Dynamic symbol allocation for spectral and energy efficient millimetre wave multi-antenna systems

In this Letter, the authors investigate the relationship between a number of parallel transmit symbols and the spectral efficiency of a millimetre wave (downlink) massive MIMO system with multiple antenna array sizes and a hybrid beamforming strategy. The proposed approach determines the optimal number of parallel data symbols that maximises both spectral efficiency and energy efficiency. A heuristic algorithm is proposed that adapts the number of symbols at the transmitter based on the instantaneous channel state information. The proposed algorithm outperforms non-adaptive strategies for multiple array sizes and achieves a significant improvement in spectral and energy efficiency.