OFDMA Receiver Non-Synchronous Signal Detection
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Solution Overview
Problem
Existing methods for receiving non-synchronous signals in OFDMA systems face challenges such as high complexity and difficulty in detecting signals with transmission delays greater than the cyclic prefix (CP) duration, particularly in frequency domain receiving methods, and require complex time domain filters in time domain receiving methods.
Innovation Solution
The method involves performing Fourier transform on a received time domain signal to obtain a frequency domain signal, setting the sub-carrier occupied by the non-synchronous signal to zero, and then performing inverse Fourier transform to subtract interference, thereby eliminating other bands and extracting the time domain received signal without the need for a time domain filter, simplifying the detection process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If frequency domain receiving method is used to detect non-synchronous signals, then detection capability is improved, but device complexity increases and signals with delay > CP duration cannot be detected
Solution Approach 1:
The patent segments the received signal processing into distinct stages: FFT transformation to frequency domain, selective sub-carrier zeroing to isolate non-synchronous signal components, and IFFT transformation back to time domain. This segmentation allows the system to handle different signal types (synchronous and non-synchronous) separately, enabling detection of signals with delay exceeding CP duration while managing complexity through modular processing steps.
Solution Approach 2:
The patent transforms the signal detection problem from the time domain to the frequency domain using FFT, processes the signal in the frequency dimension by zeroing specific sub-carriers, and then transforms back to time domain using IFFT. This dimensionality change enables the system to isolate and detect non-synchronous signals that would be difficult to separate in the time domain, particularly signals with delay greater than CP duration.
2Difficulty of detecting and measuring
If time domain filter is used to eliminate interference, then signal extraction is improved, but device complexity increases
Solution Approach 1:
The patent replaces the traditional time domain filter (mechanical/physical filtering system) with a frequency domain processing approach using FFT and IFFT transformations. Instead of using complex time domain filters to eliminate interference, the system transforms the signal to frequency domain, selectively zeroes out interfering sub-carriers, and transforms back to time domain. This substitution simplifies the interference elimination process while maintaining signal extraction capability.
3Adaptability or versatility
If cyclic shift is performed multiple times to cover maximum time delay, then detection range is improved, but processing time increases
Solution Approach 1:
The patent performs preliminary action by transforming the received signal to frequency domain using FFT before any detection operations. This preliminary transformation allows the system to identify and isolate non-synchronous signal components through selective sub-carrier zeroing, and then transform back to time domain using IFFT. By performing these transformations upfront, the system reduces the need for multiple iterative cyclic shifts, thereby reducing processing time while maintaining detection range.
Data Source
AI summary
A method and device for receiving a non-synchronous signal in an Orthogonal Frequency Division Multiple Access (OFDMA) system are provided. The method includes the following steps. Fourier transform is performed on a received first time domain signal to acquire a corresponding frequency domain signal. A sub-carrier occupied by a band of a non-synchronous signal to be received in the frequency domain signal is set to zero, inverse Fourier transform is performed on the frequency domain signal to acquire a second time domain signal, and the second time domain signal is subtracted from the first time domain signal. Or, the sub-carrier other than the sub-carrier occupied by the band of the non-synchronous signal to be received in the frequency domain signal is set to zero, and inverse Fourier transform is performed on the frequency domain signal to acquire a time domain received signal corresponding to the band of the non-synchronous signal.