Reduced Complexity UF-OFDM Encoder Architecture
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Solution Overview
Problem
The computational complexity of Universal Filtered Orthogonal Frequency Division Multiplexing (UF-OFDM) encoders is excessively high, making them impractical for implementation, especially when compared to standard OFDM systems, due to the high number of multiplications required for processing UF-OFDM symbols, which results in increased complexity and out-of-band leakage.
Innovation Solution
The proposed solution separates the UF-OFDM processing into sub-band and sub-carrier processing stages, reducing redundant operations by computing Q segments of K samples and K segments of Q samples separately, and using IFFT and FFT operations to generate the UF-OFDM data stream with reduced filter coefficients, thereby decreasing the overall complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If standard UF-OFDM encoding is implemented with independent filtering of each sub-band, then out-of-band leakage is reduced and signal-to-interference ratio is improved, but computational complexity increases excessively
Solution Approach 1:
The patent segments the UF-OFDM processing into two distinct stages: sub-band processing (generating N samples from Q symbols per sub-band) and sub-carrier processing (rearranging samples to final positions). This segmentation allows redundant operations to be identified and eliminated, reducing computational complexity while preserving the filtering benefits that reduce out-of-band leakage
Solution Approach 2:
The patent extracts and eliminates redundant operations from the standard UF-OFDM encoding process. By analyzing the sub-band and sub-carrier processing stages separately, the invention removes unnecessary computations while maintaining the core functionality of independent sub-band filtering that reduces out-of-band leakage
2Reliability
If independent filtering of each sub-band is performed, then signal-to-interference ratio is improved, but the number of multiplications required increases
Solution Approach 1:
The patent divides the filtering operation into sub-band processing and sub-carrier processing stages. By segmenting the operations, the invention identifies that certain multiplications are redundant when sub-bands are processed independently, allowing elimination of unnecessary multiplications while preserving the signal-to-interference ratio improvements from filtering
Solution Approach 2:
The patent changes the processing parameters by separating sub-band and sub-carrier operations. This parameter change reveals that the number of required multiplications can be reduced by avoiding redundant computations in the sub-carrier processing stage, while maintaining the filtering parameters that improve signal-to-interference ratio
3Device complexity
If UF-OFDM encoding is implemented with reduced complexity operations, then computational complexity is reduced, but processing accuracy may be affected
Solution Approach 1:
By segmenting the UF-OFDM encoding into sub-band and sub-carrier processing stages, the patent maintains processing accuracy within each stage while reducing overall complexity. The segmentation ensures that critical filtering operations are preserved with full precision, while redundant operations are eliminated
Solution Approach 2:
The patent extracts only the essential operations needed for accurate UF-OFDM encoding, removing redundant computations. This extraction approach maintains processing accuracy for the core filtering and transformation operations while reducing computational complexity by eliminating unnecessary steps
Data Source
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AI summary
An encoder architecture for UF-OFDM or UFMC is provided, in which samples are first processed sub-band wise, and then resorted for sub-carrier-wise processing. The sub-carrier processing may comprise separate processing for the two extremity parts of the base band signal corresponding to the transient state (or ramping up and down of the filter) of the UF-OFDM data stream and for a core part of the base band signal corresponding to the non-transient state of the UF-OFDM data stream, and then concatenated to obtain a UF-OFDM data stream. In certain embodiments a first extremity part of the base band signal corresponding to the transient state of the UF-OFDM data stream is calculated directly, and the other extremity part inferred from the core part and the first extremity part. The core and extremity part processors may be implemented with filters adapted to multiply each sample by a respective filter coefficient. Modifying these coefficients can introduce a frequency shift or convert the encoder for OFDM encoding.