Challenges and possibilities for flexible duplexing in 5G networks

This paper discusses the role of flexible duplexing in the research and development of 5G wireless networks. Legacy large coverage area networks have been designed for static and symmetric radio resources utilization where the uplink and downlink have most often been separated in frequency domain. More recently, the trend has been toward small cells deployment where time division duplex (TDD) has increased its popularity. TDD has also the advantage that it supports asymmetric radio resource division between up- and downlink either in fixed or dynamic manner. Another booster in duplexing techniques is in-band full-duplex (FD) transmission and reception. It has been around for a long time but only recently the implementation technology has progressed enough to make it a viable option for wireless bi-directional links. Key properties, advantages, disadvantages and design challenges related to alternative duplex techniques and their hybrids are discussed in the light of 5G emergence.