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We report on the theoretical design and experimental verification of a high efficiency microwave wireless power transmission (MWPT) system operating in the Fresnel region. To achieve high conversion efficiency over a transmit distance of 11 meters, the transmit reflector antenna was optimized to locate the focal point at 11 m. The size of the receive antenna was decided by calculating the field distribution and the received power at different positions in the receive antenna aperture. Furthermore, an accurate model of the diode is presented, which was imported into the ADS software for high-precision rectifying circuit design. As a result, an overall DC-DC conversion efficiency of 20% was achieved, as measured in an anechoic chamber at a given distance of 11 m. The experimental results validated the proposed method. [ABSTRACT FROM AUTHOR]

Antenna selection techniques are extensively applied to reduce hardware cost and power consumption in multiple-input multiple-output (MIMO) systems. This paper proposed a low-cost antenna selection method for system sum-rate maximization based on multiclass scalable Gaussian process classification (SGPC) which is capable to perform analytical inference and is scalable for massive data. Simulation results show that the average sum-rate obtained by SGPC is 1. 9 bps/Hz more than that obtained by conventional optimization driven user-centric antenna selection (UCAS) algorithm and 1 bps/Hz more than that obtained by the up-to-date learning scheme based on a deep neural network (DNN) when signal-to-noise ratio (SNR) is 10 dB, the number of total antennas at BS is 6, the number of selected antennas is 4, and the number of single-antenna users is 4. The superiority of SGPC over UCAS and DNN is more obvious as SNR, the number of selected antennas, or the number of users increases. [ABSTRACT FROM AUTHOR]

A system of hemispherical antenna arrays consisting of 299 elements operating at a carrier frequency of 3.6 GHz has been designed and simulated. The array elements are distributed uniformly, on two concentric hemispheres, on top of the surface of a human's brain, which is represented as a hemispherical surface with a radius of 9.5 cm. The outer array consists of 171 elements, and the inner array consists of 128 elements (i.e., total of 299 elements). The radial distances between the human brain and the inner array and the inner and outer arrays are 1.5 cm and 2.08 cm, respectively. The electromagnetic fields inside the brain are found by treating the array system as a boundary-valued problem. A beam-focusing technique focuses the total magnetic intensity to a desired point or multiple points in the brain. This beam-focusing technique aims to target a specific neuron within the brain and induce correct neuron firing to elevate the symptoms of Parkinson's disease. Since neurons respond to low frequencies (≈10 Hz), two modulating schemes are used to modulate the carrier signal and allow it to have a low-frequency envelope. The first scheme allows each antenna element to transmit a superposition of sinusoidal signals with 51 different frequencies, varying as multiples of 10 Hz but centered around 3.6 GHz. The second scheme is achieved with each antenna element transmitting at a single but distinct frequency centered around 3.6 GHz. The variation of the frequency of operation from one element to the other is 10 Hz. The slight variations between the different frequencies of the antenna elements will be used to achieve a low-frequency envelope. This multi-frequency signaling enables the carrier signal to be modulated with any real-time periodic signal desired. [ABSTRACT FROM AUTHOR]

Integrated satellite-aerial-terrestrial networks (ISATNs) expand the breadth and depth of seamless connections, which has been recognized as one of the key facilities of next-generation networks. This paper investigates the impact of transmit antenna selection, imperfect channel state information (CSI), and successive interference cancellation (SIC) on ergodic capacity (EC) of nonorthogonal multiple access- (NOMA-) enabled ISATNs, where a high altitude platform (HAP) assists the satellite transmission through decode-and-forward relaying protocol. Besides, two selection schemes are proposed to balance system complexity and transmission efficiency. Imperfect CSI and SIC are considered to impose detrimental effects on system performance. In addition, analytical expressions for EC of NOMA-enabled ISATNs in the presence of the above imperfections are derived. Finally, the Monte Carlo simulations corroborate analytical results and reveal the impacts of imperfections on integrated satellite-aerial-terrestrial networks. [ABSTRACT FROM AUTHOR]

A microwave power transmission (MPT) demonstration system was assembled to comprehensively emulate the operating mode of MPT in space solar power station (SSPS). Based on solid power amplifier and phased antenna array, this system comprised three main parts, that is, microwave power transmitting subsystem, microwave power rectenna subsystem, and power beam steering subsystem. It was employed to validate the constraint relationship between beam collection efficiency and the sizes of transmitting antenna and rectenna, transmission distance, operation frequency. High efficiency rectifying and accurate beam steering were also demonstrated. The power transmitting antenna was composed of 64 sub‐arrays of patch antennas, with the dimension of 1.2 × 1.2 m2. In addition, the rectenna array was constructed as a corner truncated square with the side length of 2 m. Its design was based on the concept of perfectly matched layer and integrated rectifying surface. The power beam steering subsystem, implemented with software retrodirective idea, pointed the microwave beam to the rectenna according to the direction of arrival of the pilot signal. The experimental MPT system, operating at 5.8 GHz, transmitted 910 W microwave power across 30 m distance. At the power receiving end, the optimum rectenna conversion efficiency of 49.3% was obtained. With aid of the beam steering subsystem, beam granularity, and beam steering accuracy of 0.23 and 0.18° were achieved, respectively. The compositive experiment verified all function as power transmitting, receiving, rectifying, and steering of MPT system. MPT technology is thus driven toward engineering application, and will ultimately space solar power exploration. [ABSTRACT FROM AUTHOR]

With the increasing number of Internet of Things (IoT), Industry 4.0 (I4.0), and mobile devices, it can be expected that base stations will have to serve more and more clients with a limited number of antennas. For their broadcast channels, nonorthogonal multiple access (NOMA) and blind interference alignment (BIA) are two efficient and commonly adopted transmission schemes. This paper conducts a comparison study on these techniques on a 3-user 2 × 1 multiple-input single-output (MISO) broadcast channel with a limited number of transmit antennas. Specifically, space-time block coding based NOMA (STBC-NOMA) and NOMA-assisted beamforming (NOMA-BF) are compared with BIA. Both perfect and imperfect successive interference cancellation (SIC) have been considered for NOMA-based schemes, and the theoretical achievable rates of all schemes have been derived. Furthermore, with a given fairness constraint among end users, the power allocation (PA) problems have been solved for cases when accurate channel state information is available at the transmitter (CSIT) as well as when only path loss information is available. Numerical results show the following: (1) none of the schemes under this study can always outperform the others under different SNR regions. (2) With imperfect SIC, NOMA-BF, and STBC-NOMA both suffer from a significant performance loss under a high SNR condition. (3) Fairness PA with only path loss information provides similar performance as that with perfect CSIT, thus partial CSIT is adequate for system or scheme designs in practice. [ABSTRACT FROM AUTHOR]

In recent years, the continuous increase in wireless data services and users' traffic demand has been imposing great challenges on traditional multiple access control (MAC) methods. Some existing MAC techniques improve the communication system's spectral efficiency (SE) via signal processing based cochannel interference (CCI) management. However, no interference management (IM) is free, i.e., its realization is based on the consumption of some communication resources, such as power and degree-of-freedom (DoF), which can also be used for the user's desired data transmission. To lessen the resource cost for IM-based MAC, we exploit interactions among multiple wireless signals to propose a new MAC method, namely, Differentiated Reception Modes based Multiple Access (DRM-MA), in this paper. Under DRM-MA, a central control unit (CCU) is adopted to manage and pair multiple transmitting antennas with their serving receivers (Rxs). The CCU first calculates the phase difference of signals sent from each candidate antenna and perceived by the two receiving antennas of an Rx based on the locations of the transmitting antenna and Rx. Then, the CCU selects and pairs a proper transmitting antenna with each Rx, so that various Rxs can adopt either additive or subtractive reception mode to postprocess the signals received by its two antennas to realize in-phase desired signal construction and inverse-phase interference destruction. DRM-MA can avoid transmission performance loss incurred by signal processing-based IM. Our theoretical analysis and simulation results have shown that DRM-MA can enable concurrent data transmissions of multiple antenna-receiver pairs and output a high system's SE. [ABSTRACT FROM AUTHOR]

In order to improve the stability and control effect of the electromechanical control system, this paper designs the electromechanical control system combined with the computer fault-tolerant technology and proposes an electromechanical control signal processing algorithm. In order to improve the accuracy of the path loss calculation, according to Fresnel's law, this paper deduces the expression of the reflection coefficient of electromechanical control signal with the distance between the transmitting antenna and the receiving antenna as the main variable and then compares the path loss with the ground and the ceiling as the reflecting surface. In addition, in order to study the path loss, this paper selects different reflective materials to study their path loss under horizontal polarization and vertical polarization. The results show that under the vertical polarization, the path loss fluctuation is not large, and the agreement is higher than that of the horizontal polarization. The research results show that the electromechanical control system based on computer fault-tolerance technology proposed in this paper has stable performance and can play an important role in the control of electromechanical systems. [ABSTRACT FROM AUTHOR]

In this paper, the precoders capable of maximizing the weighted sum rate (WSR) for multicell scenarios under power budget constraint conditions per cell were considered based on the MIMO system performance. This rate is strongly affected by intracellular interference, so we recommend using coordinated beam forming (CBF). If the number of user equipment provided per cell is small enough to the number of transmit antennas, simple linear beamformers, such as matched filter (MF), achieve higher performance rates. In general cases, two algorithms meet the best performance in terms of the total achievable rate; these are KG (Kim Giannakis) and WSMSE (Weighted Sum Minimum Squared Error) algorithms. In the KG method, the objective function of the sum rate is suggested to be divided into two functions, one function for the desired user rate and the other for the sum rate of the remaining users. In the WSMSE algorithm, maximizing the sum rate is solved by redefining it as the problem of minimizing the MSE (Mean Square Error) function. These functions are convex and nonconvex functions, respectively. In the proposed method, the WSMSEs were modified to reduce the complexity and calculations to provide optimal performance in beamforming. [ABSTRACT FROM AUTHOR]

The smart city is an emerging concept that is based on the integration of various electronic devices and citizens that enhance the flow of information. IoT is an integral part for next generation wireless network infrastructure for acting as an interface of collecting data and controlling delivery of message which are using in smart cities. In this paper, an IoT-oriented relay assisted MIMO for beyond the fifth-generation wireless network system is proposed. The proposed system provides higher capacity and lower BER. The proposed system's BER results are compared with various combinations of transmission and receiving antennas at source, relay, and destination. It is found from BER performance that the developed scheme with relay does provide 1–17 dB gain with respect to direct connection. It is also found from mathematical analysis and simulation results that this scheme provides 3 to 9 b/s/Hz improvement in performance of capacity at 5 to 10 dB by adding a different combination of STBC and VBLAST. Simulation results are also presented to demonstrate the diversity and multiplexing gain that is a key to providing high data rates with reliable communication with many interferences for the IoT system. This system can also be used for massive antennas-based IoT system by raising the number of transmitting and receiving antennas with proposed encoding and decoding techniques explained in this paper. [ABSTRACT FROM AUTHOR]

Index modulation (IM) is a novel digital modulation technique, which inactivates some subcarriers in orthogonal frequency division multiplexing (OFDM) to exploit the indices of the subcarriers to transmit bits implicitly, and has potential to further improve the energy efficiency and error performance. For the multiple-input multiple-output- (MIMO-) aided IoT devices, a highly efficient and low-complexity IM-aided scheme is needed to reduce the computational complexity at the receiver sides. In this paper, we propose a novel highly efficient MIMO-OFDM with IM scheme by performing IM on each transmit antenna subgroup, which contains two transmit antennas, to achieve two transmit diversity order and significant reduction in computational complexity at the cost of a minor spectral efficiency. To reduce the demodulation complexity, a low-complexity sequential Monte Carlo (SMC) theory-based detector is proposed, which exploits the null space submatrix of the preprocessed channel response matrix by using QR decomposition, to calculate the most likely transmitted IM patterns before the detection of the modulated symbols. Computer simulation results and complexity analysis show that the proposed IM-aided scheme achieves better error performance with extremely low computational complexity under the same constellation and the proposed SMC detector has potential to achieve near optimal bit error rate performance with considerably low demodulation complexity. [ABSTRACT FROM AUTHOR]

In this paper, a low‐size and compact substrate integrated waveguide (SIW)‐based simultaneous transmit and receive antenna is developed for full‐duplex wearable telemetry applications. The antenna operates at 4.9 GHz (Wireless Local Area Network [WLAN]) and 5.8 GHz (Industrial, Scientific and Medical [ISM]) bands with acceptable gains. Keeping a proper gap between the two ports achieves an isolation of better than 29.8 dB. This antenna is kept compact (0.20 λg2, where λg is the wavelength at 4.9 GHz) by additional arc‐shaped slot in each radiator, which adds additional capacitance. The suggested antenna is simulated inside a 52 × 63 × 17 mm3 dummy wearable telemetry device and is worn on the subject's chest. Thanks to SIW technology, it has unidirectional radiation patterns, allowing a minimum beam towards the human body, and thus, offers lower specific absorption rate (SAR) at both frequency bands. The unique advantage is its capacity to receive and transmit the telemetry signals simultaneously. Its low profile, flexibility in the resonant bands, simultaneous transmission and reception, and lower SAR values make this antenna suitable for full‐duplex wearable telemetry devices. [ABSTRACT FROM AUTHOR]

This study demonstrates an efficient 5.8 GHz microwave wireless power transmission (MWPT) system. The whole system comprises a transmitting subsystem and a receiving subsystem. A 64‐way phased microwave power source and a transmitting antenna array of 1 m × 1 m are included in the transmitting subsystem. By exciting the transmitting array with a 10‐dB Gaussian amplitude distribution and a quadratic phase distribution via the phased microwave power source, the transmitting subsystem radiates a low side‐lobe and focused microwave beam. The receiving subsystem comprises a receiving antenna array of 0.5 m × 0.5 m and 64 rectifiers. The efficient receiving antenna array and rectifiers realize an efficient rectenna array. An experiment on the MWPT system is conducted. The total microwave power output from the source is 24 W, and the transmission distance is 10 m. According to the measurements, the total rectified direct current (DC) power is 4.58 W, and the overall RF‐DC efficiency is 19.08%. [ABSTRACT FROM AUTHOR]

The concept of multituned thirteen-tower umbrella antenna is developed in this study to address the problem that increasing the power capacity of a single-tuned VLF transmitting antenna leads to a decrease in self-resonance. The calculation method of electrical parameters such as input resistance and radiation efficiency is theoretically analyzed based on the radiation resistance of different antenna units in a thirteen-tower umbrella antenna, and the electrical performance of the single-tuned and multituned thirteen-tower umbrella antennas is simulated and compared with the measured results of the Cutler antenna. Under the same antenna structure parameters and input power, the antenna radiation efficiency of the multituned thirteen-tower umbrella antenna is basically the same as that of the single tuned one. However, the multituned antenna has lower input current and higher self-resonance, which can effectively improve the antenna's safety and broaden its operating frequency range. [ABSTRACT FROM AUTHOR]

The energy consumption of massive multiple-input multiple-output (MIMO) systems increases with the number of antennas. Optimizing the energy efficiency (EE) of massive MIMO systems is one of the ways to achieve green communication. This paper proposes an EE optimization method that genetic algorithm-based antenna selection and power allocation (GA-AS+PA) for the downlink of a multicell massive MIMO system under the restriction of the users' sum-rate. First, we use the genetic algorithm to determine the active transmitting antenna of each base station (BS). Then, the transmission power for each user is allocated using the convex optimization method. Finally, the EE of system is optimized under the achieved optimum BS's transmit power and the number of active antennas. From the simulation results, the GA-AS+PA method can improve the EE of the system while meeting user sum-rate requirements, which achieves better performance compared with random antenna selection+equal power allocation method (RAS+EPA), random antenna selection+power allocation method (RAS+PA), the antenna selection method based on genetic algorithm+equal power allocation method (GA-AS+EPA), and equal power allocation (EPA) these four methods. The EE of the proposed GA-AS+PA method is improved by 33.3% compared to the EPA method. [ABSTRACT FROM AUTHOR]

Monitor of intracranial pressure (ICP) system is a life‐saving instrument that monitors changes in brain pressure in real time. To implement wireless data transfer, antenna is an indispensable device. In this paper, an implantable antenna is designed with circularly polarized, wideband and compact in size to adapt the application of the ICP monitoring system. First, a one‐layer human skin model to verify the basic characteristics of this antenna; and then a multilayered human head model is built to demonstrate the system performance of the designed antenna. In addition, we also considered the human safety to calculate the specific absorption rate value of the proposed antenna. The antenna can transmit different rates over to 1.5 m distance verified by the wireless communication link, which proved it has a good transitions characteristic. Finally, the sample of the antenna is fabricated and tested with help of fresh minced pork. Experiment results shows the antenna with a good property in the ICP monitoring system, as well as other remote medical telemetry system. [ABSTRACT FROM AUTHOR]

In this article, we propose a novel wireless powered communication network, which is composed of two multiple antennas hybrid access points and a series of distributed wireless devices. The two hybrid access points transmit downlink wireless energy to the wireless devices and receive uplink wireless messages from the wireless devices; meanwhile, the information of wireless devices nearer to their corresponding hybrid access point should be transmitted to the faraway hybrid access point. To improve the throughput performance of some wireless devices away from their corresponding hybrid access point, we propose a clustering-collaboration interactive communication protocol with multiple antennas by Time Division Multiple Access, where two of the distributed wireless devices are selected as cluster heads to help relay information of other cluster members, which can efficiently improve some faraway wireless devices' throughput performance. However, its performance is also constrained by cluster heads' high-energy consumption. To solve this energy imbalance problem, multi-antenna energy beamforming technology is exploited for the hybrid access points, which distributes more transmission power to the cluster heads to balance all the wireless devices' energy consumption. In particular, we obtain the proposed system's throughput performance through the multi-antenna cluster-based collaboration, and verify through simulations that this scheme can effectively enhance user unfairness and improve the throughput performance. [ABSTRACT FROM AUTHOR]

Very low-frequency (VLF) and ultralow-frequency (ULF) electromagnetic waves have the advantage of high penetration and low propagation loss in wireless communication systems and are mainly used for underwater and underground communications, as well as for earthquake and lightning forecasting. At present, VLF and ULF antennas are mostly bulky and require hundreds of antennas and more to be set up, which is costly and inefficient. In this paper, we propose to generate VLF and ULF signals by rotating a multilayer multipair electret thin-film electret driven by an excitation device, which improves the problem of low radiation efficiency of VLF and ULF signals and the large size of conventional low-frequency transmitting antennas. Based on a multilayer, multipair electret film mechanical antenna, a magnetic field propagation model is developed, and the relationship between the magnetic flux density mode and the number of layers of electret films, as well as the relationship between the antenna emission frequency and the motor rotation frequency and the number of pairs of electret films, is analyzed. The selection of a suitable model for practical situations based on conditions such as antenna size and propagation distance is illustrated. The research work is of great importance for guiding the design of mechanical antennas and optimizing antenna structures. [ABSTRACT FROM AUTHOR]

In the present study, a regional localization system is proposed based on the variation of the scattering field in ultrawide band (UWB) frequencies. The system uses the UWB antennas to transmit and receive the sweep sparse signal in the measured area. Subsequently, the compressed sensing (CS) algorithm is employed for localization. To increase the positioning accuracy, the randomness of signal distribution should be improved. Different from the previous designs, the scattering obstacles are introduced between the target and the antennas. Through simulation and experiment, a localization system composed of two transmitters and one receiver working at 10–20 GHz is proposed, leveraging the UWB source antennas and grid metal barriers. By complying with the sparse reconstruction algorithm of the CS method, the positioning accuracy of 1.4 mm is obtained in the area of 40 × 40 mm2 at 40 mm distance. The system is capable of locating in small areas effectively based on simple setup, and potentially applied to human‐computer interaction of wearable devices and other local positioning applications. [ABSTRACT FROM AUTHOR]

The Internet of Things (IoT) facilitates physical things to detect, interact, and execute activities on-demand, enabling a variety of applications such as smart homes and smart cities. However, it also creates many potential risks related to data security and privacy vulnerabilities on the physical layer of cloud-based Internet of Things (IoT) networks. These can include different types of physical attacks such as interference, eavesdropping, and jamming. As a result, quality-of-service (QoS) provisioning gets difficult for cloud-based IoT. This paper investigates the statistical QoS provisioning of a four-node cloud-based IoT network under security, reliability, and latency constraints by relying on the effective capacity model to offer enhanced QoS for IoT networks. Alice and Bob are legitimate nodes trying to communicate with secrecy in the considered scenario, while an eavesdropper Eve overhears their communication. Meanwhile, a friendly jammer, which emits artificial noise, is used to degrade the wiretap channel. By taking advantage of their multiple antennas, Alice implements transmit antenna selection, while Bob and Eve perform maximum-ratio combining. We further assume that Bob decodes the artificial noise perfectly and thus removes its contribution by implementing perfect successive interference cancellation. A closed-form expression for an alternative formulation of the outage probability, conditioned upon the successful transmission of a message, is obtained by considering adaptive rate allocation in an ON-OFF transmission. The data arriving at Alice's buffer are modeled by considering four different Markov sources to describe different IoT traffic patterns. Then, the problem of secure throughput maximization is addressed through particle swarm optimization by considering the security, latency, and reliability constraints. Our results evidence the considerable improvements on the delay violation probability by increasing the number of antennas at Bob under strict buffer constraints. [ABSTRACT FROM AUTHOR]

A dual‐band dual circularly polarized (CP) patch antenna is proposed with low profile and small frequency ratio in this letter, which consists of a square patch, coupling lines, and a dual‐feed network with dispersive delay line. Noticing that this antenna is fabricated on a single‐layer substrate, thus acquiring low‐profile performance. As for the coupling scheme, the bandwidth of impedance matching is increased to achieve dual‐band radiation performance. On the premise that two orthogonal signals, which transmit in two paths of the dual‐feed network, provide equal magnitude, the circular polarization can be controlled by the corresponding phase difference. Benefited from the dispersive delay line, the requirements of quadrature phases are met to present left−/right‐handed circularly polarizations in two operating frequencies. Meanwhile, small frequency ratio can be easily achieved. To demonstrate the proposed design, the single‐layer antenna with a profile of 0.006λ0 is designed, fabricated and measured. The phase difference of two orthogonal signals is adjusted to −90° at the lower operating frequency 1.9 GHz to realize right‐handed CP characteristic, while 90° phase difference in two paths is achieved at the higher one 2.4 GHz to provide left‐handed CP characteristic. Measured results are found in reasonably a good agreement with the simulated ones. [ABSTRACT FROM AUTHOR]

Network densification is one of the most promising solutions to address the high data rate demands in 5G and beyond (B5G) wireless networks while ensuring an overall adequate quality of service. In this scenario, most users experience significant interference levels from neighbouring mobile stations (MSs) and access points (APs) making the use of advanced interference management techniques mandatory. Clustered interference alignment (IA) has been widely proposed to manage the interference in densely deployed scenarios with a large number of users. Nonetheless, the setups considered in previous works are still far from the densification levels envisaged for 5G/B5G networks that are considered in this paper. Moreover, prior designs of clustered-IA systems relied on oversimplified channel models and/or enforced single-stream transmission. In this paper, we explore an ultradense deployment of small cells (SCs) to provide coverage in 5G/B5G wireless networks. A novel cluster design based on a size-restricted k -means algorithm to divide the SCs into different clusters is proposed taking into account path loss and shadowing effects, thus providing a more realistic solution than those available in the current literature. Unlike previous works, this clustering method can also cater for spatial multiplexing scenarios. Also, several design parameters such as the number of transmit antennas, multiplexed data streams, and deployed APs are analyzed in order to identify trade-offs between performance and complexity. The relationship between density of network elements per area unit and performance is investigated, thus allowing to illustrate that there is an optimal coverage area value over which the network resources should be distributed. Moreover, it is shown that the spectral-efficiency degradation due to the intercluster interference in ultradense networks (UDNs) points to the need of designing an interference management algorithm that accounts for both intracluster and intercluster interferences. Simulation results provide key insights for the deployment of small cells in interference-limited dense scenarios. [ABSTRACT FROM AUTHOR]

In this work, we consider a multiple input multiple-output system with large-scale antenna array which creates unintended multiuser interference and increases the power consumption due to the large number of radio frequency (RF) chains. The antenna selective symbol level precoding design is developed by minimizing the symbol error rate (SER) with limits of available RF chains. The ℓ 0 -norm constrained nonconvex problem can be approximated as ℓ 1 -minimization, which is further solved by alternating direction method of multipliers (ADMM) approach. The basic ADMM scheme is mapped into iterative construction process where the optimum solution is obtained by taking deep learning network as building block. Moreover, because that the standard ADMM algorithm is sensitive to the selection of hyperparameters, we further introduce the back propagation process to train the parameters. Simulation results show that the proposed deep learning ADMM scheme can achieve significantly low SER performance with small activated subset of transmit antennas. [ABSTRACT FROM AUTHOR]

IoT system becomes a hot topic nowadays for smart home. IoT helps devices to communicate together without human intervention inside home, so it is offering many challenges. A new smart home IoT platform powered using electromagnetic energy harvesting is proposed in this paper. It contains a high gain transmitted antenna array and efficient circularly polarized array rectenna system to harvest enough power from any direction to increase lifetime of the batteries used in the IoT system. Optimized energy consumption, the software with adopting the Zigbee protocol of the sensor node, and a low-power microcontroller are used to operate in lower power modes. The proposed system has an 84.6-day lifetime which is approximately 10 times the lifetime for a similar system. On the other hand, the proposed power management circuit is operated at 0.3 V DC to boost the voltage to ~3.7 V from radio frequency energy harvesting and manage battery level to increase the battery lifetime. A predictive indoor environment monitoring system is designed based on a novel hybrid system to provide a nonstatic plan, approve energy consumption, and avoid failure of sensor nodes in a smart home. [ABSTRACT FROM AUTHOR]

In order to reduce the path loss of the wireless communication signal in the underground tunnel, a scheme for configuring the antenna polarization of wireless systems based on a zone-division method is proposed. A multimodal method is used to estimate the effect of antenna polarization on the wireless propagation. When the optimal polarization of the antenna leading to low path loss is different in the zones near and far from the transmitting antenna, a dividing point is used to separate the zones. Experiments are conducted in an underground mine. It shows that the results by the multimodal method are consistent with the real data. Compared with the existing coverage schemes, the proposed scheme can obtain better coverage. Meanwhile, zone division has an important influence on the optimized performance of the wireless coverage. The zones divided based on Fresnel zone clearance and system identification are too small or too large, which result in incorrect polarization switching and high path loss. [ABSTRACT FROM AUTHOR]

In this paper, a transmission scheme based on polarization filtering and weighted fractional Fourier transform (PF-WFRFT) is proposed to enhance the transmission security in wireless communications. Indeed, the distribution of the transmit signals processed by WFRFT can be close to Gaussian, which can significantly improve the low detection probability. However, through scanning the WFRFT order with small step size, an eavesdropper can restore a regular constellation and crack the information. To overcome the problem, in the PF-WFRFT scheme, two polarized signals with mutually orthogonal polarization state are utilized to convey the information, which are processed by WFRFT separately and added up linearly before being transmitted by dual-polarized antennas. In this manner, even by scanning the WFRFT order, recovered signals are composite ones, which make the WFRFT order and the signals' PSs difficult to crack, thus improving the security. In addition, the polarization-dependent loss (PDL) effect on the proposed scheme is discussed and a proprocessing matrix based on the channel information is constructed to eliminate this effect. Finally, numerical results are given to demonstrate the security performance of the proposed scheme in wireless communications. [ABSTRACT FROM AUTHOR]

The progress of spin rectification effect, which has the potential in powering the nanoscopic devices wirelessly, has been impeded by its low conversion efficiency. To solve this problem, a 5.8 GHz planar inverted F‐shaped antenna, which is designed to harvest radiated microwave power as well as foster a field enhanced area surrounding a permalloy (Py, Ni80Fe20) monolayer, is presented. The electric and magnetic field are enhanced by ~17.5‐fold and ~ 45‐fold, respectively. With the proposed antenna, a photovoltage of 0.85 μV can be detected in the monolayer 1.5 m away from the transmitting antenna, with input power of 30 dBm. This work provides an effective method to enhance the spin rectification effect signal in the far field region and paves the way for spintronic devices to be potentially utilized in practical wireless applications, such as quantum information, photovoltaics, and nanogenerator. [ABSTRACT FROM AUTHOR]

Multiple-input multiple-output (MIMO) antenna scheme is an effective technique for future terrestrial broadcasting systems such as digital video broadcasting-next-generation handheld (DVB-NGH) to overcome the limits on information theory of traditional single-antenna wireless communications without any additional bandwidth or increased transmit power. In this paper, we propose a hybrid beamforming scheme for dual-polarized MIMO spatial multiplexing DVB-NGH broadcasting systems. The system of interest makes use of phase shifters and amplitude attenuators for the digital-analog precoder at beamforming stage of the transmitter end to maximize the signal-to-noise ratio to increase the channel capacity of the DVB-NGH systems. At the receiver end, the maximum likelihood (ML) detector is used to evaluate the system performance. We consider the signal-to-interference-and-noise ratio (SINR) and the achievable average capacity for the DVB-NGH MIMO with various FFT sizes, number of transmit antennas, and different modulation schemes. The performance results on bit error rate, channel capacity, and beampatterns show that the proposed hybrid beamforming and dual-polarized MIMO spatial multiplexing schemes provide more robustness against signal interference by beamforming and/or nulling techniques. The simulation results also show that the proposed system achieves higher capacity than the existing MIMO schemes for the DVB-NGH systems. [ABSTRACT FROM AUTHOR]

Imaging and recognition of targets with complex maneuvers bring a new challenge to conventional radar applications. In this paper, the three-dimensional (3D) high-resolution image is attained in real-time by a Multiple-Input-Multiple-Output (MIMO) radar system with single Orthogonal-Frequency-Division-Multiplexing (OFDM) pulse. First, to build the orthogonal transmit waveform set for MIMO transmission, we utilize complex orthogonal designs (CODs) for OFDM subcarrier modulation. Based on the OFDM modulation, a preprocessing method is developed for transmit waveform separation without conventional matched filtering. The result array manifold is the Kronecker product of the steering vectors of subcarrier/transmit antenna/receive antenna uniform linear arrays (ULAs). Then, the high-resolution image of target is attained by the Multidimensional Unitary Estimation of Signal Parameters via Rotational Invariant Techniques (MD-UESPRIT) algorithm. The proposed imaging procedures include the multidimensional spatial smoothing, the unitary transform via backward-forward averaging, and the joint eigenvalue decomposition (JEVD) algorithm for automatically paired coordinates estimation. Simulation tests compare the reconstruction results with the conventional methods and analyze the estimation precision relative to signal-to-noise ratio (SNR), system parameters, and errors. [ABSTRACT FROM AUTHOR]

To further enhance frequency-asynchronous distributed Alamouti-coded (FADAC) orthogonal frequency division multiplexing (OFDM), we propose a new scheme which combines the partial maximum likelihood detection (PMLD) to the residual intercarrier interference cancellation (RIC). In order to decrease the performance gap from intercarrier interference- (ICI-) free level after single time iteration of the RIC, the final stage of the proposed scheme performs the PMLD limited to the symbols of less-reliable decision variables. We show that with the practically acceptable candidate symbol set size, a single iteration for RIC is enough to achieve the ICI-free performance. Moreover, the proposed scheme substantially expands the allowable ranges of the three undesirable terms, i.e., the timing and frequency offsets between the transmit antennas and the multipath delay spreads. [ABSTRACT FROM AUTHOR]

Hybrid precoding is a promising technology for massive multiple-input multiple-output (MIMO) systems. It can reduce the number of radio frequency (RF) chains. However, the power consumption is still very high owing to the large-scale antenna array. In this paper, we propose an energy-efficient precoding scheme based on antenna selection technology. The precoding scheme greatly increases the energy efficiency (EE) of the system. In the first step, we derive an exact closed-form expression of EE. Meanwhile, we further study the relationship between the number of transmit antennas and EE on the basis of the exact closed-form expression of EE. We prove that there exists an optimal value. When the number of transmit antennas equals to the value, the EE of the system can reach the maximum by a proper hybrid precoding scheme. Then, we propose an antenna selection algorithm to select antennas from the transmit antennas. And the number of selected antennas equals to the optimal value. Subsequently, we design the analog precoder based on a codebook to maximize the equivalent channel gain. At last, we further improve the EE by baseband digital precoding. The precoding algorithm we proposed offers a compromise between spectral efficiency (SE) and EE in millimeter wave (mmWave) massive MIMO systems. Finally, simulation results validate our theoretical analysis and show that a substantial EE gain can be obtained over the precoding scheme we proposed without large performance loss. [ABSTRACT FROM AUTHOR]

In order to understand how many antennas are needed in a multiuser massive MIMO system, theoretical derivation and channel measurements are conducted; the effect of a finite number of base station (BS) antennas on the performance capability of Zero-forcing (ZF) precoding in a rich scattering channel is quantified. Through the theoretical analysis, the needed number of the transmit antennas for ZF precoder to achieve a certain percentage of the broadcast channel (BC) capacity will monotonically decrease with the increase of the transmit signal-to-noise ratio (SNR), and the lower bound of the needed transmit antennas is derived with a simple expression. Then the theoretical derivation is verified by simulation results, and the transmission performance is evaluated by channel measurements in urban microcell (UMi) scenario with frequencies of 3.5 and 6 GHz. From the measurement results, the ZF capability can be enhanced by improving the SNR and enlarging the antenna array spacing when the massive MIMO channel does not under a favorable propagation condition. Furthermore, because of the lower spatial correlation, the performance of ZF precoding at 6 GHz is closer to the theoretical derivation than 3.5 GHz. [ABSTRACT FROM AUTHOR]

In recent years, the development market for low-cost nanosatellites has grown considerably. It has been made possible due to the availability of low-cost launch vectors and the use of "commercial off-the-shelf components" (COTS). The satellite design standardization has also helped a great deal to encourage subsystem reuse over a number of space missions. This has created numerous opportunities for small companies and universities to develop their own nanosatellite or satellite subsystems. Most COTS components are usually not space qualified. In order to make them work and withstand the harsh space environment, they need extra effort in circuit redesign and implementation. Also, by adopting the modularity concept and the design reuse method, the overall testing and nonrecurring development cost can be significantly reduced. This can also help minimize the subsystem testing times. The RF front-end design presented in this paper is also considered one of the better and feasible choices based on the above approach. It consists of an S-band transceiver that is fully implemented using COTS components. In the transmit chain, it is comprised of the transmitting CC2510 RF matching network and a power amplifier (PA) with an RF output power of up to 33 dBm which connects to an antenna using two RF switches. The receive chain starts from the antenna that is connected through two RF switches to the low-noise amplifier (LNA) that further connects to the receiving CC2510 via the RF matching network. The receiver sensitivity is -100 dBm. This is a half-duplex system using the same antenna for transmitting and receiving. The receiver and transmitter chains are isolated together using two RF switches which together provide an isolation of up to 90 dB at 2.4 GHz. The concept behind using two RF switches is to provide better isolation from the transmit chain to the LNA. The matching network of CC2510 has been designed in a symmetric fashion to avoid any delays. All the RF COTS used have been selected according to link budget requirements. The LNA, PA, and RF switches were tested individually for compliance. The passive components used in the overall design of the matching network are chosen on the basis of minimum dimension, least parasitic behaviour, and guaranteed optimum RF matching. Also, the RF COTS used are non-CMOS which makes them more robust against space radiations associated with the LEO environment and enables them to provide a radio communication data rate of up to 500 kbps in both uplink and downlink. The vacant spaces on the implemented PCB are shielded with a partial ground plane to avoid RF interference. [ABSTRACT FROM AUTHOR]

Non-Foster-loaded antennas have the advantages of compact size and large bandwidth. Meanwhile, they suffer from two issues: internal instability and simulation inaccuracy resulting from distribution parameters. The most commonly used stability analysis method for microwave circuits, Rollett's criteria, is not suitable for negative impedance circuits. This paper has explained the reason and proposed an effective method for stability analysis. Transmission lines between lumped components are found to be a main reason of inaccurate simulations, which is analyzed in this paper, and it is concluded that their influence also exists at hundreds of megahertz. In order to solve this problem and improve simulation accuracy, circuit and electromagnetic cosimulation is conducted. Finally, a 320 mm dipole loading with a negative capacitor is fabricated to verify the analysis. Simulated and measured results indicate that the proposed stability analysis is effective and the simulation accuracy is significantly improved. The matched dipole achieves less than −10 dB reflection coefficient from 30 MHz to 580 MHz. Furthermore, a 14 dB gain improvement is obtained in electrically small condition. [ABSTRACT FROM AUTHOR]

An investigation on the improvement of the resolution of a radar target identification system is presented in this paper. Degradation of resolution is mainly due to influence factors associated with antennas, including the strong coupling between transmitting and receiving antennas and the variation in the antenna response. A filtering technique was therefore introduced to mitigate the underlying problem. In the technique, the antenna effects were filtered out of the total response backscattered from the objects in the radar target identification system. The short-time matrix pencil method (STMPM) was then employed to extract the poles from the backscattered response in order to identify the object. Simulation and experimentation examples are illustrated to confirm the improvement of the resolution by filtering the antenna effects. The simulation and experimentation were divided into several categories, that is, different antennas and differently shaped objects, in order to validate the advantage of filtering the antenna effects. They were setup in order to demonstrate that the poles obtained from performing the STMPM without the filtering technique were mainly because of the antenna rather than the object’s characteristic. The results showed that the resolution of the identification was significantly increased when performing pole extraction and filtering the antenna effects. [ABSTRACT FROM AUTHOR]

The design, realization, and test of the transmitting and receiving antennas for an FMCW radar operating between 24 and 24.25 GHz (ISM band), to be housed in a white cane for improving mobility of visually impaired subjects, have been performed. The coaxial-to-microstrip transition necessary for feeding the antennas has been studied together with the characteristics of serial arrays of increasing number of patches. Based on this study, a serial array with 8 patches has been selected for the transmitting and receiving antennas. The realized structures show a reflection coefficient lower than −10 dB in the ISM band. When the antennas are attached to an FMCW radar board, the radar is able to record reflections from a metallic panel up to a 5 m distance. [ABSTRACT FROM AUTHOR]

Since the beginning of the 20th century a controversy has been continuously revived about the existence of the Zenneck Wave. This wave is a theoretical solution of Maxwell’s equations and might be propagated along the interface between the air and a dielectric medium. The expected weak attenuation at large distance explains the constant interest for this wave. Notably in the High Frequency band such a wave had been thought as a key point to reduce the high attenuation observed in High Frequency Surface Wave Radar. Despite many works on that topic and various experiments attempted during one century, there is still an alternation of statements between its existence and its nonexistence. We report here an experiment done during the optimisation of the transmitting antennas for Surface Wave Radars. Using an infrared method, we visualize a wave having the structure described by Zenneck above a metasurface located on a dielectric slab. [ABSTRACT FROM AUTHOR]

Modified transmit antenna selection (TAS)/orthogonal space-time block coding (OSTBC) (M-TAS/OSTBC) schemes have been shown to achieve superior error performance together with a reduced-rate feedback channel in the presence of feedback errors (FEs) when compared with the conventional TAS/OSTBC (C-TAS/OSTBC) schemes. This paper focuses on the bringing of fixed-gain amplify-and-forward (FGAF) relaying schemes that employ M-TAS/OSTBC schemes at both hops that provides reduced feedback-rate and robust error performance in the presence of erroneous-feedback channels. The exact expressions of the outage and error probabilities for both dual-hop FGAF relaying schemes in Nakagami- m fading channels have been derived and validated via Monte Carlo simulations. Additionally, with the help of high signal-to-noise ratio (SNR) (i.e., asymptotic) approaches and some analytical approximations, the asymptotic diversity order analysis has been carried out. Besides, by providing a simulation-based examination on the inclusion of power allocation within the modified scheme, the additional advantages on the performance have been exhibited. The extensive investigation and comparisons to the conventional schemes have shown that M-TAS/OSTBC schemes employed at each transmission link provide full diversity order and considerable error performance as the C-TAS/OSTBC scheme in ideal feedback cases and also achieve more robust error performance in the presence of FEs. Thus, by using M-TAS/OSTBC schemes, the overall performances of the dual-hop FGAF relaying schemes have been enhanced, which would result in reductions on the average SNR requirements to achieve a specified error rate constraint. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The average symbol error probability (ASEP) and outage probability (OP) performance of mobile-to-mobile (M2M) senor networks employing transmit antenna selection (TAS) and selection combining (SC) over N-Nakagami fading channels are investigated in this paper. Based on the moment generating function (MGF) approach, the exact ASEP expressions are derived for several modulation schemes. The exact closed-form OP expressions are also presented. Then, the ASEP and OP performance under different conditions are evaluated through numerical simulations to confirm the accuracy of the analysis. The simulation results show that the number of antennas, the fading coefficient, and the number of cascaded components have an important influence on the ASEP and OP performance. [ABSTRACT FROM AUTHOR]

An interesting phenomenon was noticed in some cases by workers operating with cranes in electromagnetic field of broadcasting antennas. They experienced electrical shock or burning pain at distances of kilometers away from powerful transmitters because cranes act as unintentional receiving antennas. The solution to this problem depends on dimensions and positioning of the crane structure, electromagnetic field strength at the site, frequency, and directional characteristic of the transmitting antenna. Electromagnetic interference between such structures is analyzed in this paper. Computational results for the induced currents and voltages in crane, treated as wire antenna problem, are determined using integrodifferential equations for the current along conductive structure, satisfying boundary condition for the electric field. Point matching method as the Method of Moments (MoM) is applied for solving these equations and polynomial approximation of the current is used. Results are presented for different crane structures and possible solutions to this problem are given. [ABSTRACT FROM AUTHOR]

Spectrum sensing and access have been widely investigated in cognitive radio network for the secondary users to efficiently utilize and share the spectrum licensed by the primary user. We propose a cluster-based adaptive multispectrum sensing and access strategy, in which the secondary users seeking to access the channel can select a set of channels to sense and access with adaptive sensing time. Specifically, the spectrum sensing and access problem is formulated into an optimization problem, which maximizes the utility of the secondary users and ensures sufficient protection of the primary users and the transmitting secondary users from unacceptable interference. Moreover, we explicitly calculate the expected number of channels that are detected to be idle, or being occupied by the primary users, or being occupied by the transmitting secondary users. Spectrum sharing with the primary and transmitting secondary users is accomplished by adapting the transmission power to keep the interference to an acceptable level. Simulation results demonstrate the effectiveness of our proposed sensing and access strategy as well as its advantage over conventional sensing and access methods in terms of improving the achieved throughput and keeping the sensing overhead low. [ABSTRACT FROM AUTHOR]

This article presents a method for determining the required number and locations of transmitting antennas (TXs) to optimize wireless propagation coverage in an indoor ultra wideband (UWB) communication system. In the coverage prediction model, we use the three-dimensional ray-tracing technique associated with a particle swarm optimization (PSO), and asynchronous particle swarm optimization (APSO) for optimizing the TXs location in an indoor environment. The three-dimensional ray tracing and optimization algorithm was applied in indoor environment to find the best location of the TXs by maximizing the power in the coverage area. A deployment is proposed to minimize the TXs and maximize the power in the coverage area. Simulation results illustrate the feasibility of using the integrated ray-tracing, and optimization methods to find the optimal transmitter locations in determining the optimized coverage of a wireless network. The APSO has better optimization results compared to the PSO and numerical results also show that the APSO outperforms the PSO in convergence speed. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013. [ABSTRACT FROM AUTHOR]

The problem of retrieving the Fresnel reflection coefficients of a half-space medium starting from measurements collected under a reflectionmodemultistatic configuration is dealt with. According to our previous results, reflection coefficient estimation is cast as the inversion of linear operator. However, here, we take a step ahead towards more realistic scenarios as the role of antennas (both transmitting and receiving) is embodied in the estimation procedure. Numerical results are presented to show the effectiveness of the method for different types of half-space media. [ABSTRACT FROM AUTHOR]

We discuss the mitigation of truncation errors in spherical-scanning measurements by use of a constrained least-squares estimation method. The main emphasis is the spherical harmonic representation of probe transmitting and receiving functions; however, our method is applicable to near-field measurement of electrically small antennas for which full-sphere data are either unreliable or unavailable. [ABSTRACT FROM AUTHOR]

The development of four-element ultra-wideband (UWB) comb taper slot antenna array with 18 cmelement spacing for real beam radar imaging is described. The four-element UWB array system with optimum element spacing is analyzed by energy pattern. A wideband double ridge horn antenna is used as the transmitting antenna, the developed large aperture UWB array is used as the receiving antenna. The transmitting antenna and the receiving antenna are combined with impulse time domain measurement system to achieve real beam radar imaging. The receiving impulse signals at various positions are processed by the time delay and sum algorithm. The examples of several aluminum cans have been verified in the resolution and compared with using the UWB array as a receive antenna and the double ridge horn as a transmit antenna in the test setup. The crossrange resolution of UWB antenna array is better than wideband double ridge horn antenna because the beam width of UWB array is narrower. [ABSTRACT FROM AUTHOR]

We present a new space-time encoder based on packet-level redundancy which can increase the space-time encoder rate beyond unity without compromising diversity gains. A complementary low-complexity decoding algorithm based on maximum ratio combining and successive interference cancelation is further proposed. A major merit of the decoding algorithm is that it allows to adaptively tradeoff between diversity and multiplexing gains based on the estimated channel parameters at the receiver without requiring any channel state information at the transmitter. System level simulation results give insight into the advantages of the proposed scheme when compared to its Alamouti and MIMO multiplexing based on single value decomposition counterparts. [ABSTRACT FROM AUTHOR]

We consider the problem of setting the uplink signal-to-noise-and-interference (SINR) target and allocating transmit powers for mobile stations inmulticell spatialmultiplexing wireless systems. Our aim is twofold: to evaluate the potential of suchmechanisms in networkmultiple inputmultiple output (MIMO) systems, and to develop scalable numerical schemes that allow real-time nearoptimal resource allocation across multiple sites.We formulate two versions of the SINR target and power allocation problem: one formaximizing the sum rate subject to power constraints, and one forminimizing the total power needed to meet a sum-rate target. To evaluate the potential of our approach, we perform a semianalytical study in Mathematica using the augmented Lagrangian penalty function method. We find that the gain of the joint optimum SINR setting and power allocation may be significant depending on the degree of fairness that we impose. We develop a numerical technique, based on successive convexification, for real-time optimization of SINR targets and transmit powers. We benchmark our procedure against the globally optimal solution and demonstrate consistently strong performance in realistic network MIMO scenarios. Finally, we study the impact of near optimal precoding in a multicell MIMO environment and find that precoding helps to reduce the sum transmit power while meeting a capacity target. [ABSTRACT FROM AUTHOR]

This paper proposes a two-phaseminimum mean-square-error bidirectional amplify-and forward (MMSE-BAF) relaying protocol to allow two sources exchange independent messages via a relay node equipped with multiple antennas. MMSE-BAF performs a joint linear MMSE filtering of the received signal after the multiple access phase before amplifying and forwarding the filtered signal using a single transmit antenna, possibly through a specific antenna selection procedure, during the broadcast phase. The proposed protocol extends upon the so-called analog network coding schemes in the literature in that it inherently exploits the multiple antennas at the relay station to reduce the noise enhancement typical of an AF protocol, and can also compensate for link imbalances between the relay and the sources and is agnostic to sources' modulation and coding schemes. We derive the instantaneous signal-to-noise ratio expressions for the received signal by the sources in the downlink and provide extensive linklevel simulations for the MMSE-BAF protocol subject to both frequency flat and selective fading. Furthermore, we pinpoint the modifications to be incorporated into the IEEE 802.16e orthogonal-frequency-divisionmultiple access (OFDMA) cellular standard (mobileWiMax) to enable support of multiantenna bidirectional communications and show that MMSE-BAF is a viable solution within that framework. [ABSTRACT FROM AUTHOR]

Multicell cooperation has been identified as one of the underlying principles for future wireless communication systems. This paper studies the benefits ofmulticell cooperation in broadcast TV network froman information theoretical perspective.We define outage capacity as the figure of merit and derive the broadcast coverage area to evaluate such system. Specifically, we calculate the broadcast coverage area with given common information rate and outage probabilities when multiple base stations collaboratively transmit the broadcast signals. For the generalMIMO case where receivers havemultiple antennas, we provide simulation results to illustrate the expanded coverage area. In all cases, our results show that the coverage of a TV broadcast network can be significantly improved by multicell cooperation. [ABSTRACT FROM AUTHOR]

The aim of this work is to get far field radiation patterns for any radiating source from transient acquisition, in a large frequency range. An outdoor transient Ultra-Wideband near-field measurement base will be installed, a single time pulse radiated by the source will cover the desired spectrum, and the accurate determination of far field radiations will be accomplished by means of cylindrical waves' modal development. This method uses simplified test equipments, easy to be installed, and it reduces measurement costs. [ABSTRACT FROM AUTHOR]