il the 1980s accompanied by mobile telephony worldwide from the 1990s. Of course, one should not forget to mention television and radio as important telecom- munication services during the twentieth century, and they continue to be SO in the twenty-first century. ICT has created a globally connected world, not only giving people the ability to com- municate with each other but also opening up access to information and facilitating the exchange of information. The foundation of such an ICT world (the terms ICT and telecommunications will be used interchangeably in this book) lies in the introduction of digital systems and networks in the 1970s and 1980s, which provided the possibility for all information from different sources and of different types (e.g. voice, video, data, mul- timedia) to be transferred over the global telecommunications infrastructure by using series of bits and zeros (i.e. in a digital form). When information is coded at the source as series of ones and zeros, all such information can be transferred over the same telecom- munications networks and accessed via the same devices - if, of course, the networks are created in such a manner. The Internet has provided the required openness to transfer all different types of information over the same network, which is present and working well in the second decade of the twenty-first century and is expected to continue in a similar manner in the future. However, telecommunication networks are interconnected on a local, regional, and global scale to be able to transfer the information between any two or more communication endpoints on the Earth, SO the telecommunication ser- vices are global. Therefore, the quality of telecommunication services which is applied in a single network or in a single country has influence on the end-to-end quality of that service. So, the quality cannot be considered only at national or regional level, it needs QoS for Fixed and Mobile Ultra-Broadband, First Edition. Toni Janevski. © 2019 John Wiley & Sons Ltd. Published 201