Development of Full-Duplex Cellular System for Beyond 5G and 6G Systems

Abstract

In-band full-duplex (IBFD) is a technique for transmitting and receiving signals simultaneously using the same frequency and time slot. Ideally, by adopting IBFD, the frequency utilization efficiency can be twice than that of the half-duplex. In this study, we focus on a full-duplex cellular (FDC) system, where the base station (BS) allows for the superimposition of downlink (DL) communications with other user equipment (UE) on the uplink (UL) communications and the superimposition of UL communications with other UE on DL communications by applying IBFD. The BS needs to identify the UE whose signals do not degrade DL communication quality in the FDC. Moreover, self-interference (SI) of the BS (i.e., interference when the transmitted signal interferes with its own received signal in IBFD) should not degrade the UL communication quality. This paper summarizes the system configuration and research and development items on the dynamic-duplex cellular system that is generally operated in half-duplex. It adaptively performs IBFD only for UEs whose signal does not interfere with other users. In addition, this paper summarizes the development of a monitoring system for the interference from UEs and the development of digital and analog SI canceller applicable to a BS. The developed BS can reduce SI by more than 35 dB in the RF and more than 20 dB in the digital parts.