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General Packet Radio Service (GPRS), also called2.5G, is amobile data standard on the2Gcellular communication network'sglobal system for mobile communications (GSM).[1] Networks and mobile devices with GPRS started to roll out around the year 2001;[2] it offered, for the first time on GSM networks, seamless data transmission usingpacket data for an "always-on" connection (eliminating the need to "dial-up"),[3] so providing improvedInternet access forweb,email,WAP services,Multimedia Messaging Service (MMS) and others.[4]
Up until the rollout of GPRS, onlycircuit 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.[5] This increased efficiency also gives it theoretical data rates of 56–114 kbit/s,[6] significantly faster than the precedingCircuit Switched Data (CSD) technology. GPRS was succeeded byEDGE ("2.75G") which provided improved performance and speeds on the 2G GSM system.
The GPRS core network allows2G,3G andWCDMAmobile networks to transmitIP packets to external networks such as theInternet. The GPRS system is an integrated part of theGSMnetwork switching subsystem.[7][8][9]
GPRS is abest-effort service, implying variablethroughput andlatency that depend on the number of other users sharing the service concurrently, as opposed tocircuit switching, where a certainquality of service (QoS) is guaranteed during the connection. It uses unusedtime-division multiple access (TDMA) channels in the GSM system for efficiency. Unlike older circuit switching data, GPRS was sold according to the total volume of data transferred instead of time spent online,[10] which is now standard.
GPRS extends the GSM Packet circuit switched data capabilities and makes the following services possible:
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 the ordinary SMS over GSM, whose SMS transmission speed is about 6 to 10 SMS messages per minute.
As the GPRS standard is an extension of GSM capabilities, the service operates on the2G and3Gcellular communication GSM frequencies.[8][11] 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.[11][12][13]
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, 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 ofinternational cellular service frequency assignments
GPRS supports the following protocols:
WhenTCP/IP is used, each phone can have one or moreIP addresses allocated. GPRS will store and forward the IP packets to the phone even duringhandover. The TCP restores any packets lost (e.g. due to a radio noise induced pause).
Devices supporting GPRS are grouped into three classes:
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 thedual 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". Some networks have supported DTM since 2007[citation needed].
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USB 3G/GPRS modems have aterminal-like interface overUSB withV.42bis, andRFC 1144 data formats. Some models include an externalantenna connector. Modem cards for laptop PCs, or external USB modems are available, similar in shape and size to acomputer mouse, or apendrive.
A GPRS connection is established by reference to itsaccess point name (APN). The APN defines the services such aswireless application protocol (WAP)access,short message service (SMS),multimedia messaging service (MMS), and forInternet communication services such asemail andWorld Wide Web access.
In order to set up a GPRS connection for awireless modem, a user must specify an APN, optionally a user name and password, and very rarely anIP address, provided by the network operator.
GSM module or GPRS modules are similar to modems, but there's one difference: the modem is an external piece of equipment, whereas the GSM module or GPRS module can be integrated within an electrical or electronic equipment. It is an embedded piece of hardware. A GSM mobile, on the other hand, is a complete embedded system in itself. It comes with embedded processors dedicated to provide a functional interface between the user and the mobile network.
The upload and download speeds that can be achieved in GPRS depend on a number of factors such as:
Themultiple access methods used in GSM with GPRS are based onfrequency-division duplex (FDD) and TDMA. During a session, a user is assigned to one pair of up-link and down-link frequency channels. This is combined with time domainstatistical multiplexing which makes it possible for several users to share the same frequency channel. Thepackets have constant length, corresponding to a GSM time slot. The down-link usesfirst-come first-served packet scheduling, while the up-link uses a scheme very similar toreservation ALOHA (R-ALOHA). This means thatslotted ALOHA (S-ALOHA) is used for reservation inquiries during a contention phase, and then the actual data is transferred usingdynamic TDMA with first-come first-served.
The channel encoding process in GPRS consists of two steps: first, a cyclic code is used to add parity bits, which are also referred to as the Block Check Sequence, followed by coding with a possibly puncturedconvolutional code.[14] The Coding Schemes CS-1 to CS-4 specify the number of parity bits generated by the cyclic code and the puncturing rate of the convolutional code.[14] In Coding Schemes CS-1 through CS-3, the convolutional code is of rate 1/2, i.e. each input bit is converted into two coded bits.[14] In Coding Schemes CS-2 and CS-3, the output of the convolutional code ispunctured to achieve the desired code rate.[14] In Coding Scheme CS-4, no convolutional coding is applied.[14] The following table summarises the options.
| GPRS Coding scheme | Bitrate including RLC/MAC overhead[a][b] (kbit/s/slot) | Bitrate excluding RLC/MAC overhead[c] (kbit/s/slot) | Modulation | Code rate |
|---|---|---|---|---|
| CS-1 | 9.20 | 8.00 | GMSK | 1/2 |
| CS-2 | 13.55 | 12.00 | GMSK | ≈2/3 |
| CS-3 | 15.75 | 14.40 | GMSK | ≈3/4 |
| CS-4 | 21.55 | 20.00 | GMSK | 1 |
The least robust, but fastest, coding scheme (CS-4) is available near abase transceiver station (BTS), while the most robust coding scheme (CS-1) is used when the mobile station (MS) is further away from a BTS.
Using the CS-4 it is possible to achieve a user speed of 20.0 kbit/s per time slot. However, using this scheme the cell coverage is 25% of normal. CS-1 can achieve a user speed of only 8.0 kbit/s per time slot, but has 98% of normal coverage. Newer network equipment can adapt the transfer speed automatically depending on the mobile location.
In addition to GPRS, there are two other GSM technologies which deliver data services:circuit-switched data (CSD) andhigh-speed circuit-switched data (HSCSD). In contrast to the shared nature of GPRS, these instead establish a dedicated circuit (usually billed per minute). Some applications such asvideo calling may prefer HSCSD, especially when there is a continuous flow of data between the endpoints.
The following table summarises some possible configurations of GPRS and circuit switched data services.
| Technology | Download (kbit/s) | Upload (kbit/s) | TDMA timeslots allocated (DL+UL) |
|---|---|---|---|
| CSD | 9.6 | 9.6 | 1+1 |
| HSCSD | 28.8 | 14.4 | 2+1 |
| HSCSD | 43.2 | 14.4 | 3+1 |
| GPRS | 85.6 | 21.4 (Class 8 & 10 and CS-4) | 4+1 |
| GPRS | 64.2 | 42.8 (Class 10 and CS-4) | 3+2 |
| EGPRS (EDGE) | 236.8 | 59.2 (Class 8, 10 and MCS-9) | 4+1 |
| EGPRS (EDGE) | 177.6 | 118.4 (Class 10 and MCS-9) | 3+2 |
The multislot class determines the speed of data transfer available in theUplink andDownlink directions. It is a value between 1 and 45 which the network uses to allocate radio channels in the uplink and downlink direction. Multislot class with values greater than 31 are referred to as high multislot classes.
A multislot allocation is represented as, for example, 5+2. The first number is the number of downlink timeslots and the second is the number of uplink timeslots allocated for use by the mobile station. A commonly used value is class 10 for many GPRS/EGPRS mobiles which uses a maximum of 4 timeslots in downlink direction and 2 timeslots in uplink direction. However simultaneously a maximum number of 5 simultaneous timeslots can be used in both uplink and downlink. The network will automatically configure for either 3+2 or 4+1 operation depending on the nature of data transfer.
Some high end mobiles, usually also supportingUMTS, also support GPRS/EDGE multislot class 32. According to3GPP TS 45.002 (Release 12), Table B.1,[17] mobile stations of this class support 5 timeslots in downlink and 3 timeslots in uplink with a maximum number of 6 simultaneously used timeslots. If data traffic is concentrated in downlink direction the network will configure the connection for 5+1 operation. When more data is transferred in the uplink the network can at any time change the constellation to 4+2 or 3+3. Under the best reception conditions, i.e. when the best EDGEmodulation and coding scheme can be used, 5 timeslots can carry a bandwidth of 5*59.2 kbit/s = 296 kbit/s. In uplink direction, 3 timeslots can carry a bandwidth of 3*59.2 kbit/s = 177.6 kbit/s.[18]
| Multislot Class | Downlink TS | Uplink TS | Active TS |
|---|---|---|---|
| 1 | 1 | 1 | 2 |
| 2 | 2 | 1 | 3 |
| 3 | 2 | 2 | 3 |
| 4 | 3 | 1 | 4 |
| 5 | 2 | 2 | 4 |
| 6 | 3 | 2 | 4 |
| 7 | 3 | 3 | 4 |
| 8 | 4 | 1 | 5 |
| 9 | 3 | 2 | 5 |
| 10 | 4 | 2 | 5 |
| 11 | 4 | 3 | 5 |
| 12 | 4 | 4 | 5 |
| 30 | 5 | 1 | 6 |
| 31 | 5 | 2 | 6 |
| 32 | 5 | 3 | 6 |
| 33 | 5 | 4 | 6 |
| 34 | 5 | 5 | 6 |
Each multislot class identifies the following:
The different multislot class specification is detailed in the Annex B of the 3GPP Technical Specification 45.002 (Multiplexing and multiple access on the radio path)
The maximum speed of a GPRS connection offered in 2003 was similar to amodem connection in an analog wire telephone network, about 32–40 kbit/s, depending on the phone used.Latency is very high; round-trip time (RTT) is typically about 600–700 ms and often reaches 1s. GPRS is typically prioritized lower than speech, and thus the quality of connection varies greatly.
Devices with latency/RTT improvements (via, for example, the extended UL TBF mode feature) are generally available. Also, network upgrades of features are available with certain operators. With these enhancements the active round-trip time can be reduced, resulting in significant increase in application-level throughput speeds.
GSM was designed for voice, not data. It did not provide direct access to the Internet and it had a limited capacity of 9600 bauds per second.[19] The limitations ofCircuit Switched Data (CSD) also included higher costs. GPRS opened in 2000[20] as a packet-switched data service embedded in the channel-switched cellular radio networkGSM. GPRS extends the reach of the fixed Internet by connecting mobile terminals worldwide.
GPRS was established byEuropean Telecommunications Standards Institute (ETSI) in response to the earlierCDPD andi-mode packet-switched cellular technologies and is integrated into GSM Release 97 and newer releases. It is now maintained by the3rd Generation Partnership Project (3GPP).[21][22]
The CELLPAC[23] protocol developed 1991–1993 was the trigger point for starting in 1993 the specification of standard GPRS by ETSISMG. Especially, the CELLPAC Voice & Data functions introduced in a 1993 ETSI Workshop contribution[24] anticipate what was later known to be the roots of GPRS. This workshop contribution is referenced in 22 GPRS-related US patents.[25] Successor systems to GSM/GPRS like W-CDMA (UMTS) andLTE rely on key GPRS functions for mobile Internet access as introduced by CELLPAC.
According to a study on history of GPRS development,[26]Bernhard Walke and his student Peter Decker are the inventors of GPRS — the first system providing worldwide mobile Internet access.
Enhanced Data rates for GSM Evolution (EDGE), also known as 2.75G and under various other names, is a2G digitalmobile phone technology forpacket switched data transmission. It is a subset ofGeneral Packet Radio Service (GPRS) on theGSM network and improves upon it offering speeds close to3G technology, hence the name 2.75G. EDGE is standardized by the3GPP as part of the GSM family and as an upgrade to GPRS.
EDGE was deployed on GSM networks beginning in 2003 – initially byCingular (nowAT&T) in the United States.[27] It could be readily deployed on existing GSM and GPRS cellular equipment, making it an easier upgrade forcellular companies compared to theUMTS 3G technology that required significant changes.[28] Through the introduction of sophisticated methods of coding and transmitting data, EDGE delivers higher bit-rates per radio channel, resulting in a threefold increase in capacity and performance compared with an ordinary GSM/GPRS connection - originally a max speed of 384 kbit/s.[29] Later, Evolved EDGE was developed as an enhanced standard providing even more reduced latency and more than double performance, with a peak bit-rate of up to 1 Mbit/s.
{{cite web}}: CS1 maint: numeric names: authors list (link){{cite web}}: CS1 maint: numeric names: authors list (link){{cite web}}: CS1 maint: numeric names: authors list (link){{cite web}}: CS1 maint: numeric names: authors list (link){{cite web}}:Missing or empty|title= (help)[dead link]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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