Transmit diversity versus opportunistic beamforming in data packet mobile downlink transmission

Mari Kobayashi, Giuseppe Caire, David Gesbert

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

We compare spacetime coding (transmit diversity) and random "opportunistic " beamforming in a space-division multiple access/time-division multiple access single-cell downlink system with random packet arrivals, correlated block-fading channels, and non-perfect channel state information at the transmitter due to a feedback delay. Our comparison is based on system stability. The ability of accurately predicting the channel signal-to-noise ratio dominates the performance of opportunistic beamforming, even under the optimistic assumption that the sequence of beamforming matrices is perfectly known a priori by the receivers. Our results show that the relative merit of opportunistic beamforming versus spacetime coding strongly depends on the channel Doppler bandwidth. Therefore, previous naive conclusions on the fact that transmit diversity always hurts the system performance under multiuser-diversity scheduling should be taken with great care.

Original languageEnglish
Pages (from-to)151-157
Number of pages7
JournalIEEE Transactions on Communications
Volume55
Issue number1
DOIs
StatePublished - Jan 2007
Externally publishedYes

Keywords

  • Non-perfect channel state information at the transmitter (CSIT)
  • Opportunistic beamforming
  • Space-time coding (STC)
  • Stability

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