General Packet Radio Service (GPRS)
GPRS is a packet oriented Mobile Data Service available to users of the 2G cellular communication systems Global System for Mobile Communications (GSM), as well as in the 3G systems. In the 2G systems, GPRS provides data rates from 56 up to 114 kbit/s.
GPRS data transfer is typically charged per megabyte of traffic transferred, while data communication via traditional circuit switching is billed per minute of connection time, independent of whether the user actually is using the capacity or is in an idle state. GPRS is a best-effort packet switched service, as opposed to circuit switching, where a certain Quality of Service (QoS) is guaranteed during the connection for non-mobile users.
2G cellular systems combined with GPRS are often described as "2.5G", that is, a technology between the second (2G) and third (3G) generations of mobile telephony. It provides moderate speed data transfer, by using unused Time division multiple access (TDMA) channels in, for example, the GSM system. Originally there was some thought to extend GPRS to cover other standards, but instead those networks are being converted to use the GSM standard, so that GSM is the only kind of network where GPRS is in use. GPRS is integrated into GSM Release 97 and newer releases. It was originally standardized by European Telecommunications Standards Institute (ETSI), but now by the 3rd Generation Partnership Project (3GPP).
A GPRS connection is established by reference to its Access Point Name (APN). The APN defines the services such as Wireless Application Protocol (WAP) access, Short Message Service (SMS), Multimedia Messaging Service (MMS), and for Internet communication services such as email and World Wide Web access.
Overview of GSM, GPRS, and UMTSGeneral Packet Radio Service
Overview of GSM, GPRS, and UMTSGeneral Packet Radio Service The general packet radio system (GPRS) provides packet radio access for mobile Global System for Mobile Communications (GSM) and time-division multiple access (TDMA) users. In addition to providing new services for today's mobile user, GPRS is important as a migration step toward third-generation (3G) networks. GPRS allows network operators to implement an IP-based core architecture for data applications, which will continue to be used and expanded for 3G services for integrated voice and data applications. The GPRS specifications are written by the European Telecommunications Standard Institute (ETSI), the European counterpart of the American National Standard Institute (ANSI).
GPRS is the first step toward an end-to-end wireless infrastructure and has the following goals:
Open architecture
Consistent IP services
Same infrastructure for different air interfaces
Integrated telephony and Internet infrastructure
Leverage industry investment in IP
Service innovation independent of infrastructure
Benefits of GPRS
The GPRS provides the following benefits:
Overlays on the existing GSM network to provide high-speed data service
Always on, reducing the time spent setting up and taking down connections
Designed to support bursty applications such as e-mail, traffic telematics, telemetry, broadcast services, and web browsing that do not require detected connection.
By implementing Cisco GPRS products and related solutions, mobile service providers can optimize their networks to deploy high quality mobile voice and data services. They can also benefit from new operating efficiencies, peer-to-peer IP-based architecture for scalability, and IP standard interfaces to billing and customer support.
GPRS Applications
GPRS enables a variety of new and unique services to the mobile wireless subscriber. These mobile services have unique characteristics that provide enhanced value to customers. These characteristics include the following:
Mobility—The ability to maintain constant voice and data communications while on the move
Immediacy—Allows subscribers to obtain connectivity when needed, regardless of location and without a lengthy login session
Localization—Allows subscribers to obtain information relevant to their current location
The combination of these characteristics provides a wide spectrum of possible applications that can be offered to mobile subscribers. The core network components offered by Cisco enable seamless access to these applications, whether they reside in the service provider's network or the public Internet.
In general, applications can be separated into two high-level categories: corporate and consumer. These include:
Communications
E-mail; fax; unified messaging; intranet/Internet access
Value-added services—Information services; games
E-commerce—Retail; ticket purchasing; banking; financial trading
Location-based applications—Navigation; traffic conditions; airline/rail schedules; location finder
Vertical applications—Freight delivery; fleet management; sales-force automation
Advertising
Communications Communications applications include those in which it appears to users that they are using the mobile communications network as a pipeline to access messages or information. This differs from those applications in which users believe that they are accessing a service provided or forwarded by the network operator.
Intranet Access
The first stage of enabling users to maintain contact with their offices is through access to e-mail, fax, and voice mail using unified messaging systems. Increasingly, files and data on corporate networks are becoming accessible through corporate intranets. These intranets can be protected through firewalls by enabling secure tunnels or virtual private networks (VPNs).
Internet Access As a critical mass of users is approached, more and more applications aimed at general consumers are being placed on the Internet. The Internet is becoming an effective tool for accessing corporate data and manipulating product and service information. More recently, companies are using the Internet as an environment for conducting business through e-commerce.
Email and Fax
E-mail on mobile networks may take one of two forms. E-mail can be sent to a mobile user directly or the user can have an e-mail account maintained by the network operator or their Internet service provider (ISP). In the latter case, a notification is forwarded to the mobile terminal and includes the first few lines of the e-mail, details of the sender, the date and time, and the subject. Fax attachments can also accompany e-mails.
Unified Messaging
Unified messaging provides a single mailbox for all messages, including voice mail, faxes, e-mail, short message service (SMS), and pager messages. Unified messaging systems allow for a variety of access methods to recover messages of different types. Some use text-to-voice systems to read e-mail or send faxes over a normal phone line. Most allow the user to query the contents of the various mailboxes through data access such as the Internet. Others can be configured to alert the user on the device of their choice when messages are received.
Value Added Services
Value-added services refer to the content provided by network operators to increase the value of services to their subscribers. Two terms that are frequently used to describe delivery of data applications are push and pull, as defined below.
Push describes the transmission of data at a predetermined time or under predetermined conditions. It also refers to the unsolicited supply of advertising (for example, delivery of news as it occurs or stock values when they fall below a preset value).
Pull describes the request for data in real time by the user (for example, checking stock quotes or daily news headlines).
To be valuable to subscribers, this content must possess several characteristics:
Personalized information that is tailored to the user (for example, a stock ticker that focusses on key quotes and news or an e-commerce application that knows a user's profile)
Localized content that is based on a user's current location and includes maps, hotel finders, or restaurant reviews
Menu screens that are intuitive and easy to navigate
Security for e-commerce sites for the exchange of financial or other personal information
Several value-added services are outlined in the following sections.
E-commerce
E-commerce is defined as business conducted on the Internet or data service. This includes applications in which a contract is established for the purchase of goods and services and online banking applications. These applications require user authentication and secure transmission of sensitive data over the data connection.
Banking
The banking industry is interested in promoting electronic banking because electronic transactions are less costly to conduct than personal transactions in a bank. Specific banking functions that can be accomplished over a wireless connection include balance checking, money transfers between accounts, bill payment, and overdraft alert.
Financial Trading
The immediacy of transactions over the Internet and the requirement for up-to-the-minute information has made the purchasing of stocks online a popular application. By coupling push services with the ability to make secure transactions from the mobile terminal, a service that is unique to the mobile environment can be provided.
Location-Based Services and Telematics
Location-based services provide the ability to link push or pull information services with a user's location. Examples include hotel and restaurant finders, roadside assistance, and city-specific news and information. This technology also has vertical applications. These allow, for example, tracking vehicles in a fleet or managing the operations of a large workforce.
Vertical Applications
In the mobile environment, vertical applications apply to systems using mobile architectures to support the specific tasks within a company. Examples of vertical applications include:
Sales support—Configuring stock and product information for sales staff, integrating appointment details, and placing orders remotely
Dispatching—Communicating job details such as location and scheduling and permitting information queries to support the job
Fleet management—Controlling a fleet of delivery or service staff and vehicle, monitoring their locations, and scheduling their work
Parcel delivery—Tracking the locations of packages for customers and monitoring the performance of the delivery system
Advertising
Advertising services are offered as a push information service. Advertising may be offered to customers to subsidize the cost of voice or other information services. Advertising may be location sensitive. For example, a user entering a mall can receive advertisements specific to the stores in that mall.
GPRS Architecture
GPRS is a data network that overlays a second-generation GSM network. This data overlay network provides packet data transport at rates from 9.6 to 171 kbps. Additionally, multiple users can share the same air-interface resources simultaneously.
GPRS attempts to reuse the existing GSM network elements as much as possible, but to effectively build a packet-based mobile cellular network, some new network elements, interfaces, and protocols for handling packet traffic are required. Therefore, GPRS requires modifications to numerous network elements as summarized
More on GPRS & EDGE
GPRS Protocols
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Enhanced Data rates for GSM Evolution (EDGE)
Enhanced Data rates for GSM Evolution (EDGE), Enhanced GPRS (EGPRS), or IMT Single Carrier (IMT-SC) is a backward-compatible digital mobile phone technology that allows improved data transmission rates, as an extension on top of standard GSM. EDGE can be considered a 3G radio technology and is part of ITU's 3G definition,but is most frequently referred to as 2.75G. EDGE was deployed on GSM networks beginning in 2003— initially by Cingular (now AT&T) in the United States.
EDGE is standardized by 3GPP as part of the GSM family, and it is an upgrade that provides a potential three-fold increase in capacity of GSM/GPRS networks. The specification achieves higher data-rates by switching to more sophisticated methods of coding, within existing GSM timeslots. Introducing 8PSK encoding, EDGE is capable of delivering higher bit-rates per radio channel in good conditions.
EDGE can be used for any packet switched application, such as an Internet connection. High-speed data applications such as video services and other multimedia benefit from EGPRS' increased data capacity. EDGE Circuit Switched is a possible future development[citation needed].
Evolved EDGE was added in Release 7 of the 3GPP standard. This is a further extension on top of EDGE, providing reduced latency and potential speeds of 1Mbit/s by using even more complex coding functions than the 8PSK originally introduced with EDGE.
Technology
EDGE/EGPRS is implemented as a bolt-on enhancement for 2G and 2.5G GSM and GPRS networks, making it easier for existing GSM carriers to upgrade to it. EDGE/EGPRS is a superset to GPRS and can function on any network with GPRS deployed on it, provided the carrier implements the necessary upgrade.
Although EDGE requires no hardware or software changes to be made in GSM core networks, base stations must be modified. EDGE compatible transceiver units must be installed and the base station subsystem needs to be upgraded to support EDGE. If the operator already has this in place, which is often the case today, the network can be upgraded to EDGE by activating an optional software feature. Today EDGE is supported by all major chip vendors for GSM. New mobile terminal hardware and software is also required to decode/encode the new modulation and coding schemes and carry the higher user data rates to implement new services.
Transmission techniques
In addition to Gaussian minimum-shift keying (GMSK), EDGE uses higher-order PSK/8 phase shift keying (8PSK) for the upper five of its nine modulation and coding schemes. EDGE produces a 3-bit word for every change in carrier phase. This effectively triples the gross data rate offered by GSM. EDGE, like GPRS, uses a rate adaptation algorithm that adapts the modulation and coding scheme (MCS) according to the quality of the radio channel, and thus the bit rate and robustness of data transmission. It introduces a new technology not found in GPRS, Incremental Redundancy, which, instead of retransmitting disturbed packets, sends more redundancy information to be combined in the receiver. This increases the probability of correct decoding.
EDGE can carry data speeds up to 236.8 kbit/s (with end-to-end latency of less than 150 ms) for 4 timeslots (theoretical maximum is 473.6 kbit/s for 8 timeslots) in packet mode. This means it can handle four times as much traffic as standard GPRS. EDGE will therefore meets the International Telecommunications Union's requirement for a 3G network, and has been accepted by the ITU as part of the IMT-2000 family of 3G standards. It also enhances the circuit data mode called HSCSD, increasing the data rate of this service.
EGPRS modulation and coding scheme (MCS) In good radio conditions, EDGE can be four times as efficient as GSM. GSM use four coding schemes (CS-1 to 4) while EDGE provides nine Modulation and Coding Schemes (MCS-1 to 9).
Coding and modulation
scheme (MCS) Speed
(kbit/s/slot) Modulation MCS-1 8.80 GMSK MCS-2 11.2 GMSK MCS-3 14.8 GMSK MCS-4 17.6 GMSK MCS-5 22.4 8-PSK MCS-6 29.6 8-PSK MCS-7 44.8 8-PSK MCS-8 54.4 8-PSK MCS-9 59.2 8-PSK
Classification EDGE is part of ITU's 3G definition and is considered a 3G radio technology.
EDGE Evolution EDGE Evolution improves on EDGE in a number of ways. Latencies are reduced by lowering the Transmission Time Interval by half (from 20 ms to 10 ms). Bit rates are increased up to 1 MBit/s peak speed and latencies down to 100 ms using dual carriers, higher symbol rate and higher-order modulation (32QAM and 16QAM instead of 8-PSK), and turbo codes to improve error correction. And finally signal quality is improved using dual antennas improving average bit-rates and spectrum efficiency. EDGE Evolution can be gradually introduced as software upgrades, taking advantage of the installed base. With EDGE Evolution, end-users will be able to experience mobile internet connections corresponding to a 500 kbit/s ADSL service.
Networks The Global mobile Suppliers Association (GSA) states that,as of May 2008, there were 313 commercial GSM/EDGE networks in 147 countries, from a total of 363 mobile network operator commitments in 165 countries.
GPRS coding
GPRS offers a number of coding schemes with different levels of error detection and correction. These are used dependent upon the radio frequency signal conditions and the requirements for the data being sent. These are given labels CS-1 to CS-4:
- CS-1: - This applies the highest level of error detection and correction. It is used in scenarios when interference levels are high or signal levels are low. By applying high levels of detection and correction, this prevents the data having to be re-sent too often. Although it is acceptable for many types of data to be delayed, for others there is a more critical time element. This level of detection and coding results in a half code rate, i.e. for every 12 bits that enter the coder, 24 bits result. It results in a throughput of 9.05 kbps actual throughput data rate.
- CS-2: - This error detection and coding scheme is for better channels. It effectively uses a 2/3 encoder and results in a real data throughput of 13.4 kbps which includes the RLC/MAC header etc.
- CS-3: - This effectively uses a 3/4 coder and results in a data throughput of 15.6 kbps.
- CS-4: - This scheme is used when the signal is high and interference levels are low. No correction is applied to the signal allowing for a maximum throughput of 21.4 kbps. If all eight slots were used then this would enable a data throughput of 171.2 kbps to be achieved.
In addition to the error detection and coding schemes, GPRS also employs interleaving techniques to ensure the effects of interference and spurious noise are reduced to a minimum. It allows the error correction techniques to be more effective as interleaving helps reduce the total corruption if a section of data is lost.
As blocks of 20 ms data are carried over four bursts, with a total of 456 bits of information, a total of either 181, 268, 312, or 428 bits of payload data are carried dependent upon the error detection and coding scheme chosen, i.e. from CS-1 to CS-4, respectively.
GPRS classes and coding schemesIn a GPRS
network there are four coding schemes:-
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The choice of coding scheme depends on the condition of the channel provided by the cellular network (quality of the radio link between cell phone and base station). If the channel is very noisy, the network may use CS-1 to ensure higher reliability; in this case the data transfer rate is only 9.05 kbit/s per GSM time slot used. If the channel is providing a good condition, the network could use CS-3 or CS-4 to obtain optimum speed, and would then have up to 21.4 kbit/s per GSM time slot.
The multislot classes are as
follows:-
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