Outage exponent: A unified performance metric for parallel fading channels

Bo Bai, Wei Chen, Khaled B. Letaief, Zhigang Cao

Research output: Contribution to journalArticle

14 Citations (Scopus)


The parallel fading channel, which consists of finite number of subchannels, is very important, because it can be used to formulate many practical communication systems. The outage probability, on the other hand, is widely used to analyze the relationship among the communication efficiency, reliability, signal-to-noise ratio (SNR), and channel fading. To the best of our knowledge, the previous works only studied the asymptotic outage performance of the parallel fading channels which are only valid for a large number of subchannels or high SNRs. In this paper, a unified performance metric, which we shall refer to as the outage exponent, will be proposed. Our approach is mainly based on the large deviations theory and Meijer's $G$-function. It is shown that the proposed outage exponent is not only an accurate estimation of the outage probability for any number of subchannels, any SNR, and any target transmission rate, but also provides an easy way to compute the outage capacity, finite-SNR diversity-multiplexing tradeoff, and SNR gain. The asymptotic performance metrics, such as the delay-limited capacity, ergodic capacity, and diversity-multiplexing tradeoff can be directly obtained by letting the number of subchannels or SNR tend to infinity. Similar to Gallager's error exponent, a reliable function for parallel fading channels, which illustrates a fundamental relationship between the transmission reliability and efficiency, can also be defined from the outage exponent. Therefore, the proposed outage exponent provides a complete and comprehensive performance measure for parallel fading channels.

Original languageEnglish
Article number6353210
Pages (from-to)1657-1677
Number of pages21
JournalIEEE Transactions on Information Theory
Issue number3
Publication statusPublished - 20 Feb 2013



  • Channel capacity
  • Meijer's $G$-function
  • diversity-multiplexing tradeoff
  • large deviations theory
  • outage exponent
  • parallel fading channel

ASJC Scopus subject areas

  • Information Systems
  • Computer Science Applications
  • Library and Information Sciences

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