# Bit-Interleaved Coded Multiple Beamforming in Millimeter-Wave Massive MIMO Systems

## TL;DR

This paper analyzes the asymptotic diversity gain of millimeter-wave massive MIMO systems using bit interleaved coded multiple beamforming, demonstrating how increasing RAUs enhances diversity and multiplexing capabilities.

## Contribution

The paper provides a theorem for the diversity gain in mmWave MIMO systems employing BICMB with large antenna arrays, highlighting the impact of RAU count on system performance.

## Key findings

- Distributed BICMB achieves full spatial multiplexing and diversity.
- Diversity gain increases with the number of RAUs.
- Simulation confirms increased diversity with perfect CSI.

## Abstract

In this paper we carry out the asymptotic diversity analysis for millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) systems by using bit interleaved coded multiple beamforming (BICMB). First, a single-user mmWave system which employs $M_t$ antenna subarrays at the transmitter and $M_r$ antenna subarrays at the receiver is studied. Each antenna subarray in the transmitter and the receiver has $N_r$ and $N_t$ antennas, respectively. We establish a theorem for the diversity gain when the number of antennas in each remote antenna unit (RAU) goes to infinity. Based on the theorem, the distributed system with BICMB achieves full spatial multiplexing of $L_t=\sum_{i,j}L_{ij}$ and full spatial diversity of $\frac{\left(\sum_{i,j}\beta_{ij}\right)^2}{\sum_{i,j}\beta_{ij}^2L_{ij}^{-1}}$ where $L_{ij}$ is the number of propagation paths and $\beta_{ij}$ is the large scale fading coefficient between the $i$th RAU in the transmitter and the $j$th RAU in the receiver. This result shows that one can increase the diversity gain in the system by increasing the number of RAUs. Simulation results show that, when the perfect channel state information assumption is satisfied, the use of BICMB increases the diversity gain in the system.