Clock Timing Synchronization via Dual-Link Transmission
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Solution Overview
Problem
Existing technologies face challenges in synchronizing the playback of audio content among multiple playback devices in a group, especially in environments with network congestion, latency, and other impairments.
Innovation Solution
The proposed solution involves transmitting clock timing to playback devices via two or more communications links, using a combination of primary and secondary communication protocols or links, such as wireless local area networks (WLANs) and optical or radio frequency links, to facilitate clock synchronization and synchronous playback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If clock timing is transmitted via a single network communication link, then the system complexity is low, but the synchronization reliability deteriorates under network congestion and latency
Solution Approach 1:
The communication path for clock timing transmission is segmented into multiple independent links. The system divides the single communication channel into separate WLAN and wireline (Ethernet) paths, allowing clock timing data to be transmitted through different physical mediums simultaneously, thereby improving reliability against network congestion and latency on any single link.
Solution Approach 2:
A dedicated clock timing communication mechanism is introduced as an intermediary between the audio source and playback devices. This intermediary layer provides specialized timing signal transmission that operates independently from the main audio data stream, ensuring that synchronization signals maintain high reliability even when general network conditions are poor.
2Measurement precision
If multiple communication links are used for clock timing transmission, then the synchronization accuracy is improved, but the device complexity increases
Solution Approach 1:
The system dynamically selects and switches between different communication links based on real-time network conditions. The clock timing transmission adapts its path by choosing between WLAN and wireline connections depending on which provides better performance at any given moment, thereby maintaining high synchronization accuracy without requiring complex permanent multi-link infrastructure.
Solution Approach 2:
The system implements clock timing transmission with more redundancy than strictly necessary for basic functionality. By sending timing signals through multiple links simultaneously or having backup paths ready, the system ensures that synchronization accuracy is maintained even when some links fail or degrade, accepting the additional complexity as a trade-off for robust performance.
Data Source
AI summary
Disclosed embodiments include facilitating clock synchronization and/or synchronous playback among multiple playback devices in a group. An individual playback device estimates and/or calculates a clock time at a clock time source (or a time offset/error between the playback device and the clock time source) based on (i) first clock timing received from the clock time source via a primary timing link and (i) second clock timing received from the clock time source via a secondary timing link. In some embodiments, estimating and/or calculating a clock time and/or clock time offset/error comprises estimating and/or calculating the clock time and/or clock time offset/error with a state estimator, such as a Kalman filter, an extended Kalman filter, or other state estimator configured to estimate a clock time and/or clock time error based on clock timing received via two or more communications links.