Customised Applications for Mobile networks Enhanced Logic
Encyclopedia
Customised Applications for Mobile networks Enhanced Logic, or CAMEL (ETSI TS 123 078) for short, is a set of standards designed to work on either a GSM core network
Network Switching Subsystem
Network switching subsystem is the component of a GSM system that carries out call switching and mobility management functions for mobile phones roaming on the network of base stations...

 or UMTS
Universal Mobile Telecommunications System
Universal Mobile Telecommunications System is a third generation mobile cellular technology for networks based on the GSM standard. Developed by the 3GPP , UMTS is a component of the International Telecommunications Union IMT-2000 standard set and compares with the CDMA2000 standard set for...

 network. They allow an operator to define services over and above standard GSM services
GSM services
GSM services are a standard collection of applications and features available to mobile phone subscribers all over the world. The GSM standards are defined by the 3GPP collaboration and implemented in hardware and software by equipment manufacturers and mobile phone operators...

/UMTS services. The CAMEL architecture is based on the Intelligent network
Intelligent network
The Intelligent Network , is the standard network architecture specified in the . It is intended for fixed as well as mobile telecom networks...

 (IN) standards, and uses the CAP
Camel Application Part
The CAMEL Application Part is a signalling protocol used in the Intelligent Network architecture. CAP is a Remote Operations Service Element user protocol, and as such is layered on top of the Transaction Capabilities Application Part of the SS#7 protocol suite...

 protocol.

Many services can be created using CAMEL, and it is particularly effective in allowing these services to be offered when a subscriber is roaming
Roaming
In wireless telecommunications, roaming is a general term referring to the extension of connectivity service in a location that is different from the home location where the service was registered. Roaming ensures that the wireless device is kept connected to the network, without losing the...

, like, for instance, no-prefix dialing (the number the user dials is the same no matter the country where the call is placed) or seamless MMS
Multimedia Messaging Service
Multimedia Messaging Service, or MMS, is a standard way to send messages that include multimedia content to and from mobile phones. It extends the core SMS capability that allowed exchange of text messages only up to 160 characters in length.The most popular use is to send photographs from...

 message access from abroad.

CAMEL entities

  • gsmSCF: GSM Service Control Function
  • gsmSSF: GSM Service Switching Function
  • gsmSRF: GSM Specialized Resource Function
  • gprsSSF: GPRS Service Switching Function

Phases

CAMEL was always intended to be specified in phases. , there have been 4 phases specified, each building on the previous phase. Phases 1 and 2 were defined before 3G
3G
3G or 3rd generation mobile telecommunications is a generation of standards for mobile phones and mobile telecommunication services fulfilling the International Mobile Telecommunications-2000 specifications by the International Telecommunication Union...

 networks were specified, and as such support adding IN services to a GSM
Global System for Mobile Communications
GSM , is a standard set developed by the European Telecommunications Standards Institute to describe technologies for second generation digital cellular networks...

 network, although they are equally applicable to 2.5G and 3G networks. Phase 3 was defined for 3GPP
3GPP
The 3rd Generation Partnership Project is a collaboration between groups of telecommunications associations, known as the Organizational Partners...

 Releases 99 and 4, and hence is a GSM and UMTS
Universal Mobile Telecommunications System
Universal Mobile Telecommunications System is a third generation mobile cellular technology for networks based on the GSM standard. Developed by the 3GPP , UMTS is a component of the International Telecommunications Union IMT-2000 standard set and compares with the CDMA2000 standard set for...

 common specification, while Phase 4 was defined as part of 3GPP Release 5.

In line with other GSM specifications, later phases should be fully backwards compatible with earlier phases; this is achieved by means of the Transaction Capabilities Application Part
Transaction Capabilities Application Part
Transaction Capabilities Application Part, from ITU-T recommendations Q.771-Q.775 or ANSI T1.114 is a protocol for Signalling System 7 networks. Its primary purpose is to facilitate multiple concurrent dialogs between the same sub-systems on the same machines, using Transaction IDs to differentiate...

 (TCAP) Application Context (AC) negotiation procedure, with each CAMEL phase being allocated its own AC version.

Phase 1

CAMEL Phase 1 defined only very basic call control services, but introduced the concept of a CAMEL Basic call state model
Basic call state model
In Intelligent Network and CAMEL switching, a BCSM is a Basic Call State Model-Types:* O-BCSM * T-BCSM A fundamental concept for IN control is the basic call state model . When a call is processed...

 (BCSM) to the Intelligent Network (IN). Phase 1 gave the gsmSCF the ability to bar calls (release the call prior to connection), allow a call to continue unchanged, or to modify a limited number of call parameters before allowing it to continue. The gsmSCF could also monitor the status of a call for certain events (call connection and disconnection), and take appropriate action on being informed of the event.

Phase 1 was defined as part of Release 96 in 1997.

Phase 2

CAMEL Phase 2 enhanced the capabilities defined in Phase 1. In addition to supporting the facilities of Phase 1, Phase 2 included the following:
  • Additional event detection points
  • Interaction between a user and a service using announcements, voice prompting and information collection via in-band interaction or Unstructured Supplementary Service Data (USSD)
    Unstructured Supplementary Service Data
    Unstructured Supplementary Service Data is a protocol used by GSM cellular telephones to communicate with the service provider's computers...

     interaction
  • Control of call duration and transfer of Advice of Charge Information to the mobile station;
  • The ability to inform the gsmSCF about the invocation of the supplementary services Explicit Call Transfer (ECT), Call Deflection (CD) and Multi-Party Calls (MPTY)
  • The ability, for easier post-processing, of integrating charging information from a serving node in normal call records


Phase 2 was defined as part of 3GPP
3GPP
The 3rd Generation Partnership Project is a collaboration between groups of telecommunications associations, known as the Organizational Partners...

 Releases 97 and 98, in 1998, although it is referenced in the stage 1 specification of Release 96.

Phase 3

The third phase of CAMEL enhanced the capabilities of phase 2. The following capabilities were added:
  • Support of facilities to avoid overload
  • Capabilities to support Dialed Services
  • Capabilities to handle mobility events, such as (Not-)reachability and roaming;
  • Control of GPRS sessions and PDP contexts
  • Control of Mobile Originated SMS
    Short message service
    Short Message Service is a text messaging service component of phone, web, or mobile communication systems, using standardized communications protocols that allow the exchange of short text messages between fixed line or mobile phone devices...

     through both circuit-switched and packet-switched serving network entities
  • Interworking with SoLSA (Support of Localised Service Area). Support for this interworking is optional;
  • The gsmSCF can be informed about the invocation of the supplementary service Call Completion to Busy Subscriber (CCBS)


Phase 3 was released as part of 3GPP Releases 99 and 4 in 1999.

Phase 4

The fourth phase of CAMEL built on the capabilities of phase 3. The following features were defined:
  • CAMEL support for Optimal Routing of circuit-switched mobile-to-mobile calls
  • The capability for the gsmSCF to create additional parties in an existing call (Call Party Handling)
  • The capability for the gsmSCF to create a new call unrelated to any other existing call (Call Party Handling - new call)
  • Capabilities for the enhanced handling of call party connections (Call Party Handling)
  • Control of Mobile Terminated SMS
    Short message service
    Short Message Service is a text messaging service component of phone, web, or mobile communication systems, using standardized communications protocols that allow the exchange of short text messages between fixed line or mobile phone devices...

     through both circuit-switched and packet-switched serving network entities
  • The capability for the gsmSCF to control sessions in the IP Multimedia Subsystem (IMS)
    IP Multimedia Subsystem
    The IP Multimedia Subsystem or IP Multimedia Core Network Subsystem is an architectural framework for delivering Internet Protocol multimedia services. It was originally designed by the wireless standards body 3rd Generation Partnership Project , as a part of the vision for evolving mobile...

  • The gsmSCF can request the gsmSSF to play a fixed or a variable sequence of tones


With CAMEL Phase 4, it is possible that only a limited subset of the new functionalities is supported, in addition to the complete support of CAMEL Phase 3.

Phase 4 was released as part of 3GPP
3GPP
The 3rd Generation Partnership Project is a collaboration between groups of telecommunications associations, known as the Organizational Partners...

Release 5 in 2002.
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