Communication Terminal CSFB Channel Frequency Selection
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Solution Overview
Problem
Current communication terminals face delays and call failures during circuit-switched fallback (CSFB) from LTE to GSM networks due to inefficient channel frequency selection, leading to suboptimal call establishment in densely populated areas with high mobility and network complexity.
Innovation Solution
A communication terminal that selects and prioritizes channel frequencies based on measured power levels, creating a cell rank list for optimal radio link establishment, and attempts to connect to the second network starting from the top of this list, with a fallback to cell search only if all attempts fail.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the communication terminal uses conventional cell selection methods without pre-measuring channel frequencies, then the device complexity is reduced, but the call establishment time increases and call reliability decreases
Solution Approach 1:
The terminal pre-measures and ranks channel frequencies of the second communication network before the CSFB call establishment is triggered. This preliminary action creates a prepared cell rank list that enables faster and more reliable cell selection when fallback is needed, resolving the contradiction by advancing the measurement process to occur beforehand rather than during the critical call setup phase
Solution Approach 2:
The terminal dynamically adapts its cell selection strategy by using the pre-prepared cell rank list specific to the second communication network. Instead of using static or generic cell selection methods, the system dynamically selects from pre-evaluated options, improving both speed and reliability of the fallback process
2Reliability
If the communication terminal measures and ranks all channel frequencies before cell selection, then the call establishment reliability improves, but the device complexity and processing requirements increase
Solution Approach 1:
The cell selection process is segmented into distinct phases: pre-measurement and ranking of channel frequencies, and subsequent selection from the prepared list. This segmentation allows the complex measurement and ranking operations to be performed in advance when the system has more resources available, rather than during the time-critical call establishment phase
Solution Approach 2:
The complex task of measuring and ranking all channel frequencies is performed as a preliminary action before the actual CSFB call establishment. This prepares the cell rank list in advance, reducing the complexity of the real-time selection process while maintaining high reliability
Data Source
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AI summary
A communication terminal is described comprising a communication circuit configured to establish a first radio link to a first communication network; and to receive, via the first radio link to the first communication network, a message from the first communication network that indicates establishing a second radio link to a second communication network for a call; a controller configured to select at least one channel frequency from a plurality of stored channel frequencies provided for the call to the second communication network; control the communication circuit to establish the second radio link to the second communication network using the selected at least one channel frequency and to establish the call via the established second radio link.