Airframe Timestamping for Wireless Phase Synchronization
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Solution Overview
Problem
Current synchronization techniques, such as IEEE 1588v2, face complexities and inaccuracies when achieving phase synchronization across wireless links due to packet-level processing, which introduces additional latency and asymmetry, making it difficult to determine phase and frequency offsets accurately.
Innovation Solution
A method that calculates phase offset independently on both sides of the wireless link using four timestamps from airframes, allowing for precise phase and frequency synchronization, independent of packet fragmentation and master-slave configuration, and utilizing existing channels for timestamp transfer without affecting user data bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If packet-level phase synchronization (IEEE 1588v2) is used across wireless links, then frequency synchronization can be achieved, but phase synchronization accuracy deteriorates due to packet delay variation and link asymmetry
Solution Approach 1:
The patent replaces packet-level timestamping (mechanical/digital system) with physical layer signal processing. By using correlation-based detection of training sequences in the physical layer, the system directly measures phase offset without relying on packet timestamp exchanges, thereby eliminating packet delay variation effects and achieving accurate phase synchronization across wireless links
Solution Approach 2:
The patent introduces training sequences as an intermediary carrier for phase synchronization information. These known training sequences are embedded in the physical layer signals, allowing receivers to correlate and detect phase offsets directly from the training sequences without needing to process packet timestamps, thus simplifying the synchronization process while improving accuracy
2Measurement precision
If packet-level timestamping is used for phase synchronization, then time offset can be measured, but measurement precision deteriorates due to additional latency and asymmetry in wireless packet transmission
Solution Approach 1:
The patent performs phase offset measurement at the physical layer before packets are assembled and processed at higher layers. By detecting phase offsets from training sequences in the received physical layer signals, the system obtains time offset measurements without subjecting them to packet processing latency and asymmetry, thereby improving measurement precision while avoiding time loss
Data Source
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AI summary
An example system comprising a first transceiver configured to receive a request airframe from a second transceiver over a wireless link, the request airframe including a first timestamp indicating a first time T1 timestamp a second time indication indicating a second time T2 that the request airframe was received, generate a respond airframe and including a third time indication indicating a third time T3 that the respond airframe is transmitted to the second transceiver, transmit the respond airframe to the second transceiver, provide a timestamp information request to second transceiver, receive a timestamp information response, the timestamp information response including a fourth time indication indicating a fourth time T4, calculate a counter offset using the first time, second time, third time and fourth time as follows: counter offset = (TS1+TS4-TS3-TS2)/2 calculate a phase offset based on the counter offset, and correct a phase of the first transceiver.