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802.11e EDCA-APSD TXOP Handoff September 2003

802.11e EDCA-APSD TXOP Handoff September 2003. Efficiency of APSD in EDCA. Proposed EDCA APSD mechanism Allows QSTA-directed wake times Matches SP with QSTA application’s wake timing Without the overhead of complex scheduler in the QAP (maintains the simpler approach of EDCA)

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802.11e EDCA-APSD TXOP Handoff September 2003

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  1. 802.11e EDCA-APSD TXOP Handoff September 2003 Matthew Fischer, Broadcom

  2. Efficiency of APSD in EDCA • Proposed EDCA APSD mechanism • Allows QSTA-directed wake times • Matches SP with QSTA application’s wake timing • Without the overhead of complex scheduler in the QAP (maintains the simpler approach of EDCA) • Provides for adequate power save operation within EDCA • Still room for additional power savings • Not too much different from simply sending a legacy PS-Poll frame Matthew Fischer, Broadcom

  3. Allow TXOP Handoff • Allow the QSTA to hand the TXOP to the QAP when it is done with uplink transmissions • Further reduces wake time • Allows immediate downlink delivery, rather than delayed delivery • QSTA does not have to stay awake during EDCA CSMA/CA protocol resolution time which is required in the current proposal for the QAP to access the network for downlink delivery • New proposed behavior is optional, not required • See TXOP limit addition • Simple to implement Matthew Fischer, Broadcom

  4. Mechanism for Handoff • TXOP can be passed by allowing that: • QAP may respond to uplink QOS-Data (or QOS-Null) with MORE=0 with either QOS-Data+CF-ACK or QOS-Null+CF-ACK • As an alternative to ACK • Thereby taking over the TXOP • Restrict QAP behavior to those cases where uplink flow is from a QSTA with a registered EDCA APSD • Include option to allow QSTA to fill Duration of last frame of the TXOP with value to cover the expected mean-size data frame for the downlink flow plus SIFS+ACK • I.e. NAV the handoff frames • Alternative: cover a NULL frame plus SIFS+ACK Matthew Fischer, Broadcom

  5. Example 1 SIFS • QSTA captures network using EDCA rules • QAP uses the more bit to determine handoff point • Responds with normal ACK until handoff QSTA Q-Data (More=1) Q-Data (More=0) ACK ACK QAP ACK Q-Data+CF-ACK Q-Data QAP takes control here Matthew Fischer, Broadcom

  6. Example 2 SIFS • TXOP handoff only allowed if QSTA has signaled EDCA-APSD QSTA Q-Data (More=0) ACK ACK ACK QAP Q-Null+CF-ACK Q-Data Q-Data Control is passed, but QAP downlink traffic is not yet ready Matthew Fischer, Broadcom

  7. TXOP limits • Addition to the TXOP limit rules • EDCA APSD TXOP limit = ½ of normal TXOP limit • Both QSTA and QAP have this new limit for the EDCA-APSD case only • “Shared TXOP” will never exceed normal TXOP limit Matthew Fischer, Broadcom

  8. Allowance for No-ACK • Allow handoff with QoS-Data (I.e. without +CF-ACK) • Only for cases when No ACK is expected for the frame with handoff signaling (I.e. MORE=0 and registered EDCA APSD flow) Matthew Fischer, Broadcom

  9. Summary • Allow QSTA-initiated TXOP to be handed off • QSTA starts the TXOP with uplink frame • QOS-NULL is allowed as initial frame • QSTA and QAP “share” the TXOP • Minimizes wake time for sleeping QSTA • Optionally performed at the QAP, allowing flexibility in implementations • May use proposed delayed downlink delivery instead • Minimal change to EDCA APSD QSTA requirements • Must be capable of receiving +CF-ACK • Modified TXOP limit for EDCA-APSD case only Matthew Fischer, Broadcom

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