Achievable rate regions and self-interference channel estimation in hybrid full-duplex/half-duplex radio links

This article investigates the achievable rates of a bidirectional full-duplex radio link between a base station and a mobile user in a cellular network. In particular, we analyze the relationship between accurate self-interference channel estimation, which is required for effective digital interference cancellation, and spectral-efficient simultaneous two-way data transmission and reception, which is the objective for developing the full-duplex technology in the first place. Channel estimation and data transmission are inherently coupled due to a trade-off arising from the facts that the former benefits from half-duplex slots during which there is no distortion from the data signal of interest while the latter needs full-duplex slots for approaching the anticipated ideal-case doubled spectral efficiency in comparison to plain half-duplex operation. The analysis is conducted by deriving expressions for the achievable data rates and calculating the corresponding rate regions with the help of realistic waveform simulations for incorporating transceiver hardware impairments, which render residual self-interference despite effective cancellation. The findings indicate that increased flexibility in the form of half-duplex communication periods of adjustable lengths results in an increased overall throughput. Thereby, hybrid half/full-duplex operation is not only useful for improving the performance of digital self-interference cancellation but also for supporting varying unbalanced downlink-uplink traffic ratios.