Energy and Spectral Efficiency of Very Large Multiuser MIMO Systems

Hien Quoc Ngo, Erik G. Larsson, Thomas L. Marzetta

Research output: Contribution to journalArticlepeer-review

2164 Citations (Scopus)


A multiplicity of autonomous terminals simultaneously transmits data streams to a compact array of antennas. The array uses imperfect channel-state information derived from transmitted pilots to extract the individual data streams. The power radiated by the terminals can be made inversely proportional to the square-root of the number of base station antennas with no reduction in performance. In contrast if perfect channel-state information were available the power could be made inversely proportional to the number of antennas. Lower capacity bounds for maximum-ratio combining (MRC), zero-forcing (ZF) and minimum mean-square error (MMSE) detection are derived. An MRC receiver normally performs worse than ZF and MMSE. However as power levels are reduced, the cross-talk introduced by the inferior maximum-ratio receiver eventually falls below the noise level and this simple receiver becomes a viable option. The tradeoff between the energy efficiency (as measured in bits/J) and spectral efficiency (as measured in bits/channel use/terminal) is quantified for a channel model that includes small-scale fading but not large-scale fading. It is shown that the use of moderately large antenna arrays can improve the spectral and energy efficiency with orders of magnitude compared to a single-antenna system.
Original languageEnglish
Pages (from-to)1436-1449
Number of pages14
JournalIEEE Transactions on Communications
Issue number4
Early online date07 Feb 2013
Publication statusPublished - Apr 2013


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