Multi-channel Wireless Communication Research Articles

Extreme Diffraction Management in Phase‐Corrected Gradient Metasurface by Fourier Harmonic Component Engineering

AbstractBeam diffraction management with on‐demand efficiency over compact devices is important in various applications, such as communications, spectroscopy, wireless power transfer, and others. Recently, the in‐depth study of metasurfaces, such as phase gradient metasurfaces (PGMs) or metagratings (MGs) made of discrete elements, has promoted an ultrathin platform to manipulate diffractions. However, most studies only focus on symmetrical diffraction orders or different propagating diffraction orders with equally distributed energy. It is difficult to efficiently excite beams with arbitrary energy distribution by phase‐only metasurfaces due to the complex optimization procedure. Here, to address these challenges, Fourier harmonic component engineering is proposed to allocate the energy between multiple diffraction beams. By introducing phase‐corrected gradient (PCG) on the metasurface platform, lossless transformation from the incidence to far‐field patterns can be obtained. A variety of diffraction situations are considered (symmetric and asymmetric, with equal or arbitrary energy ratio), where the simulated and measured far‐field patterns are in excellent agreement with the theoretical predictions and the achieved diffraction efficiency is up to 98.3%. The proposed method paves the way for multichannel wireless communication applications and can be readily extended to other frequency regions.

Dynamic pipelining for the loosely-coupled distributed constraint satisfaction problems

In the distributed constraint satisfaction problems (DCSPs), the elements of the problem, such as variables, domains and constraints, are distributed among a group of agents and thus, communications and coordination are needed for finding a solution. In this work, we consider the situation when the underlying constraint graph of the given DCSP consists of several components which are loosely-coupled (i.e. disconnected or connected via less-restrict constraints), and propose an approach to pipeline the solving processes on each component under the multi-channel wireless communication model.

Quad-OAM-beam based on a coding transmissive metasurface

A coding transmissive metasurface is presented for −1 mode quad-OAM-beam generation in 9.2–9.4 GHz. The 3bit metasurface is designed based on Pancharatnam−Berry (PB) phase principle, which is fed by a linear horn antenna. To satisfy the phase requirement of quad-OAM-beam, the phase compensation is introduced in the design for transmitting spherical waves into plane waves and promoting the directionality of incidence. The prototype of the metasurface is fabricated and measured. The experimental results coincide with theoretical analysis. Additionally, the OAM efficiency and purity are calculated to reveal the perfect performance of the metasurface. The proposed method has potential application in multi-channel wireless communication systems.

Multi-Channel Data Aggregation Scheduling Based on the Chaotic Firework Algorithm for the Battery-Free Wireless Sensor Network

The emergence of battery-free wireless sensor networks (benefiting from the ability to collect energy from the surroundings) has broken through the energy and lifetime limitations of traditional wireless sensor network systems, but also brings challenges to the sharing of network resources. In the multi-channel wireless communication environment, in particular, how to coordinate the communication time and occupied channels of a large number of sensor nodes from the perspective of optimizing the global network has become a research problem that must be solved. To reduce the transmission delay and the usage of wireless channels, a new multi-channel data aggregation scheduling method based on the chaotic firework algorithm is proposed in this paper. With the help of the generation function of feasible solutions, one scheduling set and a firework individual can be rapidly converted to each other. By the operations of firework explosions, the Gaussian mutation, and chaotic exploration, a sub-optimal scheduling set could be found during an acceptable time period. Finally, simulation results show that the new scheduling method has advantages in aggregation delay and occupied channels when compared with existing methods.

Limiting capabilities of two-dimensional plasmonics in electromagnetic wave detection

Plasmons in two-dimensional electron systems (2DESs) feature ultrastrong confinement and are expected to efficiently mediate the interactions between light and charge carriers. Despite these expectations, the electromagnetic detectors exploiting 2D plasmon resonance have been so far inferior to their nonresonant counterparts. Here, we theoretically analyze the origin of these failures, and suggest a proper niche for 2D plasmonics in electromagnetic wave detection. We find that a confined 2DES supporting plasmon resonance has an upper limit of absorption cross section, which is identical to that of simple metallic dipole antenna. Small size of plasmonic resonators implies their weak dipole moments and impeded coupling to free-space radiation. Achieving the ``dipole limit'' of the absorption cross section in isolated 2DES is possible either at unrealistically long carrier momentum relaxation times, or at resonant frequencies below units of terahertz. We further show that amendment of even small metal contacts to 2DES promotes the coupling and reduces the fundamental mode frequency. The contacted resonators can still have deep-subwavelength size. They can be merged into compact arrays of detectors responding resonantly to multiple frequencies. Such arrays may find applications in multichannel wireless communications, hyper-spectral imaging, and energy harvesting.

Multi-channel Optical Wireless Communication under the Effect of Low Electric Field

In this study, the multiple-input multiple-output (MIMO) technique is proposed to mitigate the influence of an external electric field on the free space optical (FSO) communication. The main advantages of the proposed technique are: decrease the attenuation (decrease bit error rate BER), improve data transmission at all divergence angles, and increase the quality (Q-factor) (even when it decreases at higher divergence angles). The importance of these results can be used to solve the problem of electric discharges that occurs on power transmission lines that interfere with the optical wireless system.

New functionality in microwave interferometry by application of metastructure as a tunable beam-splitter

A new functionality of microwave interferometry is demonstrated by application of metastructure, meta-surface or meta-atom as controlled original beam-splitter in modified interferometer on basis of h-plane waveguide tee. Specific selectively-tunable interference peaks are observed in transmission of microwaves due to influence of metastructure properties on shape, frequency and intensity of interference peak, when controlled structure resonance approaches interference peak. We investigated following structures as a beam-splitter: ferrite plate, individual conductive resonant element in the form of varactor-loaded butterfly dipole, and metastructure wire grating/varactor-loaded copper strip placed orthogonally. The obtained results open new possibilities to design microwave multifarious multiband spectral filtering and implement selective electric or magnetic tuning, required in multifunctional and multichannel wireless communication.

Novel design of smart sleep-lighting system for improving the sleep environment of children.

BACKGROUND: Children struggle to fall asleep by themselves because of their physiological characteristics. Therefore, research has been carried on various devices (such as a smartphone) to assist in improving the sleep quality of children. However, all such devices need to be controlled by parents and do not have functions for monitoring the sleep environment.OBJECTIVE: In this paper, a smart sleep-lighting system that includes a sleep-lighting device and a smartphone dongle is developed to improve the sleep environment of children.METHODS:The temperature, humidity, and luminance of the sleep environment are monitored and analyzed by the sleep-lighting device to control multi-color light and audio components. The colored light emitted by the multi-color light can be adjusted to improve the sleep atmosphere. Also, the audio component can play white noise to induce sleep. In addition, parents can use a smartphone dongle with a multi-channel wireless communication method to monitor and control one or more lighting devices in different locations in real time.RESULTS: For environmental monitoring, average difference between proposed device and commercial sensor from chamber setting temperature 15C to 35C was 0.588C 0.10C, and average error value of the humidity measurement was 0.74% at 40% 60% RH. Also, the manufactured sleep-lighting device shows good performance in multi-color light emission, and playing of white noise. As result, the smartphone connected to the proposed smartphone dongle enables monitoring and control of the proposed lighting device in a wireless well.CONCLUSIONS:The manufactured sleep-lighting device has a high-precision temperature and humidity sensor and a luminance sensor that can accurately monitor the sleeping environment. The lighting device can play white noise to induce sleep in children. Also, a multi-color LED light is operated via a smartphone application to improve the sleep atmosphere. The measured data will be sent to the lighting device and processed together with sleep environment data in order to improve the sleep quality. Additionally, the final system will be tested for real end-users with clinical experiments by sleep research center of a university hospital.

Optimal solution to intelligent multi-channel wireless communications using dynamic programming

With the booming increase of networking-oriented technologies, the implementation of the intelligent data has become a fashionable alternative for enterprises or organizations to create values or improve their existing offerings. However, communications are encountering restrictions caused by the limited energy supplies in mobile computing when the volume of the data requiring wireless transmissions keeps growing in a dramatic manner. This paper focuses on saving energy consumptions in wireless communications and presents a novel optimal solution to deploying multi-channel connections with minimum energy costs. Our approach is called Intelligent Multi-Channel Communication model, which is created to minimize the total energy cost when ensuring the performance meets efficiency demands. We implement experimental evaluations to examine the effectuation of our approach and find that the results meet our design expectations.

Performance Evaluation of MANET Using Multi-Channel MAC Framework

Major modern day computing and communication rely upon the underlying network used for data transportation. A strong and robust network is a prerequisite for communication oriented applications. One kind of communication networks used for data transportation known as Mobile ad hoc Networks (MANET) have been discussed in this paper and work has been done on their capability enhancement. Mobile ad hoc networks have evolved at a fast pace and provide efficient communication solutions when fixed communication infrastructure is not available and are easily deployable. Traditional mobile ad hoc network works on single wireless communication channel which limits their capacity and capability to handle very large or voluminous data. This limitation can be resolved using multiple physical communication channels. Number of protocols and techniques has been invented to incorporate multi-channel communication capabilities in wireless mobile ad hoc networks each with some pros and cons. In this paper a novel multi-channel wireless communication framework has been presented together with associated techniques and mechanisms. The proposed framework and protocols have been rigorously tested, evaluated and compared with existing benchmarked multi-channel ad hoc network protocols to establish the credibility of the framework.

Privacy-preserving wireless communications using bipartite matching in social big data

The enhanced wireless data transmissions have enabled the dramatical improvement of the service deployment, such as social networks and big data applications. The multi-channel wireless communication is one of the approaches for disseminating information when the user popularity is large in the dynamic and heterogeneous wireless networking environment. Channel Scheduling Controllers (CSCs) are vital components in data transmissions, which uses Nodes to arrange real-time task scheduling. However, a fixed communication scheduling can hardly meet the requirement of the higher-level privacy protections because of the conflict caused by the performance and security demands. To address this issue, this paper proposes a novel algorithm using communication management techniques for enhancing the security of the systems and supporting applications with real-time constraints. The experimental results depict that the proposed approach can reduce the security cost by up to 32.62% and 23.37% on average, respectively, compare to the traditional methods.

Cross-layer TCP/IP segmentation, re-routing and adaptive modulation techniques to exploit instantaneous BER variations on parallel subchannels

This paper describes a cross-layer technique for TCP-enabled multichannel wireless communications systems such as Multiple-Input Multiple-Output (MIMO) links. The technique uses adaptive modulation (AM) and different packet re-routing strategies over physically decomposed sub-channels to exploit time-varying channel conditions. The paper will demonstrate that combining both AM and packet re-routing mechanisms can improve the overall performance of MIMO systems where sub-channels possess unbalanced or uneven time-varying error rate characteristics. A simulated wireless communications system is developed to evaluate packet re-routing techniques over four sub-channel connections made available to the link layer. It then considers the effect of cross-layer link modulation adaptation switching. The system is investigated primarily in terms of goodput for several channel arrangements and characteristics, for various data rates and mean bit error rates. Based on the investigation results, this paper will demonstrate that even simple re-routing and AM mechanisms may be beneficial for systems utilising multiple antennas, as long as these expose the underlying sub-channels and their different instantaneous error characteristics to the link layer.

Model test study on monitoring dynamic process of slope failure through spatial sensor network

Landslides represent a major type of natural hazards worldwide. For development of risk mitigation capabilities, an effective system for monitoring dynamic process of slope failure, capable of gathering spatially distributed information before, during and after a landslide occurrence at real-time manner is essential. A spatial sensor network (SSN), which integrates the real-time communication infrastructure and observations from in situ sensors and remote sensing platforms, offers an efficient and effective approach for such purpose. In this paper, a SSN-based landslide monitoring system was designed and evaluated through a model test study conducted at Tongji University, China. This system, MUNOLD (MUlti-Sensor Network for Observing Landslide Disaster), has been designed as a comprehensive monitoring framework, including sensor observations, multi-channel wireless communication, remote data storage, visualization, data processing and data analysis. In this model test study, initial experimentation demonstrated the capabilities of the MUNOLD system for collecting real-time information about the dynamic process and propagation of slope failure. Innovatively, generated from the high-speed stereo images, the sequential surface deformation vector field can be created and may exhibit the dynamic process during the extremely critical and short period of the slope failure. After this model test study, the MUNOLD system is going to be further improved and extended in a landslide prone region in Sichuan Province, China.

Fast and efficient parallel‐shift water‐filling algorithm for power allocation in orthogonal frequency division multiplexing‐based underlay cognitive radios

Water-Filling (WF) is widely applied in power allocation in multichannel wireless communications. By mathematically linearising the optimal WF expression, the authors observe an intrinsic parallel-shift property of WF, based on which a fast and efficient WF algorithm is proposed. Compared with the conventional WF algorithms, it greatly simplifies WF execution by removing the Lagrange multiplier (or water-level) searching process. The authors further apply the proposed parallel-shift WF to solve the power allocation problem in orthogonal frequency division multiplexing (OFDM)-based underlay cognitive radios (CRs), with the objective of maximising the secondary user's throughput over all OFDM sub-channels under the transmit power and the interference constraints. To this end, the existing algorithm adopts an iterative binary searching process to find the solution, where the conventional WF algorithm with Lagrange multiplier searching is invoked in each iteration. In contrast, the authors propose a new power allocation algorithm to remove the iterative binary searching process. It runs the simplified parallel-shift WF only once, and then directly calculates the final solution using a power adjustment process (with the parallel-shift property as the underlying enabling mechanism). Numerical results show that both the proposed parallel-shift WF and the OFDM-based CR power allocation algorithms can run multiple times faster than the existing counterparts, and the gap on the running time increases with the total number of OFDM sub-channels in the system.

Fast Water-Filling for Agile Power Allocation in Multi-Channel Wireless Communications

In multi-channel wireless communications, Water-Filling (WF) is a fundamental power allocation mechanism for capacity maximization under a given total transmit power. In this letter, we propose simple and fast WF algorithms for achieving agile power allocation, such that the system can better match the dynamic nature of the wireless channels for a better performance. Our algorithms remove the need of water-level searching. Numerical results show that they can run multiple times faster than the existing ones and can converge to the optimal solution in a few linear calculations.

An FET-based microwave active circuit with dual-band negative group delay

Recent studies proved that certain electronic active circuits are capable to exhibit simultaneously a negative group delay (NGD) and amplification in microwave frequency bands. One of the simplest topologies generating this counterintuitive NGD function effect is formed by a series RLC-network in cascade with a transistor. By using this cell, similar to the classical electronic functions, dual-band NGD microwave devices with loss compensation possibility can be designed. Theoretic demonstrations concerning the theory of the NGD circuit considered are presented. The dual-band NGD concept feasibility is concretely illustrated by an example of EM/circuit co-simulations. So, in frequency domain, dual-band NGD with minimal values of about -1 ns was observed simultaneously within two frequency bands centered at about 1.05 GHz and 2.05 GHz. To highlight the functioning of the hybrid device considered, time-domain analysis showing the RF/microwave signal advancement is performed. As application, the concept investigated can be envisaged for data synchronization in multi-channel wireless communication systems eventually degraded by undesired EMI effects.

A 1.2‐ to 3‐GHz tunable feedforward amplifier using broadband distributed phase shifters

AbstractIn this article, we demonstrate a broadband tunable feedforward amplifier design.For any frequency between 1.2 and 3 GHz, the third order intermodulation distortion (IMD) is reduced up to 18dB and the circuit maintains the spurious free dynamic range over 60 dBc at the output. This technique utilizes the combination of a broadband distributed‐element phase shifter (DPS) and a radio frequency feedforward approach to achieve a wideband linearization. The key element is a low‐loss, broadband and 360° changeable DPS. Because of its broadband tunable IMD cancellation capability, the proposed design will be very useful in multimode and multi channel wireless communication systems where the high power output with minimized distortion is needed. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:250–254, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26445

A high-speed adaptive antenna array with simultaneous multibeam-forming capability

A new type of adaptive beamforming antenna system architecture is proposed for multichannel wireless communications. Multibeam communication with high data throughput is accomplished using the proposed beamformer architecture. The system consists of analog mixers, a multitone direct digital synthesizer (DDS), and a digital signal processor (DSP) controller. The essential idea of multibeam forming is based on a multitone weighting scheme combined with analog-digital hybrid signal processing. While the real-time multibeam construction is realized by the analog mixer circuits and a DDS, the complicated adaptive beamforming and direction-of-arrival estimation algorithms are carried out by the DSP. In this architecture, only one beamformer circuit is required to handle multiple beams, leading to significant reduction in hardware counts. A 5.8-GHz eight-element adaptive beamforming array successfully demonstrates two-beam simultaneous beamforming with less than three degrees of peak and null steering errors and more than 20-dB interference suppression. The test-bed exhibits successful two-channel data recovery at 25-Mb/s data throughput in each channel with binary phase-shift keying modulation, for simultaneous dual-beam reception. The bit-error-rate measurement validates the robustness of the communication quality under strong interferences.