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Low-Power PS-Poll

Low-Power PS-Poll. Authors:. Date: 2012-05-17. Abstract. In this contribution, we present the scheme to support low power medium access with low-power PS-Poll. Low Power Medium Access. In 802.11ah use cases, battery-operated devices benefit from the low power operation

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Low-Power PS-Poll

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  1. Low-Power PS-Poll Authors: Date: 2012-05-17 Shoukang Zheng et. al, I2R, Singapore

  2. Abstract In this contribution, we present the scheme to support low power medium access with low-power PS-Poll. Shoukang Zheng et. al, I2R, Singapore

  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 Shoukang Zheng et. al, I2R, Singapore

  4. 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 Shoukang Zheng et. al, I2R, Singapore

  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 Shoukang Zheng et. al, I2R, Singapore

  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. Shoukang Zheng et. al, I2R, Singapore

  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 Shoukang Zheng et. al, I2R, Singapore

  8. 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 Shoukang Zheng et. al, I2R, Singapore

  9. 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 Shoukang Zheng et. al, I2R, Singapore

  10. 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 Shoukang Zheng et. al, I2R, Singapore

  11. 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 Shoukang Zheng et. al, I2R, Singapore

  12. 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) Shoukang Zheng et. al, I2R, Singapore

  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. 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

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