Multi-window Fast Convolution Waveform Processing for 5G Spectral Containment
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Solution Overview
Problem
Current waveform processing techniques for 5G communications, such as conventional CP-OFDM, face challenges in achieving high spectral efficiency and bandwidth utilization due to high side lobes causing power leakage and the need for larger guard bands, which degrades spectral efficiency and cannot meet the stringent requirements of 5G NR for higher bandwidth utilization efficiency.
Innovation Solution
The implementation of a multi-window fast-convolution (FC)-based waveform processing method that uses a first time-window function, a transform-plane window function, and a second time-window function to improve spectral containment and bandwidth efficiency, allowing for better segmentation and filtering of OFDM signals to reduce out-of-band emissions and enhance channel utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional CP-OFDM waveform processing is used, then implementation simplicity is maintained, but spectral containment deteriorates due to high side lobes causing power leakage
Solution Approach 1:
The patent segments the waveform processing into multiple independent windowing stages: first time-window function applied to time-domain signal, transform-plane window function applied after FFT, and second time-window function applied after IFFT. This segmentation allows each windowing operation to target specific spectral characteristics independently, achieving superior spectral containment while maintaining modular implementation complexity.
Solution Approach 2:
The patent applies different windowing functions at different processing stages with different characteristics. The first time-window function addresses time-domain localization, the transform-plane window function addresses frequency-domain spectral shaping, and the second time-window function addresses post-transformation spectral refinement. Each windowing operation provides localized spectral improvement at its specific processing stage.
2Object-generated harmful factors
If guard bands are increased to reduce power leakage, then spectral containment improves, but bandwidth utilization efficiency deteriorates
Solution Approach 1:
The patent converts the harmful side lobe energy into beneficial spectral shaping by applying windowing functions that deliberately modify the spectral distribution. The windowing operations transform the high side lobe structure into a controlled spectral pattern with reduced peak side lobe levels, effectively converting the harmful leakage characteristic into a beneficial spectral containment property without requiring guard band expansion.
Solution Approach 2:
The patent changes the spectral parameters of the OFDM signal by applying multiple windowing functions with different characteristics. The first time-window function modifies time-domain signal shape, the transform-plane window function directly modifies frequency-domain spectral distribution, and the second time-window function further refines spectral parameters. These parameter changes achieve superior spectral containment that enables higher bandwidth utilization efficiency.
3Device complexity
If single-window fast-convolution filtering is used, then computational complexity is reduced, but spectral containment deteriorates due to interference leakage between adjacent subbands
Solution Approach 1:
The patent segments the filtering operation into three distinct windowing stages applied at different processing points: before FFT, in transform-plane, and after IFFT. This segmentation replaces the need for complex post-filtering operations with simpler, distributed windowing operations that achieve equivalent or superior interference suppression between adjacent subbands.
Solution Approach 2:
The patent applies the first time-window function to the time-domain signal before FFT transformation as a preliminary action. This preliminary windowing pre-suppresses time-domain discontinuities that would cause spectral leakage, preventing interference between adjacent subbands before the filtering operation even begins, thereby simplifying subsequent filtering requirements.
Data Source
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Figure 3B
AI summary
According to an aspect, there is provided a waveform processing device (600). Said waveform processing device (600) comprises means for performing the following. Upon receiving one or more input signals (601, 611, 621), each of which corresponds to a different subband, the waveform processing device (600) segments each of the one or more input signals (600, 611, 621) to a subband-specific set of parallel signal blocks. Then, the waveform processing device (600) filters each subband-specific set by applying at least a first time window function (603, 613, 623), a transform-plane window function (604, 614, 624) and a second time window function (608) in this order. Finally, the waveform processing device (600) concatenates filtered signals to an output signal (610).