Pilot Power Control for Cell-free Massive MIMO

Trang C. Mai, Hien Quoc Ngo, Malcolm Egan, Trung Q. Duong

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)
365 Downloads (Pure)


In this correspondence paper, we consider a cell-free massive Multiple-Input Multiple-Output (MIMO) system where access points (APs) serve a much smaller number of users under the time-division duplex operation. The APs first estimate the channels via the uplink training phase. Then, these channel estimates are used to detect desired symbols in the uplink and precode the transmit symbols in the downlink. Nonorthogonality of pilot sequences and AP selection (e.g., received-power-based selection or largest-large-scale-fading based selection schemes) are taken into account. To reduce the effect of pilot contamination, we propose a pilot power control design, which chooses the pilot power control coefficients to minimize the mean-squared error of the channel estimation. This is achieved via the sequential convex approximation method. By using pilot power control in training phase, the system performance is considerably improved. In addition, we derive closed-form expressions for the uplink and downlink achievable rates with arbitrary power data/pilot control coefficients and any AP selection schemes.

Original languageEnglish
Pages (from-to)11264 - 11268
JournalIEEE Transactions on Vehicular Technology
Issue number11
Early online date29 Aug 2018
Publication statusPublished - Nov 2018


  • Cell-free massive MIMO
  • Channel estimation
  • channel estimation
  • Data communication
  • Downlink
  • MIMO communication
  • pilot power control
  • Power control
  • Training
  • Uplink

ASJC Scopus subject areas

  • Automotive Engineering
  • Aerospace Engineering
  • Computer Networks and Communications
  • Electrical and Electronic Engineering


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