doc.: IEEE 802.11-12/1324r0
November 2012
Very Low Energy Paging
Date: 2012-11-12
Authors:
Name
Simone Merlin
Amin Jafarian
Bin Tian
Santosh Abraham
Menzo Wentink
Hemanth Sampath
VK Jones
Yongho Seok
Qualcomm
Qualcomm
Qualcomm
Qualcomm
Qualcomm
Qualcomm
Qualcomm
LG
Electronics
Jinsoo Choi
Matthew Fischer
LG
Electronics
LG
Electronics
LG
Electronics
Broadcom
Eric Wong
Rojan Chitrakar
Broadcom
Panasonic
Ken Mori
Panasonic
Jeongki Kim
Jin Sam Kwak
Phone
email
5775 Morehouse Dr, San
Diego, CA
8588451243
[email protected]
LG R&D Complex AnyangShi, Kyungki-Do, Korea
+82-31-450-1947
[email protected]
190 Mathilda Place,
Sunnyvale, CA
+1 408 543 3370
[email protected]
Affiliations Address
[email protected]
[email protected]
.com
[email protected]
Slide 1
S. Merlin et al.
doc.: IEEE 802.11-12/1324r0
November 2012
Name
Affiliations
Address
Phone
email
Minyoung Park
Tom Tetzlaff
Emily Qi
Yong Liu
Hongyuan Zhang
Intel Corp.
Intel Corp.
Intel Corp.
Marvell
Marvell
[email protected]
Sudhir Srinivasa
Marvell
[email protected]
Sun, Bo
Lv, Kaiying
Huai-Rong Shao
Chiu Ngo
Minho Cheong
ZTE
ZTE
Samsung
Samsung
ETRI
[email protected]
Jae Seung Lee
Hyoungjin Kwon
Jaewoo Park
Sok-kyu Lee
Sayantan Choudhury
ETRI
ETRI
ETRI
ETRI
Nokia
Klaus Doppler
Chittabrata Ghosh
Esa Tuomaala
Nokia
Nokia
Nokia
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
138 Gajeongno,
Yuseong-gu, Dajeon,
Korea
+82 42 860 5635
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
2054 University Avenue,
Suite 600, Berkeley, CA
94704
Slide 2
+1 510 599 9268
[email protected]
S. Merlin et al.
doc.: IEEE 802.11-12/1324r0
November 2012
Name
Affiliations
Address
Phone
email
1 Fusionopolis Way, #21-01
Connexis Tower, Singapore
138632
+65-6408 2000
[email protected]
Shoukang Zheng
I2R
Haiguang Wang
Wai Leong Yeow
Zander Lei
Jaya Shankar
Anh Tuan Hoang
George Calcev
I2R
I2R
I2R
I2R
I2R
I2R
Huawei
Osama Aboul Magd
Huawei
Osama.AboulMagd@huawe
i.com
Young Hoon Kwon
Betty Zhao
David Yangxun
Bin Zhen
ChaoChun Wang
James Wang
Jianhan Liu
Vish Ponnampalam
James Yee
Thomas Pare
Kiran Uln
Anna Pantelidou
Juho Pirskanen
Timo Koskela
Liwen Chu
George Vlantis
Huawei
Huawei
Huawei
Huawei
MediaTek
MediaTek
MediaTek
MediaTek
MediaTek
MediaTek
MediaTek
Renesas Mobile
Renesas Mobile
Renesas Mobile
[email protected]
Joseph Teo Chee Ming
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
Rolling Meadows,
IL USA
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
m
[email protected]
[email protected]
vish.ponnampalam@mediatek.
com
[email protected]
[email protected]
[email protected]
STMicroelectronics
STMicroelectronics
Slide 3
S. Merlin et al.
doc.: IEEE 802.11-12/1324r0
November 2012
Introduction (I)
•
In sensor networks, an important class of applications will have low duty cycle UL
and DL traffic, but may have strict latency requirements in receiving DL data
– Respond to alarms with < 1s latency
– 100ms latency expected for commands (e.g. gaming or actuators)
•
STA must check with AP if data is pending at least every ‘max latency’ interval
– Data though may be very sporadic
•
Regular PS mode (use the short beacon to indicate DL data) is not efficient
enough to make 11ah competitive with other technologies
– Short beacon [1] is 560us preamble + (>13B+TIM @ 150Kbps) > 1.5ms
– Moreover, TIM size is not bound and additional fields/IEs can be present, making the
frame longer and decoding energy consuming
•
To be competitive with other technologies, 802.11ah must provide a further
optimized protocol for low latency DL traffic
Slide 4
S. Merlin et al.
doc.: IEEE 802.11-12/1324r0
November 2012
Introduction (II)
• We propose an enhanced paging protocol that uses a short NDP frame as
short paging message
– Provides shorter RX time, compared to receiving Beacon or TIM Frame
– Additionally enables the design of energy efficient receivers, optimized for the
NDP paging message
•
•
•
Other technologies use ad-hoc “wakeup receivers” for very low energy operation
802.11ah has the chance to define a similar mechanism in native form
The protocol can coexist with existing 802.11 power save operation modes and is
built on top of existing 802.11ah mechanisms (TWT with synch frame [2])
Slide 5
S. Merlin et al.
doc.: IEEE 802.11-12/1324r0
November 2012
Proposal (I)
•
When requested by a STA, the AP schedules a very short paging message at the
target wake time of the STA as the next frame for transmission
• STA may indicate a max period of time after the TWT it will be still accepting the NDP paging
message
– If STA receives the message, STA should
• Option1: act as if it received a TIM indicating BUs, i.e. send PS-Poll or trigger frame
• Option2: go read the next (short) beacon and proceed as in regular PS
• Option3: wait for a further poll message from AP after a certain time
•
The very short paging message is a NDP control frame, including
– A (partial) identifier of the STA being paged
• Same AID may identify multiple STAs (group ID)
– One bit indicating whether there is a BU for the STA
– Synchronization info, e.g. few LSBs of timestamp
– One or more bits indicating if STA need to check the beacon
Slide 6
S. Merlin et al.
doc.: IEEE 802.11-12/1324r0
November 2012
Proposal (II)
P
Sleep
•
•
•
Optimized
RX ON
TWT 560us
P
Beacon
Sleep
P= Short Paging message
TBTT
In regular PS mode, the STA decodes the (short) beacon at least every ‘max latency’ interval
– Short beacon > 1.5ms
In our proposal, the STA skips the beacon and instead decodes the short ‘NDP’
– NDP > 3 times shorter receive time than short beacon
Moreover, if the only paging message at the TWT is a well defined NDP, an optimized
receiver can be used at the TWT, instead of the ‘full’ receiver
–
–
PHY receiver optimized to detecting/decoding an NDP frame only
Very limited operations upon reception: no ‘MAC’
Slide 7
S. Merlin et al.
doc.: IEEE 802.11-12/1324r0
November 2012
Energy saving computation
•
Assumptions on regular operation with short beacon
–
–
•
Assumptions on operation with short NDP packet
–
–
•
STA reads a short beacon every X seconds
• Assume there is no BU, but still STA needs to check the beacon to guarantee the latency
Beacon: 16 Bytes at MCS0 rep2 (1.4ms)
• This is an optimistic length, assuming very short TIM and no optional fields in beacon
STA reads short paging message every X seconds
Short paging message: 560us
Common parameters
–
–
–
–
RX power: 100mW
Sleep power: 10uW
Clock drift: 20ppm [each side]
Wakeup: 2.1ms, at 2.4mW [from an actual Zigbee product]
Slide 8
S. Merlin et al.
doc.: IEEE 802.11-12/1324r0
November 2012
Energy saving evaluation
-3
Avearge Power [W]
2
1
0.5
Battery life increase %
0
0.5
1
1.5
Latency [s]
2
2.5
3
3
2
1
Short Paging 1MHz
0
0
0.5
1
1.5
Latency [s]
2
2.5
3
Shorter paging frame provides 2.4x power consumption reduction when a 100ms latency is
required
–
–
•
Regular PS mode
Short Paging 1MHz
1.5
0
•
x 10
Translates in 2x battery life
Results are conservative in that the shortest possible length of beacon was used
Moreover, optimized receivers can be designed to further lower the energy consumption
Slide 9
S. Merlin et al.
doc.: IEEE 802.11-12/1324r0
November 2012
Proposal (III)
•
Note: The proposed operation mode is targeted at very low duty cycle data
– We target an operation mode where it is very unlikely that multiple STAs need be paged
at the same time
•
Multiple STAs though can be paged at same or similar times
– Different STAs may be assigned different (nearby) TWTs, or
– Multiple STAs may be assigned same TWT
• A group ID can be defined to page multiple STAs
• The proposed mechanism can be seen as an enhancement to the Target
Wake Time with Synch frame [2]
Slide 10
S. Merlin et al.
doc.: IEEE 802.11-12/1324r0
November 2012
Proposed SFD text
Existing text [2]
• R.4.2.E: When requested by a STA, the AP sends a UL synch frame at the slot boundary or
the target wake time of the STA, if the channel is idle, to help the STA quickly synch to the
medium. (optional to AP and STA) [July 2012 meeting minutes, 11-12/840r0]
–
It is recommended that when requested by the STA, the AP sends a Short CTS frame defined in
4.4.2.3 as a synch frame. [12/840r1, September 2012 meeting minutes]
[Note: Short CTS content is not defined yet]
Proposed additional text
• When requested by a STA, the AP schedules a DL synch frame at the slot boundary or the
target wake time of the STA as the next frame for transmission
Synch frame is an NDP frame including at least
• A (Partial) identifier of the target STA(s)/group of STAs (# bits TBD)
• BU present (1 bit)
• Partial TSF (# bits TBD)
• Check beacon (# bits TBD)
Slide 11
S. Merlin et al.
doc.: IEEE 802.11-12/1324r0
November 2012
Conclusions
• DL traffic with stringent latency requirements is an important use case,
which can cause significant power consumption due to TIM reception
– 11ah is not competitive enough on this front
• 11ah has the chance to introduce a native support for a very efficient
paging mechanism, that also allows for optimized receivers
– Other technologies use dedicated wakeup signals/receivers
• We propose a short paging NDP message and a simple paging protocol
that is compatible with 802.11 baseline PS and with 802.11ah
mechanisms
Slide 12
S. Merlin et al.
doc.: IEEE 802.11-12/1324r0
November 2012
Straw polls
1.
Do you support to define a short NDP frame for paging, that includes (at
least) the following fields
•
•
•
•
2.
A (Partial) identifier of the target STA(s)/group of STAs (# bits TBD)
BU present (1 bit)
Partial TSF (# bits TBD)
Check beacon (# bits TBD)
Do you support to define an optimized paging protocol that uses a short
NDP frame as described in slide 11?
Slide 13
S. Merlin et al.
doc.: IEEE 802.11-12/1324r0
November 2012
References
•
•
[1] TGah SFD document, DCN 11/1137, section 4.4.1.1
[2] TGah SFD document, DCN 11/1137, section R.4.2.E
Slide 14
S. Merlin et al.
doc.: IEEE 802.11-12/1324r0
November 2012
Appendix
Considering the case of STA using unsolicited PS-Poll every ‘max latency’ interval
– PIFS+Short_PS_Poll+SIFS+Short_ACK
– Using same parameters as slide 7 [drift not relevant for sending PS-Poll]
-3
Avearge Power [W]
2
x 10
Regular PS mode
Short Paging 1MHz
PS-Poll
1.5
1
0.5
0
Battery life increase %
•
0
0.5
1
1.5
Latency [s]
2
2.5
3
3
2
1
Short Paging 1MHz
PS-Poll
0
0
0.5
1
1.5
Latency [s]
2
2.5
3
No benefits from the use of unsolicited PS-Poll for low latencies
Slide 15
S. Merlin et al.