ATCF Network Node SDP Analysis for VoLTE Handover Latency
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Solution Overview
Problem
In mobile communication networks, the handover process from VoLTE to CS networks during voice calls can be delayed due to IMS signaling being routed through distant home networks, especially when users roam internationally, leading to increased data path switching times.
Innovation Solution
A network node equipped with Access Transfer Control Function (ATCF) that analyzes Session Description Protocol (SDP) offers and answers to determine codec compatibility and support, allowing codec re-negotiation via IMS signaling to ensure seamless handover without anchoring communication paths in ATGW, thereby reducing switching times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If IMS signaling is routed through distant home networks during handover, then call continuity is maintained, but data path switching time increases
Solution Approach 1:
The patent introduces a local signaling proxy or anchor point in the visited network that acts as an intermediary for IMS signaling during handover. This intermediary receives and processes SDP offers/answers locally without requiring round-trip communication with the distant home network, thereby maintaining call continuity while significantly reducing data path switching time.
Solution Approach 2:
The patent performs codec compatibility checks and SDP offer/answer exchanges in advance during the initial session setup or before handover occurs. By preparing codec negotiation results beforehand, the system eliminates the need for time-consuming signaling exchanges during actual handover, thus reducing switching time while ensuring call continuity.
2Adaptability or versatility
If codec re-negotiation is performed during handover, then codec compatibility is ensured, but signaling processing time increases
Solution Approach 1:
The patent performs codec compatibility assessment and SDP offer/answer negotiation during the initial call setup phase or in advance of handover. By completing codec re-negotiation准备工作 beforehand, the system ensures codec compatibility is established before handover occurs, eliminating the need for time-consuming signaling exchanges during the critical handover moment.
Solution Approach 2:
The patent changes the timing parameter of codec negotiation from 'during handover' to 'before handover'. This parameter change allows the system to complete codec compatibility checks in advance, ensuring adaptability while avoiding the time penalty during the actual handover execution.
Data Source
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AI summary
A network node according to the present disclosure has an ATCF function for use in eSRVCC. The network node includes an SDP analyzing unit (704) that acquires information regarding a codec contained in a received SDP offer/SDP answer, a data storage unit (706) that holds at least one of information regarding a codec supported by ATGW or a neighboring MGW, information regarding transcoding supported by the ATGW or the neighboring MGW, and information regarding a codec supported by a neighboring CS network, and a determination unit (710) that determines whether transmission of the SDP offer for codec re-negotiation from the ATCF to a communication terminal is allowed using the information regarding a codec acquired in the SDP analyzing unit and the information retrieved from the data storage unit.