Digital Repeater Filter Tuning for Multipath Delay and Gain
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Solution Overview
Problem
High-speed train environments present challenging RF conditions due to varying outdoor signal levels and multipath propagation, leading to dropped connections and reduced data throughput, and existing solutions either increase cyclic prefix to reduce dropped calls at the cost of throughput or fail to optimize signal delay and gain settings effectively.
Innovation Solution
A digital repeater system with configurable digital filters and gain control, adjusting filter coefficients based on network conditions to optimize group delay and gain settings, ensuring high data throughput while minimizing dropped calls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cyclic prefix is increased to reduce dropped calls caused by multipath propagation, then call reliability is improved, but data throughput is reduced
Solution Approach 1:
The patent applies dynamics by making the cyclic prefix length adjustable rather than fixed. The system dynamically adapts the CP length based on detected multipath delay spread conditions, using longer CP only when necessary to maintain call reliability while preserving data throughput in conditions where shorter CP is sufficient.
Solution Approach 2:
The patent changes the parameter of cyclic prefix length based on channel conditions. By measuring multipath delay spread and adjusting CP length accordingly, the system optimizes the balance between call reliability and data throughput, avoiding the permanent throughput reduction that would result from a consistently long CP.
2Reliability
If digital filtering is applied to reduce multipath interference, then signal quality is improved, but signal delay increases
Solution Approach 1:
The patent makes the filter characteristics dynamic by adjusting filter coefficients based on detected signal conditions. The system adapts the digital filter's impulse response to match the actual multipath channel characteristics, optimizing signal quality while minimizing unnecessary delay introduced by filtering.
Solution Approach 2:
The patent implements feedback by detecting multipath delay spread and using this information to configure the digital filter parameters. The system continuously monitors channel conditions and adjusts filter coefficients accordingly, creating a closed-loop system that optimizes the balance between signal quality and delay.
Data Source
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AI summary
A digital repeater system for repeating RF signals can include a receiving section for receiving an RF input signal that includes a frequency band with at least one subband associated with a communication channel of a telecommunications network. The receiving section can digitize the RF input signal to obtain a digital signal. A filter device includes a digital filter with a passband for filtering the digital signal. The digital filter is configurable by setting filter coefficients. A gain control device can set the gain of at least a portion of the digital signal. A transmitting section can transmit an RF output signal and can convert the digital signal to the RF output signal for transmission. A control unit can configure the filter coefficients of the digital filter based on the gain setting of the gain control device.