Multicarrier Signal Guard Interval Insertion
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Solution Overview
Problem
Advanced modulation systems like OFDM/OQAM face challenges in channel estimation due to imaginary interference, especially at high signal-to-noise ratios, and classic space/time encoding schemes are not applicable, leading to errors and loss in spectral efficiency due to the need for guard intervals.
Innovation Solution
The introduction of a guard interval with a length smaller than or equal to the delay spread in the transmission channel, specifically inserted before payload symbols, and the use of prototype functions with distinct filtering coefficients to modulate multicarrier signals, allowing for partial overlap of symbols and reducing inter-symbol interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a guard interval is introduced in classic OFDM to prevent inter-symbol interference, then reliability is improved, but spectral efficiency deteriorates due to loss of time
Solution Approach 1:
The patent changes the fundamental parameter of guard interval length from the conventional approach (where guard interval is necessary) to an advanced modulation system where the guard interval can be minimized or eliminated. By using modulations like OFDM/OQAM with prototype functions that provide better frequency localization, the system achieves inter-symbol interference prevention without the time loss associated with traditional guard intervals, thus resolving the contradiction between reliability and spectral efficiency
2Loss of time
If advanced modulation systems like OFDM/OQAM are used to improve spectral efficiency by eliminating guard intervals, then loss of time is reduced, but measurement precision deteriorates due to imaginary interference affecting channel estimation
Solution Approach 1:
The patent extracts and addresses the imaginary interference component separately from the main signal. By identifying and isolating the imaginary interference affecting channel estimation in advanced modulation systems, the invention enables accurate channel estimation even when guard intervals are minimized or eliminated, thus maintaining measurement precision while preserving spectral efficiency
Solution Approach 2:
The patent introduces intermediary processing steps to handle the imaginary interference. By using specific prototype functions and processing techniques that act as intermediaries between the modulated signal and channel estimation, the system can accurately estimate channels without being degraded by imaginary interference, resolving the contradiction between spectral efficiency and measurement precision
3Ease of operation
If classic space/time encoding schemes are applied to advanced modulation systems, then ease of operation is maintained, but reliability deteriorates due to incompatibility with modulations using distinct filtering coefficients
Solution Approach 1:
The patent changes the encoding approach from classic space/time encoding to encoding schemes specifically adapted for advanced modulations. By modifying the encoding parameters and methods to be compatible with modulations using distinct filtering coefficients, the system maintains ease of operation while significantly improving reliability and reducing error rates
Data Source
AI summary
A method is provided for transmitting a multiple-carrier signal. The method includes modulating data symbols representative of a data signal to be transmitted, which includes a filtering by at least one prototype function using at least two different filtering coefficients, thus providing a modulated signal including a time sequence of multiple-carrier symbols. A hold interval is inserted in front of at least one multiple-carrier symbol of the modulated signal, thus providing the multiple-carrier signal.