Resource Block Extraction via Segmented FFT Processing
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Solution Overview
Problem
In LTE wireless communication systems, the conventional method for extracting the random access channel (RACH) preamble from a signal using a super Fast Fourier Transformation (FFT) results in high calculation complexity and long processing delays, which are inefficient and resource-intensive.
Innovation Solution
The method involves removing the cyclic prefix (CP) from the signal and performing a series of symbol-level Fast Fourier Transformations (FFTs) on successive symbols, followed by Inverse FFTs to extract frequency domain signals, which are then concatenated and transformed back into time domain signals to extract subcarriers corresponding to the resource block, reducing the need for large storage and lowering calculation complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a super FFT is performed on the 1 ms RACH signal to extract the preamble, then the preamble extraction is achieved, but the calculation complexity and processing delay increase significantly
Solution Approach 1:
The patent segments the 1 ms RACH signal into multiple shorter time segments (e.g., 3 segments of 33.33 μs each). Instead of performing a single super FFT on the entire 1 ms signal, the method performs separate FFT operations on each segmented portion, then combines the results. This segmentation reduces the computational complexity from O(N log N) where N is the total number of samples in 1 ms, to multiple operations where each operates on N/k samples, significantly lowering the overall calculation burden while maintaining extraction accuracy.
2Measurement precision
If a super FFT is performed on the 1 ms RACH signal to extract the preamble, then the preamble extraction is achieved, but the processing delay increases
Solution Approach 1:
By dividing the 1 ms RACH signal into multiple shorter segments and performing FFT on each segment separately, the patent reduces the processing delay. Each segment is processed independently and more quickly, and the results are combined to achieve the same preamble extraction accuracy as a full super FFT would provide, thereby reducing the overall processing time.
Solution Approach 2:
The patent performs preliminary processing by segmenting the signal and performing FFT operations on individual segments before combining them. This preliminary action on smaller data portions allows for faster computation and reduces the overall processing delay compared to waiting to process the entire 1 ms signal in a single super FFT operation.
3Measurement precision
If a super FFT is performed on the 1 ms RACH signal, then the resource block extraction is achieved, but the storage requirements increase
Solution Approach 1:
The patent segments the RACH signal into multiple time portions and performs FFT on each segment separately. This segmentation means that the base station only needs to store and process one segment at a time rather than the entire 1 ms signal simultaneously. The storage requirements are reduced from needing to hold all N samples in memory to only holding N/k samples for each FFT operation, where k is the number of segments.
Data Source
AI summary
The embodiments disclose a method in a base station for extracting a resource block at a frequency band from a signal received from a terminal device in a radio communication system employing OFDM. The method comprising: removing a CP portion corresponding to the resource block from the signal; for each of a predetermined number of successive symbols in the signal after the CP portion corresponding to the resource block has been removed, performing a FFT of the symbol, extracting a frequency domain signal corresponding to the frequency band from the FFT of the symbol, performing an IFFT on the extracted frequency domain signal to yield a time domain signal, and storing the time domain signal to form a time sequence by concatenation; performing a FFT of the stored time sequence; and extracting subcarriers corresponding to the resource block from the FFT of the stored time sequence.