UWB Clock Offset Compensation for Multi-Millisecond CIR Combining
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Solution Overview
Problem
The challenge of clock offset impairments, specifically sampling frequency offset (SFO) and carrier frequency offset (CFO), in ultra-wideband (UWB) multi-millisecond ranging processes leads to CIR smearing and phase wrapping, hindering effective signal integration and ranging accuracy.
Innovation Solution
A low complexity two-stage timing frequency estimation method is employed to compensate for clock offsets by estimating SFO from CIR fragments, compensating CFO using SFO, and combining fine CIR fragments through resampling and phase rotation, reducing implementation complexity while maintaining high performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If multi-millisecond ranging is used to extend coverage range, then ranging distance is improved, but clock offset impairments cause CIR smearing and phase wrapping
Solution Approach 1:
The patent applies preliminary action by estimating and compensating for clock offsets (SFO and CFO) before combining CIR fragments. The method first determines CIR fragments from ranging signals, then applies interpolation and estimates SFO, compensates CFO using the determined SFO, and finally combines the compensated fragments. This preliminary compensation ensures that clock offset impairments are corrected before the critical CIR combining operation, preventing CIR smearing and phase wrapping while maintaining extended ranging distance capability
2Reliability
If CIR fragments are combined to increase SNR ratio, then signal quality is improved, but clock offset causes CIR smearing and phase wrapping
Solution Approach 1:
The patent applies preliminary action by performing clock offset compensation before CIR fragment combining. The method determines SFO from interpolated CIR fragments, compensates CFO using the determined SFO, and then combines the compensated fragments. This ensures that the harmful effects of clock offsets are eliminated before the SNR-enhancing combining operation, allowing both high signal quality and accurate CIR integration to be achieved simultaneously
3Measurement precision
If clock offset compensation is applied to maintain CIR accuracy, then ranging precision is improved, but computational complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the clock offset compensation process into distinct stages: first determining SFO from CIR fragments, then compensating CFO using the determined SFO, and finally combining compensated fragments. This segmented approach breaks down the complex compensation task into manageable steps, each with a specific function, thereby reducing overall computational complexity while maintaining high ranging accuracy
Solution Approach 2:
The patent uses SFO estimation as an intermediary to facilitate CFO compensation. Instead of directly compensating both offsets simultaneously, the method first determines SFO from interpolated CIR fragments and uses this SFO information as a mediator to guide the CFO compensation process. This intermediary approach simplifies the overall compensation algorithm by creating a sequential dependency that reduces computational burden while preserving accuracy
Data Source
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AI summary
A low complexity clock drift estimation scheme for UWB-MMS ranging is proposed, assuming sampling frequency offset (SFO) and carrier frequency offset (CFO) are driven from the same clock source. SFO is first estimated with the multiple CIR fragments, and it is used to compensate the CFO for the CIR fragments. Then a fine CFO estimate is obtained from the compensated CIRs. Combining the coarse SFO and fine CFO estimate to resample and phase rotate the original CIRs can significantly improve the performance for CIR combining, thus, improve the performance for ranging.