1. Peer Traffic Indication enhancements
Month Year
doc.: IEEE yy/xxxxr0
July 2008
Peer Traffic Indication enhancements
Date:
Authors:
Jakub Majkowski (Nokia)
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
July 2008
Abstract
The presentation describes mechanisms to enhance the power save principles by using Peer Traffic Indication frame.
The enhancements introduce capability to detect ‘out-dated’ PTI frame and define a simple activation mechanism for the Direct Link.
Jakub Majkowski (Nokia)
John Doe, Some Company

3. Outdated PTI frame problem
Month Year
doc.: IEEE yy/xxxxr0
July 2008
Outdated PTI frame problem AP
STA1 Active mode
STA2 Power save mode
2. Service period 1. 3.
4. Service period
STA1 transmits a PTI frame through AP to peer STA2
STA2 triggers a service period with the STA1 before it gets the PTI indication from the AP. Service period between STA1 and STA2 is performed and terminated
The STA2 gets indication of buffered traffic in AP through the Beacon and fetches the buffered PTI frame
Because of the received “out-dated" PTI frame, the STA2 triggers a unnecessarily a service period with STA1, while the traffic is already transmitted in previous service period
This is likely scenario, because Beacon transmission periodicity is usually ~100ms and not all Beacons are necessarily received by the STA in power save mode
Jakub Majkowski (Nokia)
John Doe, Some Company

4. Solution, detection of the out-dated PTIs
Month Year
doc.: IEEE yy/xxxxr0
July 2008
Solution, detection of the out-dated PTIs
A PTI frame needs an information element which enables the receiver of the PTI frame to detect if the PTI frame is out-dated
Detection may be done by including a Sequence Number of the last transmitted frame in the Direct Link of the highest AC which backlogged field was set to non-zero value to PTI frame
If target STA detects that PTI frame is out-dated, it may ignore the frame
This eliminates unnecessary service periods and results in better power save
Jakub Majkowski (Nokia)
John Doe, Some Company

5. Two STAs supporting Peer U-ASPD
Month Year
doc.: IEEE yy/xxxxr0
July 2008
Two STAs supporting Peer U-ASPD AP
STA1 Active mode
STA2 Power save mode
Direct Link
Association
According to current draft even though two stations indicate support for Peer U-APSD only one peer STA at a time may operate in power save mode
The selection of the operation in power save mode is based on the competition:
Slower STA to signals operation in power save mode is forced to operate in active mode
This creates a race condition: battery powered STA wants only to operate in power save mode
If it temporarily changes itself to active mode, it may be forced to operate in active mode, i.e. its peer STA is able to signal the operation in power save mode
Jakub Majkowski (Nokia)
John Doe, Some Company

6. Peer U-ASPD, Peer STAs operating in power save mode
Month Year
doc.: IEEE yy/xxxxr0
July 2008
Peer U-ASPD, Peer STAs operating in power save mode
Both Peer STAs need to be allowed to operate in power save mode
To avoid unbalanced power consumption between STAs
To avoid race condition and optimal power management mode selection based on offered traffic
PTI frame may be used to setup a service period when both peer STAs operate in power save mode
Jakub Majkowski (Nokia)
John Doe, Some Company

7. Two different wakeup schedule negotiation procedures in Peer PSM
Month Year
doc.: IEEE yy/xxxxr0
July 2008
Two different wakeup schedule negotiation procedures in Peer PSM
In Peer PSM wakeup schedule negotiation between peer STAs is done in two ways:
Over the direct link (when starting Peer PSM operation)
Before negotiation both STAs in awake state on direct link, i.e. the direct link is used for frames transmission
Over the AP path (when activating the schedule)
Before negotiation both STAs in doze state on direct link, i.e. the direct link cannot be used for frames transmission
Jakub Majkowski (Nokia)
John Doe, Some Company

8. Unified wakeup schedule negotiation procedure
Month Year
doc.: IEEE yy/xxxxr0
July 2008
Unified wakeup schedule negotiation procedure
This mechanism assumes that both STAs are in awake state before starting schedule negotiation procedure.
When wakeup schedule is deactivated PTI frame transmission over the AP path can be used to assure that both STAs are in awake state.
After both STAs are in awake state wakeup schedule negotiation over the direct link can take place
Jakub Majkowski (Nokia)
John Doe, Some Company

9. Additional advantage of PTI frame
Month Year
doc.: IEEE yy/xxxxr0
July 2008
Additional advantage of PTI frame
If STA cannot buffered packets until the next wakeup period (e.g. due to missed wakeup periods) then it has to discard buffered packets
Solution
PTI frame is used to indicate that a STA has buffered frames for peer STA on direct link
The same usage as in Peer U-APSD could be advantages for STAs in Peer PSM
Allowing STA to trigger intermediate PSP with PTI frame could help to improve that situation
Jakub Majkowski (Nokia)
John Doe, Some Company

10. Month Year
doc.: IEEE yy/xxxxr0
July 2008
Strawpolls
Does the group support the proposed framework to address outdated PTI frames?
Yes No
Not sure
Does the group see the need to address Peer U-APSD use case where both the STA are in PS mode to ensure completeness of the Peer U-APSD mechanism?
Jakub Majkowski (Nokia)
John Doe, Some Company

11. Month Year
doc.: IEEE yy/xxxxr0
July 2008
Strawpolls
Does the group see the need for a wake up schedule negotiation procedure using PTI frame and PSM request/response exchange over the direct link path?
Yes No
Not sure
Does the group support using the PTI frame to have a fall back mechanism to address data loss or too high delays?
Jakub Majkowski (Nokia)
John Doe, Some Company