Femtocell Location via Differential Timing Offset Elimination
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Solution Overview
Problem
Current methods for locating femtocells in wireless communication networks are inefficient due to limitations such as the absence of GPS in some femtocells, inaccurate user-provided data, and uncertainties in algorithms used for direct solutions, especially in asynchronous networks where timing offsets vary.
Innovation Solution
A method that utilizes timing data from signals received by mobile communication devices from both femtocells and macrocells to derive differential distance measurements, eliminating timing offsets and approximating the distance between base stations and femtocell HomeNodeBs, allowing for accurate geographical location estimation of femtocells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS chip-set is built into femtocell, then location accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses mobile devices as intermediary elements to collect timing data from femtocells and macrocells. Instead of adding GPS to femtocells, the system leverages existing mobile devices that already have location capabilities to perform timing measurements and derive femtocell locations through differential distance calculations.
Solution Approach 2:
The patent replaces the mechanical/GPS-based location determination system with a signal timing-based system. By measuring timing differences of signals from femtocells and macrocells, the system calculates differential distances to determine location without requiring physical GPS receivers in femtocells.
2Device complexity
If timing data from asynchronous networks is used directly, then location determination is simplified, but measurement precision deteriorates due to timing offsets
Solution Approach 1:
The patent extracts and eliminates the timing offset component from the timing measurements. By removing the effect of asynchronous timing offsets through differential measurements, the system recovers accurate differential distance information from the remaining timing data.
Solution Approach 2:
The patent uses measurements from multiple mobile devices and multiple macrocells to obtain sufficient differential distance measurements. By collecting more measurements than the minimum required, the system can accurately determine femtocell location even in the presence of timing variations.
Data Source
AI summary
A system and method of determining the geographical location of a femtocell (640A) of an asynchronous cellular wireless communication system (600) are provided. Timing data is obtained from communication signals received by a first group of mobile communication units (450) from a femtocell (640A), and from at least two macro cells (410A, 420A, 670A). A difference (D12) in path distance from two macro cells to the femtocell (640A) is estimated using the timing data. A correction is made to remove timing offsets of the base stations of the macro cells. This provides an estimate of the geographical location of the femtocell (640A), when combined with either a similar estimate derived from signals received from a third macrocell, or an estimate derived from signal propagation data.