UPF Multiport Time Synchronization Using GPIO PPS Offset Correction
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Solution Overview
Problem
Existing methods for high-precision time synchronization in 5G networks, particularly in the User Plane Function (UPF), face challenges in accurately synchronizing the Network-Side Time-Sensitive Networking (TSN) Translator (NW-TT) module with the Grandmaster (GM) due to different hardware clock sources across N3 and N6 interfaces, leading to incorrect residence time calculations and synchronization issues.
Innovation Solution
A hardware-software co-design architecture using General-Purpose Input/Output (GPIO)-based Pulse Per Second (PPS) signal triggering and state machine control to calculate time offsets between N3 and NW-TT interfaces, employing a Data Plane Clock Servo module for precise synchronization, including a protocol module, pulse handler, and synchronization adjuster to adjust time and frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If software-based time synchronization methods are used in UPF, then implementation complexity is reduced, but synchronization precision deteriorates due to hardware access latency and environmental interference
Solution Approach 1:
The synchronization system is segmented into independent hardware modules (PPS generation unit, pulse transmission unit, pulse reception unit, offset calculation unit) that operate autonomously. Each module handles specific functions without software intervention, eliminating software-based latency while maintaining modular implementation.
Solution Approach 2:
The patent replaces software-based time synchronization mechanisms with a hardware-based electrical pulse system. GPIO pins generate and detect PPS signals directly at the hardware level, substituting the mechanical/software time measurement process with an electrical signal-based approach that eliminates hardware access latency.
2Adaptability or versatility
If different hardware clock sources are used for N3 and N6 interfaces, then system flexibility is improved, but time synchronization accuracy deteriorates due to offset errors
Solution Approach 1:
The system continuously measures the time offset between N3 and N6 clock sources using PPS pulse detection, calculates the offset value, and feeds this information back to adjust the clock synchronization. This closed-loop feedback mechanism maintains accuracy despite using different hardware clock sources.
Solution Approach 2:
The patent dynamically adjusts the time offset parameter based on real-time measurements from PPS pulse detection. By changing the offset value according to actual hardware conditions, the system compensates for differences between N3 and N6 clock sources while maintaining synchronization accuracy.
3Measurement precision
If hardware-based PPS signal triggering is implemented, then synchronization precision is improved to sub-100 ns, but device complexity increases due to additional hardware components
Solution Approach 1:
The GPIO pins are configured to serve multiple functions: generating PPS signals for N3 interface synchronization, detecting PPS signals for N6 interface synchronization, and providing offset measurement capabilities. This multi-functionality reduces the need for separate dedicated hardware components.
Solution Approach 2:
The hardware system performs self-synchronization by automatically detecting PPS pulses, calculating offsets, and adjusting timing without external intervention. The offset calculation unit autonomously measures and compensates for hardware differences, eliminating the need for complex external synchronization equipment.
4Reliability
If state machine control is used for pulse handling, then synchronization reliability is improved, but processing time increases
Solution Approach 1:
The state machine is pre-configured with predetermined transition paths for pulse detection and offset calculation. By preparing the control logic in advance with known state transitions, the system eliminates runtime decision-making delays while maintaining reliable synchronization through structured state management.
Data Source
AI summary
Described is a method of synchronizing a Network-Side Time-Sensitive Networking (TSN) Translator (NW-TT) module inside a User Plane Function (UPF) of a communication network with a Grandmaster (GM) in a 5G Time Domain of the communication network. The method includes adjusting a clock frequency of the N3 interface to synchronize the time between the N3 interface and the GM. The method includes generating one or more pulses at a pin of the N3 interface. The method includes detecting the one or more pulses at a pin of the NW-TT module. The method includes determining a time offset value (OffsetNW-TT) between the N3 interface and the NW-TT module. The method includes adjusting a time or a clock frequency of the NW-TT module using the determined time offset value (OffsetNW-TT) to synchronize the time between the NW-TT module and the GM.