Compared Analysis of Metro Networks Supported by Graph Theory

This paper brings into focus the topological and geographical evaluation of metro networks through the definition of a methodological approach based on a set of indicators, a lot of which are defined in the sector literature. Once the methodology was stated, the results of an application on the metro networks of 13 big metropolitan areas were illustrated. Statistical comparative analyses are proposed to classify networks.     

Spreading Codes Generator for Wireless CDMA Networks

The prime characteristic of spread spectrum modulated signals is that their bandwidth is greater than the information rate. In this way a redundancy is introduced that allows the severe levels of inteference inherent in the transmission of digital information over radio and satellite links to be overcome. Current spread spectrum applications are primarily in military communications; nevertheless, there is growing interest in this technique for third generation mobile radio networks (UMTS, FPLTS, etc.) with open discussion regarding the practicality of using a multiple access system based on spread spectrum techniques (CDMA). However, in order to support as many users in the same bandwidth as other multiple access techniques such as TDMA or FDMA, it is important how to generate large families of sequences that present low cross-correlation. The aim of this paper is to describe a spreading codes generator that can produce a large number of PN sequences with good properties of auto- and cross-correlation. Moreover, the codes generated shows high unpredictability and good statistical behaviour. This also allows the implementation of some features that are common on military networks such as message privacy (increasingly important in commercial networks) without additional cost. The structure presented shows itself to be advantageous for high speed generation of codes at a low cost, low power consumption (allowing longer life for batteries), small size and simplicity of implementation, essential ingredients for commercial equipment. Another attractive feature is its structural parallelism, useful in VLSI implementations. All of these features render it potentially suitable for the implementation of channel bandwidth sharing systems in future wireless personal communications networks.     

A pseudo-neural system for hypothesis selection

The article describes a system for hypothesis elicitation and ranking formed by a net of computational elements obtained by modifying the classical neural model of Caianiello. This neural structure was chosen on the basis both of knowledge representation and of parallel processing considerations. the two fundamental components of the system are an elaboration layer and, in case the available evidences are insufficient to trigger explanatory hypotheses, a query layer that enables the system to gather additional information. Algorithms that help setting the crucial variable parameters of the net are described in the Appendix. © 1992 John Wiley & Sons, Inc.