Self-interference Cancellation in Full-duplex Wireless Systems

Due to the tremendous increase in wireless data traffic, one of the major challenges for future wireless systems is the utilization of the available spectrum to achieve better data rates over limited spectrum. Currently, systems operate in what is termed "Half Duplex Mode," where they are either transmitting or receiving, but never both using the same temporal and spectral resources. Full-duplex transmission promises to double the spectral efficiency where bidirectional communications is carried out over the same temporal and spectral resources. The main limitation impacting full-duplex transmission is managing the strong self-interference signal imposed by the transmit antenna on the receive antenna within the same transceiver. Several recent publications have demonstrated that the key challenge in practical full-duplex systems is un-cancelled self-interference power caused by a combination of hardware imperfections, especially Radio Frequency (RF) circuits' impairments. In this thesis, we consider the problem of self-interference cancellation in full-duplex systems. The ultimate goal of this work is to design and build a complete, real-time, full-duplex system that is capable of achieving wireless full-duplex transmission using practical hardware platforms. Since RF circuits' impairments are shown to have significant impact on the self-interference cancellation performance, first, we present a thorough analysis of the effect of RF impairments on the cancellation performance, with the aim of identifying the main performance limiting factors and bottlenecks. Second, the thesis proposes several impairments mitigation techniques to improve the overall self-interference cancellation capability by mitigating most of the transceiver RF impairments. In addition to impairments mitigation, two novel full-duplex transceiver architectures that achieve significant self-interference cancellation performance are proposed. The performance of the proposed techniques is analytically and experimentally investigated in practical wireless environments. Finally, the proposed self-interference cancellation techniques are used to build a complete full-duplex system with a 90\% experimentally proven full-duplex rate improvement compared to half-duplex systems