Modern telecommunications make it possible to transmit images, sound and text all over the world.These technical means are neutral with respect to their content. However, telecommunications are at the origin of debates in terms of the standardization of the culture of national identity or, on the contrary, of new possibilities of expression in traditional spaces.The development of hertzian, terrestrial and then satellite means of transmission has favoured the large-scale deployment of mass media (radio, television, etc.) in societies, thus modifying traditional ways of thinking and cultural patterns.The main idea behind the design of this book is to provide teachers, researchers and students with a tool showing the evolution of communication, and especially the functioning of the radiotelephone network, as well as the study of interface security. The telecommunication engineer must be able to measure the propagation characteristics when installing the network and, above all, know the causes of degradation of the wave as it travels along the path.