Universal Decoder for Circularly Convolved Signals
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Solution Overview
Problem
In wireless communications using OFDM-OQAM, abrupt channel changes due to user equipment mobility lead to significant self-interference and loss of orthogonality in circularly convolved signals, particularly at the edges of transmission bursts, which existing technologies fail to effectively compensate for.
Innovation Solution
The system separates the received signal into two parts, aligns and combines their outputs through poly-phase filters (PPFs) with appropriate weighting based on channel discontinuity, using a universal decoder that accounts for channel changes, thereby compensating for abrupt channel changes without requiring additional signaling overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If circular convolution is used in OFDM-OQAM to remove pulse tail overhead, then spectral efficiency is improved, but self-interference and loss of orthogonality occur during abrupt channel changes
Solution Approach 1:
The receiver separates the received signal into two parts: the original circularly convolved signal and a copied version of the first plurality of symbol lengths. This segmentation allows independent processing of each part through separate poly-phase filters, enabling compensation of channel discontinuities while maintaining the spectral efficiency benefits of circular convolution.
Solution Approach 2:
The system copies the first plurality of symbol lengths from the circularly convolved signal before processing. This preliminary action creates a reference signal that can be used to compensate for channel discontinuities at the edges of the signal burst, preventing loss of orthogonality before it occurs during abrupt channel changes.
2Loss of substance
If circular convolution is used to remove pulse tail overhead, then transmission overhead is reduced, but self-interference increases at edges of signal burst during channel discontinuity
Solution Approach 1:
A weighting component acts as an intermediary between the poly-phase filter outputs and the final signal reconstruction. This intermediary applies appropriate weighting to the copied signal portion, reducing self-interference at the edges of the signal burst while maintaining the overhead reduction benefits of circular convolution.
Solution Approach 2:
The system changes the weighting parameter of the copied signal based on channel discontinuity detection. By adjusting the weighting factor dynamically, the system reduces self-interference at signal edges during abrupt channel changes while maintaining low overhead operation.
3Ease of manufacture
If existing technologies are used for circularly convolved signals, then implementation is simple, but they fail to compensate for abrupt channel changes
Solution Approach 1:
The universal decoder is designed to handle both normal channel conditions and abrupt channel changes using the same structure. It processes the combined output from both poly-phase filters and automatically adapts to channel discontinuities, providing reliable compensation without requiring separate specialized processing paths.
Solution Approach 2:
The system uses feedback from channel estimation to detect abrupt channel changes and adjusts the weighting of the copied signal accordingly. This feedback mechanism enables the simple universal decoder structure to compensate for channel discontinuities by dynamically adapting its processing based on observed channel conditions.
Data Source
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AI summary
System and method embodiments are provided for a receiver for circularly convolved signals. In an embodiment, a universal decoder for a circularly convolved signal includes a first decoder configured to decode the circularly convolved signal; a second decoder configured to decode a plurality of symbol lengths signal from a first portion of the circularly convolved signal, wherein the plurality of symbol lengths signal is time aligned with the circularly convolved signal before passing through the second decoder; and an adder component configured to sum a first decoder output coming from the first decoder and a second decoder output coming from the second decoder to produce a symbol value from which a log likelihood ratio (LLR) output is obtained.