Basic call state model

In Intelligent Network and CAMEL switching, a BCSM is a Basic Call State Model.^[1]

Types

• O-BCSM (Originating BCSM)
• T-BCSM (Terminating BCSM)

A fundamental concept for IN control is the basic call state model (BCSM). When a call is processed by an exchange, the call goes through a number of pre-defined phases. These phases of the call are described in the BCSM. The BCSM generally follows the ISUP signalling of a call

State machine description

In the following IN BCSMs, bold Detection Points and Points In Call are also present in the CAMEL Ph1 subset.

TODO: Expand to Ph2,3,4

O-BCSM

Points in call

• 1. O_Null & Authorize Origination Attempt
• 2. Collect_info (Merged with 1. in CAMEL Ph1)
• 3. Analyze_Info
• 4. Routing & Alerting (Merged with 3. in CAMEL Ph1)
• 5. O_Active
• 6. O_Exception

Detection Points

• 1 Origination_Attempt_Authorized
• 2 Collected_Info
• 3 Analyzed_Info (this is the only Statically armed DP, others are dynamically armed using "Request Report BCSM (RRBE)" message by the SCP)
• 4 Route_Select_Failure
• 5 O_Called_Party_Busy
• 6 O_No_Answer
• 7 O_Answer
• 8 O_Mid_Call
• 9 O_Disconnect
• 10 O_Abandon

T-BCSM

Points in call

• 7. T_Null & Authorize Termination_Attempt
• 8. Select_Facility & Present_Call
• 9. T_Alerting (Merged with 8. in CAMEL Ph1)
• 10. T_Active
• 11. T_Exception

Detection Points

• 12 Termination_Attempt_Authorized
• 13 T_Called_Party_Busy
• 14 T_No_Answer
• 15 T_Answer
• 16 T_Mid_Call
• 17 T_Disconnect
• 18 T_Abandon

Messages

basic INAP call example

• Initial Detection Point (IDP)
• RRB (Request Report BCSM)
• Event Report BCSM (ERB)
• Connect (CONN)
• Continue (CONT)
• Send Charging Information (SCI)
• ACH (Apply Charging)
• ACR (Apply Charging Report)

References