doc.: ieee 802.11-12/0608r2 submission may 2012 shoukang zheng et. al, i2r, singaporeslide 1...
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doc.: IEEE 802.11-12/0608r2
Submission
May 2012
Shoukang Zheng et. al, I2R, SingaporeSlide 1
Low-Power PS-Poll
Date: 2012-05-17Authors:
Name Affiliations Address Phone email Shoukang Zheng I2R 1 Fusionopolis Way, #21-01,
Connexis South Tower, Singapore 138632
+65 6408 2252 [email protected]
Haiguang Wang I2R 1 Fusionopolis Way, #21-01, Connexis South Tower, Singapore 138632
+65 6408 2256 [email protected]
Jaya Shankar I2R 1 Fusionopolis Way, #21-01, Connexis South Tower, Singapore 138632
+65 6408 2239 [email protected]
Yeow Wai Leong I2R 1 Fusionopolis Way, #21-01, Connexis South Tower, Singapore 138632
Zhongding Lei
I2R 1 Fusionopolis Way, #21-01, Connexis South Tower, Singapore 138632
Joseph Teo Chee Ming
I2R 1 Fusionopolis Way, #21-01, Connexis South Tower, Singapore 138632
Hoang Anh Tuan I2R 1 Fusionopolis Way, #21-01, Connexis South Tower, Singapore 138632
Zhou Yuan I2R 1 Fusionopolis Way, #21-01, Connexis South Tower, Singapore 138632
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.
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
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
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
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.
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
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
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
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
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
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
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
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