TheGPRS core network is the central part of thegeneral packet radio service (GPRS) which allows2G,3G andWCDMAmobile networks to transmitInternet Protocol (IP) packets to external networks such as theInternet. The GPRS system is an integrated part of theGSMnetwork switching subsystem.
The network providesmobility management,session management andtransport for IP packet services in GSM and WCDMA networks. The core network also provides support for other functions such asbilling andlawful interception. It was also proposed, at one stage, to support packet radio services in the USD-AMPS TDMA system, however, in practice, all of these networks have been converted to GSM so this option has become irrelevant.
PRS module is an open standards driven system. The standardization body is the3GPP.
GPRS Tunnelling Protocol is the definingIP-basedprotocol of the GPRS core network. Primarily it is the protocol which allows end users of a GSM or WCDMA network to move from place to place while continuing to connect to the Internet as if from one location at theGateway GPRS support node (GGSN). It does this by carrying the subscriber's data from the subscriber's currentserving GPRS support node (SGSN) to the GGSN which is handling the subscriber's session. Three forms of GTP are used by the GPRS core network.
A GSN is a network node that supports the use of GPRS in the GSM core network. All GSNs should have aGn interface and support the GPRS tunneling protocol. There are two key variants of the GSN, namely gateway GPRS support node and serving GPRS support node.
The gateway GPRS support node (GGSN)[1] is one of two components of the GPRS PS domain. The GGSN together with the SGSN handle packet transmissions between the GPRS network and externalpacket-switched networks, such as theInternet or anX.25 network.
From an external network's point of view, the GGSN is a router to a "sub-network", because the GGSN ‘hides’ the GPRS infrastructure from the external network. When the GGSN receives data addressed to a specific user, it checks if the user is active. If it is, the GGSN forwards the data to the SGSN serving the mobile user, but if the mobile user is inactive, the data is discarded. In the other direction, mobile-originated packets are routed to the right network by the GGSN.
The GGSN is the anchor point that enables the mobility of the user terminal in the GPRS/UMTS networks. In essence, it carries out the role in GPRS equivalent to thehome agent inMobile IP. It maintains routing necessary to tunnel theprotocol data units (PDUs) to the SGSN that services a particularmobile station (MS).
The GGSN converts the GPRS packets coming from the SGSN into the appropriate packet data protocol (PDP) format (e.g., IP or X.25) and sends them out on the corresponding packet data network. In the other direction, PDP addresses of incoming data packets are converted to the GSM address of the destination user. The readdressed packets are sent to the responsible SGSN. For this purpose, the GGSN stores the current SGSN address of the user and his or her profile in its location register. The GGSN is responsible for IP address assignment and is the default router for the connected user equipment (UE). The GGSN also performs authentication and charging functions.
Other functions include subscriber screening,IP pool management andaddress mapping,QoS and PDP context enforcement.
WithLTE scenario the GGSN functionality moves toSAE gateway (with SGSN functionality working inMME).
The Serving GPRS Support Node (SGSN)[1] is the node that is serving theMS/UE. The SGSN supportsGPRS and/orUMTS.[2] The SGSN keeps track of the location of an individualMS/UE and performs security functions and access control. The SGSN is connected to theGERAN base station system through the Gb or Iu interface and/or to theUTRAN through the Iu interface.[3]A SGSN is responsible for the delivery of data packets from and to the mobile stations within its geographical service area. Its tasks include packet routing and transfer, mobility management (attach/detach and location management), logical link management, and authentication and charging functions. The location register of the SGSN stores location information (e.g., current cell, currentVLR) and user profiles (e.g.,IMSI, address(es) used in the packet data network) of all GPRS users registered with it.
Enhanced Data Rates for GSM Evolution (EDGE) specific SGSN functions and characteristics are:
An access point is:
When a GPRS mobile phone sets up a PDP context, the access pointis selected. At this point anAccess Point Name (APN) isdetermined
This access point is then used in aDNS query to a private DNSnetwork. This process (called APN resolution) finally gives the IPaddress of the GGSN which should serve the access point. At thispoint a PDP context can be activated.
The packet data protocol (PDP; e.g., IP, X.25, FrameRelay) context is adata structure present on both theserving GPRS support node (SGSN) and thegateway GPRS support node (GGSN) which contains the subscriber's session information when the subscriber has an active session.When a mobile wants to use GPRS, it must first attach and thenactivate a PDP context.This allocates a PDP context data structure in the SGSN that the subscriber is currently visiting and the GGSN serving the subscriber's access point. The data recorded includes
Within the GPRS core network standards, there are a number ofinterfaces and reference points (logical points of connection that probably share a common physical connection with other reference points). Some of these names can be seen in the network structure diagram on this page.
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Cellular network standards | |||||||||
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| 0Gradio telephones (1946) | |||||||||
| 1G (1979) |
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| 2G (1991) |
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| 2G transitional (2.5G, 2.75G, 2.9G) |
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| 3G (1998) IMT-2000 (2001) |
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| 3G transitional (3.5G, 3.75G, 3.9G) |
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| 4G (2009) IMT Advanced (2013) |
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| 5G (2018) IMT-2020 (2021) |
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