802.11e EDCA-APSD TXOP Handoff September 2003 doc.: IEEE 802.11-98/xxx September 2003 802.11e EDCA-APSD TXOP Handoff September 2003 Matthew Fischer, Broadcom Matthew Fischer, Broadcom

Efficiency of APSD in EDCA 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) 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

September 2003 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

Mechanism for Handoff TXOP can be passed by allowing that: September 2003 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

Example 1 QSTA captures network using EDCA rules September 2003 Example 1 SIFS QSTA Q-Data (More=1) Q-Data (More=0) ACK ACK QAP ACK Q-Data+CF-ACK Q-Data QAP takes control here QSTA captures network using EDCA rules QAP uses the more bit to determine handoff point Responds with normal ACK until handoff Matthew Fischer, Broadcom

Example 2 TXOP handoff only allowed if QSTA has signaled EDCA-APSD September 2003 Example 2 SIFS 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 TXOP handoff only allowed if QSTA has signaled EDCA-APSD Matthew Fischer, Broadcom

TXOP limits Addition to the TXOP limit rules September 2003 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

September 2003 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

Summary Allow QSTA-initiated TXOP to be handed off September 2003 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