OQAM Signal Synchronization Using Causal Prototype Filter Estimators
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Solution Overview
Problem
Current techniques for synchronizing receivers of OFDM/OQAM and BFDM/OQAM multicarrier signals are complex and inefficient, particularly in estimating time, phase, and frequency shifts introduced by the transmission channel, often requiring lengthy preambles and increased computational complexity.
Innovation Solution
A method that uses estimators accounting for the coefficients of the prototype filter to simplify the synchronization process by reducing the complexity of estimating time and phase shifts, allowing for a shorter preamble and improved frequency estimation over a larger band, while considering the causality of the prototype filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional synchronization techniques are used for OQAM multicarrier signals, then time and phase shift estimation can be performed, but the computational complexity increases and the preamble length becomes excessive
Solution Approach 1:
The patent segments the synchronization process into two distinct stages: a first stage that estimates time shift using only real parts of the signal, and a second stage that estimates phase shift using both real and imaginary parts. This segmentation allows each estimator to be optimized independently, reducing overall computational complexity while maintaining estimation accuracy
Solution Approach 2:
The patent extracts and utilizes the specific structure of OQAM signals by separately processing real and imaginary parts at different stages. The time shift estimator extracts information only from real parts, while the phase shift estimator extracts information from both parts, optimizing the use of available signal components
2Measurement precision
If conventional synchronization techniques are used for OQAM multicarrier signals, then frequency shift estimation can be performed, but the frequency band coverage is limited
Solution Approach 1:
The patent implements a feedback mechanism where the time shift estimate obtained in the first stage is used to correct the received signal before performing frequency shift estimation in the second stage. This sequential feedback approach allows the frequency estimator to operate on a pre-corrected signal, improving accuracy and enabling broader frequency band coverage
3Ease of manufacture
If a non-causal prototype filter is used for signal processing, then processing can be simplified, but the receiver becomes physically unrealizable
Solution Approach 1:
The patent performs time shift estimation and compensation before the main signal processing operations. By estimating and correcting the time shift in advance using only real parts of the signal, the system prepares the signal for subsequent processing without requiring non-causal operations, ensuring physical realizability while maintaining processing simplicity
Data Source
Figure 1~2A
Figure 2B~11
Figure 3~5
AI summary
The invention relates to a method for receiving an OQAM multi-carrier signal, which implements a step of estimating (21), in the time domain, at least one time, phase, and/or frequency shift of said multi-carrier signal. The estimation step (21) implements at least one estimator in order to estimate said time shift, referred to as a time estimator, and/or at least one estimator for estimating said phase shift, referred to as a phase estimator, and/or at least one estimator for estimating said frequency shift, referred to as a frequency estimator. According to the invention, said multi-carrier signal includes at least one preamble, and at least one of said estimators takes into account coefficients of a prototype filter used in transmission in order to shape at least one preamble inserted into said multi-carrier signal.