March 2012 doc IEEE 802 11 120409 r

March 2012 doc. : IEEE 802. 11 -12/0409 r 0 Supporting Low Power Operation Authors: Submission Date: 2012 -03 -13 Slide 1 Shoukang Zheng et. al, I 2 R, Singapore

March 2012 doc. : IEEE 802. 11 -12/0409 r 0 Abstract In this contribution, we present the scheme that AP delays the response to acknowledge the PS-Poll through TIM frame or re-scheduling doze/awake time through an indicated timer for power saving mode operation in 802. 11 ah networks. Submission Slide 2 Shoukang Zheng et. al, I 2 R, Singapore

March 2012 doc. : IEEE 802. 11 -12/0409 r 0 Motivation • In IEEE 802. 11 ah, battery-operated devices are required to support the low power consumption. • A STA with low power operation may not listen to Traffic Indication from the AP. It may send PS-Poll any time. The AP receives PS-Poll shall immediately respond with ACK or buffered data frame to the STA [IEEE 802. 11 -11/1137 r 4, Specification framework for TGah]. Submission Slide 3 Shoukang Zheng et. al, I 2 R, Singapore

March 2012 doc. : IEEE 802. 11 -12/0409 r 0 Problems • When a large number of STAs transmits PS-Poll after waking up, – STA may have to wait for DATA even if PS-Poll has been received by AP due to that AP is busy – Some STAs may not have buffered frames at the AP and should go to sleep as soon as possible – The procedure of immediate ACK following with DATA or immediate DATA transmission may cause more power consumption for awaking STAs without buffered frames at the AP – When data rate is low, STAs waste more power to contend/wait – PS-Poll transmission time may be very close to beacon/TIM transmission time Submission Slide 4 Shoukang Zheng et. al, I 2 R, Singapore

March 2012 doc. : IEEE 802. 11 -12/0409 r 0 Suggested Solution (1) • Delay the response to STA’s PS-Polling – If very close to beacon/TIM transmission time, AP is busy with other transmissions, or TIM segment doesn’t include the STA, the STA accepts a longer waiting time for the acknowledgment from the AP – After receiving one/a few PS-Polls, the AP starts to reply • The time is determined by AP and STA (e. g. during association or other management frame exchange). • Before the time expires, if AP still engages other transmissions, it may continue current transmissions without immediate response • The delay may be decided by the smaller value of the difference between the time to transmit PS-Poll and next related TIM transmission time, and a timer Submission Slide 5 Shoukang Zheng et. al, I 2 R, Singapore

March 2012 doc. : IEEE 802. 11 -12/0409 r 0 Suggested Solution (1) Cont’d • Delay the response to STA’s PS-Polling – The acknowledgment • TIM segments or TIM frames (independent of beacon as in 802. 11 v, where TIM broadcast allows such TIM frame) – Acknowledgement may be transmitted in a higher data rate – Other STAs • no buffered frame indicated, go to sleep • buffered frame indicated, wait for DATA from AP Submission Slide 6 Shoukang Zheng et. al, I 2 R, Singapore

March 2012 doc. : IEEE 802. 11 -12/0409 r 0 Suggested Solution (2) • Re-scheduling doze/awake time – PS-Poll not followed by DATA/immediate ACK, the AP replies to STA with a timer indicating when it should wake up again – The timer is considered short enough without causing too much clock drift so that the STAs are able to capture the traffic indication – The reply may contain traffic indication for STAs • If STA knows no buffered frame, it goes to sleep • If STA knows buffered frame for itself, it may go to sleep and wake up again after timer expires • Other STAs may make use of this timer Submission Slide 7 Shoukang Zheng et. al, I 2 R, Singapore

March 2012 doc. : IEEE 802. 11 -12/0409 r 0 Conclusions • We propose a delayed response scheme for the PS-Polls by STAs with low power operation. The collective acknowledgment through TIM segment/frame may reduce the power consumption for the awaiting STA with/without buffered frames at the AP. • We also propose to support low power consumption through the re-scheduling of doze/awake time for the PSPolling STAs. Submission Slide 8 Shoukang Zheng et. al, I 2 R, Singapore

March 2012 doc. : IEEE 802. 11 -12/0409 r 0 References [1] 11 -12/127 r 1, Low Power Medium Access. Submission Slide 9 Shoukang Zheng et. al, I 2 R, Singapore

March 2012 doc. : IEEE 802. 11 -12/0409 r 0 Straw Poll (1) • Do you agree that AP may delay the response to the PSPoll by the STA with low power operation? • Y: • N: • A: Submission Slide 10 Shoukang Zheng et. al, I 2 R, Singapore

March 2012 doc. : IEEE 802. 11 -12/0409 r 0 Straw Poll (2) • Do you agree to use TIM segment or frame as the collective acknowledgment when AP delays the response to the PS-Polls by the STAs with low power operation? • Y: • N: • A: Submission Slide 11 Shoukang Zheng et. al, I 2 R, Singapore

March 2012 doc. : IEEE 802. 11 -12/0409 r 0 Straw Poll (3) • Do you agree that AP may reply to the PS-Poll with a timer indicating the re-scheduling of doze/wake time as in slide 7? • Y: • N: • A: Submission Slide 12 Shoukang Zheng et. al, I 2 R, Singapore