Intelligent-Metasurface-Assisted Full-Duplex Wireless Communications

Abstract

The limited radio-frequency spectrum is a fundamental factor in the design of wireless communication systems. The ever increasing number of wireless devices and systems has led to a crowded spectrum and increased the demand for versatile and multi-functional full-duplex wireless apparatuses. Recently, dynamic and intelligent metasurfaces are explored as a prominent technological solution to the current paradigm of spectrum scarcity by opportunistically sharing the spectrum with various users. In general, intelligent metasurfaces are dynamic, ultra-compact, multi-functional and programmable structures which are capable of both reciprocal and nonreciprocal signal wave transmissions in a full-duplex manner. The controllability and programmability of such metasurfaces are governed through the dc bias and occasionally a radio-frequency (RF) modulation applied to the the active components of the unit cells of the metasurface, e.g., diodes and transistors. This article shows that such intelligent metasurfaces can enhance the performance of wireless communications systems thanks to their unique features such as real-time signal coding, nonreciprocal-beam radiation, nonreciprocal beamsteering amplification, and advanced patterncoding multiple access communication.

Optical Pulse Compression Assisted by High‐Q Time‐Modulated Transmissive Metasurfaces

“…In other words, TMMs provide control over both spatial and spectral content of the scattered light, which can significantly extend the degree of light manipulation compared to their static and quasi-static counterparts. This is manifested in a myriad of novel physical phenomena for different applications such as acquiring a nonreciprocal response, [44][45][46][47][48][49][50][51][52][53] pulse shaping and time reversal, [54][55][56] dynamic beam steering, [57][58][59] signal processing, [60] spatiotemporal light manipulation, [61][62][63] signal amplification, [64] extreme energy accumulation, [65] wideband impedance matching, [66] and wave camouflaging. [67,68] It should be remarked that the concept of time-modulation has recently found its way into other realms of physics such as acoustics and thermal sciences, and enabled a wide spectrum of novel functionalities.…”

Angular and Polarization Stability of Broadband Reconfigurable Intelligent Surfaces of Binary Type

“…Meanwhile, adaptive shaping of the wireless channels has made the RIS a promising candidate for smart radio environments [12], [13]. Recently, RISs have been used to realize the binary frequency shift-keying (BFSK) transmitter [14], multi-modulation schemes [15], IRS-assisted full-duplex wireless communications [16], MIMO-assisted networks [17], and non-orthogonal multiple access (NOMA) communication network [18]. Often, the RIS paradigm is considered within the programmable metasurface concept [6].…”

“…This approach allows the unit cell to mimic two digital states -'0' and '1'. Being easier to implement and cheaper to fabricate and exploit, especially at the biasing point, binary MSs have got a hot topic status in the modern literature on RISs [2], [16], [25].…”