Coexistence Analysis between Radar and Cellular System in LoS Channel

TL;DR

This paper investigates interference mitigation between MIMO radar and cellular systems using null space projection, showing larger radar arrays improve performance and that channel coherence times support effective CSI-based mitigation.

Contribution

It analyzes the effectiveness of NSP-based interference mitigation in radar-cellular coexistence, highlighting the benefits of larger radar arrays and channel coherence considerations.

Findings

Larger radar arrays reduce projected power at nearby targets.

Channel coherence time exceeds radar pulse intervals, supporting CSI-based mitigation.

NSP can effectively mitigate interference in practical scenarios.

Abstract

Sharing spectrum with incumbents such as radar systems is an attractive solution for cellular operators in order to meet the ever growing bandwidth requirements and ease the spectrum crunch problem. In order to realize efficient spectrum sharing, interference mitigation techniques are required. In this letter we address techniques to mitigate MIMO radar interference at MIMO cellular base stations (BSs). We specifically look at the amount of power received at BSs when radar uses null space projection (NSP)-based interference mitigation method. NSP reduces the amount of projected power at targets that are in-close vicinity to BSs. We study this issue and show that this can be avoided if radar employs a larger transmit array. In addition, we compute the coherence time of channel between radar and BSs and show that the coherence time of channel is much larger than the pulse repetition interval of radars. Therefore, NSP-based interference mitigation techniques which depends on accurate channel state information (CSI) can be effective as the problem of CSI being outdated does not occur for most practical scenarios.