Performance of hybrid-ARQ in block-fading channels: a fixed outage probability analysis

  • Authors:
  • Peng Wu;Nihar Jindal

  • Affiliations:
  • Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN;Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN

  • Venue:
  • IEEE Transactions on Communications
  • Year:
  • 2010

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Abstract

This paper studies the performance of hybrid-ARQ (automatic repeat request) in Rayleigh block-fading channels. The long-term average transmitted rate is analyzed in a fastfading scenario where the transmitter only has knowledge of channel statistics, and, consistent with contemporary wireless systems, rate adaptation is performed such that a target outage probability (after a maximum number of H-ARQ rounds) is maintained. H-ARQ allows for early termination once decoding is possible, and thus is a coarse, and implicit, mechanism for rate adaptation to the instantaneous channel quality. Although the rate with H-ARQ is not as large as the ergodic capacity, which is achievable with rate adaptation to the instantaneous channel conditions, even a few rounds of H-ARQ make the gap to ergodic capacity reasonably small for operating points of interest. Furthermore, the rate with H-ARQ provides a significant advantage compared to systems that do not use H-ARQ and only adapt rate based on the channel statistics.