Blind null-space learning for MIMO underlay cognitive radio with primary user interference adaptation

Yair Noam, Andrea J. Goldsmith

Research output: Contribution to journalArticlepeer-review


This paper proposes a blind technique that enables a MIMO cognitive radio Secondary User (SU) to transmit in the same band simultaneously with a Primary User (PU) by utilizing separate spatial dimensions than the PU. Specifically, the SU transmits in the null space of the interference channel to the PU. The SU learns this null space without burdening the PU with any knowledge or explicit cooperation with the SU. The only condition required is that during the learning period, the SU is allowed to inflict «non-harmful» interference to the PU. The SU measures a monotonic function of this interference in order to learn the null space. Specifically, during the learning interval, the SU learns the null space by iteratively modifying the spatial orientation of its transmitted signal and measures the effect of this modification on the monotonic function that it observes. We provide simulation results demonstrating that the algorithm converges rapidly and is robust to quantization noise and other sources of interference.

Original languageEnglish
Article number6463494
Pages (from-to)1722-1734
Number of pages13
JournalIEEE Transactions on Wireless Communications
Issue number4
StatePublished - 2013
Externally publishedYes


  • MIMO
  • Underlay cognitive radio
  • blind
  • cognitive radio (CR)
  • interference constraint
  • interference suppression
  • learning
  • null space
  • opportunistic spectrum sharing
  • spatial multiplexing

All Science Journal Classification (ASJC) codes

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


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