A 3G network is a magnificently complex object embedded in a highly heterogeneous and ever-changing usage environment. It combines the functional complexity of the wireless cellular paradigm with the protocol dynamics of TCP=IP networks. Understanding such an environment is more urgent and at the same time more difficult than for legacy 2G networks. Continuous traffic monitoring by means of an advanced system, coupled with routine expert-driven traffic analysis, provides an in-depth understanding of the status and performances of the network as well as of the statistical behaviour of the user population. Such knowledge allows for a better engineering and operation practice of the whole network, and specifically the early detection of hidden risks and emerging troubles. Furthermore, the exploitation of certain TCP=IP dynamic behaviour, particularly the TCP control-loop, coupled with information extracted from the 3GPP layers, provides a cost-effective means to monitor the status of the whole network without requiring access to all network elements. In this article the main lessons are summarized learned from a two-year research activity on traffic monitoring and analysis on top of an operational 3G network.Keywords: traffic monitoring; traffic analysis; 3G; cellular networks; GPRS; UMTS Analyse und Monitoring von Datenverkehr in 3G Netzwerken: ein Erfahrungsbericht aus dem METAWIN-Projekt.Ein 3G-Mobilfunknetz stellt ein extrem komplexes Gebilde dar, das in ein stark heterogenes und stä ndig wechselndes Umfeld eingebettet ist. In ihm werden komplexe Funktionen der Mobilfunkü bertragung mit TCP=IP-Protokollen verbunden. Ein tiefes Verstä ndnis dieses Systems ist dringend erforderlich, aber sehr schwierig im Vergleich zu vorhandenen 2G-Netzen. Nur die kontinuierliche Beobachtung dieses modernen Ü bertragungssystems erlaubt es, sowohl die Leistungsfä higkeit des Netzes zu verstehen als auch das statistische Benutzerverhalten zu interpretieren. Die daraus gewonnenen Erkenntnisse begü nstigen sowohl eine verbesserte Netzplanung als auch einen optimalen Betrieb und gestatten es darü ber hinaus, verborgene Risiken und vorhandene Schwierigkeiten sehr frü h zu erkennen. Insbesondere erlaubt die Beobachtung bestimmter TCP=IP-Dynamik gemeinsam mit der Information, die aus den 3GPP-Schichten gewonnen wird, eine kostengü nstige Mö glichkeit, den Zustand des Gesamtnetzes zu erfassen ohne jedes Einzelelement des Netzes zu erfassen. In diesem Artikel sind die wesentlichen Erkenntnisse zusammengefasst, die in Folge eines zweijä hrigen Forschungsprojektes zur Beobachtung und Analyse eines 3G-Mobilfunknetzes gewonnen wurden.
This paper analyzed the spatial distribution of drought at meteorological stations on the Lim valley (Plav, Andrijevica, Berane and Bijelo Polje) and on the upper course of the river Ibar (Rožaje). The goal of this research is to point out the modern climatic characteristics in relation to the current state of aridization, which is a limiting factor for economy of the population in many areas throughout the world. The method used for such purposes is the De Marton drought index. Results of the research indicated a decrease in the annual drought index through the Lim valley, with the highest values for Plav (IDM=61,9), and the lowest for the lowest downstream station Bijelo Polje (IDM=41,3). The values of this climate index indicate the conditions of very humid (Berane, Bijelo Polje and Rožaje) and extremely humid climates (Plav and Andrijevica), with huge drainage and forest vegetation. By applying the De Marton index on a seasonal and monthly level, the highest values of this indicator were established in the winter season.
The paper analyzed basic physical-geographical characteristics and changes caused by afforestation. The aim of the paper is to point out the transformation of the natural environment initiated by afforestation, to present positive and negative implications of this action, and to emphasize the importance of the consideration of the cause-and-effect relationships during concrete action in the field. By applying analytical-synthesis and comparative methods, a presentation of the natural features of the Deliblato sand and changes that were made as a result of afforestation, is given. The results of the research present positive changes which are reflected in the stabilization of unbound sand, development of the pedogenetic process and improvement in the microclimate conditions in the forested sectors. Negative changes in afforestation are reflected in the reduction of the area's steppe vegetation and the consequent intensity of forest fires.
The paper analyzed the impact of tourism development on changes in the employed population in the service sectors by individual activities. The aim of this paper is to point out the relationship between changes in the number of tourists and changes in the number of employed population in service activities. The area of research is limited to the territory of the city of Belgrade. It cover an area of 3.223km2 . The basic methodological procedures used for research are mathematical - statistical methods: Pearson's correlation coefficient (r), testing the significance of the correlation coefficient (t test) and causal relationship (R). By applying the mentioned methods, a strong connection has been established between the growth of tourist traffic and the growth of the number of employed population in the service delivery activities on the territory of Belgrade.
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