Node Unit Delay Measurement and Compensation in Distributed Antenna Systems
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Solution Overview
Problem
In distributed transmission systems for mobile communication, such as distributed antenna systems, precise measurement and compensation of transmission delay are crucial for maintaining synchronized mobile communication services, especially in orthogonal frequency division multiplexing systems like LTE or WIBRO, but existing methods are inadequate for accurate delay equalization across node connections.
Innovation Solution
A node unit is introduced that measures and compensates for transmission delays by transmitting test signals, detecting loopback signals, and calculating summed delays across multiple stages, using a control unit to transmit compensation values and perform delay equalization, ensuring synchronized service times across the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a distributed antenna system is used to extend coverage, then service area is increased, but transmission delay variation increases
Solution Approach 1:
The patent applies preliminary action by measuring transmission delays and calculating compensation values before actual signal transmission. The headend unit determines compensation values for each node unit in advance, based on measured delays from test signals. This pre-calculated compensation is then applied to ensure synchronized signal transmission across all distributed antenna elements, resolving the delay variation issue while maintaining extended coverage.
2Measurement precision
If delay compensation is performed at each node unit, then delay equalization precision is improved, but system complexity increases
Solution Approach 1:
The patent merges the delay measurement and compensation functions into a centralized control architecture. The headend unit performs centralized delay measurement by sending test signals to node units and collecting loopback signals. Compensation values are calculated centrally at the headend unit and then distributed to respective node units for application. This centralized approach achieves precise delay equalization while avoiding the complexity of distributed measurement and compensation at each node unit.
3Measurement precision
If test signals are transmitted to measure delay, then delay measurement precision is improved, but transmission time is increased
Solution Approach 1:
The patent implements periodic action by transmitting test signals at specific intervals rather than continuously. The headend unit periodically sends test signals to node units to measure transmission delays, updates compensation values when necessary, and then resumes normal signal transmission. This periodic measurement approach maintains accurate delay compensation while minimizing the time lost to measurement activities, as the system only measures and updates when delay changes are likely to have occurred.
Data Source
AI summary
Provided is a node unit which is branch-connected to another communication node via a transport medium, the node unit comprising: a delay measurement unit which transmits a test signal for measuring a delay to an adjacent node unit of the branch-connected upper stage via the transport medium and detects a loopback signal to which the test signal is looped back via the adjacent node unit of the upper stage, thereby measuring an upper stage transmission delay between the adjacent node unit of the upper stage and the node unit; a delay summation unit which, when an adjacent node unit of the branch-connected lower stage exists, receives a lower stage transmission delay transmitted from the adjacent node unit of the lower stage, and calculates a summed transmission delay by summing the upper stage transmission delay and the lower stage transmission delay; and a control unit which transmits the summed transmission delay to the adjacent node unit of the upper stage.