DSP Back-Channel Node Synchronization for Nanosecond Timing
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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 interstitial delays in hardware and firmware, 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 deterministic latency management, incorporating a TOD counter within the DSP, and employing timestamped messaging to synchronize network nodes, thereby reducing the impact of non-deterministic delays and jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing synchronization protocols are used in coherent optical networks, then network nodes can be synchronized, but non-deterministic latencies and interstitial delays from hardware and firmware reduce synchronization accuracy
Solution Approach 1:
The patent introduces a DSP back-channel as an intermediary communication path between master and slave nodes. This separate channel carries timing information independently from the main data plane, allowing synchronization messages to bypass hardware and firmware processing delays that affect the primary communication path. The back-channel acts as a mediator that delivers timing references with deterministic characteristics, resolving the contradiction between synchronization accuracy and reliability by providing a dedicated path immune to general network variability.
Solution Approach 2:
The patent segments the synchronization function from the data transmission function by implementing a separate DSP back-channel specifically for timing information. This segmentation isolates the critical synchronization path from the variable data plane, allowing independent optimization of each channel. The timing-critical messages travel through the dedicated back-channel while data traffic uses the main channel, preventing data plane latency variations from degrading synchronization accuracy.
2Measurement precision
If TOD timestamp is localized closer to the network line, then transmission noise is reduced and synchronization accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges the TOD counter function directly into the DSP module that already handles optical signal processing. By integrating the timestamping function within the existing DSP architecture rather than adding a separate external timing device, the system achieves localized timestamping close to the network line while avoiding significant complexity increases. The DSP's existing capability to process optical signals is extended to include precise time-stamping, combining multiple functions in a single component.
3Measurement precision
If nanosecond-level resolution is achieved through DSP counter synchronization, then synchronization accuracy is improved, but the system becomes more sensitive to deterministic latencies
Solution Approach 1:
The patent implements a feedback mechanism where the slave node measures the actual reception time of synchronization messages using its locally synchronized DSP counter, compares this with the transmitted timestamp, and calculates the deterministic latency. This measured latency information is fed back to the master node, which uses it to compensate for deterministic delays in subsequent synchronization updates. This closed-loop feedback approach enables nanosecond-level resolution while actively characterizing and compensating for deterministic latencies rather than being overly sensitive to them.
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.