Evolution from 2G to 3G

2G networks were built mainly for voice data and slow transmission. Due to rapid changes in user expectation, they do not meet today's wireless needs. Evolution from 2G to 3G can be sub-divided into following phases:

• 2G to 2.5G
• 2.5G to 2.75G
• 2.75G to 3G

From 2G to 2.5G (GPRS)

The first major step in the evolution to 3G occurred with the introduction of General Packet Radio Service (GPRS). So the cellular services combined with GPRS became 2.5G.

GPRS could provide data rates from 56 kbit/s up to 114 kbit/s. It can be used for services such as Wireless Application Protocol (WAP) access, Short Message Service (SMS), Multimedia Messaging Service (MMS), and for Internet communication services such as email and World Wide Web access. GPRS data transfer is typically charged per megabyte of traffic transferred, while data communication via traditional circuit switching is billed per minute of connection time, independent of whether the user actually is utilizing the capacity or is in an idle state.

GPRS is a best-effort packet switched service, as opposed to circuit switching, where a certain Quality of Service (QoS) is guaranteed during the connection for non-mobile users. It provides moderate speed data transfer, by using unused Time division multiple access (TDMA) channels. Originally there was some thought to extend GPRS to cover other standards, but instead those networks are being converted to use the GSM standard, so that GSM is and newer releases. It was originally standardized by European Telecommunications Standards Institute (ETSI), but now by the 3rd Generation Partnership Project (3GPP).,.m

From 2.5G to 2.75G

GPRS networks evolved to EDGE networks with the introduction of 8PSK encoding. Enhanced Data rates for GSM Evolution (EDGE), Enhanced GPRS (EGPRS), or IMT Single Carrier (IMT-SC) is a backward-compatible digital mobile phone technology that allows improved data transmission rates, as an extension on top of standard GSM. EDGE can be considered a 3G radio technology and is part of ITU's 3G definition, but is most frequently referred to as 2.75G. EDGE was deployed on GSM networks beginning in 2003—initially by Cingular (now AT&T) in the United States.

EDGE is standardized by 3GPP as part of the GSM family, and it is an upgrade that provides a potential three-fold increase in capacity of GSM/GPRS networks. The specification achieves higher data-rates by switching to more sophisticated methods of coding (8PSK), within existing GSM timeslots.

EDGE can be used for any packet switched application, such as an Internet, video and other multimedia.

From 2.75G to 3G

From EDGE networks the introduction of UMTS networks and technology is called pure 3G. 3G Bandwidth 5 MHz

Migrating from GPRS to UMTS

From GPRS network, the following network elements can be reused:

• Home location register (HLR)
• Visitor location register (VLR)
• Equipment identity register (EIR)
• Mobile switching centre (MSC) (vendor dependent)
• Authentication centre (AUC)
• Serving GPRS Support Node (SGSN) (vendor dependent)
• Gateway GPRS Support Node (GGSN)

From Global Service for Mobile (GSM) communication radio network, the following elements cannot be reused

• Base station controller (BSC)
• Base transceiver station (BTS)

They can remain in the network and be used in dual network operation where 2G and 3G networks co-exist while network migration and new 3G terminals become available for use in the network.

The UMTS network introduces new network elements that function as specified by 3GPP:

• Node B (base station)
• Radio Network Controller (RNC)
• Media Gateway (MGW)

The functionality of MSC and SGSN changes when going to UMTS. In a GSM system the MSC handles all the circuit switched operations like connecting A- and B-subscriber through the network. SGSN handles all the packet switched operations and transfers all the data in the network. In UMTS the Media gateway (MGW) take care of all data transfer in both circuit and packet switched networks. MSC and SGSN control MGW operations. The nodes are renamed to MSC-server and GSN-server.