Disruptive events in high-density cellular networks

Stochastic geometry models are used to study wireless networks, particularly cellular phone networks, but most of the research focuses on the typical user, often ignoring atypical events, which can be highly disruptive and of interest to network operators. We examine atypical events when a unexpected large proportion of users are disconnected or connected by proposing a hybrid approach based on ray launching simulation and point process theory. This work is motivated by recent results using large deviations theory applied to the signal-to-interference ratio. This theory provides a tool for the stochastic analysis of atypical but disruptive events, particularly when the density of transmitters is high. For a section of a European city, we introduce a new stochastic model of a single network cell that uses ray launching data generated with the open source RaLaNS package, giving deterministic path loss values. We collect statistics on the fraction of (dis)connected users in the uplink, and observe that the probability of an unexpected large proportion of disconnected users decreases exponentially when the transmitter density increases. This observation implies that denser networks become more stable in the sense that the probability of the fraction of (dis)connected users deviating from its mean, is exponentially small. We also empirically obtain and illustrate the density of users for network configurations in the disruptive event, which highlights the fact that such bottleneck behaviour not only stems from too many users at the cell boundary, but also from the near-far effect of many users in the immediate vicinity of the base station. We discuss the implications of these findings and outline possible future research directions.Comment: 8 pages, 11 figure

Transatlantic relations are alliances a funcion [i.e. function] of an external threat?

Current European-U.S. transatlantic relations represent the heritage of a large number of international alliances and institutions that were founded at a time when there was a bipolar world, a world dominated by the United States and the Soviet Union. Today fourteen years after the end of the Cold War, some national leaders question the continued viability of these international alliances and institutions. In their references to international relations, realist and liberal theorists reflect significant ideological differences, which have considerable influence on transatlantic relations. This thesis considers a central question pertaining to the future of transatlantic relations between Europe and the United States: Will the presence, or absence, of an external threat to the countries involved be the deciding factor in their willingness to cooperate in security alliances? It is a significant question, and investigating it provides a better understanding of future uses of alliances and their role in world politics. Recently, two specific historical occurrences decisively modified the security landscape worldwide: the end of the Cold War 1991 and almost two decades of violent, deadly acts of international terrorism. Since the breakdown of the Warsaw Pact 1991 and the dissolution of the Soviet Union, which made former satellite states suddenly independent, numerous eastern European countries have applied for membership in NATO and the European Union. At the same time, organizations such as, especially, the EU and NATO, have had to deal with the competitive and often contradictory interests of member states. This thesis will focus with emphasis on France, Germany, and United States because the differences in their positions inside NATO are most significant.http://archive.org/details/transatlanticrel109452130Approved for public release; distribution is unlimited