1. 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: nageen.himayat@intel.com 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. Patent Policy: The contributor is familiar with the IEEE-SA Patent Policy and Procedures: and.http://standards.ieee.org/guides/bylaws/sect6-7.html#6http://standards.ieee.org/guides/opman/sect6.html#6.3 Further information is located at and.http://standards.ieee.org/board/pat/pat-material.htmlhttp://standards.ieee.org/board/pat

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) “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 channelUsers with good channel conditions can transmit with lower power bandwidthUsers with higher bandwidth can exponentially reduce power delay 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 conflicting design guidelines 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 Transmit Energy Overall Energy Circuit Energy Optimal Transmission

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

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 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.