Digital-assisted photonic analog wideband multipath self-interference cancellation

TL;DR

This paper introduces a digital-assisted photonic analog wideband self-interference cancellation method for in-band full-duplex systems, utilizing a dual-drive Mach-Zehnder modulator and RLS algorithm to effectively suppress multipath SI signals.

Contribution

It presents a novel approach combining photonic analog techniques with digital algorithms to overcome limitations of previous SIC methods in multipath environments.

Findings

Achieved about 26.7 dB cancellation depth at 10 GHz with 0.5 Gbaud SI baud rate.

Demonstrated effective cancellation even when direct and multipath SI signals have similar power levels.

Validated the method through experiments showing significant suppression of self-interference.

Abstract

A digital-assisted photonic analog wideband radio-frequency multipath self-interference cancellation (SIC) and frequency downconversion method based on a dual-drive Mach-Zehnder modulator and the recursive least square (RLS) algorithm is proposed and demonstrated for in-band full-duplex systems. Besides the reference for the direct-path self-interference (SI) signal, the RLS algorithm is used to construct another reference for the residual SI signal from the direct path and the SI signals from the reflection paths. The proposed method can solve the performance limitation in the previously reported SIC methods of constructing the multipath SI signal using a single reference caused by the limited dynamic range of the digital-to-analog converter when the direct-path SI signal is much stronger than the sub-weak reflection-path SI signals. An experiment is performed. When the carrier frequency of the multipath SI signal is 10 GHz and the direct-path SI signal is much stronger than the sub-weak multipath SI signal, the cancellation depths of about 26.7 and 26.1 dB are realized with SI baud rates of 0.5 and 1 Gbaud. When the direct-path SI signal and sub-weak multipath SI signal own closer power, the corresponding cancellation depths are 24.7 and 20.8 dB, respectively.