SRVCC Media Gateway Selection for Voice Call Continuity
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Solution Overview
Problem
Current SRVCC procedures in telecommunications networks face issues with speech quality degradation and inefficient resource allocation during handovers from Packet Switched (PS) to Circuit Switched (CS) access networks, as they lack optimal selection of Media Gateways (MGWs) and often require transcoding, leading to sub-optimal codec selection and excessive node allocation.
Innovation Solution
A method and apparatus for a Mobile Switching Centre (MSC) server to obtain an indication of already-seized MGWs and select an appropriate MGW for the session based on this information, optimizing resource allocation and codec selection to minimize transcoding and improve speech quality by determining the best MGW for the CS access network during a SRVCC handover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a new Media Gateway (MGW) is allocated for each SRVCC handover, then resource allocation is simplified, but resource efficiency deteriorates due to excessive node allocation
Solution Approach 1:
The system performs preliminary actions by having the IMS network indicate already-seized MGWs before the handover is executed. The MSC server uses this advance information to select an appropriate MGW, avoiding the need to allocate a new MGW and thereby improving resource efficiency.
Solution Approach 2:
Instead of allocating new MGWs for each handover, the system recovers and reuses already-seized MGWs. The MSC server selects from previously allocated MGWs that are still available, discarding the practice of continuous new allocation and thereby reducing the total number of MGWs in the network.
2Ease of operation
If codec selection is performed without knowing the actual codec used on PS access, then CS access codec selection is simplified, but speech quality deteriorates due to mismatched codec selection
Solution Approach 1:
The system implements feedback by obtaining codec information from the MME about the actual codec being used on the PS access. This feedback loop allows the MSC server to make informed codec selection decisions for the CS access, matching the codec used on PS access and thereby maintaining speech quality.
3Adaptability or versatility
If multiple separate nodes (M-MGW, ATGW, TrGW) are seized for SRVCC handover, then functional requirements are met, but system complexity increases due to inefficient node allocation
Solution Approach 1:
The system merges the functions of multiple separate nodes (M-MGW, ATGW, TrGW) into a single MGW selection process. By obtaining an indication of already-seized MGWs from the IMS network and selecting one appropriately, the system consolidates what would otherwise require multiple separate node seizures, thereby reducing system complexity while maintaining functional requirements.
Data Source
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AI summary
A mechanism is presented for performing a session transfer with Single Radio Voice Call Continuity, SRVCC, from a Packet Switched, PS, access to a Circuit Switched, CS, access of a telecommunications session that has been established over the PS access via an IP Multimedia Subsystem, IMS, network. The method includes receiving a request for the transfer of the session to the CS access. An indication of an already- seized media gateway, MGW, that has been established for use in one or more other sessions over the CS access is obtained from the IMS network. A MGW is selected as a Mobile-Media Gateway, M-MGW, for the session based on the obtained indication. Allocation of resources for the session in the CS access network is initiated, including specifying the MGW to be used as the Mobile-Media Gateway, M-MGW. Transfer of the session to the CS access is then initiated.