16-11-2012, 11:45 AM
GPRS
[attachment=39733]
Abstract
The General Packet Radio Service (GPRS) is a new non-voice value added service that allows information to be sent and received across a mobile telephone network. It supplements today's Circuit Switched Data and Short Message Service. GPRS is NOT related to GPS (the Global Positioning System), a similar acronym that is often used in mobile contexts. GPRS has several unique features which can be summarized as:
SPEED: Theoretical maximum speeds of up to 171.2 kilobits per second (kbps) are achievable with GPRS using all eight timeslots at the same time. This is about three times as fast as the data transmission speeds possible over today's fixed telecommunications networks and ten times as fast as current Circuit Switched Data services on GSM networks.
IMMEDIACY: GPRS facilitates instant connections whereby information can be sent or received immediately as the need arises, subject to radio coverage. No dial-up modem connection is necessary. This is why GPRS users are sometimes referred to be as being "always connected".
NEW APPLICATIONS, BETTER APPLICATIONS: GPRS facilitates several new applications that have not previously been available over GSM networks due to the limitations in speed of Circuit Switched Data (9.6 kbps) and message length of the Short Message Service (160 characters). GPRS will fully enable the Internet applications you are used to on your desktop from web browsing to chat over the mobile network.
. Introduction
The General Packet Radio Service (GPRS) is a new service that provides actual packet radio access for Global System for Mobile Communications (GSM) and Time-Division Multiple Access (TDMA) users. It provides for the transmission of IP packets over existing cellular networks, bringing the Internet to the mobile phone. Anything the Internet offers, from web browsing to chat and email, will be available from GSM and TDMA service providers via GPRS-enabled devices.
The main benefits of GPRS are that it reserves radio resources only when there is data to send and it reduces reliance on traditional circuit-switched network elements. The increased functionality of GPRS will decrease the incremental cost to provide data services, an occurrence that will, in turn, increase the penetration of data services among consumer and business users. In addition, GPRS will allow improved quality of data services as measured in terms of reliability, response time, and features supported. The unique applications that will be developed with GPRS will appeal to a broad base of mobile subscribers and allow operators to differentiate their services. These new services will increase capacity requirements on the radio and base-station subsystem resources. One method GPRS uses to alleviate the capacity impacts is sharing the same radio resource among all mobile stations in a cell, providing effective use of the scarce resources. In addition, new core network elements will be deployed to support the increased use of data services more efficiently.
GPRS Subscriber Terminals
New terminals (TEs) are required because existing GSM phones do not handle the enhanced air interface, nor do they have the ability to packetize traffic directly. A variety of terminals will exist, including a high-speed version of current phones to support high-speed data access, a new kind of PDA device with an embedded GSM phone, and PC Cards for laptop computers. All these TEs will be backward compatible with GSM for making voice calls using GSM.
GPRS BSS
Each BSC will require the installation of one or more PCUs and a software upgrade. The PCU provides a physical and logical data interface out of the base station system (BSS) for packet data traffic. The BTS may also require a software upgrade, but typically will not require hardware enhancements.
When either voice or data traffic is originated at the subscriber terminal, it is transported over the air interface to the BTS, and from the BTS to the BSC in the same way as a standard GSM call. However, at the output of the BSC the traffic is separated; voice is sent to the mobile switching center (MSC) per standard GSM, and data is sent to a new device called the SGSN, via the PCU over a Frame Relay interface.
GPRS Network
In the core network, the existing MSCs are based upon circuit-switched central-office technology, and they cannot handle packet traffic. Thus two new components, called GPRS Support Nodes, are added:
• Serving GPRS Support Node (SGSN)
• Gateway GPRS Support Node (GGSN)
The SGSN can be viewed as a “packet-switched MSC;” it delivers packets to mobile stations (MSs) within its service area. SGSNs send queries to home location registers (HLRs) to obtain profile data of GPRS subscribers. SGSNs detect new GPRS MSs in a given service area, process registration of new mobile subscribers, and keep a record of their location inside a given area. Therefore, the SGSN performs mobility management functions such as mobile subscriber attach/detach and location management. The SGSN is connected to the base-station subsystem via a Frame Relay connection to the PCU in the BSC.
GPRS Mobility Management
Mobility management within GPRS builds on the mechanisms used in GSM networks; as a MS moves from one area to another, mobility management functions are used to track its location within each mobile network. The SGSNs communicate with each other and update the user location. The MS profiles are preserved in the visitor location registers (VLRs) that are accessible by the SGSNs via the local GSM MSC. A logical link is established and maintained between the MS and the SGSN in each mobile network. At the end of transmission or when a MS moves out of the area of a specific SGSN, the logical link is released and the resources associated with it can be reallocated.
Technology Overview:
GPRS offers the flexibility and throughput of packet switching. At the same time, because it is designed to work on the existing GSM network, it is relatively easy and cost-effective to implement. It uses the same GSM radio frequencies and base stations that are already in place.
How GPRS Works
GPRS uses packet switching to transfer data from the mobile device to the network and back. This provides significant benefits. On a packet-switched network, a device can be always connected and ready to send information without monopolizing the data channel. Channels are shared in packet switched networks, but in circuit-switched networks each channel is dedicated to only one user. Therefore, that user has to pay for the exclusive use of the channel. Another benefit of packet switching is that there are no call setup or suspend delays. The mobile device can begin sending packets immediately whenever it is
used. By overlaying the GSM network, GPRS is able to take advantage of the world's leading digital phone system, with a global subscriber base of over 646.5 million and growing (GSM Association, 01/02). GSM service is available in more than 150 countries and has become the de facto standard in Europe and Asia. It operates on the 900 and 1800 MHz frequency bands in Europe and Asia Pacific and 1900 MHz in North America. In the near future, North American operators will also begin using the 850 MHz frequency band for GSM/GPRS. GPRS improves on the data transmission capability of GSM while using the existing voice transmission capability. Users can have high quality voice conversations using circuit switched data up to 14.4 kbps and transfer data using packet switched GPRS at up to 53.6 kbps (85.6 kbps with advanced wireless networks).
Time Slot Aggregation
Still another benefit of GPRS is the ability to use more time slots, and therefore assign more data packets, into each transmission frame to a particular user. Since GPRS can combine multiple slots in a single transmission, the effective bandwidth is increased. The theoretical limit for GPRS is eight time slots. GPRS assigns a .5-millisecond time slot to each data packet. The system is notified at the time of transmission as to how many time slots or kbps are needed on both the sending and receiving devices. The ability to combine only the required number of time slots for each transmission gives GPRS the flexibility to support both low-speed and high-speed data applications in a single network. Not only does GPRS combine multiple time slots, it also varies the transmission speed of the time slots based on the coding scheme selected.
[attachment=39733]
Abstract
The General Packet Radio Service (GPRS) is a new non-voice value added service that allows information to be sent and received across a mobile telephone network. It supplements today's Circuit Switched Data and Short Message Service. GPRS is NOT related to GPS (the Global Positioning System), a similar acronym that is often used in mobile contexts. GPRS has several unique features which can be summarized as:
SPEED: Theoretical maximum speeds of up to 171.2 kilobits per second (kbps) are achievable with GPRS using all eight timeslots at the same time. This is about three times as fast as the data transmission speeds possible over today's fixed telecommunications networks and ten times as fast as current Circuit Switched Data services on GSM networks.
IMMEDIACY: GPRS facilitates instant connections whereby information can be sent or received immediately as the need arises, subject to radio coverage. No dial-up modem connection is necessary. This is why GPRS users are sometimes referred to be as being "always connected".
NEW APPLICATIONS, BETTER APPLICATIONS: GPRS facilitates several new applications that have not previously been available over GSM networks due to the limitations in speed of Circuit Switched Data (9.6 kbps) and message length of the Short Message Service (160 characters). GPRS will fully enable the Internet applications you are used to on your desktop from web browsing to chat over the mobile network.
. Introduction
The General Packet Radio Service (GPRS) is a new service that provides actual packet radio access for Global System for Mobile Communications (GSM) and Time-Division Multiple Access (TDMA) users. It provides for the transmission of IP packets over existing cellular networks, bringing the Internet to the mobile phone. Anything the Internet offers, from web browsing to chat and email, will be available from GSM and TDMA service providers via GPRS-enabled devices.
The main benefits of GPRS are that it reserves radio resources only when there is data to send and it reduces reliance on traditional circuit-switched network elements. The increased functionality of GPRS will decrease the incremental cost to provide data services, an occurrence that will, in turn, increase the penetration of data services among consumer and business users. In addition, GPRS will allow improved quality of data services as measured in terms of reliability, response time, and features supported. The unique applications that will be developed with GPRS will appeal to a broad base of mobile subscribers and allow operators to differentiate their services. These new services will increase capacity requirements on the radio and base-station subsystem resources. One method GPRS uses to alleviate the capacity impacts is sharing the same radio resource among all mobile stations in a cell, providing effective use of the scarce resources. In addition, new core network elements will be deployed to support the increased use of data services more efficiently.
GPRS Subscriber Terminals
New terminals (TEs) are required because existing GSM phones do not handle the enhanced air interface, nor do they have the ability to packetize traffic directly. A variety of terminals will exist, including a high-speed version of current phones to support high-speed data access, a new kind of PDA device with an embedded GSM phone, and PC Cards for laptop computers. All these TEs will be backward compatible with GSM for making voice calls using GSM.
GPRS BSS
Each BSC will require the installation of one or more PCUs and a software upgrade. The PCU provides a physical and logical data interface out of the base station system (BSS) for packet data traffic. The BTS may also require a software upgrade, but typically will not require hardware enhancements.
When either voice or data traffic is originated at the subscriber terminal, it is transported over the air interface to the BTS, and from the BTS to the BSC in the same way as a standard GSM call. However, at the output of the BSC the traffic is separated; voice is sent to the mobile switching center (MSC) per standard GSM, and data is sent to a new device called the SGSN, via the PCU over a Frame Relay interface.
GPRS Network
In the core network, the existing MSCs are based upon circuit-switched central-office technology, and they cannot handle packet traffic. Thus two new components, called GPRS Support Nodes, are added:
• Serving GPRS Support Node (SGSN)
• Gateway GPRS Support Node (GGSN)
The SGSN can be viewed as a “packet-switched MSC;” it delivers packets to mobile stations (MSs) within its service area. SGSNs send queries to home location registers (HLRs) to obtain profile data of GPRS subscribers. SGSNs detect new GPRS MSs in a given service area, process registration of new mobile subscribers, and keep a record of their location inside a given area. Therefore, the SGSN performs mobility management functions such as mobile subscriber attach/detach and location management. The SGSN is connected to the base-station subsystem via a Frame Relay connection to the PCU in the BSC.
GPRS Mobility Management
Mobility management within GPRS builds on the mechanisms used in GSM networks; as a MS moves from one area to another, mobility management functions are used to track its location within each mobile network. The SGSNs communicate with each other and update the user location. The MS profiles are preserved in the visitor location registers (VLRs) that are accessible by the SGSNs via the local GSM MSC. A logical link is established and maintained between the MS and the SGSN in each mobile network. At the end of transmission or when a MS moves out of the area of a specific SGSN, the logical link is released and the resources associated with it can be reallocated.
Technology Overview:
GPRS offers the flexibility and throughput of packet switching. At the same time, because it is designed to work on the existing GSM network, it is relatively easy and cost-effective to implement. It uses the same GSM radio frequencies and base stations that are already in place.
How GPRS Works
GPRS uses packet switching to transfer data from the mobile device to the network and back. This provides significant benefits. On a packet-switched network, a device can be always connected and ready to send information without monopolizing the data channel. Channels are shared in packet switched networks, but in circuit-switched networks each channel is dedicated to only one user. Therefore, that user has to pay for the exclusive use of the channel. Another benefit of packet switching is that there are no call setup or suspend delays. The mobile device can begin sending packets immediately whenever it is
used. By overlaying the GSM network, GPRS is able to take advantage of the world's leading digital phone system, with a global subscriber base of over 646.5 million and growing (GSM Association, 01/02). GSM service is available in more than 150 countries and has become the de facto standard in Europe and Asia. It operates on the 900 and 1800 MHz frequency bands in Europe and Asia Pacific and 1900 MHz in North America. In the near future, North American operators will also begin using the 850 MHz frequency band for GSM/GPRS. GPRS improves on the data transmission capability of GSM while using the existing voice transmission capability. Users can have high quality voice conversations using circuit switched data up to 14.4 kbps and transfer data using packet switched GPRS at up to 53.6 kbps (85.6 kbps with advanced wireless networks).
Time Slot Aggregation
Still another benefit of GPRS is the ability to use more time slots, and therefore assign more data packets, into each transmission frame to a particular user. Since GPRS can combine multiple slots in a single transmission, the effective bandwidth is increased. The theoretical limit for GPRS is eight time slots. GPRS assigns a .5-millisecond time slot to each data packet. The system is notified at the time of transmission as to how many time slots or kbps are needed on both the sending and receiving devices. The ability to combine only the required number of time slots for each transmission gives GPRS the flexibility to support both low-speed and high-speed data applications in a single network. Not only does GPRS combine multiple time slots, it also varies the transmission speed of the time slots based on the coding scheme selected.