Experimental Study of Interference Suppression for Backscatter Communication in Distributed MIMO

TL;DR

This study experimentally compares beamforming techniques to suppress direct link interference in backscatter communication, demonstrating significant interference reduction and improved signal quality in a distributed MIMO setup.

Contribution

It introduces a direct-link suppression scheme that enforces spatial nulls, outperforming phase-only MRT in reducing interference in backscatter communication.

Findings

DLS reduces DLI at the reader by up to 31 dB compared to PO-MRT.

Measurements conducted with a 42-element array at 920 MHz validate the effectiveness of DLS.

The scheme enhances backscatter detection performance by mitigating interference.

Abstract

Bistatic backscatter communication requires strong illumination of a backscatter device (BD), while a spatially separated reader detects the weak modulated reflection. In practice, the resulting direct link interference (DLI) at the reader can dominate the received backscattered signal and limit detection performance. This paper experimentally investigates transmit beamforming that jointly maximizes BD illumination and suppresses DLI at the reader in a distributed multiple-input multiple-output setup. We compare phase-only maximum ratio transmission (PO-MRT) with the proposed direct-link suppression (DLS) scheme, which enforces a spatial null at the reader under per-antenna power constraints. Measurements using a phase-coherent 42-element ceiling array at 920 MHz show that DLS reduces the DLI at the target reader and improves the signal-to-interference ratio by up to 31 dB compared to PO-MRT.