GSM RF Carrier Bandwidth Screening for Faster Band Scanning
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Solution Overview
Problem
Mobile stations operating in GSM networks face challenges in quickly scanning the RF band to distinguish between valid GSM and non-GSM RF carrier signals, particularly in the 850 MHz band, due to the time required to reject non-GSM signals, which can exceed the five-second acquisition standard.
Innovation Solution
Implementing a method that involves monitoring RF channels, estimating the bandwidth of candidate RF carrier signals, and using a Fast-Fourier Transform process to differentiate between GSM and non-GSM signals based on bandwidth, allowing for rapid identification and rejection of non-GSM signals, thereby reducing the scanning time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the FCCH detector is used to reject non-GSM RF signals, then the reliability of signal identification is improved, but the scanning time increases beyond the five-second acquisition standard
Solution Approach 1:
The patent applies preliminary action by performing bandwidth estimation using Fast-Fourier Transform on candidate RF carrier signals before the FCCH detector processes them. This preliminary bandwidth check quickly identifies and rejects non-GSM signals that have incorrect bandwidth characteristics, preventing them from consuming the time required for complete FCCH detection cycles. The bandwidth estimation is performed in advance to filter out invalid signals early in the scanning process.
Solution Approach 2:
The patent segments the signal validation process into two independent stages: first, a quick bandwidth estimation stage using Fast-Fourier Transform to filter obviously invalid signals, and second, the more thorough FCCH detection stage for signals that pass the bandwidth check. This segmentation allows the system to apply different levels of scrutiny to different signals based on their bandwidth characteristics, reducing overall scanning time while maintaining reliability.
2Reliability
If the mobile station scans all RF channels in the 850 MHz band to ensure complete network coverage, then the completeness of network detection is improved, but the time required to complete scanning increases
Solution Approach 1:
The patent applies preliminary action by performing bandwidth estimation using Fast-Fourier Transform on candidate RF carrier signals before the FCCH detector processes them. This preliminary bandwidth check quickly identifies and rejects non-GSM signals that have incorrect bandwidth characteristics, preventing them from consuming the time required for complete FCCH detection cycles. The bandwidth estimation is performed in advance to filter out invalid signals early in the scanning process.
Solution Approach 2:
The patent applies partial action by implementing a two-stage validation process where not all signals undergo the complete FCCH detection cycle. Instead, signals are first evaluated using the computationally lighter Fast-Fourier Transform bandwidth estimation, and only those that pass this preliminary check proceed to full FCCH detection. This partial application of the more rigorous detection method maintains network detection completeness while significantly improving scanning speed.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces the time required to scan the RF band and ensures GSM network acquisition within the standard five seconds by efficiently differentiating between valid and non-valid RF carrier signals.
Implementation Method 1
estimating the bandwidth of the candidate RF carrier signal and/or detecting whether the candidate RF carrier signal has a predetermined system signal (e.g., a frequency correction channel (FCCH) burst) of the wireless communication network modulated thereon
Data Source
AI summary
One illustrative method of scanning a radio frequency (RF) band (e.g. 850 MHz band) for valid RF carrier signals of a wireless communication network (e.g. a GSM network) includes the steps of monitoring an RF channel to receive a candidate RF carrier signal; identifying whether the candidate RF carrier signal is a valid RF carrier signal of the wireless communication network by estimating a bandwidth of the candidate RF carrier signal and, if the estimated bandwidth is different from a predetermined bandwidth associated with valid RF carrier signals of the wireless communication network, identifying that the candidate RF signal is not a valid RF carrier signal of the wireless communication network; and repeating the acts of monitoring and identifying for a next RF channel of a plurality of RF channels associated with the wireless communication network. Preferably, the RF bandwidth estimation is performed together with a system signal detection process (e.g. FCCH detection). Advantageously, the time required to scan the RF band is reduced.