The uppermost evolution track shown in Figure is that developed in the 3rd Generation Partnership Project (3GPP), which is currently the dominant standards development group for mobile radio systems and is described in more detail below.
Within the 3GPP evolution track, three multiple access technologies are evident: the ‘Second Generation’ GSM/GPRS/EDGE family1 was based on Time- and Frequency- Division Multiple Access (TDMA/FDMA);
The ‘Third Generation’ UMTS family marked the entry of Code Division Multiple Access (CDMA) into the 3GPP evolution track, becoming known as Wideband CDMA (owing to its 5 MHz carrier bandwidth) or simply WCDMA; finally LTE has adopted Orthogonal Frequency-Division Multiplexing (OFDM), which is the access technology dominating the latest evolutions of all mobile radio standards.
In continuing the technology progression from the GSM and UMTS technology families within 3GPP, the LTE system can be seen as completing the trend of expansion of service provision beyond voice calls towards a multiservice air interface. This was already a key aim of UMTS and GPRS/EDGE, but LTE was designed from the start with the goal of evolving the radio access technology under the assumption that all services would be packet-switched, rather than following the circuit-switched model of earlier systems.
Furthermore, LTE is accompanied by an evolution of the non-radio aspects of the complete system, under the term ‘System Architecture Evolution’ (SAE) which includes the Evolved Packet Core (EPC)network. Together, LTE and SAE comprise the Evolved Packet System (EPS), where boththe core network and the radio access are fully packet-switched.