Opportunistic beamforming using dumb antennas

Pramod Viswanath, David N.C. Tse, Rajiv Laroia

Research output: Contribution to journalArticle

Abstract

Multiuser diversity is a form of diversity inherent in a wireless network, provided by independent time-varying channels across the different users. The diversity benefit is exploited by tracking the channel fluctuations of the users and scheduling transmissions to users when their instantaneous channel quality is near the peak. The diversity gain increases with the dynamic range of the fluctuations and is thus limited in environments with little scattering and/or slow fading. In such environments, we propose the use of multiple transmit antennas to induce large and fast channel fluctuations so that multiuser diversity can still be exploited. The scheme can be interpreted as opportunistic beam-forming and we show that true beamforming gains can be achieved when there are sufficient users, even though very limited channel feedback is needed. Furthermore, in a cellular system, the scheme plays an additional role of opportunistic nulling of the interference created on users of adjacent cells. We discuss the design implications of implementing this scheme in a complete wireless system.

Original languageEnglish (US)
Pages (from-to)1277-1294
Number of pages18
JournalIEEE Transactions on Information Theory
Volume48
Issue number6
DOIs
StatePublished - Jun 1 2002

Keywords

  • Multiple antennas
  • Multiuser diversity
  • Scheduling
  • Smart antennas
  • Space-time codes
  • Wireless system design

ASJC Scopus subject areas

  • Information Systems
  • Computer Science Applications
  • Library and Information Sciences

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