tailieunhanh - Wireless địa phương vòng - lý thuyết và ứng dụng P9

In the past three decades there were big social, economic and technological changes in the world. Scientific and technological advancement, informing of wide circle of people and their inclusion in the learning process are the main characteristics of this period. In such conditions, the need came up for exchanging different kind of messages, . transmission of different kind of signals, governing the extremely fast development of the telecommunications systems. With utmost certainty it can be said that there are very few human activities that experienced such basic, qualitative and quantitative changes in their development as modern telecommunications. . | Wireless Local Loops Theory and Applications Peter Stavroulakis Copyright 2001 John Wiley Sons Ltd ISBNs 0-471-49846-7 Hardback 0-470-84187-7 Electronic 9 WLL as an Interférer Miroslav Dukic Introduction In the past three decades there were big social economic and technological changes in the world. Scientific and technological advancement informing of wide circle of people and their inclusion in the learning process are the main characteristics of this period. In such conditions the need came up for exchanging different kind of messages . transmission of different kind of signals governing the extremely fast development of the telecommunications systems. With utmost certainty it can be said that there are very few human activities that experienced such basic qualitative and quantitative changes in their development as modern telecommunications. One of the characteristic examples of the fast development and wide usage of new technologies are professional radio systems. Terrestrial microwave links and corresponding satellite telecommunication systems are the most widely used professional radiosystems. Together with intercontinental cable links they are today the grounds for national and worldwide telecommunication systems. The basic problem in the current state of development of modern professional radio systems is their coexistence. The fact is that the technologically available bands and satellites orbits inherent and restricted resources show that their usage must be rational and that they are the main factor in solving the coexistence problem between old systems and newly developed PCS Personal Communication Systems . As a consequence of limited available frequency bands different professional radio systems operate in the same or near frequency bands which is very disadvantageous regarding the coexistence. On the other side the global need for telephone network access is driven by pent-up demand for existing telecommunications services by economic .