1. Power efficient and unified 802.11s solution
Month Year
doc.: IEEE yy/xxxxr0
October 2007
Power efficient and unified s solution
Date:
Authors:
Jarkko Kneckt, Nokia
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
October 2007
Abstract
This presentation provides a high level view of the s mesh network as seen by the authors. Detailed proposal is given on power save mechanisms. In general the objective has been to have a standard amendment with a feature set meeting the following main objectives:
suitable for both backbone and ad hoc type of mesh networks
power save mechanisms defined to allow for battery powered MPs
one solution to one problem
Jarkko Kneckt, Nokia
John Doe, Some Company

3. Contents Introduction Basic components Power save in details
October 2007
Contents
Introduction
The big picture
Basic components
Five basic components of MPs
Power save in details
Two levels of power save
Power mode transition rules
Peer service period
Jarkko Kneckt, Nokia

4. Power save in Mesh The power save consists on 2 capabilities:
October 2007
Power save in Mesh
The power save consists on 2 capabilities:
Support of power save to enable power save for peer MPs
Operation in power save mode and save power by shutting down the receiver
The support for power save does not enable the power save supporting MP itself to operate in power save mode
The support for power save enables operation in power save for peer MPs
The operation in power save is optional capability
The power save enables MP to operate in doze state and to reduce power consumption
Jarkko Kneckt, Nokia

5. October 2007
Support for power save
The support for power save contains capabilities to:
keep track of the power modes of the peer MPs
buffer unicast frames for the power saving peer MPs
transmit data according to the power mode of the peer MP; by using service periods or as soon as possible
The mechanisms to transmit data according to power mode of the peer MP are presented in the following slides
Jarkko Kneckt, Nokia

6. Power save proposal in nutshell
October 2007
Power save proposal in nutshell
The proposal builds upon the current two power management modes
Active mode
Power save mode
Two levels of power save proposed
Light sleep designed for battery powered active MPs
Deep sleep provides a low duty cycle mode for all the MPs
Light sleep power save operations are based on wake-up signaling in beacons and a U-APSD –like operations
Deep sleep MP can be woken up only after its own mesh DTIM beacons for short data exchange periods
Jarkko Kneckt, Nokia

7. Power management modes
October 2007
Power management modes
Active mode
The MP is awake all the time
Power save mode
Light sleep – “Diet sleep”
The MP is awake during the time needed to send own mesh beacon, receive the peer MP mesh beacons, and to serve peer links as per the mesh service period rules
Designed to be used when the MP desires to reduce the power consumption and the full bandwidth is not needed for data from/to the peer MPs
Deep sleep
The MP is awake during the own mesh DTIM beacon and the following Awake Window, and to serve any subsequent mesh service periods
Designed to be used when there is no or very limited amount of traffic from/to the peer MPs
Jarkko Kneckt, Nokia

8. Minimum activity in power saving MP
October 2007
Minimum activity in power saving MP
MP1
= Minimum activity of active mode MP1
=Minimum activity of light sleep mode MP1
= Minimum activity of deep sleep mode MP1
MP1 and MP2 are peer-MPs to each other
MP2
= DTIM beacon
= TIM beacon
= Awake Window
Jarkko Kneckt, Nokia

9. The basic rules of light sleep
October 2007
The basic rules of light sleep
Beaconing MP uses Mesh TIM field in its own beacon to indicate presence of buffered data to power saving peer MPs
Power saving MP checks if the peer MP indicates presence of buffered data for it
If the bit is set, the MP triggers a peer service period
Beaconing MP serves power saving peer MPs to which it has buffered data during peer service periods
Doze state can be entered only when all the peer service periods have been closed
The peer service period handling rules are described later in the slide set
Beacon
Beacon
Trigger frame
ACK
Peer service period
Jarkko Kneckt, Nokia

10. The basic rules of deep sleep
October 2007
The basic rules of deep sleep
Power saving MP in deep sleep shall be active at least during its mesh DTIM beacon and the following Awake Window
The Awake Window is used for two purposes
MPs can request specific actions from the power saving MP
The MP in deep sleep transmits multicast and broadcast frames to peer MPs
Specific actions one can request during the Awake Window depend on the requesters role
Peer MP can use the Awake Window to initiate a mesh service period with the power saving MP
Non-peer MP can use the Awake Window to transmit a mesh management frame related to mesh discovery or peer link establishment
Jarkko Kneckt, Nokia

11. Data transmission between deep sleep mode MPs
October 2007
Data transmission between deep sleep mode MPs 1. 2.
Power mode of MP1 seen by MP2
Operation state of MP1 3. 4.
Power mode of MP2 seen by MP1
Operation state of MP2
= DTIM beacon
= Awake Window
= peer service period
= Operation in deep sleep mode
= Doze state
= Awake state
MP1 receives null frame during its Awake window. A peer service period is triggered.
MP1 receives frames during its peer service period.
MP1 sends null frame to MP2 during Awake window of MP2 to trigger a peer service period.
MP1 transmits the frames to MP2 during the peer service period.
Jarkko Kneckt, Nokia

12. Deep sleep mode summary
October 2007
Deep sleep mode summary
Deep Sleep offers low duty-cycle power save for MPs
The deep sleep mode should be used, when network has little or no data to transmit
Data transmission between MPs in deep sleep is possible, but may introduce delays
The deep sleep mode MP has low power consumption that is independent from the amount of the peer MPs
Jarkko Kneckt, Nokia

13. Mode and level transitions (1/2)
October 2007
Mode and level transitions (1/2)
Power save mechanisms are link specific
In some traffic models or network topologies it may make sense to raise the local MP to operate in higher power save level (or power management mode) for only one or few peer links
Transition to lower power save level needs to be unicasted because only those are acknowledged
Robust and reliable power management state transitions from higher power save level to lower power save level require acknowledgement from the peer MP
Transition to higher power save level may use unicast, multicast and broadcast transmissions
The transition from a lower power save level to a higher one is robust
Even if MP assumes that the peer MP operates on the lower power save level, it will not cause failure to frame transmission
Jarkko Kneckt, Nokia

14. Mode and level transitions (2/2)
October 2007
Mode and level transitions (2/2)
Two bits in the MAC header indicate the power management mode
Power management bit indicates whether the MP operates in active or power save mode
The power save level bit indicates the level of the power save, when the MP has set the power management bit to 1
Power management indicated in BC/MC frames is set as per the lowest power management mode used in the links
The power management mode that is indicated in BC/MC frames is used also by non-peer MPs to determine the times for scan and link creation frame exchange
Power management mode
Power Management bit
Power Save Level bit
Active mode -
Power Save Light Sleep 1
Power Save Deep Sleep
Jarkko Kneckt, Nokia

15. Power save support for different power modes
October 2007
Power save support for different power modes
The power save supporting MP sets indication of the buffered traffic to beacons it transmits for light sleep MPs.
The power save supporting MP transmits null frame during the Awake window of the deep sleep mode MP to indicate buffered frames.
Mesh DTIM Beacon frame from deep sleep mode MP triggers the null frame creation to the transmission buffer
The lifetime of the null frame is set to the end of the Awake window.
Power save supporting MP may indicate buffered traffic for the deep sleep MP in the beacons it transmits.
The support for power save does not require synchronization.
The operation in power save mode requires some level of synchronization to wake up to listen to beacons from peer MPs
Jarkko Kneckt, Nokia

16. October 2007
Peer service periods – enabling transmissions while MP operates in power save mode
The MP may use peer service periods for data transmission, when it is operating in power save mode, i.e. have power management bit set to 1
A peer service period is initiated by acknowledged trigger frame
Unicasted and acknowledged PS-POLL, QoS-Null, data and management frame may be used as a trigger frame.
Peer service periods are link specific
The peer MP shall be active for the duration of the peer service period
During a peer service period, frames from all ACs may be transmitted
Trigger frame’s AC does NOT limit the ACs of the frames transmitted during the peer service period
Peer service period may contain one or more TXOPs.
Jarkko Kneckt, Nokia

17. Peer service period types
October 2007
Peer service period types
MPs use peer link creation signaling to signal the used service period type for the link.
If both MPs set Bi-directional Peer Service Periods bit in Mesh Capability field to 1 in Peer Link Open and Confirm frames bi-directional peer service periods are used for the link
Otherwise unidirectional service periods are used for the link
Peer service period type:
Unidirectional peer service period enable:
An MP to transmit data during the peer service period
The peer service period is terminated when the MP indicates that the last frame is transmitted and receives acknowledgement for the frame.
Bi-directional peer service period enable:
Both MPs to transmit data during the peer service period
Triggering a bi-directional peer service period, in power mode transitions, if peer MP has buffered frames
The peer service period is terminated when both data frame and acknowledgement indicate that all buffered traffic is transmitted
Jarkko Kneckt, Nokia

18. MAC frame header bits used in peer service periods
October 2007
MAC frame header bits used in peer service periods
More Data (MD) bit in unicast data frames
Indicates the status of the buffered unicast frames for the receiver
MD bit in multicast and broadcast frames and bit 0 in Mesh TIM element
Indicates if more multicast or broadcast will be transmitted by the MP
End of Service Period (EOSP) Bit in unicast frames
Indicates termination of the service period
The separation of MD bit and EOSP enables the separate transmission buffer status information passing and control for service periods. See slides at the end of the presentation (30->)
By using both MD and EOSP the indication of the buffered traffic and termination of the peer service period.
802.11e and U-APSD uses both MD and EOSP bits. By using the same fields, the s power save mechanisms are compatible with infrastructure mode mechanisms.
Jarkko Kneckt, Nokia

19. Triggering of peer service period
October 2007
Triggering of peer service period
null, data, management or ps-poll frame may be used as a trigger frame.
Unidirectional peer service period:
Null and ps-poll trigger frames initiate a peer service period that is owned by the receiver of the trigger frame. The receiver may send data and management frames during the service period.
Management and data trigger frames initiate two peer service periods so that both the transmitting MP and the receiving MP own a peer service period.
Bi-directional service period:
All trigger frames trigger a bi-directional service period, which enable both MPs to transmit frames.
Jarkko Kneckt, Nokia

20. Termination of the unidirectional peer service periods
October 2007
Termination of the unidirectional peer service periods
Termination of one unidirectional peer service period
Termination of two unidirectional peer service periods
Both MP 3 and MP4 are data transmitters in the peer service periods. The peer service period from MP3 is terminated, when MP3 transmits a frame with set EOSP bit. MP4 acts accordingly with its own peer service period.
MP 1 is data transmitter in the peer service period.
The peer service period is terminated when MP1 indicates that it does not have more data to transmit with EOSP.
Data
Data
Ack
Ack
Data, EOSP=1
Data, EOSP=1
Ack
Ack
Data, EOSP=1
Ack
MP1
MP2
MP3
MP4
= MP may transmit data
= MP may receive data
EOSP = End of service period bit
Jarkko Kneckt, Nokia

21. Mesh service period between active mode and light sleep MPs
October 2007
Mesh service period between active mode and light sleep MPs
MP1 indicates in beacon that it has data pending
MP1 has data to be sent for MP2 and MP1 indicates it in its beacon
MP2 responses with appropriate trigger frame which initiates mesh service period
Service period is ended with setting of EOSP bit after the MP1 buffers further data for MP2
MP2 may trigger a peer service period at any time
Beacon
MP2 responses with trigger frame starting mesh service period
Data
Ack
Data
Ack
Data, EOSP=1
Ack
MP1
MP2
= Light sleep mode MP
= Active mode MP
= MP may transmit data
= MP may receive data
Jarkko Kneckt, Nokia

22. Peer service period handling (1/2)
October 2007
Peer service period handling (1/2)
MP1 and MP2 have a peer service period.
MP1 terminates the peer service period and sets in the termination frame:
MD to1 to indicate that it has more data to transmit to the MP2.
Power management mode to 1 to indicate operation in active mode.
MP2 may trigger MP1 at any time when MP1 is active.
New peer service period is triggered and the termination of the peer service period sets MP1 to power save mode and both MPs may return to doze state.
Data
Ack
Data, PM =0, MD=1, EOSP =1
Ack
null,
Ack
Data, PM=1,MD=0, EOSP=1
Ack
MP1
MP2
= Light sleep mode MP
= Active mode MP
= MP may transmit data
= MP may receive data
Jarkko Kneckt, Nokia

23. Peer service period handling (2/2)
October 2007
Peer service period handling (2/2)
MP1 and MP2 have a peer service period ongoing.
MP1 terminates the peer service period and sets in the termination frame:
MD to1 to indicate that it has more data to transmit to the MP2.
MP2 may trigger MP1 after the beacon transmission from MP1.
New peer service period is triggered after the beacon from MP1 and the termination of the peer service period enables both MPs to return to doze state.
Data
Ack
Data, MD=1, EOSP =1
Ack …
Beacon.Tim set for MP2
null
Ack
Data, MD=0, EOSP=1
Ack
MP1
MP2
= Light sleep mode MP
= MP may transmit data
= MP may receive data
Jarkko Kneckt, Nokia

24. Bi-directional peer service periods
October 2007
Bi-directional peer service periods
Bi-directional peer service periods enable:
better efficiency and controllability of the mesh service period, because both sides may actively transmit data and other MP is not forced to receive only
Better coordination to transition from active mode to power save, no lost frames in power mode transition
Efficient termination, one frame and ack transmission to terminate a peer service period
Signaling examples are shown in the following slides.
Jarkko Kneckt, Nokia

25. Bi-directional peer service period
October 2007
Bi-directional peer service period
Operation during the bi- directional mesh service period
Both MPs are in light sleep mode
Both MPs indicate that they have transmitted all frames. After data frame transmission, which contains more data bit set to 0 and ack with more data bit set to 0, the peer service period is terminated.
Data
Ack
Data, EOSP=1
Ack, MD=1
Data, EOSP=1
Ack, MD=0
MP3
MP4
= MP may transmit data
= MP may receive data
Jarkko Kneckt, Nokia

26. October 2007
Active mode to light sleep transition, bi-directional peer service periods used
The MP3 indicates that it does not have any data to be sent and it is going to power save mode.
MP4 has data in its buffers and it initiates mesh service period which keeps MP3 in active mode until end of mesh service period.
MP3 may send any additional data it has during the mesh service period
MP indicates that is does not have data to be sent anymore and it moves to power save mode
Data
Ack
MP initiates mesh service period, receiving MP waits until mesh service period has ended before going to
Data, PM=1
Ack, MD=1
Data
Ack
Data, EOSP=1
Ack, MD = 0
MP3
MP4
= Light sleep mode MP
= MP may transmit data
= MP may receive data
= Active mode MP
Jarkko Kneckt, Nokia

27. Mesh service period summary
October 2007
Mesh service period summary
Unidirectional Mesh Service Period
Used when link configured to support only unidirectional service periods
Used in between active mode and light sleep mode MPs
Bi-directional Mesh Service Period
Provides efficient method to send data between light sleep MPs when there isn’t equal amount of data to be sent and other MP is not forced to receive only
Better coordination to transition from active mode to power save, no lost frames in power mode transition
Efficient termination through a single frame and ack transmission.
Jarkko Kneckt, Nokia

28. October 2007
Appendix, power consumption calculations in different power management modes
Jarkko Kneckt, Nokia

29. Calculations on stand-by modes power consumption
October 2007
Calculations on stand-by modes power consumption
r2 (Power save and routing) presentation presents radio power consumption parameters and beacon transmission density.
Next slide is copied from the presentation in order to provide power consumption analysis for beaconing mechanisms.
The presentation calculates power consumption estimations for IBSS beaconing, light sleep and deep sleep beaconing modes.
Jarkko Kneckt, Nokia

30. Month Year
doc.: IEEE yy/xxxxr0
October 2007
A quantitative analysis of benefit derived from power management mechanism
Some calculation:
Assumption on the power consumption  captured from [1]
Operational parameter setting
Beaconing interval : 1000 /100ms
DTIM interval : 0 (every beacon is DTIM beacon, no TIM beacons)
ATIM Window : 10 / 5 / 2,5 ms
Ramp up margin: 1ms
Number of neighbouring peer MPs : 6
Beacon frame length: 200us
Take this parameters for example
Jarkko Kneckt, Nokia
John Doe, Some Company

31. Analysis on benefits derived from power save capabilities
October 2007
Analysis on benefits derived from power save capabilities
Case 1. MP uses IBSS beaconing, all peers are using the same beacon.
MP transmits every seventh (1/7) beacon and receives 6/7 of the beacons. MP stays active during the ATIM period.
Total power consumption per 1[sec]
Amount of beacons per second x (ramp up + 1/7 beacon transmission + 6/7 beacon reception + ATIM Wakeup) + rest of time x Doze State power drain
Jarkko Kneckt, Nokia

32. Analysis on benefits derived from power save capabilities
October 2007
Analysis on benefits derived from power save capabilities
IBSS beaconing power consumption results
IBSS
ATIM = 10ms
ATIM = 5ms
ATIM = 2,5ms
Time [s]
Wakeup
0,001
Idle
0,0098
0,0048
0,0023
Total RX
0,000171
Total TX
2,86E-05
Sleep
0,989
0,994
0,9965
C [mA_s]
1,6848
0,9048
0,5148
0,032571
0,008114
9,89
9,940
9,965
Power [mW]
7,986
4,289
2,440
0,154
0,038
46,879
47,116
47,234
Total Power [mW]
Power, 1 beacon / 1 second
55,06
51,60
49,87
Power, power for sleep is not included
8,18
4,48
2,63
Power 10beacons / 1second
123,97
89,37
72,07
81,78
44,82
26,33
Note,
The time consumption is given for 1 beacon/second case.
Jarkko Kneckt, Nokia

33. Analysis on benefits derived from power save capabilities
October 2007
Analysis on benefits derived from power save capabilities
Case 2. MP operating in light sleep
Total power consumption per 1[sec]
Amount of beacons per second x [ (ramp up + beacon transmission + ATIM Wakeup) + 6*(ramp up + beacon reception)] + rest of time x Doze State power drain
Jarkko Kneckt, Nokia

34. Analysis on benefits derived from power save capabilities
October 2007
Analysis on benefits derived from power save capabilities
Light Sleep beaconing power consumption results
Light Sleep
ATIM = 10ms
ATIM = 5ms
ATIM = 2,5ms
Time [s]
Wakeup
0,007
Idle
0,0098
0,0048
0,0023
Total RX
0,0012
Total TX
2,00E-04
0,0002
Sleep
0,9818
0,9868
0,9893
C [mA_s]
2,6208
1,8408
1,4508
0,228
0,0568
9,818
9,868
9,893
Power [mW]
12,422592
8,725
6,877
1,08072
1,081
0,269232
0,269
46,53732
46,774
46,893
Total Power [mW]
Power, 1 beacon / 1 second
60,31
56,85
55,12
Power, power for sleep is not included
13,77
10,08
8,23
Power 10beacons / 1second
176,50
141,90
124,60
137,73
100,75
82,27
Note,
The time consumption is given for 1 beacon/second case.
Jarkko Kneckt, Nokia

35. Analysis on benefits derived from power save capabilities
October 2007
Analysis on benefits derived from power save capabilities
Case 3. MP operating in Deep sleep
Case assumes that MP using Deep Sleep receives every 10th (1/10) beacon from peer MPs in order to maintain links from timeout.
Total power consumption per 1[sec]
Amount of beacons per second x (ramp up + beacon transmission + ATIM Wakeup) + 6*(ramp up + beacon reception) /10 + rest of time x Doze State power drain
Jarkko Kneckt, Nokia

36. Analysis on benefits derived from power save capabilities
October 2007
Analysis on benefits derived from power save capabilities
Deep Sleep beaconing power consumption results
Deep Sleep
ATIM = 10ms
ATIM = 5ms
ATIM = 2,5ms
Time [s]
Wakeup
0,0016
Idle
0,0098
0,0048
0,0023
Total RX
0,00012
Total TX
2,00E-04
0,0002
Sleep
0,98828
0,99328
0,99578
C [mA_s]
1,7784
0,9984
0,6084
0,0228
0,0568
9,8828
9,933
9,958
Power [mW]
8,429616
4,732
2,884
0,108072
0,108
0,269232
0,269
46,844472
47,081
47,200
Total Power [mW]
Power, 1 beacon / 1 second
55,65
52,19
50,46
Power, power for sleep is not included
8,81
5,11
3,26
Power 10beacons / 1second
129,91
95,31
78,01
88,07
51,10
32,61
Note,
The time consumption is given for 1 beacon/second case.
Jarkko Kneckt, Nokia

37. Analysis on benefits derived from power save capabilities
October 2007
Analysis on benefits derived from power save capabilities
Total stand-by power consumption, excluding the sleep mode power consumption
Total stand-by power consumption
Beaconing interval [ms]
ATIM duration [ms]
Light Sleep
Deep Sleep
IBSS network
1000 10
13,77
8,81
8,18 5
10,08
5,11
4,48
2,5
8,23
3,26
2,63
100
137,73
88,07
81,79
100,75
51,10
44,82
82,27
32,61
26,33
Beaconing interval [ms]
ATIM duration [ms]
Light Sleep
Deep Sleep
IBSS network
1000 10
60,31
55,65
55,06 5
56,85
52,19
51,60
2,5
55,12
50,46
49,87
100
176,50
129,91
123,97
141,90
95,31
89,37
124,60
78,01
72,07
Jarkko Kneckt, Nokia

38. Strawpolls Does 802.11s Mesh networks need power save?
October 2007
Strawpolls
Does s Mesh networks need power save?
Yes No
Are you in favour of the power save enhancements presented in this slide set and described in r2?
Jarkko Kneckt, Nokia