Guest Editorial Special Issue on Antennas and Propagation Aspects of In-Band Full-Duplex Applications

Future generations of wireless services will always need more efficient strategies for the use of the available frequency spectrum, given the ever-increasing demand for high-speed data services. One of such strategies is given by in-band full-duplex (IBFD) systems, also called simultaneously transmit and receive (STAR) systems, that are considered because spectrum efficiency is not maximized with the current practice of half-duplex communication, where a node either transmits or receives a signal in a single channel. In fact, all currently deployed wireless networks require two separate channels to achieve bi-directionality: Frequency Division Duplex (FDD) and Time Division Duplex (TDD) are the two most commonly-used techniques. This channel separation prevents the self-interference that has been seen as an insurmountable technical problem. Promoted by the popularity of small cell wireless systems, recent works have provided experimental evidence and methodologies for IBFD systems, where a node transmits and receives signals at the same time and on the same frequency band [1], [2]. IBFD systems not only increase spectral efficiency, but also minimize overhead and timing constraints. This increases throughput and allows for the possibility of real-time sensing of spectrum occupancy for cognitive devices [3]. Even though IBFD systems have their primary application for bidirectional communication topology (where there are two data flows: terminal A sends data to terminal B, and terminal B sends data to terminal A), a different body of recent works has focused on IBFD in other settings including relay, base-station and multi-hop topologies [4]–[7].