A Contemporary Survey on Fluid Antenna Systems: Fundamentals and Networking Perspectives

The explosive growth of teletraffic, fueled by the convergence of cyber-physical systems and data-intensive applications, demands a multidisciplinary suite of innovative solutions across the physical and network layers. As part of that suite, this paper advocates hardware-agnostic fluid antenna systems (FAS), which treat the radiating aperture as a reconfigurable physical-layer resource rather than a fixed component. By rapidly adjusting position, shape, or pattern, independent of the specific conductive medium or antenna embodiment, FAS exposes additional spatial degrees of freedom (DoF) that enable channel-aware diversity, opportunistic beamforming, and interference suppression, even with a single radio-frequency (RF) chain and compact form factors. This flexibility allows adaptation to fading, blockage, and traffic dynamics, improving outage, spectral efficiency, and energy efficiency, and positioning FAS as a promising candidate for next-generation communication networks. This paper provides a comprehensive survey of the state of the art in FAS research. We begin by examining key application scenarios in which FAS offers significant advantages. We then present the fundamental principles of FAS, covering channel measurement and modeling, single-user configurations, and the multi-user fluid antenna multiple access (FAMA) framework. Following this, we delve into key network-layer techniques such as quality-of-service (QoS) provisioning, power allocation, and content placement strategies. We conclude by identifying prevailing challenges and outlining future research directions to support the continued development of FAS in next-generation wireless networks.