Discontinuous Fast Convolution for OFDM Spectral Containment
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Solution Overview
Problem
Current waveform processing techniques in 5G communications, such as conventional CP-OFDM, face challenges in achieving high spectral containment and efficiency due to high side lobes leading to power leakage and the need for larger guard bands, which degrades spectral efficiency and increases computational complexity.
Innovation Solution
The implementation of a discontinuous fast convolution (FC) processing scheme that segments OFDM symbol blocks into overlapping and non-overlapping parts, applies transform-domain windows, and discards overlapping samples to improve spectral containment and reduce computational complexity, allowing for higher bandwidth utilization efficiency and flexibility in handling multiple numerologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional CP-OFDM waveform processing is used, then spectral containment is insufficient due to high side lobes, but increasing spectral containment requires larger guard bands which degrades spectral efficiency
Solution Approach 1:
The patent segments the OFDM symbol blocks into multiple overlapping parts (first OFDM symbol block, second OFDM symbol block, etc.) and processes them separately through discontinuous fast convolution. This segmentation allows each segment to be filtered independently, reducing side lobes without requiring larger guard bands, thus maintaining spectral efficiency while improving spectral containment.
2Object-affected harmful factors
If continuous fast convolution processing is used, then spectral containment is improved, but computational complexity increases
Solution Approach 1:
The patent divides the continuous fast convolution processing into discontinuous segments, where each OFDM symbol block is segmented into multiple parts processed independently. This reduces the computational load per segment compared to continuous processing of the entire signal, while still achieving spectral containment through the segmented filtering approach.
Solution Approach 2:
The patent employs periodic overlapping and discarding of samples across consecutive OFDM symbol blocks. The overlapping parts are discarded after processing, creating a periodic action pattern that reduces computational complexity while maintaining spectral containment through the repeated filtering operation on segmented blocks.
3Object-affected harmful factors
If larger guard bands are used to reduce side lobes, then spectral containment improves, but bandwidth utilization efficiency decreases
Solution Approach 1:
The patent segments the signal into overlapping OFDM symbol blocks and applies filtering to each segment independently. This segmentation enables spectral containment and power leakage reduction without requiring larger guard bands, as the filtering operation on segmented blocks naturally confines the spectral energy within the original bandwidth, thus maintaining high bandwidth utilization efficiency.
Solution Approach 2:
The patent changes the processing parameters by applying transform-domain windowing and discontinuous fast convolution to segmented blocks. This parameter change enables spectral containment and power leakage reduction through the filtering operation itself, rather than relying on larger guard bands, thereby maintaining high bandwidth utilization efficiency.
4Object-affected harmful factors
If discontinuous fast convolution processing with overlapping parts is used, then spectral containment improves, but processing time increases
Solution Approach 1:
The patent segments the OFDM symbol blocks into overlapping parts and processes them in parallel or with overlapping computation. This segmentation enables the processing of multiple segments simultaneously or with overlapping time windows, reducing the total processing time compared to sequential processing of the entire signal, while still achieving spectral containment through the segmented filtering approach.
Solution Approach 2:
The patent employs periodic overlapping and discarding of samples across consecutive OFDM symbol blocks. The periodic nature of this operation allows for efficient time-domain multiplexing and reduces the total processing time by utilizing the overlapping structure to minimize idle processing time, while maintaining spectral containment through the repeated filtering operation.
Data Source
AI summary
According to an aspect, there is provided a waveform processing device. The waveform processing device includes circuitry for receiving an input signal including one or more subsequent orthogonal frequency division multiplexing, OFDM, symbol blocks each of which includes a cyclic prefix and an OFDM data block and corresponds to one or more subbands. Further, the waveform processing device includes circuitry for segmenting each OFDM symbol block of the input signal into a set of a pre-defined number of partially overlapping signal blocks of equal length so that non-overlapping samples of the pre-defined number of partially overlapping signal blocks in each set include, in combination, an OFDM data block. Moreover, the waveform processing device includes circuitry for filtering each signal block in each set and for combining the filtered signal blocks in each set using overlap-and-save processing to produce one or more filtered OFDM data blocks for each subband.