An In-Band Full-Duplex Prototype With Joint Self-Interference Cancellation in Antenna, Analog, and Digital Domains

In-band full-duplex (IBFD) technology has been extensively researched over the last decade, and numerous techniques have been proposed to cancel self-interference (SI) caused by the simultaneously transmitted local in-band signal. Although some prototypes for SI cancellation (SIC) have been published, there are limited works demonstrating the communication performance of the IBFD system. The noise enhancement caused by analog and/or digital SIC is mostly ignored in the literature. This article presents a prototype for an IBFD system with solutions in three domains of SI mitigation. A practical structure for joint analog and digital SIC is proposed and implemented using off-the-shelf components. The transmit data frame is designed to align with the track/hold control signaling so that the irreducible noise caused by the analog SIC can be avoided. By combining a full-duplex antenna, an analog SIC filter, and a field-programmable gate array (FPGA) platform, this prototype successfully demonstrates the performance of the desired IBFD communications. Experiments on the prototype with 50-MHz bandwidth signaling show that under a certain hardware condition, the proposed SIC solution can sufficiently mitigate the SI with 75 dB of cancellation, and a low bit error rate (BER
$ < 10^{-4}$
) is demonstrated to allow practical applications.