rial presented in the book: Apostolos Papathanassiou, Intel Corpo- ration; Jaemin Han, Intel Corporation; Krzysztof Kordybach, Nokia; and Markus Dominik Mueck, Intel Corporation. List of Contributors Alexander (Sasha) Sirotkin is a senior engineer with 20 years of experience in telecommu- nications, international standardization, intellectual property, machine learning, real-time systems, and open source. Currently his primary focus areas are 4G/LTE and 5G/NR Radio Access Network (RAN) Architecture, and licensed and unlicensed spectrum integration and co-existence. In stan- dards, Sasha contributed to 3GPP RAN2, RAN3, and RAN plenary, where he served as rapporteur for multiple specifications, as well as work and study items. Currently Sasha serves as the 3GPP RAN3 vice chairman and leads the Intel's RAN3 delegation. In addition to 3GPP, Sasha has contributed to various other standards development organi- zations and industry fora, such as IEEE, O-RAN, WFA, WBA, ETSI, and 5G Americas. Prior to working in the field of wireless (802.11/Wi-Fi and cellular) communications, Sasha was actively involved in the open source, primarily the Linux operating system. Having been an open source enthusiast since 1993, Sasha was one of the first to realize that the potential of Linux lies not SO much in the desktop, but in embedded and real-time systems, which he worked to promote long before the first version of Android was conceived. Sasha received an MSc in machine learning and BSc degrees in computer science and physics from Tel-Aviv University. Sasha lives with his wife and children in Hod HaSharon, Israel. In his spare time, which his kids make sure he doesn't have too much of, he occasionally goes scuba diving and alpine skiing (usually not on the same day, even though that is sometimes technically possible in Israel), and practices Kyokushin Karate. List of Contributors Contributors Reza Arefi, Intel Corporation - Washington DC, USA Nicolas Chuberre, Thales Alenia Space - Pibrac, France Stefano Cioni, European Space Agency