GPRS (General Packet Radio Service) enhances GSM networks by enabling high-speed wireless Internet and data communication. It allocates GSM time slots dynamically, allowing users to transmit data alternately in the same slot. Data is packetized and sent instantly, creating an “always connected” experience for subscribers. GPRS offers more than four times the data speed of conventional GSM systems, making services easily accessible and quick to use.
In GPRS, data rates are significantly higher than traditional GSM. GSM offers a maximum of 9.6 kbps per time slot, while GPRS provides a baseline of 9.05 kbps, with 8 kbps available for users. GPRS employs error correction adaptable to radio channel quality and the possibility of using multiple time slots, with up to all 8 slots theoretically available. Four coding schemes (CS-1 to CS-4) optimize data rates, with a maximum theoretical net rate of 160 kbps. In practice, typical speeds exceed 40 kbit/s, offering improved data transmission capabilities in mobile networks.
GPRS introduces two essential network elements: the Serving GPRS Support Node (SGSN) and the Gateway GPRS Support Node (GGSN). The SGSN manages packet-switched data, including user authentication and tracking, mirroring some MSC functions for voice. Often, SGSN and MSC are colocated. The GGSN serves as the interface between the GSM/GPRS network and external networks and is responsible for IP address allocation.
In GPRS, mobile terminals are categorized into three classes:
- Class A: Capable of concurrently using GPRS for data and circuit-switched services (voice).
- Class B: Can operate either GPRS services or voice service separately but can listen to incoming calls for both GPRS and voice simultaneously.
- Class C: Capable of using either GPRS or circuit-switched services exclusively. It can either handle voice or GPRS and can only listen to one of these services when active.