System design, DMT analysis, and penalty for non-coherent relaying

S. H. Song, Khaled Letaief

Research output: Contribution to journalArticle

4 Citations (Scopus)


In a two-hop system with multiple amplify-and-forward (AF) relays, the instantaneous channel state information (CSI) is usually required at the relays to achieve a coherent combining at the destination. In this paper, we investigate the design of non-coherent relaying systems, where no CSI is available at the relays. It will be shown that non-coherent relaying can achieve the optimal diversity and multiplexing tradeoff (DMT) of coherent relaying systems with no penalty in the coding length, but incurs a loss of combining gain. To illustrate the practicality of non-coherent relaying, we propose a simple spreading-based non-coherent relaying scheme which achieves the optimal diversity gain. However, the spreading scheme demonstrates a unique non-coherent penalty, namely, the inclusion of one non-coherent relay may introduce "negative" contribution to the receive SNR. To handle this penalty, a distributed relay selection scheme, which can achieve a better outage performance with less energy, is proposed.

Original languageEnglish
Article number6241378
Pages (from-to)2489-2498
Number of pages10
JournalIEEE Transactions on Communications
Issue number9
Publication statusPublished - 2012
Externally publishedYes



  • DMT
  • frequency selective channel
  • MIMO
  • Non-coherent relaying
  • parallel channels

ASJC Scopus subject areas

  • Electrical and Electronic Engineering

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