Phasing, 22 References, 25 2.1 Introduction Standards are defined in the 3rd generation partnership project (3GPP), with the actual contributions coming from members of the regional standards bodies that participate in 3GPP activity. More than 600 companies are members of 3GPP via their regional standards organizations. Before standards work begins, however, the requirements and use case are defined. This occurs on the one hand in forums like ITU-R (International Telecommunication Union Radio sector) and on the other hand in industry forums, especially in the Next Generation Mobile Network (NGMN) Alliance. Pre-standards research forums are also involved, for example, the projects part of the 5G Infrastruc- ture Public Private Partnership (5G-PPP) and 5G Mobile Communications Promotion Forum (5GMF), which aim to collect research inputs both from industry and academia before actual standards work begins. There are other forums that take interest in spe- cific areas of 5G development for the next phase of 5G development, as discussed in Chapter 15. This chapter covers the key activities leading to 5G specification finalization in the International Telecommunication Union (ITU), NGMN, and 3GPP. ITU has been contributing to international standardization of mobile commu- nication systems through the standard known as IMT (International Mobile 5G Technology: 3GPP New Radio, First Edition. Edited by Harri Holma, Antti Toskala, and Takehiro Nakamura. © 2020 John Wiley & Sons Ltd. Published 2020 by John Wiley & Sons Ltd. 2 5G Targets and Standardization Table 2.1 Previous international standardization for mobile communications systems by ITU. Example of radio interface technologies IMT-2000 WCDMA/HSPA/LTE, cdma2000, TD-SCDMA, WiMAX, etc. IMT-Advanced LTE-Advanced, Wireless-MAN-Advanced Telecommunications). This standardization has been achieved through develop- ment of ITU-R Recommendations on radio interface technologies for the terrestrial components of IMT-2000 and IMT-Advanced, and these technologies have been used for