WDM-based local lightwave networks. II. Multihop systems

For pt.I see ibid., vol.6, no.3, p.12-27, 1992. A survey of wavelength-division-multiplexing (WDM)-based local lightwave networks is presented. The general characteristics of multihop systems are discussed, and various multihop approaches are reviewed. The construction of optimal structures based on minimizing the maximum link flow and optimizations based on minimization of the mean network packet delay are also reviewed. Regular topologies that have been studied as candidates for multihop lightwave networks, including the perfect shuffle, the de Bruijn graph, the toroid, and the hypercube, are discussed. Near-optimal node placement algorithms and shared-channel multihop systems are also discussed     

A simple adaptive routing scheme for congestion control inShuffleNet multihop lightwave networks

The authors describe a simple adaptive routing scheme for datagram (connectionless) and virtual circuit (connection-oriented) transmission that relieves congestion resulting from nonuniform traffic patterns and network failures. The authors describe a fixed-routing algorithm for dedicated channel ShuffleNets. Based on the fixed routing algorithm, an adaptive routing scheme for datagram transmission is presented followed by performance results for uniform and nonuniform traffic patterns and fault tolerance. The adaptive routing of datagrams uses only the local queue size information available at the network interface units (NIUs) and redistributes the load as congestion develops. Since datagrams are individually routed through the network, they may not arrive at their destination in the order they were generated and may need to be resequenced. The authors compute an upper estimate on the resequencing buffer size for stream traffic. A virtual circuit version of the adaptive routing algorithm eliminates the need for resequencing buffers     

High-capacity lightwave local are networks

The author presents an overview of fundamental considerations that guide and motivate research in this area. He explores the relationship between the bandwidth of the fiber, the available power and the loss in various network designs, and the throughput of networks as limited by the medium-access techniques and control mechanisms. He discusses two approaches to opening up the bottleneck that seem particularly promising. The first, multihop, uses a novel network architecture to achieve high capacity with existing devices; the second, wavelength division multiple access (WDMA), emphasizes new devices in a relatively conventional architecture. Noting that the primary disadvantage of the bus topology, poor energy efficiency, could be overcome with a suitable optical amplifier to compensate for the high signal attenuation in the network, the author discusses one of the most promising candidates, the traveling-wave semiconductor amplifier. He also discusses medium-access considerations     

Logically rearrangeable multihop lightwave networks

The optimization problem of rearrangeable multihop lightwave networks is considered. The authors formulate the flow and wavelength assignment problem, when minimizing the maximum flow in the network, as a mixed integer optimization problem subject to linear constraints. The problem is decomposed into two independent subproblems, the wavelength assignment (or connectivity problem) and the flow assignment (or routing problem). A simple heuristic provides a meaningful formulation to the connectivity problem, in a form similar to a transportation problem. An algorithm is then proposed which finds a heuristic initial logical connectivity diagram and the corresponding routing, and then iterates from that solution by applying branch-exchange operations to the connectivity diagram. The algorithm was tested on illustrative traffic matrices for an 8 node network with two transmitters and two receivers per node, and an improvement in achievable throughput over the Perfect Shuffle interconnection pattern was shown in all cases     

An overview of lightwave packet networks

The unique systems opportunities offered by, and the unique systems constraints imposed by, lightwave technology as it applies to the field of distributed packet networks are examined. Single-channel and star topology approaches are first considered. Terabit-capacity lightwave networks are discussed, covering both wavelength-division and time-division multiplexing. Multichannel multihop lightwave networks are then considered, and a particular implementation, the ShuffleNet, is described, and its performance, as well as some simple addressing and routing schemes, is discussed     

Multihop routing with static and distributed clustering in WSNs

Wireless Networks - Nowadays, Wireless Sensor Networks are one of the fundamental infrastructures for IoT technology. Although WSN has been researched for a decade, providing energy efficiency for...     

Optical components for WDM lightwave networks

Recently, there has been growing interest in developing optical fiber networks to support the increasing bandwidth demands of multimedia applications, such as video conferencing and World Wide Web browsing. One technique for accessing the huge bandwidth available in an optical fiber is wavelength-division multiplexing (WDM). Under WDM, the optical fiber bandwidth is divided into a number of nonoverlapping wavelength bands, each of which may be accessed at peak electronic rates by an end user. By utilizing WDM in optical networks, we can achieve link capacities on the order of 50 THz. The success of WDM networks depends heavily on the available optical device technology. This paper is intended as a tutorial on some of the optical device issues in WDM networks. It discusses the basic principles of optical transmission in fiber and reviews the current state of the art in optical device technology. It introduces some of the basic components in WDM networks, discusses various implementations of these components, and provides insights into their capabilities and limitations. Then, this paper demonstrates how various optical components can be incorporated into WDM optical networks for both local and wide-area applications. Finally, the paper provides a brief review of experimental WDM networks that have been implemented     

Wavelength assignment in multihop lightwave networks

In this paper we present a new approach to the design of multihop lightwave networks with connectivity patterns that can be dynamically reconfigured. We introduce a practical algorithm that efficiently reconfigures the connectivity diagram by reassigning wavelengths to best fit the current traffic pattern. A newly developed stochastic optimization algorithm is used to obtain the mapping of a regular structure into a WDM star, while optimizing the system performance measures. The optimization tool is generated and can be used with any objective function which is a function of the traffic patterns, the system control and the system configuration. The results show that this is a practical tool and the resulting structures have a superior system performance     

Multiwavelength lightwave networks for computer communication

The different approaches being considered to build high-capacity lightwave networks are described. Two kinds of lightwave network architectures are examined: broadcast-and-select networks and wavelength-routing networks. A comparison of the two shows that broadcast-and-select networks may be more suitable for local area networks (LANs) and metropolitan area networks (MANs), while wavelength-routing networks are suitable for wide area networks (WANs). The overall network may then be a combination of broadcast subnets interconnected by a point-to-point wavelength-routing network     

Subcarrier multiplexing for multiple-access lightwave networks

This paper describes the applicability of subcarrier multiplexing to lightwave multiple-access networks. It is shown how currently available microwave and lightwave components can be used, by using subcarrier multiplexing, to provide high-capacity networks. For example, the proposed multiple-access network can support 1024 users at a continuous bit rate of 1.5 Mbit/s, per user.     

Buffered fixed routing: a routing protocol for real-time transportin grid networks

We propose a new routing protocol called buffered fixed routing (BFR) for real-time applications on grid networks. While previous routing protocols for grid networks have been designed to improve network throughput, the BFR scheme is proposed to guarantee the end-to-end packet delay and sequencing without loss by using finite buffers at each node. Thus the proposed scheme can satisfy quality-of-service (QoS) requirements of real-time applications. The BFR scheme uses the token on the row ring to provide QoS guarantees. The performance of the BFR scheme is analyzed by using the Geom/Geom/1 queueing system under uniform traffic. In the simulation, the BFR scheme shows the zero-loss, high-throughput performance with the minimum delay variation compared to other routing protocols such as store and forward routing, deflection routing and vertical routing. In addition, it has shown the smallest average delay at intermediate and heavy loads     

路由与网桥结构之比较

有线电视经营者及其下属成员在建宽带线缆调制解调器网络时,遇到前所未有的网络扩展压力。人们预计1998年至1999年间网络用户和业务量会快速增长,这也是业内大多数有线经营者扩大市场的重要原因。@HomeNetwork、Me-diaOne/TimeWarnerRoadRunner等大公司在一年之内有可能要为成千上万个用户服务。     

Practical constraints in growth of lightwave networks

The amount of fiber required, propagation delay, and length of the longest link are significant design constraints in spatially large networks. This paper examines these characteristics from the viewpoint of growth and compares basic networks with hierarchical ones in terms of these characteristics. Results show that, when considering growth from three nodes, a star network randomly placed with a uniform distribution uses less fiber than a dual ring until there are 57 nodes. As the networks become large, the star has the smallest propagation delay and the dual ring uses the least amount of fiber. A two-level network having a star on the upper level and dual rings on the lower network level performs well in both categories by using 1.38 times as much fiber as the dual ring and having 1.65 times the propagation delay of a star as the number of nodes becomes large     

Branch-exchange sequences for reconfiguration of lightwave networks

Some of today's telecommunications networks have the ability to superimpose some form of logical connectivity, or virtual topology, on top of the underlying physical infrastructure. According to the degree of independence between the logical connectivity and the physical topology, the network can dynamically adapt its virtual topology to track changing traffic conditions, and cope with failure of network equipment. This is particularly true for lightwave networks, where a logical connection diagram is achieved by assignment of transmitting and receiving wavelengths to the network stations that tap into, and communicate over, an infrastructure of fiber glass. Use of tunable transmitters and/or receivers allow the logical connectivity to be optimized to prevailing traffic conditions. With rearrangeability having thus emerged as a powerful network attribute, this paper discusses the reconfiguration phase which is the transition between the current logical connection diagram and a target diagram. We consider here an approach where the network reaches some target connectivity graph through a sequence of intermediate connection diagrams, so that two successive diagrams differ by a single branch-exchange operation. This is an attempt at logically reconfiguring the network in a way that is minimally disruptive to the traffic. We propose and compare three polynomial-time algorithms that search for “short” sequences of branch-exchange operations, so as to minimize the overall reconfiguration time. For networks made of up to 40 stations, theoretical and simulation results show that, when a randomly selected diagram is to be changed to another randomly chosen diagram, the average number of branch-exchange operations required grows linearly with the size of the network     

QUARTS-II: a routing simulator for ATM networks

This article presents a discrete-event simulator, called QUARTS-II, that can be used for the design and analysis of routing protocols for ATM networks. This simulator shares many high-level features of the ATM Forum's P-NNI routing protocol; topology-state advertisement, on-demand source routing, call admission control and generic call admission control, hierarchical routing, and crank-back and rerouting. Simulations can be carried out at both the call and cell levels. Although this simulation tool has been designed primarily to simulate routing protocols, it can easily be extended to simulate other elements of an AIM traffic control architecture     

Optical signal processing for lightwave communications networks

A number of optical signal processing functions that might be potentially important for future lightwave communication networks are described. An optical network with a distribution capacity of 100 HDTV channels is considered along with how such a network can be implemented using the following functional subsystems: frequency converters; transmitter banks; modified (wavelength division multiplexing) WDM demultiplexers; and tunable optical receivers. Discussed are the key network-level issues: the power budget, the channel separation, and the overall rationale for selection of multiplexing techniques. A hardware implementation of the functional subsystems using three basic building blocks-tunable amplifiers/filters, phase locked loops, and comb generators-is discussed     

A new architecture and a new metric for lightwave networks

The notion of a logically routed network was developed to overcome the bottlenecks encountered during the design of a large purely optical network. In the last few years, researchers have proposed the use of torus. Perfect shuffle, hypercube, de Bruijn graph, Kautz graph, and Cayley graph as an overlay structure on top of a purely optical network. All these networks have regular structures. Although regular structures have many virtues, it is often difficult in a realistic setting to meet these stringent structural requirements. In this paper, we propose generalized multimesh (GM), a semiregular structure, as an alternate to the proposed architectures. In terms of simplicity of interconnection and routing, this architecture is comparable to the torus network. However, the new architecture exhibits significantly superior topological properties to the torus. For example, whereas a two-dimensional (2-D) torus with N nodes has a diameter of Θ(N^0.5), a generalized multimesh network with the same number of nodes and links has a diameter of Θ(N^0.25). In this paper, we also introduce a new metric, flow number, that can be used to evaluate topologies for optical networks. For optical networks, a topology with a smaller flow number is preferable, as it is an indicator of the number of wavelengths necessary for full connectivity. We show that the flow numbers of a 2-D torus, a multimesh, and a de Bruijn network, are Θ(N^1.5), Θ(N^1.25), and Θ(N log N), respectively, where N is the number of nodes in the network. The advantage of the generalized multimesh over the de Bruijn network lies in the bet that, unlike the de Bruijn network, this network can be constructed for any number of nodes and is incrementally expandable     

Topology of a store-and-forward net

Bounds are obtained for the minimum average delay of equal-length messages in a store-and-forward net when the traffic level is low. Specific network topologies are shown to achieve the bound when the traffic is also uniform.     

Multihop data gathering in wireless sensor networks with a mobile sink

Network performance can be improved by using a mobile sink (MS) to collect sensed data in a wireless sensor network. In this paper, we design an efficient trajectory for MS, collecting data from sensor nodes in a multihop fashion, with the aim of prolonging the network lifetime. Considering event‐driven applications, we present an approach to jointly determine the optimal trajectory for MS and data paths and transmission rates from source nodes to MS, without considering any rendezvous points. In these applications, an MS is supposed to harvest the data from source nodes in a given time‐slot. We first show that this problem is in form of a mixed integer nonlinear programming model, which is NP‐hard. Then, to achieve an approximate solution, we divide the mentioned problem into 2 simple subproblems. In fact, after determining an approximate zone for the trajectory of MS, the optimal data paths and transmission rates from source nodes to the MS are obtained through a mathematical optimization model. Finally, to illustrate the efficiency of the proposed approach, we compare the performance of our algorithm to an rendezvous point–based and also the state‐of‐the‐art approach in different scenarios.