Integrating Charging and Rating into the IMS Platform

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Integrating Charging and Rating into the IMS
Platform

• Joe Hogan CTO and Founder Openet Telecom

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Agenda

• Introduction
• Developing and launching services and
  applications quickly and cost effectively
• How can existing OSS systems evolve to IMS
  architecture
• Examining the impact of IMS services on OSS/BSS
  systems
• Real-Time Charging models as a natural towards
  IMS
• Transferring charging information from the IMS
  nodes to the billing system
• Utilizing real-time rating for IMS applications

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Rapid service creation and deployment

• IMS architecture facilitates faster service
  creation and delivery.
• Horizontal service architecture for service
  delivery
• Avoids stovepipe challenges previously associated
  with deploying services
• Improved scalability of service offerings
  (independent of session control and transport)
• Increased control over service lifecycle
• Service transparency

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Evolving to IMS Architecture
3G Charging Architecture From 3GPP (TS 32.240)
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IMS Charging Interface Architecture
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Existing OSS systems evolution

• Critical that investment in OSS systems is
  leveraged.
• Departure from legacy prepaid platforms and
  reliance on vendor defined architectures.
• Progression of rating and intelligence
  capabilities to the network edge.
• Online transaction processing treatment for all
  subscribers irrespective of payment method.
• Flexible Transactionality is at the heart of
  IMS service lifecycle control for service
  creation, aggregation, orchestration, discovery,
  retirement and delivery.

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Impact of IMS services on OSS/BSS systems

• IMS will deliver innovative services that shall
  demand the OSS/BSS system handle complex pricing
  strategies
• Batch based systems fall short of the real-time,
  low latency processing requirements.
• Network edge rating required.
• Support required for standards based input
  interfaces (e.g. Rf, Ro).
• Diameter rich protocol, non trivial to implement
• Interoperability testing critical to success
• Session performance and reliability criteria must
  be met.
• Irrespective of pre and post payment for
  services.
• Much greater volumes of usage data from network
  nodes.
• Increased correlation challenges.

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IMS Online and Offline Charging

• Offline Charging
• Used for post-paid account management.
• Subscriber is billed after the service is
  delivered.
• Customer data records are aggregated and sent to
  the Billing System in real-time or batch.
• The following types of accounting data can be
  sent
• START session accounting
• INTERIM session accounting
• STOP session accounting
• EVENT accounting data.

• Online Charging
• Used for pre-paid account management.
• Subscribers account balance is checked and
  authorisation is received in real-time before a
  service is provided.
• Three types of credit control operation for
  online charging
• Immediate Event Charging (IEC) -
• Event Charging with Unit Reservation (ECUR)
• Session Charging with Unit Reservation (SCUR).

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IMS Event Based Charging

• Manages charging for single events
• Direct Debit
• Service price enquiry
• Balance enquiry
• Refunds
• Offline event-based charging is performed by the
  CCF
• A single CDR is generated for the event which can
  be correlated and sent to the Billing System.
• Online event-based charging is performed by the
  OCS
• Authorisation, credit control and account balance
  management are performed for one or more events.
• Communicates with the rating function to
  determine the value of the requested event.
• Communicates with Credit Control to perform
  credit reservation and account balance
  management.

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Session Based Charging

• Manages the charging of a subscriber session such
  as multimedia gaming, video-conferencing etc.
• Offline session-based charging is performed by
  the CCF.
• CDR(s) are generated for the session and are
  aggregated and correlated before being sent to
  the Billing System.
• Online session-based charging is performed by the
  OCS
• Authorisation, credit control and account balance
  management are performed for the session.
• Communicates with the rating function to
  determine the value of a requested service.
• Communicates with Credit Control to perform
  credit reservation and account balance
  management.
• Graceful service termination supported as
  subscribers account goes to zero.

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Interfaces for Offline Charging
IMS Interface Description
Bi Charging data collection interface between a CCF and a Billing System.
Rf All data communication for offline charging between IMS nodes and the CCF.
Bp Charging data collection interface between a CGF and a Billing System.
Ga Charging data collection interface between a CDR transmitting unit (GGSN/SGSN) and a CDR receiving unit such as a CGF.
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Interfaces for Online Charging
IMS Interface Description
Rb Online Charging Reference Point between Session Charging Function and Correlation Function.
Rc Online Charging Reference Point between Event Charging Function and the Correlation Function.
Re Online Charging Reference Point towards a Rating Function.
Ro Online Charging Reference Point between an Application Server or MRFC and the Event Charging Function.
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Real-Time Charging Models as a natural migration
towards IMS

• Valuable experience gained with existing charging
  models in wireless space e.g. packet switched
  domain.

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Transferring charging information from the IMS
nodes to the billing system

• Charging interfaces from the IMS core
• Session aggregation
• Correlation
• Account balance management
• Distribution

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Charging interfaces from the IMS core

• 3GPP defined Rf interface for offline charging
• Based on Diameter Base Protocol Accounting from
  IETF AAA WG (RFC3588)
• ACR/ACA Messages
• 3GPP AVPs
• 3GPP defined Ro interface for online charging
• Based on Diameter Credit Control Application from
  IETF AAA WG (RFC4006)
• CCR/CCA Messages

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Session aggregation

• Session based aggregation required for offline
  charging to produce P/I/S-CSCF, AS, MRFC, BGCF
  and MGCF CDRs
• Generated from Diameter ACRs (Start, Interim,
  Stop)
• Error handling conditions required

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Correlation
Correlation of IMS usage events is typically
required before sending to BS. Correlation is
possible on multiple levels

• Intra level using ICID key
• Inter level e.g. with the PS domain
• Inter network using the Inter Operator
  Identification (IOI) key

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Account balance management

• For online charging interaction with the
  subscribers balance is required e.g.
• Query balance
• Increment balance
• Decrement balance
• Set balance to value
• Reserve units
• Commit reservation
• Release reservation

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Distribution

• Bi interface loosely defined
• Many different BS vendors most using proprietary
  formats for input
• Typically file based (push/pull)

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Utilizing real-time rating for IMS applications

• 3GPP have defined rating function within the OCS
• 3GPP online charging demands low latency which
  mandates network edge rating
• 3GPP services shall more sophisticated and
  consequently shall require a corresponding level
  of rating complexity and flexibility
• Rating engines shall need to be able to adapt
  rapidly to the constant shifting of offered
  services without dependence on the vendor