Modeling based real frequency technique

Usually commercially available software tools are used, to design matching networks for wireless communication systems. But a properly selected matching network topology with good initial element values must be supplied to these tools. Therefore, in this paper a modeling-based real frequency technique (M-RFT) is presented, to generate matching networks with initial element values. In the proposed method, output impedance data of the matching network are obtained in terms of ABCD-parameters of the load model. Then, they are modeled which in turn yields the desired matching network with initial element values. It is not needed to select a circuit topology for the matching network, which is the natural consequence of the matching processes. Also, there is no need to select the desired transducer power gain level; the proposed technique naturally provides a gain curve fluctuating around a flat level. Eventually, the initial design is improved by optimizing the performance of the matched system employing the commercially available computer aided design (CAD) packages. An algorithm and example are given, to illustrate the utilization of the proposed technique.     

A FLEXIBLE POLYMER FIBRE INFRASTRUCTURE FOR AN EVOLUTIONARY CUSTOMER PREMISES NETWORK

The developments in compressed digital video technology are paving the way for video-based services. Provision of such services requires a broadband communications network, which should extend into the customers' premises up to the terminals. This indicates a growing need for a customer premises network. This paper presents an infrastructure for an evolutionary and future-proof customer premises network. Such an infrastructure allows for early deployment and gradual upgrades associated with service demand. A key element in the concept is the use of the graded index polymer optical fibre (GIPOF) which combines an intrinsically high bandwidth with easy and therefore low-cost handling. There are two opposite approaches for the choice of network topology. In one approach, all applications are forced onto a single topology. In the other approach, the topology best suited for each application type is used. This paper considers the ‘best-suited topology’ approach and presents a network infrastructure that can support many topologies simultaneously as independent overlay networks. The proposed infrastructure consists of bundles of fibres, which can be interconnected and accessed by terminals in any required manner. © 1997 by John Wiley & Sons, Ltd.     

Design of broadband single matching networks

In general commercially available software tools are preferred, to design broadband matching networks for wireless communication systems. But they need a properly selected matching network topology with good initial element values. Therefore, in this paper a new real frequency technique is presented, to generate broadband single matching networks with suitable initial element values. In the proposed method, load impedance is written in terms of ABCD-parameters of the desired matching network and the source resistor. Then, free parameters are optimized which in turn yields the desired matching network with initial element values. It is not needed to select a circuit topology for the matching network, which is the natural consequence of the matching processes. Also, there is no need to select the desired transducer power gain level; the proposed technique naturally provides a gain curve fluctuating around the final available level. Eventually, the initial design is improved by optimizing the performance of the matched system employing the commercially available computer-aided design (CAD) packages. An algorithm and two examples are given, to illustrate the utilization of the proposed technique.     

A tutorial on using genetic algorithms for the design of network topology

The design of network topology is an important part of network design, since network topology is directly associated with network operational behavior, capacity, reliability, and cost. This paper is a tutorial paper concerned with illustrating how the optimization capabilities of genetic algorithms can be used to design suitable network topologies considering basic topology problems. Simple genetic algorithms have been developed for the topology problem of mesh networks, considering single node and single link failure tolerance. The algorithms are based on criteria of two important measures: minimizing the length of communication links; and minimizing traffic flow through these links for given traffic loads. The first measure contributes to minimizing the cost of cabling, while the second measure contributes to minimizing the cost of link capacity. The work provides a useful approach and tools to network students and professionals concerned with the topology design of backbone networks. The developed software is made available on the Internet. Copyright © 2006 John Wiley & Sons, Ltd.     

A design method for lumped broadband MMIC matching networks withsemiuniform frequency-dependent losses

A design method for broadband MMIC matching networks which consist of lumped inductors and capacitors is presented. Based on a fictitious transformation between the lossy network and the lossless one, the transducer power gain (TPG) of the lossy network is calculated using impedance matrix and transmission parameter matrix methods. Then, on the basis of the result of TPG optimization, the matching network can be synthesized. Since only the complexity of the matching network needs to be specified, the advantage of the real frequency technique of B.S. Yarman and H.J. Carlin (1982) is retained. In this design procedure the frequency-dependent losses of lumped elements can be considered. Thus the actual gain response tends to coincide with the desired performance more than when the element losses are neglected. An example is given to show the application of the method to broadband GaAs FET amplifier design     

Reliability and cost evaluation of third-generation wireless accessnetwork topologies: a case study

The "explosive growth in bursty traffic" changes the network dynamics and requires a good evaluation of various classes of service when designing an access network. From a topological standpoint, the multiservice networks in this paper are heterogeneous systems which integrate both a core and some wireless access networks into an infrastructure similar to third-generation wireless networks. Such networks require reliable and cost-effective solutions to the problem of selecting access technologies for satisfying performance and quality of service requirements related to the services and applications envisioned. This paper analyzes the reliability aspects of some access network topologies to insure a certain level of quality of service at the lowest cost for the end users. It considers a mass market equivalent to 1.6 million subscribers, the objective being to determine the cost the users are ready to pay to benefit from services and applications provided by these multiservice networks. For these purposes, the relative behavior of 3 access-network topologies are studied: the tree with parallel backup links, the ring, and the partially meshed topologies. In ring topology, simulation results show that a great connectivity in the access network is not justified in terms of reliability requirements; the partially meshed topology, even if it has redundant links which affect its cost, outperforms the tree with parallel backup links; and the ring topology is more reliable in terms of disconnected sessions than the tree topology. By considering both reliability and cost, a tree with parallel backup links appears the best topology for the access network and its cost is acceptable for the end user. This study can be extended by: (1) establishing the cost as a function of the quality of service; (2) optimizing the partially meshed topology for more reliable networks; and (3) defining a (shaping) policy to deal with a variety of traffic schemes     

A Lumped Circuit for Wideband Impedance Matching of a Non-Resonant, Short Dipole or Monopole Antenna

A new technique is proposed for wideband impedance matching of short dipole- or monopole-like antennas in the VHF-UHF bands. Instead of constructing the network topology for every particular antenna, we propose a simple network of one fixed topology. This network is an inductive L-section cascaded with a high-pass T-section. The network includes five discrete components—three inductors and two capacitors. Although the approach is not general, the paper proves that matching with the present network is close to the theoretical limit impedance matching confirmed by Bode-Fano theory. The matching performance also approaches the performance of the Carlin's equalizer for short dipoles and monopoles. The dipoles and monopoles may have different shape and different matching bandwidths. By using the matching circuit of fixed topology we avoid greater difficulties related to the practical realization of the Carlin's equalizer. The key point is to minimize the antenna's matching network complexity (and loss) so that the circuit can be designed and constructed in a straightforward manner.      

面向动态拓扑网络的深度强化学习路由技术

针对现有智能路由技术无法适用于动态拓扑的不足,提出了一种面向动态拓扑的深度强化学习智能路由技术,通过使用图神经网络近似PPO(Proximal Policy Optimization)强化学习算法中的策略函数与值函数、策略函数输出所有链路的权值、基于链路权值计算最小成本路径的方法,实现了路由智能体对不同网络拓扑的泛化....     

Capacity dimensioning and routing for hybrid satellite and terrestrial systems

Satellite network architecture plays an important role in the success of a satellite business. For future commercial broadband data satellite networks integrated with the terrestrial network, satellite network topology, link capacity, and routing have major impacts on the cost of the network and the amount of revenue the network can generate. To find the most cost-effective satellite network topology, we propose a unified mathematical framework using a two-stage stochastic programming formulation. The solution to the stochastic programming formulation gives optimal link capacities and an optimal routing strategy for different network topologies, taking into account uncertainties in long-term aggregate traffic statistic estimation. Using a simple satellite network example, we show the feasible topology regions for three different satellite topologies and show that, for some parameter values, the hybrid topology is more cost effective than nonhybrid topologies. In the limit of high traffic rejection cost, stochastic dimensioning reduces to static dimensioning. We study worst case static dimensioning for a general geosynchronous earth orbit satellite network and show the feasible topology regions, as well as effective cost comparisons for different topologies. We conclude with a discussion on network cost and architectural flexibility relating to satellite network design.     

无线传感器网络拓扑的容错度与容侵度

研究传感器网络拓扑对节点失败的容忍能力,必须解决三个基本问题,容忍节点失败的定义是什么,如何评价拓扑的这种容忍能力,什么样的拓扑具有较高的容忍能力.当前有关无线网络容错拓扑的研究均将图的多连通性看成拓扑的容错性,以图形多连通度的大小来衡量拓扑容错性的高低.本文通过实例分析指出图的多连通性与容错性是不同的,并结合网络的可用性,给出拓扑对失败节点容忍的定义,在此基础上,根据随机故障和恶意入侵两类节点失败形成原因,给出了拓扑容错度和容侵度作为拓扑对节点失败容忍能力高低的评价标准,并利用这两个标准分析了传感器网络分层拓扑,得出其拓扑容错度随簇头节点比例提高递减、而容侵度随之递增的理论结果.     

一种高生存性的光接入网结构

提出了一种新的双环加星型环的高生存性光接入网拓扑结构,并和现行各种光接入网拓扑结构的生存性进行了定量比较.在多故障情况下,具有比现行各种光接入网结构更高的生存率.随着故障数目的增加,其网络生存率均值下降缓慢,当故障数为6时,依然可以保持99.997%的高生存率均值,大大好于现行光接入网结构,说明该接入网结构能更好地满足用户对下一代光接入网生存性的要求.     

Virtual network construction with K‐shortest path algorithm and optimization problems for robust physical networks

In network virtualization, it has been considered that virtual networks are constructed over a physical network where conventional data transmission services have been utilized. Here, virtual networks have to be constructed while keeping qualities of the conventional services. In this paper, we propose a new virtual network construction in order to construct many virtual networks while keeping the robustness of a physical network by using network resources effectively. The proposed method consists of three processes: K ‐shortest path algorithm and Prim's minimum spanning tree algorithm, path splitting, and path migration. In the proposed method, at first, multiple topologies are designed by using the K ‐shortest path algorithm and the Prim's MST algorithm according to the user's request. After the topology design is completed, an admission control with network robustness of the physical network is performed. Then, if one of the designed topologies can satisfy the construction conditions, a virtual network is constructed and provided with the user. Otherwise, the path splitting and path migration are performed. Here, the path splitting is utilized to design another topology of a virtual network and path migration is used to change the topologies of the virtual networks that have already been constructed. These processes are formulated as optimization problems and those are processed by solving the optimization problems. In numerical examples, we show that our proposed method can construct a higher number of virtual networks while keeping the robustness of a physical network by comparing with the conventional method where only the Kou–Markowsky–Berman algorithm is used. Copyright © 2015 John Wiley & Sons, Ltd.     

Design of electrically loaded wire antennas using geneticalgorithms

A novel antenna design procedure based on genetic algorithm (GA) driven optimization is proposed and applied to the synthesis of wire antennas loaded with lumped components. Loading circuit parameters, locations of the loads along the antenna, as well as matching network parameters, are optimized simultaneously. A computational scheme based on the Sherman-Morrison-Woodbury formula for the fast evaluation of the antenna performance for many distinct loading configurations is developed. The GA iteratively guides a population of randomly selected design candidates toward the optimal solution. The success of the proposed procedure is demonstrated through its application to the design of efficient ultra-broadband antennas and their corresponding matching networks     

Design of Translucent Optical Networks: Partitioning and Restoration

We discuss the problem of designing translucent optical networks composed of restorable, transparent subnetworks interconnected via transponders. We develop an integer linear programming (ILP) formulation for partitioning an optical network topology into subnetworks, where the subnetworks are determined subject to the constraints that each subnetwork satisfies size limitations, and it is two-connected. A greedy heuristic partitioning algorithm is proposed for planar network topologies. We use section restoration for translucent networks where failed connections are rerouted within the subnetwork which contains the failed link. The network design problem of determining working and restoration capacities with section restoration is formulated as an ILP problem. Numerical results show that fiber costs with section restoration are close to those with path restoration for mesh topologies used in this study. It is also shown that the number of transponders with the translucent network architecture is substantially reduced compared to opaque networks.     

A New Technique for Synthesis of Broad-Band Parametric Amplifiers

A new synthesis technique for providing precise design values for the realization of broad-band parametric amplifiers incorporating practical varactor diode models is presented. The method provides the designer considerable flexibility in choosing the topology of matching networks employed. An integral part of the synthesis scheme is the application of a least-squares optimization procedure which employs exact partial derivatives of the objective function. The partial derivatives are used in the optimization to compute the gain sensitivity of the amplifier with respect to all matching network and diode parameters. For the first time, sensitivity data is presented which quantitatively shows the effect of the device and matching network parameter variations on overall amplifier response. This permits the determination of critical parameters and provides a means for establishing tolerances for various circuit parameters. In comparison with conventional procedures, significantly improved broad-band designs are shown to result.     

Design of practical broadband matching networks with commensurate transmission lines

To design broadband matching networks for microwave communication systems, commercially available computer aided design (CAD) tools are always preferred. But these tools need proper matching network topology and element values. Therefore, in this paper, a practical method is proposed to generate distributed-element matching networks with good initial element values. Then, the gain performance of the designed matching network can be optimized employing these tools. The utilization of the proposed method is illustrated by means of the given example. It is shown that proposed method provides very good initials for CAD tools.     

光纤通道拓扑结构冗余方法研究

对于采用光纤通道(FC)互连的航空电子系统,在FC3种基本拓扑结构的基础上,分别给出了FC组合拓扑结构和由多个FC交换机组成的FC交换式网络的通信模型。针对航空电子系统的分布式网络模型,给出了基于任务的可靠性分析方法。根据航空电子系统容错功能和提高可靠性的需要,提出了FC的3种基本冗余结构:双环结构、双交换机结构和交换机仲裁环冗余结构,专门针对FC交换式网络提出了两种冗余结构:基本路径冗余和全网络冗余,专门针对FC组合拓扑结构提出了桥端口冗余结构;通过基于任务的可靠性分析,对各种容错拓扑结构进行了比较。对FC各种冗余拓扑结构的研究对于航空电子系统设计阶段的容错设计和冗余结构设计都将起到一定作用。     

一种基于进化的电路网络建模方法

针对电路设计繁冗、复杂及周期长等特点,提出了一种基于进化的电路网络建模方法,该方法把电路网络建模过程转变为电路元器件选择和元件值确定的搜索优化过程.利用遗传程序设计进化电路网络的结构,对元器件和元件值相互影响的复杂解空间进行全局寻优,实现电路网络的进化.     

基于FCM隶属度的支持向量机

传统SVM在训练大规模数据集时,训练速度慢,时间消耗代价大.针对此问题,提出利用FCM算法对训练样本集进行预处理,依据样本隶属度提取出所有可能的支持向量进行SVM训练.利用原始数据集对算法进行验证,此算法在保证SVM分类精度的同时,大大提高了训练速度,算法具有可行性.