Digital Filter in Remote Unit for WDS Noise Suppression
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Solution Overview
Problem
Distributed antenna systems (DAS) face challenges in reducing out-of-channel noise, which leads to non-compliance with spectrum emission masks, due to amplified energy leaking beyond predefined bandwidths and interference from analog components in downlink digital communications signals.
Innovation Solution
Implementing digital filtering in remote units of the DAS, configured based on physical characteristics of the downlink digital communications signals, to suppress out-of-channel noise before amplification and distribution, thereby ensuring compliance with spectrum emission masks without the need for central unit digital filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital filtering is implemented in the central unit to suppress out-of-channel noise, then signal quality and SEM compliance are improved, but device complexity and power consumption increase
Solution Approach 1:
The patent divides the filtering function into two parts: coarse filtering is performed in the central unit, while fine filtering is performed in the remote units. This segmentation allows the central unit to reduce complexity by not performing all filtering operations, while still achieving SEM compliance through the combined filtering effect at multiple levels in the signal chain.
2Reliability
If digital filtering is implemented in the central unit to suppress out-of-channel noise, then signal quality and SEM compliance are improved, but power consumption increases
Solution Approach 1:
The filtering operation is segmented between the central unit and remote units. The central unit performs initial coarse filtering which reduces the out-of-channel noise significantly, and then the remote units perform additional filtering. This segmentation reduces the computational burden and power consumption in the central unit while still achieving the required SEM compliance through the combined filtering effect.
3Device complexity
If no digital filtering is implemented in the central unit, then device complexity and power consumption are reduced, but out-of-channel noise is amplified leading to non-compliance with spectrum emission masks
Solution Approach 1:
The central unit performs preliminary coarse filtering before transmitting the signal to remote units. This preliminary action reduces the out-of-channel noise content in the transmitted signal, preventing excessive noise amplification in subsequent stages. The filtering is performed in advance at the central unit, but only to the extent needed to prevent harmful noise levels, maintaining simplicity while ensuring compliance.
Solution Approach 2:
Different filtering characteristics are applied at different locations in the system. The central unit applies coarse filtering with specific characteristics suitable for the overall signal, while remote units apply additional filtering with characteristics optimized for local requirements. This local quality differentiation allows each unit to have simplified design while the combined system achieves SEM compliance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces complexity, cost, and power consumption in the central unit while ensuring amplified RF communications signals comply with regulatory standards, improving signal quality and reducing interference.
Implementation Method 1
The digital filter is configured to output a modified downlink digital communications signal based on the downlink digital communications signal and at least one filter configuration parameter received from a control circuit to suppress out-of-channel noise in the downlink digital communications signal
Implementation Method 2
A digital-to-analog converter (DAC) is configured to convert the modified downlink digital communications signal into a downlink RF communications signal
Implementation Method 3
A power amplifier is configured to generate an amplified downlink RF communications signal based on the downlink RF communications signal for communication to one or more client devices in the WDS
Data Source
AI summary
Embodiments of the disclosure relate to reducing out-of-channel noise in a wireless distribution system (WDS). A digital filter in a remote unit is configured to suppress out-of-channel noise in a downlink digital communications signal based on at least one filter configuration parameter received from a control circuit. The control circuit is configured to determine the filter configuration parameter based on physical characteristics of the downlink digital communications signal. By suppressing the out-of-channel noise of the downlink digital communications signal, it is possible to provide a downlink RF communications signal communicated from the remote unit that complies with a spectrum emission mask (SEM). Further, by suppressing the out-of-channel noise at the remote unit, it is not necessary for a central unit to perform digital filtering before distributing the downlink digital communications signal to the remote unit, thus helping reduce complexity, cost, physical size, and power consumption of the central unit.