The GPRS core network is the central part of the

general packet radio service General Packet Radio Service (GPRS) is a packet oriented mobile data standard on the 2G and 3G cellular communication network's global system for mobile communications (GSM). GPRS was established by European Telecommunications Standards Inst ...

(GPRS) which allows 2G, 3G and

WCDMA The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the Inte ...

mobile networks to transmit IP packets to external networks such as the

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...

. The GPRS system is an integrated part of the

GSM The Global System for Mobile Communications (GSM) is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation ( 2G) digital cellular networks used by mobile devices such as ...

network switching subsystem Network switching subsystem (NSS) (or GSM core network) is the component of a GSM system that carries out call out and mobility management functions for mobile phones roaming on the network of base stations. It is owned and deployed by mobi ...

. The network provides

mobility management Mobility management is one of the major functions of a GSM or a UMTS network that allows mobile phones to work. The aim of mobility management is to track where the subscribers are, allowing calls, SMS and other mobile phone services to be deli ...

session management In computer science and networking in particular, a session is a time-delimited two-way link, a practical (relatively high) layer in the tcp/ip protocol enabling interactive expression and information exchange between two or more communication de ...

and

transport Transport (in British English), or transportation (in American English), is the intentional movement of humans, animals, and goods from one location to another. Modes of transport include air, land (rail and road), water, cable, pipeline, an ...

for Internet Protocol packet services in GSM and WCDMA networks. The core network also provides support for other functions such as billing and

lawful interception Lawful interception (LI) refers to the facilities in telecommunications and telephone networks that allow law enforcement agencies with court orders or other legal authorization to selectively wiretap individual subscribers. Most countries require ...

. It was also proposed, at one stage, to support packet radio services in the US D-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 the 3GPP.

GPRS tunnelling protocol (GTP)

''GPRS Tunnelling Protocol'' is the defining IP-based

protocol Protocol may refer to: Sociology and politics * Protocol (politics), a formal agreement between nation states * Protocol (diplomacy), the etiquette of diplomacy and affairs of state * Etiquette, a code of personal behavior Science and technology ...

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 the Gateway GPRS support node (GGSN). It does this by carrying the subscriber's data from the subscriber's current

serving GPRS support node (SGSN) The GPRS core network is the central part of the general packet radio service (GPRS) which allows 2G, 3G and WCDMA mobile networks to transmit IP packets to external networks such as the Internet. The GPRS system is an integrated part of the ...

to the GGSN which is handling the subscriber's session. Three forms of GTP are used by the GPRS core network. ;GTP-U: for transfer of user data in separated tunnels for each Packet Data Protocol (PDP) context ;GTP-C: for control reasons including: :* setup and deletion of PDP contexts; :* verification of GSN reachability; :* updates; e.g., as subscribers move from one SGSN to another. ;GTP' (pronounced "GTP Prime"): for transfer of charging data to the Charging Gateway Function.

GPRS support nodes (GSN)

A GSN is a network node which supports the use of GPRS in the GSM core network. All GSNs should have a ''Gn'' interface and support the GPRS tunneling protocol. There are two key variants of the GSN, namely Gateway and Serving GPRS support node.

Gateway GPRS support node (GGSN)

The gateway GPRS support node (GGSN) is one of two components of the GPRS PS domain. The GGSN together with the SGSN handle packet transmissions between the GPRS network and external packet switched networks, such as the

or an

X.25 X.25 is an ITU-T standard protocol suite for packet-switched data communication in wide area networks (WAN). It was originally defined by the International Telegraph and Telephone Consultative Committee (CCITT, now ITU-T) in a series of drafts a ...

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 The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the Inte ...

networks. In essence, it carries out the role in GPRS equivalent to the

home agent Mobile IP (or MIP) is an Internet Engineering Task Force (IETF) standard communications protocol that is designed to allow mobile device users to move from one network to another while maintaining a permanent IP address. Mobile IP for IPv4 is desc ...

Mobile IP Mobile IP (or MIP) is an Internet Engineering Task Force (IETF) standard communications protocol that is designed to allow mobile device users to move from one network to another while maintaining a permanent IP address. Mobile IP for IPv4 is descr ...

. It maintains routing necessary to tunnel the

protocol data unit In telecommunications, a protocol data unit (PDU) is a single unit of information transmitted among peer entities of a computer network. It is composed of protocol-specific control information and user data. In the layered architectures of c ...

s (PDUs) to the SGSN that services a particular

mobile station A mobile station (MS) comprises all user equipment and computer software, software needed for communication with a Cellular network, mobile network. The term refers to the global system connected to the mobile network, i.e. a mobile phone or mob ...

(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 and address mapping, QoS and PDP context enforcement. With LTE scenario the GGSN functionality moves to

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gateway (with SGSN functionality working in MME).

Serving GPRS support node (SGSN)

The Serving GPRS Support Node (SGSN) is the node that is serving the MS/ UE. The SGSN supports

GPRS General Packet Radio Service (GPRS) is a packet oriented mobile data standard on the 2G and 3G cellular communication network's global system for mobile communications (GSM). GPRS was established by European Telecommunications Standards Insti ...

and/or

. The SGSN keeps track of the location of an individual MS/ UE and performs security functions and access control. The SGSN is connected to the

GERAN GERAN is an abbreviation for GSM EDGE Radio Access Network. The standards for GERAN are maintained by the 3GPP (Third Generation Partnership Project). GERAN is a key part of GSM, and also of combined UMTS/GSM networks. GERAN is the radio part of ...

base station system through the Gb or Iu interface and/or to the

UTRAN UTRAN (short for "UMTS Terrestrial Radio Access Network''") is a collective term for the network and equipment that connects mobile handsets to the public telephone network or the Internet. It contains the base stations, which are called Node B's ...

through the Iu interface.3GPP TS 23.060 V14.3.0 (2017-03), p.23 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, current VLR) and user profiles (e.g., IMSI, address(es) used in the packet data network) of all GPRS users registered with it.

Common SGSN functions

* Detunnel GTP packets from the GGSN (downlink) * Tunnel IP packets toward the GGSN (uplink) * Carry out mobility management when a standby mode mobile moves from one routing area to another routing area * Billing a user according to data used. * Mobile Equipment Identity Check Procedure (Gf/S13' interfaces). * The SMS GMSCs and SMS IWMSCs support SMS transmission via the SGSN. * The Offline Charging System (OFCS) collects charging records from SGSNs. * The SGSN contains mechanisms for avoiding and handling overload situations. * The SGSN communicate with other SGSN(s) and/or MME(s) (

Mobility Management Entity System Architecture Evolution (SAE) is the core network architecture of mobile communications protocol group 3GPP's LTE wireless communication standard. SAE is the evolution of the GPRS Core Network, but with a simplified architecture; an all-IP ...

) (Gn/S16/S3 interfaces)

GSM/EDGE specific SGSN functions

Enhanced Data Rates for GSM Evolution (EDGE) specific SGSN functions and characteristics are: * Maximum data rate of approx. 60 kbit/s (150 kbit/s for EDGE) per subscriber * Connect via

Frame Relay Frame Relay is a standardized wide area network (WAN) technology that specifies the physical and data link layers of digital telecommunications channels using a packet switching methodology. Originally designed for transport across Integrated Se ...

or IP to the packet control unit using the Gb protocol stack * Accept uplink data to form IP packets * Encrypt down-link data, decrypt up-link data * Carry out mobility management to the level of a

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...

for connected mode mobiles

WCDMA specific SGSN functions

* Carry up to about 42 Mbit/s traffic downlink and 5.8 Mbit/s traffic uplink (HSPA+) * Tunnel/detunnel downlink/uplink packets toward the

radio network controller The Radio Network Controller (RNC) is a governing element in the UMTS radio access network (UTRAN) and is responsible for controlling the Node Bs that are connected to it. The RNC carries out radio resource management, some of the mobility managem ...

(RNC) *

Access point

An access point is: * An IP network to which a mobile set can be connected * A set of settings which are used for that connection * A particular option in a set of settings in a mobile phone When a GPRS mobile phone sets up a PDP context, the access point is selected. At this point an

Access Point Name An Access Point Name (APN) is the name of a gateway between a GSM, GPRS, 3G and 4G mobile network and another computer network, frequently the public Internet. A mobile device making a data connection must be configured with an APN to present t ...

(APN) is determined :Example: aricenttechnologies.mnc012.mcc345.gprs :Example: geocell :Example: internet :Example: hcl.cisco.ggsn This access point is then used in a

DNS The Domain Name System (DNS) is a hierarchical and distributed naming system for computers, services, and other resources in the Internet or other Internet Protocol (IP) networks. It associates various information with domain names assigned to ...

query to a private DNS network. This process (called APN resolution) finally gives the IP address of the GGSN which should serve the access point. At this point a PDP context can be activated.

PDP context

The packet data protocol (PDP; e.g., IP, X.25, FrameRelay) context is a

data structure In computer science, a data structure is a data organization, management, and storage format that is usually chosen for efficient access to data. More precisely, a data structure is a collection of data values, the relationships among them, a ...

present on both the ''serving GPRS support node'' (SGSN) and the ''gateway 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 then ''activate 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 * Subscriber's

IP address An Internet Protocol address (IP address) is a numerical label such as that is connected to a computer network that uses the Internet Protocol for communication.. Updated by . An IP address serves two main functions: network interface ident ...

* Subscriber's IMSI * Subscriber's Tunnel Endpoint ID (TEID) at the GGSN * Subscriber's Tunnel Endpoint ID (TEID) at the SGSN

Reference points and interfaces

Within the GPRS core network standards there are a number of

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s and reference points (logical points of connection which 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.

Interfaces in the GPRS network

;Ga: The interface serves the CDRs (accounting-records) which are written in the GSN and sent to the charging gateway (CG). This interface uses a GTP-based protocol, with modifications that supports CDRs (Called ''GTP' '' and ''GTP prime''). ;Gb: Interface between the

base station subsystem The base station subsystem (BSS) is the section of a traditional cellular telephone network which is responsible for handling traffic and signaling between a mobile phone and the network switching subsystem. The BSS carries out transcoding of s ...

and the SGSN the transmission protocol could be Frame Relay or IP. ;Iu: Interface between the Radio Network Controller and the SGSN. The interface exchanges signaling and payload. ;Gc: Interface between the

GGSN The GPRS core network is the central part of the general packet radio service (GPRS) which allows 2G, 3G and WCDMA mobile networks to transmit IP packets to external networks such as the Internet. The GPRS system is an integrated part of the G ...

and HLR so that the GGSN can get the location details of a

. To avoid implementing MAP/SS7 in the GGSN, this interface is optional. When not present, the GGSN routes inquires to the HLR via an

SGSN The GPRS core network is the central part of the general packet radio service (GPRS) which allows 2G, 3G and WCDMA mobile networks to transmit IP packets to external networks such as the Internet. The GPRS system is an integrated part of the G ...

. ;Gd: Interface between the SGSN and the SMS Gateway. Can use MAP1, MAP2 or MAP3. ;Ge: The interface between the SGSN and the service control point (SCP); uses the

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protocol. ;Gf: The interface between the SGSN and the Equipment Identity Register (EIR), used for checking the mobile's equipment identity number (IMEI) against a list of reported stolen mobile phones. ;Gi: IP based interface between the GGSN and a public data network (PDN) either directly to the

or through a

WAP gateway A WAP gateway sits between mobile devices using the Wireless Application Protocol (WAP) and the World Wide Web, passing pages from one to the other much like a proxy. This translates pages into a form suitable for the mobiles, for instance using the ...

. ;Gmb: The interface between the GGSN and the Broadcast-Multicast Service Center (BM-SC), used for controlling MBMS bearers. ;Gn: IP based interface between SGSN and other SGSNs and (internal) GGSNs.

also shares this interface. Uses the GTP Protocol. ;Gp: IP based interface between internal SGSN and external GGSNs. Between the SGSN and the external GGSN, there is the border gateway (which is essentially a

firewall Firewall may refer to: * Firewall (computing), a technological barrier designed to prevent unauthorized or unwanted communications between computer networks or hosts * Firewall (construction), a barrier inside a building, designed to limit the spre ...

). Also uses the GTP Protocol. ;Gr: Interface between the SGSN and the HLR. Messages going through this interface uses the MAP3 protocol. ;Gs: Interface between the SGSN and the MSC (VLR). Uses the BSSAP+ protocol. This interface allows paging and station availability when it performs data transfer. When the station is attached to the GPRS network, the SGSN keeps track of which routing area (RA) the station is attached to. An RA is a part of a larger location area (LA). When a station is paged this information is used to conserve network resources. When the station performs a PDP context, the SGSN has the exact BTS the station is using. ;Gx: The on-line policy interface between the GGSN and the charging rules function (CRF). It is used for provisioning service data flow based on charging rules. Uses the diameter protocol. ;Gy: The on-line charging interface between the GGSN and the

online charging system Online charging system (OCS) is a system allowing a communications service provider to charge their customers, in real time, based on service usage. Architecture Event based charging An event-based charging function (EBCF) is used to charge event ...

(OCS). Uses the diameter protocol ( DCCA application). ;Gz: The off-line ( CDR-based) charging interface between the GGSN and the Charging system Uses GTP'. ;Lg: The interface between the SGSN and the Gateway Mobile Location Center (

GMLC {{context, date=January 2020 The Gateway Mobile Location Centre (GMLC) contains functionality required to support location-based service (LBS). In one public land mobile network (PLMN), there may be more than one GMLC. The GMLC is the first node a ...

), used for location-based services. ;S3: This interface is defined between the SGSN and the MME and it is used to exchange user and bearer information in inter-system mobility procedures. This interface is implemented using eGTP-C. ;S4: This interface is defined between the SGSN and the SGW (Serving Gateway). The term "S4-SGSN" refers to a Release-8 SGSN that has at least one set of S4/S3/S16 interfaces enabled. ;S6d: The interface between SGSN and Home Subscriber Server (HSS). It is a

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based interface which is used for transferring subscription and authentication data of the user to HSS for authenticating and authorizing user access. ;S13': This interface is defined between the SGSN and the EIR (Equipment Identity Register). The S13' interface applies only to the S4-based SGSN. The interface is based on Diameter protocol. ;S16: This interface is defined between two SGSNs and exclusively uses GTPv2-C.SAE and the Evolved Packet Core: Driving the Mobile Broadband Revolution, p. 237-238

References

External links

3GPP web page including standards

GPRS attach and PDP context activation sequence diagrams

Main Reference

3GPP TS 23.060 V13.4.0 (2015-09)
{{DEFAULTSORT:Gprs Core Network 3GPP standards Telecommunications infrastructure