Design of IIR allpass networks for Hilbert transformers

A new method for designing an allpass network is proposed. The coefficients obtained by a Kalman filter are used for an allpass network for an IIR Hilbert transformer with a flat magnitude response.<>     

Physical topology design for all-optical networks

When designing an all-optical network, the designers face a choice of laying down more fibers or increasing the number of wavelengths. Although either choice could be used to support new connections, one increases the link cost and the other increases the node (wavelength equipments) cost. The tradeoffs between link and node cost are not well understood. Using the efficient physical topology design algorithm that we propose, we study this tradeoff. We use the asymptotic growth rate of the provisioned capacity as a metric to compare various design alternatives. A higher asymptotic growth rate translates directly into a higher deployment cost for large networks. Our study shows that taking fiber length into consideration can lead to lower capacity requirement. We also find that a sufficiently large fiber-to-node ratio is necessary in order to minimize the asymptotic growth in the provisioned capacity, increase capacity utilization and minimize the need for wavelength conversion. We study a real network and find that its fiber-to-node ratio is too low. As a result, large provisioned capacity is required and less than 55% of the capacity is usable. By increasing the ratio, we can reduce the provisioned capacity and achieve close to 80% utilization.     

Low-power current-reused RF front-end based on optimized transformers topology

This paper discusses the design, analysis and performance of a 2.4 GHz fully integrated low-power current-reused receiver front-end implemented in 0.18 μm CMOS technology. The front-end is composed of a single-to-differential low-noise amplifier (LNA), using high-Q differential transformers and inductors and a coupled switching mixer stage. The mixer transconductor and LNA share the same DC current. Measurements of performance show a conversion gain of 28.5 dB, noise figure of 6.6 dB, 1 dB compression point of −32.8 dBm and IIP3 of −23.3 dBm at a 250 kHz intermediate frequency, while dissipating 1.45 mA from a 1.2 V supply.     

一种面向分布式星群的混合拓扑

针对分布式星群内无线网络的高可靠、灵活交换和低实现复杂度的需求,提出一种面向分布式星群的混合拓扑结构。通过在星群内各颗卫星配置模拟交换载荷实现模拟域的无中心拓扑,在交换卫星配置数字交换载荷实现数字域的双中心拓扑。理论及数值分析表明,混合拓扑结构具备与无中心拓扑结构相同的拓扑可靠性及较低的实现复杂度,同时能够提供波束/波长级、子带级和分组交换颗粒度。     

移动P2P网络安全拓扑构造协议

针对移动对等(MP2P)网络的安全问题,提出一种MP2P网络安全拓扑构造协议(AMPSTP).AMPSTP协议首先利用Fortune算法完成对地理区域的划分,然后给出临时锚节点的选取和更新策略、MP2P覆盖网拓扑模型的构造和维护机制、MP2P覆盖网的路由发现算法以及基于博弈的MP2P覆盖网的节点选择机制.最后对AMPSTP协议的性能进行理论分析和仿真实验.结果表明,与MADPastry协议相比AMPSTP协议不仅可以保障网络安全和提高网络性能,而且还大大降低了控制开销.     

A hybrid relay control mechanism for ribbon topology in low‐voltage power line communication networks

The communication reliability and distance of the low‐voltage power line communication system are seriously affected by the channel interference and the time variant load impedance. Therefore, how to control the relay nodes to reduce the communication delay and improve the communication reliability is mainly considered in the design. A novel hybrid relay control mechanism (HRCM) that includes the static relay pre‐configuration and the dynamic relay selection is designed for the ribbon topology in the low‐voltage power line communication networks. In the ribbon topology, the initial configuration for the communication link is realized through the pre‐configure relay nodes, which guarantees that the concentrator can communicate with the furthest terminal node. During the normal operations, the dynamic relay node is selected according to the sequence number of the uplink or downlink data frame and the data discard strategy. With the relay node dynamical selected mechanism, the frame repeated transmission can be avoided and the communication delay is reduced. The actual test results show that the hybrid relay control mechanism can effectively extend the communication distance, improve the communication real‐time and the reliability of the low‐voltage power line communication. Copyright © 2014 John Wiley & Sons, Ltd.     

Logical topology design for linear and ring optical networks

The design of logical topologies in wavelength-routing multihop optical networks is a well-studied problem. We consider logical topology (LT) design over the popular ring and linear topologies. Our objective is the minimization of the electronic processing delay for the worst case traffic flow. For uniform traffic between nodes, this delay minimization corresponds to minimizing the number of hops on a shortest path between the farthest two nodes in the logical topology (the diameter of the logical topology). The simple structure of the physical topologies enables us to present a rigorous analysis of the problem. We present lower bounds for the achievable diameter wherever possible and propose practical logical topology design algorithms and corresponding upper bounds. We also present an application of the LT designs in the linear topology to the survivability of ring networks     

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....     

A fast topology maintenance algorithm for high-bandwidth networks

A fast time-driven algorithm for topology maintenance in high-speed networks is presented. The algorithm uses only four time units for each broadcast by each computer. The best previous algorithm required O(log m) time units for each broadcast by each computer, where m is the number of currently operational computers in the network. In addition to its speed, the presented algorithm makes several significant contributions. I. Cidon et al. (1988) have shown that Ω(log m) time units are necessary for time-driven topology maintenance algorithms of high-speed networks that do not allow a packet to traverse the same edge in both directions. The proposed algorithm shows that this lower bound does not hold for networks that do allow a packet to traverse the same edge in both directions. The O(log m) algorithm assumed that it takes each computer at most one time unit to simultaneously broadcast messages to all neighbors of the computer. In contrast, a node in the proposed algorithm can send at most, one message per time unit. As in the O(log m) algorithm, the algorithm requires O (D) broadcasts per node before all nodes know the correct topology of the network, where D is the diameter of the currently operational portion of the network     

Localized topology control algorithms for heterogeneous wireless networks

Most existing topology control algorithms assume homogeneous wireless networks with uniform maximal transmission power, and cannot be directly applied to heterogeneous wireless networks where the maximal transmission power of each node may be different. We present two localized topology control algorithms for heterogeneous networks: Directed Relative Neighborhood Graph (DRNG) and Directed Local Spanning Subgraph (DLSS). In both algorithms, each node independently builds its neighbor set by adjusting the transmission power, and defines the network topology by using only local information. We prove that: 1) both DRNG and DLSS can preserve network connectivity; 2) the out-degree of any node in the resulting topology generated by DRNG or DLSS is bounded by a constant; and 3) DRNG and DLSS can preserve network bi-directionality. Simulation results indicate that DRNG and DLSS significantly outperform existing topology control algorithms for heterogeneous networks in several aspects.     

Distributed topology control of wireless networks

We propose and analyaze a distributed control law that will maintain prescribed local properties of a wireless ad hoc network in the presence of node mobility, MAC layer power control and link fades. The control law uses a simple and intuitive power adaptation mechanism. We consider as an example the topology requirement of maintaining the out-degrees of each node at prescribed values and keeping the in-degree close to the out-degree. The topology objective is achieved by adapting the transmission power based only on local information. This power adaptation algorithm is analyzed using the o.d.e. approach to stochastic approximation. Simulation results verify the analysis and demonstrate its effectiveness. We also study the ability of the proposed objective to maintain connectivity. Although many heuristics are described in the literature to maintain local topological properties, the algorithm proposed in this paper is the first one that has proven convergence properties. Vivek S. Borkar got his B. Tech. (Elec. Engg.) from Indian Institute of Technology, Mumbai, in 1976, M. S. (Systems and Control) from Case Western Reserve Uni. in 1977 and Ph.D. (Elec. Engg. and Comp. Sci.) from Uni. of California, Berkeley. He was with Uni. of Twente (1980–81), TIFR Centre, Bangalore (1982–89), Indian Inst. of Science (1989–99), and has been with School of Technology and Computer Science, Tata Inst. of Fundamental Research, Mumbai, since April 1999. His research interests include stochastic optimization and applications. D. Manjunath received his B.E. from Mysore University, M.S. from Indian Institute of Technology, Madras and Ph.D. from Rensselaer Polytechnic Inst, Troy NY in 1986, 1989 and 1993 respectively. He has been a summer intern in the Corporate R & D Center of GE (1990), a visiting faculty in the Computer and Information Sciences Dept. of the University of Delaware (1992-93), a post doctoral fellow in the Computer Science Dept. of the University of Toronto (1993–84) and on the Electrical Engineering faculty of the Indian Inst. of Technology, Kanpur (1994–98).He has been with the Elec Enggg. Dept. of Indian Inst. of Technology, Bombay in Mumbai since July 1998 where he is now an Associate Professor. His research interests are in the areas of communication networks, performance analysis of systems, queueing systems and multimedia communications.     

Evaluation and improvement of CDS-based topology control for wireless sensor networks

The connected dominating set (CDS) principle has emerged as the predominant method for energy-efficient discovery and clustering of power-/location-unaware WSN nodes. While many CDS discovery protocols have been proposed recently, a one-to-one comparative evaluation of these protocols has not been performed on judicious metrics. In this paper, we perform a simulation-based evaluation of three prominent CDS based protocols (CDS Rule K, EECDS and A3) on the basis of message and energy overhead, residual energy, number of unconnected nodes, and convergence time. Our analysis shows that the protocols’ performances vary significantly with different maintenance techniques and none of the existing protocols can outperform the others on all metrics. Based on this result, we identify some performance-improving guidelines for CDS-based topology discovery and utilize them to propose a new protocol, clique-based CDS discovery (CCDS). We show that CCDS provides considerably better performance than existing protocols in most operational scenarios.     

Analysis and modeling of interstacked transformers for mm-wave applications

The analysis and modeling of monolithic interstacked transformers for mm-wave applications is addressed. The performance advantages of the interstacked structure are demonstrated by using the most important figures of merit for integrated transformers and a physic-based scalable lumped model is proposed. The model components are calculated with closed-form expressions that make use of geometrical and technological parameters. The accuracy of the proposed model is demonstrated by comparison with electromagnetic data in a wide frequency range. Maximum errors are below 5, 7.5, and 2% for magnetic coupling factor, quality factor, and self-resonance frequency, respectively. High accuracy is also achieved in the modeling of S-parameters up to the self-resonance frequency.     

A WDM cross-connected star topology for multihop lightwave networks

The authors propose a star topology for multihop lightwave networks in which the conventional N×N passive star coupler is replaced by fixed wavelength division multiplexed (WDM) cross connects. The proposed topology overcomes three major limitations of the conventional star topology. First, it reduces the number of wavelengths needed in a (p,k) ShuffleNet from kp ^k+1 wavelengths in the conventional topology to p wavelengths in the proposed one. Second, the signal power loss due to the 1/N power splitting at the star coupler no longer exists in the WDM cross connects and, therefore, the restriction on the supported number of users by the star network is alleviated. Third, it completely eliminates the need for wavelength filtering at the input to the receivers as is the case in the conventional star topology     

Efficient algorithm for virtual topology design in multihoplightwave networks

One of the major challenges in the virtual topology design of a WDM star based system, is to incorporate in the optimization process both realistic objective functions and real system behavior. The authors present an efficient discrete optimization algorithm that meets these goals while incorporating the prevailing traffic conditions. They simulate the real system and then approximate the objective function by a short term simulation. The optimization process is based on an ordinal optimization approach, i.e., is insensitive to the approximation of the objective function obtained by short term simulation. Another crucial issue in virtual topology design is how to evaluate the quality of the solution obtained by the algorithm. They propose a new metric to evaluate the solution quality, the so called suboptimal quality, obtained by deriving the solution's relative position in the state space according to the performance order. The experiments presented in the paper attest to the quality (efficiency and robustness) of the optimization algorithm and its suitability to solve the wavelength assignment problem     

MST-based clustering topology control algorithm for wireless sensor networks

In this paper, we propose a novel clustering topology control algorithm named Minimum Spanning Tree (MST)-based Clustering Topology Control (MCTC) for Wireless Sensor Networks (WSNs), which uses a hybrid approach to adjust sensor nodes’ transmission power in two-tiered hierarchical WSNs. MCTC algorithm employs a one-hop Maximum Energy &; Minimum Distance (MEMD) clustering algorithm to decide clustering status. Each cluster exchanges information between its own Cluster Members (CMs) locally and then deliveries information to the Cluster Head (CH). Moreover, CHs exchange information between CH and CH and afterwards transmits aggregated information to the base station finally. The intra-cluster topology control scheme uses MST to decide CMs’ transmission radius, similarly, the inter-cluster topology control scheme applies MST to decide CHs’ transmission radius. Since the intra-cluster topology control is a full distributed approach and the inter-cluster topology control is a pure centralized approach performed by the base station, therefore, MCTC algorithm belongs to one kind of hybrid clustering topology control algorithms and can obtain scalability topology and strong connectivity guarantees simultaneously. As a result, the network topology will be reduced by MCTC algorithm so that network energy efficiency will be improved. The simulation results verify that MCTC outperforms traditional topology control schemes such as LMST, DRNG and MEMD at the aspects of average node’s degree, average node’s power radius and network lifetime, respectively.     

A self-organization structure for hybrid networks

This paper focuses on the self-organization of ad hoc and hybrid networks. We propose to organize networks with two integrated virtual structures: a backbone and clusters. The backbone helps to optimize the flooding of control packets, and to offer a natural prolongation of the backbone of wired networks. Clusters help to hierarchize the network, each of which is managed logically by its clusterhead. Since MANETs are mobile, we propose distributed algorithms for both the construction and the maintenance to preserve an efficient virtual structure despite topology changes. Simulations results exhibit the robustness and persistence of the proposed virtual structure.     

Using generalized capacitated trees for designing the topology of local access networks

The design of the topology of a local access network is a complex process which builds on many different combinatorial optimization problems such as the concentrator quantity problem, the concentrator location problem, the terminal clustering problem and the terminal layout problem. Usually, these four subproblems are solved separably and sequentially and the solution of one subproblem is used as data for the next subproblem. There are two main drawbacks associated to this four‐phase approach: i) without knowing the optimal solution to the global problem it is difficult to set the parameters for some of the subproblems which appear in the earlier phases and ii) in many cases, wrong decisions taken at one of the earlier phases are “passed” to the subsequent phases. Our aim in this paper is to formulate the two last subproblems, clustering and layout, as one single generalized capacitated tree problem. We formulate the clustering/layout problem as a capacitated single‐commodity network flow problem with adequate capacities on the arcs. We adapt a reformulation presented in (Gouveia, 1995) of a single‐commodity flow model presented in (Gavish, 1983). We present several inequalities which can be used to tighten the LP relaxation of the original formulation. We present two heuristics for obtaining feasible solutions for the clustering/layout problem. Computational results taken from tests with 50, 100 and 200 nodes indicate that in most of the cases the best heuristic produces topologies with lower cost than the ones obtained by solving separately and sequentially the two individual subproblems. This revised version was published online in June 2006 with corrections to the Cover Date.     

Analysis of rectangular spiral transformers for MMIC applications

Multidielectric planar structures such as transformers and triformers are analyzed by cascading multidimensional chain matrices. The distributed-line model facilitates the use of these elements in microwave monolithic integrated circuits (MMIC) applications as wideband transformers and baluns. High-speed routines suitable for inclusion in computer-aided design packages for desktop PCs are implemented and used to calculate S parameters. Wideband MMIC triformers are fabricated and measured, showing good agreement between theory and measurement over the frequency range 1-10 GHz