Roaming Border Control Function for IMS Session Routing
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Solution Overview
Problem
Current IMS roaming solutions face inefficiencies in resource consumption and quality issues due to inefficient routing and independent signaling and media routing, leading to challenges in correlation, security, accounting, and quality assurance across networks during VoIP and Video sessions, especially with legacy CS networks.
Innovation Solution
The implementation of a Roaming Border Control Function (RBCF) within the Visited Public Land Mobile Network (VPLMN) allows for optimized media paths, minimal media gateways, and inter-operator accounting, enabling Local Break Out and seamless handovers between PS and CS functionalities, ensuring correlated signaling and media routing and accounting across networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Home Routing is used to route IMS signalling and user plane from VPLMN via HPLMN, then standard functionalities can be applied to terminate sessions, but resource consumption increases and IP transmission delays increase
Solution Approach 1:
The invention introduces a Border Gateway Function (BGF) as an intermediary entity deployed at the VPLMN side. The BGF receives SIP signalling from the VPLMN's P-CSCF and performs local breakout of the user plane, acting as a mediator that enables the VPLMN to terminate sessions locally while maintaining HPLMN control for service logic. This eliminates the need to route all traffic through the HPLMN, reducing resource consumption and transmission delays while preserving session termination capabilities.
2Productivity
If Local Break Out is used to route user plane directly between VPLMN and target network, then routing efficiency improves, but correlation, security, and accounting problems arise between independent signalling and user plane paths
Solution Approach 1:
The BGF serves as a coordinating intermediary that receives both SIP signalling from the P-CSCF and user plane data from the VPLMN's packet core. It maintains correlation between the signalling and user plane by processing them through a unified local breakout path, ensuring that security policies and accounting information are properly associated. The BGF acts as a single point of control that prevents the dissociation problems that would otherwise occur with independent routing paths.
Solution Approach 2:
The invention merges the handling of SIP signalling and user plane traffic at the BGF, which processes both types of traffic through a unified local breakout mechanism. This consolidation ensures that correlation information, security contexts, and accounting data remain associated throughout the local breakout process, eliminating the fragmentation issues that would arise from completely separate signalling and user plane paths.
3Productivity
If Local Break Out is used, then direct routing between VPLMN and target network is achieved, but accounting between terminating network and other involved networks becomes unclear
Solution Approach 1:
The BGF implements feedback mechanisms by generating and forwarding accounting information to both the VPLMN and HPLMN. It collects accounting data from the local breakout operations and provides feedback reports to the appropriate networks, ensuring that both the terminating network (VPLMN) and the home network (HPLMN) receive accurate accounting information for billing and settlement purposes.
Data Source
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AI summary
The invention relates to a Method for providing a roaming functionality related to an Internet Protocol Multimedia Subsystem (IMS) session, wherein a first User Equipment (UE A) is associated to a Home Public Land Mobile Network (HPLMN) and wherein first the User Equipment (UE A) roams in a Visited Public Land Mobile Network (VPLMN), wherein the Home Public Land Mobile Network (HPLMN) comprises a first Internet Protocol Multimedia Subsystem (IMS) domain, wherein the Visited Public Land Mobile Network (VPLMN) comprises a second Internet Protocol Multimedia Subsystem (IMS) domain, and wherein the Visited Public Land Mobile Network (VPLMN) comprises a Roaming Border Control Function (RBCF), - wherein in case of a session set-up request originating from the first User Equipment (UE A) (mobile originating case) the method comprises the steps of the second Internet Protocol Multimedia Subsystem (IMS) domain transmitting a session set-up request to the first Internet Protocol Multimedia Subsystem (IMS) domain, and the first Internet Protocol Multimedia Subsystem (IMS) domain transmitting a session set-up request to the Roaming Border Control Function (RBCF), and - wherein in case of a session set-up request terminating at the second User Equipment (UE B) (mobile terminating case) the method comprises the steps of the Roaming Border Control Function (RBCF) transmitting a session set-up request to the first Internet Protocol Multimedia Subsystem (IMS) domain, and the first Internet Protocol Multimedia Subsystem (IMS) domain transmiting a session set-up request to the second Internet Protocol Multimedia Subsystem (IMS) domain.