A server repeatedly transmits data items (pages) possibly with different speeds on a set of channels. The objective is to minimize energy consumption of the schedule. We adopt the common model that sending at speed s for t time units consumes t ·s α energy for a constant α ≥ 2. An individual window length is associated with each page. This length is a strict upper bound on the time between two consecutive broadcasts for that page. We present an easy to implement algorithm for the single channel case that obtains an approximation ratio of 3·4 α . For the multi-channel case with identical channels an extension of this algorithm computes an 8 α -approximation. Both algorithms run in low-order polynomial time. As our main tool for the analysis, we show that it suffices to consider periodic schedules as their energy density (total energy consumption per time unit) differs from the one of general schedules at most by (1 + ε) for an arbitrary constant ε> 0.


Optimal Schedule Approximation Ratio Window Length Online Algorithm Feasible Schedule 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2008

Authors and Affiliations

  • Christian Gunia
    • 1
  1. 1.Dept. of Computer ScienceFreiburg UniversityFreiburgGermany

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