FBMC Receiver Carrier Frequency Offset Compensation
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Solution Overview
Problem
Current FBMC systems face challenges in compensating for carrier frequency offsets, especially when multiple terminals share subcarriers, leading to interference between subchannels, and existing solutions only address single-user contexts or do not effectively handle significant frequency offsets.
Innovation Solution
An FBMC receiver is designed with an FFT module, carrier frequency offset estimator, shift module, and interference reduction filter using matrix multiplication to compensate for carrier frequency offsets, allowing for effective interference reduction between subcarriers even when frequency offsets are significant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If simple phase multiplication is used for carrier frequency offset compensation, then single-user offset compensation is achieved, but interference between subchannels cannot be reduced in multi-user scenarios
Solution Approach 1:
The patent segments the compensation process into two distinct stages: first applying phase multiplication to compensate for carrier frequency offset, then applying interference reduction filtering to eliminate subchannel interference. This segmentation allows each stage to address its specific function without compromising the other, resolving the contradiction between achieving offset compensation and reducing interference in multi-user scenarios.
Solution Approach 2:
The patent introduces an interference reduction filter as an intermediary component between the phase multiplication stage and the signal output. This filter acts as a mediator that processes the compensated signal to remove inter-subchannel interference, enabling both offset compensation and interference reduction to coexist in the same system.
2Device complexity
If carrier frequency offset compensation is implemented without interference reduction, then processing complexity is reduced, but signal quality deteriorates in multi-user scenarios with significant frequency offsets
Solution Approach 1:
The patent divides the signal processing into segmented stages: a first processing stage for carrier frequency offset compensation using phase multiplication, and a second processing stage for interference reduction using filtering. This segmentation allows the system to maintain reasonable complexity while progressively improving signal quality through each stage.
Solution Approach 2:
The patent performs carrier frequency offset compensation as a preliminary action before applying interference reduction filtering. By correcting the frequency offset first, the subsequent filtering operation becomes more effective at removing interference, as the signal components are properly aligned in the frequency domain.
3Ease of operation
If existing FBMC receiver structures are used, then basic demodulation is achieved, but accurate offset compensation in multi-user scenarios cannot be performed
Solution Approach 1:
The patent applies preliminary carrier frequency offset compensation through phase multiplication before the standard demodulation process. This preliminary action corrects frequency errors that would otherwise degrade demodulation accuracy in multi-user scenarios, while maintaining compatibility with existing FBMC receiver structures.
Solution Approach 2:
The patent introduces an interference reduction filter as an intermediary processing stage that enhances measurement precision for offset compensation. This filter operates on the demodulated signal to remove inter-subchannel interference, thereby improving the accuracy of frequency offset estimation and compensation in multi-user environments.
Data Source
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Figure 3A~3B
AI summary
The invention relates to a filter bank receiver (FBMC) performing carrier frequency offset compensation in the frequency domain. The receiver comprises an FFT module extended by the overlap factor (610), a shift module (630) of a predetermined number of subcarriers at the output of the FFT followed by a subcarrier interference reduction filter (640), the number of subcarriers and the coefficients of the interference reduction filter being determined from an estimate ( ) of the frequency offset. The resulting sample vector is then subjected to channel equalization (650) before being filtered by an analysis filter bank and spectrally despread (660). Finally, after spectral despreading, the sample vector is demodulated by OQAM demodulation (670) to recover the transmitted data.