t level are pointed to the relevant standards. This chapter aims to orientate the reader as a guide to navigating the many standards. 8.1 Overview of the ITU The ITU is a multilateral organization headquartered in Geneva, Switzerland. It is an agency of the United Nations that is specialized in information and communication technologies. The ITU web- site (https://www.itu.int) gives the following summary of its role: Founded in 1865 to facilitate international connectivity in communications networks, we allocate global radio spectrum and satellite orbits, develop the technical standards that en- sure networks and technologies seamlessly interconnect, and strive to improve access to ICTs [Information and Communication Technologies] to underserved communities world- wide. Every time you make a phone call via the mobile, access the Internet or send an email, you are benefitting from the work of ITU. The ITU consists of three main areas of activity organized into the following sectors: ITU Telecommunication Standardization Sector (ITU-T): Mainly responsible for the devel- opment of standards to support telecommunications and other technical areas such as audio and video compression ITU Radiocommunications Sector (ITU-R): Mainly responsible for harmonized wireless and radio standards, as well as allocation of spectrum and satellite orbits ITU Telecommunication Development Sector (ITU-D): Responsible for numerous programs centered on improving access to modern telecommunications services for people living in un- derserved regions and emerging markets For the purposes of this book, the most important sector is the ITU-T, which supports the telecom- munications industry by developing a very large number of standards-although the ITU-T prefers to call them recommendations. For the mobile, broadcasting, and satellite industries, the ITU-R also plays a very important role. The ITU-T sector is broken up into numerous study groups (about 11), and each of these study groups has various subgroups that the ITU-T calls questions 