1. Improving Client Energy Consumption in 802.16m
Document Number: IEEE S802.16m-09/107r4
Date Submitted:
Source:
N. Himayat, M. Venkatachalam, A. Koc, S. Talwar, H. Yin,
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 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”.
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2. 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.

3. Approaches for Energy Savings (Transmit Mode)
Consider Shannon’s Law for a Point-to-Point Link
Channel Gain
“Error free”
Rate
Linear
relationship between
rate and bandwidth
Exponential
relationship between
rate and power
For fixed rate
Users with good channel conditions can transmit with lower power
Users with higher bandwidth can exponentially reduce power
If delay can be tolerated, tradeoff delay and energy consumption
Network can allocate power & bandwidth and control delay across users to conserve transmit energy

4. Energy-Aware Metrics
Measure Energy Efficiency in terms of “Throughput Per Joule”
Aggregate Metrics Across Multiple Users

5. Client Characteristics are Important
Client circuit power consumption is a “fixed cost” during active mode
Transmit Energy
Overall Energy
Circuit Energy
Optimal Transmission
Need to balance conflicting design guidelines to optimize
Transmit energy: Extend transmission time for as long as possible
Circuit energy: Use highest rate supported and finish transmission quickly

6. Energy Efficiency Performance
Distributed, multi-cellular design (7 cell, flat fading)
Throughput per Joule Performance
Significant energy savings (> 75%) over traditional schemes

7. Interference Reduction Performance
Distributed, multi-cellular design (7 cell, flat fading)
Throughput Performance
Energy-efficient schemes reduce system interference to improve throughput performance

8. 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

9. Recommended SDD Text
Add Section to Section 10.5 on Power Savings
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.