Distributed space-time interference alignment with moderately delayed CSIT

Namyoon Lee, Ravi Tandon, Robert W. Heath

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


This paper proposes an interference alignment method with distributed and delayed channel state information at the transmitter (CSIT) for a class of interference networks. The core idea of the proposed method is to align interference signals over time at the unintended receivers in a distributed manner. With the proposed method, achievable tradeoffs between the sum of degrees of freedom (sum-DoF) and feedback delay of CSI are characterized in both the X-channel and three-user interference channel to reveal the impact on how the CSI feedback delay affects the sum-DoF of the interference networks. A major implication of derived results is that distributed and moderately delayed CSIT is useful to strictly improve the sum-DoF over the case of no CSI at the transmitter in a certain class of interference networks. For a class of X-channels, the results show how to optimally use distributed and moderately delayed CSIT to yield the same sum-DoF as instantaneous and global CSIT. Furthermore, leveraging the proposed transmission method and the known outer bound results, the sum-capacity of the two-user X-channel with a particular set of channel coefficients is characterized within a constant number of bits.

Original languageEnglish (US)
Article number6926832
Pages (from-to)1048-1059
Number of pages12
JournalIEEE Transactions on Wireless Communications
Issue number2
StatePublished - Feb 2015
Externally publishedYes


  • delayed CSIT
  • interference networks
  • Space-time interference alignment

ASJC Scopus subject areas

  • Computer Science Applications
  • Electrical and Electronic Engineering
  • Applied Mathematics


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