Improve Transmission Capacity Research Articles

Research on Step-down Resonance Suppression and Filtering Device

In recent years, offshore wind farms have developed rapidly, and their installed capacity is getting bigger and bigger, and the offshore distance is getting farther and farther. In order to meet the needs of large-capacity and long-distance offshore wind power transmission, the AC submarine cable has the characteristics of long distance, high voltage and large cross-section. Along with the significantly improved transmission capacity, its equivalent capacitance is also increasing, which further reduces the resonance frequency of the offshore wind power AC transmission system. If the parallel resonance frequency of the offshore wind power transmission system is close to the main harmonic current frequency band of wind turbines, it will cause harmful system resonance and harmonic amplification, significantly increasing the harmonic current of grid-connected lines and the voltage distortion rate of nodes in nearby power grids, and seriously affect the safety of equipment and the safe and stable operation of offshore wind power transmission system. A step-down resonance suppression filtering device applied to the offshore wind power transmission system is proposed. The AC cable is connected to the low-voltage 35 kV side of the compensation winding of the centralized control center to eliminate the resonance risk of the 220 kV system and filter out the harmonic current. Compared with the existing technical scheme, the device has the advantages of simple control, reliable operation, stable resonance suppression effect, low operation loss and the like, and has great engineering popularization value.

A Weakly-Coupled Double Bow-Tie Multi-Ring Elliptical Core Multi-Mode Fiber for Mode Division Multiplexing across C+L+U Band

We herein present a weakly-coupled double bow-tie multi-ring elliptical core multi-mode fiber (DBT-MREC-MMF) supporting 22 eigenmodes for mode division multiplexing across the C+L+U band. The proposed fiber introduces a multi-ring elliptical core, bow-tie air holes, and bow-tie stress-applying areas to effectively split adjacent eigenmodes. By utilizing the finite element method (FEM), we accordingly optimized the fiber to support the 22 modes under the weakly-coupled condition. We evaluated the impact of fiber parameters on the minimum effective refractive index difference (min Δneff) between adjacent eigenmodes, model birefringence (Bm), and bending loss at a wavelength of 1550 nm. Additionally, broadband performance metrics, such as effective modal index (neff), effective index difference (Δneff), effective mode area (Aeff), differential mode delay (DMD), and chromatic dispersion (D), were comprehensively studied over the entire C+L+U band, ranging from 1530 to 1675 nm. The proposed fiber is capable of supporting 22 completely separated eigenmodes with a min Δneff between adjacent eigenmodes larger than 3.089 × 10−4 over the entire C+L+U band. The proposed DBT-MREC-MMF holds great potential for use in short-haul communication systems that require MDM to improve transmission capacity and expand bandwidth.

Investigations on design limits and improved material utilization of press-fit connections using elastic-plastic design

Today, there are a number of analytical and numerical calculation methods for the elastic-plastic design of press-fit connections. However, these are largely constrained by their restriction to elastic-ideal-plastic material behavior. In addition, recommendations for limiting the plasticized hub cross section that have been provided to date do not exploit the full potential of the materials, with the result that opportunities for lightweight design and improved transmission capacity have remained unused so far. Yet, no experimental validations exist to this end, which is why the existing design method could not be validated until today. In addition, there is still a lack of research on how to evaluate the potential for increasing the force and torque transmission under consideration of the strain hardening of the material during plastic deformation. The lack of knowledge today prevents a targeted design and thereby the industrial application of this type of connection; the transmission capacity and lightweight design potentials have thus remained unused until now (Kröger and Binz, 2020). This article presents the actual design and joining limits of hubs made of EN AW-5083 (AlMg4,5Mn), which were determined as part of an Industrial Collective Research (IGF) project. This allows the hub materials to be better utilized, which leads to a reduction in mass and/or an increase in the force and torque transmission. In addition, the experimental validation of the numerical investigations helps to establish the design method in industrial practice.

Design of weakly coupled 20-eigenmode bow-tie rectangular dual-step fiber for short-haul communication in O band

We present a weakly coupled bow-tie rectangular dual-step few-mode fiber supporting 20 eigenmodes for short-haul communication systems across the O band. The rectangular dual-step core and bow-tie stress-applying area are introduced to effectively split adjacent eigenmodes. We evaluate the impact of parameters on modal mode effective refractive index difference (MERID) Δneff, min Δneff, min Aeff, Bm, and bending loss at a wavelength of 1310 nm. Broadband performance of the entire O band, including neff, MERID Δneff, differential mode delay, and dispersion, is also analyzed. Results indicate that the 20 eigenmodes supported by the designed fiber are completely separated with MERID Δneff between adjacent modes larger than 2.319 × 10 − 4 over the whole O band. The designed fiber can be used for short-haul multiple-input multiple-output-free eigenmode-division multiplexing systems to improve transmission capacity and expand bandwidth.

Design of a side-hole-assisted weakly coupled rectangular ring-core multimode fiber for mode-division-multiplexing networks.

We present a side-hole-assisted weakly coupled polarization-maintaining rectangular ring-core multimode fiber supporting 68 eigenmodes. The rectangular ring-core and side-hole structures are introduced to effectively split eigenmodes. The impact of parameters on mode utilization rate η and mode number is evaluated at the wavelength of 1550 nm. We also analyze bending loss and broadband performance of the entire C band, including neff, Δneff, Aeff, nonlinearity, and differential mode delay. By optimizing the design parameters, the 68 eigenmodes are completely separated with Δneff between adjacent modes larger than 10-4 over the whole C band. The designed fiber can be used for eigenmode-division multiplexing networks to improve transmission capacity and spectral utilization.

Evaluation of optimal UPFC allocation for improving transmission capacity

A unified power flow controller (UPFC) combines the advantages of various flexible alternating current transmission system (FACTS) devices into a powerful format. Using a 500 kV power grid, this study evaluates the selection and use of a UPFC to improve transmission capacity. The “UPFC unit capacity control proportionality coefficient” is introduced to quantify the control effect of the UPFC, and an optimal calculation method for the UPFC capacity is presented. Following the proposal of a UPFC site selection process, the data of an existing power grid is used to conduct simulations. The simulation results show that the UPFC has a strong ability to improve transmission capacity, and its use is greatly advantageous. Additionally, by applying the proposed selection method, the control effect and economic benefits of the UPFC can be comprehensively considered during project site selection. These findings have a guiding significance for UPFC site selection in ultra-high voltage power grids.

Fragmentation and time aware algorithms in spectrum and spatial assignment for space division multiplexed elastic optical networks (SDM-EON)

The Space Division Multiplexing with Elastic Optical Networks (SDM-EON) is one of the newest networks to improve transmission capacity and prepare more flexibility compared to conventional EON networks. In SDM-EON, arriving connection demands could be setup efficiently. We consider a multi-core fiber (MCF)-enabled elastic optical network. We introduce two novel metrics as holding time metric (HTM) and coefficient of variant metric (CVM). Based on these metrics, three novel algorithms are introduced to resolve the fragmentation problem and improve blocking probability in SDM-EON; called Coefficient of Variant Metric (CVM); Holding Time Metric (HTM); and Moderate Coefficient of Variant Metric and Holding Time Metric (Mod_CVM_HTM) algorithms. According to our performance evaluation results, our proposed algorithms can reduce blocking probability (BP).

Improvement of optical fiber channel capacity using compressed non-orthogonal frequency quadrature amplitude modulation

Abstract A new modulation scheme, that can increase the channel capacity of optical fiber link, is proposed in this paper. It is implemented by using a non-orthogonal frequency shift keying (FSK), quadrature amplitude modulation (QAM), and sparse sinusoidal sampling based on a compressed sensing. The proposed technique can allow us to have the improved transmission capacity because frequency spacing among digitally sample RF subcarriers becomes much narrower than the channel bandwidth by the non-orthogonality and the total signal length can be reduced by using the sparse sinusoidal sampling. For experimental verification, a 64-non-orthogonal frequency quadrature amplitude modulation (NoFQAM) signal is generated using non-orthogonal 4-FSK and 16-QAM. The total length of 64-NoFQAM signal is reduced up to 60% at the bit error rate (BER) of 4 × 10−5 by the sparse sinusoidal sampling. The BER of 2 × 10−5 was measured at a frequency spacing between digitally sampled RF subcarriers corresponding to 10% of channel bandwidth (500 MHz). The 7.5-Gb/s transmission of 64-NoFQAM signal with the channel bandwidth of 500 MHz was demonstrated successfully by using 50-km and 300-km optical fiber link.

Routing using reinforcement learning in vehicular ad hoc networks

AbstractIn vehicular ad hoc networks (VANETs), the frequent change in vehicle mobility creates dynamic changes in communication link and topology of the network. Hence, the key challenge is to address and resolve longer transmission delays and reduced transmission stability. During the establishment of routing path, the focus of entire research is on traffic detection and road selection with high traffic density for increased packet transmission. This reduces the transmission delays and avoids carry‐and‐forward scenarios; however, these techniques fail in obtaining accurate traffic density in real‐time scenario due to rapid change in traffic density. Thus, it is necessary to create a model that efficiently monitors the traffic density and assist VANETs in route selection in an automated way with increased accuracy. In this article, a novel machine learning architecture using deep reinforcement learning (DRL) model is proposed to monitor and estimate the data essential for the routing protocol. In this model, the roadside unit maintains the traffic information on roads using DRL. The DRL predicts the movement of the vehicle and makes a suitable routing path for transmitting the packets with improved transmission capacity. It further uses predicted transmission delays and the destination location to choose the forwarding directions between two road safety units (RSUs). The application of DRL over VANETs yields increased network performance, which provides on‐demand routing information. The simulation results show that the DRL‐based routing is effective in routing the data packets between the source and destination vehicles than other existing method.

3D Fragmentation Metric and RCSA Scheme for Space Division Multiplexing Elastic Optical Networks

The space division multiplexing elastic optical networks (SDM-EONs) based on multi-core fiber (MCF) are an effective solution to improve transmission capacity. In SDM-EONs, spectrum resources take on three-dimensional (3D) properties (i.e., frequency, time, and space), which brings new spatial constraints to network resource allocation. Meanwhile, the spectrum fragmentation in the network also presents same characteristics with the setup and release of dynamic lightpath. To improve the success rate of transmission and the utilization of network resources, it is necessary to evaluate network fragmentation effectively from the three dimension. Therefore, this paper focuses on a new fragmentation measurement for SDM-EONs. Firstly, the 3D fragmentation metric is carried out considering the frequency-time-space domain. Then, routing, core, and spectrum allocation (RCSA) scheme is proposed to allocate the spectrum resource with minimal future fragmentation and core resource with maximal free resource reservation. Simulation results show the proposed scheme better in blocking probability, spectrum utilization, and fragmentation rate.

The Research Progress in On-Chip Mode (De)multiplexer

With the increasing integration of communication devices and the demand for communication capacity, the methods to increase bandwidth and transmission capacity have attracted lots of attentions. As a new multiplexing dimension, mode division multiplexing (MDM) can effectively improve transmission capacity, in which different modes are utilized for data transmission. In this paper, we investigate the recent progress in on-chip mode (de)multiplexer, which is the key technology to realize mode (de)multiplexing. Firstly, several traditional on-chip mode (de)multiplexers are introduced, including mode (de)multiplexers based on Multi-Mode Interference (MMI), Adiabatic Coupler, Asymmetric Y-Junction, Asymmetry Directional Coupler (ADC) and Micro-ring Resonator (MMR), respectively. Secondly, hybrid (de)multiplexers combining MDM with Polarization Division Multiplexing (PDM) or Wavelength Division Multiplexing (WDM) are discussed. Finally, this paper looks forward to the development prospects of on-chip mode multiplexing technology.

Electromagnetic Characteristics Analysis of Tri-Axial HTS Cables Based on PEEC Approach

The tri-axial high-temperature superconducting (HTS) cable is the key factor to improve transmission capacity and to optimize the structure of smart grid. The HTS devices generally have large current-carrying capacity. Therefore, the electromagnetic characteristic of a composite superconducting cable with high current density becomes a key point for the application of these HTS devices. In this paper, in order to derive the electromagnetic characteristics and voltage reflection mechanism of HTS cable with fast stable convergence, the optimized equivalent estimation model for the distributed impedance and inductance parameters of HTS cable's conductor layer and shielding layer is put forward based on the optimal vector fitting algorithm with the novel partial element equivalent circuit approach, which could precisely identify the frequency-dependent stray parameters with the iteration computation of a rational function approximation via poles and residues. Accordingly, the dynamic influence behavior of the distributed parameters on the mechanism of HTS cable's electromagnetic characteristics is theoretically discussed in the paper for a complicated power system, and the feasibility and accuracy of the proposed conducted electromagnetic interference estimation method are also verified via a numerical computation and a performance experiment.

Subcarrier Index-Power Modulated-Optical OFDM With Dual Superposition Multiplexing for Directly Modulated DFB-Based IMDD PON Systems

A low-signal-modulation format-enabled highly spectrally efficient new transmission technique termed subcarrier index-power modulated optical OFDM with dual superposition multiplexing (SIPM-OOFDM-DSPM) is proposed and investigated, for the first time, in intensity modulation and direct detection (IMDD) passive optical network (PON) systems incorporating directly modulated DFB lasers (DMLs). The DSPM operation passively adds two low-signal-modulation format-encoded complex numbers and assigns the sum to subcarrier index-power modulation (SIPM)-generated low- and high-power subcarriers. Detailed numerical explorations of SIPM-OOFDM-DSPM performances over additive white Gaussian noise channels are undertaken, based on which optimum key transceiver parameters are identified. In comparison with previously published techniques, over simple DML-based IMDD PON systems, SIPM-OOFDM-DSPM considerably improves the signal transmission capacity, system power budget, and performance tolerance to both chromatic dispersion and fiber nonlinearity. The work suggests that SIPM-OOFDM-DSPM is a promising signal transmission technique capable of providing cost-sensitive PON systems with improved transmission capacity, performance flexibility, and adaptability.

Spectral function modulation based on nonlinear frequency division multiplexing

A combination of phase and amplitude modulation in nonlinear discrete spectrum is proposed based on nonlinear frequency division multiplexing. Here the integrable nonlinear Schrodinger equation is used as the channel model. We propose the transmission system with designed transmitting signals and implement our scheme with simulation. We use 8QAM constellation and 2 eigenvalues to generate 5 bit signals, which greatly improve spectral efficiency. This method can be expanded for higher order modulation and further improve transmission capacity in limited bandwidth.

White LED-based optical wireless link with improved transmission capacity using nonorthogonal multiamplitude phase frequency modulation

A nonorthogonal amplitude, phase, and frequency modulation (APFM) technique that can increase the transmission capacity of an optical wireless link based on white light-emitting diode (LED) is proposed. It is implemented by the simultaneous use of nonorthogonal frequency shift keying (FSK) and quadrature amplitude modulation (QAM). A white LED-based wireless link using a 64-APFM scheme is constructed to experimentally verify the proposed technique, where the 64-APFM scheme is implemented by the combination of nonorthogonal 4-FSK and 16-QAM. Two more bits per symbol are transmitted using the proposed scheme with the same bandwidth of QAM. No intercarrier interference effect is observed at the 0.02-% frequency spacing (0.001 MHz) for the used RF carrier (5 MHz) because the correlation between the received 64-APFM signal and only one carrier at a time is accomplished with the help of digital signal processing. 6 - Mbit / s ( 1 - Msymbol / s ) data are successfully transmitted through an optical wireless channel with a limited bandwidth of 1 MHz. This indicates that six bits per symbol can be transmitted using the proposed APFM technique at the same physical bandwidth as 16-QAM.

White light-emitting diode based wireless orthogonal frequency division multiplexing link with improved transmission capacity using Bayesian compressive sensing

We propose a technique that improves the channel capacity of an optical wireless orthogonal frequency division multiplexing (OFDM) transmission, which employs a visible light-emitting diode. An OFDM waveform encoded by quadrature phase shift keying (QPSK) or 16-quadrature amplitude modulation is compressed and then transformed into a sparse waveform using a proposed advanced systematic sampling. At the optical wireless receiver, the original waveform is recovered by L 1 -minimization based on a Bayesian compressive sensing. Our experimental results show the significant increase in the channel capacity from 31.12 to 51.87 Mbit/s at forward error correction limit (i.e., error vector magnitude of 32%) in case of QPSK symbols.

English

In recent years, a number of Flexible AC Transmission system (FACTS) devices have been proposed for better utilization and enhancing the power transfer capability of existing power transmission network. There are several conventional methods to improve the voltage profile and annual savings, but FACTS devices are shown better results to improve transmission line performance such as power profile and annual savings. The ability to enhance power transfers lead to their applications in a multi machine power system for the purpose of an overall reduction in power generation cost, compared to others. This paper focus on the evolution of economic viability for reducing generation cost using FACTS devices. The most and versatile FACTS devices, such as Static Var Compensator (SVC), Thyristor Controlled Series Capacitor (TCSC) and Unified Power Flow Controller (UPFC) are used to improve transmission capacity of the system. The devices are incorporated in the system by the Optimal Power Flow method and Genetic Algorithm based optimization technique. The proposed methods are tested on IEEE-57 bus system and the corresponding test results are compared with conventional method.

On-Demand Spectrum and Core Allocation for Reducing Crosstalk in Multicore Fibers in Elastic Optical Networks

In the past few years, many researchers have studied elastic optical networks, which exhibit a dramatically improved transmission capacity compared with conventional optical networks. However, the transmission capacity per fiber will soon reach the physical limit for traditional single-mode fibers. Multicore fiber (MCF) is among the innovative fibers based on space-division multiplexing technology. MCF has multiple cores and achieves a far larger transmission capacity than traditional single-mode fibers. However, signals transmitted in these crowded multiple cores interfere with each other and are degraded. This degradation has a serious impact on the network resource management in elastic optical networks. Previous research indicates that the crosstalk effect of MCF is dependent on an arrangement of signals regarding the spectrum and core. Therefore, we approach the problem of the crosstalk in MCF with regard to the spectrum and core allocation, from the network perspective. First, this paper summarizes the related work regarding elastic optical networks and MCFs. Next, we propose an “on-demand” spectrum and core allocation method that reduces both the crosstalk and fragmentation in elastic optical networks with MCFs. This proposed method is based on two predefined policies related to the crosstalk and fragmentation. The first, the core prioritization policy, is based on the MCF’s structure, and the other is a core classification policy based on the required bandwidth of the connections. The core prioritization policy realizes the core allocation that reduces crosstalk by avoiding filling adjacent cores. The core classification policy reduces the spectrum fragmentation by allocating a uniform bandwidth connection for each core. Finally, we evaluate the proposed method using computer simulations. The results indicate that the proposed method can, under various network conditions, improve both the crosstalk and blocking probability of the total network through our two policies.

Adaptive Scheduling in MIMO-Based Heterogeneous Ad Hoc Networks

The demands for data rate and transmission reliability constantly increase with the explosive use of wireless devices and the advancement of mobile computing techniques. Multiple-input and multiple-output (MIMO) technique is considered as one of the most promising wireless technologies that can significantly improve transmission capacity and reliability. Many emerging mobile wireless applications require peer-to-peer transmissions over an ad hoc network, where the nodes often have a different number of antennas, and the channel condition and network topology vary over time. It is important and challenging to develop efficient schemes to coordinate transmission resource sharing among a heterogeneous group of nodes over an infrastructure-free mobile ad hoc network. In this work, we propose a holistic scheduling algorithm that can adaptively select different transmission strategies based on the node types and channel conditions to effectively relieve the bottleneck effect caused by nodes with smaller antenna arrays, and avoid the transmission failure due to the violation of lower degree of freedom constraint resulted from the channel dependency. The algorithm also takes advantage of channel information to opportunistically schedule cooperative spatial multiplexed transmissions between nodes and provide special transmission support for higher priority nodes with weak channels, so that the data rate of the network can be maximized while user transmission quality requirement is supported. The performance of our algorithm is studied through extensive simulations and the results demonstrate that our algorithm is very effective in handling node heterogeneity and channel constraint, and can significantly increase the throughput while reducing the transmission delay.

A Novel Optical Orthogonal Modulation Format Based on Differential Phase-Shift Keying and Code-Shift Keying

We propose a novel orthogonal modulation format with differential phase-shift keying (DPSK) and code-shift keying (CSK) to improve transmission capacity of the optical code-based communication system. A 2-bit/symbol 10-Gb/s system with DBPSK/binary-CSK modulation is demonstrated.