Network Node Synchronization via DSP Back-Channel Timestamps
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Solution Overview
Problem
Modern telecommunications systems face challenges in achieving accurate network synchronization due to non-deterministic latencies and jitter in DSP-based optical modules, which are exacerbated by hardware and firmware delays, making existing protocols like PTP and gPTP unsuitable for precise time synchronization.
Innovation Solution
Implementing a synchronization protocol that utilizes a DSP back-channel for timestamped messaging to synchronize network nodes, incorporating a TOD counter within the DSP and using deterministic latency correction fields to account for fiber and hardware delays, thereby improving synchronization accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing synchronization protocols (PTP, gPTP) are used, then network synchronization is achieved, but synchronization accuracy deteriorates due to non-deterministic latencies and jitter in DSP-based optical modules
Solution Approach 1:
The patent segments the synchronization measurement into two separate channels: a forward channel for data transmission and a back-channel for timestamped synchronization messages. This segmentation allows the back-channel to be optimized for deterministic latency measurement while the forward channel handles data traffic, resolving the contradiction between achieving high synchronization accuracy and maintaining reliability in the presence of non-deterministic DSP processing variations.
Solution Approach 2:
The patent introduces an intermediary timestamp mechanism that operates independently of the main data processing path. Timestamps are inserted at known points in the signal path and transmitted through the back-channel, serving as intermediaries that carry precise timing information without being affected by the non-deterministic processing delays in the main DSP pipeline.
2Adaptability or versatility
If DSP-based optical modules are used, then signal processing capability is improved, but synchronization stability deteriorates due to hardware and firmware delays
Solution Approach 1:
The patent extracts the timing measurement function from the main DSP processing path and places it in a separate back-channel subsystem. By taking out the critical timing measurements from the complex, variable DSP processing pipeline, the system maintains the adaptability and signal processing capability of the DSP while achieving stability in synchronization measurements through the dedicated back-channel path.
Solution Approach 2:
The patent implements preliminary timestamp insertion at fixed, known points in the signal path before the variable DSP processing occurs. These preliminary timestamps serve as reference markers that allow later calculation of actual processing delays, enabling the system to maintain both high signal processing capability and synchronization stability by compensating for DSP-induced variations.
3Measurement precision
If timestamped messaging via back-channel is implemented, then synchronization accuracy is improved to +/−1 nanosecond, but system complexity increases
Solution Approach 1:
The patent merges the synchronization function with the existing optical communication infrastructure by utilizing the back-channel that is already present in coherent optical modules. Rather than adding a completely separate synchronization system, the timestamped messaging is combined with the existing communication path, achieving +/−1 nanosecond accuracy while minimizing the increase in system complexity through resource sharing and integration.
Data Source
AI summary
In one embodiment, the disclosure includes a network node synchronization system. The system may include a first node. The first node may include a first host card comprising a first (TOD) time of day counter, a first digital signal processor (DSP) comprising a first DSP counter, and a first optical communication device comprising a first DSP communication channel, wherein the first DSP communication channel transports DSP frames. In various embodiments, the DSP is a coherent DSP.