Dual SIM Roaming System Optimizing Call Routing Costs
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Solution Overview
Problem
Current mobile systems incur high costs for international calls and voice mail forwarding when roaming, as they do not efficiently manage roaming agreements and SIM card activations to optimize call routing and billing.
Innovation Solution
A mobile system with an auxiliary network platform that includes a mobile telephone switch, visiting location register, main location register, and short message center, which registers the mobile's location and updates the home network to route calls through an auxiliary switch, optimizing call costs by choosing the best operator for incoming and outgoing calls, and allowing transparent communication termination without changing the nominal number.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mobile uses its nominal SIM card while roaming in a visited network, then it can maintain its home network number and services, but it incurs high costs for incoming and outgoing calls due to international roaming tariffs
Solution Approach 1:
The system segments the SIM card functionality by introducing an auxiliary SIM card that operates independently from the nominal SIM card. The mobile terminal can switch between nominal mode (using nominal SIM) and auxiliary mode (using auxiliary SIM with different IMSI), allowing cost optimization for roaming calls while maintaining home network services through the nominal SIM's number and identity
Solution Approach 2:
The auxiliary SIM card acts as an intermediary element that enables cost-effective roaming calls. When activated, it provides a local IMSI that allows the mobile to access visited networks at local rates, while the nominal SIM remains active in the background to maintain the home network number for identification and service continuity
2Loss of energy
If a mobile activates an auxiliary SIM card with a different IMSI while roaming, then it can reduce call costs by accessing local networks, but it changes its identification number which may affect service continuity and caller identification
Solution Approach 1:
The system separates the identification function (handled by nominal SIM with home network number) from the access function (handled by auxiliary SIM with local IMSI). This segmentation allows the mobile to display and use the home network number for identification while using the auxiliary SIM's IMSI for actual network access and call routing, thus maintaining service continuity without changing the visible number
Solution Approach 2:
The mobile terminal is designed with multi-functionality to support both nominal SIM and auxiliary SIM operations simultaneously. It can manage multiple IMSIs, switch between them based on operational mode, and maintain consistent service delivery regardless of which SIM is actively accessing the network, ensuring universal compatibility and service continuity
3Loss of energy
If a mobile uses multiple SIM cards or switches between nominal and auxiliary SIMs, then it can optimize roaming call costs, but it increases device complexity and requires additional management mechanisms
Solution Approach 1:
The system implements dynamic SIM card management where the mobile terminal can automatically or manually switch between nominal and auxiliary SIM cards based on the operational context (roaming status, cost considerations). This dynamic switching capability allows cost optimization without requiring permanent dual-SIM hardware, reducing overall device complexity while maintaining flexibility
Solution Approach 2:
The mobile terminal incorporates self-service mechanisms for SIM card management, including automatic detection of roaming status, automatic selection of appropriate SIM card mode (nominal or auxiliary), and automatic configuration of network parameters. This self-service approach reduces the need for complex user intervention and simplifies the management interface
4Reliability
If a mobile forwards calls to voice mail while roaming using the nominal SIM, then it can maintain service continuity, but it incurs high costs for both incoming and outgoing call segments due to international tariffs
Solution Approach 1:
The system segments the voice mail forwarding function from the nominal SIM's international routing by enabling auxiliary SIM-based forwarding when roaming. The auxiliary SIM's local IMSI handles the forwarding connection, breaking the international call path into local segments and eliminating IOT charges for voice mail access while maintaining service continuity through the nominal SIM's number
Data Source
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AI summary
The system has a gateway mobile switching centre (GMSC) switch installed in a country. An auxiliary network has roaming agreements with home public land mobile network (HPLMN) and visited public land mobile network (VPLMN). A roaming hub records a mobile location with subscriber identity module card and updates a register of the mobile network to indicate the network (HPLMN) like the network (VPLMN). The hub controls return calls toward the switch and passes the incoming calls to a roaming number. The switch uses operators of international telephone network to emit calls toward the mobile.