Description
CAMEL Modified Number (CMN) is a CAMEL service that operates within the Intelligent Network (IN) architecture of GSM/UMTS networks. When a subscriber initiates a call, the CAMEL Service Environment (CSE) intercepts the call setup request and applies logic to modify the destination number based on predefined service logic. This modification occurs before the call is routed through the network, allowing for dynamic number translation without requiring changes to the subscriber's handset or the core switching infrastructure.
The service works through the interaction between the Mobile Switching Center (MSC) and the Service Control Point (SCP) using CAMEL Application Part (CAP) protocol. When a subscriber with CMN service initiates a call, the MSC detects the CAMEL trigger and sends an InitialDP message to the SCP. The SCP then executes service logic that determines the appropriate modified destination number based on factors such as time of day, calling party identity, or service type. The SCP returns a Connect message to the MSC with the modified destination number, which the MSC then uses for call routing.
Key components include the CAMEL Service Environment (CSE) containing the service logic, the Service Control Point (SCP) that executes the logic, and the Mobile Switching Center (MSC) that implements the number modification. The service relies on CAMEL subscription information stored in the Home Location Register (HLR) that indicates which subscribers have CMN capability. The MSC uses this information to trigger CAMEL interactions when these subscribers originate calls.
CMN plays a critical role in enabling advanced telephony services without requiring network-wide infrastructure changes. By centralizing number modification logic in the SCP, operators can deploy services rapidly and manage them centrally. The service supports various business applications including virtual private networks, intelligent routing based on time or location, and integration with external databases for services like number portability.
Purpose & Motivation
CMN was created to address the need for intelligent call routing and number translation services in mobile networks without requiring changes to subscriber handsets or core network switches. Before CAMEL services, number modification required either pre-programmed handsets or complex switch configurations that were difficult to manage and scale. The limitations of these approaches included lack of flexibility, high maintenance costs, and inability to implement centralized service logic.
The historical context for CMN development was the growing demand for intelligent network services in GSM networks during the late 1990s. As mobile operators expanded their service offerings beyond basic voice calls, they needed mechanisms to implement services like freephone numbers, premium rate services, and virtual private networks. Traditional switch-based solutions were vendor-specific and difficult to integrate across multi-vendor networks. CAMEL provided a standardized approach to intelligent network services, with CMN specifically addressing the need for dynamic number modification.
CMN solves the problem of implementing number-based services in a standardized, scalable manner. It enables operators to offer services like number portability (where calls to ported numbers must be redirected to new network destinations), VPN services (where short codes are translated to full numbers), and intelligent routing based on business rules. By centralizing the logic in SCPs, operators can rapidly deploy and modify services without requiring switch upgrades or configuration changes across multiple network elements.
Key Features
- Dynamic number translation during call setup
- Integration with CAMEL Service Environment for centralized logic
- Support for time-based and condition-based routing rules
- Compatibility with existing MSC/HLR infrastructure
- Standardized CAP protocol interface between MSC and SCP
- Subscription-based activation through HLR profile
Evolution Across Releases
Introduced CMN as part of CAMEL Phase 3 capabilities in 3GPP Release 4. Initial architecture included basic number modification functionality with support for destination number replacement during call setup. The service operated through CAP protocol interactions between MSC and SCP, with triggers based on CAMEL subscription data in HLR.
Defining Specifications
| Specification | Title |
|---|---|
| TS 23.079 | 3GPP TS 23.079 |