1. DLS Power Save Delivery Mechanism
November 2007
doc.: IEEE /2807r0
November 2007
DLS Power Save Delivery Mechanism
Date:
Authors:
Ali Raissinia, Qualcomm Inc.
Ali Raissinia, Qualcomm Inc.

2. November 2007
doc.: IEEE /2807r0
November 2007
Abstract
A mechanism to provide Power Save Delivery in DLS environment as both scheduled and unscheduled
Ali Raissinia, Qualcomm Inc.
Ali Raissinia, Qualcomm Inc.

3. November 2007
Baseline Standard
DLS (Direct Link Set-up) is a mechanism introduced in 11.e for direct data transfer between non-AP QOS STAs in a BSS
Improves traffic efficiency- throughput and delay
Frames not need to be routed through AP
Requires link set-up before data session can begin
Requires link tear-down after data session completed
DLS protocol prohibits STA to enter Beacon Power-Save
Assumption is that only AP is aware of STAs being sleep
Ali Raissinia, Qualcomm Inc.

4. DPSD Proposed Solution
November 2007
DPSD Proposed Solution
Modify standard to allow Beacon PS mode
No impact to normal operation- only DLS operation is compromised
Come up with a scheme where peer STAs can share wake-up time(s) for data transfer
Normal Beacon PS mode still allows data transfer between AP and STA
Use of TIM bits as notification for presence of unicast and broadcast/multicast frames
Use some form of “TSPEC” negotiation between two STAs to setup scheduled wake-up times or unscheduled
“TSPEC” can be used to set unidirectional or bidirectional data transfer
Key parameters for Scheduled DPSD are OFFSET and SERVICE INTERVAL (see diagram in the next page)
Ali Raissinia, Qualcomm Inc.

5. Scheduled DPSD Details
November 2007
Scheduled DPSD Details
Scheduled DPSD suited for VOIP data, i.e. 20/30ms
Use More Data bit to convey presence of additional buffered frames & EOSP bit to indicate “ready” to enter sleep
In uni-directional case, ESOP bit conveys STA entering sleep after receiving ACK frame (if required)
When no ACK received retransmit frame with ESOP bit once more and then enter sleep
In a Bi-directional case, STA enters sleep only after it coveys that it’s ready to sleep (setting its own ESOP bit) and also receives ESOP bit from the peer STA
Ali Raissinia, Qualcomm Inc.

6. Unscheduled DPSD Details
November 2007
Unscheduled DPSD Details
For unscheduled DPSD one of the STAs stays always awake
STA that enters sleep can wakeup and follow similar procedure used in unscheduled APSD, i.e. send trigger frame to “always awake DLS STA”
Upon trigger frame the “always awake DLS STA” sends MSDUs that are assigned to be delivery-enabled, limited by a new field “MAX DLS SP length field”
Rule for more data bit indicating additional frame buffered by “always awake DLS STA” should follow the unscheduled APSD
Ali Raissinia, Qualcomm Inc.

7. November 2007
Conclusions
DLS Power Save Delivery mechanism provides ability for STA to benefit from power save mechanism while performing DLS transmissions for QoS sensitive traffics, i.e. required minimum latency/jitter
Ali Raissinia, Qualcomm Inc.