Errors and power when communicating with spins

We consider a network composed of a finite set of communicating nodes that send individual particles to each other, and each particle can carry binary information. Though our main motivation is related to communications in nanonetworks with electrons that carry magnetic spin as the bipolar information, one can also imagine that the particles may be molecules that use chirality to convey information. Since it is difficult for a particle to carry an identifier that conveys the identity of the “source” or “destination”, each node receives particles whose source cannot be ascertained since physical imperfections may result in particles being directed to the wrong destination in a manner that interferes with the correctly directed particles, and particles that should arrive at a node may be received by some other node. In addition, noise may randomly switch the polarity of particles, and in the case of magnetic spin we can also have the effect of entanglement.We estimate the error probability in such a multipoint network as a function of the rate of flow of particles, and the power consumption per communicating pair of nodes. We then design a bipolar detector and show that it can significantly eliminate the effect of errors

Why Noise and Dispersion may Seriously Hamper Nonlinear Frequency-Division Multiplexing

The performance of optical fiber systems based on nonlinear frequency-division multiplexing (NFDM) or on more conventional transmission techniques is compared through numerical simulations. Some critical issues affecting NFDM systems-namely, the strict requirements needed to avoid burst interaction due to signal dispersion and the unfavorable dependence of performance on burst length-are investigated, highlighting their potentially disruptive effect in terms of spectral efficiency. Two digital processing techniques are finally proposed to halve the guard time between NFDM symbol bursts and reduce the size of the processing window at the receiver, increasing spectral efficiency and reducing computational complexity.Comment: The manuscript has been submitted to Photonics Technology Letters for publicatio

On the Security of the Automatic Dependent Surveillance-Broadcast Protocol

Automatic dependent surveillance-broadcast (ADS-B) is the communications protocol currently being rolled out as part of next generation air transportation systems. As the heart of modern air traffic control, it will play an essential role in the protection of two billion passengers per year, besides being crucial to many other interest groups in aviation. The inherent lack of security measures in the ADS-B protocol has long been a topic in both the aviation circles and in the academic community. Due to recently published proof-of-concept attacks, the topic is becoming ever more pressing, especially with the deadline for mandatory implementation in most airspaces fast approaching. This survey first summarizes the attacks and problems that have been reported in relation to ADS-B security. Thereafter, it surveys both the theoretical and practical efforts which have been previously conducted concerning these issues, including possible countermeasures. In addition, the survey seeks to go beyond the current state of the art and gives a detailed assessment of security measures which have been developed more generally for related wireless networks such as sensor networks and vehicular ad hoc networks, including a taxonomy of all considered approaches.Comment: Survey, 22 Pages, 21 Figure

Impact of 4D channel distribution on the achievable rates in coherent optical communication experiments

We experimentally investigate mutual information and generalized mutual information for coherent optical transmission systems. The impact of the assumed channel distribution on the achievable rate is investigated for distributions in up to four dimensions. Single channel and wavelength division multiplexing (WDM) transmission over transmission links with and without inline dispersion compensation are studied. We show that for conventional WDM systems without inline dispersion compensation, a circularly symmetric complex Gaussian distribution is a good approximation of the channel. For other channels, such as with inline dispersion compensation, this is no longer true and gains in the achievable information rate are obtained by considering more sophisticated four-dimensional (4D) distributions. We also show that for nonlinear channels, gains in the achievable information rate can also be achieved by estimating the mean values of the received constellation in four dimensions. The highest gain for such channels is seen for a 4D correlated Gaussian distribution

Submarine canyon dynamics - Executive Summary

Discussing submarine canyons dynamics through a multidisciplinary approach allowed to identify both advances in knowledge and remaining gaps concerning the controlling factors underlying the formation, development, ecological functioning and vulnerability of canyons at various time scales. As a result, we identified a number of recommendations for future research and actions that the interested reader will discover in this synthetic chapter, drafted as a collective effort in the months following our meeting. The subsequent chapters, each written by a workshop participant, detail the specificities and dynamics of of submarine canyons within and beyond the Mediterranean domain

Decision-Feedback Detection Strategy for Nonlinear Frequency-Division Multiplexing

By exploiting a causality property of the nonlinear Fourier transform, a novel decision-feedback detection strategy for nonlinear frequency-division multiplexing (NFDM) systems is introduced. The performance of the proposed strategy is investigated both by simulations and by theoretical bounds and approximations, showing that it achieves a considerable performance improvement compared to previously adopted techniques in terms of Q-factor. The obtained improvement demonstrates that, by tailoring the detection strategy to the peculiar properties of the nonlinear Fourier transform, it is possible to boost the performance of NFDM systems and overcome current limitations imposed by the use of more conventional detection techniques suitable for the linear regime

Connectivity beyond the urban community in central Italy

Two significant recent developments concerning the archaeology of Iron Age central Italy call for a fresh analysis of settlement dynamics in the region and their relations vis-à-vis one another. The first development is the reconsideration of ancient urban centres as single entities, and the need, which has mostly been advocated for the Classical and later historical Mediterranean, to examine the systems or networks within which these centres functioned. The second development is the increasing amount of fieldwork-based research in those regions that have been situated at the margins of scholarly interest. New data from such research increasingly allow us to see the networks or systems that linked these regions to better-known ones on the Tyrrhenian coast. Such developments enable us to reassess the importance traditionally given to the core urban area of central Italy, and to offer a more balanced framework for understanding the exchange dynamics among Iron Age Central Italian communities. This chapter intends to do precisely that, and in so doing, its aim is twofold: first, to decentralise central Italy in line with studies on other Mediterranean regions that have similarly dispelled distinctions between core urban areas and non-urban peripheries; second, to shift attention away from evolutionary and other categories towards a perspective that stresses connectivity and patterns of human mobility