OFDM Control Signal Placement for Modulation Error Correction
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Solution Overview
Problem
In radio communication systems, there is a risk of incorrect determination of modulation method and error correction method due to noise and propagation path fluctuations, leading to reduced communication quality.
Innovation Solution
The solution involves transmitting modulation method and error correction method information signals at discrete locations within the same frame, using adaptive switching based on propagation path conditions, and employing BPSK or QPSK modulation for high error tolerance, allowing accurate estimation even under fading conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If modulation method and error correction method information are transmitted using high-order modulation (64 QAM), then transmission efficiency is improved, but error rate increases due to noise and propagation path fluctuations
Solution Approach 1:
The patent changes the modulation parameter for control information from high-order modulation (64 QAM) to low-order modulation (BPSK or QPSK). This parameter change ensures that control information can be transmitted reliably even under poor propagation conditions, while the data information continues to use high-order modulation for efficiency.
Solution Approach 2:
The patent segments the transmission frame into different portions: control information (modulation method and error correction method) is separated from data information. The control information is transmitted using BPSK or QPSK modulation at discrete locations, while data information uses 64 QAM modulation. This segmentation allows each type of information to be transmitted with appropriate modulation characteristics.
2Loss of information
If control information is transmitted at every symbol position, then completeness is improved, but vulnerability to fading increases
Solution Approach 1:
The patent applies local quality by transmitting control information at specific discrete locations (e.g., first and second symbol positions) rather than uniformly across all symbol positions. The control information is placed at locations where it can be reliably received even under fading conditions, while data information fills the remaining positions.
Solution Approach 2:
The patent provides beforehand cushioning by using BPSK or QPSK modulation for control information, which has lower error rate characteristics. This cushioning ensures that even if fading occurs, the control information can still be decoded correctly, preventing complete loss of communication.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures correct determination of modulation and error correction methods on the receiving side, thereby improving communication quality by reducing errors and maintaining signal integrity during propagation path fluctuations.
Implementation Method 1
transmitting signals indicating the modulation method and error correction method used by the transmitting side arranged at discrete locations within the same frame
Implementation Method 2
employing BPSK or QPSK modulation for high error tolerance
Implementation Method 3
A receiving apparatus receives and demodulates a signal transmitted by the transmitting apparatus
Data Source
AI summary
An orthogonal frequency division multiplexing transmission method includes generating a data symbol. A control information signal is generated. The control information signal relates to a modulation scheme and an error correction scheme of a data symbol in a frame. An orthogonal frequency division multiplexing signal is formed. The orthogonal frequency division multiplexing signal includes the data symbol and the control information signal. The orthogonal frequency division multiplexing signal is formed by arranging the control information signal in a first symbol group that is formed with subcarriers in a time period, and in a second symbol group that is formed with subcarriers, located in the time period, and that has a frequency band distant from the first symbol group.