Leveraging dynamic spare capacity in wireless systems to conserve mobile terminals' energy

  • Authors:

  • Hongseok Kim;Gustavo De Veciana

  • Affiliations:

  • Department of Electrical Engineering, Princeton University, Princeton, NJ and Department of Electrical and Computer Engineering, University of Texas at Austin, Austin, TX;Department of Electrical and Computer Engineering, University of Texas at Austin, Austin, TX

  • Venue:
  • IEEE/ACM Transactions on Networking (TON)
  • Year:
  • 2010

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Abstract

In this paper, we study several ways in which mobile terminals can backoff on their uplink transmit power in order to extend battery lifetimes. This is particularly effective when a wireless system is underloaded as the degradation in user's perceived quality of service can be negligible. The challenge, however, is developing a mechanism that achieves a good tradeoff among transmit power, idling/circuit power, and the performance customers will see. We consider systems with flow-level dynamics supporting either real-time or best effort (e.g., file transfers) sessions. The energy-optimal transmission strategy for real-time sessions is determined by solving a convex optimization. An iterative approach exhibiting superlinear convergence achieves substantial amount energy savings, e.g., more than 50% when the session blocking probability is 0.1% or less. The case of file transfers is more subtle because power backoff changes the system dynamics. We study energy-efficient transmission strategies that realize energy-delay tradeoff. The proposed mechanism achieves a 35%-75% in energy savings depending on the load and file transfer target throughput. A key insight, relative to previous work focusing on static scenarios, is that idling power has a significant impact on energy-efficiency, while circuit power has limited impact as the load increases.