Frequency-Domain Decision Feedback Equalization for Lower BER
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Solution Overview
Problem
Single carrier modulation in broadband communication systems faces challenges with complex linear and decision feedback equalization, especially when adaptive modulation is used, leading to higher bit error rates compared to OFDM, and is sensitive to carrier frequency offsets and non-linear distortion.
Innovation Solution
A frequency-domain decision feedback equalizer device and method that employs fast Fourier transformations, feed forward equalization, and linear feedback filtering to mitigate interference, similar to multicarrier modulation with a cyclic prefix, reducing complexity and error propagation while maintaining the advantages of single carrier modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single carrier modulation with linear and decision feedback equalization is used, then the system maintains advantages of single carrier modulation, but the equalization complexity increases and bit error rate worsens compared to OFDM
Solution Approach 1:
The patent divides the equalization process into two separate sections: a first section performing feed forward equalization using fast Fourier transformation, and a second section performing decision feedback equalization. This segmentation reduces the complexity of each individual equalization stage while maintaining overall equalization effectiveness, thereby improving reliability without excessive complexity increase.
Solution Approach 2:
The patent introduces an intermediary structure where the output of the first feed forward equalization section serves as input to the second decision feedback equalization section. This intermediary arrangement allows the system to benefit from both feed forward and feedback equalization methods while distributing the computational burden, resolving the contradiction between equalization performance and complexity.
2Adaptability or versatility
If adaptive modulation is used in single carrier systems, then system flexibility improves, but bit error rate performance deteriorates compared to OFDM
Solution Approach 1:
The patent implements a dynamic two-section equalization structure where the feed forward and feedback equalization parameters can be adaptively adjusted based on channel conditions. This dynamic adaptation enables the system to maintain low bit error rates across varying channel conditions while preserving the adaptability benefits of adaptive modulation schemes.
3Device complexity
If conventional single carrier equalization is used, then implementation is simpler than feedback-based approaches, but error propagation increases
Solution Approach 1:
The patent introduces a feedback mechanism in the second equalization section where detected symbols are fed back to compensate for intersymbol interference. This feedback approach effectively reduces error propagation by correcting decisions based on previously detected symbols, improving reliability while the two-section structure keeps the overall complexity manageable.
Data Source
AI summary
A fast Fourier transformation is performed on a first vector of signals, and as a result a second vector of signals is provided. A feed forward equalization is performed by multiplying each of the components of said second vector with equalization parameters, and as a result a third vector of signals is provided. An inverse fast Fourier transformation is performed on said third vector, and as a result a fourth vector of signals is provided. An output signal of said first section is provided on the basis of said fourth vector of signals. In a second section a signal derived from an output signal of said second section is is filtered via linear feedback filtering and the filtered signal is added to said first section output signal, and an added signal is provided, and said second section output signal is generated by extracting samples from said added signal.