Radio Unit Downlink Gain Compensation with Predistortion Control
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Solution Overview
Problem
Existing downlink gain compensation methods in radio units are inefficient due to long gain estimation and compensation periods, errors in phase compensation, and instability caused by re-convergence of digital predistortion calculations, leading to degraded instantaneous performance.
Innovation Solution
A device and method incorporating a pre-distortion circuit, digital and analog gain adjusters, and gain controllers to dynamically adjust gains, with the pre-distortion circuit generating and applying pre-distortion to input signals, and digital and analog gain adjusters applying adjustable gains based on determined gain differences, allowing for faster and more accurate gain compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If software-based gain compensation is used, then gain adjustment capability is provided, but gain estimation period is long and instantaneous performance is degraded
Solution Approach 1:
The gain compensation function is segmented into two independent parts: a fast hardware-based analog compensation path using VVA for immediate gain adjustment, and a software-based digital compensation path using TGAs for fine-tuned adjustment. This segmentation allows the system to achieve both fast response and precise control, resolving the contradiction between gain adjustment capability and estimation time.
Solution Approach 2:
The patent introduces an intermediate hardware-based analog gain compensation mechanism (VVA) that acts as a mediator between the software control and the power amplifier. This intermediary provides fast gain adjustment without waiting for software-based estimation, thereby reducing the overall gain estimation period while maintaining adjustment capability.
2Measurement precision
If digital predistortion re-convergence is performed, then compensation accuracy is improved, but system stability is reduced
Solution Approach 1:
The patent applies preliminary analog gain compensation through VVA before digital predistortion re-convergence is triggered. This preliminary action pre-adjusts the gain to be close to the target value, reducing the magnitude of subsequent digital adjustments needed. As a result, the system maintains stability while still achieving accurate compensation, as the predistortion algorithm doesn't need to make large corrections that could cause oscillation.
Solution Approach 2:
The analog gain compensation mechanism serves as a cushioning layer before digital predistortion adjustments. By pre-compensating gain variations in the analog domain, the system reduces the stress on the digital predistortion algorithm, preventing instability that would otherwise occur during re-convergence while maintaining compensation accuracy.
3Speed
If analog gain adjuster is added, then gain adjustment speed is improved, but device complexity increases
Solution Approach 1:
The patent merges the analog gain adjustment function (VVA) with the existing digital gain adjustment architecture (TGAs). The analog and digital paths work together in a coordinated manner, sharing control signals and working towards the same gain compensation goal. This merging allows fast analog adjustment without significantly increasing overall system complexity, as the components are integrated into the existing RF signal path.
Data Source
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AI summary
Device and method are disclosed for downlink gain compensation at a radio unit. According to an embodiment, the device comprises a pre-distortion circuit, a digital gain adjuster, a gain determiner and a first gain controller. The pre-distortion circuit is configured to generate and apply a pre-distortion to an input signal. The digital gain adjuster is configured to apply an adjustable gain to an output signal from the pre-distortion circuit. The gain determiner is configured to determine a gain difference between a target downlink gain and current downlink gain. The first gain controller is configured to control the digital gain adjuster based on the gain difference. A radio unit comprising the device is also disclosed.