Search

In NOMA achieving fairness in data transmission for all users is one of the key challenges. It implies a fair allocation of resources among users according to a given criterion. NOMA systems are based on the discreteness of the data source, since the specific nature of data allows to extract information in overloaded systems. Well-known C.E. Shannon capacity equation does not take into account the discrete nature of NOMA group signals, considering them as Gaussian source of information. Therefore, it does not take into account the characteristics of discrete signals used in NOMA systems, which makes it difficult to solve the optimization problem, especially for types of NOMA that use code division. For this task it is necessary to use DCMC capacity. When optimizing total capacity of DCMC, individual properties of users are not taken into account, as a result of which the allocation of resources with such optimization might not be fair. This paper proposes an approach to optimizing NOMA based on the analysis of an-individual mutual information (capacity). The proposed optimization approach allows analyzing the individual characteristics of each user in order to improve NOMA system performance by optimizing NOMA signals parameters. [ABSTRACT FROM AUTHOR]

Summary: The increasing prevalence of MIMO technology in wireless communication networks is attributed to its ability to augment system capacity and dependability. Consequently, there is a notable enthusiasm for the advancement and implementation of S‐band applications. Nevertheless, the mutual coupling between numerous antennas presents a crucial obstacle to MIMO system performance. This paper presents a novel technique that utilizes a defective ground structure with parasitic components to increase antenna isolation and gain. Additionally, an L‐shaped slot is incorporated into the patch element to enhance the antennas impedance bandwidth. Antennas are intentionally placed in a perpendicular arrangement to minimize the impact of the coupling effects. The antenna exhibits an impedance bandwidth in the frequency range of 2.62–2.79 GHz. Furthermore, the utilization of a four‐element MIMO antenna setup with a defective ground structure yields outstanding isolation properties, with values notably lower than −25 dB. To achieve an optimal MIMO performance, we assessed various diversity parameters, including diversity gain, channel capacity loss, total active reflection coefficient, and envelope correlation coefficient. The parameter values were within acceptable limits (ECC < 0.04, DG = 10 dB, TARC < 0 dB, and CCL < 0.1 bits/s/Hz). This research paper therefore offers essential insights into the design and optimization of MIMO antennas specifically for 2.7 GHz applications. [ABSTRACT FROM AUTHOR]

This work presents a knowledge-based decision-making robust antenna design (KDRAD) method that employs a heuristic-optimisation technique for antenna design. The method is used to create and scale a single-element antenna to operate at multiple frequencies within the 5 G range. In this study, a low-profile planar four-element microstrip antenna of 14.8 mm × 14.8 mm × 0.508 mm gives simulated and measured impedance bandwidths of about 1.18 GHz (26.43–27.61 GHz) and 1.08 GHz (26.42–27.50 GHz), respectively, with a centre frequency of 27 GHz. The mm-wave planar four-port antenna has a maximum gain of 7.2 dBi; isolation of 33.2 dB; and multiple antenna matrices with minimal ECC (0.000000109), high diversity gain (10 dB) and channel capacity loss of 0.00110 bits/s/Hz. [ABSTRACT FROM AUTHOR]

The single-input-single-output technology experiences loss of data in the communication channel due to the receiving antenna undergoing fading of the signal impinged on it. Today's need is faster data transfer with multiple applications in the single antenna with multiple-identical radiating elements, leading to multiple-input-multiple-outputDWMB (MIMODWMB) technology. The MIMODWMB configuration with multi-band capability is the objective of the proposed work with applications ranging between microwave-millimeterWave bands. The four-port Dual-Wide Multi-Band (DWMB) MIMODWMB antenna radiating electro-magnetic-energy is proposed, which generates measured bandwidths of 7.27GHz-34.32GHz (Band 1) and 46.54GHz-71.52GHz (Band 2) including applications Up-link/Down-link Satellite System, X-Band, Ku-Band, ISM 24.0GHz (24.0GHz-24.25GHz), 24.0GHz UWB Band (21.65GHz-26.65GHz), n258, n257/n261 and n263 V-band. The proposed antenna technology is printed on Rogers's low permittivity substrate with a hexagon patch etched with dual merged-elliptical slot and three identical circular slots to achieve high impedance matching for Band 1. The partial-ground is etched by a rectangular slot for better impedance matching, and two-thin-etched rectangular slits generate 60.0GHz Band 2. The thin substrate, thickness 0.254mm, is utilized for flexible applications without compromising the operation of dual wide bandwidths. The flexible antenna is also subjected to analysis of Specific-Absorption-Rate (SAR) analysis at key frequencies within both the bands and found to be within the standard limit of 1.60W/Kg for 1g of the human tissue model and corresponds to 1.01W/Kg at 10.0GHz, 0.280W/Kg at 15.0GHz, 0.475W/Kg at 26.0GHz, 0.588W/Kg at 28.0GHz & 0.301W/Kg at 60.0GHz. The high diversity performance with Envelope Correlation Coefficient<0.50, Diversity Gain≈10.0dB, Total Active Reflection Coefficent<0dB, Channel Capacity Loss<0.40b/s/Hz and multi-band capability for mobile users make the proposed work suitable for flexible on-body applications in a wireless environment. The proposed work MIMODWMB antenna offers advantages such as reduced size (20mm×24mm: 0.61λ0×0.74λ0 at λ0 = 7.27GHz) and a wide range of impedance bandwidths, which are useful for several applications. Also, due to the flexible nature of the design, they can be used for future on-body wearable applications. [ABSTRACT FROM AUTHOR]

This research work presents the design of a multiband dual‐polarized eight‐element MIMO antenna having dimensions (0.51 λ × 0.66 λ × 0.009 λ). The antenna is observed to be radiating between 1.7 GHz and 2.4 GHz, 4.1 GHz and 10 GHz and 10.6 GHz and 19.8 GHz, featuring 3 dB axial ratio bandwidth between 9.7 and 10 GHz, 12.1 and 13.1 GHz, 14.4 and 14.5 GHz and 17.9 and 18.9 GHz. In the proposed MIMO antenna, the triangular‐shaped monopole antenna is tapered at its two sides. The isolation between the various elements of the proposed antenna is observed to be in range of −20 dB–−70 dB for the concerned frequency range. On the basis of comparison with similar existing structures, the proposed antenna demonstrates superior performance in terms of total active reflection coefficient (TARC < −5 dB), diversity gain (DG around 10 dB), channel capacity loss (CCL < 0.3 bits/s/Hz), mean effective gain (MEG) and envelope correlation coefficient (ECC < 0.024). The proposed antenna provides wide bandwidth (15.8 GHz) and high value of peak gain (6 dB). The proposed geometry is novel as it exhibits both linear as well as circular polarization with multiband response and it provides the least ECC and maximum isolation. The experimental results are found to be in agreement with the simulated results, so the proposed antenna can be useful for WLAN, C‐band, X band and Ku band applications. [ABSTRACT FROM AUTHOR]

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A distributed multiple‐input multiple‐output (MIMO) dual‐function radar‐communication (D‐MIMO DFRC) system is composed of multiple distributed dual‐function transmitters, multiple radar receivers and multiple communication receivers, which is capable of performing communication and radar tasks simultaneously. In a DFRC system, the goal is on optimising both the sum ‐rate in communication receivers and detection/localisation performance in radar receivers. The secrecy rate is maximised in D‐MIMO DFRC systems by decreasing the eavesdropper data rate as much as possible with a two‐step antenna selection method while maintaining optimal radar performance. In the first step of the proposed method, all transmitter antennas have been classified into groups based on their distance from each other, and each group is called a cluster. Then, a cluster of distributed transmitter antennas is selected based on path fading effects. In the second step of this method, the antenna selection algorithm is performed in the pre‐selected cluster based on channel capacity information utilising QR decomposition. The results show that this antenna selection method, along with low computational complexity and high performance, leads to the maximisation of the secrecy rate. In DFRC systems, it is desirable to minimise the total transmit power while satisfying system requirements to provide low probability of interception (LPI). Finally, after antenna selection, a power allocation strategy is also applied on the selected antennas to optimise the total transmit power and to maximise throughput in communication radar receivers simultaneously, and as a result it leads to provide LPI. [ABSTRACT FROM AUTHOR]

In today's modern and globalized world, connectivity is a key factor for businesses, production facilities, sensor networks, and ordinary people. However, there are still populated areas which are not covered by ground-based telecommunications infrastructure. This is where telecommunication satellite constellations come in, as they can provide coverage to remote and uninhabited regions and fill existing connectivity gaps to ensure data transfer. LoRa is one of the technologies designed for data transmissions over long distances with low power consumption. Alongside with other technologies of the Low-Power Wide Area Network family, it is widely used for Internet of Things applications. LoRa chirp spread spectrum modulation is robust against the Doppler frequency shifts encountered in low earth orbits, and it has already been used in IoT satellite communications. Due to the low transmitted signal power, the achieved data rate is not high, making it a suitable technology for telecommunications payloads on CubeSat platforms for messaging services. As compared to existing traditional communication satellite systems, CubeSat constellations are low-cost and may offer an affordable connectivity service to developing regions. This study is divided in two parts. In Part I the demand model is built based on the population distribution not covered by cell towers. The LoRa link performance is analyzed, considering the impact of LoRa channel parameters variation, such as spreading factor and channel bandwidth, while satellite orbital height, transmission antenna beamwidth, and transmitter peak power have a direct impact on the payload mass. Among thousands of possible configurations, 73 feasible payload designs have been downselected. In Part II of the study, the satellite mass and the total system cost are estimated based on the payload parameters obtained. Messages transmission simulation via a constellation is conducted in order to identify optimal constellation architectures for messaging service, as well as the main drivers of the system economic profitability. The presented analysis results provide a deeper understanding of LoRa connectivity advantages and limitations together with the performance drivers, which will support the optimization of future LoRa-based satellite communication systems and other IoT satellite constellations. • A general framework for communications satellite constellation is suggested. • LoRa technology feasibility for messaging service via satellites has been proved. • LoRa channel capacity is sufficient for 1 message per day per uncovered user. • SF drives achievable channel capacity, orbit height and antenna beamwidth. • 73 payloads were downselected, with 2x2-8x8 patch antennas and transceivers of 1-2W. [ABSTRACT FROM AUTHOR]

Modern wireless communication systems have undergone a radical change with the introduction of multiple-input multiple-output (MIMO) antennas, which provide increased channel capacity, fast data rates, and secure connections. To achieve real-time requirements, such antenna technology needs to have good gains, wider bandwidths, satisfactory radiation characteristics, and high isolation. This article presents an eight-element CPW-fed antenna for the 5G mid-band. The proposed antenna consists of eight symmetrical, modified circular monopole antennas with a connected CPW-fed ground plane that offers 24 dB isolation over the operating range. The antenna is further investigated in terms of the scattering parameters, and radiation characteristics under both the x and y-axis bending scenarios. The antenna holds a volume of 83 × 129 × 0.1 mm3 and covers a measured impedance bandwidth of 4.5–5.5 GHz (20%) with an average gain of 4 dBi throughout the operating band. MIMO diversity performance of the antenna is performed, and the antenna exhibits good performance suitable for MIMO applications. Furthermore, the channel capacity (CC) is estimated, and the antenna gives a value of 41.8–42.6 bps/Hz within the operating bandwidth, which is very close to an ideal 8 × 8 MIMO system. The antenna shows an excellent match between the simulated and measured findings. [ABSTRACT FROM AUTHOR]

This paper introduces a 4-port antenna tailored for 5G, operating in the 4.4 to 7.25 GHz (Fractional Bandwidth is 48.9%) range with a 10 dB impedance bandwidth. The operating bandwidth includes the n79 band (4.4–5 GHz), 5G WLAN band (5.125–5.825 GHz), and Wi-Fi 6E band (5.925 to 7.125 GHz). Constructed on a compact FR4 substrate (0.057λ × 0.057λ × 0.0018λ (where λ is the wavelength at 4.4 GHz), it exhibits robust performance in fabrication and measurements. The single antenna covers a total area as small as 20×17.6 mm², which enables the compactness of the MIMO antenna with a gain of up to 6 dBi and 85% radiation efficiency; it supports MIMO with a low correlation coefficient (< 0.02), high diversity gain (up to 9.98 dB), and minimal channel capacity loss (0.25 bps/Hz). The Total Active Reflective Coefficient (TARC) is computed to validate MIMO performance over the operating bandwidth. Featuring bidirectional radiation patterns in both E-plane and H-plane, the antenna is well suited for 5G applications, demonstrating potential for future wireless systems. [ABSTRACT FROM AUTHOR]

A novel proposal for upcoming wireless applications introduces a dual-band, highly decoupled, and compact microstrip patch co-planar waveguide (CPW)-fed MIMO antenna. This low-profile antenna exhibits narrow wide-band performance across the frequency bands of 6.2 to 11.2 GHz, with dimensions of 20×20 mm³ on a standard FR4 substrate. Through integration onto a printed circuit board (PCB) measuring 20 × 20 mm², the antenna configuration is expanded to a 4 × 4 MIMO arrangement. Individual antennas within this setup maintain a significant isolation of around 20 dB in the absence of a decoupling mechanism. Fabrication of the designed four-port antenna allows for practical measurement of various antenna parameters. The measured results closely align with simulated outcomes, encompassing S parameters, far-field patterns, and MIMO characteristics such as envelope correlation coefficient, channel capacity loss, and total active reflection coefficient. These results suggest that the antenna design presented in this study holds promise for future wireless applications. [ABSTRACT FROM AUTHOR]

Abstract—Today, drones need a reliable data network to perform operations such as command and control or autonomous flight. Combined with hybrid architecture of cellular and satellite networks, drones can fly quickly and safely in urban areas. A large number of connected objects can only develop if it is possible to make them entirely energy autonomous. In this article, we describe an optimal and environmentally friendly solution to these problems; it is renewable energy harvesting technology (solar, electromagnetic) that can extend the life of these sensors. This vision has given rise to a conversion system that we have called "Solar Rectenna." Our contribution allows the energy autonomy of a drone, thus ensuring a combination of cellular and satellite networks allowing commercial drones to fly quickly and safely in urban areas. A 5G antenna at 60 GHz has been proposed and studied and the simulation results of this one is very advantageous with a gain of 6 dBi, a bandwidth of approximately 4 GHz and a reflection parameter S11 at –25 dB. An identical two-antenna MIMO system based on the 60 GHz antenna has been developed whose purpose of increasing the number of transmitting and receiving antennas to improve the communication quality and increase the channel capacity. Good results of S-parameter simulations |S11| and |S21| are obtained with an isolation method between the two antennas based on SRR metamaterials. Finally, the antenna array will be included on the back side of our solar cell to design our solar rectenna system which will be dedicated to the recovery of energy for the supply of drones and the transmission of their data via satellite in rural and urban areas, such as the detection of forest fires via drones equipped with thermal cameras. [ABSTRACT FROM AUTHOR]

This investigation introduces a MIMO antenna using cylindrical shaped dielectric resonators and discusses both the design and implementation approaches. The proposed antenna design employs a CSRR structure and L-shaped metallic reflectors to improve isolation across many frequency bands. The typology operates at five different frequency ranges: 2.48, 3.92, 5.36, 7.4, and 8.56 GHz. It provides isolation levels of 39, 52.5, 33.8, 42.9, and 37.2 dB, respectively. The semi-circular tapered feed enables for circular polarization between 5.3 and 5.75 GHz. The simulated results indicate that the specified antenna is appropriate for usage in five frequency ranges: 2.1–2.6, 2.7–4.4, 4.9–5.8, 6.9–7.8, and 8.1–9.1 GHz. In a multiple-input multiple-output configuration, antenna performance is evaluated using a variety of diversity indicators, including the envelope correlation coefficient, mean effective gain, diversity gain, channel capacity loss, and total active reflection coefficient. Both simulations and measurements reveal that the proposed antenna can handle Wi-Fi 6, Wi-Max, and W-LAN services, including X-band. [ABSTRACT FROM AUTHOR]

To enhance the transmission rate and bandwidth utilization of Multiple-Input Multiple-Output (MIMO) communication systems, a dual-band MIMO antenna for millimeter waves is proposed, which is based on a substrate-integrated waveguide (SIW) and fed by a 50O microstrip line. To achieve the dual-band performance, it employs a modified dual P-shaped slot instead of the conventional single P-shaped slot. The modified slot antenna generates dual-frequency radiation by exciting the primary and mixed modes in the circular resonant cavity. To improve the channel capacity of the system, the antenna is formed into a 2-element antenna, and the isolation of the antenna is improved by pattern diversity and defected ground structure (DGS). The antenna's prototype is fabricated using a standard printed circuit board (PCB) process. The antenna's dimension is 20 × 18.9 × 0.508 mm³. Measured results show that the impedance bandwidth of the antenna is about 26.7 GHz-27.9 GHz and 37.95 GHz-40.92 GHz with peak gain of 5.63 dBi and 6.35 dBi, respectively. In addition, the isolation degree is greater than 30 dB, the envelope correlation coefficient (ECC) less than 0.0002, and the diversity gain (DG) greater than 9.995. The antenna shows the advantages of low profile, dual-frequency radiation, and high isolation characteristics, which are well suited for millimeter-wave wireless communication systems. [ABSTRACT FROM AUTHOR]

This paper proposes a broadband eight-antenna array design suitable for Fifth Generation New Radio (5G NR) smartphone applications. To cover the 5G NR bands n77/n78/n79 (3300–5000 MHz) and 5G NR-U n46 band (5150–5925 MHz), the single antenna array unit applied is a modified loop antenna element (MLAE) that can generate three different loop modes. To yield good multi-input multi-output (MIMO) performances, the designed MLAE is further arranged as an eight-antenna array, and the experimental results show that the overlapping 6 dB bandwidth can cover the bands-of-interest (3300–5925 MHz) with good isolation and total efficiency of >10 dB and 51–84%, respectively. Finally, good MIMO performances, such as an envelope correlation coefficient (ECC) of lower than 0.1 and desirable channel capacity (CC) of 37–40 bps/Hz, were calculated across the bands-of-interest. [ABSTRACT FROM AUTHOR]

Terahertz (THz) spectral region from 0.1 to 3 THz is envisaged to hold immense potential in the next generation of wireless technologies. Recently, research has focused on this terahertz gap, because of its unprecedented channel capacities. At the physical layer, the design complexities and fabrication of THz devices, especially antennas are the prime bottlenecks to realize its full potential. This article introduces a cost-effective, easy-to-fabricate, and reproducible sub-THz antenna design based on a single-layer planar printed circuit board technology. The antenna incorporates carefully designed quasi-cross slots and applied machine learning-assisted global optimization techniques to achieve the desired performance metrics. The antenna performance is elucidated through numerical simulations and verified through a rigorous in-house THz experimental framework around 100–110 GHz. The proposed antenna offers a peak gain of 13.90 dBi with less than 1 dB variation within the entire band of 100–110 GHz. The antenna holds the potential to achieve terabits per second data rates and futuristic high-resolution short-range THz imaging applications. [ABSTRACT FROM AUTHOR]

In IoT paradigm, Sensor-Cloud Infrastructure provides sensor nodes that sense various environmental parameters, generates the data and sends the same to the desired destination, say a cloud server through a common gateway. Sensor nodes with different data streaming specifications, can generate huge amount of traffic, if streams data simultaneously towards the destination, according to a random schedule. This can lead to higher bandwidth requirements in the wireless medium and increase the amount of data to be received at the gateway in any time slot. This further increases the channel capacity required at the access link to transmit the received data from gateway to the server. An optimal schedule of the sensor nodes will lead to minimization of instantaneous aggregated traffic in both the wireless medium and the access link. Thus leading to minimization of required bandwidth at the wireless medium and channel capacity at the access link. This would further increase the resource utilization of minimize the service provisioning cost of the sensor-cloud infrastructure. A straight forward optimization of the problem of minimizing the instantaneous aggregated traffic load generated from n sensor nodes require an exponential time to find the optimal schedule. Thus, in this paper, an ILP formulation and a polynomial-time heuristic algorithm is presented. [ABSTRACT FROM AUTHOR]

In this paper, a slotted frustum-shaped $ 4\times 4 $ 4 × 4 multiple-input multiple-output (MIMO) dielectric resonator antenna (DRA) is designed and developed for portable 5G Wi-Fi ( $ 5.15{-}5.85\, {\rm GHz} $ 5.15 − 5.85 GHz ) applications. The DRA is excited by $ HEM_{11\delta } $ HE M 11 δ and $ HEM_{21\delta } $ HE M 21 δ modes. A slotted right-angle frustum-shaped (SRFS) structure of alumina material as a dielectric resonator (DR) is positioned on the ground plane of the FR4 substrate to design a DRA. Based on the designed DRA, a compact ( $ 2.57\, \lambda _g\times 2.57 \,\lambda _g $ 2.57 λ g × 2.57 λ g , where $ \lambda _g $ λ g is guided wavelength and calculated at a lower cut-off frequency, $ 5.0\, {\rm GHz} $ 5.0 GHz , for $ \epsilon _f $ ϵ f of $ 4.4 $ 4.4) $ 4\times 4 $ 4 × 4 MIMO antenna with high isolation of greater than $ 27.13\, {\rm dB} $ 27.13 dB (from $ 5.0 $ 5.0 to $ 6.1\, {\rm GHz} $ 6.1 GHz ) and $ 24.3\, {\rm dB} $ 24.3 dB (from $ 6.1 $ 6.1 to $ 6.25\, {\rm GHz} $ 6.25 GHz ) is proposed. The developed MIMO antenna's measured working frequency ranges from $ 5.0 $ 5.0 to $ 6.25\, {\rm GHz} $ 6.25 GHz , with an impedance bandwidth, $ BW_i $ B W i of $ 22.22\% $ 22.22 % , peak gain, $ G_P $ G P of $ 5.85\, {\rm dBi} $ 5.85 dBi and an average peak gain, $ G_{av} $ G av of $ 5.25\, {\rm dBi} $ 5.25 dBi . The calculated MIMO antenna's diversity performance parameters, channel capacity loss $ (C_{CL}^{ij}) $ (C CL ij) , diversity gain $ (D_G^{ij}) $ (D G ij) , envelop correlation coefficient $ (E_{CC}^{ij}) $ (E CC ij) , mean effective gain $ (M_{EG}^i) $ (M EG i) , total active reflection coefficient $ (T_{ARC}) $ (T ARC) , and channel capacity $ (C_C) $ (C C) are obtained as $ { \lt }0.17\, {\rm bits}/{\rm sec}/{\rm Hz} $ < 0.17 bits / sec / Hz , $ { \gt }9.99 \, {\rm dB} $ > 9.99 dB , $ { \lt }0.0301 $ < 0.0301 , $ { \lt }-6.06\, {\rm dB} $ < − 6.06 dB , $ { \lt }-12.5\, {\rm dB} $ < − 12.5 dB , and $ { \lt }21.6\, {\rm bits}/{\rm sec}/{\rm Hz} $ < 21.6 bits / sec / Hz , respectively. The agreement between the simulation and measurement results is found to be remarkably consistent. [ABSTRACT FROM AUTHOR]

In this paper, four-element Multiple-Input Multiple-Output (MIMO) antenna system has been proposed for Intelligent Internet of Everything (IIoE) and high-speed data applications. The presented antenna design operates at 4.9 GHz (5G millimeter wave applications) with high isolation in a small size. Defected Microstrip Structure (DMS), slot modification and orthogonal polarization are used to generate the desired frequency band, improve the impedance bandwidth, and enhance the isolation between antenna elements at 4.9 GHz, respectively. Furthermore, the usefulness of the proposed MIMO antenna has been verified by comparing the simulated and the measured results using a fabricated version of the considered 4 × 4 MIMO antenna. In addition, the results indicate a high diversity performance in terms of: Envelope Correlation Coefficient (ECC), Diversity Gain (DG), Efficiency, Gain, Total Active Reflection Coefficient (TARC) and Total Channel Capacity Loss (CCLTotal). [ABSTRACT FROM AUTHOR]

With multi-band rejection characteristics, a new low-profile antenna of size 34 × 34 mm2 is conferred in this article. It consists of quad identical monopole elements (originated orthogonally), contributing ultra-wideband characteristics in the system. The single unit of the proposed design consists of a modified spinning-top shape radiator (MSTSR), excited by a tapered microstrip line feed (TMLF) and semi-circular ground. An excellent bandwidth of 3–12.9 GHz (where S11 < − 10 dB) is obtained at each port. By inserting the structure of four spiral coils, a sharp notch ranging from 7.9 to 8.5 GHz is achieved to filter the X-band satellite communication uplink. In addition, a circular spiral slot in the radiator near the ground plane creates a stop band at 7.35–7.565 GHz band (satellite communication downlink band). Furthermore, symmetrical rectangular trapezoid resonators and inverted symmetrical rectangular trapezoid structures near the feed line are responsible for the elimination of interferences at 5.5 GHz lower WLAN and 3.5 GHz WiMAX respectively. The FR-4 substrate used for the UWB-MIMO design fabrication process and fabricated results are found in good match with the simulated results. Also, the design provides good performance metrics such as total active reflection coefficient, diversity gain, channel capacity loss, isolation, and envelope correlation coefficient. [ABSTRACT FROM AUTHOR]

Flying base stations, also known as aerial base stations, provide wireless connectivity to the user and utilize their aerial mobility to improve communication performance. Flying base stations depend on traditional stationary terrestrial base stations for connectivity, as stationary base stations act as the gateway to the backhaul/cloud via a wired connection. We introduce the flying base station channel capacity to build on the Shannon channel capacity, which quantifies the upper-bound limit of the rate at which information can be reliably transmitted using the communication channel regardless of the modulation and coding techniques used. The flying base station's channel capacity assumes aerial mobility and ideal positioning for maximum channel capacity. Therefore, the channel capacity limit holds for any digital and signal processing technique used and for any location or positioning of the flying base station. Because of its inherent reliance on the stationary terrestrial base station, the flying base station channel capacity depends on the stationary base station's parameters, such as its location and SNR performance to the user, in contrast to previous research, which focused on the link between the user and the flying base station without the stationary base station. For example, the beneficial region (where there is a positive flying base station capacity gain) depends on the stationary base station's power and channel SNR in addition to the flying base station's own transmission power and whether it has full duplex vs. half-duplex capability. We jointly study the mobility and the wireless communications of the flying base station to analyze its position, channel capacity, and beneficialness over the stationary terrestrial base station (capacity gain). As communication protocols and implementations for flying base stations undergo development for next-generation wireless networking, we focus on information-theoretical analyses and channel capacity to inform future research and development in flying base station networking. [ABSTRACT FROM AUTHOR]

The demand for compact, efficient, and versatile antennas has surged in tandem with the rapid evolution of wireless communication technologies. In response, this paper presents a pioneering Quadport-based fractal compact MIMO antenna designed to meet the stringent requirements of modern communication systems. The antenna incorporates a circular-shaped fractal radiating element and a stub-loaded ground region with a Partial ground, resulting in a significant enhancement of isolation performance. Through iterative optimisation, involving the integration of Partial ground, loading stubs, and fractals into the patch area, the antenna achieves optimal dimensions of 0.66λ × 0.83λ while operating across five distinct frequency bands, thereby catering to a wide range of multiband applications. Remarkable performance metrics are demonstrated, including peak isolation of 35 dB and minimum return loss of − 25.80 dB, alongside a peak electric field of 5.51 × 103 V/m. The polarization response for various resonating frequencies is meticulously analysed. The diverse parameters such as Total Active Reflection Coefficient < − 10, Mean Effective Gain around 0, Diversity Gain is around 10, Channel Capacity Loss < 0.2, and Envelope Correlation Coefficient < 0.1 are achieved. Utilising FR4 material for design enables mass production feasibility, further enhancing the antenna's practicality. Comparative analysis against existing literature underscores its superiority, positioning it as an ideal candidate for applications in 6G networks, WiMax, and weather monitoring. Overall, this Quadport-based fractal compact MIMO antenna represents a significant advancement in antenna offering a compelling blend of compactness, multiband capability, and exceptional performance metrics essential for the next generation of communication applications. [ABSTRACT FROM AUTHOR]

This article presents a meticulously engineered MIMO antenna system tailored specifically for 26 GHz millimeter-wave applications. It integrates a compact planar-patterned metamaterial (MTM) structure, carefully designed with split square and hexagonal unit cells to realize an effective near-zero index (NZI) range for both permeability and permittivity. Comprehensive wave propagation analysis along the y-axis rigorously examines the MTM's characteristics. The antenna system showcases impressive technical attributes, including an extensive 8.7 GHz bandwidth, notably highlighting mu-near-zero (MNZ) characteristics spanning over 8.7 GHz wide frequency spectrum, and epsilon near zero (ENZ) properties covering 8 GHz (26–34 GHz). Notably, a 4-ports MIMO antenna design is adopted with each element meticulously crafted using a 4-unit cell array configuration. The designed 4 × 4 MIMO antenna is fabricated using Rogers RT/duroid 5880 substrate and it occupies a compact dimension of 45.5 × 45.5 × 0.8 mm3. Experimental validation reveals compelling performance metrics, including a bandwidth spanning from 24.3 to 30.9 GHz, isolation levels below − 25 dB, and a maximum peak gain of 15.48 dBi. Additionally, the antenna exhibits circular polarization characteristics, maintaining an axial ratio below 3 dB within the frequency bands of 25.35 to 28.05 GHz and 28.10 to 29.83 GHz. Furthermore, the fabricated MIMO antenna demonstrates outstanding diversity parameters, exemplified by a high diversity gain (DG > 9.99), low envelope correlation coefficient (ECC < 0.0001), minimal channel capacity loss (CCL < 0.5), and total active reflection coefficient (TARC < − 8 dB). The suggested MTM-based MIMO antenna system with sophisticated design and exceptional performance could be an exemplary choice for seamless integration into the evolving landscape of 5G NR networks, particularly those operating within the n257/n258/n261 bands. [ABSTRACT FROM AUTHOR]

Recently, due to the fast development in multimedia applications of wireless communication systems and demands of increasing the capacity and data rates to meet the requirements of 5G mobile communication systems, new transmission techniques are needed. One of the powerful enabling tools of the 5G communication systems is the multi-input multi-output (MIMO) antenna system employing multiple antennas and utilizing the multipath fading mobile environment to increase the channel capacity without any additional bandwidth and/or transmitted power. However, because of the limited space of mobile devices, the distances between antennas are decreasing. The mutual coupling between antennas severely affects the overall performance of the MIMO system. So, isolation improvement methods are applied to reduce these influences. In this review, different isolation techniques and their features and drawbacks are presented, and the techniques for applying them in modern MIMO antenna systems are illustrated. Besides, the performance characteristics of these MIMO systems are compared. The review also contains basic concepts of the MIMO antenna system and its performance metrics. Finally, the future directions and trends for the MIMO antenna system design are discussed briefly. [ABSTRACT FROM AUTHOR]

This article presents a planar, non-angular, series-fed, dual-element dipole array MIMO antenna operating at 28 GHz with the metasurface-based isolation improvement technique. The initial design is a single-element antenna with a dual dipole array which is series-fed. These dipole elements are non-uniform in shape and distance. This dipole antenna results in end-fire radiation. The dipole antenna excites the J 1 mode for its operation. Further, with the view to improve channel capacity, the dipole array expands the antenna to a three-element MIMO antenna. In the MIMO antenna structure, the sum of the J 1 , J 2 , and J 3 modes is excited, causing resonance at 28 GHz. This article also proposes a metasurface structure with wide stopband characteristics at 28 GHz for isolation improvement. The metasurface is composed of rectangle-shaped structures. The defected ground and metasurface structure combination suppresses the surface wave coupling among the MIMO elements. The proposed antenna results in a bandwidth ranging from 26.7 to 29.6 GHz with isolation improvement greater than 21 dB and a gain of 6.3 dBi. The antenna is validated with the diversity parameters of envelope correlation coefficient, diversity gain, and channel capacity loss. [ABSTRACT FROM AUTHOR]

For the transmission of data at high speed, the requirement of using a larger bandwidth increases due to the rise in wireless communication technologies like smart devices, mobiles, etc. An abrupt increase in the requirement for internet data due to an increase in internet users demanded time-to-time upgrades in available techniques. A significant modernization has been done by technology in mobile and wireless communication and networking fields. Therefore, the development of mobile communication began with the First Generation (1G) and has progressed continuously to the Fifth Generation (5G). To address the weaknesses of previous generations, each successive generation has been developed with improvements. Fifth Generation (5G) is the latest technology in wireless communication cellular systems, providing the highest internet speeds to everyone, anywhere, anytime. 5G has attracted many global researchers, universities, and research institutes to invent new techniques for enhancement in channel capacity and spectrum utilization of communication systems. This paper describes the evolution of cellular networks, expectations from 5G, the challenges and advantages of 5G, and the techniques on which 5G relies. [ABSTRACT FROM AUTHOR]

Due to enhanced data rates and channel capacity, the Multiple-Input Multiple-Output (MIMO) antennas are mainly utilized for advanced IoT applications. The recent research carried out on MIMO antennas ensures the contribution to IoT applications. Moreover, the MIMO antennas have the ability to make communication smooth and enhance communication efficiency between both source and destination. Because of the growing performance of MIMO in IoT, the present study intends to survey the recent studies conducted on different MIMO antennas in IoT and 5G applications from the year of 2015 to 2022. In order to obtain better efficiency, improving the isolation among antenna elements is highly required. Hence, this review article covers various isolation techniques employed in MIMO systems along with performance comparison. In particular, gain enhancement methods, size reduction methods, localization, and tracking methods are surveyed in detail. Also, computational complexity is the major issue faced by the MIMO system. The methods utilized for reducing complexity issues in MIMO are reviewed. Finally, the challenges faced by existing studies and how they will be mitigated in the future are discussed clearly. [ABSTRACT FROM AUTHOR]

A multiple antenna placement system analysis for the improvement of efficiency and capacity for inter and intra vehicular communication is proposed in this article. Four antennas are placed in the four locations of the vehicular body which includes roof, side mirror, rear screen, and dashboard. The constituted antenna occupying the dimension of 40×38.5×0.2 mm3 on flexible substrate material of photo paper and the bending analysis of the model as per the conformal nature on vehicular body is also analyzed and presented in this work. The received power from each receiving antenna response with respect to the transmitter has been analyzed. The channel capacity with respect to the antenna position for V2V communication is analyzed in different areas and in different environmental conditions. [ABSTRACT FROM AUTHOR]

The primary focus of this paper is to evaluate the channel capacity of a Terahertz (THz) communication system using a Multiple Input Multiple Output (MIMO) technique. By deriving mathematical expressions for channel capacity and considering practical constraints, the paper provides insights into the performance of such systems under various conditions. The channel model used in this work accommodates the channel accuracies and transceivers constraints. To validate the proposed channel capacity, some simulations by taking into account deferent parameters namely SNR (Signal to Noise Ratio), MIMO channel Matrix size, and distance between transmitter and receiver are performed. These simulations are carried out for 3 cases which are: (1) Channel State Information CSI is known to both transmitter (Tx) and receiver (Rx), (2) CSI is known to Rx but unknown to Tx, (3) CSI is unknown to both Tx and Rx. In this study, we introduce a mathematical formulation for a communication channel tailored for Terahertz (THz) applications. Using this channel model, we analyze the capacity of the THz channel. The suggested research has the potential to be applied in the design and enhancement of Terahertz (THz) wireless communication systems, aiding in the advancement of robust and high-capacity wireless networks that can fulfill the requirements of contemporary multimedia applications. [ABSTRACT FROM AUTHOR]

This study highlights the benefits of soliton microcombs (SMCs) in FSO communication systems. By employing a microring resonator coupled with an add/drop filter, we achieved soliton microcombs with a precise Free Spectral Range (FSR) of 1870 pm and a Full Width at Half Maximum (FWHM) of 60 pm, tailored for Wavelength Division Multiplexing (WDM) channels. The system utilized 100 lines for the WDM channel with an inter-channel spacing of 0.5 nm and PolSK modulation to encode the data. This combination achieved a bit error rate (BER) of $ 10^{-9} $ 10 − 9 , significantly lower than the $ 10^{-7} $ 10 − 7 observed with traditional systems. For performance simulation, the channel was characterized using the gamma-gamma model, which assessed the impact of atmospheric turbulence on data transmission. The results show a high channel capacity ( $ 10^3 $ 10 3 Gbit/s) and a low loss probability ( $ 10^{-8} $ 10 − 8 ), ensuring reliable data transmission even in the presence of atmospheric disturbances. This methodology provides substantial improvements in stability and efficiency for FSO networks. [ABSTRACT FROM AUTHOR]

Multiband MIMO antenna system is very important in 5G mobile communication to meet the requirements of increasing data rate. However integrating multiple antennas in the limited space causes mutual coupling. The antenna configuration gets more intricate, if additional circuitry is installed to obtain greater isolation and hence, the occupied area on the board grows significantly, making the overall antenna design bulky. Hence, to provide dual band coverage, decent isolation and compact design, a compact MIMO antenna system is presented in this paper. The proposed system includes a T-shaped resonating structure that is employed on the side-frames to form a MIMO system with eight antennas. The T-shaped strip is designed to resonate at two frequencies and thereby covering two 5G bands (LTE 42/LTE 46). The proposed dual band MIMO system is fairly compact as the individual antennas are mounted on the 150 × 3.6 mm 2 side-frames of the smartphone. The isolation between antenna elements is 14 dB. This is accomplished without the need of a decoupling structure or a complex tuning process. The ergodic channel capacity realized by the suggested MIMO system in the operational bands is more than 41 b/s/Hz and ECC is less than 0.075. The impacts of the presence of plastic frame, display panel and phantom hand on the performance of proposed design are discussed. The proposed design provides compactness, dual band coverage and high isolation. [ABSTRACT FROM AUTHOR]

A compact MIMO antenna with enhanced isolation and the ability to switch the frequency bands is an attractive candidate for the current multifunctional high-speed portable wireless devices. To achieve this objective, a simple and novel compact dual-mode 4-port MIMO configuration for WiMAX and WLAN standards has been introduced in this work. The compactness of the MIMO geometry (34 mm × 34 mm) is due to compact switchable curve-shaped monopoles arranged closely over a loop-shaped continuous ground plane. The ground plane is defected by etching open-ended slots to suppress the surface current flow between the elements. As antenna elements switch between mode-1 (WiMAX band) and mode-2 (WLAN band), the DGS slots are also switchable to enhance isolation across both bands. The switchable DGS slots function as bandstop filters and thus isolate the elements by 40 and 41 dB in the accomplished frequency bands. The intented MIMO antenna reports a − 10 dB return loss bandwidths of 400 MHz (3.3–3.7 GHz) and 1100 MHz (4.75–5.85 GHz) in mode-1 and mode-2, respectively. The diversity metrics of envelope correlation coefficient < 0.002, diversity gain ≈ 10 dB, total active reflection coefficient < − 10 dB, and channel capacity loss < 0.4 b/s/Hz, ensure excellent diversity/MIMO performance. The optimized 4-port MIMO configuration is fabricated, and measured results are compared with the simulated ones to validate the introduced technique. The MIMO antenna's compact form factor and excellent antenna/diversity characteristics confirm its potentiality for use in portable multifunctional wireless devices. [ABSTRACT FROM AUTHOR]

In this paper, a low profile compact 8‐port multiband antenna with polarization diversity principle for automotive communication is proposed. The geometric of the proposed MIMO antenna is integrated with multiple stubs on substrate having a size of 0.94λg × 0.94λg. The proposed design resonates at multiple frequencies of 1.8, 2.4, 5.2, and 5.8 GHz, respectively for GSM, ISM bands and WLAN wireless services which covers the bandwidth of 2.8%, 5%, 5%, and 5.6%, respectively with S11 ≤ −10 dB. Besides, the measured results provide a peak gain of 4.3, 3.1, 4.5, and 4.2 dBi at 1.8, 2.4, 5.2, and 5.8 GHz, omni directional radiation pattern with more than 80% of efficiency in all operating bands. The MIMO structure provides a good isolation of greater than 20 dB without decoupling structure, envelope correlation coefficient of ≤0.1, diversity gain of ≥9.99 dB, mean effective gain of <1 dB, total active reflection coefficient ≤−10 dB, channel capacity loss of ≤0.25 bits/s/Hz. Finally, the housing effect of MIMO antenna is analyzed in the vehicular environment which provides good performance for Vehicular to Intravehicular communication. [ABSTRACT FROM AUTHOR]

This study investigated a novelty system known as optical code division multiple access-free space optics (OCDMA-FSO) based on a new two-dimensional successive weight (2D-SW) code. The proposed approach is developed to be employed in incoherent wireless optical networks to improve channel capacity, support a large number of concurrent users, accommodate a high bits rate, and eliminate the effect of electromagnetic and multiple access interferences. A new mathematical analysis for the proposed system has been detailed, including the expression of signal-to-noise ratio (SNR) and bit error rate (BER). Accordingly, the numerical outcomes of the mathematical analysis at a total data rate of 260 Gbps revealed that the proposed system enhanced the channel capacity to 2.04, 1.6, 3.32, 1.47, 1.68, 1.33, and 2.29 times than those of the systems based on the two-dimensional codes family including perfect difference (2D-PD), both diluted perfect difference (2D-DPD) and dynamic cyclic shift (2D-DCS), hybrid flexible cross-correlation/modified double weight (FCC/MDW), hybrid zero cross-correlation/multi-diagonal (2D-ZCC/MD), modified prime code (2D-MPC), hybrid prime code (2D-HPC), and one-dimensional successive weight (1D-SW), respectively. It can save − 4.9 dBm, − 2.9 dBm, − 4.3 dBm, and − 2.2 dBm of received power in comparison to both 2D-DPD, 2D-DCS, 2D-ZCC/MD, 2D-MPC, and 2D-HPC codes respectively, and it keeps − 6.2 dBm when moving from 1D-SW to 2D-SW. Moreover, the suggested network is also studied using Optisystem software at 30 Gbps of each channel, where it achieves a low BER value reaching 1.72 × 10 - 33 with a high transmission quality reaching 11.99 at a lengthy range attaining 1.3 km. Consequently, the results demonstrate that the proposed system can satisfy optical communication needs and be implemented in the next generations of wireless optical networks. [ABSTRACT FROM AUTHOR]

The utilization of Free Space Optical (FSO) systems in upcoming 5G or beyond systems is appealing due to its secure transmission, unlicensed spectrum, and higher information rate. Despite the various advantages of the FSO system, long-range communication transmission is inadequate because the effectiveness of FSO systems is significantly impaired by environmental phenomena such as scintillation, fog, haze, and rain. This research intends to improve the FSO module's effectiveness in terms of channel capacity and long-range communication. The present research has employed a hybrid technique that integrates multiple-beam, Erbium-doped fiber amplifier amplification and Homodyne detection methodologies within a wavelength division multiplexing FSO system to achieve the desired outcome. The channel model employed in this study is the Gamma–Gamma model, and the framework is evaluated using various strategies including single beam (SB1 × 1), four beams (MB4 × 4), and eight beams (MB8 × 8). The findings indicate that optimal performance has been achieved through the utilization of MB8 × 8. A channel capacity of 320 Gb/s has been observed across a range of 1.6–12 km, with variations in transmission distance attributed to external environmental factors. The link effectiveness is evaluated through the calculation of the Bit Error Rate, Q factor and Eye Height analysis. [ABSTRACT FROM AUTHOR]

Optical backbone networks, characterized by using optical fibers as a transmission medium, constitute the fundamental infrastructure employed today by network operators to deliver services to users. As network capacity is one of the key factors influencing optical network performance, it is important to comprehend its limitations and have the capability to estimate its value. In this context, we revisit the concept of capacity from various perspectives, including channel capacity, link capacity, and network capacity, thus providing an integrated view of the problem within the framework of the backbone tier. Hence, we review the fundamental concepts behind optical networks, along with the basic physical phenomena present in optical fiber transmission, and provide methodologies for estimating the different types of capacities, mainly using simple formulations. In particular, we propose a method to evaluate the network capacity that relies on the optical reach to account for physical layer aspects, in conjunction with capacitated routing techniques for traffic routing. We apply this method to three reference networks and obtain capacities ranging from tens to hundreds of terabits/s. Whenever possible, we also compare our results with published experimental data to understand how they relate. [ABSTRACT FROM AUTHOR]

Ultra-reliable low-latency communication (URLLC) is a key technology in future wireless communications, and finite blocklength (FBL) coding is the core of the URLLC. In this paper, FBL coding schemes for the wireless multi-antenna channels are proposed, which are based on the classical Schalkwijk-Kailath scheme for the point-to-point additive white Gaussian noise channel with noiseless feedback. Simulation examples show that the proposed feedback-based schemes almost approach the corresponding channel capacities. [ABSTRACT FROM AUTHOR]

This paper introduces the novel IRS-based Optimal Relay Selection (ORS-IRS) method, aimed at analyzing the performance of wireless communication systems with an emphasis on symmetry. The ORS-IRS approach presents an innovative communication algorithm that seamlessly integrates Intelligent Reflecting Surfaces (IRS) with relay selection techniques. Through adaptive adjustments of reflection coefficients, IRS elements efficiently manipulate incoming signals, fostering symmetry in signal strength enhancement and latency reduction for improved signal delivery to the intended destination. This symmetrical optimization in channel capacity and transmission power ensures reliable data transmission with low latency, achieved through the seamless integration of IRS and relay selection techniques. In contrast, the Cell-Free Massive MIMO (CF-M-MIMO), with its decentralized architecture, excels in serving a larger user base and attaining remarkable capacity gains, showcasing a different dimension of symmetry. The Decode-and-Forward (DF) relaying approach demonstrates its potential in enhancing signal reliability across extended distances, contributing to the overall symmetry of the comparative analysis. This comprehensive evaluation provides valuable insights into selecting appropriate transmission strategies, particularly for applications that demand high capacity and reliability in the design of modern wireless communication systems with a symmetrical focus. [ABSTRACT FROM AUTHOR]

For future fifth-generation (5G) smartphones, a high-efficiency multiple-input/multiple-output (MIMO) antenna system capable of operating in Long Term Evolution (LTE) 42/43/46 is suggested. A pair of small microstrip-fed slot antenna and inverted F antenna is part of the single antenna design structure. They are positioned on the longer side of the FR-4 printed circuit board. In an effort to lessen the mutual coupling, two antenna elements have a U-shaped rectangular slot inserted between them. The detailed study of the suggested MIMO system includes measurement of the reflection parameter, analyzing the radiation performance, performing envelope correlation coefficient (ECC) and channel capacity calculations, and analyses of the effects of user's hand in the vicinity of the antenna array. Simulation and measurement results demonstrate the required performance of the proposed design, that is, greater than 80% of total efficiency, isolation >12 dB, and ECC <0.15. The suggested antenna has the benefits of multiband operation, high efficiency, good isolation, and a small footprint. [ABSTRACT FROM AUTHOR]

A holistic performance analysis and classification of multiport antennas (MPAs) is conducted in this paper. We focus on 5.9 GHz vehicle-to-vehicle communications suited to the emerging technology of intelligent transportation systems. Three-dimensional (3-D) uniform/isotropic, directional, and omnidirectional propagation scenarios are considered to account for any wireless environment. The presented analysis can be adapted to any MPA with an arbitrary number of ports, operating in any frequency band, or used in other emerging technologies such as in 5G and beyond 5G communications. On top of the classical key performance metrics (KPMs) in communication theory, i.e., the diversity antenna gain (DAG) and channel capacity (CC), we employ for the first time the energy efficiency as one more KPM capable to characterize performance and classify MPAs, particularly when DAG and CC fail to do so. Computation of the aforementioned KPMs departs from a covariance matrix formulation incorporating all intrinsic features that affect MPA performance, namely, MPA radiation characteristics, MPA termination conditions, and wireless propagation channel attributes. Accordingly, we derive the ideal form of the covariance matrix under the standardized and widely adopted 3-D uniform/isotropic wireless propagation scenario. A good MPA design should be one with a covariance matrix as close as possible to this ideal one. The adopted performance analysis methodology can thus inform the design of optimum MPAs and accordingly, we designed a proof-of-concept box-shaped MPA which shows outstanding performance across all propagation scenarios. It would be wise to conduct similar performance analyses as in this paper before releasing an MPA design. [ABSTRACT FROM AUTHOR]

This study introduces a novel, non-planar 16-port massive Multiple-Input-Multiple-Output (MIMO) antenna system that has been designed for six-generation (6G) THz future applications. On a cross-shaped of a 100 um thick Polyimide substrate, the proposed MIMO elements are positioned strategically to encompass a wide frequency band of 61.54%. A compact near-zero indexes and epsilon-negative metamaterial unite cell is designed and implemented to increase the isolation, gain and the overall antenna performance. The metamaterial elements are located on both top and bottom layers of the substrate, achieving an isolation of greater than 24 dB for antenna elements on the same side of the cross-shaped substrate. Besides the antenna's isolation enhancement, the gain and efficiency improved to a maximum of 13.2 dBi and 92%, respectively. In addition, extensive simulations demonstrate that MIMO performance parameters, such as Diversity gain ≈ 10 dB, Envelope correlation coefficient ≤ 0.001, Total Active Reflection Coefficient ≤ −15 dB and Channel Capacity Loss (0.4 bits/s/Hz are favorable. The proposed non-planar 3D massive MIMO antenna system has tremendous potential for the sixth generation's THz wireless communication applications. [ABSTRACT FROM AUTHOR]

The channel matrix of the commonly used uniform circular array-based orbital angular momentum (UCA-OAM) system reaches the full-rank state when the degree of freedom (DoF) is limited only by the number of UCA antenna elements. The rank of the channel matrix of the UCA-OAM system is equal to DoF under this condition. However, the practical DoF of the UCA-OAM system is always affected by other transmission factors, such as the transmission distance and the radius of the receiving antenna. Therefore, by exploiting the practical DoF of the UCA-OAM system affected by the transmission distance and the radii of the receiving antenna and transmission antenna, a novel channel capacity model of the UCA-OAM communication system with a deficient-rank channel (DRC) matrix is first proposed. Moreover, the formulas of the channel matrix and channel capacity for the DRC matrix are analytically derived. The results of numerical simulations indicate that when the practical transmission factors including transmission distance and radii of the receiving antenna and transmission antenna are considered, the UCA-OAM communication system with the DRC matrix has less channel capacity than that with the full-rank channel (FRC) matrix. These simulated results provide helpful guidance on the practical application of the UCA-OAM communication system. [ABSTRACT FROM AUTHOR]

Abstract—The purpose of this article is to analyze the capacity of a discrete-continuous communication channel (DC-channel) as applied to nonorthogonal multiple access (NOMA) systems. In this work, an expression is obtained for the individual mutual information of a DC-channel in communication systems with nonorthogonal access, which makes it possible to analyze the capacity of the DC-channel individually for subscribers of NOMA systems. Its effectiveness for analyzing group signals of NOMA systems is shown, examples of its use are given, and capacity characteristics for NOMA subscribers are obtained as well. [ABSTRACT FROM AUTHOR]

A four-port MIMO antenna with high isolation is presented. The antenna is primarily envisioned to cover the n48 band of Frequency Range-1 (FR-1) with TDD duplex mode. The engineered antenna has electrical dimensions of 90 × 90 × 1.57 mm3. The size miniaturization of a single antenna unit is achieved through an optimized placement of slots and extended arms. The quad-antennas are then placed orthogonally to achieve antenna diversity. The antenna resonates at 3.56 GHz and 5.28 GHz having 2:1 VSWR fractional bandwidth of 1.82% and 2.12%. The proposed resonator provides 88.34% and 79.28% efficiency at lower and upper bands, respectively. The antenna is an exceptional radiator regarding MIMO diversity performance owing to high inter-element isolation. The values of envelope correlation coefficient < 0.05, channel capacity loss is nearly 0.1 bits/sec/Hz, and total active reflection coefficient is − 24.26. The full ground plane profile aids in high directivity and cross-pol isolation. The antenna exhibits a gain of 4.2 dBi and 2.8 dBi, respectively, justifying intended application requirements. There is a good coherence between simulation and experimental results. The self-decoupled antenna poses its application in 5G and WLAN Communication Applications. [ABSTRACT FROM AUTHOR]

Transmission and reception of images and videos are critical for remote real-time underwater monitoring in internet of underwater things (IoUT) applications. Underwater communication is particularly challenging since it relies on highly lossy underwater acoustics (UWA) channel. High- speed mobility is difficult in UWA systems as UWA includes fast-varying channels. For channel estimation and image transmission in UWA, the performance of the conventionally used orthogonal frequency-division multiplexing (OFDM) might deteriorate dramatically if precise Doppler correction is not used. To alleviate this issue, the orthogonal time frequency space (OTFS) modulation is effective. The advantages of OTFS are two-fold, i.e., the orthogonality in time–frequency domain and clustered sparsity of channel information in the delay-Doppler domain. For efficient image transmission in the UWA channel, the integration of compressed sensing (CS) has also been proposed in this work. The two-dimensional structured Robbins Monro (RM) and the greedy orthogonal matching pursuit (OMP) CS algorithms are considered and the better between the two have been established. The proposed approach converts a time–frequency doubly fading UWA channel to a time invariant channel. Here the high-resolution picture that is to be sent is separable and orthogonal in character. All of the delay- Doppler diversity branches are grouped together. OTFS is able to achieve channel capacity with optimum performance-complexity because of the high-resolution delay-Doppler separation. Moreover, OTFS also provides robustness against Doppler and multipath channel conditions. Simulation results prove that the suggested 2D-OMP and 2D-RM algorithms offer higher MSSIM and PSNR values than the OTFS system alone. [ABSTRACT FROM AUTHOR]

This paper presents design of a 4-element crescent-shaped two-sided multiple-input-multiple-output (MIMO) antenna, employing pattern and polarization diversity with improved element-to-element isolation, for UWB, X and Ku band wireless applications. The proposed crescent-shaped MIMO structure consists of two antennas on the top and remaining two antennas on the bottom sides of the substrate. The developed antenna operates in a frequency range from 2.8 to 15.2 GHz, covering the entire UWB 3.1–10.6 GHz, X-band and portion of Ku-band giving element-to-element isolation of more than 20 dB in most of the operating bands. Also, the proposed MIMO structure gives a maximum gain of 6.6 dBi with radiation efficiency from 75 to 95% in the operating band. The important MIMO parameters like envelope correlation coefficient (ECC < 0.005), channel capacity loss (CCL < 0.03 bits/s/Hz), mean effective gain (MEG < − 3 dB) and total active reflection coefficient (TARC < − 10 dB) are presented to estimate the performance of the developed UWB MIMO system. [ABSTRACT FROM AUTHOR]

In this work, a compact size 4 ports multiple input multiple output (MIMO) slot antenna with the connected ground for Ultra-Wide Band (UWB) and X band applications is introduced and discussed. The single antenna is a cross-shaped slot antenna in the ground plane and a 50 Ω microstrip line with a small L-stub is used to feed the antenna on the other side. The suggested MIMO antenna has four identical elements arranged to be orthogonal to each other to enhance the MIMO system performance. The antenna elements are connected with a small strip to compose the proposed connected ground antennas. The suggested MIMO antenna has an overall size of 47 mm × 47 mm. The antenna has tested and simulated bandwidth with S 11 < −10 dB extended from 4– 14 GHz and has isolation greater than 20 dB between ports without utilizing the decoupling elements and with good consistency between results. The MIMO antenna has peak gain and efficiency, envelope correlation coefficient, diversity gain, and channel capacity loss of 5.6 dBi and 80%, <5 × 10–3, 10 dB, and <0.4 bit/s/Hz, respectively which prove that our antenna can be suggested for the UWB MIMO applications. [ABSTRACT FROM AUTHOR]