Fluid Antenna System-Part I: Preliminaries

With research efforts gearing up to build the sixth-generation (6G) mobile communications, it is only logical to seek new mobile technologies that can provide the next generational leap for much better performance under harsher environments. To this end, one interesting concept is fluid antenna system (FAS) which utilizes flexible antenna architectures such as liquid-based antennas, reconfigurable RF pixel-based antennas, stepper motor-based antennas, and etc., to enable reconfigurability of antenna's position (i.e., port). In so doing, tremendous space diversity can be obtained in a novel way. The possibility of accessing seemingly a continuous fading envelope in the spatial domain also means that multiple access can be realized in a simple manner without complex optimization and processing. This is the first of a three-part letter that reviews the basic principles of FAS. Our scope focuses on the physical-layer performance metrics and we discuss the evolution of the channel models being adopted for FAS and summarize the key results highlighting its potential.