IMSI Identifier Transmission for Multi-Terminal Access Transfer
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Solution Overview
Problem
Current advanced session control protocols, such as SIP, face challenges in identifying the specific terminal involved in a communication switchover when a user has multiple terminals sharing the same public identity, leading to failures in SRVCC and eSRVCC procedures.
Innovation Solution
The proposed method involves transmitting the IMSI identifier from the registration server to the access transfer control entity, allowing unambiguous identification of the terminal involved in the network change by consulting a list of IMSI identifiers, and sending this identifier to SCC-AS and ATCF entities to manage access transfers effectively in multi-terminal configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a user has multiple terminals sharing the same public identity (MSISDN), then the system supports multi-terminal subscription flexibility, but the terminal identification during access transfer becomes ambiguous and fails
Solution Approach 1:
The patent segments the identification system by introducing terminal-specific identifiers (IMSI, IMPI, GRUU) that distinguish individual terminals within a multi-terminal subscription. Each terminal is assigned unique identifiers that are transmitted during access transfer procedures, enabling precise identification of the specific terminal involved in the transfer while maintaining the overall multi-terminal subscription structure.
2Device complexity
If only MSISDN is transmitted during access transfer, then the signaling protocol remains simple, but the terminal cannot be uniquely identified among multiple terminals
Solution Approach 1:
The patent applies preliminary action by pre-configuring and storing multiple terminal identifiers (IMSI, IMPI, GRUU) in the terminal and ensuring they are available before the access transfer occurs. During the access transfer procedure, the appropriate identifier is selected and transmitted along with the MSISDN, allowing the receiving entity to reliably identify the specific terminal before the transfer is completed.
Solution Approach 2:
The patent introduces additional identifier fields as intermediaries in the signaling process. These identifiers (IMSI, IMPI, GRUU) act as mediators that bridge the gap between the simple MSISDN and the need for precise terminal identification. The identifiers are embedded in the access transfer signaling messages, enabling reliable terminal identification without fundamentally changing the existing MSISDN-based signaling framework.
3Measurement precision
If terminal identifiers are added to the signaling messages, then terminal identification becomes accurate, but the signaling message size and processing complexity increase
Solution Approach 1:
The patent makes the additional identifier fields optional and context-dependent. The terminal identifiers (IMSI, IMPI, GRUU) are included in the signaling messages only when needed - specifically when multi-terminal subscription is detected or when the network entity requires enhanced terminal identification. This multi-functional approach allows the signaling protocol to operate simply in single-terminal scenarios while providing enhanced identification capability when required, without always increasing message complexity.
Data Source
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AI summary
The invention relates to a method for changing mobile network, comprising the following steps: detecting the necessity to switch a communication in which a terminal is participating, from a first mobile network (LTE) connected to an IP network, to a second mobile network (GSM, UMTS) connected to the same IP network; transmission of the IMSI identifier of said terminal, by a first management centre (MME) pertaining to said first mobile network (LTE), to a second management centre (MSV) pertaining to said second mobile network (GSM, UMTS); sending of said IMSI identifier to the core of the IP network by said second management centre (MSC); receiving a request to change mobile network containing said IMSI identifier by an entity for controlling the access transfers (SCC-AS, ATCF); and identification of the contact address of the terminal by said entity for controlling the access transfers (SCC-AS, ATCF) by means of the IMSI identifier. Furthermore, during the recording of said terminal in said IP network, a recording server (S-CSCF) in charge of the terminal obtains the IMSI identifier and sends it to said entity for controlling the access transfers (SCC-AS, ATCF). The invention is applicable to mobile networks connected to an IMS network.