P-CSCF Media Gateway Selection via UPF Geographical Area
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Solution Overview
Problem
Existing methods for selecting media gateways and media resource functions in IP sessions are inefficient, as they rely on UPF IDs selected during IMS registration, which may not reflect the actual UPF instance handling the PDU session, leading to suboptimal voice/video latency and requiring non-scalable reconfiguration of IMS nodes with each UPF instantiation.
Innovation Solution
The proposed solution involves a method where IMS nodes select media gateways and media resource functions based on the geographical service area associated with the current UPF instance, using a Network Repository Function to register and store UPF profiles with tracking area identifiers, allowing for dynamic selection and minimizing the impact on legacy protocols and control plane functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If UPF ID is used to select media gateway or media resource function, then the selection can be made at IMS registration, but the selected UPF instance may not be the actual one handling the PDU session when voice/video call is initiated, leading to suboptimal latency
Solution Approach 1:
The UPF geographical service area information is obtained and stored in advance during PDU session establishment, before the voice/video call is initiated. This preliminary action ensures that when the call is initiated, the correct UPF instance is already identified, eliminating the timing mismatch and ensuring optimal latency while maintaining accurate UPF instance selection.
2Adaptability or versatility
If UPF ID is conveyed to IMS nodes via HSS/UDM/CSCF at registration, then media gateway selection can be made, but it impacts legacy diameter protocols (Cx, Sh) which are soon to be deprecated
Solution Approach 1:
The solution extracts the UPF geographical service area information from the deprecated diameter protocol path (HSS/UDM/CSCF) and conveys it through the modern SBI interface (SMF to PCF to P-CSCF). This separation removes the dependency on legacy diameter protocols while preserving the essential functionality of media gateway selection based on UPF location.
Solution Approach 2:
The PCF acts as an intermediary between the SMF (which has UPF information) and the P-CSCF (which needs UPF geographical service area for media gateway selection). The PCF receives the UPF geographical service area from the SMF and provides it to the P-CSCF, enabling media gateway selection without directly impacting legacy diameter protocols.
3Ease of operation
If UPF ID is used for media gateway selection, then selection can be made, but it impacts S-CSCF/HSS/UDM which are not controlling user plane functions, creating unnecessary complexity
Solution Approach 1:
The solution applies local quality by limiting the UPF geographical service area information flow to only those network functions that directly control user plane functions and need this information for media gateway selection (SMF, PCF, P-CSCF). S-CSCF and HSS/UDM, which do not control user plane functions, are excluded from this information flow, reducing unnecessary complexity in the control plane.
4Measurement precision
If every new UPF instance requires reconfiguration of IMS nodes, then accurate UPF tracking is possible, but the configuration becomes non-scalable in large networks with multiple UPFs
Solution Approach 1:
The solution changes the parameter used for media gateway selection from specific UPF ID to UPF geographical service area. This parameter change allows multiple UPF instances to be associated with the same geographical service area, so when a new UPF is instantiated, it is automatically associated with the appropriate geographical area without requiring reconfiguration of IMS nodes. The P-CSCF selects media gateway based on geographical area, not specific UPF ID, enabling scalability while maintaining accurate tracking.
Data Source
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Figure 1B
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AI summary
Embodiments described herein relate to methods and apparatuses for for enabling selection of a media resource function or a media gateway in an IP session. A method in a Proxy Call Session Control Function, P-CSCF, comprises receiving one or more Session Initiation Protocol, SIP, packets originating from a wireless device as part of the IP session; responsive to receiving the SIP packets, transmitting a request to a Policy Control Function, PCF, for an indication of a geographical service area for a User Plane Function, UPF associated with the IP session; receiving an indication of the geographical service area; and selecting a gateway node based on the geographical service area.