OFDM Active Interference Cancellation Using Non-Zero Tones
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Solution Overview
Problem
Current methods for mitigating in-band spurious signals in OFDM transmitters, such as zeroing tones, are inadequate in achieving the required interference suppression levels without excessive degradation of communication throughput and increased hardware complexity.
Innovation Solution
The implementation of active interference cancellation (AIC) through a computational algorithm that transmits non-zero tones to cancel interference, minimizing the number of tones used and maximizing interference suppression, with a hardware implementation that includes up-sampling and matrix computations to determine optimal tone values for interference cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If narrow-band RF-band notch filters are used to eliminate interference bands, then interference suppression is improved, but chip cost and design complexity increase significantly
Solution Approach 1:
The patent replaces physical narrow-band RF notch filters with a digital signal processing-based active interference cancellation system. The system uses digital computation to generate cancellation signals that actively suppress interference in protected bands, eliminating the need for complex hardware filters while achieving comparable or superior interference suppression performance.
Solution Approach 2:
The system dynamically adjusts transmission parameters by computing optimal tone values and cancellation signals based on real-time spectral analysis. The active interference cancellation mechanism changes the amplitude and phase parameters of OFDM tones to minimize interference in protected bands while maintaining communication performance in active bands.
2Adaptability or versatility
If conventional narrow-band filter design is used with adjustable center notch frequency, then adaptability to regional spectrum use is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent replaces hardware-based frequency adjustment mechanisms with software-defined spectral management. The system uses digital signal processing to dynamically reconfigure which frequency bands are protected and which are active, allowing regional spectrum adaptation through software configuration rather than hardware redesign.
Solution Approach 2:
The system dynamically adapts to different regional spectrum requirements by computing protection patterns and cancellation signals in real-time based on configured protected bands. The active interference cancellation mechanism can quickly reconfigure protection patterns without requiring hardware changes, enabling flexible adaptation to different regulatory environments.
3Object-affected harmful factors
If zeroing OFDM sub-carriers in interference bands is implemented, then interference protection is improved, but communication throughput deteriorates due to loss of data transmission capacity
Solution Approach 1:
The patent converts the harmful interference problem into a beneficial cancellation opportunity. Instead of simply removing tones (which loses capacity), the system computes active cancellation signals that suppress interference while preserving data transmission. The interference cancellation mechanism transforms the interference challenge into a means of protecting protected bands without sacrificing throughput in active bands.
Solution Approach 2:
The system applies partial interference cancellation by targeting only the specific frequency components that cause interference in protected bands, while leaving the majority of OFDM tones intact for data transmission. This selective approach provides sufficient interference protection without the excessive throughput loss associated with zeroing multiple tones.
4Object-affected harmful factors
If more OFDM sub-carriers are zeroed to achieve better interference suppression, then interference suppression is improved, but communication throughput deteriorates further
Solution Approach 1:
The patent transforms the interference suppression challenge into an active cancellation process that achieves high suppression levels without proportionally increasing tone zeroing. The system computes cancellation signals that efficiently suppress interference through constructive and destructive interference patterns, achieving greater than 50 dB suppression while maintaining most tones active for data transmission.
Solution Approach 2:
The system optimizes the balance between interference suppression and throughput by dynamically adjusting cancellation signal parameters. The active interference cancellation mechanism computes optimal amplitude and phase values for cancellation tones based on the spectral characteristics of interference and desired protection levels, achieving maximum suppression with minimum impact on data transmission capacity.
Data Source
AI summary
A computational algorithm provides new and effective interference cancellation of the in-band spurious signals for the Orthogonal Frequency Division Multiplex (OFDM) transmitters. This new interference cancellation transmits non-zero tones may be used to cancel the interference generated by the modulated data signals. This minimizes the number of tones used and maximizes the interference suppression achieved at the same time. The technique described is one of active interference cancellation (AIC).