IR-UWB Receiver Synchronization via Frequency Offset Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing IR-UWB systems face challenges in achieving low-SNR synchronization, particularly when dealing with conventional levels of central frequency offset (CFO), which limits the duration of correlation and affects the accuracy of time and frequency synchronization.
Innovation Solution
The method involves a telecommunications receiver device that synchronizes with an IR-UWB signal using a preamble with specific sequence structures. The preamble includes a first portion with multiple occurrences of a sequence of weighted pulses and a second portion with the complex conjugate of the first sequence. The device samples the preamble, determines frequency shifts, and applies synchronization based on these shifts to achieve accurate time and frequency alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long sequences are used for correlation to achieve low-SNR synchronization, then synchronization accuracy is improved, but the duration of correlation is limited by frequency offset causing phase rotation
Solution Approach 1:
The patent converts the harmful effect of frequency offset into a useful measurement. By analyzing the phase rotation caused by frequency offset during correlation, the system estimates the frequency offset value and uses it to correct the correlation process. This allows long correlation sequences to be used for low-SNR synchronization while compensating for the phase rotation that would otherwise limit correlation duration.
Solution Approach 2:
The system implements a feedback mechanism where the frequency offset is estimated from the correlation process itself, then this estimated offset is used to correct subsequent correlation operations. The patent uses the phase information from correlation peaks to calculate frequency offset, which is then applied to adjust the correlation process, enabling extended correlation duration without losing synchronization accuracy.
2Adaptability or versatility
If non-coherent accumulations are employed to overcome phase rotation, then frequency offset tolerance is improved, but processing improvement is reduced compared to coherent accumulations
Solution Approach 1:
The patent changes the parameter of accumulation type from purely non-coherent to a hybrid approach. Instead of using only non-coherent accumulation (which loses phase information) or purely coherent accumulation (which is sensitive to frequency offset), the system performs coherent accumulation with frequency offset compensation. This parameter change allows the system to maintain phase information for processing improvement while compensating for frequency offset effects.
3Reliability
If correlation is performed with conventional frequency offset, then synchronization can be achieved, but the maximum correlation duration is limited
Solution Approach 1:
The patent performs preliminary frequency offset estimation using a reduced set of correlation operations or pilot sequences before the main synchronization correlation. This preliminary action characterizes the frequency offset conditions, which are then used to pre-adjust the main correlation process. By performing this preliminary frequency characterization, the system enables longer correlation durations without the phase rotation problems that would otherwise limit correlation duration under conventional frequency offset conditions.
Data Source
AI summary
A method for synchronizing in a receiver receiving an IR-UWB signal including data packets having a preamble comprising a first preamble portion of at least two occurrences of a first preamble sequence of N pulses spaced apart by a period T and that are each equal to a reference pulse weighted by a complex coefficient cn, n=0 to N−1 indicating the rank of the pulse in the first sequence and a second preamble portion of at least two occurrences of a second preamble sequence equal to the complex conjugate of the first sequence, comprising: considering the NP successive samples sn for n=0 to NP−1, of a slice, of duration NT, of the first and respectively second preamble portion of a received packet, determiningxn=c⌊nP⌋*sn,and respectivelyyn=c⌊nP⌋zn,with Ts the sampling period T=P×Ts; determining the frequency fd and respectively fg of the sequence xn and respectively yn; computing a shift Δf to be applied to synchronize to the received signal via:fd=1NPTs(⌊t0mT⌋+ϵ)+Δffg=-1NPTs(⌊t0mT⌋+ϵ)+Δf