science

GPRS

GPRS is a 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 rather than just read about it. In short: General Packet Radio Service (GPRS), also called 2.5G, is a mobile data standard that is part of the 2G cellular communication network Global System for Mobile Communications (GSM). Networks and mobile devices with GPRS started to roll out around the year 2001; it offered, for the first time on GSM networks, seamless data transmission using packet-switched data for an "always-on" connection, eliminating the need to…

Key takeaways

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

Reference excerpt

General Packet Radio Service (GPRS), also called 2.5G, is a mobile data standard that is part of the 2G cellular communication network Global System for Mobile Communications (GSM). Networks and mobile devices with GPRS started to roll out around the year 2001; it offered, for the first time on GSM networks, seamless data transmission using packet-switched data for an "always-on" connection, eliminating the need to dial up, providing improved Internet access for web, email, Wireless Application Protocol (WAP) services, Short Message Service (SMS), Multimedia Messaging Service (MMS) and others. Up until the rollout of GPRS, only circuit-switched data was used in cellular networks, meaning that one or more radio channels were occupied for the entire duration of a data connection. On the other hand, on GPRS networks, data is broken into small packets and transmitted through available channels. This increased efficiency also gives it theoretical data rates of 56–114 kbit/s, significantly faster than the preceding Circuit Switched Data (CSD) technology. GPRS was succeeded by EDGE ("2.75G") which provided improved performance and speeds on the 2G GSM system.

Technical overview

The GPRS core network allows 2G, 3G and W-CDMA mobile networks to transmit IP packets to external networks such as the Internet. The GPRS system is an integrated part of the GSM network switching subsystem. GPRS is a best-effort service, implying variable throughput and latency that depend on the number of other users sharing the service concurrently, as opposed to circuit switching, where a certain quality of service (QoS) is guaranteed during the connection. It uses unused time-division multiple access (TDMA) channels in the GSM system for efficiency. Unlike older circuit-switched data, GPRS was sold according to the total volume of data transferred instead of time spent online, which is now standard.

Services offered

GPRS extends the GSM Circuit Switched Data capabilities and makes the following services possible:

SMS messaging and broadcasting MMS "Always on" Internet access Push-to-talk over cellular (PoC) Instant messaging and presence—wireless village Internet applications for smart devices through WAP Point-to-point (P2P) service: inter-networking with the Internet (IP) Point-to-multipoint (P2M) service: point-to-multipoint multicast and point-to-multipoint group calls If SMS over GPRS is used, an SMS transmission speed of about 30 SMS messages per minute may be achieved. This is much faster than using SMS over GSM, whose transmission speed is about 6 to 10 messages per minute.

Frequencies As the GPRS standard is an extension of GSM capabilities, the service operates on the 2G and 3G GSM frequencies. GPRS devices can typically use (one or more) of the frequencies within one of the frequency bands the radio supports (850, 900, 1800, 1900 MHz). Depending on the device, location, and intended use, regulations may be imposed either restricting or explicitly specifying authorised frequency bands. GSM-850 and GSM-1900 are used in the United States, Canada, and many other countries in the Americas. GSM-900 and GSM-1800 are used in Europe, the Middle East, Africa and most of Asia. In South Americas these bands are used in Costa Rica (GSM-1800), Brazil (GSM-850, 900 and 1800), Guatemala (GSM-850, GSM-900 and 1900), El Salvador (GSM-850, GSM-900 and 1900). There is a more comprehensive record of international cellular service frequency assignments.

Protocols supported GPRS supports the following protocols:

Internet Protocol (IP). In practice, built-in mobile browsers used IPv4 before IPv6 was widespread. Point-to-Point Protocol (PPP) is typically not supported by mobile phone operators, but if a cellular phone is used as a modem for a connected computer, PPP may be used to tunnel IP to the phone. This allows an IP address to be dynamically assigned to the mobile equipment using IPCP rather than DHCP. X.25 connections are typically used for applications like wireless payment terminals, although it has been removed from the standard. X.25 can still be supported over PPP, or even over IP, but this requires either a network-based router to perform encapsulation or software built into the end-device/terminal (user equipment or UE). When TCP/IP is used, each phone can have one or more IP addresses allocated. GPRS will store and forward the IP packets to the phone even during handover. TCP will retransmit any packets that are lost.

Hardware Devices supporting GPRS are grouped into three classes:

Class A Can be connected to GPRS service and GSM service (voice, SMS) simultaneously. Class B Can be connected to GPRS service and GSM service (voice, SMS), but using only one at a time. During GSM service (voice call or SMS), GPRS service is suspended and resumed automatically after the GSM service (voice call or SMS) has concluded. Most GPRS mobile devices are Class B. Class C Are connected to either GPRS service or GSM service (voice, SMS) and must be switched manually between one service and the other. Because a Class A device must service GPRS and GSM networks together, it effectively needs two radios. To avoid this hardware requirement, a GPRS mobile device may implement the Dual Transfer Mode (DTM) feature. A DTM-capable mobile can handle both GSM packets and GPRS packets with network coordination to ensure both types are not transmitted at the same time. Such devices are considered pseudo-Class A, sometimes referred to as "simple class A".

USB 3G/GPRS modems have a terminal-like interface over USB with V.42bis, and RFC 1144 data formats. Some models include an external antenna connector. Modem cards for laptop PCs, or external USB modems are available, similar in shape and size to a computer mouse, or a pendrive.

Addressing A GPRS connection is established by reference to its Access Point Name (APN). The APN defines the services such as WAP, SMS, MMS, and Internet services such as email and World Wide Web access. In order to set up a GPRS connection for a wireless modem, a user must specify an APN, optionally a user name and password, and very rarely an IP address, provided by the network operator.

Coding schemes and speeds

The upload and download speeds that can be achieved in GPRS depend on a number of factors such as:

the number of BTS TDMA time slots assigned by the operator the channel encoding used. the maximum capability of the mobile device expressed as a GPRS Multislot Class

… excerpt ends here. Continue reading the full article.

Illustrations

GPRS: GPRS sign shown in notification bar of a Samsung Galaxy smartphone — GPRS sign shown in notification bar of a Samsung Galaxy smartphone

Worked examples

Example 1 — a first encounter with GPRS

Start with the simplest possible case. Write down what GPRS claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In 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 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 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

In research: GPRS appears in 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 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 is common in secondary-school and first-year university syllabi. It links to neighbouring topics 3GPP standards, ETSI, Link protocols, so understanding it makes those chapters shorter.
In everyday life: Look for GPRS 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 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what GPRS 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 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is GPRS in simple terms?

Why does GPRS matter?

Because it connects several 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?

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.