Distributed Radio Transparent Clock for Wireless Synchronization
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Solution Overview
Problem
Current synchronization techniques, such as IEEE 1588v2, face challenges in achieving precise phase synchronization across wireless links due to packet delay variation and asymmetry, which are inherent properties of microwave radio interfaces, leading to complex and restricted implementations.
Innovation Solution
A method and system for calculating phase and frequency synchronization across wireless links by determining offsets between transceivers and intermediate nodes using timestamped airframes, allowing independent calculation of phase offsets on both sides of the link, independent of master-slave configuration, and utilizing airframe-level timestamping to minimize bandwidth impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If IEEE 1588v2 phase synchronization is used across wireless links, then frequency synchronization can be achieved, but packet delay variation and asymmetry cause scattering and deviation errors that reduce synchronization precision
Solution Approach 1:
The patent segments the synchronization function by introducing intermediate nodes that independently calculate and compensate for offset values on each wireless link segment. Instead of end-to-end synchronization that accumulates errors, each node processes timing packets locally, determining offset values between adjacent nodes and applying corrections incrementally along the path, thereby preventing error propagation and improving overall synchronization precision
Solution Approach 2:
The patent replaces the mechanical packet-level synchronization approach of IEEE 1588v2 with a radio-level timestamping mechanism. By capturing timestamps at the radio interface before packet processing, the system substitutes the packet transmission mechanism with a direct radio timing measurement, eliminating the scattering errors introduced by packet fragmentation and processing variations
2Measurement precision
If packet-level phase synchronization is implemented, then time synchronization can be achieved, but the process imposes complexities and restrictions that reduce ease of operation
Solution Approach 1:
The patent implements self-service by enabling each intermediate node to autonomously calculate offset values using timing packets it receives. Each node independently performs timestamping, offset determination, and correction without requiring centralized control or complex coordination with other nodes. This distributed self-service approach eliminates the operational complexities of centralized packet-level synchronization while maintaining high precision
Solution Approach 2:
The patent applies preliminary action by having intermediate nodes pre-calculate and store offset values between adjacent nodes before actual synchronization operations. These offset values are determined in advance through timestamping exchanges and are readily available when timing packets need correction, eliminating the need for complex real-time calculations and reducing operational restrictions
3Measurement precision
If airframe-level timestamping is used instead of packet-level timestamping, then synchronization accuracy improves, but bandwidth consumption increases
Solution Approach 1:
The patent merges the timestamping function with the existing airframe structure by embedding timestamp information directly into the airframe headers. Instead of creating separate timestamp messages or using additional packet overhead, the timing data is combined with the radio frame structure, achieving high-precision timestamping without increasing overall bandwidth consumption. This merging approach efficiently utilizes the existing communication infrastructure
Data Source
AI summary
An example method comprises receiving, by a first PHY of a first transceiver, a timing packet, timestamping, by the first transceiver, the timing packet and providing the timing packet to a first intermediate node, determining a first offset between the first intermediate node and the first transceiver, updating a first field within the timing packet with the first offset between the first intermediate node and the first transceiver, the offset being in the direction of the second transceiver, receiving the timing packet by a second transceiver, the timing packet including the first field, information within the first field being at least based on the first offset, determining a second offset between the second transceiver and an intermediate node that provided the timing packet to the second transceiver and correcting a time of the second transceiver based on the information within the first field and the second offset.