Filterbank Multicarrier Equalizer Using Time-Domain Derivatives
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Solution Overview
Problem
Filterbank multicarrier (FBMC) modulations face challenges in robustness against channel frequency selectivity, leading to inter-symbol and inter-carrier interference, which current equalization techniques fail to adequately address due to high computational complexity and suboptimal performance.
Innovation Solution
A method involving serial-to-parallel conversion of received signals, processing through multiple parallel filterbanks using time-domain derivatives of an original filter, and weighting outputs to form new signals, with optional single tap multiplication by the inverse channel frequency response, reducing computational complexity and output distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional equalization schemes are applied to FBMC signals in the full time-frequency domain, then signal equalization is achieved, but computational complexity becomes very high
Solution Approach 1:
The patent divides the full time-frequency equalization problem into separate time-domain and frequency-domain processing stages. The received signal is first processed through time-domain filtering, then transformed to frequency domain for subcarrier-specific equalization. This segmentation allows each stage to operate independently with reduced complexity compared to full joint time-frequency processing.
Solution Approach 2:
The patent transforms the equalization problem from the time-frequency domain to the frequency domain using Fourier transform. By moving to another dimension (frequency domain), the equalization can be performed independently on each subcarrier, reducing the overall computational complexity while maintaining equalization effectiveness.
2Device complexity
If per-subcarrier equalization is used with banks of filters, then computational complexity is reduced, but inter-carrier interference compensation becomes suboptimal
Solution Approach 1:
The patent applies time-domain filtering as a preliminary action before frequency-domain equalization. This pre-processing step in the time domain prepares the signal by reducing interference components, which then makes the subsequent per-subcarrier frequency-domain equalization more effective at compensating for inter-carrier interference.
Solution Approach 2:
The patent introduces Fourier transform as an intermediary operation between time-domain filtering and frequency-domain equalization. This intermediary transformation allows the system to leverage both time-domain and frequency-domain processing benefits, achieving better inter-carrier interference compensation than pure per-subcarrier methods while maintaining lower complexity than full joint processing.
Data Source
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AI summary
A method for equalizing the received signal in communications based on filterbank multicarrier modulations and, more particularly, to such a method and system especially advantageous in situations where the channel frequency selectivity is exceptionally high. The method significantly improves the performance of traditional filterbank equalization algorithms based on finite impulse response filters at the output of the receive filterbank. Furthermore, the system consists of multiple parallel stages, the number of which can be tuned to achieve a good compromise between performance and computational complexity. Thanks to this modular structure, and to the fact that most of the architecture can be efficiently implemented using fast Fourier transforms, the system presents a very low computational complexity compared to more traditional equalizers for filterbank multicarrier modulations.