The Evolution of Mobile Networks

To date, there have been three distinct generations of mobile cellular networks. The first three generations of mobile networks are conventionally defined by air interfaces and transport technologies. However, it is worth noting that each generation clearly provided an increase in functionality to the mobile user, and could therefore be defined in those terms, rather than in transport technology terms.

• 1G: Basic mobile telephony service
• 2G: Mobile telephony service for mass users with improved ciphering and efficient utilization
• of the radio spectrum
• 2.5G: Mobile Internet services
• 3G: Enhanced 2.5G services plus global roaming, and emerging new applications

The first generation (1G) is based on analog cellular technology, such as the American Mobile Phone Service (AMPS) in the United States and the NTT system in Japan. The second-generation (2G) technology is based on digital cellular technology. Commercially deployed examples of the second generation are the Global System for Mobile Communications (GSM), the North American Version of the CDMA Standard (IS-95) and in Japan, the Personal Digital Cellular (PDC). GSM also provides interregional roaming functionality. Owing to this functionality, GSM continues to show outstanding progress by obtaining 1 billion customers worldwide in 2004.

Packet-switched networks were overlaid onto many of the 2G networks, in the middle of the 2G period. Generally, 2G networks with packet-switched communication systems added are referred to as 2.5G mobile networks.

2.5G mobile networks facilitate instant connections where information can be sent or received almost immediately and without any user activity required to establish a connection. This is why 2.5G mobile devices are commonly referred to be as being always connected or always on.