Communication Device Delay Time Correction for Unsynchronized Clocks
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Solution Overview
Problem
Existing communication devices face challenges in accurately measuring delay time between unsynchronized clocks, leading to discrepancies between estimated and actual one-way delay times, particularly in real-time communication systems like voice communication and IoT.
Innovation Solution
A communication device with a first clock and a communication unit that receives and transmits packets, includes a delay time acquiring unit to measure delay times using both clocks, and a correction unit to calculate and apply a correction value based on minimum delay times to correct the delay time, ensuring accurate synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If Ping method is used to measure delay time without clock synchronization, then measurement can be performed without complex synchronization, but the measured value includes processing time and differs from actual one-way delay time
Solution Approach 1:
The patent segments the round-trip delay measurement into two separate one-way delay measurements by utilizing timestamps from both clocks. Instead of measuring the entire round trip as one value and dividing by two, the system separately measures the forward delay (from first clock to second clock) and backward delay (from second clock to first clock), then averages these segmented measurements to eliminate processing time bias.
Solution Approach 2:
The patent introduces timestamp markers as intermediary elements that carry time information between the two clocks. These timestamps act as mediators that allow each clock to record the exact time packets are sent and received, enabling precise calculation of one-way delays without requiring the clocks to be synchronized to a common reference.
2Measurement precision
If clock synchronization is implemented to obtain accurate delay time, then measurement accuracy improves, but system complexity and synchronization requirements increase
Solution Approach 1:
Instead of synchronizing the clocks to a common reference (the conventional approach), the patent inverts the problem by allowing each clock to operate independently and use its own timestamps to measure delays. The system calculates delay by comparing the difference between transmission and reception timestamps from each respective clock, rather than trying to make the clocks agree on a universal time.
3Measurement precision
If minimum delay time is used for correction calculation, then correction accuracy improves, but more measurement data and time are required
Solution Approach 1:
The patent performs preliminary correction by calculating the clock time difference using minimum delay times from previous measurements, then applies this correction to subsequent delay measurements. This preliminary correction establishes a baseline offset that can be used immediately, reducing the need to wait for extensive data collection before achieving accurate measurements.
Data Source
AI summary
A communication device includes a first clock, a communication unit, a delay time acquiring unit, a selection unit, and a correction unit. The communication unit is configured to receive first packets from an outside communication device including a second clock and transmit second packets to the outside communication device. The delay time acquiring unit is configured to a first delay time and a second delay time. The selection unit is configured to select one of the first packet and the second packet as a target packet. The correction unit is configured to calculate a correction value based on a first minimum delay time or a second minimum delay time, and correct the delay time of the target packet using the correction value.