Threshold-based relaying in coded cooperative networks

Ghaleb Al-Habian, Ali Ghrayeb, Mazen Hasna, Adnan Abu-Dayya

Research output: Contribution to journalArticle

52 Citations (Scopus)


In cooperative communications, error propagation at the relay nodes degrades the diversity order of the system. To combat that effect, we present a novel technique to control error propagation at the relays, which is implemented in the context of a distributed turbo code. In the presented technique, the relay calculates the log-likelihood ratio (LLR) values for the bits sent from the source. These values are subjected to a threshold to distinguish the reliable bits from the unreliable bits. The relay then forwards the bits that are deemed reliable and discards the bits that are not, resulting in fewer errors propagating to the destination. The assumption here is that the destination does not know the location of the discarded bits. We develop upper bounds on the end-to-end bit error rate, enabling us to optimize the threshold in terms of the minimum end-to-end bit error rate. We compare our technique with existing techniques that have been proposed to control error propagation, including using only a cyclic redundancy code check at the relay, forwarding analog LLR values, and by employing no error control at the relay at all. We demonstrate, through several numerical examples, that the proposed scheme outperforms all existing schemes.

Original languageEnglish
Article number5605270
Pages (from-to)123-135
Number of pages13
JournalIEEE Transactions on Vehicular Technology
Issue number1
Publication statusPublished - Jan 2011
Externally publishedYes



  • Concatenated coding
  • cooperative systems
  • diversity methods
  • error propagation
  • relaying strategies
  • reliability estimation
  • virtual multiple-input-multiple-output (MIMO)

ASJC Scopus subject areas

  • Automotive Engineering
  • Aerospace Engineering
  • Computer Networks and Communications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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