DAS Downlink Time Alignment for Mixed RF and Digital Donors
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Solution Overview
Problem
In distributed antenna systems (DAS) using time division duplexing (TDD), radio frames from RF-interface and digital interface base stations arrive at radio units at different times, causing interference with neighboring radios due to desensitization, as RF-interface base stations cannot synchronize their frames with digital interface base stations.
Innovation Solution
A DAS is configured to time align contemporaneous TDD frames from digital and RF-interface base stations by determining and adjusting propagation delays in the DAS propagation paths, using delay adjustment circuits to synchronize the frame start times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If RF-interface base station uses wireless connection to couple to DAS, then ease of installation is improved, but time synchronization with digital interface base station deteriorates
Solution Approach 1:
The system performs preliminary measurement of propagation delays between the RF-interface base station and radio units during installation or initialization. These measured delay values are stored and later used by the delay adjustment circuit to compensate for timing differences, enabling synchronization without requiring complex real-time adjustment mechanisms.
Solution Approach 2:
A delay adjustment circuit is introduced as an intermediary component in the signal path from the RF-interface base station to the radio units. This circuit measures and adjusts the timing of downlink signals to align them with signals from digital interface base stations, thereby mediating the synchronization problem between different base station types.
2Device complexity
If propagation delay is not adjusted, then device complexity is reduced, but signal reception quality deteriorates due to interference
Solution Approach 1:
The delay adjustment circuit automatically measures propagation delays and adjusts signal timing without requiring manual configuration or external control. The system self-configures by detecting the timing differences between RF and digital base station signals and applying appropriate delays to achieve synchronization, thereby maintaining simplicity while improving reception quality.
3Manufacturing precision
If delay adjustment is implemented, then time alignment between base stations is improved, but device complexity increases
Solution Approach 1:
The system achieves time alignment by dynamically adjusting the timing parameter of downlink signals from RF-interface base stations. The delay adjustment circuit modifies the signal arrival time at radio units based on measured propagation delays, thereby aligning frames from different base station types without requiring changes to the fundamental system architecture or multiple complex components.
Data Source
AI summary
This invention relates to a DAS comprising a digital donor interface circuit, an RF donor interface circuit, a first DAS propagation path, a second DAS propagation path, and a radio unit and configured to obtain a first propagation time delay for the first DAS propagation path and a second propagation time delay for the second DAS propagation path, obtain at least one of a time delay of the RF donor interface circuit and the digital donor interface circuit, determine a first downlink time delay value, and transmit the first downlink time delay value to a delay adjustment circuit in a downlink path of the DAS.