1 research outputs found
A multi-user linear equalizer for uplink broadband millimeter wave massive MIMO
Most previous work on hybrid beamforming millimeter wave (mmWave) communications and massive
multiple input multiple output (MIMO) systems focused on narrowband channels. However, it is expected
that the mmWave channels will be wideband, and for that reason, it is important to design solutions for
frequency-selective channels. Therefore, in this paper, we consider the design of a hybrid analog/digital
multiuser linear equalizer for broadband mmWave massive MIMO systems, optimized using the bit error
rate (BER) as a metric. For the digital part, a closed-form solution is obtained by showing that the
minimum mean square error (MMSE) and minimum BER solutions are identical. The analog part, which is
assumed to be the same for all subcarriers, is computed iteratively over the radio frequency (RF) chains,
and it is shown that the solution obtained in a previous iteration may be updated inexpensively to obtain
a solution for the current iteration. The simulation results show that the performance gap between the
proposed hybrid broadband multiuser equalizer and full digital equalizer decreases monotonically and
exponentially with the number of RF chains until reaching zero. Moreover, the gap decay rate is faster
for sparser mmWave channels, where fewer RF chains are required to achieve the same performance of
the full digital architecture.publishe