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

In this paper we propose an end-to-end solution for urban infrastructure-to-vehicle traffic data delivery based on a class of unequal error protection (UEP) rateless codes called expanding window fountain (EWF) codes. The proposed solution relies on attractive features that rateless codes introduce to networks with unpredictable dynamics: the universal capacity approaching property which is well-matched to time-varying behavior of wireless links, and the innovative nature of each encoded packet which makes both time-consuming retransmission and content-reconciliation mechanisms unnecessary. Furthermore, usage of EWF codes allows separation of delivered data in importance classes with different error protection and recovery time guarantees, enabling mobile users to retrieve more important information more reliably and in shorter time span, thus making the proposed solution suitable for time-critical services. The addressed urban communication scenario consists of large number of sensors that sample and relay traffic flow information to network of Access Points (APs). APs use the existing underlying communication infrastructure, such as metropolitan area networks (MANs), to exchange traffic flow data, encode it using EWF coding principles, and finally disseminate it to roaming vehicles that join the network service in an ad-hoc manner in order to retrieve information regarding the surrounding environment. The proposed approach is suitable for real-time applications, such as frequent periodic reporting of urban traffic conditions, that could be used by on-board computers to provide improved navigation for end-users.

Urban Infrastructure-to-Vehicle Traffic Data Dissemination Using UEP Rateless Codes

This paper deals with a variable rate discrete multitone modulation system for broadband power-line communications, based on the bit-loading algorithm proposed by Leke and Cioffi. In the proposed system a suitable least mean square channel estimator is considered, which is based on the insertion of a training sequence (TS). The proposed approach will be compared with the ideal channel estimates, showing its effectiveness. Moreover, different TS lengths will be compared. The system performance, expressed in terms of bit rate and bit-error rate, is derived by simulation with and without estimation errors. The propagation environment has been assumed as a frequency-selective multipath fading channel with additive colored Gaussian noise, according to the in-building networks model

A rate adaptive bit-loading algorithm for in-building power-line communications based on DMT-modulated systems

Vertical approach still largely dominates smart devices systems. Even in IoT, proprietary protocols and backend systems are still common. The presented solution aims at harmonizing different standards and architectures, improving sustainability and security. It also allows to use a IaaS approach to further enhance the sensor networks business model.

Short paper: Overcoming IoT fragmentation through standard gateway architecture

WiMAX is one of the most important technologies for providing a Broadband Wireless Access (BWA) in a metropolitan area. The use of OFDM transmission has been proposed to reduce the effect of multipath fading in wireless communications; moreover, multiple access is achieved by resorting to the use of OFDMA. Adaptive subcarrier allocation techniques have been selected to exploit the multiuser diversity, leading to an improvement of performances by assigning subchannels to the users accordingly with their channel responses. In this paper, three adaptive subcarrier allocation algorithms have been proposed; they are based on channel capacity and aim to assign an equal amount of capacity to all the users or to distribute the capacity proportionally to the users' channel conditions. The algorithms performances have been valued and compared in terms of bit error rate and throughput. The proposed strategies show a substantial improvement with respect to a static allocation, turning the multiuser diversity into a significant increase of data rate.

Adaptive Subcarrier Allocation Algorithms in Wireless OFDMA Systems

The demand for high-speed services and multimedia applications in wider wireless environments leads to the growth of wireless communications, due to the simplicity of installation and the reduction of costs with respect to traditional cabled links. In particular, WiMAX technology is considered one of the most prominent solutions capable to provide a Broadband Wireless Access in metropolitan areas. In this paper two schemes of adaptive modulation and coding are proposed with the aim of improving performances in Non Line-of-Sight communications, typical of urban environments. Through these techniques it is possible to switch the order of the modulation and the coding rate to better match the channel conditions, obtaining comforting results in terms of probability of error and throughput. The system has been modeled with a finite state structure in which every state consists in a possible scheme of transmission (i.e. a specific modulation and coding rate), and the switch among different states happens when multiple thresholds on channel attenuation are reached. The adaptation is realized at the physical level of the transmission for a WiMAX OFDMA structure. The two proposed techniques are suitable for different kind of traffic and, therefore, can be used for respecting different QoS requirements.

Romano Fantacci

Papers

Urban Infrastructure-to-Vehicle Traffic Data Dissemination Using UEP Rateless Codes

A rate adaptive bit-loading algorithm for in-building power-line communications based on DMT-modulated systems

Short paper: Overcoming IoT fragmentation through standard gateway architecture

Adaptive Subcarrier Allocation Algorithms in Wireless OFDMA Systems

Efficient Adaptive Modulation and Coding Techniques for WiMAX Systems