Low PAPR Precoded Reference Signal Design for MIMO Transmissions
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Solution Overview
Problem
In wireless communication systems, the multiplexing of multiple reference signal streams for MIMO transmissions often results in high peak-to-average power ratio (PAPR), which can lead to reduced throughput and amplifier distortion, especially when using frequency division multiplexing (FDM) on a single antenna.
Innovation Solution
The technique involves multiplexing reference signal streams in the time domain using time division multiplexing (TDM) before mapping them to subcarriers of a DFT-s-OFDM waveform, ensuring that the streams are mapped to orthogonal or pseudo-orthogonal time intervals, thereby reducing the PAPR of the uplink transmission to be comparable to that of a single-carrier waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple reference signal streams are multiplexed using frequency division multiplexing (FDM) on a single antenna, then the system supports MIMO transmissions with multiple streams, but the peak-to-average power ratio (PAPR) of the uplink transmission increases
Solution Approach 1:
The patent inverts the conventional FDM approach by using time division multiplexing (TDM) instead. Multiple reference signal streams are transmitted in different time slots rather than different frequency subcarriers, which maintains MIMO capability while preserving low PAPR characteristics of single-carrier waveforms
Solution Approach 2:
The patent changes the multiplexing domain parameter from frequency (FDM) to time (TDM). This parameter change allows the system to maintain multiple stream transmission capability while keeping the waveform characteristics that result in low PAPR, specifically by transmitting single-carrier waveforms in sequential time slots
2Productivity
If multiple reference signal streams are multiplexed for uplink transmission, then the system achieves higher data throughput, but amplifier distortion increases due to high PAPR
Solution Approach 1:
Instead of using FDM which causes high PAPR and amplifier distortion, the patent applies TDM to transmit multiple streams sequentially in time. This inversion of the multiplexing approach maintains high throughput by supporting multiple streams while avoiding the PAPR-related amplifier distortion that plagues FDM-based MIMO transmissions
Solution Approach 2:
The patent employs periodic time-division multiplexing where reference signal streams are transmitted in periodic time slots. This periodic structure allows the power amplifier to operate in a more linear region by avoiding the simultaneous transmission of multiple high-PAPR signals, thereby reducing amplifier distortion while maintaining throughput
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AI summary
Methods, systems, and devices for wireless communication are described that support a low peak-to-average power ratio (PAPR) precoded reference signal design for multiple-input, multiple-output (MIMO) transmissions. A user equipment (UE) may identify multiple sets of symbols associated with different reference signal waveforms, where each reference signal waveform may be associated with a low PAPR. In some cases, different single-carrier reference signal waveforms may be mapped to subsets of frequency resources through frequency division multiplexing (FDM) for a transmission on a single antenna. However, the addition of single-carrier waveforms through FDM for a transmission via an antenna may result in an uplink transmission having a high PAPR (e.g., as compared to single-carrier waveforms). The UE may reduce the PAPR of the uplink transmission by multiplexing the reference signal waveforms in the time domain (e.g., using time division multiplexing (TDM)).