MCCA Owner CF-End Data NAV MCCA-Capable STA Data RAV Reset RAV? If yes, MCCA-capable STA may contend with MCCAOP Owner. If no, it is unfair compared with legacy STA. NAV Legacy STA Reset NAC Data

4. doc.: IEEE 802.11-09/0562r0 Submission May 2009 L. Chu et alSlide 4 EDCA TXOP, PSMP & HCCA PSMP allows a STA to transmit frames from multiple ACs in a TXOP which can save more power. –Why doesn’t MCCA allow a STA to transmit frames from multiple ACs in a MCCAOP to save more power? The AP can start PSMP TXOP through EDCAF or PIFS without backoff. The EDCA TXOP definition is accordingly changed to: –“Note that, as for an EDCA TXOP, a multiple frame transmission is granted to an EDCAF, not to a non-AP STA or AP, so that the multiple frame transmission is permitted only for the transmission of a frame of the same AC as the frame that was granted the EDCA TXOP, unless the EDCA TXOP obtained is used by an AP for a PSMP sequence, in which case, this AC transmission restriction does not apply to either the AP or the STAs participating in the PSMP sequence, but the specific restrictions on transmission during a PSMP sequence described in 9.16 (PSMP Operation) do apply”. In a reserved HCCA TXOP, it is up to the polled STA to decide which frames to transmit regardless the granted TXOP for a special TS. –Why does MCCA have the restriction that the reserved MCCAOP shall only transmit the frames for the indicated AC?

5. doc.: IEEE 802.11-09/0562r0 Submission May 2009 L. Chu et alSlide 5 Different DTIM Beacon Intervals In a mesh BSS, each mash STA can select different DTIM Beacon interval. –A MP can not reference its Neighbor MP’s MDAOP TXOP as a fixed offset with respect to its own MDAOP TXOP, because the MDAOP TXOP “slide” with respect to each other. TDBTT Subinterval TDIM Beacon Interval Offset TDBTT Subinterval TDIM Beacon Interval Offset TDBTT Subinterval Duration Subinterval TDIM Beacon Interval TDBTT TDIM Beacon Interval Subinterval

6. doc.: IEEE 802.11-09/0562r0 Submission May 2009 L. Chu et alSlide 6 Solutions: Reference DTIM Beacon Interval for MCCA Solution 1: all MCCA-capable mesh STAs use the default DTIM interval as its DTIM interval if they want to use MCCA. –Otherwise, MCCA is disabled in a MCCA-capable STA if the default DTIM interval is not used. –The DBTT is random selected to avoid beacon collision. Solution 2: all MCCA-capable mesh STAs use the default DTIM interval as the reference interval to select MCCAOP.

7. doc.: IEEE 802.11-09/0562r0 Submission May 2009 L. Chu et alSlide 7 Solutions: MCCAOP is Equal to EDCA TXOP RAV is not required. –A MCCA-capable mesh STA SHALL interpret the reception of a CF-End frame as a NAV reset. It is fair to legacy STAs and MCCA-capable STAs after receiving CF-End from MCCA Owner and MCCA Responder. The protocol becomes simple. Duration MCCAOP MCCA Owner CF-End Data NAV MCCA-Capable STA Data NAV Legacy STA Reset NAC

8. doc.: IEEE 802.11-09/0562r0 Submission May 2009 L. Chu et alSlide 8 Solutions: MCCAOP Access In a MCCAOP, it is up to the MCCAOP owner to decide which frames to transmit regardless the granted AC. This is similar to HCCA reserved SP and PSMP reserved SP. This can further save the power when MCCA is used for power saving.

9. doc.: IEEE 802.11-09/0562r0 Submission May 2009 L. Chu et alSlide 9 MCCA MCF EDCA

10. doc.: IEEE 802.11-09/0562r0 Submission May 2009 L. Chu et alSlide 10 TXOP Truncation A TXOP owner may transmit a CF-End frame to truncate the NAV when it empties its transmission queue. An AP may respond by transmitting a CF-End frame after SIFS. A non-AP STA that is not the TXOP holder shall not transmit a CF-End frame. –This is unfair to the neighbor mesh STAs of the TXOP receiver in a mesh BSS. A STA shall interpret the reception of a CF-End frame as a NAV reset. In a MBSS, if source mesh STA only transmits CF-End to truncate a TXOP, it is not fair to the neighboring mesh STAs of the destination STA. Solution: in subclause 9.9.1.7 add the following sentence “in a mesh BSS, a TXOP receiver may respond by transmitting a CF-End frame after SIFS. ”

11. doc.: IEEE 802.11-09/0562r0 Submission May 2009 L. Chu et alSlide 11 MCF EDCAF Backoff & Retransmission Mesh STA is added to EDCA backoff procedure and Retransmission procedure. But a mesh STA has the same rules of the backoff and retransmission as a QoS STA. –Since a mesh STA is a QoS STA, the mesh STA is not required to be mentioned in these places. Solution: delete subclause 9.9.15 and 9.9.1.6 from the draft.