Mobile IAB Frequency Synchronization via Propagation Delay Estimation
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Solution Overview
Problem
Existing technologies for mobile integrated access backhaul (IAB) deployments face challenges in accurately synchronizing frequency and timing, especially when IAB nodes are moving and propagation delays vary, due to the complexity of separating frequency offsets caused by Doppler and local clock errors.
Innovation Solution
The proposed solution involves estimating changes in propagation delay at two time instants, measuring the time period using a local clock, subtracting the propagation delay change, calculating the difference with known timing, and converting this to a frequency offset value to synchronize downlink transmission frequency between the IAB node and its parent node. This method also considers information signaled from the parent node to adjust timing references and separate Doppler and local clock offset effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing frequency synchronization methods are used in mobile IAB deployments, then the system is simpler to implement, but frequency and timing synchronization accuracy deteriorates when IAB nodes are moving
Solution Approach 1:
The patent segments the frequency offset into two distinct components: Doppler frequency offset (caused by node movement) and local clock frequency offset (caused by clock inaccuracies). By separating these effects, the system can apply different compensation strategies for each component, improving overall synchronization accuracy while managing complexity through structured analysis
Solution Approach 2:
The patent introduces reference signals as an intermediary mechanism to enable the IAB node to estimate and compensate for frequency offsets. These reference signals serve as a mediator between the parent node and IAB node, allowing the moving node to accurately measure and correct frequency deviations without requiring complex direct coordination
2Measurement precision
If frequency offset compensation is applied without separating Doppler and local clock effects, then the synchronization process is simpler, but synchronization accuracy deteriorates in mobile scenarios
Solution Approach 1:
The patent performs preliminary estimation of the Doppler frequency offset using known reference signals before final frequency synchronization. By pre-characterizing the Doppler effect based on reference signal measurements, the system prepares compensation data in advance, making the final synchronization more accurate and reducing the difficulty of real-time frequency offset separation
Solution Approach 2:
The patent implements a feedback mechanism where the IAB node continuously estimates frequency offsets using reference signals from the parent node, calculates the separation between Doppler and local clock effects, and adjusts its transmission frequency accordingly. This closed-loop feedback enables accurate frequency offset separation and compensation in mobile scenarios
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 enables accurate IAB synchronization in mobile scenarios, maintaining network synchronization across various velocities and ensuring precise timing and frequency adjustments, thereby enhancing the reliability and efficiency of IAB networks.
Implementation Method 1
separating frequency offsets caused by Doppler and local clock errors
Data Source
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AI summary
Implementations of advanced frequency synchronization in a mobile integrated access backhaul deployment are disclosed. An apparatus includes at least one processor, and at least one non-transitory memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform: estimate a change in a propagation delay at two time instants, measure a time period of the two time instants using a local clock of a network node, wherein the two time instants correspond to a known timing of a received signal, subtract the change of the propagation delay from the measured time period, calculate a difference between the subtracted time period and a known timing of the received signal; and convert the difference to a frequency offset value to synchronize downlink transmission frequency between the network node and a parent node.