It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

On the capacity of a cellular CDMA system

Praise for the Third Edition: "This is one of the best books available. Its excellent organizational structure allows quick reference to specific models and its clear presentation . . . solidifies the understanding of the concepts being presented."IIE Transactions on Operations EngineeringThoroughly revised and expanded to reflect the latest developments in the field, Fundamentals of Queueing Theory, Fourth Edition continues to present the basic statistical principles that are necessary to analyze the probabilistic nature of queues. Rather than presenting a narrow focus on the subject, this update illustrates the wide-reaching, fundamental concepts in queueing theory and its applications to diverse areas such as computer science, engineering, business, and operations research.This update takes a numerical approach to understanding and making probable estimations relating to queues, with a comprehensive outline of simple and more advanced queueing models. Newly featured topics of the Fourth Edition include:Retrial queuesApproximations for queueing networksNumerical inversion of transformsDetermining the appropriate number of servers to balance quality and cost of serviceEach chapter provides a self-contained presentation of key concepts and formulae, allowing readers to work with each section independently, while a summary table at the end of the book outlines the types of queues that have been discussed and their results. In addition, two new appendices have been added, discussing transforms and generating functions as well as the fundamentals of differential and difference equations. New examples are now included along with problems that incorporate QtsPlus software, which is freely available via the book's related Web site.With its accessible style and wealth of real-world examples, Fundamentals of Queueing Theory, Fourth Edition is an ideal book for courses on queueing theory at the upper-undergraduate and graduate levels. It is also a valuable resource for researchers and practitioners who analyze congestion in the fields of telecommunications, transportation, aviation, and management science.

Fundamentals of Queueing Theory

Technical foundations introduction software reliability and system reliability the operational profile software reliability modelling survey model evaluation and recalibration techniques practices and experiences best current practice of SRE software reliability measurement experience measurement-based analysis of software reliability software fault and failure classification techniques trend analysis in validation and maintenance software reliability and field data analysis software reliability process assessment emerging techniques software reliability prediction metrics software reliability and testing fault-tolerant SRE software reliability using fault trees software reliability process simulation neural networks and software reliability. Appendices: software reliability tools software failure data set repository.

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Handbook of software reliability engineering

To support bursty traffic on the Internet (and especially WWW) efficiently, optical burst switching (OBS) is proposed as a way to streamline both protocols and hardware in building the future gener...

Optical burst switching (OBS) - a new paradigm for an optical Internet

The emerging software defined networking (SDN) paradigm separates the data plane from the control plane and centralizes network control in an SDN controller. Applications interact with controllers to implement network services, such as network transport with quality of service. SDN facilitates the virtualization of network functions so that multiple virtual networks can operate over a given installed physical network infrastructure. Due to the specific characteristics of optical (photonic) communication components and the high optical transmission capacities, SDN-based optical networking poses particular challenges, but holds also great potential. In this article, we comprehensively survey studies that examine the SDN paradigm in optical networks; in brief, we survey the area of software defined optical networks (SDONs). We mainly organize the SDON studies into studies focused on the infrastructure layer, the control layer, and the application layer. Moreover, we cover SDON studies focused on network virtualization, as well as SDON studies focused on the orchestration of multilayer and multidomain networking. Based on the survey, we identify open challenges for SDONs and outline future directions.

Software Defined Optical Networks (SDONs): A Comprehensive Survey

This paper addresses contention resolution in optical switching fabrics exploiting Parametric Wavelength Converters (PWCs). Being a PWC able to perform simultaneous wavelength conversions, it can be employed to replace many single-channel wavelength converters, thus saving in the number of expensive optical components. Recently a switching fabric employing FixedWavelength Converters (FWCs), providing relevant cost savings compared to previous proposals, has been presented. The drawback is that it requires a high number of FWCs. For this reason, here new solutions based on PWCs instead of FWCs for such an architecture are proposed. Resulting switching fabrics are compared in terms of loss performance and cost. Simulation results outline that fabrics based on PWCs allow to save devices while obtaining the same performance as architectures using FWCs. They also prove how cost benefits are obtained in many switch configurations.

Contention resolution using Parametric Wavelength Converters: Performance and cost analysis

The delay-line buffer is widely used to solve contention by exploiting the time domain for optical packet switching (OPS) networks. How to optimize the length of the delay-line element to minimize the packet loss is a major challenge in designing delay-line buffers efficiently. In this paper we consider the buffers in asynchronous OPS networks with different incoming traffic patterns. For a specific mean packet length, we first demonstrate that the optimum length value of the delay-line element mainly depends on the incoming traffic load. The dependence of packet loss ratio on the delay-line granularity under different traffic loads and buffer sizes is given by both analytical model and simulation results. An optimum delay granularity is found under each traffic load, and this optimum granularity is independent of the buffer sizes. According to this finding, we designed an adaptive delay-line buffer structure with an input-feedback mechanism, namely an improved multiple-input single-output optical buffer, which could automatically configure the switch fabric and adjust the delay-line granularity according to the incoming traffic load. It is shown that the proposed buffer structure can achieve optimum performance for packet loss rate under different network scenarios.

Optimized design of delay-line buffers with an input-feedback mechanism for asynchronous optical packet switching networks.

This paper evaluates the performance of an asynchronous optical packet switch (OPS) equipped with limited range wavelength converters (LRWCs), in terms of packet loss ratio (PLR), when a circular-type wavelength conversion is adopted. Two separate Markov models are proposed to provide the analytical upper and lower bounds values of the PLR. The corresponding closed form expressions are given. We also build a discrete event simulator which introduces two realistic-to-implement conversion policies (closest conversion, random conversion) for the arriving packets. Results show that the proposed models give the absolute PLR bounds values for the studied OPS node. In addition, the paper gives clear guidelines for the applicability of the present models according to the normalized system load, the conversion range of the used LRWCs, and the employed conversion policy.

Packet loss bounds for asynchronous bufferless optical packet switches with limited range wavelength converters

In this paper a parametric cost model is applied to compare switching fabrics sharing a reduced number of fixed/tunable wavelength converters with a fully equipped architecture. This cost model can be used to evaluate in which switch configuration a sharing scheme leads to effective cost reduction, according to the cost parameters. Sample results show how sharing wavelength converters is not always the best choice, in particular when the cost ratio between a wavelength converter and an optical gate is low. Actually sharing converters requires a relevant number of additional optical gates. The sharing leads to reduced cost when the number of fibers/wavelengths is not very high, while the fully equipped architecture is often preferable for large switch sizes. Furthermore, fixed wavelength converters lead to further cost saving in many cases.

Sharing wavelength converters in optical switching fabrics: When, how, and which kind of?

Passive Optical Networks (PONs) are one of the preferred technologies to deploy broadband access networks. As time passes, end users presuppose network connectivity to be always available, and expect PONs to be highly dependable. Yet operators, from an economic view, are interested in the costs related to failures. Thus, PONs dependability and associated costs have been extensively studied, but only focusing on hardware failures. Contrarily, this paper performs a thorough analysis of the impact of software failures in failure-related costs. Based on real empirical data, software failures are thoroughly characterized and classified in four different categories according to their severity. Also, the effect of software failures on the behavior of PON’s fiber protection and recovery mechanisms is detailed. Software failures are included into a Markov cost model, implementing a comprehensive cost framework. This way, the dependability-related costs of PONs are analyzed, accounting for hardware and software failures, as well as for the consequences of software failures on well-known PON protection mechanisms. Moreover, how the testing phase duration and user profile (residential or business) impact these costs is pinpointed.

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Norvald Stol

Papers

Contention resolution using Parametric Wavelength Converters: Performance and cost analysis

Optimized design of delay-line buffers with an input-feedback mechanism for asynchronous optical packet switching networks.

Packet loss bounds for asynchronous bufferless optical packet switches with limited range wavelength converters

Sharing wavelength converters in optical switching fabrics: When, how, and which kind of?

Influence of software and hardware failures with imperfect fault coverage on PONs OPEX