A numerical investigation of all-analog radio self-interference cancellation

Radio self-interference cancellation (SIC) is the fundamental enabler for full-duplex radios. While SIC methods based on baseband digital signal processing and/or beamforming are inadequate, an all-analog method is useful to drastically reduce the self-interference as the first stage of SIC. However, all-analog radio SIC has so far received very little academic attention in terms of its architectural design and performance limit. In this paper, we present such an early effort. We show that a recently used uniform architecture with uniformly distributed RF attenuators has a performance highly dependent on the carrier frequency. We also show that a new architecture with the attenuators distributed in a clustered fashion has important advantages over the uniform architecture. These advantages are shown numerically through random multipath interference channels, number of control bits in step attenuators, attenuation-dependent phases, single and multi-level structures, etc. These insights will be useful in guiding future hardware-based experiments.