Sleep Mode Considerations for a Device-Based Power Saving
Document Number: S80216m-08_580
Date Submitted: 2008-07-07
Source:
Mamadou Kone
Ming-Hung Tao
Ying-Chuan Hsiao
Richard Li
ITRI.
E-mail:
970031@itri.org.tw, makone@gmail.com
E-mail:
richard929@itri.org.tw
Venue:
Session #56
Denver, USA
Base Contribution:
IEEE C80216m-08_580r1
Purpose:
For discussion and adoption by IEEE 802.16m group
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Approach


1.
Actual design of power saving mode has lots of complexities and signaling
overheads making inefficient the power saving for a device.
Two important performance factors have to be considered for MS operating in
sleep mode:
MS power consumption

2.
Depend on the number of Power Saving Class (PSC) and their design
Signaling load generated by MS in sleep mode

Traffic indications, deactivation and handoffs signals from the network
Traffic indication
Positive Traffic indication
Receive signal from BS
to reactivate PSC1
DL/ UL data burst
Deactivation of PSC type 3
Availability interval
Unavailability interval
The PSC type 2 could be still running, but
the device power saving is interrupted.
PSC type 2 – listening window of constant size and sleep window of constant size
PSC type 1 – listening window of constant size and doubling sleep window
Device mode – Unavailability interval - period of inactivity of the device
Type 1 connections : BE, NRT-VR; Type 2 connections : RTVR, UGS, ERTVR
Type 3 connections : Multicast, Periodic ranging, Management messages
Sleep mode issues

Common issues from 802.16e:



PSC type 2 issues


Fix listening window : May be too long or too short to cover different cases
of traffic behaviors (HARQ operations, etc).
PSC type 1 issues:




Three kinds of PSC: Overlapping of listening and sleep windows may extend
power consumption.
Possibly several PSCs within same type of connection: Overlapping issue to
get the device sleep interval.
Signaling load: MOB_TRF_IND (traffic indication) at every listen window
and signals for deactivation / reactivation of the power saving.
Reactivation of the power saving with Initial sleep window no matter the
length of the sleep window before deactivation.
No influence of the doubling sleep window on device sleep interval when
coupled with PSC type 2.
PSC type 3 issues


Lack of listen window: signaling for reactivation of the power saving
No influence of long sleep window on device sleep interval when coupled
with PSC type 2 or type 1.
Enhancement within same type of connections

For same type of connections: Integrate all the connections into a unique power
saving class to represent their traffics pattern.

Only type 1 connections
Data/positive traffic indication
received before timer ends
Traffic timer ends, no
data burst received
Data burst timer
reached, MS sleeps



Super frame header
Timer not expired, incoming data
Initial sleep longer

Use of traffic timer to monitor data
burst or positive traffic indication
Use of data burst timer to monitor
data burst ending
Match the start of every listening
window with a super frame header
Use a HARQ timer for data recovery
After incoming data, new Initsleep=
multiple of Initial sleep < last sleep.
Only type 2 connections
Default listen
window
HARQ traffic timer expires
for each reception
Sleep window


HARQ traffic timer expires
for each reception
HARQ traffic timer stopped
because of erroneous data
The listening window is
extended to recover the data

Only type 3 connections
Signal to sleep and/or
for next wakeup time
Type 3 operations


Timers not expired still data
Default listen window to carry out
normal operations of DL and UL
based on no error of transmission
Use HARQ traffic timer or data
recovery and listening window may
cover the next sleep length
Define default listen and timers(multicast,
periodic ranging) are used to increase its
length when needed.
The default listen window size could be a
multiple of the longest timer used.
Signaling to trigger MS sleep and/or decide
for the next data time otherwise default
length of inactivity used after timers expire.
Merging connections into a unique PSC

Combine in each case two different types of connection in a unique Power saving
class
Type 2 and type 1 connections
Data burst / positive traffic
indication for type 1 traffics
Work as PSC type 2 connections
only, because no data burst

Data burst timer expires

Traffic timer starts and ends
no data burst received

Type 2 and type 3 connections
Remaining Sleep window
Listen matches with type 3
connections data reception
predicted type 3 inactive time matches with listen

timers expire or signal
for next wakeup time
Type 1 and type 3 connections
Receiving type 3 data

Positive traffic indication
for type 1 traffics

Predicted type 3 inactive time is
ok for type 1 traffics buffering
Traffic timer didnt expire
Data burst timer expires
Signal for next
wake up time
Use type 2 connections to
design the unique PSC
With type 1 connection use: all
timers from different types as
previously defined.
With type 3 connections use
the predictive sleep period to
define the scenarios of listen
and sleep
Listen window extensible with
timers to support operations
Use the length of the type 3
connection inactive time as the
default sleep window (matching
with BS buffer for type 1 data)
Integrate the timers/signals from
type 1 and type 3 connections
during listening window to either
continue to receive data or sleep
Toward the design of a unique PSC



Integrate type 1 connection to the merging of type 2 and type 3 to define
only a unique Power Saving Class
Type 1 connections data burst opportunity can be offered during every n
default listening period.
Apply all the timers and signals already define from all types of
connections and also the possible listening window flexibility.
Here n= every 2 listening window
Listening matches with type 3
connections data reception
2nd opportunity: traffic indication
positive for type 1 traffics
sleep window reduced by
listening extension length
Predicted type 3 inactive time matches with default listen
1st opportunity for type 1 traffic,
but no burst, so works as PSC 2
Listening extended
Signal to stop data sending for type
3 and define next wake up time
Data burst timer ends
A unique power saving class representing all traffic patterns
Power saving periods
Active
Inactive
Illustration of the device power saving from the unique PSC
Dynamic Update of the unique PSC

In case of update within the same type of connection, apply the update to listening and
sleep windows definition.



Applied the change to the next sleep when decreasing the sleep length
Can apply the change to a later sleep period when increasing the sleep length
In case of update or complete deletion of one type of connection included in the
unique PSC design.


Update the unique Power saving class based on the remaining types of connection.
Signaling to decide for the effective start of the new definition if needed.
New parameters applied
type 3 connections
data reception
traffic indication
Signal for for type 1 traffics
predicted type 3 inactive time next wakeup
type 3 connections
data reception
Exchange new windows
definition for 2nd sleep
Signal for next
wakeup time
…
……
1st opportunity for data burst, but
traffic timer expires, works as PSC 2
No traffic indication/ data burst
Type 1 connection
deletion indication
type 3 connections
data reception
Signal for next
wakeup time
type 3 connections
data reception
Type 2 connection
deletion indication
Signal for next
wakeup time
Next predicted inactive time
…
No traffic indication/data burst
Define or not new windows
size for next sleep
No more traffic timer, works with
type 3 connections only
New parameters are applied
type 3 connections
data reception
Signal for next
wakeup time
1st new opportunity: traffic
indication positive
3. Proposed text for SDD
[Insert the following into sleep section of [2]]
--------------------------------------- Text start --------------------------------------------X.x.x Sleep mode



Sleep mode operation uses connection behaviors to design a unique device-based power
saving framework.
A mechanism for adaptively adjusting sleep patterns (i.e. duration of sleep and listening
windows) based on traffic pattern without deactivating the sleep mode should be provided.
This unique power saving framework uses efficient timers with less signaling that enables
maximum MS power saving and reduces the air-link resource usage associated with sleep
mode signaling.
--------------------------------------- Text end -----------------------------------------------
References
[1] IEEE Std. 802.16e-2005, IEEE Standard for Local and metropolitan area networks, Part 16:
Air Interface for Fixed and Mobile Broadband Wireless Access Systems, Amendment 2:
Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in
Licensed Bands, and P802.16Rev2/D3 (February 2008).
[2] IEEE 802.16m-08/003r1, “The Draft IEEE 802.16m System Description Document”