On spectral efficiency of low-complexity adaptive MIMO systems in rayleigh fading channel

  • Authors:
  • Jinliang Huang;Svante Signell

  • Affiliations:
  • Department of Communication Systems, Royal Institute of Technology, Kista, Sweden;Department of Communication Systems, Royal Institute of Technology, Kista, Sweden

  • Venue:
  • IEEE Transactions on Wireless Communications
  • Year:
  • 2009

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Abstract

Adaptive MQAM modulation is used to maximize spectral efficiency of Multiple-Input Multiple-Output (MIMO) systems while keeping bit error rate (BER) under a target level. Closed-form expressions of the average spectral efficiency, coined as discrete-rate spectral efficiency (DRSE), are derived for adaptive modulation MIMO systems using different algorithms. To further enhance the spectral efficiency, a low complexity adaptation scheme is suggested to switch across different algorithms based on the DRSE. In the current letter, we investigate the adaptation scheme that switches between Orthogonal Space-Time Block Codes (OSTBC) and spatial multiplexing with zero-forcing (ZF) detection for MIMO systems with two transmit antennas. Two types of operating environment are considered: flat Rayleigh fading channel without spatial correlation and spatially correlated Rayleigh fading channel with transmit correlation.