Mixed-Numerology OFDM Interference Cancellation by Signal Regeneration
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Solution Overview
Problem
In 5G NR communication systems, existing methods are inadequate for completely canceling interference from one numerology to another, particularly due to the overlap of OFDM symbols with different subcarrier spacings, leading to residual interference even after FFT operations.
Innovation Solution
A processor-regenerated time domain signal of the interfering numerology is used to generate a cancellation signal, which is then subtracted from the frequency domain received signal of the desired numerology, employing FFT sizes corresponding to the desired numerology to effectively mitigate interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If receiver filtering and windowing methods are used to remove interfering numerology, then some interference can be reduced, but residual interference remains and cannot be completely canceled
Solution Approach 1:
The patent creates a copy of the interfering numerology signal by regenerating it through IFFT using the known time domain samples and interfering numerology parameters. This copied interference signal is then subtracted from the received signal to achieve complete interference cancellation, going beyond the partial reduction achieved by conventional filtering methods.
Solution Approach 2:
The patent replaces the conventional mechanical signal filtering approach (Rx filtering and windowing) with a signal regeneration and subtraction method. Instead of mechanically filtering out interference, the system regenerates the interference signal digitally and subtracts it, achieving complete cancellation rather than partial reduction.
2Object-affected harmful factors
If a large filter length is used for receiver filtering to cancel interference, then interference cancellation performance improves, but system complexity and processing requirements increase
Solution Approach 1:
The patent replaces complex mechanical filtering operations with digital signal regeneration and subtraction. Instead of using long filters that require extensive computational resources, the system regenerates the interference signal through IFFT and subtracts it directly, achieving the same interference cancellation effect with lower computational complexity.
Solution Approach 2:
The patent changes the approach from modifying filter parameters (increasing filter length) to changing the fundamental method of interference removal. By regenerating the interference signal using known parameters and subtracting it, the system achieves effective interference cancellation without increasing filter length or processing complexity.
3Measurement precision
If FFT operation is performed with proper size for each numerology, then each numerology can be recovered, but interfering numerology still causes residual interference on desired numerology
Solution Approach 1:
The patent creates a digital copy of the interfering numerology signal that has been recovered through FFT, then uses this copy to generate an interference cancellation signal. This copied signal is subtracted from the desired numerology signal, removing residual interference that would otherwise remain after standard FFT-based recovery.
Solution Approach 2:
The patent segments the received signal processing into distinct components: desired numerology recovery through FFT, interfering numerology regeneration through IFFT, and interference cancellation through subtraction. This segmentation allows each component to be optimized independently while achieving complete interference removal.
Data Source
AI summary
An apparatus and a method are provided in which a processor of a receiving apparatus regenerates time domain samples of an interfering data numerology from frequency domain received signals. The processor performs FFT, with a size corresponding to a desired data numerology, on the regenerated time domain samples to generate an interfering numerology cancellation signal. The processor subtracts the interfering numerology cancellation signal from a frequency domain received signal of the desired data numerology.