Switching Node Research Articles

Multi-Controller Deployment in SDN-Enabled 6G Space–Air–Ground Integrated Network

The space–air–ground Integrated Network (SAGIN) is considered to be a significant framework for realizing the vision of “6G intelligent connection of all things”. The birth of 6G SAGIN also brings many problems, such as ultra-dense dense networks, leading to a decrease in the efficiency of traditional flat network management, and traditional satellite networking solidified network functions, etc. Therefore, combining the 6G SAGIN network with the software-defined network (SDN) is an excellent solution. However, the satellite network topology changes dynamically and the ground user unbalanced distribution leads to the unbalanced load of the SDN controller, which further leads to the increased communication delay and throughput drop, etc. For these problems, a hierarchical multi-controller deployment strategy of an SDN-based 6G SAGIN is proposed. Firstly, the delay model of the network, the load model of the SDN controller, and a loss value as a measure of whether the network delay and controller load are optimal are defined. Then, using the distribution relationship between the SDN controller and the switch node as the solution space, and taking the loss value as the optimization goal, a multi-controller deployment strategy based on the simulated annealing algorithm is used to search for the optimal solution space. Lastly, considering the network topology changes dynamically and the SDN controller imbalance, a switch migration strategy oriented toward load balancing is proposed. We aimed to determine the controller deployment plan through the above two points, balance the controller load, and then improve the network performance. The simulation results show that the controller load is increased by about 7.71% compared to OCLDS, and the running time is increased by 17.7% compared to n-k-means.

Demonstration of a Hybrid Analog–Digital Transport System Architecture for 5G and Beyond Networks

In future mobile networks, the evolution of optical transport architectures enabling the flexible, scalable interconnection of Baseband Units (BBUs) and Radio Units (RUs) with heterogeneous interfaces is a significant issue. In this paper, we propose a multi-technology hybrid transport architecture that comprises both analog and digital-Radio over Fiber (RoF) mobile network segments relying on a dynamically reconfigurable optical switching node. As a step forward, the integration of the discussed network layout into an existing mobile infrastructure is demonstrated, enabling the support of real-world services through both standard digital and Analog–Intermediate- Frequency over Fiber (A-IFoF)-based converged fiber–wireless paths. Emphasis has been placed on the implementation of a real-time A-IFoF transceiver that is employed through a single embedded fully programmable gateway array (FPGA)-based platform that serves as an Ethernet to Intermediate Frequency (IF) bridge for the transmission of legacy traffic over the analog network segment. The experimental evaluation of the proposed concept was based on the dynamic optical routing of the legacy Common Public Radio Interface (CPRI), 1.5 GBaud analog-intermediate frequency-over-fiber (A-IFoF)/mmWave and 10 Gbps binary optical waveforms, showing acceptable error vector magnitude (EVM) values for the complex radio waveforms and error-free operation for binary optical streams, with Bit Error Rate (BER) values less than 10−9. Finally, the end-to-end proof-of-concept demonstration of the proposed solution was achieved through the delivery of 4K video streaming and Internet Protocol (IP) calls over a mobile core network.

Analysis of optical networks in presence of nodes noise and crosstalk

Abstract Optical packet switching has gained lot of momentum in last decade due to the advantages of optical fiber over copper cables. Optical switching is beneficial in optical networks which form connections of links and switching nodes. In these high speed networks minimum delay and high throughput are two important parameters which are considered. To minimize network delay shortest path algorithm is used for route selections. In previous studies while choosing shortest path distance among various nodes is considered. In this work we have shown that it is necessary to consider both distance and number of hops while choosing path from source to destination to minimize power per bit used for the transmission.

Identification of Structural Reliability Parameters in Distributed Telecommunication System

The article considers estimation of structural parameters for communication network. The article aims to calculate the key indicators of structural reliability. Proposed method consists of mathematical expectation estimation for number of connections and connectivity probability in different structured networks. The methodology is based on solution to the problem of network optimization structure for reliability view. Classification of equipment is proposed in terms of failure impact on quality management of network traffic. According to the accepted classification, reliability parameters are listed characterizing each of the classified equipment groups. Reliability parameters are divided into single and complex ones. The reliability and quality of the communication network functioning is assessed by the estimated values of these parameters. A probabilistic graph of network model and state diagram of communication lines for one hierarchical level were plotted. When plotting, it was assumed that switching nodes are absolutely reliable. The reliability of communication lines is expressed in terms of availability. The calculation of parameters was carried out on the assumption that communication line failures are statistically independent events. Reliability indicators are estimated, such as the probability of connectivity between each pair of telecommunication nodes and the absolute value of mathematical expectation for number of connections. For convenience, practical application of the proposed method, calculation results of the mathematical expectation of number of connections is expressed as a percentage. The article considers a mathematical model of the functioning of a separate communication line with the absolute reliability of the system for monitoring its technical condition. The mathematical model is presented in the form of a state diagram. It is assumed that the network monitoring system performs the functions of periodic and continuous monitoring. A method for calculating complex indicators of reliability, such as the availability factor and the downtime factor, is proposed. The calculation method is based on the matrix method for analyzing probabilistic systems. The calculation formulas include statistical data from the system for monitoring the technical condition of communication lines. Modelling is used to simulate the process of communication network functioning in experimental research. The process of communication network functioning is simulated. Depending on the incoming load, a search for free algorithmic resources and communication lines is performed. The calculation of the reliability indicators of the selected way of servicing calls is performed, taking into account the selection criterion set by the program. The monitor displays a dependency graph of the reliability indicators on the intensity of the incoming load. The calculation of the relative statistical frequency of the success of servicing requests is carried out, and the frequency of communication lines failure is also calculated. The program output is proposals for communication network reconstruction due to network resources redistribution.

Fault-Tolerant Embedding Algorithm for Node Failure in Airborne Tactical Network Virtualization

Airborne tactical networks (ATNs) are driving the promising development of Internet of Battle things by enabling efficient information sharing, which is impeded by the network ossification problem that is deep-rooted in the tightly coupled network architecture. As a solution, network virtualization (NV) can break the tight coupling between applications and network infrastructure, providing a more flexible and scalable architecture for ATNs. With complex interference and malicious attacks, the application of NV is challenged by network failures when instantiating multiple virtual networks on a shared substrate network, which is known as survivable virtual network embedding (SVNE). However, existing SVNE algorithms, mostly designed for wired networks, are not necessarily optimal for the virtualization of ATNs due to the complex wireless interference. To this end, a fault-tolerant SVNE algorithm, termed SVNE-FT, is proposed to recover virtual networks from single node failure (end or switching node failure) under the wireless interference. To end node failure, SVNE-FT firstly adopts a novel node ranking approach to select reliable substrate nodes for virtual nodes and then remaps the failed virtual nodes, affected by node failure, by releasing part of the substrate paths to improve the resource utilization. In addition, to switching node failure, it adopts the improved pre-configured cycle (p-Cycle) technology to augment the reliable link mapping with differentiated p-Cycles that protect switching node from node failure and reduce the resource consumption of backups. Numerical simulation results reveal that SVNE-FT outperforms typical and latest heuristic SVNE algorithms under the complex interference of ATNs. For instance, average acceptance ratio of virtual networks improves at least 12%.

ТЕХНОЛОГИИ РАЗВИТИЯ МОРСКИХ ИНТЕГРИРОВАННЫХ СИСТЕМ СВЯЗИ

The goal is to improve the quality of information interaction of objects by increasing the reliability of message delivery to recipients and bandwidth through the integration of networks using various signals and physical channels. A search for new technical solutions for the creation of integrated (hybrid) communication technologies aimed at expanding the possibilities for creating adaptive, self organizing, resistant to destabilizing factors communication systems with an increased quality of services provided in vast areas was carried out. The method of solving the tasks is based on the analysis of development trends and forecasting the requirements for integrated mobile communication systems. The novelty lies in the development and evaluation of options for building the structures of integrated communication systems, represented by diverse, complementary subsystems using various methods of channel separation, including in physical environments, as well as algorithms for their operation. Key findings. A set of technologies for the development of coastal integrated communication systems has been developed: the structure of the system based on a hybrid mesh topology; the basic form of the carrier signal with controlled parameters depending on the physical channel; the principle of control of orthogonal signals in adjacent channels of switching and relay nodes, as well as between network nodes; hydroacoustic communication method. Hydroacoustic communication for coastal areas is a potential for increasing the number of simultaneously used information channels per unit of the volume of interaction of vital objects and makes it possible to connect satellite, air, surface, underwater and bottom subsystems of telecommunications. The con ducted studies have shown the stability of the proposed methods in conditions of excess of interference over the signal.

Multiclass data plane recovery using different recovery schemes in SDN: a simulation analysis

To provide dependable services SDN networks need to be resilient to link or switching node failures. This entails, when faults occur, ensuring differentiated types of recovery, according to carried traffic, to routing paths. However, the choice of the recovery scheme best suited to each traffic class is not direct, nor is obvious the impact of the combination of various recovery schemes, according to traffic classes. We explore the usage of different recovery schemes for traffic with distinct requirements Simulation analysis confirms that using different recovery schemes for distinct types of traffic does create differentiated effects in terms of traffic carried and bandwidth usage.

Tutorial on filterless optical networks [Invited

The recent acceleration in fiber-to-the-home deployment worldwide along with the emerging 5G communications are pressuring network operators to enhance their networks to serve these new deployments. Hence, operators are seeking new high-capacity optical-network architectures, while averting excessive capital and operational expenditures. Filterless optical networks (FONs), by replacing costly wavelength selective switches in switching nodes with passive optical power splitters/combiners, currently represent a prominent candidate for cost-effective optical-network deployment. In this tutorial, we provide an overview of the architecture and the design issues of FONs when deployed in core and in metro networks. We also perform a techno-economic study to quantify the economic benefits of FONs, comparing their cost to that of state-of-the-art filtered optical networks, and we discuss how several networking problems such as resource allocation, network slicing, and protection are tackled in the context of FONs. Finally, we present our vision of how research on FONs will evolve in the coming years.

Method for assessing the operating quality of a switching node in a technological transmission network data in the context of DDoS attacks by an intruder

The purpose of this study is to develop a mechanism to account for the effects of a distributed denial of service attack on a switching node, as well as to assess the quality of its functioning under destructive effects. Relevance stems from the possibility of disruption of regional economic complex management due to the impact on the elements of the technological network of data transmission attacker type “distributed denial of service”. Based on the mathematical apparatus of GERT-networks the authors propose an approach to assess the quality of switching nodes. The essence lies in the representation of the data flow service node switching network data transmission under attack by an intruder in the form of a stochastic network, setting the type of partial distributions, the definition of the equivalent function, followed by determining the distribution function delay time packets. The model proposed by the authors allows to evaluate the quality of switching nodes operation under the conditions of “distributed denial of service” intruder attacks, both when transmitting stationary Poisson and self-similar traffic, represented by the Weibull and Pareto flow models. The results obtained are in good agreement with the data given in previously published works. The model allows to analyze and develop directions to improve the quality of functioning of switching nodes of technological network of data transmission under conditions of destructive information impact of the intruder.

A Communication Method of Distributed Tactical Training Simulation System Suitable for Remote Interconnection

The traditional distributed tactical training simulation system is limited by the availability and bandwidth of military network transmission channel and does not have the feasibility of remote interconnection and spatial sub-regional deployment. In this paper, a new communication method of distributed tactical training simulation system is proposed to solve the problem of strong business coupling between nodes and system availability under the condition of low bandwidth. The operator of federated exchange, federated queue and their concepts and design requirements are firstly proposed, and the inverted tree, triangle, ring exchange topology and circular queue structure are further constructed. Theoretically, the expected goal of high-speed interworking between nodes in the cluster and high reliable transmission between clusters is realized. The example also shows that this method can significantly improve the throughput of single switching node and federated node after using reliability confirmation mechanism.

EMI Filter Design for a Three-Phase Buck–Boost Y-Inverter VSD With Unshielded Motor Cables Considering IEC 61800-3 Conducted and Radiated Emission Limits

The standard converter concept employed in variable speed motor drives is the two-level three-phase Si insulated-gate bipolar transistor voltage source inverter with its switch nodes connected to the motor terminals via shielded cables to avoid excessive high-frequency noise emissions. However, high dv/dt pulses of the inverter pose substantial stresses on the motor, which are further intensified by the ever-faster switching speeds of wide band-gap semiconductors, hence promoting interest in inverters with full-sinewave output filters, which potentially enable the use of inexpensive unshielded motor cables. However, the IEC 61800-3 standard dictates stringent conducted and radiated emission limits on unscreened power interfaces. In this article, a dc input and ac output filter structure allowing operation with unshielded cables is derived for a phase-modular 11-kW buck-boost Y-inverter motor drive system employing 1.2-kV SiC MOSFETs with a switching frequency of 100 kHz. First, regulations and measurement techniques for conducted and radiated emissions of motor drives are analyzed. Next, the operating principle of the Y-inverter is described and an electromagnetic interference equivalent circuit is derived, followed by a systematic filter design. Finally, measurements are conducted on an ultracompact hardware prototype of the converter system with 12 kW/dm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (197 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) power density, where the results indicate full compliance with the IEC 61800-3 conducted and radiated emission limits for operation with unshielded dc supply and motor cables in a residential area.

Method distribution of package delivery time

When analyzing the problems of organizing the effective functioning of distributed data transmission networks with packet switching, it becomes clear that it is necessary to improve existing models of individual network structures, develop new models for studying effects, factors and mechanisms that have not been considered previously, and create, on their basis, non-laborious methods for selecting network parameters according to various criteria of optimality. An analytical review of the results achieved in the study of various structural formations made it possible to reveal the degree of elaboration of the issues of organizing the effective operation of the network, to formulate unsolved problems and to outline the main directions of research. In this case, the peculiarity of end-to-end data transportation over a multi-link virtual connection is clearly not taken into account, and the question of the adequacy of the assigned distributions to the real information transfer process is not considered and remains open. An approach to the construction of the distribution of the transmission time of an information packet in a virtual channel with distortions is proposed, on the basis of which the analysis of the influence of the duration of the end-to-end time-out of non-receipt of a receipt on the operational characteristics of the data transport process is carried out. A model of a data transmission path with distortions in individual sections of the transfer in the form of a stochastic conveyor is proposed, and auxiliary relations necessary for the analysis of stochastic information transfer are obtained. The parameters of the line protocols largely determine the potential of inter-node connections, the requirements for the buffer memory of the switching nodes and the end-to-end delay of subscriber messages. The known methods for the formal selection of these parameters are focused mainly on the unconditional preference of the criterion for the throughput of inter-node connections and require time-consuming numerical calculations. Since the problem of redefining network parameters often arises in real networks due to changes in operating conditions, then there is a need to develop non-laborious engineering methods for their selection according to various criteria of optimality.

A Novel Methodology for Optimal SVC Location Considering N-1 Contingencies and Reactive Power Flows Reconfiguration

In this research, an alternative methodology is proposed for the location of Static VAR Compensators (SVC) in power systems, considering the reconfiguration of reactive power flows through the optimal switching of the transmission stage, which resembles the contingency restriction N-1 usually considered in transmission expansion planning. Based on this methodology, the contingency index was determined, which made it possible to determine which is the contingency that generates the greatest voltage degradation in the system. For the quantification of reactive flows, optimal AC power flows were used, which minimize the operating costs of the power system subject to transmission line switching restrictions, line charge-ability, voltages and node angles. To determine the node in which the compensation should be placed, the contingency index criterion was used, verifying the voltage profile in the nodes. The proposed methodology was tested in the IEEE test systems of 9, 14 nodes and large-scale systems of 200, 500 and 2000 bus-bars; to verify that the proposed methodology is adequate, the stability of the EPS was verified. Finally, the model allows satisfactorily to determine the node in which the SVC is implemented and its compensation value.

A Two-Channel High-Performance DC-DC Converter for Mobile AMOLED Display Based on the PWM–SPWM Dual-Mode Switching Method

In this paper, we propose a design of a two-channel high-performance DC-DC converter that provides a positive voltage VPOS with a low ripple, and a negative voltage VNEG with high power efficiency, for the purpose of enhancing power efficiency and output ripple under light loads of 100 mA or less for mobile active-matrix organic light-emitting diode (AMOLED) displays. The VPOS was designed as a boost converter using a novel input voltage variation reduction circuit (IVVRC), which rapidly changes the pulse width for input voltage fluctuations, using a feed-forward path. The VNEG was designed as an inverting buck–boost converter based on the pulse width modulation–set time variable pulse width modulation (PWM–SPWM) dual-mode switching method to enhance power efficiency, especially under light loads, and to reduce the overhead of the circuit configuration using a voltage-controlled oscillator. In addition, an adaptive dead-time using voltage detection of switching node (ADTVS) circuit was proposed to enhance power efficiency, which detects the voltage of the switching node at every cycle, and keeps the dead-time constant irrespective of changes in driving conditions. The proposed converter was fabricated with a chip size of 1.67 mm × 2.44 mm, using a 0.35 μm BCD process. Measurement results showed that the power efficiency of our converter was 72.9%~90.4% at 5 mA–100 mA light load output current, which is 2.7%~5.8% higher than the output of the previous converter. Furthermore, the output voltage ripple of VPOS and VNEG at 5 mA light load output current was 3.0 mV and 5.3 mV, respectively, which improved by 19% and 25% as compared to those of the previous converter, respectively.

A novel design of switched boost action based multiport converter using dsPIC controller for renewable energy applications

ABSTRACT Traditionally the grid supplies only a particular voltage to the load, but today we are using ‘n’ number of loads with different voltage rating and converters. So, the conversion of the generated AC voltage into several stages of DC voltage before reaching the load is required. In this paper, the Multi Port Converter (MPC) is proposed, which is capable of converting a single valued AC voltage into several stages of DC voltage. The feasibility of employing of converter level switch node, as an interface to numerous output stages is examined in this paper. The connecting of several outputs at the identical node is accomplished by the use of time-division multiplexing technique. In this study, the input power is multiplexed into separate ports via a phenomenon known as Switching Boost Action (SBA). The prototype was developed for converting the 240 V, 50 Hz, single phase AC supply into two outputs and the 12 V DC supply which can fed to the loads, that can be stored in batteries for future use. This paper has been proposed to design SBA based MPC using dsPIC controller for renewable energy applications.

Multi-timescale and multi-centrality layered node selection for efficient traffic monitoring in SDNs

With the assistance of global view in software-defined networks (SDNs), some switch nodes can be selected for traffic monitoring, which ensures the security of SDNs with a minimum cost. However, identifying the flow-based smallest subset of switches with the maximum coverage for node selection is always an NP-hard problem. To address this challenge, a two-stage parameter-rectifying-based selection (TSPRS) scheme is presented for efficient traffic monitoring in SDNs. In this novel scheme, a multi-timescale and multi-centrality layered virtual network (MMLVN) model is first built according to the different network structures over various time periods. By virtue of the MMLVN model, a tensor-based eigenvector multi-centrality computing (TEMC) method is employed at the first-stage selection to identify the smallest subset of switches with the maximum coverage for obtaining the subset of primary core nodes. To obtain more accurate parameters of real-time flows, a modified MMLVN model is further built by combining the results of a bandwidth cost-effective polling (BCeP) algorithm and the first-stage selection. Then, based on the modified MMLVN model, the TEMC method is reused to obtain the final optimization subset of the core nodes for efficient traffic monitoring at the second-stage selection. Extensive simulation experiments demonstrate that the proposed scheme can achieve a desirable tradeoff between the monitoring overhead and accuracy, and also reduce the communication bandwidth cost, which is superior to the existing state-of-the-art schemes.

Direct 12V/24V-to-1V Tri-State Double Step-Down Power Converter With Online V CF Rebalancing and In-Situ Precharge Rate Regulation

In response to fast-growing high-voltage (HV) power IC market demands, this article presents a tri-state double step-down (DSD) power converter to achieve direct 12V/24V- to-1V dc-dc power delivery with high efficiency and high power density. By taking advantage of the benefits from both three-level and DSD converter topologies, the converter allows the use of lower voltage rating power devices and thus facilitates high switching frequency operation with smaller power passives. An online flying capacitor voltage ( V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CF</sub> ) rebalancing scheme is introduced to optimize switching nodes voltages and minimize power path mismatch for improved reliability and efficiency. During startup transients, an in-situ precharge rate regulation technique manages the charging process on flying capacitors precisely in avoidance of potential device breakdown. An IC prototype of this design was fabricated using a 180 nm HV bipolar-CMOS-DMOS (BCD) process with an active area die of 6.3 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . At 3-W output power, a chip power density of 476 mW/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is accomplished. The online V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CF</sub> rebalancing reduces voltage mismatch between the flying capacitors by 16.7%. The converter achieves peak efficiencies of 88.3% and 92.1% for 24V/1V and 12V/1V conversion, respectively.

All optical metropolitan quantum key distribution network with post-quantum cryptography authentication.

Quantum key distribution (QKD) provides information theoretically secure key exchange requiring authentication of the classic data processing channel via pre-sharing of symmetric private keys to kick-start the process. In previous studies, the lattice-based post-quantum digital signature algorithm Aigis-Sig, combined with public-key infrastructure (PKI), was used to achieve high-efficiency quantum security authentication of QKD, and we have demonstrated its advantages in simplifying the MAN network structure and new user entry. This experiment further integrates the PQC algorithm into the commercial QKD system, the Jinan field metropolitan QKD network comprised of 14 user nodes and 5 optical switching nodes, and verifies the feasibility, effectiveness and stability of the post-quantum cryptography (PQC) algorithm and advantages of replacing trusted relays with optical switching brought by PQC authentication large-scale metropolitan area QKD network. QKD with PQC authentication has potential in quantum-secure communications, specifically in metropolitan QKD networks.

Modelling and Optimization of Multi-Service Optical Switching Networks with Threshold Management Mechanisms

DWDM networks make use of optical switching networks that allow light waves of multiple lengths to be serviced and provide the possibility of converting them appropriately. Research work on optical switching networks focuses on two main areas of interest: new non-blocking structures for optical switching networks and finding traffic characteristics of switching networks of the structures that are already well known. In practical design of switching nodes in optical networks, in many cases, the Clos switching networks are successfully used. Clos switching networks are also used in Elastic Optical Networks that can effectively manage allocation of resources to individual multi-service traffic streams. The research outcomes presented in this article deal with the problems of finding traffic characteristics in blocking optical switching networks with known structures. This article aims at presenting an analysis of the influence of traffic management threshold mechanisms on the traffic characteristics of multi-service blocking Clos switching networks that are used in the nodes of elastic optical networks as well as their influence on the traffic efficiency of network nodes. The analysis was carried out on the basis of research studies performed in a specially dedicated purpose-made simulation environment. The article presents a description of the simulation environment used in the experiments. The study was focused on the influence of the threshold mechanism, which is one of the most commonly used and elastic traffic management mechanisms, and on the traffic characteristics of switching networks that service different mixtures of multi-service Erlang, Engset and Pascal traffic streams. The conducted study validates the operational effectiveness and practicality of the application of the threshold mechanism to model traffic characteristics of nodes in an elastic optical network.

Advances in Fault Diagnostics and Post‐Fault Operation of Electrical Drives

Advances in Fault Diagnostics and Post‐Fault Operation of Electrical Drives