A Multipath Approach to Self-Interference Cancellation in MIMO Rayleigh Fading Channels

Abstract

An optically enabled multi-path self-interference (MSI) cancellation technique for in-band full duplex (IBFD) RoF MIMO systems under Rayleigh fading channels is proposed. A digitally assisted Rayleigh fading channel model generates the MSI signal. An optically tunable multi-path delay lines (OTMDL) module is designed using optical delay lines (ODL) and an optical attenuator (OA) for coarse and fine-tuning of time delays and amplitude matching between the locally generated reference (LR) signal and the MSI signal. The OTMDL module adjusts the LR signal to cancel the effect of MSI on the signal received through the fading channel. The concept is validated using a remote sensor node of a 3x3 IBFD MIMO RoF system with a Rayleigh fading channel. The system’s performance is evaluated by determining the MSI cancellation depths using the OTMDL section for various cancellation channels, and by computing the MSI cancellation for both single band and wide band signals across different cancellation channels. An average value of MSI cancellation depth of 20.38 dB is obtained for a single-tone RF signal in the range 15 GHz - 25 GHz. Thus, the proposed system for MSI cancellation can be utilized in wireless communication systems in multiple way.