Mobile Phone SIM Card Selection via Number Portability Database
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Solution Overview
Problem
Mobile phones with multiple SIM cards require users to manually select the appropriate SIM card for calls, which is inconvenient.
Innovation Solution
The mobile phone automatically selects a SIM card by querying a number portability database to match the telecom operator of the outgoing number with the available SIM cards, using a querying module to cache results for efficient dialing and selecting the appropriate SIM card based on the telecom operator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If users manually select SIM card for each call, then they can control which SIM card to use, but the operation becomes inconvenient and time-consuming
Solution Approach 1:
The system performs preliminary actions by automatically querying the number portability database to determine the telecom operator of the outgoing number before the call is initiated, and pre-selects the appropriate SIM card based on this information, eliminating the need for manual selection at the time of dialing
Solution Approach 2:
The mobile phone system performs self-service by automatically matching the outgoing number with the appropriate SIM card through database queries and automated selection logic, without requiring user intervention in the SIM card selection process
2Measurement precision
If the system queries the number portability database for every outgoing number, then accurate SIM card selection is achieved, but the dialing time increases due to repeated database queries
Solution Approach 1:
The system performs preliminary actions by querying the number portability database in advance for frequently dialed numbers and caching the results, so that subsequent calls to the same numbers do not require repeated database queries, thus reducing dialing time while maintaining accuracy
Solution Approach 2:
The system dynamically adjusts its query behavior based on whether the outgoing number exists in the cache - using cached results for quick selection when available, and performing database queries only when necessary, thereby optimizing the balance between accuracy and speed
3Productivity
If the mobile phone stores cached results for frequently dialed numbers, then dialing speed is improved, but the device complexity increases
Solution Approach 1:
The system segments the number storage into two distinct components: a cache storage for frequently dialed numbers with pre-queryed results, and the main number portability database for comprehensive operator information. This segmentation allows the system to optimize for speed in common cases while maintaining complete accuracy for all cases
Solution Approach 2:
The system uses a lightweight cache storage mechanism that stores only essential information (number and telecom operator) for frequently dialed numbers, rather than implementing a complex permanent database solution. This cache can be refreshed or rebuilt if needed, providing a simple and flexible approach to improving dialing speed
Data Source
AI summary
A mobile phone includes at least two subscriber identity module (SIM) cards. The mobile phone queries a number portability database (NPDB) for at least two telecom operators of the at least two SIM cards. The mobile phone queries the NPDB for a telecom operator of an outgoing number dialed using the mobile phone. The mobile phone selects one SIM card with one telecom operator same as the telecom operator of the outgoing number from the at least two SIM cards.