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

Points in call
  • 1. O_Null & Authorize Origination Attempt
  • 2. Collected_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

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)
  • RRBE (Request Report BCSM)
  • Event Report BCSM (ERB)
  • Connect (CON)
  • Continue (CUE)
  • Send Charging Information (SCI)
  • ACH (Apply Charging)
  • ACR (Apply Charging Report)

References
  1. From GSM to LTE: An Introduction to Mobile Networks and Mobile Broadband, p. 58, at Google Books


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