OFDM Demodulation Circuit Size Reduction via Correlation Segmentation
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Solution Overview
Problem
Existing OFDM demodulation apparatuses face challenges in efficiently detecting transmission modes due to large circuit sizes required for parallel detection methods and long detection times for serial methods, necessitating a solution that balances circuit size and detection speed.
Innovation Solution
A demodulation apparatus with a signal receiving unit, correlation units, and a detection unit that generates correlation signals and integrates them to detect the effective symbol and guard interval periods, allowing for automatic mode detection with reduced circuit size by eliminating the need for multiple delay/correlation calculation and integration units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a parallel type detection method is used to detect transmission modes, then the detection time is short, but the circuit size becomes large
Solution Approach 1:
The detection process is segmented into two distinct stages: a first correlation calculation stage that processes all received signals to generate correlation signals, and a second correlation calculation stage that processes only the generated correlation signals. This segmentation allows the system to achieve parallel-type detection speed while reducing circuit complexity by avoiding the need for multiple simultaneous delay/correlation units.
Solution Approach 2:
The first correlation calculation is performed preliminarily on all received signals before the second correlation calculation. By pre-processing the signals to generate correlation signals that already contain the necessary correlation information, the system eliminates the need for redundant delay/correlation calculation units in the second stage, thereby reducing circuit size while maintaining fast detection speed.
2Area of stationary object
If a serial type detection method is used to detect transmission modes, then the circuit size is small, but the detection time becomes long
Solution Approach 1:
The detection process maintains continuous useful action by performing correlation calculations in two sequential stages without idle periods. The first correlation calculation continuously processes received signals, and the second correlation calculation continuously processes the generated correlation signals, ensuring that the detection operation proceeds efficiently without wasting time while using a compact circuit structure.
3Measurement precision
If multiple delay/correlation calculation units are provided for each transmission mode, then the detection accuracy is high, but the device complexity increases
Solution Approach 1:
The first correlation calculation unit and the second correlation calculation unit are merged into a sequential processing pipeline. Instead of providing separate delay/correlation calculation units for each transmission mode simultaneously, the system merges the correlation calculation functions into two sequential stages, reducing device complexity while maintaining detection accuracy through the two-stage correlation process.
Solution Approach 2:
The first correlation calculation unit serves a universal function by processing all received signals regardless of the specific transmission mode, generating correlation signals that contain mode-specific information. This multi-functional unit replaces the need for mode-specific delay/correlation units, reducing device complexity while preserving detection accuracy.
Data Source
AI summary
An OFDM modulation apparatus receives a signal composed of OFDM symbols each of which is composed of an effective symbol and a guard interval, generates K delayed signals by delaying the received signal by K effective symbol periods, generates a signal by adding up all the K delayed signals, generates a first correlation signal that shows a correlation between the received signal and the addition-result signal, generates K×L second correlation signals from the first correlation signal, based on K×L combinations of K effective symbol periods and L fractions used to indicate the guard interval period, detects one among the K×L second correlation signals that indicates a largest correlation level, and detect periods of the effective symbol and the guard interval of the received signal in accordance with the detected second correlation signal.