e Sky Network, and Celfinet. He previously worked for PHI Networks (Israel), AT&T (the US), and Yota (Russia). About the reviewers Karthik Chandrasekaran has 19+ years of experience working in the telecom industry, with 10 years spent on IP Multimedia Subsystem (IMS), Voice over LTE (VoLTE), and most recently, 5G SA and Voice over NR (VoNR). He has worked on multiple launches with T-Mobile USA. He has a wide range of experience within the telecom domain, including IMS, SMS, charging, and end-to-end voice launches in packet-switched telecom networks. He has worked across multiple companies within the telecom domain, such as TCS, Sasken, Nokia Siemens Networks, Mavenir, and T-Mobile. With his experience of working on the first VoNR launch in North America with T-Mobile, he has a unique set of knowledge to help review voice aspects of packet-switched networks. Payam Alavizadeh has worked in the mobile communication industry for more than 20 years, with 16 years specifically dedicated to RF engineering. He has performed network investigation with the latest methods for improving network quality. He is CEO and Founder of the Semantic Communication Ltd and works with Canadian mobile operators in British Columbia Canada as a 5G RF engineering consultant focusing on improving mobile network quality. His research interests include QoS ,QoE, XR, and the next generation of mobile networks. He was selected as the IEEE DAY 2019 Winnipeg, Canada Section Ambassador at the University of Manitoba. He was evaluated by the IEEE Admission and Advanced Committee and was promoted to the grade of IEEE Senior Member (SMIEEE) on Nov 2020. I'd like to thank my wife, Mana Moosavi, who always supports me when I am reviewing chapters. Thanks to everyone on the Packt Publishing team who helped me so much. Special thanks to Rahul Nair, Neil D'mello, and Mohd Riyan Khan, the ever-patient publishing managers, and Aryaa Joshi for coordinating this project. I'd like to thank the authors; working in this field would not be possible without your sup