The effect of adjacent channel interference on the capacity of FDMAcellular systems

In FDMA cellular radio systems, the adjacent channel interference (ACI) is suppressed by the IF filter and also by a distance factor. Channels immediately adjacent to each other in frequency are assigned to different cells and, as such, the distance plays a role in reducing their mutual interference. The authors study the feasibility of optimizing the frequency spacing between carriers such that the combined effect of distance and IF filter will be enough to control the interference while allowing the maximum number of channels in a given bandwidth. They also study the decision feedback equalizer (DFE) as a means to reduce any excess ACI that results from reducing the channel spacing. The paper starts with a model that estimates the cumulative probability density of the signal to adjacent channel interference ratio (SIR) as a function of the channel spacing. They then present the results of a computer simulation study to estimate the performance of DFE in mitigating the effect of ACI. The results indicate that, under the conditions of slow flat fading and selection diversity, the DFE is very effective in reducing the effect of excess ACI interference which allows for a considerable reduction in the frequency spacing     

Development of statistical theory in reliability engineering: A survey

Statistical theory and its applications have played a significant role in the advancement of methodology and techniques for solving various problems in reliability engineering. Different criteria of aging have been introduced for modelling and characterizations of wear properties. Some real life engineering reliability operations arising in maintenance and replacement policies formulations are investigated as convolution, mixture and formation of coherent systems. Shock models are studied for shocks arriving according to Poisson process and causing damages with specific form of aging. Cumulative damage models have been also studied by many researchers. Statistical hypotheses testing are used to test whether a certain, censored or uncensored data has exponential or a specific aging propety.In this paper we present a unified state of the art type of survey for the research and developments in these problems. In particular we expose the main recent contributions, trace the trend of research and highlight the possible direction of further research.     

Generalized formulation of yield, variability, minimax and Taguchi circuit optimization problems

A generalized formulation of several circuit design problems, such as manufacturing yield optimization, circuit performance variability minimization, deterministic and statistical minimax design, Income Index maximization, Taguchi approach, etc., is developed. Several other “intermediate” problems can be defined in a sense similar to the one used in Zadeh's fuzzy set theory. A specific problem is identified by the selection of a generalized membership function ω(·) of the acceptability region, and a sequence of the values of the “smoothing” parameter β. Generalized gradient formulas are developed, and various possible algorithmic implementations discussed. As a result, trade-offs between different design strategies can be investigated by circuit designers, within one coherent methodology.     

Probabilistic approach to some problems of system safety

Measures of direct importance of unrepairable system components, based on the multilinear expansions, are introduced. Various characteristics of system quality of performance are discussed. Cases of binar and multistate components are studied. The measure of specific importance, considering the cost of reliability component's improvement, is defined. The multilinear expansion for a system of multistate components, giving the possibility to estimate measures of the direct importance of components and levels of components performance as well, is discussed. The limit transition to continuum structures is performed. Some measures of importance for repairable systems are introduced.     

The effects of flow split ratio and flow rate in manifolds

This paper reports a combined experimental and numerical investigation of three-dimensional steady turbulent flows in inlet manifolds of square cross-section. Predictions and measurements of the flows were carried out using computational fluid dynamics and laser Doppler anemometry techniques respectively. The flow structure was characterized in detail and the effects of flow split ratio and inlet flow rate were studied. These were found to cause significant variations in the size and shape of recirculation regions in the branches, and in the turbulence levels. It was then found that there is a significant difference between the flow rates through different branches. The performance of the code was assessed through a comparison between predictions and measurements. The comparison demonstrates that all important features of the flow are well represented by the predictions.     

Analysis of a soliton-based logic module for a ring network

We analyze and numerically study the code-matching logic module that is the central element in a proposed soliton-based ring network system running at peak rates of 100 Gb/s. The proposed network is packet-switched, and fast logic is required to route each packet. That is the function of the code-matching logic module, and four soliton logic gates that can perform fast logic are the key devices in its design. The behavior of the code-matching logic module is governed by a large set of parameters, and we simulate it by varying many of these parameters. The physical effects that occur in these devices and their significance are analyzed. The results indicate that the logic module will work but within a restricted parameter range     

An overview of the Telecommunications Information NetworkingArchitecture

The Telecommunications Information Networking Architecture (TINA) Consortium is an international collaboration aiming at defining and validating an open architecture for telecommunication services for the broadband, multimedia, and information era. The architecture is based on distributed computing, object orientation, and other concepts and standards from the telecommunications and computing industries. This paper provides an introduction to TINA. First, it presents an overall view of TINA, followed by a brief introduction to the main parts of the architecture, namely the computing, network, service, and management architectures. This is followed by a brief overview of interworking and migration scenarios for legacy systems. Finally, an overview of a tool-set to aid service specification and design is presented     

Theoretical investigation of a free-electron maser operating with aTEM transmission line

The possibility of using the transverse electric magnetic (TEM) transmission line in free-electron masers (FEM) is discussed. It is shown that at the centimeter and long-millimeter wavelengths such transmission lines allow one to combine the advantages of an open cavity and a waveguide-based resonator. A particular case of an FEM-based on the use of a shielded two-wire transmission line is investigated theoretically. A mathematical approach that allows one to calculate transmission-line parameters important to the FEM application is developed. It is based on the use of the integral equation technique and on a new representation of the Green function of the internal region of a circle, which was obtained in this paper. Numerical analysis of effective mode area, wave impedance, and attenuation constant was made for the odd TEM mode, which is excited in FEM operation. The FEM under research at Tel Aviv University was considered as an example. The frequency dependence of gain for an FEM operating in the linear regime was calculated. That the obtained gain value is much higher than the ohmic losses in the transmission line shows the possibility of using the TEM transmission line in this FEM