Wireless Clock Synchronization via Offset Calibration
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Solution Overview
Problem
Current wireless communication systems, particularly 5G NR, face challenges in maintaining wireline equivalent clock synchronization accuracy due to random dynamics in channel conditions and queuing delays, which hinder the effective application of conventional synchronization protocols designed for wireline systems.
Innovation Solution
The technique involves sharing frequency and phase offsets between local NR clocks and corresponding PTP clocks at wireless nodes to synchronize PTP clocks over wireless connections, using methods such as transmitting offset indications via RRC or NAS messages and calibrating clocks based on received time stamps to maintain synchronization accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional synchronization protocols designed for wireline systems are applied to wireless systems, then the system structure remains simple and familiar, but clock synchronization accuracy deteriorates due to random dynamics in channel conditions and queuing delays
Solution Approach 1:
The patent changes the synchronization approach by measuring and compensating for specific parameters (frequency offset and phase offset) between wireline and wireless domains. The gNB measures these offsets between its PTP clock and NR clock, then communicates them to the UE for calibration, enabling accurate synchronization despite wireless channel dynamics
Solution Approach 2:
The patent introduces an intermediary mechanism where the gNB acts as a mediator that translates wireline PTP timing to wireless NR timing. By measuring offsets at the gNB and communicating calibration information to the UE, it bridges the gap between wireline synchronization protocols and wireless channel conditions
2Adaptability or versatility
If clock synchronization is implemented over wireless connections, then wireless communication flexibility is improved, but synchronization accuracy deteriorates compared to wireline connections
Solution Approach 1:
The patent implements a feedback mechanism where the gNB continuously measures frequency and phase offsets between its PTP and NR clocks, then feeds back calibration information to the UE. This closed-loop approach maintains synchronization accuracy over wireless connections by compensating for dynamic offsets in real-time
Solution Approach 2:
The patent performs preliminary offset measurement and calibration at the gNB before wireless transmission. By pre-measuring the frequency and phase offsets between PTP and NR clocks at the gNB and communicating these calibration values to the UE in advance, it prepares the synchronization parameters needed for accurate wireless timing
3Measurement precision
If frequency and phase offset calibration is performed, then clock synchronization accuracy is improved to wireline-equivalent levels, but system complexity increases due to additional measurement and communication mechanisms
Solution Approach 1:
The patent extracts the complex offset measurement and calibration functions to the gNB side, which has the computational resources and direct access to both PTP and NR clocks. The UE simply receives and applies the calibration information, reducing the complexity burden on mobile devices while achieving high synchronization accuracy
Solution Approach 2:
The patent makes the gNB a multi-functional node that simultaneously performs wireline PTP synchronization, wireless NR communication, and offset measurement/calibration. By consolidating these functions at the gNB, it avoids duplicating complex measurement mechanisms at each UE while still enabling accurate wireless synchronization
Data Source
AI summary
Techniques for clock synchronization over a wireless connection are provided. A first wireless node determines an offset between a first clock used by the first wireless node for a wired connection between the first wireless node and at least one upstream node and a second clock used by the first wireless node for a wireless connection between the first wireless node and a second wireless node on the downstream. The first wireless node transmits an indication of the determined offset to the second wireless node for use by the second wireless node to calibrate a third clock corresponding to the first clock to synchronize the third clock with the first clock, wherein the third clock is used by the second wireless node for a second wired connection with at least one downstream node.