Objectives

When you complete the reading in this chapter, you will be able to

• Describe the main architecture of a GPRS network.

• Describe the new components needed to operate a GPRS overlay.

• Understand how the mobility management works.

• Discuss the role of the gateways (signaling, charging, and IP routers).

• Understand the different logical packet channels.

• Describe all the different interfaces in GPRS.

Network Architecture

Support of General Packet Radio Service (GPRS) does not represent a major upgrade to the existing Global Systems for Mobile (GSM) infrastructure. The greatest impact is the addition of two new network elements, which are shown in Figure 3-1.

Figure 3-1: The SGSN and GGSN additions.

• The Serving GPRS Support Node (SGSN)

• The Gateway GPRS Support Node (GGSN)

Functionally, no hardware impact occurs to the Base Transceiver Systems (BTS). Overall, GPRS represents a software upgrade to the Base Station System (BSS), with the exception of the introduction of Packet Control Unit Support Nodes (PCUSN) to support the packet orientation of the G _b interface logically between the Base Station Controller (BSC) and the SGSN.

The architecture of GPRS is designed so that signaling and high-level data protocols are system-independent. Only the low-level protocols in the radio interface must be changed to operate with the same services.

The SGSN can be viewed as a packet-switched Mobile Switching Center (MSC); it delivers packets to mobile stations within its service area.