doc.: IEEE /0409r6 Submission July 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 1 Channel Access Supporting Low Power Operation Date: Authors:

doc.: IEEE /0409r6 Submission July 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 2

doc.: IEEE /0409r6 Submission July 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 3

doc.: IEEE /0409r6 Submission July 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 4 Abstract In this contribution, we present the scheme to re-schedule doze/awake time for PS-Poll sent by STA supporting low power operation in ah networks

doc.: IEEE /0409r6 Submission July 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 5 Motivation In ah use cases, battery-operated devices benefit from the low power operation. 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 /1137r4].

doc.: IEEE /0409r6 Submission awake doze awake Example of Low Power Medium Access July2012 Shoukang Zheng et. al, I2R, SingaporeSlide 6 beaconbeacon PS-Poll ACK BU=1 DATA1DATA1 AP STA1 STA2 STA3 STA4 ACK BU=1 ACK BU=1 DATA1DATA1 Short Ack DATA2DATA2 Short Ack beaconbeacon DATA3DATA3 Short Ack DATA4DATA4 Short Ack PS-Poll doze

doc.: IEEE /0409r6 Submission Problems When a large number of STAs transmits PS-Poll after waking up –STA with buffered frame has to wait for DATA when AP is unable to respond promptly due to transmitting fragmented DATA retransmitting DATA taking time to determine the status of buffered frame busy processing other matters –AP may not complete the data transmissions for all the PS-Polls in the beacon interval –When data rate is low, STAs waste more power to contend/wait July 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 7

doc.: IEEE /0409r6 Submission Suggested Solution Re-scheduling doze/awake time –PS-Poll not followed by DATA or immediate ACK, 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 –The reply may contain traffic indication for STAs If PS-Polling STA knows no buffered frame, it goes to sleep If PS-Polling 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 –STA can re-sync to the beacon with the help of the timer –AP determines to use the protocol [1] or this proposed scheme July 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 8

doc.: IEEE /0409r6 Submission Turning into Paged STA After non-TIM STA is switched to Power Save Mode, AP can assume that non-TIM STA is going to become paged STA and wake up in the next beacon transmission time If the beacon carries the slot information associated with the TIM bit for it to receive downlink buffered unit, this paged STA (originally non-TIM STA) may not send PS-Poll again The above paged STA can go to sleep till the assigned slot if there is no uplink data to transmit In the assigned time slot, the paged STA wakes up to receive the downlink data from the AP Slide 9 July 2012 Shoukang Zheng et. al, I2R, Singapore

doc.: IEEE /0409r6 Submission doze awake doze awake Example of Proposed Scheme July 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 10 beaconbeacon PS-Poll ACK BU=1 DATA1DATA1 AP STA1 STA2 STA3 STA4 Timer BU=1 Timer BU=1 DATA1DATA1 Short Ack DATA2DATA2 Short Ack beaconbeacon DATA3DATA3 Short Ack DATA4DATA4 Short Ack PS-Poll doze

doc.: IEEE /0409r6 Submission July 2012 Slide 11 Conclusions We propose to support low power operation through the re- scheduling of doze/awake time for the STAs. The timer can be used to indicate the beacon transmission time to support the above rescheduling. Shoukang Zheng et. al, I2R, Singapore

doc.: IEEE /0409r6 Submission July 2012 Slide 12 References [1] 11-12/127r1, Low Power Medium Access. Shoukang Zheng et. al, I2R, Singapore

doc.: IEEE /0409r6 Submission Straw Poll Do you agree that AP may reply to the PS-Poll with a timer indicating the re-scheduling of doze/awake time as in slide 8? Y: N: A: July 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 13