MIMO communications in ad hoc networks

Biao Chen, Michael J. Gans

Research output: Contribution to journalArticlepeer-review

86 Scopus citations


We study in this paper the network spectral efficiency of a multiple-input multiple-output (MIMO) ad hoc network with K simultaneous communicating transmitter-receiver pairs. Assuming that each transmitter is equipped with t antennas and each receiver with r antennas and each receiver implements single-user detection, we show that in the absence of channel state information (CSI) at the transmitters, the asymptotic network spectral efficiency is limited by r nats/s/Hz as K → ∞ and is independent of t and the transmit power. With CSI corresponding to the intended receiver available at the transmitter, we demonstrate that the asymptotic spectral efficiency is at least t + r + 2√tr nats/s/Hz. Asymptotically optimum signaling is also derived under the same CSI assumption, i.e., each transmitter knows the channel corresponding to its desired receiver only. Further capacity improvement is possible with stronger CSI assumption; we demonstrate this using a heuristic interference suppression transmit beamforming approach. The conventional orthogonal transmission approach is also analyzed. In particular, we show that with idealized medium access control, the channelized transmission has unbounded asymptotic spectral efficiency under the constant per-user power constraint. The impact of different power constraints on the asymptotic spectral efficiency is also carefully examined. Finally, numerical examples are given that confirm our analysis.

Original languageEnglish (US)
Pages (from-to)2773-2783
Number of pages11
JournalIEEE Transactions on Signal Processing
Issue number7
StatePublished - Jul 2006


  • Ad hoc networks
  • Multiple-input multiple-output (MIMO) communications
  • Spectral efficiency

ASJC Scopus subject areas

  • Signal Processing
  • Electrical and Electronic Engineering


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