IMS S-CSCF Selection Using UE Region to Cut Cross-Region Latency
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Solution Overview
Problem
Existing telecommunication networks face increased network latency and call setup time due to UE registration across different regions, leading to degraded network performance and customer experience when users handover or reconnect to different network nodes.
Innovation Solution
Implement location-based S-CSCF selection in IMS networks by determining the current region of the UE and selecting a suitable S-CSCF within that region for re-registration, rather than assigning the previous S-CSCF, using CGI information and DNS queries to ensure service continuity within the same region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the network is divided into multiple independent regions with network elements physically located within each region, then network latency is improved and outages are limited to the same region, but the complexity of S-CSCF selection and registration management increases
Solution Approach 1:
The network is divided into multiple independent regions, each with its own S-CSCF servers. The I-CSCF uses region information from the UE's current location to select an appropriate S-CSCF within the same region, avoiding cross-region registrations and reducing network latency while maintaining manageable complexity through structured region-based selection
Solution Approach 2:
The I-CSCF pre-determines the UE's current region using CGI information before S-CSCF selection. By proactively identifying the region and selecting an appropriate S-CSCF in advance, the system avoids the complexity of dynamic cross-region routing decisions during call setup
2Reliability
If the I-CSCF assigns the previous S-CSCF for re-registration, then service continuity is maintained, but network latency increases due to cross-region IP hops
Solution Approach 1:
The I-CSCF selects an S-CSCF that is locally located in the UE's current region rather than assigning the previous S-CSCF from a different region. This local selection minimizes IP hops and network latency while maintaining service continuity through proper registration transfer procedures
Solution Approach 2:
The system adds a spatial dimension to S-CSCF selection by considering the geographic region of the UE's current location. Instead of solely relying on previous registration data, the I-CSCF makes selection decisions based on the UE's current regional position, reducing cross-region traffic and improving latency
3Adaptability or versatility
If cross-region registrations are allowed, then user mobility is supported, but call setup time increases and network performance degrades
Solution Approach 1:
The network is segmented into independent regions with region-specific S-CSCF servers. The I-CSCF enforces region-based registration by selecting S-CSCFs within the UE's current region, preventing cross-region registrations. This segmentation maintains user mobility support while reducing call setup time by eliminating unnecessary cross-region routing
Solution Approach 2:
The I-CSCF acts as an intermediary that mediates between the UE's mobility needs and the region-based S-CSCF selection. It uses CGI information to determine the current region and selects an appropriate local S-CSCF, thereby supporting user mobility while preventing degraded network performance from cross-region registrations
Data Source
AI summary
Methods and systems for a location-based serving call session control function (S-CSCF) selection in an IP multimedia subsystem (IMS) network is disclosed. According to an implementation, an interrogating CSCF (I-CSCF) of an IMS network receives a request to register a user equipment (UE) to use an IP multimedia service. The request may be a session initiation protocol (SIP) register. The I-CSCF determines that the UE is located in a first region based on the geographic information in the request. The I-CSCF may determine, based at least in part on the cell global identity (CGI) information in the SIP register, that the UE is previously registered through a different region. The I-CSCF may determine a serving CSCF (S-CSCF) located in the first region to provide the IP multimedia service to the UE. The I-CSCF further registers the UE on the S-CSCF.