Distributed optimal beamformers for cognitive radios robust to channel uncertainties

Yu Zhang, Emiliano Dallanese, Georgios B. Giannakis

Research output: Contribution to journalArticle

61 Scopus citations


Through spatial multiplexing and diversity, multi-input multi-output (MIMO) cognitive radio (CR) networks can markedly increase transmission rates and reliability, while controlling the interference inflicted to peer nodes and primary users (PUs) via beamforming. The present paper optimizes the design of transmit-and receive-beamformers for ad hoc CR networks when CR-to-CR channels are known, but CR-to-PU channels cannot be estimated accurately. Capitalizing on a norm-bounded channel uncertainty model, the optimal beamforming design is formulated to minimize the overall mean-square error (MSE) from all data streams, while enforcing protection of the PU system when the CR-to-PU channels are uncertain. Even though the resultant optimization problem is non-convex, algorithms with provable convergence to stationary points are developed by resorting to block coordinate ascent iterations, along with suitable convex approximation techniques. Enticingly, the novel schemes also lend themselves naturally to distributed implementations. Numerical tests are reported to corroborate the analytical findings.

Original languageEnglish (US)
Article number6298975
Pages (from-to)6495-6508
Number of pages14
JournalIEEE Transactions on Signal Processing
Issue number12
StatePublished - 2012


  • Beamforming
  • MIMO wireless networks
  • channel uncertainty
  • cognitive radios
  • distributed algorithms
  • robust optimization

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