MIMO downlink scheduling with non-perfect channel state knowledge

  • Authors:
  • Hooman Shirani-Mehr;Giuseppe Caire;Michael J. Neely

  • Affiliations:
  • Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, CA;Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, CA;Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, CA

  • Venue:
  • IEEE Transactions on Communications
  • Year:
  • 2010

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Abstract

Downlink scheduling schemes are well-known and widely investigated under the assumption that the channel state is perfectly known to the scheduler. In the multiuser MIMO (broadcast) case, downlink scheduling in the presence of nonperfect channel state information (CSI) is only scantly treated. In this paper we provide a general framework that addresses the problem systematically. Also, we illuminate the key role played by the channel state prediction error: our scheme treats in a fundamentally different way users with small channel prediction error ("predictable" users) and users with large channel prediction error ("non-predictable" users), and can be interpreted as a near-optimal opportunistic time-sharing strategy between MIMO downlink beamforming to predictable users and space-time coding to non-predictable users. Our results, based on a realistic MIMO channel model used in 3GPP standardization, show that the proposed algorithms can significantly outperform a conventional "mismatched" scheduling scheme that treats the available CSI as if it was perfect.