  The second-generation (2G) mobile systems were developed in response to the growing demand for a system that met mobile communication demands while also providing greater interoperability with other systems. International organizations were crucial in the development of a system that would offer better services, be more transparent, and be more interoperable with other networks. The aim of having a single set of standards for networks worldwide was sadly not realized by the 2G network standards. The third generation (3G) was born. It was called the universal terrestrial mobile system (UMTS), which is European telecommunications standards institute (ETSI) driven. IMT-2000 is the international telecommunication union-telecommunication standardization sector (ITU-T) name for the 3G network. Wide-band code division multiple access (WCDMA) is the air interface technology for the UMTS. This platform offers many services that are based on the Internet, along with video calling, imaging, etc. Further advancements to mobile network technology led to long term evolution (LTE), a technology referred to as 4G. The primary goal of LTE was to improve the speed and capacity of mobile networks while lowering latency. As we move to an ALL-IP system, mobile networks' design becomes much simpler. LTE uses orthogonal frequency division multiplexing (OFDM) in its air interface. This paper details all mentioned mobile generations, as well as all the differences between them in terms of hardware and software architectures. 
From 2G to 4G Mobile Network: Architecture and Key Performance   Indicators