Fluid Antenna System for 6G: When Bruce Lee Inspires Wireless Communications

Abstract

Since its inception, multiple-input multiple-output (MIMO) has become a magical technology that continues to break new grounds and deliver the needed upgrades in mobile communications. The emerging 5G systems are also being labelled by many as the massive MIMO generation. This somewhat oversimplified view is perhaps a reflection of the great impact MIMO has had on our generation of mobile communication networks. Although the technologies have evolved in the past decades, the principle remains the same-to exploit the diversity of different copies of signals at independent locations for reducing the degree of fading and randomness of wireless channels. Through signal processing and coding, the diversity has been translated successfully into capacity gain and enhancement in other forms of the quality-of-service. This article identifies "fluid" antenna as a trending technology that may succeed MIMO and become a reality to transform wireless communications to a new height. Fluid antenna is a radical approach that advocates software-controlled position-flexible shape-flexible antenna. The concept liberates antennas to unleash massive diversity inherent in the small space of a mobile device and makes possible new opportunities that were previously unthinkable. This article attempts to be imaginative and aims to take readers on a short journey of what fluid antenna might bring in future-generation mobile communications systems and speculate on its impact.

Fluid Antenna Multiple Access

“…which happens when evaluating (17). To get around this, the second term inside the product can be evaluated by (18) (see next page), which can be obtained from the definition of I 0 (•).…”

“…In order to achieve this, it will require a technology that allows us to skim through a collection of fading envelopes and exploit their ups and downs. The technology that makes this realizable is fluid antenna which refers to any software-controllable fluidic, conductive radiating structure that can alter their shape and/or position to reconfigure the polarization, operating frequency, radiation pattern and etc., and it may include designs involving no fluidic materials if they can mimic the agility [18].…”

SWIPT with Intelligent Reflecting Surfaces under Spatial Correlation

“…the number of elements, the elements' size and dimensions as well as the implemented topology, so as to satisfy a certain correlation requirement. Also, more advanced IRSs could employ adaptive techniques, where elements can dynamically be switched on/off [4] or can be reconfigured through a software-controllable fluidic structure [11], in order to achieve the required correlation.…”

On the Diversity and Coded Modulation Design of Fluid Antenna Systems

“…, m. As before, we assume perfect channel estimation at the receiver. The channel estimates for a fixed resource block are spatially correlated over different ports based on the autocorrelation function defined in (7).…”

“…Moreover, the FA uses just one RF chain and so the spacing constraint does not apply in this case, making it a suitable technology for very small devices [6]. It follows that in comparison to conventional static metallic antennas, FAs can adjust their physical configuration (e.g., shape, feeding) as well as their electrical properties (e.g., resonant frequency, radiation pattern) [7]. Therefore, this technology provides a new degree of freedom in the design of wireless communication systems.…”