ed States), ARIB and TTC (Japan), CCSA (China), TSDSI (India), and TTA (South Korea). Global ATIS, USA Global policies ETSI, Europe CCSA, China standards ARIB, Japan TTC, Japan TTA, Korea Technical specification TSDSI, India Figure 4-4 3GPP and Regional SSOs The 3GPP project encompasses the end-to-end specification of the cellular system including radio access technologies, the cellular system, and the service framework. To address these technology areas, 3GPP has three technical specification groups (TSG): Radio Access Network (TSG RAN): Responsible for the radio parts of the network (mobile user equipment and base stations) for both frequency division duplex (FDD) and time division duplex (TDD) radio types. TSG RAN specifies not only performance and RF characteristics but also testing for conformance. It is made up of six working groups, including WGs dedicated to radio layer 1 (WG1), radio layers 2 and 3 (WG2), and operations and maintenance (WG3). Core Network and Terminals (TSG CT): Responsible for specifying the core network com- ponents of 3GPP systems, including the signaling interfaces that control factors such as mobil- ity, policy, call connection control, and SO forth. TSG CT also specifies terminal (user equip- ment) characteristics, QoS, and subscriber identity module (SIM) technologies. Service and System Aspects (TSG SA): Responsible for the definition, evolution, and main- tenance of the overall system architecture, including the assignment of functions between vari- ous subsystems. It is made up of six working groups, including one for security. 3GPP technologies have evolved through every generation of the mobile systems. After defining 3G, 3GPP delivered Long-Term Evolution (LTE), LTE-Advanced, LTE-Advanced Pro, and the cur- rent body of work on 5G. 3GPP has become the single technology body that defines technical spe- cifications for global mobile. 3GPP defines the time and frequency synchronization requirements for radio access networks to address various mobility use cases, but it does not 