Internet Access Guide : GPRS

Picture: Internet access over GPRS
One may use a mobile phone, PDA, or notebook to connect to a GPRS network.
A mobile phone can be used as a GPRS modem too by linking it with computer
using Bluetooth, infrared, or serial cable.

General Packet Radio Services or GPRS is an enhancement to GSM or TDMA (IS-95)  network. That's why GPRS is often touted as a 2.5G technology. It uses existing cellular network infrastructure with software upgrade at base stations and the addition of a GPRS Gateway that connects the GPRS network to the Internet.

GPRS as a mobile communication technology between 2G GSM and 3G WCDMA has been serving as data bearer in mobile Internet access as well as other applications, such as machine-to-machine communication. When the faster 3.5G HSDPA networks and the latest 4G LTE networks are being deployed here and there, GPRS still retains its place as a fall-back technology in areas where the higher speed options are unavailable. 

Because GPRS is a packet switched network, a GPRS user station doesn't occupy a dedicated path during an Internet connection. However, each end user station (e.g. mobile phone) is allocated several time slots out of 8 GSM/TDMA available time-slots for GPRS service. Each time slot has a maximum capacity of 14.4 kbps. Depending on how many time slots are allocated for the downlink (from a base station to a user station) and the uplink (from a user station to a base station), GPRS devices are divided into multi-slot classes. A multi-slot class is often represented by the number of downlink and uplink slots. For example, Class 10 is also known as Class 4+2. While active slots indicate the maximum number of slots that can be allocated for both downlink and uplink in a specific class. The following table lists available multi-slot classes.

page 2 : GPRS device classes
page 3 : how to use GPRS