There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

Information Theory and Reliable Communication

: This thesis applies neural network feature selection techniques to multivariate time series data to improve prediction of a target time series. Two approaches to feature selection are used. First, a subset enumeration method is used to determine which financial indicators are most useful for aiding in prediction of the S&P 500 futures daily price. The candidate indicators evaluated include RSI, Stochastics and several moving averages. Results indicate that the Stochastics and RSI indicators result in better prediction results than the moving averages. The second approach to feature selection is calculation of individual saliency metrics. A new decision boundary-based individual saliency metric, and a classifier independent saliency metric are developed and tested. Ruck's saliency metric, the decision boundary based saliency metric, and the classifier independent saliency metric are compared for a data set consisting of the RSI and Stochastics indicators as well as delayed closing price values. The decision based metric and the Ruck metric results are similar, but the classifier independent metric agrees with neither of the other metrics. The nine most salient features, determined by the decision boundary based metric, are used to train a neural network and the results are presented and compared to other published results. (AN)

/pdf/nonlinear-time-series-analysis-1j3a35n4y3.pdf

Nonlinear Time Series Analysis.

This document provides updates to IEEE Std 802.16's MIB for the MAC, PHY and asso- ciated management procedures in order to accommodate recent extensions to the standard.

IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems Draft Amendment: Management Information Base Extensions

This paper deals with a turbo multiuser detector suitable for applications in overloaded coded DS-CDMA systems. The turbo-MUD receiver is based on the use of a linear MMSE detector in the first iteration and a parallel interference cancellation scheme in the successive ones. The inputs of the interference cancellator are both the detector outputs and the soft information from a bank of turbo decoders. The performance of the proposed receiver has been derived by means of computer simulations and applications of the density evolution theory: in particular, this technique permits to properly evaluate the number of MMSE iterations, simplifying the overall receiver design.

Design of Turbo-MUD Receivers for Overloaded CDMA Systems by Density Evolution Technique

Different dynamic channel allocation (DCA) approaches based on the evaluation of a cost function are proposed. The scenario considered is low earth orbit and geostationary orbit mobile satellite systems. A suitable user mobility model has been defined to generate interbeam handover requests. Different alternatives to manage interbeam handovers have been investigated. Among them, the most promising solution seems to be the queuing of handover requests. The quality of service parameters that have been considered are: blocking probability for new call arrivals, handover failure probability and the probability of incompletely served call owing to the initial blocking or to the failure of a subsequent handover request. Comparisons among the proposed DCA techniques and the fixed channel allocation technique have been carried out to find a solution that represents a good trade-off between the blocking performance and the required signalling load.

/pdf/call-blocking-performance-for-dynamic-channel-allocation-1vf4b8rfwc.pdf

Call blocking performance for dynamic channel allocation technique in future mobile satellite systems

We propose an energy-efficient resource allocation framework suitable for multicast service delivery over 3GPP's Long Term Evolution Advanced Single Frequency Network evolved Multimedia Broadcast and Multicast Service networks. A key aspect of the considered system model is that multicast communications are delivered according to the Random Linear Network Coding (RLNC) principle. The proposed optimization framework aims at minimizing the transmission energy associated with the delivery of a set of multicast flows. The goal is achieved by jointly optimizing the transmission power and the RLNC scheme of each flow. Furthermore, we present a heuristic strategy that can efficiently find a good-quality feasible solution of the presented resource allocation model.

An Energy-Efficient Resource Allocation Scheme for RLNC-Based Heterogeneous Multicast Communications

Recently, ad-hoc networks have obtained a growing interest due to their advantages in many practical applications. One of the most critical points is the definition of an efficient medium access control (MAC) protocol that allows the transmission of packets generated by a node and routing of packets arriving from other nodes. This paper deals with a MAC technique based on code division multiple access (CDMA) scheme that adapts the used spreading factor to the network congestion in order to minimize the energy consumption and maximize the network throughput.

A MAC technique for CDMA based ad-hoc networks

In this paper, we present the comparison between a distributed and a centralized authentication protocol for wireless sensor networks (WSN). We outline the difference between authentication and key-agreement schemes and we propose a novel approach based on the use of polynomial functions to produce a distributed bi-directional authentication. The advantages of this approach are: speed of operation that can allow multiple subsequent authentications, thus support to mobility; balanced energy consumption if compared with the imbalanced centralized approach and the prevention of partition attacks. Copyright © 2008 John Wiley & Sons, Ltd.

Romano Fantacci

Papers

Design of Turbo-MUD Receivers for Overloaded CDMA Systems by Density Evolution Technique

Call blocking performance for dynamic channel allocation technique in future mobile satellite systems

An Energy-Efficient Resource Allocation Scheme for RLNC-Based Heterogeneous Multicast Communications

A MAC technique for CDMA based ad-hoc networks

Fast distributed bi‐directional authentication for wireless sensor networks