General Packet Radio Service (GPRS)

Introduction

GPRS, as it reads General Packet Radio Service, was initialized by ETSI/SMG in 1994, to provide end-to-end packet-switched services to mobile users. GPRS was important as a migration step toward third-generation (3G) networks and allows network operators to implement an IP-based core architecture for data applications, which will continue to be used and expanded for 3G services for integrated voice and data applications.

Many Problems Solved 

GPRS enabled a variety of new and unique services to the mobile wireless subscriber. These features include the following:

Mobility: The ability to maintain constant voice and data communications while on the move.

Immediacy: Allowed subscribers to obtain connectivity when needed, regardless of location and without a lengthy login session.

Localization: Allowed subscribers to obtain information relevant to their current location.

GPRS Architecture

GPRS is a data network that overlays a second-generation GSM network. This data overlay network provides packet data transport at rates from 9.6 to 171 kbps. Additionally, multiple users can share the same air-interface resources simultaneously.

Following is the GPRS Architecture diagram:

GPRS Architecture

Following two new components, called GPRS support nodes (GSNs), are added into existing GSM architecture with a few modifications in BSS and BSC:

Gateway GPRS support node (GGSN):
The Gateway GPRS Support Node acts as an interface and a router to external networks. The GGSN contains routing information for GPRS mobiles, which is used to tunnel packets through the IP based internal backbone to the correct Serving GPRS Support Node. The GGSN also collects charging information connected to the use of the external data networks and can act as a packet filter for incoming traffic.

Serving GPRS support node (SGSN):
The Serving GPRS Support Node is responsible for authentication of GPRS mobiles, registration of mobiles in the network, mobility management, and collecting information for charging for the use of the air interface.

GPRS MS Classses

The handset is probably the most well-known piece of equipment, because this is the part we use to make phone calls and to access data services. When we talk about advanced services, the handset is commonly called an MS, which consists of terminal equipment (TE) and a mobile terminal (MT). TE is the device that hosts the applications and the user interaction, while the MT is the part that connects to the network.

In order to take advantage of the new GPRS services, we need new GPRS enabled handsets. There are three different classes of GPRS terminal equipments:

Class A:
Class A terminals can handle packet data and voice at the same time. In other words, we need two transceivers because the handset has to send and/or receive data and voice at the same time. This situation makes class A terminals significantly more expensive to manufacture than class B and C terminals.

Class B:
Class B terminals can handle both packet data and voice, but not at the same time. In other words, you can use the same transceiver for both, keeping the cost of the terminals down.

Class C:
Class C terminals can only handle either voice or data. Examples of class C terminals are GPRS PCM/CIA cards, embedded modules in vending machines, and so on.

Network Processes

This gives a brief description of the basic processes used in GPRS networks:

• Attach process: Process by which the MS attaches (i.e, connects) to the SGSN in a GPRS network

• Authentication process: Process by which the SGSN authenticates the mobile subscriber

• PDP activation process: Process by which a user session is established between the MS and the destination network

• Detach process: Process by which the MS detaches (i.e., disconnects) from the SGSN in the GPRS network

• Network-initiated PDP request for static IP address: Process by which a call from the packet data network reaches the MS using a static IP address

• Network-initiated PDP request for dynamic IP address: Process by which a call from the packet data network reaches the MS using a dynamic IP address 
  

All the latest GSM phones available in the market are enabled to use GPRS services. So if you are planning to buy a GPRS enabled mobile phone then most probably you have to choose one GSM Mobile Phone unless you are using CDMA technology.

GPRS is a crucial step in the mobile evolution, and it opens endless possibilities for application developers and users. In the next article I will talk about UMTS and other 3G technologies.