A wideband, compact monopolar patch antenna with an inherent filtering response is presented in this paper. By employing a slot-assisted mode-tailoring technique, the field distributions of several higher-order modes at the patch center are engineered to produce a stable monopolar radiation pattern with enhanced bandwidth. The closed-form analysis indicates that increasing the current intensity at the central region can transform the conventional TM22mode into one that exhibits a monopolar pattern. This concept is realized by incorporating four slanted slots at the corners of the patch, which constrain the surface current toward the patch center. Besides, these slots also excite an additional slot mode, which serves as a second resonance. At higher frequencies, the slots continue to confine the current distribution of the original TM33mode to a small central region and thereby forming a quasi-TM01monopolar radiation. By combining the three engineered resonances, the proposed single-layer patch achieves a significantly improved bandwidth. (The simulated and measured impedance bandwidths (S11 < -10 dB) are 26.9% and 27.1% respectively). More importantly, the proposed antenna preserves a stable radiation pattern even when the ground-plane size changes. This robustness arises from the slot-assisted mode-tailoring scheme, which strongly confines the current distribution to the central region of the patch. The small-footprint prototype realizes peak gains of 6.92 dBi in simulation and 6.42 dBi in measurement. To ensure the application of the proposed antenna on a vehicle, a large-scale simulation has been performed to verify the wide impedance bandwidth, realized gain and consistent radiation patterns when the antenna is positioned on the roof of a car. While good in-band results are obtained. Radiation nulls are observed near the band edges, resulting from the mutual cancellation of radiated fields. With its broad bandwidth, stable monopolar radiation, and built-in filtering (stopband gain not exceeding 0 dBi), the proposed antenna offers an attractive solution for modern wireless platforms demanding compact form factors and robust interference immunity.

Fluid antenna systems (FAS) have recently emerged as a promising solution for sixth-generation (6G) ultra-dense connectivity. These systems utilize dynamic radiating and/or shaping techniques to mitigate interference and improve spectral efficiency without relying on channel state information (CSI). The reported improvements achieved by employing a single dynamically activated radiating position in fluid antenna multiple access (FAMA) are significant. To fully realize the potential of FAMA in multi-user multiplexing, we propose leveraging the unique fast-switching capabilities of a single radio-frequency (RF)-chain meta-fluid antenna structure to achieve multi-activation. This allows for a significantly larger set of independent radiating states without requiring additional signal processing. Simulations demonstrate that multi-activation FAMA enables robust multi-user multiplexing with a higher signal-to-interference ratio (SIR) under various Rayleigh-fading environments compared to other single RF-chain technologies. We further show that the SIR can be optimized within a 15~$μs$ timeframe under a multi-user Rayleigh-fading channel, making the proposed scheme highly suitable for fast-changing wireless environments. Verified through the theoretical Jakes' model, full three-dimensional (3D) electromagnetic (EM) simulations and experimental validation, multi-activation FAMA enables effective CSI-free, multi-user communication, offering a scalable solution for high-capacity wireless networks.

Smart cities demand versatile antenna systems supporting heterogeneous wireless applications across diverse propagation environments. This paper presents a wideband pixel-based fluid antenna system (PB-FAS) designed as a general-purpose antenna solution for smart city infrastructures, addressing fundamental challenges in wideband operation, spatial adaptability, interference mitigation, and scalable deployment. The proposed PB-FAS integrates parasitic elements for enhanced bandwidth (6.0-7.0 GHz) and a compact 6-PIN-diode pixel surface enabling 64 distinct fluid states, achieving optimal cost-performance balance. An integrated FPGA-based control system provides microsecond-level reconfiguration for real-time channel adaptation. We establish a rigorous exact spatial geometry (ESG) channel model capturing state-dependent antenna responses across near-field and far-field regions, providing a unified theoretical foundation for interference mitigation analysis. Comprehensive validation through full-wave electromagnetic simulations, anechoic chamber measurements, and experimental two-source 16-QAM communication tests demonstrates up to 11 dB SINR improvement and 13.2% EVM reduction through hardware-level spatial diversity, confirming the system’s effectiveness as a scalable, cost-effective solution for next-generation smart city wireless infrastructures ranging from IoT sensor networks to high-capacity backhaul links.

Fluid antenna (FA) technology has emerged as a promising approach in wireless communications due to its capability of providing increased degrees of freedom (DoFs) and exceptional design flexibility. This paper addresses the challenge of direction-of-arrival (DOA) estimation for aligned received signals (ARS) and non-aligned received signals (NARS) by designing two specialized uniform FA structures under time-constrained mobility. For ARS scenarios, we propose a fully movable antenna configuration that maximizes the virtual array aperture, whereas for NARS scenarios, we design a structure incorporating a fixed reference antenna to reliably extract phase information from the signal covariance. To overcome the limitations of large virtual arrays and limited sample data inherent in time-varying channels (TVC), we introduce two novel DOA estimation methods: TMRLS-MUSIC for ARS, combining Toeplitz matrix reconstruction (TMR) with linear shrinkage (LS) estimation, and TMR-MUSIC for NARS, utilizing sub-covariance matrices to construct virtual array responses. Both methods employ Nyström approximation to significantly reduce computational complexity while maintaining estimation accuracy. Theoretical analyses and extensive simulation results demonstrate that the proposed methods achieve underdetermined DOA estimation using minimal FA elements, outperform conventional methods in estimation accuracy, and substantially reduce computational complexity.

An auto-polarization fluid antenna (APFA) is developed for indoor wireless channel sounding and employed to reveal a novel “fluid polarization effect” (FPE) in wireless communications. Unlike conventional fluid antennas (FAs) that are steering their beams/nulls with the aid of external mechanical/electronic actuators, the APFA only relies on the natural swinging of human arms to yield a self-driven polarization switching ability. Compared with the conventional fixed circularly polarized antennas, the wrist-worn, self-driven APFA in indoor wireless channel sounding systems effectively reduces multipath clusters (MPCs), attains smaller path loss exponent (PLE), and consequently yields the FPE. Compared to the fixed circularly polarized case with PLE= 1.62, the measured PLE is reduced by 14% to 1.38, and the system packet error rate (PER) is improved by 76%. It realizes robust anti-multipath fading performance owing to the much-improved FPE. The fluid effect in polarization domain is anticipated to remarkably enhance the anti-multipath fading performance of wearable wireless communication systems. It opens a new horizon to develop self-driven, cost-effective fluid antenna systems (FASs) for universal applications.

In-band full-duplex (IBFD) systems are expected to double the spectral efficiency compared to half-duplex systems, provided that loopback self-interference (SI) can be effectively suppressed. The inherent interference mitigation capabilities of the emerging fluid antenna system (FAS) technology make it a promising candidate for addressing the SI challenge in IBFD systems. This paper thus proposes a FAS-assisted self-interference cancellation (SIC) framework, which leverages a receiver-side FAS to dynamically select an interference-free port. Analytical results include a lower bound and an approximation of the residual SI (RSI) power, both derived for rich-scattering channels by considering the joint spatial correlation amongst the FAS ports. Simulations of RSI power and forward link rates validate the analysis, showing that the SIC performance improves with the number of FAS ports. Additionally, simulations under practical conditions, such as finite-scattering environments and wideband integrated access and backhaul (IAB) channels, reveal that the proposed approach offers superior SIC capability and significant forward rate gains over conventional IBFD SIC schemes.

Fluid antenna systems (FAS) are emerging as a transformative enabler for sixth-generation (6G) wireless communications, providing unprecedented spatial diversity through dynamic reconfiguration of antenna ports. However, the inherent spatial correlation among ports poses significant challenges for accurate analysis. Conventional models such as Jakes are analytically intractable, while oversimplified constant-correlation models fail to capture the true behavior. In this work, we address these challenges by applying the variable block-correlation model (VBCM) -- originally proposed by Ramírez-Espinosa \textit{et al.} in 2024 -- to FAS security analysis, and by developing comprehensive optimization methods to enhance analytical accuracy. We derive new closed-form expressions for average secrecy capacity (ASC) and secrecy outage probability (SOP), demonstrating that the VBCM framework achieves simulation-aligned accuracy, with relative errors consistently below $5\%$ (compared to $10$--$15\%$ for constant-correlation models). To maximize ASC, we further design two algorithms: a grid search (GS) method and a gradient descent (GD) method. Numerical results reveal that the VBCM-based approach not only provides reliable insights into FAS security performance, but also yields substantial gains -- ASC improvements exceeding $120\%$ in high-threat scenarios and $18$--$19\%$ performance enhancements for compact antenna configurations. These findings underscore the practical value of integrating VBCM into FAS security analysis and optimization, establishing it as a powerful tool for advancing 6G communication systems.

This paper proposes a hardware-software co-design approach to efficiently optimize beamforming and port selection in fluid antenna systems (FASs). To begin with, a fluid-antenna (FA)-enabled downlink multi-cell multiple-input multiple-output (MIMO) network is modeled, and a weighted sum-rate (WSR) maximization problem is formulated. Second, a method that integrates graph neural networks (GNNs) with random port selection (RPS) is proposed to jointly optimize beamforming and port selection, while also assessing the benefits and limitations of random selection. Third, an instruction-driven deep learning accelerator based on a field-programmable gate array (FPGA) is developed to minimize inference latency. To further enhance efficiency, a scheduling algorithm is introduced to reduce redundant computations and minimize the idle time of computing cores. Simulation results demonstrate that the proposed GNN-RPS approach achieves competitive communication performance. Furthermore, experimental evaluations indicate that the FPGA-based accelerator maintains low latency while simultaneously executing beamforming inference for multiple port selections.

This paper investigates a design framework for sparse fluid antenna systems (FAS) enabling high-performance direction-of-arrival (DOA) estimation, particularly in challenging millimeter-wave (mmWave) environments. By ingeniously harnessing the mobility of fluid antenna (FA) elements, the proposed architectures achieve an extended range of spatial degrees of freedom (DoFs) compared to conventional fixed-position antenna (FPA) arrays. This innovation not only facilitates the seamless application of super-resolution DOA estimators but also enables robust DOA estimation, accurately localizing more sources than the number of physical antenna elements. We introduce two bespoke FA array structures and mobility strategies tailored to scenarios with aligned and misaligned received signals, respectively, demonstrating a hardware-driven approach to overcoming complexities typically addressed by intricate algorithms. A key contribution is a light-of-sight (LoS)-centric, closed-form DOA estimator, which first employs an eigenvalue-ratio test for precise LoS path number detection, followed by a polynomial root-finding procedure. This method distinctly showcases the unique advantages of FAS by simplifying the estimation process while enhancing accuracy. Numerical results compellingly verify that the proposed FA array designs and estimation techniques yield an extended DoFs range, deliver superior DOA accuracy, and maintain robustness across diverse signal conditions.

Surface wave communication (SWC) is an emerging technology garnering significant interest for its diverse potential applications in communications. However, accurately computing electromagnetic field strength, which is related to the path loss, in reconfigurable surface structures, particularly for long-distance transmission, presents an ongoing challenge. To address this, we introduce a novel analytical model employing surface wave ray tracing. Unlike conventional simulations, our analytical approach enables precise computation of the electromagnetic field strength attenuation in both short and long-distance transmissions, providing invaluable insights for practical SWC implementations. Our proposed model takes into account key system parameters such as surface material, thickness, cavity porosity, and other variables influencing propagation performance. This facilitates analysis of optimal reconfigurable structures. Simulation results validate the model’s accuracy in short-distance transmission, thereby endorsing its effectiveness in studying surface wave path loss over longer distances. Furthermore, our study demonstrates the SWC superiority over traditional coaxial cable and space-wave communication in mitigating path loss. Additionally, we explore the impacts of various factors such as different dielectric layers, wall materials, leakage, and pathway width on SWC performance, providing deeper insights into designing optimal reconfigurable structures for SWC applications.

Fluid antenna system (FAS) is an emerging technology that uses the new form of shape- and position-reconfigurable antennas to empower the physical layer for wireless communications. Prior studies on FAS were however limited to narrowband channels. Motivated by this, this paper addresses the integration of FAS in the fifth generation (5G) orthogonal frequency division multiplexing (OFDM) framework to address the challenges posed by wideband communications. We propose the framework of the wideband FAS-OFDM system that includes a novel port selection matrix. Then we derive the achievable rate expression and design the adaptive modulation and coding (AMC) scheme based on the rate. Extensive link-level simulation results demonstrate striking improvements of FAS in the wideband channels, underscoring the potential of FAS in future wireless communications.

This paper investigates the performance of a single-user fluid antenna system (FAS), by exploiting a class of elliptical copulas to describe the dependence structure amongst the fluid antenna positions (ports). By expressing the well-known Jakes’ model in terms of the Gaussian copula, we consider two cases: (i) the general case, i.e., any arbitrary correlated fading distribution; and (ii) the specific case, i.e., correlated Nakagami-m fading. For both scenarios, we first derive analytical expressions for the cumulative distribution function (CDF) and probability density function (PDF) of the equivalent channel in terms of multivariate normal distribution. Then we obtain the outage probability (OP) and the delay outage rate (DOR) to analyze the performance of FAS. By employing the popular rank correlation coefficients such as Spearman’s$\rho $and Kendall’s$\tau $, we measure the degree of dependency in correlated arbitrary fading channels and illustrate how the Gaussian copula can be accurately connected to Jakes’ model in FAS. Our numerical results demonstrate that increasing the size of FAS provides lower OP and DOR, but the system performance saturates as the number of antenna ports increases. In addition, our results indicate that FAS provides better performance compared to conventional single-fixed antenna systems even when the size of fluid antenna is small.

To enable innovative applications and services, both industry and academia are exploring new technologies for sixth generation (6G) communications. One of the promising candidates is fluid antenna system (FAS). Unlike existing systems, FAS is a novel communication technology where its antenna can freely change its position and shape within a given space. Compared to the traditional systems, this unique capability has the potential of providing higher diversity and interference-free communications. Nevertheless, the performance limits of FAS remain unclear as its system properties are difficult to analyze. To address this, we approximate the outage probability and diversity gain of FAS in closed-form expressions. We then propose a suboptimal FAS with$N^{\ast}$ports, where a significant gain can be obtained over FAS with$N^{\ast}-1$ports whilst FAS with$N^{\ast}+1$ports only yields marginal improvement over the proposed suboptimal FAS. In this paper, we also provide analytical and simulation results to unfold the key factors that affect the performance of FAS. Limited to systems with one active radio frequency (RF)-chain, we show that the proposed suboptimal FAS outperforms single-antenna (SISO) system and selection combining (SC) system in terms of outage probability. Interestingly, when the given space is$\frac {\lambda }{2}$, the outage probability of the proposed suboptimal FAS with one active RF-chain achieves near to that of the maximal ratio combining (MRC) system with multiple active RF-chains.

Multiple-input multiple-output (MIMO) system has been the defining mobile communications technology in recent generations. With the ever-increasing demands looming towards the sixth generation (6G), we are in need of additional degrees of freedom that deliver further gains beyond MIMO. To this goal, fluid antenna system (FAS) has emerged as a new way to obtain spatial diversity using reconfigurable position-switchable antennas. Considering the case with more than one ports activated on a 2D fluid antenna surface at both ends, we take the information-theoretic approach to study the achievable performance limits of the MIMO-FAS. First of all, we propose a suboptimal scheme, referred to as QR MIMO-FAS, to maximize the rate at high signal-to-noise ratio (SNR) via joint port selection, transmit and receive beamforming and power allocation. We then derive the optimal diversity and multiplexing tradeoff (DMT) of MIMO-FAS. From the DMT, we highlight that MIMO-FAS outperforms traditional MIMO antenna systems. Further, we introduce a new metric, namelyq-outage capacity, which can jointly consider rate and outage probability. Through this metric, our results indicate that MIMO-FAS surpasses traditional MIMO greatly.

This paper aims to present a simple multiple access scheme for massive connectivity that enables a large number of mobile user equipments (UEs) to occupy the same time-frequency channel without the need of precoding and power control at the base station (BS) and interference cancellation at each UE. The proposed approach does not even require the UEs to know their signal-to-interference ratios (SIRs) and each UE also needs only two radio-frequency (RF) chains to operate. The proposed scheme is inspired by the emerging concept of fluid antenna system (FAS) which enables high-resolution position-switchable antenna to be deployed at each UE. Instead of activating only one port of FAS for reception, each UE activates an ultra massive number of ports to receive the signal. The activated ports are chosen to ensure that the in-phase and quadrature components of the desired signal at the ports are added constructively while the interference signals superimpose randomly. This approach is referred to as compact ultra massive antenna array (CUMA) which can also be realized by deploying a dense, fixed massive antenna array at each UE. We derive the exact probability density function (pdf) of the SIR of a CUMA UE which leads to the data rate analysis. Simulation results demonstrate that even with mutual coupling and under finite scattering, more than 10 UEs can be supported by having a 25×13-port FAS of size 15 cm×8 cm at each UE. Considering quadrature phase shift keying (QPSK), CUMA delivers a network data rate of 10.7 bps per channel use serving 10 UEs at 26 GHz, and the rate is risen to 15.1 bps per channel use if 20 UEs are accommodated at 40 GHz with a 40×21-port FAS at every UE. In the case without mutual coupling and under rich scattering, CUMA can even support hundreds of UEs per channel use.

Fluid antenna system (FAS) is a new flexible antenna technology that offers a new approach to multiple access, referred to as fluid antenna multiple access (FAMA). The performance of FAMA has been investigated but previous results were based on simplified spatial correlation models. In this paper, we will revisit FAMA for the two-user case and study the outage probability by characterizing the joint spatial correlation among the ports. We first derive a closed-form lower bound on the outage probability and reveal that in the absence of spatial correlation, the outage probability of the system decreases exponentially as the number of ports increases. We then show that the channel model can be greatly simplified by focusing upon a limited number of channel variables, allowing us to derive the outage probability using the approximate model. To gain insight, we further approximate the channel model and provide another approximation of the outage probability that is easier to compute. Simulation results validate the approximations and demonstrate that the outage probability decreases with the number of ports but has an error floor unless the antenna size is increased. Also, when the number of ports is fixed, the outage probability initially decreases exponentially with the size but eventually approaches the lower bound.

Fluid antenna system (FAS) is an emerging flexible antenna technology that provides a new way for multiple access. In fluid antenna multiple access (FAMA), each user switches its fluid antenna to the location (i.e., port) in which the interfering users suffer from a deep fade for interference-free communication. Previous work has attempted to understand the interference immunity of FAMA but the results are limited to simplified spatial correlation models. In this paper, we revisit the FAMA system with only two users by characterizing the joint spatial correlation amongst all the ports. Using this model, however, the number of variables determining each channel coefficient scales with that of ports, hence making the analysis intractable. To tackle this, we first show that the channel model could be considerably simplified by taking into account only a few variables, and then derive the outage probability for the considered FAMA system by using the approximated model. Simulation results show that the simplified channel model can quickly approach the exact one and that the outage probability decreases with the number of ports but has an error floor unless the size of fluid antenna is increased.

Abstract Using reconfigurable fluid antennas, it is possible to have a software‐controlled position‐tuneable antenna to realize spatial diversity and multiplexing gains that are previously only possible using multiple antennas. Recent results illustrated that fast fluid antenna multiple access ( f ‐FAMA) which always tunes the antenna to the position for maximum signal‐to‐interference ratio (SIR) on a symbol‐by‐symbol basis, could support hundreds of users on the same radio channel, all by a single fluid antenna at each user without complex coordination and optimization. The network outage rate, nevertheless, depends on the SIR threshold chosen for each user. Motivated by this, this paper adopts a first‐order approximation to obtain the outage probability expression from which a closed‐form solution is derived for optimizing the SIR threshold in maximizing the network outage rate. Moreover, a closed‐form expression is provided to estimate the number of users in the f ‐FAMA network in which the outage rate begins to plateau. Numerical results show that the proposed SIR threshold achieves near‐maximal outage rate performance.

Fluid antennas offer a novel way to achieve massive connectivity by enabling each user to find a ‘port’ in space where the instantaneous interference undergoes a deep null for multiple access. While this unprecedented capability permits hundreds of users to share the same radio channel, each user needs to switch its best port on a symbol-by-symbol basis, which is impractical. Motivated by this, this paper considers the scenario in which the fluid antenna of each user updates its best port only if the fading channel changes. We refer to this approach asslowfluid antenna multiple access ($s$-FAMA). In this paper, we first investigate the interference immunity of$s$-FAMA through analyzing the outage probability. Then an outage probability upper bound is obtained, from which we shed light on the achievable multiplexing gain of the system and unpack the impacts of various system parameters on the performance. Numerical results reveal that despite having a weaker multiplexing power than the symbol-based,fastFAMA (i.e.,$f$-FAMA), spatial multiplexing of 4 users or more is possible if the users’ fluid antennas have large numbers of ports.

Multiple access can be realized by utilizing the spatial moments of deep fades, using fluid antennas. The interference immunity for fluid antenna multiple access (FAMA), nevertheless, comes with the requirement of a large number of ports at each user. To alleviate this, we study the synergy between opportunistic scheduling and FAMA. A large pool of users permits selection of favourable users for FAMA and decreases the outage probability at each selected user. Our objective is to characterize the benefits of opportunistic scheduling in FAMA. In particular, we derive the multiplexing gain of the opportunistic FAMA network in closed form and upper bound the required number of users in the pool to achieve a given multiplexing gain. Also, we find a lower bound on the required outage probability at each user for achieving a given network multiplexing gain, from which the advantage of opportunistic scheduling is illustrated. In addition, we investigate the rate of increase of the multiplexing gain with respect to the number of users in the pool, and derive a tight approximation to the multiplexing gain, expressed in closed form. As a key result of our analysis, we obtain an operating condition on the product of the number of users in the pool and the number of ports at each fluid antenna that ensures a high multiplexing gain. Numerical results demonstrate clear benefits of opportunistic scheduling in FAMA networks, and corroborate our analytical results.

Due to the exceedingly high integration density of VLSI circuits and the resulting high power density, thermal integrity became a major challenge. One way to tackle this problem is Dark silicon. Dark silicon is the amount of circuitry in a chip that is forced to switch off to insure thermal integrity of the system and prevent permanent thermal-related faults. In many-core systems, the presence of Dark Silicon adds new design constraints, in general, and on the communication fabric of such systems, in particular. This is due to the fact that system-level thermal-management systems tend to increase the distance between high activity cores to insure better thermal balancing and integrity. Consequently, a designing dilemma is created where a compromise has to be made between interconnect performance and power consumption. This study proposes a hybrid wire and surface-wave interconnect (SWI) based Network-on-Chip (NoC) to address the dark silicon challenge. Through efficient utilization of one-hop cross the chip communication SWI links, the proposed architecture is able to offer an efficient and scalable communication platform in terms of performance, power, and thermal impact. As a result, evaluations of the proposed architecture compared to baseline architecture under dark silicon scenarios show reduction in maximum temperature by 15∘C, average delay up to 73.1%, and energy-saving up to ∼3X. This study explores the promising potential of the proposed architecture in extending the utilization wall for current and future many-core systems in dark silicon era.

With massive deployment, multiple-input–multiple-output (MIMO) systems continue to take mobile communications to new heights, but the ever-increasing demands mean that there is a need to look beyond MIMO and pursue the next disruptive wireless technologies. Reconfigurable intelligent surface (RIS) is widely considered a key candidate technology block to provide the next generational leap. The first part of this article provides an updated overview of the conventional reflection-based RIS technology, which complements the existing literature to include active and semiactive RIS, and the synergies with cell-free massive MIMO (CF mMIMO). Then, we widen the scope to discuss the surface-wave-assisted RIS that represents a different design dimension in utilizing metasurface technologies. This goes beyond being a passive reflector and can use the surface as an intelligent propagation medium for superb radio propagation efficiency. The third part of this article turns the attention to the fluid antenna, a novel antenna technology that enables a diverse form of reconfigurability that can combine with RIS for ultrahigh capacity, power efficiency, and scalability. This article concludes with a discussion of the potential synergies that can be exploited between MIMO, RIS, and fluid antennas.

Fluid antenna system represents an emerging technology that enables an antenna to switch its physical location in a predefined space. This paper explores the potential of using a single fluid antenna at each mobile user for multiple access, which we refer to it as fluid antenna multiple access (FAMA). FAMA exploits spatial moments of deep fade suffered by the interference to achieve a favourable channel condition for the desired signal, without requiring sophisticated signal processing. We analyze the FAMA network by first deriving the outage probability of the signal-to-interference ratio (SIR) in a double integral form. We then obtain an outage probability upper bound in closed form and an average outage rate lower bound for the FAMA system, with an arbitrary number of interferers, from which the multiplexing gain of FAMA is characterized. We also estimate how large the number of locations is required to achieve a given multiplexing gain using fluid antennas with a given size. Results show that it is possible for FAMA to support hundreds of users using only one fluid antenna of a few wavelengths of space at each user, giving rise to significant gain in the average network outage rate.

Over the past decades, multiple antenna technologies have appeared in many different forms, most notably as multiple-input multiple-output (MIMO), that have transformed wireless communications for extraordinary diversity and multiplexing gains. The various MIMO technologies have been based on placing a number of antennas at some fixed locations which dictate the fundamental limit on the achievable performance. By contrast, this paper envisages the scenario in which the physical position of an antenna can be switched freely to one of the N positions over a fixed-length line space to pick up the strongest signal in the manner of traditional selection diversity. We refer to this system as a fluid antenna system (FAS) for tremendous flexibility in its possible shape and position. The aim of this paper is to study the achievable performance of a single-antenna FAS system with a fixed length and N in arbitrarily correlated Rayleigh fading channels. Our contributions include exact and approximate closed-form expressions for the outage probability of FAS. We also derive an upper bound for the outage probability, from which it is discovered that a single-antenna FAS given any arbitrarily small space can outperform an L-antenna maximum ratio combining (MRC) system if N is large enough. Our analysis also reveals the minimum required size of the FAS, and how large N is considered enough for the FAS to surpass MRC.

Hybrid wired-wireless Network-on-Chip (WiNoC) has emerged as an alternative solution to the poor scalability and performance issues of conventional wireline NoC design for future System-on-Chip (SoC). Existing feasible wireless solution for WiNoCs in the form of millimeter wave (mm-Wave) relies on free space signal radiation which has high power dissipation with high degradation rate in the signal strength per transmission distance. Moreover, over the lossy wireless medium, combining wireless and wireline channels drastically reduces the total reliability of the communication fabric. Surface wave has been proposed as an alternative wireless technology for low power on-chip communication. With the right design considerations, the reliability and performance benefits of the surface wave channel could be extended. In this paper, we propose a surface wave communication fabric for emerging WiNoCs that is able to match the reliability of traditional wireline NoCs. First, we propose a realistic channel model which demonstrates that existing mm-Wave WiNoCs suffers from not only free-space spreading loss (FSSL) but also molecular absorption attenuation (MAA), especially at high frequency band, which reduces the reliability of the system. Consequently, we employ a carefully designed transducer and commercially available thin metal conductor coated with a low cost dielectric material to generate surface wave signals with improved transmission gain. Our experimental results demonstrate that the proposed communication fabric can achieve a 5 dB operational bandwidth of about 60 GHz around the center frequency (60 GHz). By improving the transmission reliability of wireless layer, the proposed communication fabric can improve maximum sustainable load of NoCs by an average of 20:9 and 133:3 percent compared to existing WiNoCs and wireline NoCs, respectively.

In this study, the authors investigate the error performance of the protograph (low‐density parity check) codes over Nakagami‐ m fading relay channels. The authors first calculate the decoding thresholds of the protograph codes over such channels with different fading depths (i.e. different values of m ) by exploiting the modified protograph extrinsic information transfer (PEXIT) algorithm. Furthermore, based on the PEXIT analysis and using Gaussian approximation, the authors derive the bit‐error‐rate (BER) expressions for the error‐free (EF) relaying protocol and decode‐and‐forward (DF) relaying protocol. The authors finally compare the threshold with the theoretical BER and the simulated BER results of the protograph codes. It reveals that the performance of DF protocol is approximately the same as that of EF protocol. Moreover, the theoretical BER expressions, which are shown to be reasonably consistent with the decoding thresholds and the simulated BERs, are able to evaluate the system performance and predict the decoding threshold with lower complexity as compared with the modified PEXIT algorithm. As a result, this work can facilitate the design of the protograph codes for the wireless communication systems.

This paper presents a novel technique to enable over-body propagation at 60 GHz. A flexible material has been created that enables the propagation of surface waves around the body without the need of repeaters, high powers or high gain antennas. The solution is wireless and self-redundant, and will facilitate the development of light weight, high bandwidth, and low power, wireless body area networks that could offer improvements for mobile health monitoring applications as well as utility in sports and entertainment industries.

The basic geometry of a microstrip patch antenna (MPA) consists of a metallic patch printed on a grounded substrate. Three commonly used feeding methods are coaxial feed, stripline feed, and aperture-coupled feed. The patch antenna idea was first proposed in the early 1950s, but it was not until the late 1970s that this type of antenna attracted serious attention of the antenna community. The microstrip patch antenna offers the advantages of low profile, conformability to a shaped surface, ease of fabrication, and compatibility with integrated circuit technology, but the basic geometry suffers from narrow bandwidth. In the last three decades, extensive studies have been devoted to improve the performance of this antenna and the MPA has found numerous applications in both the military and the commercial sectors. This article begins with a brief description of the modeling techniques and basic characteristics of the MPA. Methods of broadbanding, dual and multiband designs, size-reduction techniques, and design for circular polarization are then reviewed. The paper ends with some concluding remarks.