1. 802.11e EDCA-APSD TXOP Handoff September 2003
doc.: IEEE /xxx
September 2003
802.11e EDCA-APSD TXOP Handoff September 2003
Matthew Fischer, Broadcom
Matthew Fischer, Broadcom

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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