Crosstalk and Self-Interference Cancellation in Full-Duplex Communication Systems

This paper provides insights into the ongoing research work of NATO IST-175-RTG that aims to demonstrate the benefits of full-duplex radios in military applications. Full-duplex radios in general allow to simultaneously transmit and receive RF signals in the same frequency band but require solving technical challenges that are not present in conventional half-duplex systems. Mainly this means suppressing the self-interference which is caused by the transmitted signal reaching the receiver path. This can result because of, e.g., circulator leakage, antenna mismatch, or reflections from the environment. Several techniques, both digital and analog, have been proposed in literature to cope with such strong interference in the receiver path after the point from which the interference has reached there. However, an additional challenge can arise in transceivers with improper internal isolation such as, e.g., low-cost software-defined radios, where the leaking, or crosstalk, takes place inside the radio. In such cases, the analog cancellation cannot be positioned after the leakage point but must be implemented pre-emptively. This paper quantifies the crosstalk for one such commercial-off-the-self transceiver plus presents and compares solutions for managing both, the crosstalk, and the self-interference either separately or jointly. This paper was originally presented at the NATO Science and Technology Organization Symposium (ICMCIS) organized by the Information Systems Technology (IST) Panel, IST-200 RSY - the ICMCIS, held in Skopje, North Macedonia, 16-17 May 2023.