Energy Efficient Design of Massive MIMO: How Many Antennas?
02 July 2015
We provide explicit formulas for obtaining the optimal number of service antennas per base station to maximize the cell total energy efficiency of a multi-cell massive MIMO wireless network. Furthermore, we show that equipping the same number of service antennas in each base station results in virtually no loss in energy efficiency due to the flatness of energy efficiency function. Conjugate beamforming pre-coding compares very competitively with zero-forcing pre-coding and in fact, due to the loss in effective array gain and the additional computational cost in zero-forcing, conjugate beamforming can achieve better energy efficiency when per user throughput demand is moderate. In single cell case, we provide explicit algebraic formulas for calculating the optimal number of service antennas and optimal radiated power when a target throughput per user is given.
