Topics: Mobile phone, GSM, Packet switching Pages: 8 (2146 words) Published: April 25, 2013








What is GPRS?

GSM was the most successful second generation cellular technology, but the need for higher data rates spawned new developments to enable data to be transferred at much higher rates. The first system to make an impact on the market was GPRS. The letters GPRS stand for General Packet Radio System, GPRS technology enabled much higher data rates to be conveyed over a cellular network when compared to GSM that was voice centric. General Packet Radio Service

• General: not restricted to GSM use (DECT?, 3rd generation systems?) • Packet Radio: enables packet mode communication over air • Service, not System: existing BSS (partially also NSS) infrastructure is used GPRS became the first stepping-stone on the path between the second-generation GSM cellular technology and the 3G W-CDMA / UMTS system. With GPRS technology offering data services with data rates up to a maximum of 172 kbps, facilities such as web browsing and other services requiring data transfer became possible. Although some data could be transferred using GSM, the rate was too slow for real data applications. General Packet Radio Service is a radio technology for GSM networks that adds packet-switching protocols, shorter set-up time for ISP connections; it also offers the possibility to charge by amount of data sent rather than connect time.

Key GPRS parameters

The key parameters for the GPRS, General Packet Radio System, are tabulated below: Parameter Specification
Channel Bandwidth 200 kHz
Modulation type GMSK
Data handling Packet data
Max data rate172 kbps

With GPRS providing additional connectivity in terms of packet data, there are naturally a number of upgrades needed to the network architecture required. A number of new elements are needed for the network, but these can operate alongside the existing elements meaning that the GPRS capability is an upgrade to the network and not a completely new network structure. The main new network architecture entities that are needed are: SGSN: GPRS Support Node - this forms a gateway to the services within the network. GGSN: Gateway GPRS Support Node which forms the gateway to the outside world. PCU: Packet Control Unit which differentiates whether data is to be routed to the packet switched or circuit switched networks. A simplified view of the GPRS network architecture can be seen in the diagram below. From this it can be seen that it is very similar to the more basic GSM network architecture, but with additional elements. [pic]


The SGSN or Serving GPRS Support Node element of the GPRS network provides a number of takes focussed on the IP elements of the overall system.There is a location register within the SGSN and this stores location information (e.g., current cell, current VLR). It also stores the user profiles (e.g., IMSI, packet addresses used) for all the GPRS users registered with the particular SGSN.


The GGSN, Gateway GPRS Support Node is one of the most important entities within the GPRS network architecture. The GGSN organizes the interworking between the GPRS network and external packet switched networks to which the mobiles may be connected. These may include both Internet and X.25 networks. The GGSN can be considered to be a combination of a gateway, router and firewall as it hides the internal network to the outside. In operation, when the GGSN receives data addressed to a specific user, it checks if the user is active, then forwarding the data. In the opposite direction, packet data from the mobile is routed to the right destination network by the GGSN.


The PCU or Packet Control Unit is a hardware router that is added to the BSC. It differentiates data...
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