Wireless Link Delay Asymmetry Detection for 5G Time Synchronization
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Solution Overview
Problem
Existing wireless communication systems face challenges in accurately detecting and compensating for asymmetric propagation delays, which lead to errors in time synchronization and positioning due to the assumption of symmetric uplink and downlink delays, particularly in 5G NR applications requiring high reliability and low latency.
Innovation Solution
A mechanism is introduced to detect propagation delay asymmetry by measuring round-trip time and time difference of arrival for wireless links, calculating a propagation delay asymmetry metric, and responding with actions such as adjusting beam pairs or obtaining time synchronization from different links to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If symmetric propagation delay assumption is used for time synchronization, then device complexity is reduced, but measurement precision deteriorates due to asymmetric delays in wireless channels
Solution Approach 1:
The patent replaces the conventional symmetric delay assumption (mechanical model) with electromagnetic signal-based measurements. By using multiple signal transmission directions and measuring actual propagation times through electromagnetic wave travel, the system directly measures asymmetric delays rather than assuming symmetry, thereby improving measurement precision while maintaining manageable complexity through standardized signal processing procedures
Solution Approach 2:
The patent introduces reference signals as intermediaries to measure propagation delays. These reference signals are transmitted between devices and network nodes, serving as mediators that carry timing information. By measuring the arrival times of these intermediary reference signals, the system can accurately determine asymmetric propagation delays without requiring direct complex calculations between end devices
2Measurement precision
If asymmetric propagation delay detection is implemented, then time synchronization accuracy is improved, but device complexity increases due to additional measurement and calculation requirements
Solution Approach 1:
The patent segments the propagation delay measurement process into multiple independent directional measurements. Instead of attempting to measure total round-trip delay as a single value, the system separates measurements into individual transmission directions (e.g., device to network, network to device) and calculates asymmetric delays by comparing these segmented measurements. This segmentation simplifies the overall complexity by breaking down a complex symmetric assumption into manageable directional components
Solution Approach 2:
The patent performs preliminary propagation delay measurements using reference signals before actual data transmission. By pre-measuring and storing asymmetric delay values through preliminary reference signal exchanges, the system prepares compensation parameters in advance, reducing the computational complexity during actual time synchronization operations and enabling faster real-time synchronization without repeated complex calculations
Data Source
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AI summary
A method includes determining a plurality of signal measurements including at least one of a round-trip time (RTT) measurement and a time difference of arrival (TDoA) measurement for one or more wireless links for the user device, including at least for a first wireless link; determining based on the plurality of signal measurements, a propagation delay asymmetry metric that estimates an amount of asymmetry between an uplink propagation delay and a downlink propagation delay for the first wireless link of the user device; and performing at least one of the following: sending a message to a control entity to report the propagation delay asymmetry metric for the first wireless link of the user device; or determining whether or not the first wireless link of the user device has an asymmetric propagation delay based on the propagation delay asymmetry metric for the first wireless link of the user device.