General Packet Radio Service

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Comparison of the maximum achievable bit rates with different mobile radio standards. ( logarithmic representation )

General Packet Radio Service , abbreviated GPRS (German: "General packet-oriented radio service ") is the name for the service for data transmission in GSM networks. This cell phone network generation was launched worldwide in 2001.

Data transfer

In contrast to the circuit-switched (English circuit switched ) data service CSD is GPRS packet-oriented. This means that the data is converted into individual packets at the sender, transmitted as such and reassembled at the receiver.

Bernhard Walke and Peter Decker are considered to be the inventors of GPRS .

If GPRS is activated, there is only a virtual permanent connection to the remote station (so-called always-on operation ). The radio room is only occupied when data is actually being transmitted, otherwise it is free for other users. Therefore, no radio channel needs to be permanently reserved for a user (as with CSD ). That is why the costs for GPRS connections are usually calculated according to the amount of data transferred and not according to the duration of the connection. Of course, the individual contract conditions are decisive.

Channel bundling

The GPRS technology enables in combining all eight GSM - time slots of a channel in theory, a data transmission rate of 171.2 kilobits per second. In practical operation, however, the number of usable time slots within a frame is limited by the capability of the mobile station ( multislot capability ) and the networks. On the market (as of 2008) there are multislot Class 12 devices with a maximum of four time slots each in the downlink and in the uplink (but at the same time a maximum of 5 time slots). The achievable data transmission rate is - depending on the coding scheme used (depends on the signal and noise ratio) and the number of time slots allocated depending on the network load - up to 53.6 kbps (with 4 time slots and CS-2). This corresponds roughly to the speed of a V.90 telephone modem.

GPRS coding schemes

Coding scheme Data transmission rate
( kbit / s ) per time slot
CS-1 9.05
CS-2 13.4
CS-3 15.6
CS-4 21.4

GPRS terminal classes

There are 3 different classes of end device that indicate the basic capabilities of a device. The device class is indicated with a letter:

  • Class-A: Class A terminals make it possible to use packet-switched and circuit-switched services at the same time. This means that additional data can be transferred during a phone call.
  • Class B: Class B terminals can use either a packet or a circuit-switched service, but not both at the same time. This means that a call can be signaled during data transmission; if this is accepted, no data can be transferred during the call.
  • Class-C: Class C terminals only allow data transmission as long as they are registered with the GPRS service.

GPRS-capable mobile phones mostly belong to device class B. (As of 2008/2009) Some Nokia devices, such as the N900, support class A.

application

Since around the year 2000, many cell phones have supported GPRS, for example for viewing WAP pages. The Multimedia Messaging Service (MMS) is also based on GPRS. Often a computer or handheld can also be connected to a GPRS-capable mobile phone in order to give it full, albeit narrow-band, Internet access. The mobile phone then acts as a modem .

GPRS plug-in card for notebooks

Small GPRS modems are also known as plug-in cards for notebooks.

GPRS is also particularly suitable for telecontrol tasks . As a rule, only a small bandwidth is required here, the transmission speed plays a subordinate role. The greatest advantages of GPRS in the area of ​​telecontrol are the network coverage and the availability of GSM, as well as the lower investment compared to other transmission technologies.

Another application is the location of vehicles and objects, in which GPRS is used for the transmission of position and telemetry data.

The GPRS data network is also used for the push-to-talk mobile service .

Network architecture

Integration of the GPRS (SGSN, GGSN, MMSC) into the GSM cellular network

The packet-switching service GPRS is based on the GSM - mobile network , but requires additional network elements: PCU ( Packet Control Unit ), the SGSN (Serving GPRS Support Node ) and GGSN (Gateway GPRS Support Node) (both of which are explained below).

Interfaces of the GSN (GPRS Support Nodes)

The GSM guidelines as well as WPP3G (the GSM successor to UMTS ) define interfaces between the various network elements. The following list shows the most common interfaces (signaling) and connections (signaling and user data). The largely English terms are taken from the GSM Recommendations set of rules . A translation is not always meaningful.

  • Ga: Interface of the SGSN and GGSN to the charging control function , i.e. the recording of charges
  • Gb: Connection of the SGSN to the BSC , Frame Relay or IP for user data and signaling
  • Gd: Interface of the SGSN to the SMSC ( Short Message Service Center ), is still rarely used
  • Ge: Interface of the SGSN to CAMEL (intelligent network functions)
  • Gi: Connection of the GGSN to the ISP ( Internet Service Provider ) and to company networks ( Corporate Network ), but also to application servers such as MMSC ( Multimedia Messaging Center ), WAP-GW ( Wireless Application Gateway ).
  • Gn: Connection between SGSN and GGSN, mostly ATM or IP ( Internet Protocol ), for user data and signaling
  • Gp: Connection of SGSN to GGSN of other PLMNs ( e.g. for international roaming )
  • Gr: Connection of the SGSN to the HLR (the subscriber data and QoS profiles are located here )
  • Gs: Interface of the SGSN to the MSC , is required for combined network registrations in GPRS network modes 1 and 3
  • Gx and Gy: interfaces of the GGSN to the Charging Control Function (charge recording). These two interfaces are more intended for intelligent services (different fees depending on the application), while the SGSN usually only bills according to the transmission volume.
  • Iu (PS): Connection of the SGSN to the RNC , ATM or IP for user data and signaling
  • LIC: Legal Interception Center (interception of data connections by the state)
  • S3: Interface to the MME in LTE networks (user and signaling data via IP)

SGSN (Serving GPRS Support Node)

The BSC decouples the GPRS packet data and forwards it to the responsible Serving GPRS Support Node (SGSN) via Frame Relay or IP connections. Each SGSN manages the GPRS data traffic for a large number of BSCs. If the Gb interface is routed via IP instead of Frame Relay, a BSC can communicate with a group of SGSN. One then speaks of “SGSN in Pool” or “Gb flex”. This makes the network more fail-safe and the load can be better distributed between the SGSNs.

An SGSN has a similar function for GPRS data communication as an MSC for voice communication. The SGSN organizes the booking in of participants for GPRS services, the change of radio cells and SGSN areas (GPRS Routing Area Update or GPRS Cell Reselection ) and the routing of GPRS data. An SGSN uses the following interfaces for this:

  • Frame relay or IP interfaces to the BSC
  • SS7 and SIGTRAN routes (SS7 over IP) to your own signaling network to B. to manage subscriber data and locations with the help of HLR and to be able to address service nodes of the GSM network.
  • IP routes to other GPRS network elements, such as B. the GGSN to be able to exchange data with the Internet, company networks, WAP servers, etc.
  • IP routes to the GGSNs of foreign networks in order to enable participants from foreign networks who are in their own network ( roaming ) to access GPRS services in their home network.

GGSN (Gateway GPRS Support Node)

The GGSN (Gateway GPRS Support Node) establish the GPRS data connections to network-internal service platforms or to data networks. A GGSN has the following interfaces, all of which are based on IP :

  • Interfaces to the SGSN of the own network
  • Interfaces to the SGSNs of foreign GPRS networks to enable your own subscribers to use the GPRS services from abroad.
  • Interfaces to online billing systems (traffic analyzer, charging gateway) in order to be able to bill GPRS usage in terms of quantity or target-specifically.
  • Interfaces to GPRS service platforms (e.g. WAP server, MMSC )
  • Interfaces to data networks (Internet, company networks)

The GPRS network is accessed via an access point called the Access Point Name (APN). The assignment of APN to a participant takes place via the participant data, which is stored in the HLR. A participant can use several APNs.

See also

literature

  • Martin Sauter: Basic course in mobile communication systems . 3. Edition. Vieweg + Teubner, 2008, ISBN 978-3-8348-0397-9 .
  • Jochen Schiller: Mobile communication . 2nd Edition. Pearson Studies 2003, 2003, ISBN 3-8273-7060-4 .

Individual evidence

  1. ↑ 3GPP TS 24.008: Mobile radio interface Layer 3 specification; Core network protocols; Stage 3; Cape. 1.7.2 General Packet Radio Service (GPRS). (ZIP / DOC; 3.4 MB) September 28, 2009, accessed on December 2, 2009 (English).
  2. ↑ 3GPP TS 23.060: General Packet Radio Service (GPRS); Service description; Stage 2; Cape. 4 main concept. (ZIP / DOC; 5.2 MB) September 29, 2009, accessed on December 2, 2009 (English).
  3. ^ Bernhard Walke: The roots of GPRS: the first system for mobile packet-based global Internet access . Ed .: IEEE Wireless Communications. May 2013, p. 12 ( article online, there p. 1 [PDF; accessed on February 8, 2019]).
  4. ^ Bernhard Walke: The roots of GPRS: the first system for mobile packet-based global Internet access . Ed .: IEEE Wireless Communications. May 2013, p. 12–23 ( article online, there pp. 1–19 [PDF; accessed on February 8, 2019]).
  5. ↑ Peter Decker, Bernhard Walke: A general packet radio service proposed for GSM . In: ETSI SMG Workshop "GSM in a Future Competitive Environment" . Helsinki, Finland October 13, 1993, p. 1–20 ( rwth-aachen.de [PDF; accessed February 8, 2019]).
  6. ↑ General Packet Radio Service (GPRS) (English) - Page at Nuntius ; As of March 12, 2009; (see table under "Channel coding schemes")
  7. ↑ 3GPP TS 23.060: General Packet Radio Service (GPRS); Service description; Stage 2; Cape. 5.4.5: Mobile stations. (ZIP / DOC; 5.2 MB) September 29, 2009, accessed on December 2, 2009 (English).
  8. ↑ Nokia Germany - Nokia N900 - Technical Specifications. January 7, 2010, accessed January 30, 2010 .

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