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Peer Power Save Mode for TDLS

Peer Power Save Mode for TDLS. Authors:. Date: 2008-05-12. In some usage scenarios, both peer STAs may want to go into PS mode over a direct link.

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Peer Power Save Mode for TDLS

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  1. Peer Power Save Mode for TDLS Authors: Date: 2008-05-12 Michelle Gong (Intel Corp) et al.

  2. In some usage scenarios, both peer STAs may want to go into PS mode over a direct link • For instance, when a laptop is communicating with a handheld device over a direct link, both want to save power while still maintaining the direct link • The existing asymmetric peer PSM mechanism as defined in 11z D1.0 does not address this usage scenario Michelle Gong (Intel Corp) et al.

  3. The scheduled peer PSM is complementary to the unscheduled peer PSM defined in 11z D1.0 • When one peer STA supports PSM client mode and the other STA supports PSM AP mode, they can utilize asymmetric peer PSM • Because different STAs may support either AP mode or client mode, some of the following cases are not addressed in D1.0 • Both peer STAs support PSM AP mode: • Both always stay awake and never go into power save mode over the direct link (No PSM is needed) • They negotiate as to which one can go into power save mode and which one has to stay active (Asymmetric peer PSM combined with a negotiation procedure) • Both want to go into power save mode (Symmetric peer PSM is needed) • Both peer STAs support PSM client mode: • Neither one wants to go into power save mode over the direct link (No PSM is needed) • At least one wants to go into power save mode (Symmetric peer PSM is needed) • The goal is to have a joint Unscheduled Power Save Mode (UPSM) and Scheduled Power Save Mode (SPSM) proposal that can cover a broad range of usage scenarios Michelle Gong (Intel Corp) et al.

  4. 5 Buffered DATA frame (EOSP is set to 1) 4 4 QSTA1 wakes up at scheduled time QSTA2 wakes up at scheduled time 2 EncapsulatedDATA frame(TDLS PSM Switch Response) To support the combined PSM mode, two peer STAs exchange Request/Response frames AP QSTA2 changes to Power Save Mode QSTA1 changes to Power Save Mode 3 3 QSTA2 QSTA1 EncapsulatedDATA frame(TDLS PSM Switch Request) 1 Michelle Gong (Intel Corp) et al.

  5. Peer STAs exchange TDLS PSM Request and Response frames over the direct link • Frame format of the TDLS PSM Request frame Michelle Gong (Intel Corp) et al.

  6. Frame format of the TDLS PSM Response frame Michelle Gong (Intel Corp) et al.

  7. Format of the Result IE Note: Upon receiving “Accept with my own schedule”, the initiator may send out a second request frame that contains the wakeup schedule defined in the first TDLS PSM Response frame Michelle Gong (Intel Corp) et al.

  8. An example Wakeup Schedule IE has the following fields • Sleep State: 0: Always awake 1:No scheduled wakeup period 2: Wakeup schedule as specified in this IE • Offset, Periodicity, Beacon Interval (BI) and Fraction has the following relationship • An example formula: TSF mod floor(BI * Periodicity/Fraction) = offset • Offset field indicates the timing offset from the TSF Start Time • The value of the offset can be randomly selected to avoid overlapping wakeup schedules for different direct links • Overlapping with beacons and MCBC is not recommended • Periodicity is introduced to facilitate a longer sleep interval than a beacon interval or a DTIM interval • Fraction is introduced for flexibility and shorter sleep intervals • Example: BI=100 TUs, Periodicity = 60, Fraction=16, offset=15 TUs • Awake at 15, 390, 765, 1140, … Michelle Gong (Intel Corp) et al.

  9. Minimum Duration and Maximum Duration of the wakeup period are also important parameters • Both peer STAs wake up at or before the scheduled wakeup period and stay awake for Minimum Duration after the beginning of the wakeup period • The peer STAs may go back to doze state when data exchanges complete successfully before the Minimum Duration time • Both STAs remain awake until all data exchanges complete successfully or for Maximum Duration after the beginning of the wakeup period • The Maximum Duration is useful for off-channel operation where one or both peer STAs need to go back to the main channel at a certain time, for instance to receive DTIM beacons or buffered traffic Michelle Gong (Intel Corp) et al.

  10. Each peer STA may initiate one or more service periods within one wakeup period The shortest data exchange in a wakeup period: A data (EOSP=1)/ SIFS / ACK/A data (EOSP=1)/ SIFS / ACK 11n reverse direction grant can be utilized to exchange data in both directions in a single channel access Michelle Gong (Intel Corp) et al.

  11. Data exchanges between two STAs in PS occur during the wakeup period • If STA A has buffered traffic for STA B, STA A can directly send buffered data frames to STA B within the minimum duration • STA A sets the EOSP bit of all its data frames to 0, until it has no more frames buffered for STA B. STA A sets the EOSP bit in the last data frame to 1 to indicate that it has no buffered traffic for STA B • If STA A has frames buffered for STA B but max duration has elapsed since the beginning of the wakeup period, STA A sets the EOSP bit to 1 in the first data frame sent after the time expires. STA A should not send additional data frames to STA B until the next wakeup period • STA B can transmit its frames to STA A while it’s receiving STA A’s packets, which means two service periods that are started by STA A and STA B respectively can overlap. Note that multiple buffered packets may be delivered during this period. • Both STA A and STA B shall remain awake until all buffered frames have been delivered to them or the max duration timer expires • After both STAs indicate the completion of data transmission by setting the EOSP bit to 1 in data frames, both STAs go back to doze state Michelle Gong (Intel Corp) et al.

  12. In summary, the combined peer PSM is more flexible and addresses a broader range of use cases • UPSM and SPSM allow one or both STAs to go into power save mode while still maintaining the peer link • The procedure is as follows: • Two STAs negotiate the peer power save mode that they would be in and a wakeup schedule • STAs wakeup at or before the start of the wakeup period and start data packet exchange • Either STA can initiate a peer service period • The owner of the peer service period terminates the period • We will update the normative text in 11-08-0541r0 Michelle Gong (Intel Corp) et al.

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