P-CSCF Signalling Session Management for IP-CAN Bearer Loss Detection
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Solution Overview
Problem
The existing IP Multimedia Subsystem (IMS) infrastructure lacks mechanisms to detect and manage loss of signalling bearer transport through an IP Connectivity Access Network (IP-CAN), leading to resource wastage and prolonged waiting times due to repeated requests during bearer failures, especially when no media session is established.
Innovation Solution
The proposed solution involves modifying the Policy and Charging Control (PCC) model to enable the Proxy Call Session Control Function (P-CSCF) and Rules-Control Function Device (RCFD) to establish and manage signalling sessions independently of media sessions, allowing for subscription and notification of bearer-level events for signalling IP flows, thereby detecting and reporting signalling bearer losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the IMS infrastructure uses repeated requests during bearer failures, then service availability is maintained, but resource wastage increases and waiting times are prolonged
Solution Approach 1:
The patent implements a feedback mechanism where the P-CSCF subscribes to bearer status notifications from the PCRF. When bearer transport is lost, the PCRF actively notifies the P-CSCF, which then takes appropriate service continuity actions. This feedback loop replaces blind repeated requests with intelligent, event-driven responses, reducing resource wastage while maintaining service availability.
Solution Approach 2:
The system performs preliminary actions by establishing the PCC architecture and bearer monitoring capabilities before failures occur. The P-CSCF pre-subscribes to bearer status notifications, and the PCRF is pre-configured to detect and report bearer losses. This preparation enables immediate response to failures without needing to repeatedly probe for service availability.
2Measurement precision
If the P-CSCF continuously monitors bearer status without PCC architecture, then bearer failures can be detected, but the system complexity increases and detection capabilities are limited
Solution Approach 1:
The patent introduces the PCRF as an intermediary entity between the bearer transport layer and the P-CSCF. The PCRF monitors bearer status and provides standardized notifications to the P-CSCF through existing PCC interfaces. This intermediary approach enables precise bearer loss detection without requiring the P-CSCF to implement complex monitoring logic, thus maintaining low system complexity while achieving high detection precision.
3Ease of operation
If signalling sessions are managed without independent establishment capability, then media session dependency simplifies control, but signalling session management flexibility is reduced
Solution Approach 1:
The patent segments session management into independent signalling session and media session components. The P-CSCF can establish, modify, and terminate signalling sessions independently of media sessions using the new PCC-based bearer monitoring capabilities. This segmentation provides flexibility to manage signalling sessions separately while maintaining simplified control through the standardized PCC interface for actual bearer monitoring.
Data Source
AI summary
Being aware of a loss of signalling bearer transport through an IP Connectivity Access Network is an important issue. Therefore, the present invention relies on amending the Policing and Charging Control model with means to provide the IMS infrastructure with subscriptions to and notifications about signalling session events detected on the signalling IP flow transported through the bearer layer. To this end, a P-CSCF, or AF included therein, is amended to allow the establishment of a signalling session for subscription to notification of bearer level events for a signalling IP flow. Apart from that, new processing rules are required at the AF and PCRF for handling the signalling session, the notification of events and the termination of the signalling session.