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Improving Client Energy Consumption in 802.16m
Document Number: IEEE S802.16m-09/107r4
Date Submitted:2009-01-05
Source: N. Himayat, M. Venkatachalam, A. Koc, S. Talwar, H. Yin, Email: [email protected] S. Ahmadi, M. Ho, Intel Corporation G. Miao, Ye (Geoffrey) Li, Georgia Tech. H. Kim, U. T. Austin Pei-Kai Liao, Yih-Sheng Chen and Paul Cheng, MediaTek Inc. Zheng Yan-Xiu, Ming Bing Chen, Richard Li, ITRI
Venue: Interim IEEE 802.16 Session #59 , La Jolla, CA, USA
Base Contribution:IEEE C80216m-09_0107r4.doc
Purpose:In support of contribution IEEE C80216m-09_0107r4.doc, regarding SDD modification to add Section 10.5 on “Power savings in active connected mode”.
Notice:This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained herein.
Release:The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that
this contribution may be made public by IEEE 802.16.
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Background
• Energy efficiency is critical for mobile communications due to limited improvements in battery technology and increasing demands of “any-time, anywhere” multimedia communication.
• 802.16m SRD and SDD include support for power management schemes, but mostly focused on sleep and idle modes.
• Contribution highlights network based techniques for improving energy savings at the mobile client during “active connected” mode.
• Demonstrates significant energy savings for “transmit mode,” as well as interference reduction capabilities.
• Proposes SDD text to include support for power management techniques in the “active connected” mode as well.
Approaches for Energy Savings (Transmit Mode)
Noise
PGBWC iTXi
ii,1log
“Error free” Rate
Exponential relationship between
rate and power
Linear relationship between rate and bandwidth
Channel Gain
Consider Shannon’s Law for a Point-to-Point Link
For fixed rate
•Users with good channelchannel conditions can transmit with lower power
•Users with higher bandwidth bandwidth can exponentially reduce power
If delaydelay can be tolerated, tradeoff delay and energy consumption
Network can allocate power & bandwidth and control delay across users to conserve transmit energy
Energy-Aware Metrics
Measure Energy Efficiency in terms of “Throughput Per Joule”
)/()(
)( JoulebitsRPP
RRU
TC
Aggregate Metrics Across Multiple Users
)(1
1
RUN
N
ii
N
i
N
ii RU
/1
1
)(
Client Characteristics are Important
Client circuit power consumption is a “fixed cost” during active mode
Need to balance conflicting design guidelinesconflicting design guidelines to optimize
•Transmit energy: Extend transmission time for as long as possible
• Circuit energy: Use highest rate supported and finish transmission quickly
Transmit Energy
Overall Energy
Circuit Energy
Optimal Transmission
Energy Efficiency Performance
1 3 5 7 9 11 130
2
4
6
8
10
12
Number of active users in each cell
En
erg
y e
ffic
ien
cy (
Mb
its/J
ou
le)
Energy Efficiency (Througput per Joule)
Trad-33dBm (single-cell)
Trad-15dBm
Trad-33dBm
Trad-25dBm
Prop-EE
Opt-EE
Opt-EE (single cell)
Significant energy savings (> 75%) over traditional schemes
Throughput per Joule Performance
Distributed, multi-cellular design (7 cell, flat fading)
Interference Reduction Performance
1 3 5 7 9 11 130
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Number of active users in each cell
Th
rou
gh
pu
t (M
bit
s/s)
Throughput
Trad-25dBm
Opt-EE
Trad-33dBm (single cell)
Opt-EE (single cell)
Prop-EE
Trad-33dBm
Trad-15dBm
Distributed, multi-cellular design (7 cell, flat fading)
Throughput Performance
Energy-efficient schemes reduce system interference to improve throughput performance
Required Standards Support
• Minimal Standard Support Required
• Base station requires client power profile and power savings preference for selecting optimal transmission parameters
• Information can be communicated upon initialization and/or via slow periodic updates through suitably defined MAC management messages
• Example information
– A user’s power consumption profile (circuit power, idle power etc.)
– User’s preferred power savings mode (“on”, “off”, “intermediate”)
– User’s remaining battery level
Recommended SDD Text Add Section 10.5.3 to Section 10.5 on Power Savings
10.5.3 Power Management for the Connected Mode
Enhanced power savings when the MS is in connected mode and is actively transmitting to the network may be supported. In this mode, the base station optimizes resources and transmission parameters to optimize energy savings at the MS. A power aware metric may be used for such optimization. An example power aware metric is the “Bits per Joule” metric.
For active mode energy optimization, base station must have information related to a user’s power consumption profile, as well as user’s preference for energy saving mode. Such information may be made known to the base station upon terminal provisioning and initialization, as well as through slow updates using suitably defined MAC management messages. The details of the information as well as the exact format and communication of these messages are FFS.
