OFDM Automatic Gain Control Using SR-Based Reference Power
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Solution Overview
Problem
Conventional OFDM systems face challenges in minimizing bit error rate (BER) due to variations in reference power, which affect the overall performance of the system.
Innovation Solution
An automatic gain control (AGC) device and method that generates a reference power based on a saturation-to-RMS (SR) ratio of 4.0σ, using a variable gain amplifier, energy calculator, truncator, subtracter, and RC filter to control the gain and minimize BER.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional AGC process is used with fixed reference power, then the AGC device can control gain, but the bit error rate increases due to reference power variations
Solution Approach 1:
The patent applies dynamics by making the reference power variable rather than fixed. The AGC device dynamically adjusts the reference power based on the saturation-to-RMS ratio calculated from the input signal characteristics, allowing the system to adapt to different signal conditions and minimize BER for each specific case.
Solution Approach 2:
The patent changes the parameter of reference power from a fixed value to a dynamically calculated value based on the saturation-to-RMS ratio. By calculating this ratio from the input signal and using it to set the reference power, the system optimizes performance for varying signal conditions, directly addressing the BER issue caused by fixed reference power.
2Reliability
If the AGC device controls gain using conventional methods, then the processing is simple, but the overall system performance deteriorates due to reference power variations
Solution Approach 1:
The patent applies preliminary action by calculating the saturation-to-RMS ratio and setting the optimal reference power before the main AGC gain control process. This preliminary setup ensures that subsequent gain control operations use the correct reference power, improving overall system performance without significantly increasing the complexity of the main AGC loop.
Solution Approach 2:
The patent implements feedback by using the calculated saturation-to-RMS ratio to adjust the reference power, which then feeds back into the AGC decision-making process. This closed-loop approach ensures that the reference power is continuously optimized based on actual signal characteristics, improving reliability while maintaining manageable complexity through systematic feedback control.
Data Source
AI summary
Disclosed is an automatic gain control device in an orthogonal frequency division multiplexing system. A variable gain amplifier controls a gain of an input signal; an energy calculator calculates an energy of the input signal; a truncator accumulates the calculated energies, finds an average thereof, and generates a DC offset of the input signal; a subtracter subtracts a predefined reference value from the DC offset, and outputs a signal; and an RC filter feeds the value output by the subtracter back to the variable gain amplifier so that the value output by the subtracter may be used for an automatic gain control. The predefined reference value given to be 4.Ov is a reference power generated based on a saturation to RMS ratio for minimizing the bit error rate of the orthogonal frequency division multiplexing system.