Digital Self-Interference Cancellation for Low-Cost Full-Duplex Radio Devices

Abstract

Wireless inband full-duplex communications, where individual radio devices transmit and receive simultaneously on the same frequency band, has recently been proposed as another step towards the full utilization of the available spectral resources. This chapter concentrates on solving the greatest challenge in wireless inband full-duplex communications, i.e., the self-interference, which refers to the interference produced by the own transmitter. To this end, this chapter provides digital-domain solutions for efficient self-interference cancellation in low-cost full-duplex radios. The proposed digital cancellers are capable of modeling the most prominent radio circuit impairments, in particular the nonlinear distortion produced by the transmitter power amplifier. The digital cancellers are evaluated using an actual inband full-duplex prototype, which contains also other self-interference suppression mechanisms operating in the analog domain. The obtained measurement results show that, with the help of these digital cancellers, the self-interference can be cancelled almost perfectly, proving that true full-duplex operation is indeed possible. Altogether, the own transmit signal is shown to be suppressed in some cases by more than 100 dB, which is one of the highest reported self-interference cancellation performances to date.