computer science

GPRS core network

GPRS core network is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand GPRS core network rather than just read about it. In short: 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 Internet Protocol (IP) or X.25 packets to external networks such as the Internet. The GPRS system is an integrated part of the GSM network switching subsystem.

Key takeaways

GPRS core network belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect GPRS core network to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of GPRS core network from memory before moving on to harder problems.

Reference excerpt

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 Internet Protocol (IP) or X.25 packets to external networks such as the Internet. The GPRS system is an integrated part of the GSM network switching subsystem. The network provides mobility management, session management and transport for IP packet services in GSM and WCDMA networks. The core network also provides support for other functions such as billing and lawful interception. 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 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) 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 that 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 GPRS support node 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 Internet or an X.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 the home agent in Mobile IP. It maintains routing necessary to tunnel the protocol data units (PDUs) to the SGSN that services a particular mobile 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 and address mapping, QoS and PDP context enforcement. With LTE scenario the GGSN functionality moves to SAE 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 and/or UMTS. 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 base station system through the Gb or Iu interface and/or to the UTRAN through the Iu interface. 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) (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 or IP to the packet control unit using the Gb protocol stack Accept uplink data to form IP packets Encrypt downlink data, decrypt uplink data Carry out mobility management to the level of a cell 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 (RNC)

Access point

An access point is:

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with GPRS core network

Start with the simplest possible case. Write down what GPRS core network claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to GPRS core network before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about GPRS core network ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of GPRS core network

In research: GPRS core network appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses GPRS core network in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: GPRS core network is common in secondary-school and first-year university syllabi. It links to neighbouring topics 3GPP standards, Telecommunications infrastructure, so understanding it makes those chapters shorter.
In everyday life: Look for GPRS core network outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study GPRS core network in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what GPRS core network means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain GPRS core network out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is GPRS core network in simple terms?

Why does GPRS core network matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study GPRS core network?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on GPRS core network.