Femto Cell Identification via Timing Difference Analysis
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Solution Overview
Problem
Current methods for identifying femto cells in wireless communication networks face challenges such as distinguishing between femto cells sharing common Primary Scrambling Codes, limited accuracy in geo-location, and difficulties in seamless call hand-off due to ambiguous identification and poor GPS coverage.
Innovation Solution
A method that determines observed timing differences between femto cells and macro cells, comparing these differences to reference timing difference data to identify the specific femto cell, allowing for accurate geo-location and efficient call hand-off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If femto cells share common Primary Scrambling Codes to reduce complexity, then device complexity is reduced, but femto cells become difficult to distinguish from one another
Solution Approach 1:
The patent introduces timing difference data as an intermediary parameter to differentiate femto cells. Instead of relying solely on Primary Scrambling Codes, the system uses the timing difference between uplink signals received from the wireless communication unit and corresponding downlink signals transmitted to the unit. This intermediary measurement enables distinction between femto cells sharing the same PSC without increasing device complexity.
Solution Approach 2:
The patent changes the identification parameter from static PSC-based identification to dynamic timing difference-based identification. By measuring and comparing timing differences (which vary between femto cells even when PSC is shared), the system achieves precise femto cell differentiation while maintaining simple device architecture.
2Area of stationary object
If macro cells are used for geo-location, then coverage area is large, but location accuracy is reduced
Solution Approach 1:
The patent segments the macro cell coverage area into multiple femto cell zones. By identifying which specific femto cell a wireless communication unit is connected to within a macro cell footprint, the system divides the large macro cell area into smaller, more precisely locatable femto cell areas, thereby improving geo-location accuracy while maintaining broad coverage.
3Measurement precision
If femto cells are used for geo-location, then location accuracy is improved, but femto cells are difficult to distinguish leading to identification ambiguity
Solution Approach 1:
The patent uses timing difference data as an intermediary to resolve identification ambiguity. The network element measures the timing difference between uplink and downlink signals, which serves as a unique identifier for each femto cell. This intermediary measurement enables accurate geo-location through femto cell identification without requiring complex device-side processing.
4Measurement precision
If timing difference measurement is implemented, then femto cell identification accuracy is improved, but measurement and detection difficulty increases
Solution Approach 1:
The patent implements a feedback mechanism where the network element measures timing differences and uses this information to identify femto cells. The system continuously monitors timing difference data and feeds this information back into the identification process, enabling accurate femto cell differentiation through automated measurement and comparison procedures.
Data Source
AI summary
A femto cell is located within a macro cell of a wireless communication system. A method of identifying the femto cell comprises: determining at least one timing difference, the at least one timing difference being observed for communications between a wireless communication unit and each of a femto cell and at least one macro cell; and comparing the at least one observed timing difference to reference timing difference data. The identity of the femto cell may allow the location of the femto cell to be set as a geographical location for a wireless communication device that is within the footprint of the femto cell. The identity of the femto cell may allow hand in of an ongoing call, from the macro cell to the femto cell.