Browsing by Issue Date, starting with "2007-04"
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- Cost/Revenue Optimisation of Multi-Service Cellular Planning for City Centre E-UMTSPublication . Velez, Fernando J.; Anastácio, Nuno; Merca, Francisco; Cabral, Orlando Manuel BritoAn overview of All-IP Enhanced Universal Mobile Telecommunication System, E-UMTS, service needs in the business city centre, BCC, scenario is first presented. Then, E-UMTS traffic generation and activity models are described and characterised. System level simulations are carried out and the enhanced performance is demonstrated based in a single quality parameter, which simultaneously accounts for call blocking and handover failure probabilities. End-to-end delays do not present a limitation. By considering a grade of service of 1% for the quality parameter, and different hypothesis for costs and prices, an optimum coverage distance is obtained around ~200-425 m, which maximises the supported throughput per km2. However, results for the profit in percentage indicates that coverage distances in the range 395-425 m should be used in BCC.
- Between facts and news: Journalism, common sense knowledge and public spherePublication . Correia, João Carlos; Vizeu, AlfredoAfter the optimism which followed the falling of the Berlin Wall, one has found out that the alternative to the Cold War wasn’t the Global Peace. Regional conflicts have grown stronger, becoming more intense than ever. At several levels, some taken-for-granted evidence were shaken by new social, cultural, political and technological phenomena. Risk, contingence, and entropy became major categories of contemporary theoretical approaches. The post-modern society appears now to contemporary thought as a new world shaped by social and cultural fragmentation, and the eruption of new identities. The emergence of a novel public sphere concerned, mainly, with emergent social and political rights of minorities; and the constant flow of people, either immigrants or refugees crossing cultural and geographic spaces, brought to light new and old identities, leading those ancient and secure borders to collapse. Some confluent phenomena such as environmental problems, contemporary hazards associated with nuclear power, chemical pollution, terrorism, changes on cultural attitudes, the “women’s lib” and their subsequent arrival to labour market, the crisis of the old traditional mediation apparatus (Church, Family, Tradition), the decadence of ideologies, emerge as main features of a society where everything that was solid melted on air (Adam, Beck, e van Loom 2000: pp 6-7). Increasing reflexivity in face of answers once taken-for-granted challenged by those enormous changes, and anxiety in face of a changing world makes that concern with security and risk become a major problem of our societies. Insecurity is thus an existential context: we don’t know anymore how to go on the basis of tradition. The implicit validity claims of taken-for-granted values and traditions become problematic and potentially questioned (Adam, Beck e van Loom, 2000:37)- Throughout this text, one appeals to a theoretical approach where we can find elements from the phenomenology of Lebenswelt, from the theory of multiple realities, from the theory of social representations and also from the analysis of the didactic and safety functions of journalism. With this approach, we achieve the conceptual framework adequate to perception and analysis of the media representation of a complex society, confronted with the insecurity of its taken-for-granted structures and with new enclaves of meaning. The appearance of new provinces of meaning is related with the emergence of a pluralistic public sphere and with the eruption of some expressions of identity and life-styles concerned with the so called post-modern changes
- Event-Based Simulation for Multi-rate Multi-service Traffic Validation in B3G SystemsPublication . Juarez, Jesus M.; Paulo, Rui R.; Velez, Fernando J.A multi-service traffic model is briefly presented, and its validation is achieved by using event-based simulation results which consider the burstiness of traffic. A simulator was produced to extract conclusions about blocking and handover failure probabilities in a multi-service bursty traffic context. Simulations, were performed for different cases, from single- to multi-service situations, and from absence to presence of mobility. Besides quality of service results in the air interface, including blocking and handover failure probabilities, the simulator allows for extracting conclusions about the validation of the Bernoulli-Poisson-Pascal model for the computation of the on/off blocking probability, the ratio between the number of call rejected at the beginning of an on period and the total number of bursts generated during a session. In the single-service case, the theoretical and the experimental values of on/off blocking probability are close to each other, and there is an almost perfect concordance between theoretical and simulation values when the average sojourn time in cells is equal to the average holding time. In the multi-service case, the behaviour is not exactly the same but a coherent behaviour is achieved for an average traffic per user up to 0.10 Erl.