# Capacity Analysis for Joint Radar-Communication Capable Coherent MIMO Radars

## TL;DR

This paper analyzes the communication channel capacity of joint radar-communication coherent MIMO radars under various fading conditions, revealing optimal waveform strategies for maximizing capacity.

## Contribution

It provides the first detailed analysis of how unintentional amplitude modulation affects communication capacity in JRC MIMO radars under different channel conditions.

## Key findings

- Single-side limited null direction waveform yields highest capacity.
- Capacity varies with Rayleigh and Rician fading conditions.
- Unintentional amplitude modulation impacts communication performance.

## Abstract

Recently, huge attention is attracted to the concept of integrating communication and radar missions within the same platform. Joint radar-communications (JRC) system gives an important opportunity to reduce spectrum usage and product cost while doing concurrent operation, as target sensing via radar processing and establishing communication links. A JRC-capable coherent MIMO radar system have been proposed recently in the literature. Several methods are introduced to reach dual goal as a notable null level towards the direction of interest of the radar and MIMO radar waveform orthogonality. Due to the limitations originated form the JRC operation, communication channel may encounter unwanted amplitude variations. This unwanted modulation normally affects the communication performance by its nature, due to the fades on radiated signal amplitude towards the direction of communication. However, the effect of this unintentional modulation on communication channel is yet to be investigated. In this paper, the communication channel for JRC capable phase-coded coherent MIMO radars is analyzed and investigated under additive white Gaussian noise and Rayleigh/Rician fading conditions. Communication capacity is evaluated for each channel condition. The results reveal that, using the single-side limited null direction fixed waveform generation method displays the best capacity performance under all channel conditions.