# Receive Spatial Modulation for Massive MIMO Systems

## TL;DR

This paper introduces a receive spatial modulation architecture for massive MIMO systems that reduces power consumption at the user terminal by using analog devices and simple threshold detection, while maintaining high throughput.

## Contribution

It proposes a novel receive spatial modulation scheme with low-power analog detection and derives analytical expressions for detection thresholds and error probabilities.

## Key findings

- Threshold detector performance approaches optimal at high SNR
- Small pilot symbols suffice for threshold estimation
- Performance gap with fully digital MIMO can be minimized with proper constellation design

## Abstract

In this paper, we consider the downlink of a massive multiple-input-multiple-output (MIMO) single user transmission system operating in the millimeter wave outdoor narrowband channel environment. We propose a novel receive spatial modulation architecture aimed to reduce the power consumption at the user terminal, while attaining a significant throughput. The energy consumption reduction is obtained through the use of analog devices (amplitude detector), which reduces the number of radio frequency chains and analog-to-digital-converters (ADCs). The base station transmits spatial and modulation symbols per channel use. We show that the optimal spatial symbol detector is a threshold detector that can be implemented by using one bit ADC. We derive closed form expressions for the detection threshold at different signal-to-noise-ratio (SNR) regions showing that a simple threshold can be obtained at high SNR and its performance approaches the exact threshold. We derive expressions for the average bit error probability in the presence and absence of the threshold estimation error showing that a small number of pilot symbols is needed. A performance comparison is done between the proposed system and fully digital MIMO showing that a suitable constellation selection can reduce the performance gap.