Clock Synchronization Using LF and HF Signals
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Solution Overview
Problem
Existing communication systems face challenges with synchronization and authentication due to signal degradation, timing misalignment, and power consumption issues, particularly in RF ranging applications like automotive access, where long packet preambles increase latency and power consumption.
Innovation Solution
The method involves a local device with a low-frequency (LF) transmitter and high-frequency (HF) transceiver synchronizing with a remote device having an LF receiver and HF transceiver, using LF signals for initial synchronization and HF signals for fine-tuning, with predetermined time delays to minimize power consumption and latency, and includes encryption for authentication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long packet preambles are used for synchronization and authentication, then timing alignment accuracy is improved, but latency and power consumption increase
Solution Approach 1:
The patent divides the synchronization process into two distinct phases: a coarse synchronization phase using a long preamble to achieve initial timing alignment, and a fine synchronization phase using a short packet to refine the timing. This segmentation allows the system to obtain accurate timing alignment without requiring the entire synchronization process to use the long preamble format, thereby reducing overall latency.
Solution Approach 2:
The patent performs coarse synchronization using the long preamble in advance, before the actual data transmission. This preliminary action establishes the initial timing alignment, allowing subsequent short packets to be transmitted with minimal overhead for fine-tuning the synchronization, thus reducing the latency of the overall communication process.
2Measurement precision
If long packet preambles are used for synchronization and authentication, then timing alignment accuracy is improved, but power consumption increases
Solution Approach 1:
The patent segments the synchronization process into coarse and fine phases, allowing the power-intensive long preamble to be used only once for initial alignment. Subsequent communications use short packets for fine synchronization, significantly reducing the cumulative power consumption while maintaining timing alignment accuracy.
Solution Approach 2:
The patent performs the power-consuming coarse synchronization using the long preamble as a preliminary action before actual data transmission. This one-time preliminary synchronization reduces the need for repeated long preambles, thereby lowering overall power consumption while ensuring accurate timing alignment is achieved beforehand.
3Reliability
If RF ranging is performed for authentication, then security is improved, but system latency increases
Solution Approach 1:
The patent segments the authentication process into two parts: initial authentication using the long preamble with coarse timing information, and final authentication confirmation using short packets with fine timing information. This segmentation allows security to be established through the initial phase while minimizing the time impact of RF ranging in the subsequent phases.
Solution Approach 2:
The patent performs preliminary authentication and coarse timing measurement using the long preamble before actual data transmission. This preliminary action establishes the security baseline and initial timing reference, allowing subsequent short packet exchanges to complete authentication quickly with minimal latency impact.
Data Source
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AI summary
Aspects of the present disclosure are directed to communications between devices. As consistent with one or more embodiments, a local device has a first clock, a low-frequency (LF) transmitter and a high-frequency (HF) transceiver. A remote device includes a second clock, a LF receiver and a HF transceiver. An LF signal is transmitted from the local device to the remote device and used to synchronize the second clock. The first clock is synchronized based on an HF signal transmitted to the local device using the synchronized second clock and a first predetermined time delay relative to receipt of the LF signal. The second clock is resynchronized based on a second HF signal transmitted to the remote device using the first clock and a second predetermined time delay relative to receipt of the first HF signal, while accounting for a trip time for communicating one or both of the HF signals.