Low-Complexity Precoding for Multi-User MIMO OTFS Networks
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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, leading to increased power consumption and reduced battery life in wireless communication systems.
Innovation Solution
Applying zero-forcing (ZF) and minimum mean square error (MMSE) precoding techniques in orthogonal time and frequency space (OTFS) networks, utilizing precoders, inverse symplectic finite Fourier transforms, and Heisenberg transforms to generate and transmit modified time domain signals, which reduce interference and conserve computing and networking resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDM waveforms are used for wireless communication, then high spectral efficiency is achieved, but high peak-to-average power ratio increases power consumption
Solution Approach 1:
The patent transforms the waveform representation from time-frequency domain (OFDM) to delay-Doppler domain (OTFS) by changing the fundamental parameters of signal representation. This parameter transformation reduces peak-to-average power ratio while maintaining spectral efficiency, directly resolving the contradiction between productivity and energy consumption
2Productivity
If OFDM waveforms are used, then data transmission is achieved, but sensitivity to frequency offset and Doppler shift reduces reliability
Solution Approach 1:
The patent introduces a new dimension by transforming signals from conventional time-frequency representation to delay-Doppler representation. This dimensional change makes the system inherently more robust to frequency offset and Doppler shift, as these effects become manageable parameters in the new domain rather than destructive interference sources
3Productivity
If OFDM waveforms are used, then communication is achieved, but complex synchronization requirements increase device complexity
Solution Approach 1:
By changing the fundamental parameters of waveform representation to delay-Doppler domain, the patent simplifies synchronization requirements. The OTFS modulation structure with its inherent delay-Doppler spreading provides natural robustness to timing and frequency offsets, reducing the complexity of synchronization algorithms needed
4Productivity
If OFDM waveforms are used, then signal transmission is achieved, but significant out-of-band emissions cause interference
Solution Approach 1:
The transformation to delay-Doppler domain representation fundamentally changes how spectral energy is distributed. The OTFS waveform structure in the new domain translates to more contained spectral emissions in the frequency domain, reducing out-of-band emissions and interference to adjacent channels while maintaining transmission capability
Data Source
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.