Doppler-Frequency Signal Transmission for High-Speed OFDM Links
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Solution Overview
Problem
Existing wireless communication systems face challenges in maintaining high demodulation performance for high-speed mobile users due to the fast time-varying characteristics of channels, particularly in scenarios involving orthogonal frequency division multiplexing (OFDM) waveforms.
Innovation Solution
A new waveform, orthogonal frequency-Doppler space (OFDM), is introduced by encoding bit data into a Doppler and frequency domain, transforming it into a time and frequency domain, and determining a transmittable signal to improve demodulation performance for high-speed mobile users.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If OFDM waveform is used for signal transmission, then low-speed mobile user demodulation performance is good, but high-speed mobile user demodulation performance deteriorates due to fast time-varying channel characteristics
Solution Approach 1:
The patent transforms the signal from the traditional time-frequency domain to a Doppler-frequency domain by introducing a Doppler dimension. This dimensional change allows the system to capture and exploit Doppler diversity, converting the harmful fast time-varying channel characteristics into useful signal features that improve demodulation performance for high-speed mobile users.
Solution Approach 2:
The patent changes the fundamental parameter of signal representation from time-domain to Doppler-domain. By rewriting the signal in terms of Doppler frequency components rather than traditional time samples, the system adapts to the fast time-varying channel characteristics of high-speed mobile scenarios, thereby improving demodulation performance.
2Device complexity
If traditional OFDM waveform is used, then signal transmission is simple, but Doppler diversity gain is insufficient for high-speed mobile users
Solution Approach 1:
The patent adds a Doppler dimension to the traditional time-frequency resource grid, creating a four-dimensional Doppler-frequency-time resource structure. This dimensional expansion enables the system to capture and exploit Doppler diversity, transforming the signal representation to inherently include multiple Doppler shifts that provide diversity gain for high-speed mobile users.
Solution Approach 2:
The patent segments the signal into distinct Doppler components and frequency components, allowing independent processing and optimization of each component. This segmentation enables the system to exploit Doppler diversity by treating different Doppler shifts as independent signal elements, thereby improving reliability without excessive complexity.
3Adaptability or versatility
If signal is transmitted in time-frequency domain, then existing OFDM systems are compatible, but interference from fast time-varying channels increases
Solution Approach 1:
The patent introduces a Doppler-domain transformation as an intermediary step between the traditional time-frequency domain and the final signal transmission. This intermediary transformation converts the harmful fast time-varying channel effects into manageable Doppler components, allowing the system to maintain compatibility with existing OFDM frameworks while mitigating channel interference through Doppler diversity.
Data Source
AI summary
The present application relates to the field of communications, and discloses a signal transmission method and apparatus, a terminal, and a storage medium. The signal transmission method in embodiments of the present application includes: encoding bit data to be transmitted to obtain a modulation signal corresponding to the bit data to be transmitted; writing the modulation signal into a first resource domain constructed by means of a Doppler dimension and a frequency dimension to obtain a modulation signal in the first resource domain; transforming the modulation signal in the first resource domain into a second resource domain constructed by means of a time dimension and a frequency dimension to obtain a modulation signal in the second resource domain; and determining a transmittable signal of the bit data to be transmitted on the basis of the modulation signal in the second resource domain.