Adaptive MIMO transmission for exploiting the capacity of spatially correlated channels

Antonio Forenza*, Matthew R. McKay, Ashish Pandharipande, Robert W. Heath, Iain B. Collings

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

115 Citations (Scopus)


We consider a novel low-complexity adaptive multiple-input multiple-output (MIMO) transmission technique. The approach is based on switching between low-complexity transmission schemes, including statistical beamforming, double space-time transmit diversity, and spatial multiplexing, depending on the changing channel statistics, as a practical means of approaching the spatially correlated MIMO channel capacity. We first derive new ergodic capacity expressions for each MIMO transmission scheme in spatially correlated channels. Based on these results, we demonstrate that adaptive switching between MIMO schemes yields significant capacity gains over fixed transmission schemes. We also derive accurate analytical approximations for the optimal signal-to-noise-ratio switching thresholds, which correspond to the crossing-points of the capacity curves. These thresholds are shown to vary, depending on the spatial correlation, and are used to identify key switching parameters. Finally, we propose a practical switching algorithm that is shown to yield significant spectral efficiency improvements over nonadaptive schemes for typical channel scenarios.

Original languageEnglish
Pages (from-to)619-630
Number of pages12
JournalIEEE Transactions on Vehicular Technology
Issue number2
Publication statusPublished - Mar 2007
Externally publishedYes


  • Adaptive modulation
  • Channel capacity
  • Channel coding
  • Fading channels
  • MIMO systems


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