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MCF Issues

MCF Issues. Date: 2009-05-10. Authors:. MCCAOP MCF EDCA. 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.

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MCF Issues

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  1. MCF Issues Date: 2009-05-10 Authors: L. Chu et al

  2. MCCAOP MCF EDCA L. Chu et al

  3. 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. MCCAOP and EDCA TXOP CF-End Data Data TXOP Limit MCCA Owner Duration MCCAOP Data Reset RAV? If yes, MCCA-capable STA may contend with MCCAOP Owner. If no, it is unfair compared with legacy STA. RAV MCCA-Capable STA NAV Reset NAC NAV Legacy STA L. Chu et al

  4. 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? EDCA TXOP, PSMP & HCCA L. Chu et al

  5. 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. Different DTIM Beacon Intervals Duration Offset Subinterval Subinterval Subinterval TDIM Beacon Interval TDBTT TDIM Beacon Interval TDBTT TDIM Beacon Interval TDBTT TDBTT Duration Offset Subinterval Subinterval TDIM Beacon Interval TDIM Beacon Interval TDBTT TDBTT TDBTT L. Chu et al

  6. 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. Solutions: Reference DTIM Beacon Interval for MCCA L. Chu et al

  7. 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. Solutions: MCCAOP is Equal to EDCA TXOP Data CF-End MCCA Owner Duration MCCAOP Data NAV MCCA-Capable STA Reset NAC NAV Legacy STA L. Chu et al

  8. 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. Solutions: MCCAOP Access L. Chu et al

  9. MCCA MCF EDCA L. Chu et al

  10. 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. ” TXOP Truncation L. Chu et al

  11. 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. MCF EDCAF Backoff & Retransmission L. Chu et al

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