1. Peer Power Save Mode Date: 2008-01-15 Authors: January 2008
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Alexander Safonov, IITP RAS

2. PSM in the current 802.11z-D0.01 document (1/2)
January 2008
PSM in the current z-D0.01 document (1/2)
TDLS Rx Path Switch Request/Response 1
Encapsulated DATA frame (TDLS Rx Path Switch Request)
Path Element (AP Path Switch) AP AP AP
Encapsulated DATA frame (TDLS Rx Path Switch Response)
Path Element (AP Path Switch) 2
QSTA1 changes to Power Saving Mode 3
QSTA2
QSTA2
QSTA1
QSTA1
QSTA1
Alexander Safonov, IITP RAS

3. PSM in the current 802.11z-D0.01 document (2/2)
January 2008
PSM in the current z-D0.01 document (2/2)
Data is sent on the AP path, but not on the direct one AP 3
TIM element
DATA frame 1
PS-poll 4
DATA frame 5
QSTA2
QSTA1 2
QSTA1 awakes
Alexander Safonov, IITP RAS

4. Motivation When a peer is in PSM, the direct link is not used
January 2008
Motivation
When a peer is in PSM, the direct link is not used
The AP path is used, thus two successful transmissions of a long data packet are needed to deliver the packet from peer to peer
No QoS differentiation because of legacy AP
Is there another way of operation in PSM?
Alexander Safonov, IITP RAS

5. Peer Power Save Mode Peers enter PSM remaining on the direct path
January 2008
Peer Power Save Mode
Peers enter PSM remaining on the direct path
Data is buffered at the originator QSTA, but not at the legacy AP
QoS differentiation
Peers use the concept of Service Period (SP) to deliver data directly but not over the AP
Using full potential of the direct path
Peers may use TLDS TIM sent over the AP path to inform the peer about buffered data
Alexander Safonov, IITP RAS

6. Atlanta history (07/2761r4) 07/2769r2: two concepts were proposed
January 2008
Atlanta history (07/2761r4)
07/2769r2: two concepts were proposed
SP is unscheduled
Only one of two peers may enter PSM simultaneously
SP is scheduled
Both peers may enter PSM at the same time
Straw polls:
Are you in favor to consider Unscheduled PSM (as per doc. 2760r1)?
Yes: 24; No: 0; I don’t know: 1
Are you in favor to consider Scheduled PSM (as per doc. 2760r1)?
Yes: 11; No: 6; I don’t know: 6
Alexander Safonov, IITP RAS

7. January 2008
Power Save Mode in TDLS
TDLS STA has two options when it is going to enter PSM
Switch to the AP path with its peer
Enter Peer PSM (PPSM) informing the peer while remaining at the direct path
Alexander Safonov, IITP RAS

8. January 2008
Peer PSM (1/3)
To enter PPSM, a TDLS STA sends to its peer a frame with Power Management field set to 1
When a STA is in PPSM, its peer STA shall stay in active mode and buffer frames for the STA in PPSM
The STA in PPSM may wake up at some arbitrary time and initiate an unscheduled SP by sending a trigger frame to the peer
The STA in PPSM remains in awake state until it receives a frame, with the EOSP bit set to 1
Alexander Safonov, IITP RAS

9. January 2008
Peer PSM (2/3)
The peer STA in active mode may assemble the partial virtual bitmap containing the buffer status for STAs in the PPSM and send it out in the TIM field of TDLS TIM broadcast frame
If STA in TDLS PPSM receives TDLS TIM frame, it must initiate the unscheduled SP
The transmission interval of TDLS TIM frame is out of scope
Alexander Safonov, IITP RAS

10. Peer PSM(3/3) Power Management bit controls the state in PPSM
January 2008
Peer PSM(3/3)
Power Management bit controls the state in PPSM
Unscheduled SP is triggered to retrieve buffered data from peer
If QSTA2 wishes to inform QSTA1 about buffered data it may send a TDLS TIM frame AP
Encapsulated DATA frame (TDLS TIM)
QSTA1 changes to Power Saving Mode
QSTA1 changes to Power Saving Mode 4
Null DATA frame (Power Management Field is set to 0) 6 2
QSTA2
QSTA1 5
Buffered DATA frame (EOSP is set to 1)
QSTA1 wakes up 3
A frame with Power Management bit set to 1 1
Alexander Safonov, IITP RAS

11. January 2008
Motion
Move to include the normative text in document z-normative-text-peer-power-save-mode.doc into the TGz current draft
Mover:
Seconder:
Result:
Alexander Safonov, IITP RAS