Uplink Power Modulator Control for 256 QAM EVM Stability
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Solution Overview
Problem
Existing wireless communications devices face challenges in managing error vector magnitude (EVM) distortion during uplink signal transmission, particularly with high-order modulation schemes like 256 QAM, due to RF transient times exceeding cyclic prefix (CP) sizes, leading to decreased data throughput and increased power consumption.
Innovation Solution
The wireless communications device controls RF transient times by managing the output voltage of the supply modulator and optimizing power amplifier bias current using look-up tables (LUTs) tailored for 256 QAM, ensuring transient times remain within CP limits and minimizing EVM degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-order modulation schemes like 256 QAM are used to increase data throughput, then data throughput is improved, but EVM distortion increases due to RF transient times exceeding cyclic prefix sizes
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal supply modulator output voltage values in look-up tables before transmission. The processor queries these pre-prepared voltage values based on modulation order and resource allocation, eliminating the need for real-time calculation and ensuring that voltage control is ready in advance to prevent EVM distortion during high-order modulation transmission
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the supply modulator output voltage based on the modulation order and resource allocation information. Different voltage values are selected from look-up tables corresponding to different modulation schemes (e.g., 256 QAM, 64 QAM, 16 QAM), allowing the system to optimize EVM performance for each specific modulation parameter configuration
2Loss of time
If supply modulator output voltage is increased to reduce RF transient time, then RF transient time is reduced, but power consumption increases
Solution Approach 1:
The patent applies parameter changes by selecting from multiple discrete supply modulator output voltage values stored in look-up tables. Instead of continuously increasing voltage, the system chooses the most appropriate voltage level from pre-defined options that corresponds to the current modulation order and resource allocation, achieving RF transient time reduction while avoiding excessive power consumption through optimized voltage selection
Solution Approach 2:
The patent implements feedback by having the processor query look-up tables based on identified modulation order and resource allocation information to determine the appropriate supply modulator output voltage. This feedback mechanism ensures that voltage adjustments are made only when necessary and at optimal levels, preventing both excessive RF transient time and unnecessary power consumption
Data Source
AI summary
An operating method of a wireless communications device includes identifying a modulation order and resource allocation information of a first uplink signal transmitted in a first symbol and a second uplink signal transmitted in a second symbol preceding the first symbol, controlling a difference between a supply modulator output voltage value for the first uplink signal and a supply modulator output voltage value for the second uplink signal, based on the identified order or information, and transmitting the first uplink signal, based on the controlled difference between the supply modulator output voltage values.