Book excerpt: Telecommunication Systems and Technologies theme is a component of Encyclopedia of Physical Sciences, Engineering and Technology Resources in the global Encyclopedia of Life Support Systems (EOLSS), which is an integrated compendium of twenty one Encyclopedias. Telecommunication systems are emerging as the most important infrastructure asset to enable business, economic opportunities, information distribution, culture dissemination and cross-fertilization, and social relationships. As any crucial infrastructure, its design, exploitation, maintenance, and evolution require multi-faceted know-how and multi-disciplinary vision skills. The theme is structured in four main topics: Fundamentals of Communication and Telecommunication Networks; Telecommunication Technologies; Management of Telecommunication Systems/Services; Cross-Layer Organizational Aspects of Telecommunications, which are then expanded into multiple subtopics, each as a chapter. These two volumes are aimed at the following five major target audiences: University and College students Educators, Professional practitioners, Research personnel and Policy analysts, managers, and decision makers and NGOs