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)

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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 the performance evaluation of a cognitive overlay wireless sensor network relying on a low complexity spectrum sensing technique. In particular, the paper proposes a dynamic channels selection policy in order to improve the performance of a IEEE 802.15.4e sensor overlay network. Further, the paper proposes a suitable analytic model to carry out a performance evaluation analysis, in terms of throughput, packet dropping probability and energy efficiency. The obtained results highlight a remarkable gain with respect to classic approaches, without burdensome cost or complexity.

Performance Evaluation of an Adaptive Channel Allocation Technique for Cognitive Wireless Sensor Networks

In the last few years, the metropolitan area networks (MAN) have increased their popularity and attracted the interest of the most important research groups all over the world. Among several standards, IEEE 802.16 has taken a relevant role providing high data rate in a big covering range with low implementation costs and multi-traffic communications. The IEEE 802.16 networks can have a pre-defined structure, with a central base station (BS) covering a cell in which a variable number of subscriber stations (SSs) can work. This paper deals with the proposal of a quality of service (QoS) driven scheduling algorithm to be used in an IEEE 802.16 network where different traffic types coexist. In particular, the paper mainly focuses on best effort data and VoIP communications, by proposing a scheduling technique that allows an efficient resource management of both traffic types by considering their specific QoS flavor. The performance evaluation has been carried out by considering both the phases of contention and packet scheduling, by means of a theoretical approach and computer simulations. Numerical results show the performance of the proposed algorithm by focusing on a scenario where the BS schedules the best effort and VoIP traffics of several SSs. Copyright © 2008 John Wiley & Sons, Ltd.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/wcm.649

Performance evaluation of the MAC protocol in IEEE 802.16 systems with data and VoiP traffic scheduling

A new digital implementation of a receiver for digital communications is presented. The receiver structure performs the integration of a maximum a posteriori probability (MAP) carrier and clock synchronisation with the maximum likelihood (ML) demodulation. It is shown that the key feature of the receiver structure is that the same hardware is able to perform both operations; thus the receiver implementation complexity is greatly reduced. This scheme can be adapted to different modulation techniques suitable for digital communications, such as QPSK-O-QPSK and MSK. As examples, the application to QPSK and MSK signals is considered, owing to the interest of these modulation schemes for satellite communications.

Joint carrier and clock recovery for QPSK and MSK digital communications

The paper deals with the comparison of different multiple access techniques and different impulses in a multiple access communication system based on ultra wide band (UWB) impulse radio technology under non-ideal conditions. Several multiple access techniques and impulses have been designed and compared in the past, but mainly with the assumption of perfect synchronization of the users and perfect recovery of frame synchronization at the receiver. We drop these impractical assumptions. The results have been obtained by computer simulations. The sensitivity to synchronization errors of time hopping PPM and direct sequence multiple access techniques has been carried out with two different pulse shapes, the Gaussian monocycle and the doublet. The impact of multiple access interference is also reported in order to have an exhaustive comparison of UWB systems.

/pdf/impact-of-synchronization-errors-and-multiple-access-1giaaaitzm.pdf

Impact of synchronization errors and multiple access interference to the performance of UWB impulse radio systems

During last years modern telecommunication systems have achieved important results in terms of reliability, coverage and data rate, allowing a high variety of applications services. Among others, TETRA (Terrestrial Trunked Radio) is one of the most important in the professional market; in particular, the DMO (Direct Mode Operation) mode allows half-duplex direct communications among users without the need of an infrastructure. However, TETRA-DMO cannot perform multi-hop communications, limiting both the coverage and the scalability of the whole network. The idea behind our proposal is an integration between TETRA-DMO and another more flexible wireless system (e.g., IEEE 802.11), where the TETRA-DMO is the access technology, thus allowing the use of standard TETRA-DMO terminals, while the IEEE 802.11 technology can be used as a flexible multi-hop meshed backbone technology for interconnecting remote TETRA-DMO areas.

Romano Fantacci

Papers

Performance Evaluation of an Adaptive Channel Allocation Technique for Cognitive Wireless Sensor Networks

Performance evaluation of the MAC protocol in IEEE 802.16 systems with data and VoiP traffic scheduling

Joint carrier and clock recovery for QPSK and MSK digital communications

Impact of synchronization errors and multiple access interference to the performance of UWB impulse radio systems

Analysis and design of a TETRA-DMO and IEEE 802.11 integrated network