Low-Complexity Multi-User OTFS Precoding for High-Doppler MIMO
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Solution Overview
Problem
Existing OFDM waveforms face challenges such as high peak-to-average power ratio, sensitivity to frequency offset and Doppler shift, complex synchronization requirements, significant out-of-band emissions, and reduced spectral efficiency in environments with delay spread, leading to increased power consumption and reduced battery life.
Innovation Solution
Applying zero forcing and minimum mean square error precoders in orthogonal time and frequency space (OTFS) networks, utilizing inverse symplectic finite Fourier transforms and Heisenberg transforms to generate and transmit modified time domain signals with cyclic prefixes, enabling efficient beamforming techniques in multi-user multi-input multi-output systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDM waveforms are used for communication, then spectral efficiency is achieved, but power consumption increases and battery life reduces due to high peak-to-average power ratio
Solution Approach 1:
The patent transforms the communication waveform from time-frequency domain (OFDM) to delay-Doppler domain (OTFS) by changing the fundamental parameter space. This parameter transformation allows the system to maintain spectral efficiency while reducing peak-to-average power ratio, thereby lowering power consumption and extending battery life in high mobility scenarios
Solution Approach 2:
The patent introduces a new dimension by operating in the delay-Doppler domain rather than the traditional time-frequency domain. This dimensional change enables the system to handle high Doppler shifts more efficiently, maintaining communication performance while reducing power consumption through more efficient signal representation
2Productivity
If OFDM waveforms are used, then data transmission is achieved, but sensitivity to frequency offset and Doppler shift degrades performance
Solution Approach 1:
The patent changes the domain of operation from time-frequency to delay-Doppler, which fundamentally alters how the system responds to frequency offset and Doppler shift. In the delay-Doppler domain, these effects become more manageable, allowing reliable data transmission even in high mobility environments where traditional OFDM fails
Solution Approach 2:
The patent converts the harmful effect of Doppler shift into a beneficial feature by operating in the delay-Doppler domain. Instead of treating Doppler shift as interference to be eliminated, the system exploits the Doppler domain structure to improve signal detection and maintain reliable communication in high mobility scenarios
3Measurement precision
If synchronization requirements are made complex to improve accuracy, then measurement precision increases, but device complexity increases
Solution Approach 1:
The patent simplifies synchronization by changing the domain in which synchronization is performed. By operating in the delay-Doppler domain, the system achieves accurate timing and frequency synchronization with reduced complexity, as the structure of the OTFS waveform naturally provides better synchronization properties compared to OFDM
4Reliability
If OFDM is used in environments with delay spread, then communication is maintained, but spectral efficiency reduces due to inter-carrier interference
Solution Approach 1:
The patent transforms the signal representation from time-frequency to delay-Doppler domain, which fundamentally changes how delay spread affects the system. In the delay-Doppler domain, delay spread becomes a more manageable parameter, allowing the system to maintain high spectral efficiency even in multipath environments where OFDM suffers from inter-carrier interference
Data Source
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AI summary
A device may apply a precoder to input information symbols to generate delay-Doppler (DD) domain symbols, and may utilize an inverse symplectic finite Fourier transform to transform the DD domain symbols into a time-frequency (TF) domain signal. The device may utilize a Heisenberg transform to convert the TF domain signal to a time domain signal, and may add a cyclic prefix to the time domain signal to generate a modified time domain signal. The device may transmit the modified time domain signal to at least one user equipment.