Designing of multichannel optical communication systems topologies criteria optimization

This paper presents the issues necessary to solve in the designing process of multichannel optical communication systems topologies. The main design assumption is the acceptance of mul-tichanneling in communication system realization. In particular, the basics of designing physical and logical topologies are shown. Also cost aspects of physical and logical topologies realization are shown

Modular expansion and reconfiguration of shufflenets in multi-star implementations.

by Philip Pak-tung To.Thesis (M.Phil.)--Chinese University of Hong Kong, 1994.Includes bibliographical references (leaves 57-60).Chapter 1 --- Introduction --- p.1Chapter 2 --- Modular Expansion of ShuffleNet --- p.8Chapter 2.1 --- Multi-Star Implementation of ShuffleNet --- p.10Chapter 2.2 --- Modular Expansion of ShuffleNet --- p.21Chapter 2.2.1 --- Expansion Phase 1 --- p.21Chapter 2.2.2 --- Subsequent Expansion Phases --- p.24Chapter 2.3 --- Discussions --- p.26Chapter 3 --- Reconfigurability of ShuffleNet in Multi-Star Implementation --- p.33Chapter 3.1 --- Reconfigurability of ShuffleNet --- p.34Chapter 3.1.1 --- Definitions --- p.34Chapter 3.1.2 --- Rearrangable Conditions --- p.35Chapter 3.1.3 --- Formal Representation --- p.38Chapter 3.2 --- Maximizing Network Reconfigurability --- p.40Chapter 3.2.1 --- Rules to maximize Tsc and Rsc --- p.41Chapter 3.2.2 --- Rules to Maximize Z --- p.42Chapter 3.3 --- Channels Assignment Algorithms --- p.43Chapter 3.3.1 --- Channels Assignment Algorithm for w = p --- p.45Chapter 3.3.2 --- Channels Assignment Algorithm for w = p. k --- p.46Chapter 3.3.3 --- Channels Assignment Algorithm for w=Mpk --- p.49Chapter 3.4 --- Discussions --- p.51Chapter 4 --- Conclusions --- p.5

Efficient embedding of virtual hypercubes in irregular WDM optical networks

This thesis addresses one of the important issues in designing future WDM optical networks. Such networks are expected to employ an all-optical control plane for dissemination of network state information. It has recently been suggested that an efficient control plane will require non-blocking communication infrastructure and routing techniques. However, the irregular nature of most WDM networks does not lend itself to efficient non-blocking communications. It has been recently shown that hypercubes offer some very efficient non-blocking solutions for, all-to-all broadcast operations, which would be very attractive for control plane implementation. Such results can be utilized by embedding virtual structures in the physical network and doing the routing using properties of a virtual architecture. We will emphasize the hypercube due to its proven usefulness. In this thesis we propose three efficient heuristic methods for embedding a virtual hypercube in an irregular host network such that each node in the host network is either a hypercube node or a neighbor of a hypercube node. The latter will be called a “satellite” or “secondary” node. These schemes follow a step-by-step procedure for the embedding and for finding the physical path implementation of the virtual links while attempting to optimize certain metrics such as the number of wavelengths on each link and the average length of virtual link mappings. We have designed software that takes the adjacency list of an irregular topology as input and provides the adjacency list of a hypercube embedded in the original network. We executed this software on a number of irregular networks with different connectivities and compared the behavior of each of the three algorithms. The algorithms are compared with respect to their performance in trying to optimize several metrics. We also compare our algorithms to an already existing algorithm in the literature

Improving performance through topology management and wireless scheduling in military multi-hop radio networks

Thesis (S.M.)--Massachusetts Institute of Technology, Sloan School of Management, Operations Research Center, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 91-93).We investigate two distinct problems in military radio networking. In the first problem, we study a mobile airborne multi-hop wireless network. The mobility of the nodes leads to dynamic link capacities requiring changes to the topology by adding and removing links. Changes are intended to minimize maximum link load. Mixed integer linear programming is used to periodically find topological modifications resulting in optimal performance. To reduce computation and the rate of changes to the topology, we design and employ heuristic algorithms. We present several such algorithms of differing levels of complexity, and model performance using each. A comparison of the results of each method is given. In the second problem, we study a ground multi-hop wireless network. Scalability is an issue for such ground tactical radio networks, as increasing numbers of nodes and flows compete for the capacity of each link. The introduction of a relay node allows additional routes for traffic flows. Greater benefit is achieved by fixing the relay node at a higher elevation to allow it to broadcast to all other nodes simultaneously, thereby reducing the number of hops packets must travel. We use a combination of linear programming (LP) and novel bounds on the achievable network performance to investigate the benefits of such a relay node. We show that a relay node provides moderate improvement under an all-to-all unicast traffic model and more substantial improvement for broadcast traffic patterns.by Zachary S. Bunting.S.M

Genetic algorithm optimisation methods applied to the indoor optical wireless communications channel

This thesis details an investigation into the application of genetic algorithms to indoor optical wireless communication systems. The principle aims are to show how it is possible for a genetic algorithm to control the received power distribution within multiple dynamic environments, such that a single receiver design can be employed lowering system costs. This kind of approach is not typical within the research currently being undertaken, where normally, the emphasis on system performance has always been linked with improvements to the receiver design. Within this thesis, a custom built simulator has been developed with the ability to determine the channel characteristics at all locations with the system deployment environment, for multiple configurations including user movement and user alignment variability. Based on these results an investigation began into the structure of the genetic algorithm, testing 192 different ones in total. After evaluation of each one of the algorithms and their performance merits, 2 genetic algorithms remained and are proposed for use. These 2 algorithms were shown capable of reducing the receiver power deviation by up to 26%, and forming, whilst the user perturbs the channel, through movement and variable alignment, a consistent power distribution to within 12% of the optimised case. The final part of the work, extends the use of the genetic algorithm to not only try to optimise the received power deviation, but also the received signal to noise ratio deviation. It was shown that the genetic algorithm is capable of reducing the deviation by around 12% in an empty environment and maintain this optimised case to within 10% when the user perturbs the channel

Topology Control and Pointing in Free Space Optical Networks

Free space optical (FSO) communication provides functionalities that are different from fiber optic networks and omnidirectional RF wireless communications in that FSO is optical wireless (no infrastructure installation cost involving fibers) and is highly directional (no frequency interference). Moreover, its high-speed data transmission capability is an attractive solution to the first or last mile problem to bridge to current fiber optic network and is a preferable alternative to the low data rate directional point-to-point RF communications for inter-building wireless local area networks. FSO networking depends critically on pointing, acquisition and tracking techniques for rapidly and precisely establishing and maintaining optical wireless links between network nodes (physical reconfiguration), and uses topology reconfiguration algorithms for optimizing network performance in terms of network cost and congestion (logical reconfiguration). The physical and logical reconfiguration process is called Topology Control and can allow FSO networks to offer quality of service by quickly responding to various traffic demands of network users and by efficiently managing network connectivity. The overall objective of this thesis research is to develop a methodology for self-organized pointing along with the associated autonomous and precise pointing technique as well as heuristic optimization methods for Topology Control in bi-connected FSO ring networks, in which each network node has two FSO transceivers. This research provides a unique, autonomous, and precise pointing method using GPS and local angular sensors, which is applicable to both mobile and static nodes in FSO networking and directional point-to-point RF communications with precise tracking. Through medium (264 meter) and short (40 meter) range pointing experiments using an outdoor testbed on the University of Maryland campus in College Park, sub-milliradian pointing accuracy is presented. In addition, this research develops fast and accurate heuristic methods for autonomous logical reconfiguration of bi-connected ring network topologies as well as a formal optimality gap measure tested on an extensive set of problems. The heuristics are polynomial time algorithms for a congestion minimization problem at the network layer and for a multiobjective stochastic optimization of network cost and congestion at both the physical and network layers

Genetic algorithm optimisation methods applied to the indoor optical wireless communications channel

This thesis details an investigation into the application of genetic algorithms to indoor optical wireless communication systems. The principle aims are to show how it is possible for a genetic algorithm to control the received power distribution within multiple dynamic environments, such that a single receiver design can be employed lowering system costs. This kind of approach is not typical within the research currently being undertaken, where normally, the emphasis on system performance has always been linked with improvements to the receiver design. Within this thesis, a custom built simulator has been developed with the ability to determine the channel characteristics at all locations with the system deployment environment, for multiple configurations including user movement and user alignment variability. Based on these results an investigation began into the structure of the genetic algorithm, testing 192 different ones in total. After evaluation of each one of the algorithms and their performance merits, 2 genetic algorithms remained and are proposed for use. These 2 algorithms were shown capable of reducing the receiver power deviation by up to 26%, and forming, whilst the user perturbs the channel, through movement and variable alignment, a consistent power distribution to within 12% of the optimised case. The final part of the work, extends the use of the genetic algorithm to not only try to optimise the received power deviation, but also the received signal to noise ratio deviation. It was shown that the genetic algorithm is capable of reducing the deviation by around 12% in an empty environment and maintain this optimised case to within 10% when the user perturbs the channel.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Joint optimization of topology, switching, routing and wavelength assignment

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 279-285).To provide end users with economic access to high bandwidth, the architecture of the next generation metropolitan area networks (MANs) needs to be judiciously designed from the cost perspective. In addition to a low initial capital investment, the ultimate goal is to design networks that exhibit excellent scalability - a decreasing cost-per-node-per-unit-traffic as user number and transaction size increase. As an effort to achieve this goal, in this thesis we search for the scalable network architectures over the solution space that embodies the key aspects of optical networks: fiber connection topology, switching architecture selection and resource dimensioning, routing and wavelength assignment (RWA). Due to the inter-related nature of these design elements, we intended to solve the design problem jointly in the optimization process in order to achieve over-all good performance. To evaluate how the cost drives architectural tradeoffs, an analytical approach is taken in most parts of the thesis by first focusing on networks with symmetric and well defined structures (i.e., regular networks) and symmetric traffic patterns (i.e., all-to-all uniform traffic), which are fair representations that give us suggestions of trends, etc.(cont.) We starts with a examination of various measures of regular topologies. The average minimum hop distance plays a crucial role in evaluating the efficiency of network architecture. From the perspective of designing optical networks, the amount of switching resources used at nodes is proportional to the average minimum hop distance. Thus a smaller average minimum hop distance translates into a lower fraction of pass-through traffic and less switching resources required. Next, a first-order cost model is set up and an optimization problem is formulated for the purpose of characterizing the tradeoffs between fiber and switching resources. Via convex optimization techniques, the joint optimization problem is solved analytically for (static) uniform traffic and symmetric networks. Two classes of regular graphs - Generalized Moore Graphs and A-nearest Neighbors Graphs - are identified to yield lower and upper cost bounds, respectively. The investigation of the cost scalability further demonstrates the advantage of the Generalized Moore Graphs as benchmark topologies: with linear switching cost structure, the minimal normalized cost per unit traffic decreases with increasing network size for the Generalized Moore Graphs and their relatives.(cont.) In comparison, for less efficient fiber topologies (e.g., A-nearest Neighbors) and switching cost structures (e.g., quadratic cost), the minimal normalized cost per unit traffic plateaus or even increases with increasing network size. The study also reveals other attractive properties of Generalized Moore Graphs in conjunction with minimum hop routing - the aggregate network load is evenly distributed over each fiber. Thus, Generalized Moore Graphs also require the minimum number of wavelengths to support a given uniform traffic demand. Further more, the theoretical works on the Generalized Moore Graphs and their close relatives are extended to study more realistic design scenarios in two aspects. One aspect addresses the irregular topologies and (static) non-uniform traffic, for which the results of Generalized Moore networks are used to provide useful estimates of network cost, and are thus offering good references for cost-efficient optical networks. The other aspect deals with network design under random demands. Two optimization formulations that incorporate the traffic variability are presented.(cont.) The results show that as physical architecture, Generalized Moore Graphs are most robust (in cost) to the demand uncertainties. Analytical results also provided design guidelines on how optimum dimensioning, network connectivity, and network costs vary as functions of risk aversion, service level requirements, and probability distributions of demands.by Kyle Chi Guan.Ph.D