Achievable rates in low-power relay links over fading channels

Xiaodong Cai, Yingwei Yao, Georgios B. Giannakis

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Relayed transmissions enable low-power communications among nodes (possibly separated by a large distance) in wireless networks. Since the capacity of general relay channels is unknown, we investigate the achievable rates of relayed transmissions over fading channels for two transmission schemes: the block Markov coded and the time-division multiplexed (TDM) transmissions. The normalized achievable minimum energy per bit required for reliable communications is derived, which also enables optimal power allocation between the source and the relay. The time-sharing factor in TDM transmissions is optimized to improve achievable rates. The region where relayed transmission can provide a lower minimum energy per bit than direct transmission, as well as the optimal relay placement for these two transmission schemes, are also investigated. Numerical results delineate the advantages of relayed, relative to direct, transmissions.

Original languageEnglish (US)
Pages (from-to)184-194
Number of pages11
JournalIEEE Transactions on Communications
Issue number1
StatePublished - Jan 2005


  • Fading channels
  • Low-power transmissions
  • Minimum energy per bit
  • Relay channels
  • Spectral efficiency

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Computer Networks and Communications


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