Transmitter Power Back-Off Estimation for Stable ACLR
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Solution Overview
Problem
The 3GPP standard's method for calculating power reduction in transmitters for digital wireless communications systems is inaccurate, leading to degraded performance in user equipment due to insufficient consideration of varying modulation configurations and operating conditions, making it difficult to achieve consistent Adjacent Channel Leakage power Ratio (ACLR) across different configurations.
Innovation Solution
The method calculates power reduction by combining modulation-dependent data, including higher-order products, with transmitter-dependent data, using RMS values of third, fifth, and seventh order products, and coefficients determined through simulations or measurements, allowing for accurate estimation and adaptation to different operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the 3GPP standard's cubic metric method is used to calculate power reduction, then the calculation is simple, but the accuracy of power reduction estimation is poor
Solution Approach 1:
The patent changes the parameters used in the calculation from only third-order products to include higher-order products (fifth, seventh, and ninth orders). This parameter expansion improves the accuracy of power reduction estimation while maintaining a systematic calculation approach that balances complexity and precision.
2Reliability
If the maximum back-off is changed frequently to adapt to different modulation configurations, then the ACLR performance can be optimized, but the computational resources and complexity increase
Solution Approach 1:
The patent pre-calculates and stores the relationship between modulation configurations and required back-off levels in lookup tables during the design phase. During operation, the system simply queries these pre-computed tables based on the current modulation configuration, avoiding frequent complex calculations while maintaining optimal ACLR performance adaptation.
Solution Approach 2:
The patent creates simplified representations of the complex back-off calculation relationships by storing pre-computed data in lookup tables. These tables serve as copies of the full computational model, allowing fast retrieval of appropriate back-off values without executing the complete higher-order product calculations in real-time.
3Ease of operation
If the standard's Maximum Power Reduction is used, then implementation is straightforward, but it does not account for specific transmitter components and operating conditions
Solution Approach 1:
The patent introduces transmitter-specific parameters and operating condition-dependent coefficients into the back-off calculation. Different transmitter components (power amplifiers, modulators) and operating conditions (temperature, load) have their own characteristic parameters that are incorporated into the calculation, allowing each transmitter to be optimized for its specific characteristics rather than using a universal standard value.
Data Source
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AI summary
A level of power reduction for a transmitter arranged to transmit signals modulated according to one of a number of modulation configurations via radio channels in a digital wireless communications system is estimated. Modulation dependent data comprising a term calculated from a third order product of a signal modulated according to a modulation configuration are provided, and a power reduction estimate for transmission of signals modulated according to said modulation configuration is calculated (307) there from. The modulation dependent data are provided (305) to comprise, in addition to the term calculated from a third order product, at least one term calculated from a higher order product. Further, transmitter dependent data are provided (306), and the estimate is calculated from said modulation dependent and transmitter dependent data. Thus a more accurate method of determining a power reduction is achieved, which also allows different operating conditions for the transmitter to be considered.