The General Packet Radio Service (GPRS) is an extension of GSM which allows subscribers to send and receive data over packet-switched connections. The use of GPRS is particularly appropriate for applications with the following characteristics:
• bursty transmission (for which the time between successive transmissions greatly exceeds the average transfer delay);
• frequent transmission of small volumes of data;
• infrequent transmission of large volumes of data.
GPRS Architecture
A GPRS mobile station is categorized according to its capabilities to support simultaneous modes of operation for GSM and GPRS [3GPP-22.060] which are as follows:
• Class A: the mobile station supports simultaneous use of GSM and GPRS services (attachment, activation, monitoring, transmission, etc.). A class A mobile station may establish or receive calls on the two services simultaneously. The high complexity of designing class A devices makes them prohibitively expensive to produce and, therefore, these devices are typically not available for the mass market.
• Class B: the mobile station is attached to both GSM and GPRS services. However, the mobile station can only operate in one of the two services at a time.
• Class C: the mobile station is attached to either the GSM service or the GPRS service but is not attached to both services at the same time. Prior to establishing or receiving a call on one of the two services, the mobile station has to be explicitly attached to the desired service.
Before a mobile station can access GPRS services, it must execute a GPRS attachment procedure to indicate its presence to the network. After its GPRS attachment, the mobile station activates a Packet Data Protocol (PDP) context with the network in order to be able to transmit or receive data. This procedure is called PDP context activation.
Serving GPRS Support Node
The Serving GPRS Support Node (SGSN) is connected to one or more base station subsystems. It operates as a router for data packets for all mobile stations present in a given geographical area. It also keeps track of the location of mobile stations and performs security functions and access control.
Gateway GPRS Support Node
The Gateway GPRS Support Node (GGSN) provides the point of attachment between the GPRS domain and other data networks such as the Internet or corporate networks. An Access Point Name (APN) is used by the mobile user to establish the connection to the required destination network.
• bursty transmission (for which the time between successive transmissions greatly exceeds the average transfer delay);
• frequent transmission of small volumes of data;
• infrequent transmission of large volumes of data.
GPRS Architecture
A GPRS mobile station is categorized according to its capabilities to support simultaneous modes of operation for GSM and GPRS [3GPP-22.060] which are as follows:
• Class A: the mobile station supports simultaneous use of GSM and GPRS services (attachment, activation, monitoring, transmission, etc.). A class A mobile station may establish or receive calls on the two services simultaneously. The high complexity of designing class A devices makes them prohibitively expensive to produce and, therefore, these devices are typically not available for the mass market.
• Class B: the mobile station is attached to both GSM and GPRS services. However, the mobile station can only operate in one of the two services at a time.
• Class C: the mobile station is attached to either the GSM service or the GPRS service but is not attached to both services at the same time. Prior to establishing or receiving a call on one of the two services, the mobile station has to be explicitly attached to the desired service.
Before a mobile station can access GPRS services, it must execute a GPRS attachment procedure to indicate its presence to the network. After its GPRS attachment, the mobile station activates a Packet Data Protocol (PDP) context with the network in order to be able to transmit or receive data. This procedure is called PDP context activation.
Serving GPRS Support Node
The Serving GPRS Support Node (SGSN) is connected to one or more base station subsystems. It operates as a router for data packets for all mobile stations present in a given geographical area. It also keeps track of the location of mobile stations and performs security functions and access control.
Gateway GPRS Support Node
The Gateway GPRS Support Node (GGSN) provides the point of attachment between the GPRS domain and other data networks such as the Internet or corporate networks. An Access Point Name (APN) is used by the mobile user to establish the connection to the required destination network.
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