Sensing, beamforming and self-interference mitigation methods for full-duplex communications

Date

2025-8-26

Author

Kurt, Anıl

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Full-Duplex (FD) communication systems enable simultaneous transmission and reception using the same frequency and time resources, potentially doubling the data rate. However, the self-interference (SI) is a bottleneck for FD operation. This thesis investigates SI mitigation and beamforming techniques for FD communication systems, with a focus on time-varying channels and millimeter-wave (mmWave) multiple-input multiple-output (MIMO) architectures. The first part addresses SI cancellation in single-antenna FD systems, examining the effects of nonlinear distortions caused by power amplifier impairments and rapid variations in the SI channel. A novel adaptive-iterative cancellation algorithm is proposed to combat signal-of-interest contamination and reduce complexity by separating nonlinear learning from real-time operation. The second part focuses on far-field SI in mmWave MIMO systems, where environmental echoes from scatterers create SI with spatial and temporal characteristics. A hybrid scheme combining angle-based spatial suppression and delay-based digital SI cancellation is developed. Using sensing methods and a scatterer map, the system adaptively selects the optimal mitigation action for each scatterer to maintain robust communication performance in dynamic environments. Finally, the third part complements the FD operation by enabling robust angular estimation and beam tracking of user equipments. A low-complexity two-stage beamforming framework is proposed for multi-cluster, time-varying massive MIMO channels, leveraging reduced-dimensional statistical methods and distinguishing fast- and slow-time channel parameters. Overall, the contributions in this thesis offer a holistic SI mitigation and beamforming strategy for emerging FD mmWave systems, addressing both near- and far-field interference while ensuring robustness to environmental dynamics and hardware limitations.

Subject Keywords

Millimeter-wave, MIMO, Full-duplex, Self-interference cancellation, Spatial suppression

URI

https://hdl.handle.net/11511/116057

Collections

Graduate School of Natural and Applied Sciences, Thesis