logging in or signing up GPRS Overview- 2G&3G telecom.shooter Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 1417 Category: Science & Tech.. License: All Rights Reserved Like it (3) Dislike it (0) Added: December 24, 2010 This Presentation is Public Favorites: 3 Presentation Description No description available. Comments Posting comment... By: ambuj_kaushal (14 month(s) ago) sir i want to download ur ppt on gprs:2g & 3g pls permit me.......... Saving..... Post Reply Close By: telecom.shooter (14 month(s) ago) apani email.ID send karo Saving..... Edit Comment Close By: swasmi4u (14 month(s) ago) hi plz send me this ppt my email id is swasmi@hotmail.com thanks! Saving..... Post Reply Close Saving..... Edit Comment Close By: dungnt84 (14 month(s) ago) I very like their slides, pls send me its asap via email ntdbk84@gmail.com Many thanks! Saving..... Post Reply Close Saving..... Edit Comment Close By: paramjeet.bhullar (15 month(s) ago) its a good presentation.....pls allow to download Saving..... Post Reply Close Saving..... Edit Comment Close By: nkmj (15 month(s) ago) I like this presentation very much ,so plz mail me on mishranishant59@gmail.co Saving..... Post Reply Close Saving..... Edit Comment Close loading.... See all Premium member Presentation Transcript GPRS- 2G&3G : GPRS- 2G&3G By: Ramesh Chandra ZTE Telecom India Pvt Ltd Performance Department of Network Overview : Overview What is VAS? VAS Services GPRS-an Introduction GPRS Architecture Interfaces Basic Parameters Network Nodes GPRS Support Nodes Logical Channels APN and PDP context Network element Mobility Management Session Management GPRS Attach GPRS Accesing procedure Charging What is VAS? : What is VAS? Value-Added Services (VAS) is a telecommunications industry term for non-core services or, in short, all services beyond standard voice calls and fax transmissions. On a conceptual level, value-added services add value to the standard service offering, spurring the subscriber to use their phone more and allowing the operator to drive up their ARPU (Average revenue per unit) VAS Services : VAS Services Short Message Services GPRS Data Services Multimedia Messaging Missed Call Information Customized Ring-back tone Promotional Messaging Subscription Services Background Music Voice Mail, Chats, SMS etc Roaming replicators, retainers etc Subscription Services -USSD GPRS – An introduction : GPRS – An introduction 1) GPRS functionality basically provides resource-efficient access to external Internet protocol-based(IP) networks. 2) GPRS introduces two new nodes for handling packet traffic: • The Serving GPRS Support node (SGSN) • The Gateway GPRS Support node (GGSN) The implementation of GPRS brings Internet Protocol (IP) capability to the GSM network, enabling connection to a wide range of public and private data networks using industry standard data protocols such as Transmission Control Protocol/Internet Protocol (TCP/IP). The Internet relies exclusively on packet switching. The GPRS system is designed to support intermittent and bursty data transfers as well as transmission of larger volumes of data. When sending packet switched data, a radio channel is occupied only for the duration of the data transmission instead of continuously over a permanent connection, as in circuit-switched technology. This efficiency optimizes network and radio resource usage making GPRS ideal for data applications such as email and Internet access. Slide 6: GPRS provides the following services: Efficient transport of packets in the cellular network Efficient use of scarce radio resources Flexible service, with prepaid or postpaid charging based on content, volume, or session duration Fast setup and access time Simultaneous CS and Packet-Switched (PS) services, which means coexistence without disturbance Connectivity to other external Packet Data Networks (PDNs) using IP GPRS Architecture : GPRS Architecture Interfaces : Interfaces Gn Interface between two GSNs within the same PLMN. Gp Interface between two GSNs in different PLMNs. The Gp interface allows support of GPRS network services across areas served by the co-operating GPRS PLMNs. Gr Interface between an SGSN and an HLR. Um Interface between the mobile station (MS) and the GPRS fixed network part. Gs Interface between an SGSN and an MSC/VLR. Gb Interface between an SGSN and a BSS. Gc Interface between a GGSN and an HLR. Gd Interface between a SMS-GMSC and an SGSN, and between a SMS-IWMSC and an SGSN. Gf Interface between an SGSN and an EIR. Gi Reference point between GPRS and an external packet data network. Basic Parameters : Basic Parameters NSEI – Network Service Entity Identifier To identify each Packet Control Unit to the SGSN Each BSC has only one PCU, so it has only one Network Service Identifier. An SGSN can be connected to several PCUs. Conversely a PCU can only be connected to one SGSN NSVCI - Network Service Virtual Connection Identifier To identify a virtual connection setup between the SGSN and a PCU (in the BSC) Each NSEI consists of various NSVCI (one or more) DLCI - Data Link Connection Identifier It is a unique number to identify a local connection in a Frame Relay network Each DLCI is defined between two Frame Relay Nodes BVCI - BSSGP Virtual Connection Identifier To identify a virtual connection setup between the SGSN and a cell in BSS The BVCI is set by the BSC automatically so only NSVCI and DLCI must be fixed by the command RRNSI Network Nodes : Network Nodes MS TE MT BSS GSM RBS BSC RNS RNC WCDMA RBS MSC/VLR HLR EIR SMS-GMSC/SMS-IWMSC SCP SGSN GGSN CGSN OSS GPRS Support Nodes : GPRS Support Nodes Serving GPRS Support Node (SGSN) Provides Session and Mobility Management (paging, attach, detach, Packet Data Protocol, context handling, intra- and inter-SGSN routing area update). Supports packet services for the GSM and WCDMA Radio Access Network A Dual Access SGSN for both GSM and WCDMA is also available. Gateway GPRS Support Node (GGSN) Provides an interface between mobile radio core networks (GSM and WCDMA) and other packet data networks, such as the Internet, corporate intranets, and private data networks. SGSN : SGSN The Serving GPRS Support Node can be compared to a GSM MSC/VLR. It forwards incoming and outgoing IP packets to and from the MSs attached within the SGSN Service Area. The SGSN also contains a database with visiting GPRS subscriber data. The SGSN provides: Packet routing and transfer towards the MS within the SGSN Service Area Packet routing and transfer towards the GGSN Ciphering and Authentication Handling of Update Procedures (described further in the chapter) Output of billing data Logical link management to the MS Mobility management, that is, support for roaming and handover within and between mobile networks Session management, that is, connection with the MS and GGSN GGSN : GGSN The Gateway GPRS Support Node is responsible for: Packet routing and transfer towards external IP networks Associating subscribers with appropriate SGSN Output of billing data Logical Channels : Logical Channels Packet Common Control Channels PPCH – Packet Paging CHannel (downlink). PRACH – Packet Random Access Channel (uplink) PAGCH – Packet Access Grant CHannel (downlink) PTCCH – Packet Timing advance Control Channel (uplink and downlink). Packet Broadcast Channel PBCCH – Packet Broadcast Control Channel (downlink). Packet Traffic Channels PDTCH – Packet Data Traffic Channel (uplink and downlink). PACCH – Packet Associated Control Channel (uplink and downlink). APN and PDP CONTEXT : APN and PDP CONTEXT ACCESS POINT NAME: When a GPRS mobile phone sets up a PDP context, the access point is selected eg: airtelfun.com.mnc.010.mcc.404.gprs PDP CONTEXT It is a data structure present on both the SGSN and the GGSN which contains the subscriber's session information when the subscriber has an active session. It includes: Subscriber's IP address Subscriber's IMSI,MSISDN Subscriber's Tunnel Endpoint ID (TEID) at the GGSN Tunnel Endpoint ID (TEID) at the SGSN The Tunnel Endpoint ID (TEID) is a number allocated by the GSN which identifies the tunnelled data related to a particular PDP context. Network Elements : Network Elements DNS Domain Name Service which maps logical names to network layer IP addresses. NTP Network Time Protocol server which synchronizes time across all GSN components in the data network. NFS Network File Server which provides long-term storage for network configuration information, charging data information and network statistics. CFG Charging Gateway Function which collects and stores subscriber accounting data for collection by a Billing System (BS). CommHub The CommHub is the backbone of the GSN Complex. It provides routing and switching functions within the GSN, using a Local Area Network (LAN) to interconnect the SGSN and GGSN. In addition, the CommHub provides IP routing within the GPRS backbone (Intranet), Wide Area Network (WAN) interfaces using common backbone technologies such as Frame Relay, and IP security functions such as IP address filtering. OMC-G It controls and monitor the GSN complex. It uses GUI and uses alarms and statistics. APN A reference to the GGSN to be used. In addition, Access Point Name may, in the GGSN,identify the external network. Mobility Management : Mobility Management • Idle : mobile is not registered with the SGSN • Ready : mobile will inform the SGSN of every cell change it can activate a PDP context to communicate with the Internet • Standby : only report change in Routing Area. can still have a PDP context Session Management : Session Management • Creating and handling of PDP context Slide 20: GPRS Attach: MS BSS SGSN HLR 1. Attach Request 2. Security Procedure 3. Security Procedure 4. Update Location 5. Insert Subscriber Data 6. Insert Subscriber Data Ack 7. Update Location ack. Slide 21: MS BSS SGSN DNS GGSN RADIUS PDP Context activation: 1. Activate PDP Context APN 2. DNS Query APN 3 . DNS Response GGSN IP Address 4 . Create PDP Context Request 5.Authentication/accounting request. 6.Authentication/accounting response 7 . Create PDP Context Response IP Address 8. Activate PDP Context Accept IP Address PSTN/ISDN network for dial-up internet access : PSTN/ISDN network for dial-up internet access RADIUS (Remote Authentication Dial In User Server) demand authentication and logon before a user is granted access to the Internet or their email. At this stage, the user may also be given an IP address for use for the duration of the session (Dynamic IP address allocation). In order to access the Internet via a dial-up modem, a user will dial the phone number of their ISP. The call is routed via the ISDN/PSTN fixed line network to the ISP as if it were a normal voice call. SGSN is acting as a user access point and GGSN is acting as a gateway to the ISP. The ISP’s Remote Access Server (RAS) answers the call and begins communication with the user’s modem to negotiate a data transfer speed and other parameters of the session. Once negotiation is completed, a transparent communication pipe is established directly between the user’s computer and the ISP’s network. GPRS Accessing Procedure. : GPRS Accessing Procedure. For accessing any of the GPRS service, MS must be configured for the respective APN. In GPRS attach procedure, SGSN interrogates HLR about MS’s subscription for GPRS services. After this the routing area update procedure registers the MS in SGSN. Now SGSN makes a Logical Link with MS and assign it a TLLI (Temporary Logical Link Identity). After this, the requested is processed in Gn interface, where a DNS determines the GGSN to be contacted for the APN defined for a MCC and MNC. The request ultimately goes to GGSN where MS is given a Gi address whose accounting is done by RADIUS (Remote Authentication Dial-In User Service) Server, after this an APN address is assigned to MS. After this the request goes to Siterouters from where further routing takes place according to type of service requested. Schematic view of Bharti GPRS Network in India. : Schematic view of Bharti GPRS Network in India. Slide 25: Air Interface - Mobile Terminal Type C GPRS only (or manually switched between GPRS and speech modes) Type B GPRS and Speech (not at same time) (Automatically switches between GPRS and speech modes) Type A GPRS and Speech at the same time Charging : Charging PS charging is often primarily amount based instead of time based, that is, the amount of data transmitted over a PDP context is input to the charging system instead of the period the PDP context is active. There are two kinds of charging : 1)Postpaid 2)Prepaid Postpaid Charging : Postpaid Charging Charging Data Records (CDRs), containing information about chargeable events, are transferred from the SGSN or GGSN either directly to a billing system or through a charging gateway. The charging gateway offers functions to prepare GPRS charging information. It can, for example, check and eliminate double CDRs and verify that the CDRs have the right content. In addition, the charging gateway can examine the order of the CDRs and provide the billing system with charging data arranged in sequence. The Ericsson charging gateway product is called Multi Mediation (MM). The billing system handles the billing of the customers, for example, keeping track of the account types and charging agreements. The CDRs used for postpaid charging can be sent over both a file-based output stream using FTP and a near-real-time output stream using GTP Prime (GTP') Hot billing, when the charging data is created immediately after service delivery, also uses CDRs for charging Prepaid Charging : Prepaid Charging The prepaid charging function enables the SCP to have real-time control over subscriber service usage in the SGSN. The charging data is transferred from the SGSN using Customized Applications for Mobile Network Enhanced Logic (CAMEL) and the CAMEL Application Part (CAP) protocol. The GPRS Service Switching Function (gprsSSF) in the SGSN communicates with the GSM Service Control Function (gsmSCF) in the Charging Control Node (CCN). In the Ericsson solution the CCN converts the CAP ptotocol to the SC1+ protocol, which is used to transfer the charging information further to the SCP. The SCP is connected to a server containing information about the prepaid accounts. The CDRs used for prepaid charging can be sent over a near-real-time output stream using GTP'. You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
GPRS Overview- 2G&3G telecom.shooter Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 1417 Category: Science & Tech.. License: All Rights Reserved Like it (3) Dislike it (0) Added: December 24, 2010 This Presentation is Public Favorites: 3 Presentation Description No description available. Comments Posting comment... By: ambuj_kaushal (14 month(s) ago) sir i want to download ur ppt on gprs:2g & 3g pls permit me.......... Saving..... Post Reply Close By: telecom.shooter (14 month(s) ago) apani email.ID send karo Saving..... Edit Comment Close By: swasmi4u (14 month(s) ago) hi plz send me this ppt my email id is swasmi@hotmail.com thanks! Saving..... Post Reply Close Saving..... Edit Comment Close By: dungnt84 (14 month(s) ago) I very like their slides, pls send me its asap via email ntdbk84@gmail.com Many thanks! Saving..... Post Reply Close Saving..... Edit Comment Close By: paramjeet.bhullar (15 month(s) ago) its a good presentation.....pls allow to download Saving..... Post Reply Close Saving..... Edit Comment Close By: nkmj (15 month(s) ago) I like this presentation very much ,so plz mail me on mishranishant59@gmail.co Saving..... Post Reply Close Saving..... Edit Comment Close loading.... See all Premium member Presentation Transcript GPRS- 2G&3G : GPRS- 2G&3G By: Ramesh Chandra ZTE Telecom India Pvt Ltd Performance Department of Network Overview : Overview What is VAS? VAS Services GPRS-an Introduction GPRS Architecture Interfaces Basic Parameters Network Nodes GPRS Support Nodes Logical Channels APN and PDP context Network element Mobility Management Session Management GPRS Attach GPRS Accesing procedure Charging What is VAS? : What is VAS? Value-Added Services (VAS) is a telecommunications industry term for non-core services or, in short, all services beyond standard voice calls and fax transmissions. On a conceptual level, value-added services add value to the standard service offering, spurring the subscriber to use their phone more and allowing the operator to drive up their ARPU (Average revenue per unit) VAS Services : VAS Services Short Message Services GPRS Data Services Multimedia Messaging Missed Call Information Customized Ring-back tone Promotional Messaging Subscription Services Background Music Voice Mail, Chats, SMS etc Roaming replicators, retainers etc Subscription Services -USSD GPRS – An introduction : GPRS – An introduction 1) GPRS functionality basically provides resource-efficient access to external Internet protocol-based(IP) networks. 2) GPRS introduces two new nodes for handling packet traffic: • The Serving GPRS Support node (SGSN) • The Gateway GPRS Support node (GGSN) The implementation of GPRS brings Internet Protocol (IP) capability to the GSM network, enabling connection to a wide range of public and private data networks using industry standard data protocols such as Transmission Control Protocol/Internet Protocol (TCP/IP). The Internet relies exclusively on packet switching. The GPRS system is designed to support intermittent and bursty data transfers as well as transmission of larger volumes of data. When sending packet switched data, a radio channel is occupied only for the duration of the data transmission instead of continuously over a permanent connection, as in circuit-switched technology. This efficiency optimizes network and radio resource usage making GPRS ideal for data applications such as email and Internet access. Slide 6: GPRS provides the following services: Efficient transport of packets in the cellular network Efficient use of scarce radio resources Flexible service, with prepaid or postpaid charging based on content, volume, or session duration Fast setup and access time Simultaneous CS and Packet-Switched (PS) services, which means coexistence without disturbance Connectivity to other external Packet Data Networks (PDNs) using IP GPRS Architecture : GPRS Architecture Interfaces : Interfaces Gn Interface between two GSNs within the same PLMN. Gp Interface between two GSNs in different PLMNs. The Gp interface allows support of GPRS network services across areas served by the co-operating GPRS PLMNs. Gr Interface between an SGSN and an HLR. Um Interface between the mobile station (MS) and the GPRS fixed network part. Gs Interface between an SGSN and an MSC/VLR. Gb Interface between an SGSN and a BSS. Gc Interface between a GGSN and an HLR. Gd Interface between a SMS-GMSC and an SGSN, and between a SMS-IWMSC and an SGSN. Gf Interface between an SGSN and an EIR. Gi Reference point between GPRS and an external packet data network. Basic Parameters : Basic Parameters NSEI – Network Service Entity Identifier To identify each Packet Control Unit to the SGSN Each BSC has only one PCU, so it has only one Network Service Identifier. An SGSN can be connected to several PCUs. Conversely a PCU can only be connected to one SGSN NSVCI - Network Service Virtual Connection Identifier To identify a virtual connection setup between the SGSN and a PCU (in the BSC) Each NSEI consists of various NSVCI (one or more) DLCI - Data Link Connection Identifier It is a unique number to identify a local connection in a Frame Relay network Each DLCI is defined between two Frame Relay Nodes BVCI - BSSGP Virtual Connection Identifier To identify a virtual connection setup between the SGSN and a cell in BSS The BVCI is set by the BSC automatically so only NSVCI and DLCI must be fixed by the command RRNSI Network Nodes : Network Nodes MS TE MT BSS GSM RBS BSC RNS RNC WCDMA RBS MSC/VLR HLR EIR SMS-GMSC/SMS-IWMSC SCP SGSN GGSN CGSN OSS GPRS Support Nodes : GPRS Support Nodes Serving GPRS Support Node (SGSN) Provides Session and Mobility Management (paging, attach, detach, Packet Data Protocol, context handling, intra- and inter-SGSN routing area update). Supports packet services for the GSM and WCDMA Radio Access Network A Dual Access SGSN for both GSM and WCDMA is also available. Gateway GPRS Support Node (GGSN) Provides an interface between mobile radio core networks (GSM and WCDMA) and other packet data networks, such as the Internet, corporate intranets, and private data networks. SGSN : SGSN The Serving GPRS Support Node can be compared to a GSM MSC/VLR. It forwards incoming and outgoing IP packets to and from the MSs attached within the SGSN Service Area. The SGSN also contains a database with visiting GPRS subscriber data. The SGSN provides: Packet routing and transfer towards the MS within the SGSN Service Area Packet routing and transfer towards the GGSN Ciphering and Authentication Handling of Update Procedures (described further in the chapter) Output of billing data Logical link management to the MS Mobility management, that is, support for roaming and handover within and between mobile networks Session management, that is, connection with the MS and GGSN GGSN : GGSN The Gateway GPRS Support Node is responsible for: Packet routing and transfer towards external IP networks Associating subscribers with appropriate SGSN Output of billing data Logical Channels : Logical Channels Packet Common Control Channels PPCH – Packet Paging CHannel (downlink). PRACH – Packet Random Access Channel (uplink) PAGCH – Packet Access Grant CHannel (downlink) PTCCH – Packet Timing advance Control Channel (uplink and downlink). Packet Broadcast Channel PBCCH – Packet Broadcast Control Channel (downlink). Packet Traffic Channels PDTCH – Packet Data Traffic Channel (uplink and downlink). PACCH – Packet Associated Control Channel (uplink and downlink). APN and PDP CONTEXT : APN and PDP CONTEXT ACCESS POINT NAME: When a GPRS mobile phone sets up a PDP context, the access point is selected eg: airtelfun.com.mnc.010.mcc.404.gprs PDP CONTEXT It is a data structure present on both the SGSN and the GGSN which contains the subscriber's session information when the subscriber has an active session. It includes: Subscriber's IP address Subscriber's IMSI,MSISDN Subscriber's Tunnel Endpoint ID (TEID) at the GGSN Tunnel Endpoint ID (TEID) at the SGSN The Tunnel Endpoint ID (TEID) is a number allocated by the GSN which identifies the tunnelled data related to a particular PDP context. Network Elements : Network Elements DNS Domain Name Service which maps logical names to network layer IP addresses. NTP Network Time Protocol server which synchronizes time across all GSN components in the data network. NFS Network File Server which provides long-term storage for network configuration information, charging data information and network statistics. CFG Charging Gateway Function which collects and stores subscriber accounting data for collection by a Billing System (BS). CommHub The CommHub is the backbone of the GSN Complex. It provides routing and switching functions within the GSN, using a Local Area Network (LAN) to interconnect the SGSN and GGSN. In addition, the CommHub provides IP routing within the GPRS backbone (Intranet), Wide Area Network (WAN) interfaces using common backbone technologies such as Frame Relay, and IP security functions such as IP address filtering. OMC-G It controls and monitor the GSN complex. It uses GUI and uses alarms and statistics. APN A reference to the GGSN to be used. In addition, Access Point Name may, in the GGSN,identify the external network. Mobility Management : Mobility Management • Idle : mobile is not registered with the SGSN • Ready : mobile will inform the SGSN of every cell change it can activate a PDP context to communicate with the Internet • Standby : only report change in Routing Area. can still have a PDP context Session Management : Session Management • Creating and handling of PDP context Slide 20: GPRS Attach: MS BSS SGSN HLR 1. Attach Request 2. Security Procedure 3. Security Procedure 4. Update Location 5. Insert Subscriber Data 6. Insert Subscriber Data Ack 7. Update Location ack. Slide 21: MS BSS SGSN DNS GGSN RADIUS PDP Context activation: 1. Activate PDP Context APN 2. DNS Query APN 3 . DNS Response GGSN IP Address 4 . Create PDP Context Request 5.Authentication/accounting request. 6.Authentication/accounting response 7 . Create PDP Context Response IP Address 8. Activate PDP Context Accept IP Address PSTN/ISDN network for dial-up internet access : PSTN/ISDN network for dial-up internet access RADIUS (Remote Authentication Dial In User Server) demand authentication and logon before a user is granted access to the Internet or their email. At this stage, the user may also be given an IP address for use for the duration of the session (Dynamic IP address allocation). In order to access the Internet via a dial-up modem, a user will dial the phone number of their ISP. The call is routed via the ISDN/PSTN fixed line network to the ISP as if it were a normal voice call. SGSN is acting as a user access point and GGSN is acting as a gateway to the ISP. The ISP’s Remote Access Server (RAS) answers the call and begins communication with the user’s modem to negotiate a data transfer speed and other parameters of the session. Once negotiation is completed, a transparent communication pipe is established directly between the user’s computer and the ISP’s network. GPRS Accessing Procedure. : GPRS Accessing Procedure. For accessing any of the GPRS service, MS must be configured for the respective APN. In GPRS attach procedure, SGSN interrogates HLR about MS’s subscription for GPRS services. After this the routing area update procedure registers the MS in SGSN. Now SGSN makes a Logical Link with MS and assign it a TLLI (Temporary Logical Link Identity). After this, the requested is processed in Gn interface, where a DNS determines the GGSN to be contacted for the APN defined for a MCC and MNC. The request ultimately goes to GGSN where MS is given a Gi address whose accounting is done by RADIUS (Remote Authentication Dial-In User Service) Server, after this an APN address is assigned to MS. After this the request goes to Siterouters from where further routing takes place according to type of service requested. Schematic view of Bharti GPRS Network in India. : Schematic view of Bharti GPRS Network in India. Slide 25: Air Interface - Mobile Terminal Type C GPRS only (or manually switched between GPRS and speech modes) Type B GPRS and Speech (not at same time) (Automatically switches between GPRS and speech modes) Type A GPRS and Speech at the same time Charging : Charging PS charging is often primarily amount based instead of time based, that is, the amount of data transmitted over a PDP context is input to the charging system instead of the period the PDP context is active. There are two kinds of charging : 1)Postpaid 2)Prepaid Postpaid Charging : Postpaid Charging Charging Data Records (CDRs), containing information about chargeable events, are transferred from the SGSN or GGSN either directly to a billing system or through a charging gateway. The charging gateway offers functions to prepare GPRS charging information. It can, for example, check and eliminate double CDRs and verify that the CDRs have the right content. In addition, the charging gateway can examine the order of the CDRs and provide the billing system with charging data arranged in sequence. The Ericsson charging gateway product is called Multi Mediation (MM). The billing system handles the billing of the customers, for example, keeping track of the account types and charging agreements. The CDRs used for postpaid charging can be sent over both a file-based output stream using FTP and a near-real-time output stream using GTP Prime (GTP') Hot billing, when the charging data is created immediately after service delivery, also uses CDRs for charging Prepaid Charging : Prepaid Charging The prepaid charging function enables the SCP to have real-time control over subscriber service usage in the SGSN. The charging data is transferred from the SGSN using Customized Applications for Mobile Network Enhanced Logic (CAMEL) and the CAMEL Application Part (CAP) protocol. The GPRS Service Switching Function (gprsSSF) in the SGSN communicates with the GSM Service Control Function (gsmSCF) in the Charging Control Node (CCN). In the Ericsson solution the CCN converts the CAP ptotocol to the SC1+ protocol, which is used to transfer the charging information further to the SCP. The SCP is connected to a server containing information about the prepaid accounts. The CDRs used for prepaid charging can be sent over a near-real-time output stream using GTP'.