Capacity of time-varying channels with causal channel side information

Andrea J. Goldsmith, Muriel Médard

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


We derive the capacity of time-varying channels with memory that have causal channel side information (CSI) at the sender and receiver. We obtain capacity of block-memoryless and asymptotically block-memoryless channels with block-memoryless or weakly decorrelating side information. Our coding theorems rely on causal generation of the codewords relative to the causal transmitter CSI. The CSI need not be perfect, and we consider the case where the transmitter and receiver have the same causal CSI as well as the case where the transmitter CSI is a deterministic function of the receiver CSI. For block-memoryless and asymptotically block-memoryless channels, our coding strategy averages mutual information density over multiple transmission blocks to achieve the maximum average mutual information. We apply the coding theorem associated with the block-memoryless channel to determine the capacity and optimal input distribution of intersymbol interference (ISI) time-varying channels with causal perfect CSI about the time-varying channel. The capacity of this channel cannot be found through traditional decomposition methods.

Original languageEnglish (US)
Pages (from-to)881-899
Number of pages19
JournalIEEE Transactions on Information Theory
Issue number3
StatePublished - Mar 2007
Externally publishedYes

All Science Journal Classification (ASJC) codes

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


  • Capacity
  • Causal channel side information (CSI)
  • Intersymbol interference (ISI)
  • Time-varying channels


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