SC-FDMA Receiver Frequency Offset Correction Per User Signal
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Solution Overview
Problem
In SC-FDMA systems, frequency offsets caused by local oscillator shifts and mobile object Doppler variations lead to signal distortion and adjacent channel interference, degrading reception quality, as existing techniques do not adequately address these issues.
Innovation Solution
A receiver mechanism that converts reception signals into the frequency domain, identifies user signals using selected sub-carriers, generates correction signals to address frequency offsets, and corrects these offsets before demodulation, employing DFT and frequency conversion to improve reception characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If frequency domain processing is applied to all users at once, then receiver structure is simplified, but frequency offset effects are not corrected leading to signal distortion and interference
Solution Approach 1:
The receiver processes each user's signal separately after initial frequency domain conversion, applying individual frequency offset correction to each user signal. This segmentation allows the simple frequency domain processing structure to be maintained while correcting frequency offset effects for each user independently, resolving the contradiction between structural simplicity and reception quality.
Solution Approach 2:
The receiver performs preliminary frequency offset correction for each user signal before demodulation. By correcting the frequency offset in advance during the frequency domain processing stage, the system maintains its simplified structure while ensuring accurate reception quality, as the correction is integrated into the existing processing flow rather than adding separate correction stages.
2Reliability
If frequency offset correction is applied to each user signal, then reception quality is improved, but processing complexity increases
Solution Approach 1:
The frequency offset correction process is merged with the existing frequency domain processing pipeline. The correction is performed by multiplying each user signal by a complex exponential term generated from the estimated frequency offset, integrating the correction function into the demodulation process without requiring separate correction hardware or processing stages, thus avoiding increased processing complexity.
3Productivity
If all user signals are processed together in frequency domain, then calculation amount is reduced, but adjacent channel interference occurs due to frequency offsets
Solution Approach 1:
The receiver applies local frequency offset correction to each user signal individually based on their specific frequency offset characteristics. By tailoring the correction parameters to each user's local frequency conditions rather than applying a uniform processing approach, the system maintains calculation efficiency while eliminating adjacent channel interference caused by differential frequency offsets between users.
Data Source
AI summary
In a reception method and a receiver, a base station corrects a frequency offset contained in a reception signal from each user terminal and realizes excellent reception characteristics by using a simple receiver mechanism for performing frequency domain processing in a radio system using a frequency division multiplex (FDM) method. The base station includes: a DFT section that converts reception signals from a plurality of mobile stations communicating by radio communication using FDM all at once into the frequency domain; a demapping section that recognizes, from the frequency domain signals, user signals corresponding to respective mobile stations by using sub-carriers selected in association with respective mobile stations; a correction signal generation section generating a correction signal correcting a user signal frequency offset for each user signal; a frequency conversion section that corrects the frequency offset of the user signal by the correction signal; and a demodulation section that demodulates each of the corrected user signals.