Peer Power Save Mode for TDLS Month Year doc.: IEEE 802.11-yy/xxxxr0 July 2008 Peer Power Save Mode for TDLS Date: 2008-07-15 Authors: Michelle Gong (Intel Corp) et al. John Doe, Some Company

July 2008 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.

Month Year doc.: IEEE 802.11-yy/xxxxr0 July 2008 To support the peer PSM mode, two peer STAs exchange Request and Response frames AP QSTA1 changes to Power Save Mode QSTA2 changes to Power Save Mode 5 Buffered DATA frame (EOSP is set to 1) 3 3 QSTA2 QSTA1 QSTA1 wakes up at scheduled time 4 QSTA2 wakes up at scheduled time 4 2 Encapsulated DATA frame (TDLS PSM Switch Response) Encapsulated DATA frame (TDLS PSM Switch Request) 1 Michelle Gong (Intel Corp) et al. John Doe, Some Company

Format of the TDLS PSM Request frame Month Year doc.: IEEE 802.11-yy/xxxxr0 July 2008 Format of the TDLS PSM Request frame Order Information Notes 1 Dialog Token The Dialog Token is set to a non-zero value that is unique among TDLS Peer PSM Request frames for which a corresponding TDLS Switch Response frame has not been received. 2 Link Identifier The link identifier is specified in section 7.3.2.z1 3 Wakeup Schedule IE The Wakeup Schedule IE describes a schedule for the wakeup time 4 Vendor Specific One or more vendor-specific information elements may be in this frame. Michelle Gong (Intel Corp) et al. John Doe, Some Company

Format of the TDLS PSM Response frame Month Year doc.: IEEE 802.11-yy/xxxxr0 July 2008 Format of the TDLS PSM Response frame Order Information Notes 1 Dialog Token The Dialog Token is set to the non-zero value contained in the TDLS Peer PSM Request frames to identify the request/response transaction 2 Status Code The Status code identifies the result of the response as defined in Table 7-23. 3 Link Identifier The link identifier is specified in section 7.3.2.z1 4 Wakeup Schedule IE The Wakeup Schedule IE describes a schedule for the wakeup time 5 Vendor Specific One or more vendor-specific information elements may be in this frame. Michelle Gong (Intel Corp) et al. John Doe, Some Company

A STA may reject a wakeup schedule for various reasons July 2008 A STA may reject a wakeup schedule for various reasons Status code Meaning <ANA> Wakeup schedule rejected but alternative schedule provided Wakeup schedule rejected because not going into power save Wakeup schedule rejected for unspecified reason Michelle Gong (Intel Corp) et al.

The Wakeup Schedule IE has the following fields Month Year doc.: IEEE 802.11-yy/xxxxr0 July 2008 The Wakeup Schedule IE has the following fields   Element ID Length Start Time Interval Min Duration Idle Count Octets 1 8 4 2 The Start Time field is 8 octets and indicates the anticipated time, expressed in microseconds, when both STAs need to wakeup It represents the TSF timer value at the start of the first wakeup period (WP) StartTime can be set to a beacon TBTT plus an offset The Interval field indicates the time, expressed in microseconds, between two successive wakeup periods The Idle Count field indicates how many consecutively empty wakeup periods a peer STA would allow before it suspends the direct link Michelle Gong (Intel Corp) et al. John Doe, Some Company

July 2008 Minimum Duration is introduced so that two STAs have time to access the channel 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 A bi-directional peer service period begins after an acknowledged frame exchange A STA shall remain awake until it receives an MPDU with EOSP bit set to 1 The peer service period is terminated when both peer STAs transmitted an MPDU with the EOSP bit set The peer STAs may go back to doze state when data exchanges complete successfully before the Minimum Duration time Minimum duration Interval Michelle Gong (Intel Corp) et al.

Peer STAs wake up at or before the start of a wakeup period Month Year doc.: IEEE 802.11-yy/xxxxr0 July 2008 Peer STAs wake up at or before the start of a wakeup period STA B STA A TDLS PSM Switch Request TDLS PSM Switch Response Minimum wakeup period Buffered DATA (EOSP=0) Buffered DATA (EOSP=1) Buffered DATA (EOSP=0) Buffered DATA (EOSP=1) A peer service period begins after an acknowledged frame exchange between the peer STAs The scenario when the “More data” bit in ACK is supported is in the backup slides Michelle Gong (Intel Corp) et al. John Doe, Some Company

Month Year doc.: IEEE 802.11-yy/xxxxr0 July 2008 A service period between two STAs in PS mode may be initiated within the minimum wakeup duration 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 does not intend to transmit more frames to STA B. STA A sets the EOSP bit in the last data frame to 1 STA B can transmit its frames to STA A while it’s receiving STA A’s packets After a service period is initiated, both STA A and STA B shall remain awake until one of the following conditions are met If “More Data” bit in ACK is supported: Peer STAs may go back to doze state after one acknowledged frame exchange with the EOSP bit in an MPDU set to 1 and the More Data bit in the ACK frame set to 0 If “More Data” bit in ACK is not supported: Peer STAs may go back to doze state after one acknowledged frame exchange in each direction with the EOSP bit in the MPDU set to 1 Michelle Gong (Intel Corp) et al. John Doe, Some Company

July 2008 In summary, this peer PSM scheme is flexible and addresses a broader range of use cases The peer PSM allows one or both STAs to go into power save mode while still maintaining the peer link The procedure is as follows: Two STAs negotiate a wakeup schedule STAs wakeup at or before the start of a wakeup period and start data packet exchange A peer service period is initiated by an acknowledged frame exchange between the peer STAs The peer service period is terminated 1) when both peer STAs transmitted an MPDU with the EOSP bit set to 1 or 2) through one acknowledged frame exchange with the EOSP bit in the MPDU set to 1 and “More data” bit in the ACK set to 0 Peer STAs may stay in doze state after “Idle Count” number of consecutive empty wakeup periods Detailed information can be found in 11-08/0668r8 Michelle Gong (Intel Corp) et al.

July 2008 Backup Michelle Gong (Intel Corp) et al.

Utilize the More Data bit in the ACK frame Month Year doc.: IEEE 802.11-yy/xxxxr0 July 2008 Utilize the More Data bit in the ACK frame QSTA1 QSTA2 Buffered DATA (EOSP=0) Minimum Duration ACK (More data=1) Buffered DATA (EOSP=1) ACK (More data=1) Remain awake Buffered DATA (EOSP=0) ACK (More data=0) Buffered DATA (EOSP=1) ACK (More data=0) Go back to sleep Go back to sleep The shortest frame exchange during one wakeup period (Data(EOSP=1) / SIFS / ACK (MoreData=0) Michelle Gong (Intel Corp) et al. John Doe, Some Company