GPRS (General Packet Radio Service) is a non-voice service added to existing TDMA networks, one of the 2.5G technology upgrades. TDMA is the underlying transport mechanism used by GSM networks.
GPRS provides the transmission of IP packets over existing cellular networks.
How does it work?
GPRS is a network overlay to the existing cellular network. It uses the nature of IP transmissions to its advantage. Because IP traffic is made of packets, the network does not need to have continuous data transmission. Thus, IP traffic can easily share the channels. A user may be receiving or transmitting data while another one is reading information. The second user does not need to use the channel during this time, and it makes packet networks more efficient than circuit-switched networks (2G), where the channel would be in use, regardless of the user transmitting or not.