2. Integrating Charging and Rating into the IMS Platform
Joe Hogan CTO and Founder Openet Telecom

3. 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

4. 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

5. Evolving to IMS Architecture
3G Charging Architecture From 3GPP (TS )
Billing Domain
ONLINE
CHARGING
OFFLINE
WLAN
BGCF
MGCF
MRFC
SIP AS
CRF AF
CDF CS - NE
SGSN
CGF
OCS
IMS
GWF P
CSCF I S
Service
GGSN
TPF

6. IMS Charging Interface Architecture

7. 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.

8. 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.

9. IMS Online and Offline Charging
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).
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.

10. 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.

11. 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.

12. 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.

13. 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.

14. 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. Gn Gi
BTS
MSC
SGSN
WAP GW
Cisco CSG
Cisco SESM
Portal
Volubill D2CP
GGSN
Intelligent GGSN
Gaming Server
Music Server
Self-Help Server
UMS Server
Etc.
MMSC
ProQuent MSSP
EDR / RTCU
Cisco SSG
Gn Probe
Netspira
Internet
IMS MFR, MGCF CSCF, etc.
CDR
Charging
Customer and Product
Info
DWH
Fraud
Postpaid Billing
Balance Mgmt System(s)
- Billing System - IN Platform - CRM - Etc
External Rating
- Rating Engine - IN Platform - Billing System - Etc
Rating
G-CDR
EDR
RTCU
S-CDR
- Real-Time Content Usage Events
Key
- Policy Controller
- Policy Enforcers
xDR
- Post Service Delivery Usage Events

15. Transferring charging information from the IMS nodes to the billing system
Charging interfaces from the IMS core
Session aggregation
Correlation
Account balance management
Distribution

16. 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

17. 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

18. 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

19. 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

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

21. 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