Carrier Identification via Spectral Template Filtering
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Solution Overview
Problem
Current wireless communication systems face inefficiencies in cell and PLMN selection, particularly in mixed-RAT frequency bands, leading to unnecessary cell searches and energy wastage due to reliance on RSSI values alone, which fail to distinguish between different radio access technologies and do not effectively identify frequencies to avoid searching.
Innovation Solution
The method involves measuring received energy across various frequencies, filtering the data using matched, high-pass, low-pass, inverting, or deviation filters to identify likely carrier frequencies, thereby determining where to perform and avoid cell searches based on filtered metrics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If RSSI scan is used to identify carrier frequencies, then the scan speed is fast (300ms for 300 carriers), but the method cannot distinguish between different RATs leading to unnecessary cell searches and energy wastage
Solution Approach 1:
The patent introduces an intermediary filtering stage between RSSI scanning and cell search. A matching filter compares the scanned frequency spectrum against stored RAT-specific spectral templates to identify which RATs are actually present. This intermediary step prevents unnecessary cell searches on frequencies occupied by non-target RATs, thereby reducing energy consumption while maintaining fast scan speeds.
Solution Approach 2:
The patent changes the parameter being measured from simple power level (RSSI) to a more informative metric that incorporates spectral shape characteristics. By filtering the RSSI spectrum through RAT-specific templates, the system transforms the raw power measurement into a RAT-identified metric, enabling selective cell search and energy savings.
2Reliability
If cell search is performed on every frequency with high RSSI, then no carrier signals are missed, but the cell search process becomes time-consuming (up to 400ms per search)
Solution Approach 1:
The patent performs preliminary action by conducting RSSI scanning and RAT identification before initiating cell search. The system pre-identifies which frequencies contain target RAT carriers using spectral template matching, creating a filtered list of candidate frequencies. This preliminary filtering ensures that subsequent cell searches are only performed where needed, maintaining reliability while dramatically reducing total search time.
Solution Approach 2:
The patent extracts only the relevant information from the full frequency spectrum by removing frequencies that do not contain target RAT carriers. Instead of searching all high-RSSI frequencies, the system extracts and searches only those frequencies where the spectral template matching indicates presence of the desired RAT, reducing search time while maintaining detection reliability.
3Device complexity
If traditional RSSI-based frequency ranking is used, then the implementation is simple, but it performs unnecessary cell searches in mixed-RAT bands where energy is present but not from target RAT
Solution Approach 1:
The patent introduces an intermediary spectral template matching filter that operates between simple RSSI measurement and cell search execution. This filter adds minimal complexity by comparing the scanned spectrum against pre-stored RAT-specific templates, yet it dramatically improves productivity by eliminating unnecessary cell searches in mixed-RAT environments.
Solution Approach 2:
The patent creates a universal filtering mechanism that can identify multiple different RATs using the same spectral template matching approach. The system maintains a library of templates for different RATs and can selectively identify which RATs are present, providing multi-functional capability while adding only one filtering stage to the existing RSSI scanning infrastructure.
Data Source
AI summary
A user equipment (UE) in a communication system measures the power received in a bandwidth on possible downlink carriers in a frequency band that is supported by the UE in order to search for available carriers. Search times can be decreased on average by using a specially configured filter to process the received power measurements and then determining likely carriers based on the filtered values. Metrics from the filter can be used to indicate both where to perform cell search and where not to perform cell search.