1. doc.: IEEE 802.11-12/0608r2 Submission May 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 1 Low-Power PS-Poll Date: 2012-05-17 Authors:

2. doc.: IEEE 802.11-12/0608r2 Submission May 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 2 Abstract In this contribution, we present the scheme to support low power medium access with low-power PS-Poll.

3. doc.: IEEE 802.11-12/0608r2 Submission May 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 3 Low Power Medium Access In 802.11ah use cases, battery-operated devices benefit from the low power operation Spec framework for TGah [1] –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

4. doc.: IEEE 802.11-12/0608r2 Submission Problems When AP receives the PS-Poll sent by a STA listening to beacon/TIM, AP shall respond by ACK or buffered frame When AP receives the PS-Poll sent by low-power- operated STA without listening to beacon/TIM, AP shall respond by ACK with BU bit (set as 1 or 0) or buffered frame May 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 4

5. doc.: IEEE 802.11-12/0608r2 Submission May 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 5 Motivation Two types of PS-Polls –Power Saving Mode –Low Power Medium Access There may be different protocols for the above two PS-Polls The protocols need to know the type of PS-Poll due to different protocols How to know which type of PS-Poll

6. doc.: IEEE 802.11-12/0608r2 Submission May 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 6 Case 1 For STA supporting low power operation, no TIM bit is transmitted for non-TIM STA [2] –If PS-Poll is sent by low power STA and there is buffered frame, AP shall respond by ACK with BU = 1, and STA will check BU bit and wait for DATA after receiving ACK. –If PS-Poll is sent by power saving STA, AP shall respond by ACK ignoring BU bit, and STA will wait for DATA after receiving ACK. –If PS-Poll is sent by low power STA and there is no buffered frame, AP shall respond by ACK with BU = 0, and STA will check BU bit and can go to sleep after receiving ACK.

7. doc.: IEEE 802.11-12/0608r2 Submission May 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 7 Case 2 For a PS-Poll sent by low-power-operated STA, AP may respond with a timer [3] –As the acknowledgment to the STA –Other STAs can make use of this timer if RA for the ACK is broadcast address –Not required to check the status of buffered unit if BU bit is not used Helpful when AP can’t respond by ACK with BU bit set as 1 or 0 promptly in SIFS for a STA as it takes time to find out whether the STA is low-power- operated and has buffered unit

8. doc.: IEEE 802.11-12/0608r2 Submission Suggested Solution We propose the method to differentiate two types of PS-Polls: (1) normal PS-Poll for Power Saving STA where the STA listens to the TIM sent by its associated AP and (2) low-power PS-Poll for STA with low power operation –defining a Low-Power-PS-Poll bit in PS-Poll (simple) –giving a new type of control frame for the low-power PS-Poll by STA with low power operation May 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 8

9. doc.: IEEE 802.11-12/0608r2 Submission Low-Power PS-Poll Low-Power-PS-Poll bit in PS-Poll differentiates the normal PS-Poll from the low-power PS-Poll If a STA supporting low power operation transmits PS- Poll without listening to the beacon/TIM, it makes use of the Low-Power-PS-Poll bit to indicate that the PS- Poll is a low-power PS-Poll May 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 9

10. doc.: IEEE 802.11-12/0608r2 Submission AP’s response to Low-Power PS-Poll When AP receives the low-power PS-Poll, it follows the related protocol to handle this PS-Poll –For example, AP follows the protocol [1] or –Use normal ACK rather than short ACK without BU bit –Other enhancement if applicable May 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 10

11. doc.: IEEE 802.11-12/0608r2 Submission Method 1 for Low-Power PS-Poll bit Low-Power-PS-Poll bit can reuse Power Management bit –Setting it as 0 in normal PS-Poll to indicate the STA is low-power- operated and AP will handle it accordingly May 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 11

12. doc.: IEEE 802.11-12/0608r2 Submission Method 2 for Low-Power PS-Poll bit Low-Power-PS-Poll bit can use the reserved case of DURATION/ID field (see table below) –Use bit 13 to indicate (for the case of bit 14=1 and bit 15=1) May 2012 Shoukang Zheng et. al, I2R, SingaporeSlide 12

13. doc.: IEEE 802.11-12/0608r2 Submission May 2012 Slide 13 Conclusions We propose to use Low-Power-PS-Poll bit to differentiate the low-power PS-Poll sent by STA supporting low power operation from the normal PS-Poll. Shoukang Zheng et. al, I2R, Singapore

14. doc.: IEEE 802.11-12/0608r2 Submission May 2012 Slide 14 References [1] 11-12/1137r6, Specification Framework for TGah. [2] 11-12/610, Non-TIM Status in TGah. [3] 11-12/409, Supporting Low Power Operation. Shoukang Zheng et. al, I2R, Singapore