# Generalized Spatial Modulation Aided MmWave MIMO with Sub-Connected Hybrid Precoding Scheme

## TL;DR

This paper proposes a generalized spatial modulation scheme for mmWave MIMO systems that enhances spectral efficiency without additional RF chains, using a hybrid precoding design optimized through a two-step algorithm.

## Contribution

A novel GenSM aided mmWave MIMO system that transmits extra data via antenna group indices without extra RF chains and an optimized hybrid precoding algorithm.

## Key findings

- Achieves higher spectral efficiency compared to traditional schemes.
- Demonstrates the effectiveness of the proposed hybrid precoding in simulations.
- Provides a practical solution for cost-effective mmWave MIMO systems.

## Abstract

Due to the high cost and low energy efficiency of the dedicated radio frequency (RF) chains, the number of RF chains in a millimeter wave (mmWave) multiple-input multiple-output (MIMO) system is usually limited from a practical point of view. In this case, the maximum number of independent data streams is also restricted by the number of RF chains, which consequently leads to limiting the potentially attainable spatial multiplexing gain. In order to address this issue, in this paper, a novel generalized spatial modulation (GenSM) aided mmWave MIMO system is proposed, which enables the transmission of an extra data stream via the index of the active antennas group and requires no extra RF chain. Moreover, a two-step algorithm is also proposed to optimize the hybrid precoder design with respect to spectral efficiency (SE) maximization. Finally, numerical simulation results demonstrate the superior SE performance achieved by the proposed scheme.