Transcript August 2001 doc.: IEEE 802.15-01/315r4 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: IEEE802.15.3: Overview of Power Save.

August 2001
doc.: IEEE 802.15-01/315r4
Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: IEEE802.15.3: Overview of Power Save Proposal.
Date Submitted: 14 August, 2001
Source: Jay Bain
Company: Time Domain
Address: 7057 Old Madison Pike
Voice: 256 922 9229 , FAX: 256 922 0853, E-Mail: [email protected]
Source: Mark E. Schrader
Company: Eastman Kodak Co.
Address: 4545 East River Road, Rochester, NY 14650-0898
Voice: 716-781-9561 , FAX: 716-781-9533, E-Mail: [email protected]
Abstract: This provides an overview of proposed incorporations in the draft standard relating to power
management.
Purpose: To provide information and solicit comments on proposed power management
Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for
discussion and is not binding on the contributing individual(s) or organization(s). The material in this
document is subject to change in form and content after further study. The contributor(s) reserve(s) the
right to add, amend or withdraw material contained herein.
Release:
The contributor acknowledges and accepts that this contribution becomes the property of IEEE and
may be made publicly available by P802.15
Submission
Slide 1
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Overview of MAC Power Save
Provide the protocol structure that
will allow a range of applications
the greatest opportunity to save
power.
Submission
Slide 2
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Possible Power Save Scenarios
• The mode with greatest power saving is
OFF!
• If OFF won’t do -- Associate with a
network and then:
– Take advantage of characteristics of
contention free period – reduce power in
slots not assigned to a device. (RPS)
– Take advantage of higher layer inactivity reduce power by skipping several beacons
and superframes. (EPS)
Submission
Slide 3
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
The enemies of power saving
• Constant high throughput requirements.
• Time to progress from startup to data
movement.
• Failure by higher layers to correctly structure
requirements for service
• Real characteristics of PHY and MAC
• Poor environmental conditions resulting in
lost packets and use of lower transmission
rates
Submission
Slide 4
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Reduced Power Save
RPS
Submission
Slide 5
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Period of Reduced Power Opportunity
• PNC may be an RPS device
• Stay awake for
–
–
–
–
Beacon
CAP
Assigned receive slot
Assigned send slot with
activity
• Consider receive slot as
empty after 25% of duration
Submission
Slide 6
Slot
Contention
Access
Period
Assigned
Contention Free Period
Assigned
Slot
Beacon
RPS Operation
• Slot location
– Higher layers make
realistic RPS QoS
requirement known to
device
– PNC required to make
best effort to locate
assigned slot nearest
beacon
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Extended Power Save
EPS
Submission
Slide 7
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Presuppositions 1
• Sleeping really means waking periodically to
check the beacon, etc.
• The sending station and the receiving station
will synchronize their wakeups to the same
superframe if possible.
• The PNC needs to be able to communicate
with EPS stations. It must know on what
cycles the EPS station will be listening.
Submission
Slide 8
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Presuppositions 2
• The AWAKE QoS requirements will be
greater than or equal to the EPS QoS
requirements (which could go to zero).
• There are two primary AWAKE scenarios
needed to satisfy its AWAKE transmission
requirements.
– The sender may want only one superframe of
AWAKE mode transmission before return to EPS.
– The sender may want multiple or continuous
superframes of AWAKE mode transmission.
Submission
Slide 9
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Proposed Solution Overview
• Allow stations separate allocations of
requested channel time for EPS and for
AWAKE. Allow less than one slot per
superframe as a valid period between
allocated slots.
• The existence of the CTA indicates that both
stations will be awake for this superframe.
• The PNC knows all EPS intervals.
• Allow zero allocation length so that a CTA
element (with EPS destination ID) will be
generated by the PNC but no slot length will
be allocated to the station.
Submission
Slide 10
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
EPS Example Scenarios
Submission
Slide 11
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Introduction to the Scenarios
•
Four examples supported in EPS
Mode
1. Inactive EPS to high throughput awake
2. Inactive EPS to very low throughput
awake
3. Data in EPS to high throughput awake
4. Inactive EPS to Momentary awake
Submission
Slide 12
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Scenario 1 – Inactive EPS to high throughput awake
AWAKE
Submission
Mode
Sender: to PNC
“Switch to AWAKE
mode CTA” in CAP,
receive ACK.
Switch at end of
EPS interval
Contention Free Period
Assigned
Slot
Sender &
Receiver
wake to
beacon,
read null
CTA.
No traffic
Indicated
Beacon
Beacon
EPS Mode
Other Members’ Slots
Slide 13
EPS Mode
Sender: In beacon on last data
packet, “Switch to EPS mode
CTA” in CAP (or CFP) to PNC and
receive ACK. PNC returns to
sending null CTAs at the EPS
Mode rate.
Sender & Receiver wake to
beacon with AWAKE Mode
CTAs set by PNC. Send first
data packet in assigned slot.
High rate AWAKE allocations
shown
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Scenario 2 – Inactive EPS to very low throughput
awake
Sender /Receiver
listen to this
beacon, read null
CTA. No slot
allocated.
Submission
Mode
AWAKE Mode
Sender: Transmits to
PNC “Switch to
AWAKE mode CTA” in
CAP, receives ACK
from PNC. The mode
will switch on next
scheduled superframe
with (null) CTA.
Slide 14
Contention Free Period
Other
Members’
Slots
Assigned
Slot
Beacon
Beacon
Beacon
EPS Mode
EPS
Sender & Receiver
wake to beacon with
AWAKE Mode CTA (with
slot) set by PNC, Send
first data packet in
assigned slot. An
identical-to-EPS-Mode
rate is shown.
Sender: Transmits to
PNC “Switch to EPS
mode CTA” in CAP,
receives ACK. The
mode switches on next
scheduled AWAKE Mode
slot superframe.
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Scenario 3 – Data in EPS to high throughput awake
AWAKE
Sender &
Receiver
wake to
beacon, and
data is sent
in EPS mode
allocated
slots.
Submission
Mode
Sender: transmit to
PNC “Switch to
AWAKE mode CTA”
(Persistent) to PNC in
CAP and receive ACK
from PNC. Switch to
AWAKE allocation at
end of EPS interval
Contention Free Period
Assigned
Slot
Beacon
Beacon
EPS Mode
Other Members’ Slots
Slide 15
EPS Mode
EPS interval
Sender: Send in CAP on last data
packet superframe, “Switch to
EPS mode CTA” and receive
ACK. PNC. This switches the
allocation back to EPS Mode
allocated slots.
Sender & Receiver wake
to beacon. data is sent in
AWAKE Mode allocated
slots
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Scenario 4 – Inactive EPS to Momentary awake
EPS Mode
EPS Mode
Sender /Receiver
listen to this
beacon, read null
CTA. No slot
allocated.
Submission
Beacon
Beacon
EPS interval
Sender & Receiver wake to beacon
with AWAKE Mode CTA set by
PNC. Sender transmits data
packet in assigned slot.
PNC immediately reverts
back to EPS Mode CTA..
Sender: Transmits to PNC
“Switch to AWAKE mode CTA”
in CAP with “Momentary”
parameter and receives ACK
from PNC. The CTA mode will
switch to EPS Mode at the end of
this EPS interval.
Slide 16
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Changes to frame formats
Submission
Slide 17
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
EPS Notification via CTA
1 Octet
Dest. DEV ID
EPS Information
Element
“No-OP” CTA
Information
Element
Information bearing
CTA Information
Element
Submission
1 Octet
1 Octet
1 Octet
2 Octet
SRC DEV
Address
DST DEV
Address
Slot Start Time
Zero Value
1 Octet
1 Octet
2 Octet
2 Octet
SRC DEV
Address
DST DEV
Address
Slot Start Time
Slide 18
2 Octet
Time Slot Duration
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Channel Time Request Additions (Alternative 1)
Existing Channel
Time Request
Submission
CTA Switch
(2 Bits)
AWAKE Mode
Channel Time Request
0
0
EPS Mode
Channel Time Request
0
1
Reserved
1
0
Reserved
1
1
Slide 19
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Channel Time Request Additions (Alternative 2)
Existing Channel
Time Request
Submission
CTA Switch
(1 Bit)
AWAKE Mode
Channel Time Request
0
EPS Mode
Channel Time Request
1
Slide 20
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Management Primitives
• Switch to EPS CTA
– Persistent Only
• Switch to AWAKE CTA
– Persistent
– Momentary
Submission
Slide 21
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Benefits to Additions to PNC and CTA
• Gives PNC the knowledge to communicate
with EPS devices.
• Provides sanity check for EPS receiving
device that it is still in sync
• Facilitates different models of QoS for EPS
devices.
• Utilizes existing CTA mechanisms to support
a wide variety of power save scenarios.
Submission
Slide 22
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Additional Considerations
Submission
Slide 23
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
QoS Aspects for EPS
• Higher order protocols dictate the latency of
the EPS device waking for a beacon
• Higher layers should not ask for more than
needed
• Two profile operation
– Low duty cycle
– High rate operation
Submission
Slide 24
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Repeater Considerations
• Use repeater in normal manner as piconet
coverage enhancer.
Submission
Slide 25
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Superframe Considerations
• Consideration of Beacon change (new superframe
length)
– PNC should not change the superframe length if
not truly beneficial to traffic requirements
– If it does change, the EPS device shall stay on to
find the beacon – if once in a long while event, not
a problem.
• Clock drift calculation and leading of nominal beacon
time is EPS device responsibility.
Submission
Slide 26
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
MAC to PHY Communications
• Taking James Gilb suggestion
• Table of power save options in PHY sent to
MAC. Content is time to return to normal
operation.
• MAC chooses the appropriate table index for
each power down command to PHY.
• MAC sends power on command to return the
PHY to normal mode.
Submission
Slide 27
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Additional CTA thought
• If the sender's CTA in the beacon contained the beacon count of its
next (not current) allocated slot, this could assist with managing the
time with respect to superframes, and help stations who were not in
sync with the sender know when the sender was going to wake up
next.
• If there could be a special CTA that only indicated a sender's next
wake up superframe, it could be broadcast in EVERY beacon as an
indication of the next wakeup superframe. This "information only
CTA" would allow everyone to resync very quickly and easily without
listening for the normal CTA.
Submission
Slide 28
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Performance Modeling
Note: these will be updated in the
next rev, 5.
Submission
Slide 29
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
No-Op Wake Cycle Average Amp Chart
1.00E+00
0.01
0.1
1
1.00E-01
10
no return assumption
1 mS return assumed
1.00E-02
multi superframe return
assumed
always active
1.00E-03
always inactive
1.00E-04
1.00E-05
Submission
Slide 30
Jay Bain Time Domain, Mark Schrader Eastman Kodak
August 2001
doc.: IEEE 802.15-01/315r4
Revision changes
• Changes from R0 to R1
– Add MAC to PHY power management content
– Change EPS sequence from text to diagram
• Changes from R1 to R2
– Add shoulds and shalls to text on beacon length,
QoS,
– Add chart of EPS savings
– Add table of comparison of approaches
• Note that R3 was a distributed but not
presented early version. Content is in R4
• Changes from R2
to R4 Jay Bain Time Domain, Mark Schrader Eastman Kodak
Submission
Slide 31
August 2001
doc.: IEEE 802.15-01/315r4
EPS Information Element Disposition
• Remove EPS gauge level bits. Average power decrease didn’t
weigh well against the increased complexity
• Remove the more bit. Message Header in assigned slot carries
the intent that EPS receiver remains awake after that
superframe
• Remove Current sequence value. Use zero duration CTA
element to reflect the presence or absence of information for the
EPS receive device. Zero duration CTA only present during
superframe for EPS wake.
• Remove the Acknowledged sequence value. The desired effect
is proved by exception handling
• Remove the Active update bit. Define the sending QoS to be
single message or multimessage. (assurance that an errant
sending device doesn’t impact a receiving EPS device)
Submission
Slide 32
Jay Bain Time Domain, Mark Schrader Eastman Kodak