Wireless Transmitter and Receiver LP-LFFT for High-Mobility Links
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Solution Overview
Problem
Conventional wireless communication systems face challenges in high-mobility scenarios due to increased overhead from pilot and guard symbols, leading to reduced spectral efficiency and performance metrics, particularly in channels with large Doppler frequency spread.
Innovation Solution
Implementing a linearly pre-coded layered Fast Fourier Transform (LP-LFFT) modulation that arranges data symbols in a two-dimensional array, applying FFT operations to achieve a transmit signal in the delay-Doppler domain while creating an intermediate-frequency domain with reduced overhead, enabling efficient pilot and data multiplexing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional OFDM waveforms are used with shorter symbols to compensate for mobility, then the system can operate in high-mobility scenarios, but spectral efficiency is reduced
Solution Approach 1:
The patent changes the fundamental parameter of the waveform from conventional OFDM to asymmetric OFDM (A-OFDM), which uses a layered-IFFT transformation. This parameter change enables the system to maintain spectral efficiency while improving robustness against Doppler frequency spread in high-mobility scenarios.
Solution Approach 2:
The patent introduces dynamic adaptability by allowing the receiver to employ a layered-FFT transformation that can process signals with varying Doppler characteristics. This dynamic processing enables the system to adapt to different mobility conditions without sacrificing spectral efficiency.
2Reliability
If asymmetric OFDM (A-OFDM) is used to reduce PAPR and improve robustness against Doppler spread, then reliability in mobility scenarios improves, but the receiver cannot detect data symbols in the delay-Doppler domain, losing full diversity gain
Solution Approach 1:
The patent implements a feedback mechanism where the receiver receives feedback information about the transmitted signal structure and employs the appropriate layered-FFT transformation to detect data symbols in the delay-Doppler domain. This feedback enables the system to recover the full diversity gain while maintaining the robustness benefits of A-OFDM.
3Reliability
If OTFS modulation is used to achieve better reliability performance in high-mobility scenarios, then data detection in delay-Doppler domain is enabled, but a relatively large number of null or guard symbols are required, increasing overhead
Solution Approach 1:
The patent applies partial action by using a reduced number of guard symbols compared to conventional OTFS. The layered-FFT transformation at the receiver enables efficient data detection with fewer guard symbols, achieving the necessary reliability performance while reducing the overhead burden.
4Reliability
If the number of guard symbols is increased to separate pilot and data symbols or prevent multi-user interference, then signal separation and interference reduction improve, but overhead increases
Solution Approach 1:
The patent introduces the layered-FFT transformation as an intermediary mechanism at the receiver. This transformation acts as a mediator that enables efficient separation of pilot and data symbols, and of signals from different users, with minimal guard symbols. The intermediary transformation provides the necessary signal separation capability without requiring excessive guard symbols.
Data Source
AI summary
The present disclosure relates to a transmitter device and a receiver device for a wireless communication system supporting low-overhead multiple access for a layered Fast Fourier Transform-based wireless communication. The transmitter device obtains a plurality of first data symbol matrices in a delay-Doppler domain for a plurality of users, a plurality of second data symbol matrices in an intermediate-frequency domain for the plurality of users, and an aggregated matrix in the intermediate-frequency domain for the plurality of users. The receiver device obtains an aggregated matrix in the intermediate-frequency domain for a plurality of users based on a signal received in a time domain from the transmitter device, a plurality of first data symbol matrices in the intermediate-frequency domain for the plurality of users, and a plurality of second data symbol matrices in the delay-Doppler domain for the plurality of users.