Low PAPR Waveform Design via Time-Frequency Multiplexing
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Solution Overview
Problem
Wireless communication systems face increased peak-to-average power ratio (PAPR) when multiplexing multiple streams, leading to reduced throughput and coverage, particularly in power-limited situations where UEs must back off transmission power to avoid distortion from high PAPR signals.
Innovation Solution
Implementing frequency and time domain multiplexing techniques, where multiple sets of symbols associated with different streams are mapped to subsets of time intervals and transformed using discrete Fourier transform (DFT) and inverse DFT (IDFT) processes, allowing for efficient reduction of PAPR by aligning time domain waveforms and maintaining properties similar to single-carrier waveforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple streams are multiplexed using frequency division multiplexing (FDM), then the data transmission capacity is improved, but the peak-to-average power ratio (PAPR) increases
Solution Approach 1:
The patent segments the time domain resources by dividing the symbol period into multiple time intervals, with each stream assigned to specific time intervals. This time domain segmentation prevents the simultaneous addition of multiple single-carrier waveforms, thereby reducing PAPR while maintaining data transmission capacity through frequency division multiplexing.
Solution Approach 2:
The patent implements periodic time division multiplexing where different streams are transmitted in alternating time intervals within the symbol period. This periodic allocation ensures that single-carrier waveforms are transmitted sequentially rather than simultaneously, maintaining low PAPR characteristics while achieving multi-stream data transmission.
2Productivity
If multiple single-carrier waveforms are added through frequency division multiplexing, then the transmission throughput is improved, but the PAPR becomes larger
Solution Approach 1:
The patent segments time domain resources into multiple intervals and assigns different streams to different intervals. This segmentation prevents the constructive addition of multiple single-carrier waveforms at the same time, thereby controlling PAPR while maintaining high transmission throughput through frequency division multiplexing of multiple streams.
Solution Approach 2:
The patent performs preliminary time domain mapping before frequency domain transformation, assigning specific time intervals to each stream. This preliminary arrangement ensures that when multiple streams are multiplexed in the frequency domain, their time domain representations do not overlap, preventing PAPR increase while maintaining throughput.
3Reliability
If transmission power is reduced to avoid distortion from high PAPR signals, then the PAPR distortion is avoided, but the communication range is reduced
Solution Approach 1:
The patent converts the harmful effect of high PAPR into a benefit by using time division multiplexing to maintain low PAPR characteristics. This allows the system to transmit at full power without distortion, thereby maintaining both signal quality and communication range, as the low PAPR waveforms do not require power backoff.
Data Source
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AI summary
Methods, systems, and devices for wireless communications are described that support frequency and time domain multiplexing for low peak-to-average waveforms with multiple streams. A user equipment (UE) may identify sets of symbols associated with different streams (e.g., multiple single-carrier discrete Fourier transform (DFT)-spread waveforms), where each stream may be associated with a low peak-to-average power ratio (PAPR). In some cases, different waveforms may be mapped to subsets of frequency resources through frequency division multiplexing (FDM). The UE may further reduce the PAPR of the multiplexed waveforms by performing time division multiplexing (TDM) across the single-carrier streams, and sets of symbols that are not used by one waveform may be used by another waveform. Frequency domain phase ramps may be applied to align the multiplexed waveforms. Signals included in an uplink transmission according to these techniques may maintain properties similar to single-carrier waveforms, including a low PAPR.