Crest Factor Reduction via Cancellation Pulses
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Solution Overview
Problem
Wireless communication systems face reduced throughput due to high peak-to-average power ratio (PAPR) in single carrier FDMA or OFDMA transmissions, which can be exacerbated in highly occupied frequency spectrums.
Innovation Solution
The described techniques involve sampling an input signal to identify signal windows where peak amplitudes exceed a threshold, applying a series of cancellation pulses based on the signal's characteristics, such as its envelope or phase, to reduce the amplitude below the threshold, and transmitting the resulting reduced signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If cancellation pulses are applied to reduce peak amplitudes, then PAPR is reduced, but signal distortion increases
Solution Approach 1:
The signal processing is divided into multiple stages: initial peak reduction through cancellation pulses, followed by iterative refinement. Each stage addresses specific amplitude excursions, segmenting the overall PAPR reduction process into manageable steps that progressively reduce peaks while monitoring signal quality
Solution Approach 2:
The system employs feedback mechanisms where the reduced signal is monitored for residual peaks and distortion. Based on this feedback, additional cancellation pulses are selectively applied only when necessary, adjusting the processing level to maintain signal fidelity while achieving PAPR reduction targets
2Loss of energy
If multiple cancellation pulses are applied iteratively, then PAPR reduction is improved, but computational complexity increases
Solution Approach 1:
Instead of applying excessive processing to all signals uniformly, the system applies cancellation pulses partially and selectively only when peak amplitudes exceed thresholds. The iterative process performs partial actions in each stage, refining only the necessary portions of the signal to achieve adequate PAPR reduction without unnecessary computational overhead
Solution Approach 2:
The system performs preliminary PAPR reduction in early processing stages using cancellation pulses, addressing the most significant peaks before further signal processing. This preliminary action reduces the burden on subsequent processing stages, lowering overall computational complexity while achieving effective PAPR control
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. The described methods, systems, and devices may include sampling an input signal to obtain one or more signal windows. An amplitude of a first sample within a first signal window of the one or more signal windows may be determined to exceed an amplitude threshold. A series of cancellation pulses may be combined with the first sample within the first signal window to obtain a reduced signal, the reduced signal including one or more reduced samples each having an amplitudes within the amplitude threshold. The series of cancellation pulses may be based on a characteristic of the first sample. The reduced signal may then be transmitted. The series of cancellation pulses may be based on, for example, an envelope of the first sample. In some cases, the series of cancellation pulses may be based on a phase of the first sample.