The architecture of mobile networks has gone through a number of evolutionary changes. The changes have happened over the course of the last three decades and during this duration, these networks have transitioned from one generation to another. The first generation systems were analog, circuit switched, and short lived. The second-generation systems, based on digital technology, started to appear in the 1990s and are still in use. The 3G systems were introduced in the early 2000s, while 4G (LTE-Advanced) systems are currently rolling out. The 5G systems, based on ITU-R's IMT-2020 requirements, are in the research and standardization phase and commercialization is expected in the 2020s. It may be noted that all the mobile network architectures consist of four areas, namely radio access network, core network, network operations, and connectivity between these three which is supported through the transport network.