Phase 1
CAMEL Phase 1 defined only very basic call control services, but introduced the concept of aCAMEL Basic call state model (BCSM) to the Intelligent Network (IN). Phase 1 gave the gsmSCF theability to bar calls (release the call prior to connection), allow a call to continue unchanged, or to modify alimited number of call parameters before allowing it to continue. The gsmSCF could also monitor thestatus of a call for certain events (call connection and disconnection), and take appropriate action onbeing 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 informationcollection via in-band interaction or Unstructured Supplementary Service Data (USSD)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 CallTransfer (ECT), Call Deflection (CD) and Multi-Party Calls (MPTY)
The ability, for easier post-processing, of integrating charging information from a serving node innormal call records
Phase 2 was defined as part of 3GPP Releases 97 and 98, in 1998, although it is referenced in the stage1 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 through both circuit-switched and packet-switched serving networkentities
Interworking with SoLSA (Support of Localised Service Area). Support for this interworking isoptional;
The gsmSCF can be informed about the invocation of the supplementary service Call Completion toBusy 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
