Frequency Offset Estimation Using Cyclic Prefix Correlation and Low-Pass Filtering
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Solution Overview
Problem
Current wireless communication standards for power grid control, such as WirelessHART and WIA-FA, face challenges in achieving low latency and high reliability due to non-optimized physical communication layers, particularly in frequency offset estimation, which is crucial for reliable message delivery in wireless networks.
Innovation Solution
A method and packet receiver that utilize a cyclic prefix (CP) based similarity measure determination and a low-pass filter for efficient frequency offset estimation in wireless communication networks, allowing for accurate estimation even with short preambles, thereby reducing latency and improving communication reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long preamble sequences are used for frequency offset estimation, then frequency offset estimation accuracy is improved, but transmission latency increases
Solution Approach 1:
The patent extracts only the necessary portion of the preamble (the cyclic prefix part) for frequency offset estimation, rather than using the entire long preamble sequence. This selective extraction maintains estimation accuracy while significantly reducing the time required for the process.
Solution Approach 2:
The patent segments the preamble into functional parts, using only the cyclic prefix portion for frequency offset estimation. This segmentation allows the system to perform estimation with a shorter effective sequence, reducing latency while maintaining accuracy through targeted use of the available signal structure.
2Measurement precision
If identical OFDM symbols are transmitted for frequency offset estimation, then estimation accuracy is improved, but transmission latency doubles
Solution Approach 1:
The patent makes the cyclic prefix serve dual purposes: it maintains its traditional function of protecting against inter-symbol interference while simultaneously providing the reference signal needed for frequency offset estimation. This self-service approach eliminates the need for separate estimation sequences.
Solution Approach 2:
The cyclic prefix is designed to perform multiple functions: signal protection and frequency offset estimation. By making the estimation process utilize existing signal structure rather than requiring dedicated estimation symbols, the system achieves accurate estimation without doubling transmission time.
3Loss of time
If short preambles are used to reduce latency, then transmission latency is reduced, but frequency offset estimation accuracy deteriorates
Solution Approach 1:
The patent changes the approach to estimation by utilizing the cyclic prefix structure and applying low-pass filtering to the correlation output. This parameter change in the processing method allows accurate estimation to be achieved with shorter preamble sequences, overcoming the traditional trade-off between length and accuracy.
Solution Approach 2:
The patent introduces low-pass filtering as an intermediary processing step that enhances the frequency offset estimation accuracy from the cyclic prefix correlation. This intermediary filtering operation compensates for the reduced sequence length, maintaining accuracy despite using shorter preambles.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution enables efficient frequency offset estimation, reducing latency and ensuring reliable wireless communications in power grid control networks by using CP-based similarity measures and low-pass filtering, which is essential for accurate channel estimation and phase rotation compensation.
Implementation Method 1
applying a low-pass filter to the sequence of similarity measure values, resulting in a filtered sequence of similarity measure values
Implementation Method 2
determining a sequence of similarity measure values between the CP of the preamble and the end-portion of the preamble
Data Source
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AI summary
There is provided mechanisms for frequency offset estimation in a wireless communication network for power grid control. The wireless communication network employs time based scheduling of packets. A method is performed by a packet receiver in the wireless communication network. The method comprises receiving a packet from a packet transmitter. The packet comprises a preamble. The preamble is composed of samples of a single OFDM symbol. The preamble has a CP defined by a repetition of samples from an end- portion of the preamble. The preamble, except for the CP, is free from any repeated sequence of samples. The method comprises determining a sequence of similarity measure values (ie. correlation) between the CP of the preamble and the end-portion of the preamble. The method comprises applying a low-pass filter to the sequence of similarity measure values, resulting in a filtered sequence of similarity measure values. The method comprises performing frequency offset estimation on the filtered sequence of similarity measure values.