Non-linear Phase Compensation for Sub-meter Location
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Solution Overview
Problem
Existing communication systems, such as WLANs, face challenges in providing accurate sub-meter location services due to frequency-dependent group delays caused by non-linear phase responses in devices, which were previously ignored and result in timing errors that prevent precise location determination.
Innovation Solution
A method and system that compensate for non-linear phase responses by determining a second delay value from pre-determined frequency response values and subtracting it from the first delay value to form a compensated delay value, suitable for accurate timing estimates in OFDM systems, allowing for sub-meter location capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If non-linear phase responses are ignored in timing estimation, then device complexity is reduced and ease of operation is improved, but timing precision deteriorates and location accuracy worsens
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing compensation values for non-linear phase responses during device initialization or calibration. These compensation values are stored in lookup tables or memory structures, allowing the device to quickly retrieve and apply corrections without performing complex real-time calculations. This approach maintains operational simplicity while significantly improving timing estimation accuracy by addressing non-linear phase effects in advance.
Solution Approach 2:
The patent changes parameters by introducing compensation values that adjust the estimated timing parameters. Specifically, the system calculates compensation values based on the difference between linear and non-linear phase responses, then applies these values to correct timing estimates. This parameter adjustment transforms the inaccurate timing estimates into accurate ones without requiring complete redesign of the timing estimation algorithm.
2Measurement precision
If non-linear phase compensation is implemented, then timing precision is improved and location accuracy is enhanced, but device complexity increases
Solution Approach 1:
The patent reduces device complexity by performing the computationally intensive non-linear phase analysis in advance during calibration or initialization. The results are stored as compensation values that can be quickly applied during normal operation. This shifts the complexity from runtime processing to setup-time processing, maintaining simple operational complexity while achieving high timing precision.
Solution Approach 2:
The patent uses copying by creating lookup tables or stored representations of non-linear phase characteristics. Instead of performing complex non-linear phase calculations for every timing estimation, the system copies pre-computed compensation values and applies them directly. This copying approach replaces complex real-time computations with simple data retrieval and application operations.
3Productivity
If frequency-dependent group delays are neglected, then processing speed is maintained and energy consumption is reduced, but location precision deteriorates
Solution Approach 1:
The patent maintains processing speed by pre-calculating compensation values for frequency-dependent group delays during system initialization or calibration. These pre-computed values are stored and directly applied during location determination, avoiding the need for complex real-time frequency analysis. This preliminary action preserves fast processing while achieving high location precision.
Solution Approach 2:
The patent applies copying by storing pre-computed compensation values for frequency-dependent group delays and directly applying them during timing estimation. Instead of performing complex frequency-domain analysis for each measurement, the system copies and applies pre-determined correction values, maintaining high processing speed while improving location accuracy.
4Measurement precision
If device-specific non-linearities are addressed individually, then measurement precision is improved, but ease of manufacture and system deployment become more difficult
Solution Approach 1:
The patent applies self-service by enabling each device to automatically characterize and compensate for its own non-linear phase responses through built-in calibration routines. During initialization, the device performs self-calibration by measuring its own frequency-dependent group delays and generating device-specific compensation values. This self-characterization approach eliminates the need for manual factory calibration, making manufacturing easier while achieving high measurement precision.
Solution Approach 2:
The patent uses feedback by implementing calibration routines that measure the actual non-linear phase responses of each device and use these measurements to generate appropriate compensation values. The system continuously refines its compensation based on measured performance, creating a feedback loop that automatically optimizes timing estimation accuracy for each specific device without requiring manual intervention.
Data Source
AI summary
Systems and techniques for compensating for non-linear phase responses and resulting frequency-dependent group delay using data for a specific device are described. The error in the delay value of a channel determined from a received data packet due to frequency-dependent group delay is removed by subtracting a delay value determined from measurements of a specific device from the delay value of the channel. Furthermore, compensated delay values are calculated for multiple training fields in the received data packet, enabling combining of delay values determined from different training fields that may operate at different frequencies (e.g., with different subcarriers). Hence, the systems and techniques described herein are suitable to provide accurate timing estimates that support calculations for location services, including sub-meter location of a device using a wireless network.