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DLS Power Save Delivery Mechanism

DLS Power Save Delivery Mechanism. Authors:. Date: 2007-11-12. Abstract. A mechanism to provide Power Save Delivery in DLS environment as both scheduled and unscheduled. 802.11 Baseline Standard.

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DLS Power Save Delivery Mechanism

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  1. DLS Power Save Delivery Mechanism Authors: Date: 2007-11-12 Ali Raissinia, Qualcomm Inc.

  2. Abstract A mechanism to provide Power Save Delivery in DLS environment as both scheduled and unscheduled Ali Raissinia, Qualcomm Inc.

  3. 802.11 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 • 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 ScheduledDPSD are OFFSET and SERVICE INTERVAL (see diagram in the next page) Ali Raissinia, Qualcomm Inc.

  5. Scheduled DPSD Details • Scheduled DPSD suited for VOIP data, i.e. wakeup @every 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 • 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. 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.

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