Downlink Beamforming for Energy-Efficient Heterogeneous Networks with Massive MIMO and Small Cells

Long D. Nguyen, Hoang Duong Tuan, Trung Q. Duong, Octavia A. Dobre, H. Vincent Poor

Research output: Contribution to journalArticlepeer-review

57 Scopus citations


A heterogeneous network (HetNet) of a macrocell base station equipped with a large-scale massive multi-in multi-out (MIMO) antenna array overlaying a number of small cell base stations (small cells) can provide high quality of service (QoS) to multiple users under low transmit power budget. However, the circuit power for operating such a network, which is proportional to the number of transmit antennas, poses a problem in terms of its energy efficiency (EE). This paper addresses the beamforming design at the base stations to optimize the network EE under the QoS constraints and a transmit power budget. Beamforming tailored for weak, strong, and medium cross-tier interference HetNets is proposed. In contrast to the conventional transmit strategy for power efficiency in meeting the users' QoS requirements, which suggest the use of a few hundred antennas, it is found out that the overall network EE quickly drops if this number exceeds 50. It is found that, for a given number of antennas, HetNet is more energy efficient than massive MIMO when considering the overall energy consumption.

Original languageEnglish (US)
Pages (from-to)3386-3400
Number of pages15
JournalIEEE Transactions on Wireless Communications
Issue number5
StatePublished - May 2018
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Computer Science Applications
  • Electrical and Electronic Engineering
  • Applied Mathematics


  • Heterogeneous networks
  • beamformer design
  • energy efficiency
  • massive MIMO
  • optimization
  • small cell


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