Spatial Diversity Research Articles

Wideband Circularly Polarized Two-Element MIMO Antenna with Polarization Diversity

Wideband Circularly Polarized Two-Element MIMO Antenna with Polarization Diversity

Design and analysis of a fabricated modified elliptical patch antenna with slots and partial ground plane techniques for UWB applications

This study presents a novel elliptical microstrip antenna (EMSA) design method for enhanced bandwidth. The proposed EMSA offers versatile polarization control, generating both linear and circular polarization. Wider impedance bandwidths compared to some other patch antennas make it suitable for broadband communication. Its compact size facilitates integration into space-constrained devices. Additionally, it provides polarization diversity for MIMO systems, reducing signal fading. The fabricated EMSA, operating at 7.05 GHz, achieves a simulated bandwidth of 5.7% and a measured bandwidth of 4.28%. It exhibits a return loss of -42 dB, 50 Ω impedance matching, 8.57 dB radiation gain, and a VSWR of 1.016. Two bandwidth enhancement techniques were investigated: reducing the ground plane size and incorporating slots within the patch. The partial ground plane achieved simulated and measured bandwidth improvements of 146% and 167%, respectively. The slotted patch yielded 160% and 180% improvements, respectively.

Dual data fusion fault diagnosis of transmission system based on entropy weighted multi-representation DS evidence theory and GCN

Power transmission reliability of drivelines guarantees fast maneuverability of heavy vehicles. During health monitoring, multi-sensor data fusion technology has been widely used in the improvement of fault diagnosis accuracy of long-link multi-structure drivelines. However, in multi-sensor fusion and joint fault diagnosis scenarios where multiple conditions coexist, it is still challenging to fuse multi-sensor data and extract generalized fault intrinsic features for any combination of operating conditions under multi-sensor monitoring. In this paper, a dual fusion graph convolutional network (DFGCN) is proposed for multi-sensor-multi-condition fault diagnosis of the transmission system. First, considering the data structure and the correlation of different sensors, DFGCN constructs multi-sensor intrinsic links synchronously from the data and feature levels by using multi-branch parallel GCN. Second, considering the susceptibility to over-confidence when the feature space of multi-condition data is inconsistent, an entropy-weighted multi-representation Dempster-Shafer (EWMR-DS) evidence theory fusion strategy is designed to extract the condition-shared features by increasing the label space diversity. Finally, an end-to-end lightweight diagnosis framework is scalable to multi-sensor and multi-working conditions in engineering practice, and the dual information fusion improves the fusion efficiency of fine-grained features with distributional differences. Using experimental datasets collected from two typical transmission fault test benches, the effectiveness of the proposed DFGCN method in multi-sensor-multi-condition scenarios is verified. The results indicate that DFGCN achieves an average diagnostic accuracy of more than 99.7% and superior noise resistance under different degrees of environmental noise.

Phenolic multiple kinetics-dynamics and discrete crystallization thermodynamics in amorphous carbon nanostructures for electromagnetic wave absorption

The lack of a chemical platform with high spatial dimensional diversity, coupled with the elusive multi-scale amorphous physics, significantly hinder advancements in amorphous electromagnetic wave absorption (EWA) materials. Herein, we present a synergistic engineering of phenolic multiple kinetic dynamics and discrete crystallization thermodynamics, to elucidate the origin of the dielectric properties in amorphous carbon and the cascade effect during EWA. Leveraging the scalability of phenolic synthesis, we design dozens of morphologies from the bottom up and combine with in-situ pyrolysis to establish a nanomaterial ecosystem of hundreds of amorphous carbon materials. Based on controlled discrete crystallization, nano-curvature regulation of spatial inversion symmetry-breaking structures, and surface electric field enhancement from multi-shell structures, the multi-scale charge imbalance triggers intense polarization. Both experiments and theories show that each scale is essential, which collectively drives broadband absorption (8.46 GHz) and efficient dissipation (−54.77 dB) of EWA performance. Our work on the amorphous nanostructure platform and the cascade effect can contribute to uncovering the missing pieces in amorphous physics and EWA research.

A closely spaced dual-band dual-sense linear-to-circular polarization converter for X-band applications

This paper presents a novel design of closely spaced dual-band dual-sense linear-to-circular polarization converting metasurface for X-band applications. The unit cell of the metasurface consists of a pair of L-shaped dipoles and a pair of cross-dipoles, respectively, with diagonal symmetry. The proposed linear-to-circular polarization converter (LCPC) provides a 3-dB axial ratio bandwidth (ARBW) ranging from 7.84 to 9.08 GHz (14.65%) for the lower band, and from 10.89 to 12.94 GHz (17.11%) for the upper band. The two frequency bands are in close proximity to each other, with a calculated separation bandwidth of 33.95%. Moreover, the proposed metasurface provides dual-sense operation, enabling polarization conversion to left-hand circular polarization (LHCP) in the lower band and right-hand circular polarization (RHCP) in the upper band for a y-polarized incidence wave and vice versa for an x-polarized incidence wave, respectively. These characteristics hold significant importance in different applications, such as satellite communication, that demand polarization diversity. After numerical analysis based on full-wave simulations, the proposed converter is fabricated and measured. A good agreement is observed between the full-wave simulated and measurement results.

Spatial and Temporal Diversity of Fishes at Wuzhizhou Island in the South China Sea Based on Environmental DNA

Spatial and Temporal Diversity of Fishes at Wuzhizhou Island in the South China Sea Based on Environmental DNA

Multiyear genotype characterization of eastern spruce budworm outbreaking populations from Quebec and adjacent regions.

Population outbreaks are characterized by irruptive changes in population density and connectivity resulting in rapid demographic and spatial expansion, often at the landscape scale. Outbreaks are common across multiple taxa, many of which inhabit northern ecosystems. Outbreaks of Lepidopteran defoliators in forest ecosystems are a particularly compelling example of this phenomenon, given the massive spatial scales over which these outbreaks can occur, their frequency, and socioeconomic impacts. The eastern spruce budworm (SBW) is a native outbreaking Lepidopteran defoliator of North American boreal forests. Cyclic outbreaks of the SBW influence ecosystem functioning and resilience, as well as forest productivity, timber supply, and other socioeconomic values related to management and mitigation. Despite these significant impacts, the ecological and biological drivers and outcomes of these outbreaks remain poorly understood. Here, we present an extensive genotypic dataset for 1998 geo-referenced SBW individuals collected between the years of 2012 and 2017, during the rising and peak phases of an outbreak that began approximately in 2006. Our sampling covers an unprecedented scope in the extent and number of individuals collected between 2012 and 2017 from Quebec, and in 2015 from New Brunswick (Canada) and from Maine (USA), from multiple SBW life stages, including early and late instar larvae (L2-L6), pupae, and adult moths. Genomic DNA extraction was followed by library preparation and high-throughput sequencing using Genotyping-by-Sequencing (GBS). Samples were genotyped for single nucleotide polymorphisms (SNPs) and aligned to the bw6 version of the SBW genome. This dataset represents one of the most extensive genotypic datasets to date for a boreal insect and is unique as it includes multiple years during a developing (ongoing, at time of sampling) outbreak. Sampling effort covered areas close to the epicenter of the outbreak (Quebec/Canada) and adjacent areas affected by the outbreak progress. This dataset also provides genome-wide characterization of SBW populations from Quebec, serving as a standard for the identification of future samples regarding their locality of origin, structure and connectivity. These data represent a valuable novel resource for further study of the spatial and temporal dynamics of SBW, and how spatial genetic diversity and gene flow are affected by population outbreaks. These data provide a temporal snapshot of SBW genetic diversity, which can serve as baseline for future studies regarding outbreaks, and the impact of human-induced environmental changes on complex population dynamics. This genotype dataset comprises a unique representation of genomic-level composition and variation observed in subsequent generations of an irruptive, cyclic outbreaking species and is of utmost importance for exploring and describing how accelerated demographic variation impacts the development of spatial genetic structure across heterogeneous landscapes. We believe this dataset is essential to management and conservation biology initiatives not only for SBW and boreal forests but also for providing a starting point for broader evolutionary and ecological studies of complex population dynamics. Furthermore, the knowledge, data collection, and curation framework we present here can be used to inform similar spatial temporal baseline studies of other outbreaking (e.g., mountain pine beetle, red-backed voles) and invasive species (e.g., spongy moth and emerald ash borer). The data are released under a CC BY 4.0 license.

Cross‐scale scaling‐law analyses for the heterogeneity and diversity of animal gut microbiomes from community to landscape

Diversity and heterogeneity often are conflated but are fundamentally different. An aphorism proposed by Shavit and Ellison (2021; J. Phil. 118: 525–548) for distinguishing them is that ‘a zoo is diverse whereas an ecosystem is heterogeneous.' That is, a zookeeper measuring diversity simply enumerates the different types of animals; interactions are not expected to occur between animals separated by fences or other barriers. In contrast, measures of heterogeneity ought to include both interspecific interactions and relationships between species and their heterogeneous habitats. Here, we use cross‐scale, dual scaling‐law analyses of heterogeneity and diversity of animal gut microbiomes (AGMs) to address three objectives: 1) estimate the spatial heterogeneity and diversity of animal‐gut microbiomes; 2) analyze influences of phylogeny and diets on scaling of diversity and heterogeneity; 3) explore mechanistic differences between diversity and heterogeneity in AGMs. From 4903 AGM samples collected from 318 animal species covering all six classes of vertebrates and four major classes of invertebrates, we estimated that ≈640 000 operational taxonomic units (OTUs or ‘species') make up the pool of microbial species that could inhabit animal guts, among which ≈8000 are relatively common and ≈800 are dominant. The gut of any single animal, however, includes only 0.01–0.5% of the total species pool. We applied Ma's diversity‐area relationship for scaling diversity, and extend Taylor's power law and Luna et al.'s (2020; Diversity 12: 86) interaction diversity for scaling heterogeneity. At the community scale, phylogeny significantly influenced heterogeneity, but diets did not. Phylogeny and diets had limited influence on diversity at both community and landscape scales. We demonstrated that diversity and heterogeneity measure two different properties. Further, differences in scaling of diversity and heterogeneity are a result of heterogeneity being primarily the result of evolved dispersal behavior and interspecific interactions, whereas diversity results from abundances controlled on ecological time scales.

Probe Capture Enrichment Sequencing of amoA Genes Improves the Detection of Diverse Ammonia‐Oxidising Archaeal and Bacterial Populations

ABSTRACTThe ammonia monooxygenase subunit A (amoA) gene has been used to investigate the phylogenetic diversity, spatial distribution and activity of ammonia‐oxidising archaeal (AOA) and bacterial (AOB), which contribute significantly to the nitrogen cycle in various ecosystems. Amplicon sequencing of amoA is a widely used method; however, it produces inaccurate results owing to the lack of a ‘universal’ primer set. Moreover, currently available primer sets suffer from amplification biases, which can lead to severe misinterpretation. Although shotgun metagenomic and metatranscriptomic analyses are alternative approaches without amplification bias, the low abundance of target genes in heterogeneous environmental DNA restricts a comprehensive analysis to a realisable sequencing depth. In this study, we developed a probe set and bioinformatics workflow for amoA enrichment sequencing using a hybridisation capture technique. Using metagenomic mock community samples, our approach effectively enriched amoA genes with low compositional changes, outperforming amplification and meta‐omics sequencing analyses. Following the analysis of metatranscriptomic marine samples, we predicted 80 operational taxonomic units (OTUs) assigned to either AOA or AOB, of which 30 OTUs were unidentified using simple metatranscriptomic or amoA gene amplicon sequencing. Mapped read ratios to all the detected OTUs were significantly higher for the capture samples (50.4 ± 27.2%) than for non‐capture samples (0.05 ± 0.02%), demonstrating the high enrichment efficiency of the method. The analysis also revealed the spatial diversity of AOA ecotypes with high sensitivity and phylogenetic resolution, which are difficult to examine using conventional approaches.

Joint DOA and distance estimation via spatial diversity wideband signal synthesis calibrated by distance parameter

Wideband signal synthesis is a technique designed to achieve large bandwidth detection capabilities by utilizing multiple relatively narrow bandwidth signals. Traditional single-antenna, time-diversity wideband synthesis method is inefficient, which has led to using Multiple-Input Multiple-Output (MIMO) architectures to introduce spatial diversity. However, this method introduces challenges such as frequency-phase inconsistencies in the self-mixing signals from different array elements due to differences in wave travel distances. In previous research, we studied the calibration of frequency and phase for synthesized sub-signals using DOA parameters, which required additional high-precision direction of arrival (DOA) estimation algorithms. In contrast, this paper proposes a novel spatial-diversity wideband synthesis method that utilizes distance parameter calibration for joint DOA and distance estimation (JDDE). A key advantage of this method is the relative simplicity of obtaining distance parameters. To address the issue where the accuracy of distance parameters does not meet the requirements for synthesis, we proposed a grid search synthesis method in this paper. Furthermore, we introduced a search synthesis based on optimization algorithms to reduce computational load and enhance the synthesis performance. Theoretical analysis and simulations confirm the high accuracy of our JDDE method. Under conditions of high signal-to-noise ratios, our method significantly reduces the DOA's root mean square error—approximately halving it compared to the multiple signal classification algorithm within the same wideband self-mixing framework. Additionally, both distance resolution and range accuracy exceed those achieved with pre-synthesis methods.

Illumination diversity in multiwavelength extreme ultraviolet ptychography

With the development of high harmonic generation (HHG), lensless extreme-ultraviolet (XUV) imaging at nanoscale resolution has become possible with table-top systems. Specifically, ptychographic phase retrieval using monochromatic XUV illumination exhibits extraordinary robustness and accuracy to computationally reconstruct the object and the illumination beam profile. In ptychography, using structured illumination has been shown to improve reconstruction robustness and image resolution by enhancing high spatial-frequency diffraction. However, broadband imaging has remained challenging, as the required multiwavelength algorithms become increasingly demanding. One major aspect is the ability to separate the available information into different physically meaningful states, such as different spectral components. Here, we show that introducing spatial diversity between spectral components of an HHG beam can significantly improve the reconstruction quality in multiwavelength XUV ptychography. We quantify the diversity in the polychromatic illumination by analyzing the diffraction patterns using established geometry- and information-theory-based dissimilarity metrics. We experimentally verify the major influence of diversity by comparing ptychography measurements using HHG beams with Gaussian and binary structured profiles as well as with beams carrying wavelength-dependent orbital angular momentum. Our results demonstrate how structured illumination acts in twofold by separating the spectral information in a single diffraction pattern while providing maximized added information with every new scan position. We anticipate our work to be a starting point for high-fidelity polychromatic imaging of next-generation nanostructured devices at XUV and soft-X-ray wavelengths.

UOWC spatial diversity techniques over hostile maritime environments: an approach under imperfect CSI and per-source power constraints

Optical communication in submarine environments has emerged as a novel technology that enables high bandwidth and high data rate links. However, the unique characteristics of the underwater channel impose new challenges, such as mitigating the remarkable absorption and scattering of hostile maritime environments. For the first time, we consider a per-source optical power constraint based on eye-safety regulations, which has never before been taken into account in Multiple-Input/Single-Output (MISO) systems within underwater optical wireless communication (UOWC) scenarios. Hence, we introduce an innovative spatial repetition coding (SRC) system model, which enables the analysis of an SRC scheme operating under either a per-source or a per-transmitter power constraint. In addition, a tractable generalized transmit laser selection (GTLS) model is presented in order to consider the impact of erroneous selections of the best laser source due to imperfect channel state information (CSI) at the transmitter, prevalent in underwater scenarios with dynamic fluctuations from water currents. Novel bit error rate closed-form expressions and asymptotic results are derived. The presented results demonstrate that an SRC system, when appropriately designed under a per-source power constraint, outperforms the TLS system by effectively mitigating the adverse effects of underwater links. Conversely, in situations where compact transmitters necessitate constraints that significantly modify eye-safety, TLS schemes are superior.

Characterisation and synchronisation of a netted software defined radio radar

AbstractThe present work intends to characterise the combination of two netted software defined radios (SDR) and different radio frequency (RF) front‐ends installed in them, together with a two‐stratum time dissemination and synchronisation system. A modified implementation of the Network Time Protocol is used as coarse event synchronisation for either SDR back‐end. The White rabbit light embedded node implementation of the commonly known white rabbit synchronisation system (IEEE 1588 PTP‐2019) or arbitrary wave form generators are used as fine time dissemination system for either SDR. The resulting netted transceiver system is intended to compose a demonstrator for proof‐of‐concept experiments. The findings presented in this article show that the chosen combination of hardware and software is suitable for radar applications operating within L‐, S‐ and C‐bands. A channel coherency throughout the network with a relative modified Allan deviation of less than 80 fs for averaging intervals of 1 s, a phase noise better than −118 dBc/Hz at 10 Hz frequency offset and a fractional frequency lower than was measured. Within a single transceiver node, a fractional frequency lower than and phase noise of −124 dBc/Hz at 10 Hz frequency offset were measured as well. Multistatic radar systems exploit wide spatial diversity to enhance target detection and tracking, albeit with increased complexity when compared to a monostatic configuration. To exploit these benefits, all participating transceiver nodes within the netted radar need to synchronise to a common time base . The achieved synchronisation level increases the accuracy with which the chain of timed events at the transmitter and at the receiver side occur, intending to maximise the signal‐to‐noise ratio available at the receiver. The Universal software radio peripheral model X310 with two different daughterboard models as RF front‐end was used as SDR on either radar node. A network combining data and synchronisation purposes allowed the radar nodes under test to operate synchronously. The two‐stratum synchronisation system used glass fibres between 2 m and 5 km of length or coaxial cables with 2 m in length for network traffic, time and frequency dissemination purposes. The multiple RF front‐ends were stimulated by means of arbitrary waveform generators with calibrated traceability. Up‐chirp and sinusoid waveforms were used as stimuli for measuring the offset of either channel with regards of to ultimately estimate the achievable coherency limits of the system under test. Both analogue and digital evaluation methods were considered.

Simultaneous seasonal dry/wet signals in eastern and central Asia since the Last Glacial Maximum

Abstract. The East Asian monsoon region with the summer precipitation regime and the Mediterranean climate region with the winter precipitation regime show opposite dry/wet changes since the Last Glacial Maximum (LGM). Therefore, different precipitation regimes bring about the opposing changes in dry/wet states between eastern and central Asia (EA and CA). Based on a comprehensive study of modern observational datasets, ensemble simulations of eight climate models from the Paleoclimate Modeling Intercomparison Project phase 3 (PMIP3), and a compilation of 42 proxy records from EA and CA, here we assess the relationship of seasonal precipitation signals involving rain and heat periods and the difference and linkage in dry/wet states from EA and CA. At short-term timescales, empirical orthogonal function (EOF) analysis results of mean annual precipitation show the spatial diversity of overall precipitation patterns in EA and CA. However, EOF results of summer and winter precipitation indicate a similarity between EA and the east of CA, suggesting that seasonal signals of precipitation affected by the Asian monsoon, westerlies, ENSO, the North Atlantic Oscillation (NAO), and the Pacific Decadal Oscillation (PDO) are the primary factors causing the linkage in dry/wet states. At long-term timescales, reconstructed dry/wet states from proxy records since the LGM reveal a parallel evolution in EA and the east of CA as well. A visual inspection from PMIP3 multi-model simulations in summer and winter shows that the insolation in different seasons controls the intensity of westerlies and summer monsoon and further influences the summer and winter precipitation in EA and CA since the LGM. Overall, we suggest, in addition to the traditional difference caused by different precipitation regimes, that dry/wet states in EA and CA universally have inter-regional connections affected by seasonal signals of precipitation at multiple timescales.

A Compact Planar MIMO Inverted‐F Antenna (PIFA) for Sub‐6 GHz 5G Communication and IoT Wireless Networks Applications

ABSTRACTA compact eight‐port MIMO structure containing planar inverted‐F antennas (PIFAs) as radiating elements is designed for 5G cellular communication applications within the sub‐6 GHz band. The proposed antenna consists of four radiating elements that are placed at four corners on the same plane of geometry. The overall dimension of the ground plane is considered to be 59 mm × 120 mm to make it convenient for modern smart mobile handsets. Each radiating element has 2‐feeding plates, which are situated perpendicular to each other in orientation to make the arrangement cross‐polarized, which in turn exploits polarization diversity as well as spatial diversity among the combination of different radiating elements. The patches are structured by embedding rectangular slots in a meandered shape, and the ground plane is configured by introducing rectangular slots and narrow metallic strips. The prototype of the prescribed MIMO PIFA model has been fabricated and experimentally tested. It shows multi‐band operations (3.27–3.37, 4.16–4.35, 4.93–5.06, and 5.47–5.68 GHz) within the sub‐6 GHz spectrum. The isolation among various patches is observed within the range of −35 dB to −42 dB. The peak gain reaches around 8.1 dBi. The designed MIMO PIFA exhibits superior diversity performance by producing ECC ≤ 0.0006, DG ≈ 10 dB, CCL < 0.20 bits/Hz/s, and MEG ≤ −3 dB. Furthermore, the specific absorption rate (SAR) is evaluated according to the standard values of fat, skin, and muscle at 3.3 GHz. The prescribed model maintains acceptable SAR values for 1‐g and 10‐g tissues, which makes it suitable for smartphone applications.

On-Body Cavity-Backed Slot Antenna With Pattern and Polarization Diversity for Medical Imaging

On-Body Cavity-Backed Slot Antenna With Pattern and Polarization Diversity for Medical Imaging

Identifying and filling critical knowledge gaps can optimize financial viability of blue carbon projects in tidal wetlands

One of the world’s largest “blue carbon” ecosystems, Louisiana’s tidal wetlands on the US Gulf of Mexico coast, is rapidly being lost. Louisiana’s strong legal, regulatory, and monitoring framework, developed for one of the world’s largest tidal wetland systems, provides an opportunity for a programmatic approach to blue carbon accreditation to support restoration of these ecologically and economically important tidal wetlands. Louisiana’s coastal wetlands span ∼1.4 million ha and accumulate 5.5–7.3 Tg yr−1 of blue carbon (organic carbon), ∼6%–8% of tidal marsh blue carbon accumulation globally. Louisiana has a favorable governance framework to advance blue carbon accreditation, due to centralized restoration planning, long term coastal monitoring, and strong legal and regulatory frameworks around carbon. Additional restoration efforts, planned through Louisiana’s Coastal Master Plan, over 50 years are projected to create, or avoid loss of, up to 81,000 ha of wetland. Current restoration funding, primarily from Deepwater Horizon oil spill settlements, will be fully committed by the early 2030s and additional funding sources are required. Existing accreditation methodologies have not been successfully applied to coastal Louisiana’s ecosystem restoration approaches or herbaceous tidal wetland types. Achieving financial viability for accreditation of these restoration and wetland types will require expanded application of existing blue carbon crediting methodologies. It will also require expanded approaches for predicting the future landscape without restoration, such as numerical modeling, to be validated. Additional methodologies (and/or standards) would have many common elements with those currently available but may be beneficial, depending on the goals and needs of both the state of Louisiana and potential purchasers of Louisiana tidal wetland carbon credits. This study identified twenty targeted needs that will address data and knowledge gaps to maximize financial viability of blue carbon accreditation for Louisiana’s tidal wetlands. Knowledge needs were identified in five categories: legislative and policy, accreditation methodologies and standards, soil carbon flux, methane flux, and lateral carbon flux. Due to the large spatial scale and diversity of tidal wetlands, it is expected that progress in coastal Louisiana has high potential to be generalized to similar wetland ecosystems across the northern Gulf of Mexico and globally.

High-performance and scalable polarization splitter-rotator based on photonic crystal nanobeam reflection.

The polarization splitter-rotator (PSR) is a key device for polarization processing in polarization diversity systems, which has wide applications in achieving polarization independence and mixed multiplexing. However, it remains a significant challenge to simultaneously achieve a better balance in bandwidth, crosstalk (CT), polarization extinction ratio (PER), and compact footprint of the PSR. In this article, a photonic crystal nanobeam (PCN) structure is introduced to PSR for large bandwidth and compact size, with a device length of only 104 µm. Additionally, to achieve lower CT, a bridge waveguide is introduced for primary filtering. Simulation results show that the insertion loss (IL) is less than 0.55 dB, CT less than -35 dB, and PER greater than 35 dB within a bandwidth exceeding 110 nm, while maintaining a large process tolerance. Furthermore, the proposed PSR design breaks through the limitations of traditional schemes by extending its functionality effectively. To further improve integration, a novel approach to PSR using mode hybridization followed by spatial beam splitting is proposed. By controlling the phase-matching condition of various modes in different waveguides, the designed spatial beam splitting achieves lower CT and better compactness. Simulation results verify that the IL of the improved scheme is less than 1 dB, CT less than -24 dB, and PER greater than 22 dB within an 85 nm bandwidth, while reducing the overall length to less than 20 µm.

Dynamic output feedback model predictive control for polytopic uncertain systems under decode and forward cooperative relay protocol

This paper addresses the robust model predictive control (RMPC) problem for a class of polytopic uncertain systems under the decode and forward cooperative relay protocol (DFCP). In order to combat signal fading from sensors to controllers and improve communication reliability, spatial diversity is achieved through cooperative terminal relay signals. At each transmission instant, the terminal only selects a better signal for transmission and a switched system is constructed. The aim of this paper is to design a set of desired dynamic output feedback controllers in the framework of RMPC such that the switched system with the underlying DFCP is exponentially stable. By taking the influence of the randomness of DFCP derived from a three nodes model composed of DF relay, a new objective function based on the mathematical expectation of the traditional quadratic function of MPC is established. Then, the orthogonal complement technique is applied to handle the inherent couplings of variables to formulate a solvable optimisation problem. Moreover, the sufficient conditions are provided to guarantee the recursive feasibility of the MPC strategy and the stability of the established closed-loop system in terms of the average dwell time (ADT) method. Finally, three experiments are given to illustrate the effectiveness of the proposed method.

Simultaneous Integration of Pattern, Frequency and Polarization Diversities in Broadband Programmable Metasurface for Computational Imaging

Simultaneous Integration of Pattern, Frequency and Polarization Diversities in Broadband Programmable Metasurface for Computational Imaging