Optimality of zero-forcing beamforming with multiuser diversity

Taesang Yoo, Andrea Goldsmith

Research output: Contribution to journalConference articlepeer-review

169 Scopus citations


In MIMO downlink channels, the capacity is achieved by dirty paper coding (DPC). However, DPC is difficult to implement in practical systems. This work investigates if, for a large number of users, simpler schemes can achieve the same performance. Specifically, we show that a zero-forcing beamforming (ZFBF) strategy, while generally suboptimal, can achieve the same asymptotic sum-rate capacity as that of DPC, as the number of users goes to infinity. In proving this asymptotic result, we propose an algorithm for determining which users should be active in ZFBF transmission. These users are semi-orthogonal to one another, and when fairness among users is required, can be grouped for simultaneous transmissions to enhance the throughput of fair schedulers. We provide numerical results to confirm the optimality of ZFBF and to compare its performance with that of various MIMO downlink strategies.

Original languageEnglish (US)
Article numberCT07-3
Pages (from-to)542-546
Number of pages5
JournalIEEE International Conference on Communications
StatePublished - 2005
Externally publishedYes
Event2005 IEEE International Conference on Communications, ICC 2005 - Seoul, Korea, Republic of
Duration: May 16 2005May 20 2005

All Science Journal Classification (ASJC) codes

  • Computer Networks and Communications
  • Electrical and Electronic Engineering


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