Time-Synchronized Radio Bearer for Deterministic PTP Timing
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Solution Overview
Problem
Current mobile cellular networks lack the capability to support highly time-sensitive and synchronized end-to-end communications required for industrial automation and control systems, particularly in 5G radio access networks, due to excessive delay, delay jitter, and asymmetry, which compromise precision timing synchronization across distributed devices.
Innovation Solution
The introduction of a Time-Synchronized Radio Bearer (TS-RB) that provides low latency jitter and symmetric uplink/downlink latency, enabling PDCP-level time synchronization through a master PDCP synchronization source, configured and controlled by the serving network to ensure deterministic and symmetric communication links for IEEE 802.1 TSN applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional radio bearers are used in mobile cellular networks, then general communication requirements are met, but delay asymmetry and delay jitter occur which prevent precision timing synchronization
Solution Approach 1:
The radio bearer is segmented into separate uplink and downlink paths with independent timing management. Each direction is configured with separate timing advance values and scheduling parameters, allowing independent optimization to achieve symmetric and deterministic packet delay in both directions, which is essential for PTP-based TSN applications
Solution Approach 2:
Timing parameters such as timing advance, scheduling offset, and packet delay budget are dynamically adjusted and optimized for the time-synchronized radio bearer. The network configures specific parameter sets that compensate for radio propagation delays and ensure deterministic timing behavior, transforming the conventional asymmetric bearer into a symmetric synchronization-capable bearer
2Measurement precision
If time-synchronized radio bearer with PDCP-level synchronization is implemented, then precision timing synchronization is achieved, but network complexity increases due to additional configuration and management requirements
Solution Approach 1:
The PDCP layer is enhanced with multi-functionality to serve both conventional data transmission and precision timing synchronization roles. The same PDCP entity manages both user data and timing-critical data, using unified synchronization mechanisms that work across different bearer types, thereby reducing the need for separate specialized processing paths
Solution Approach 2:
The network introduces a synchronization intermediary function that mediates between the PTP protocol requirements and the radio bearer characteristics. This intermediary manages the synchronization configuration, coordinates timing between uplink and downlink, and handles the complexity of PDCP-level synchronization transparently, shielding application layers from implementation details
3Productivity
If conventional radio access is used, then network coverage and connectivity are provided, but excessive delay and delay jitter prevent support for time-sensitive industrial automation applications
Solution Approach 1:
The network performs preliminary timing alignment and synchronization configuration before time-sensitive data transmission begins. Timing advance values are pre-calculated and configured, synchronization parameters are established in advance, and radio resources are pre-allocated with deterministic timing characteristics, eliminating the need for reactive timing adjustments during critical data exchange
Solution Approach 2:
The time-synchronized radio bearer implements continuous timing synchronization and deterministic packet scheduling without interruption. The uplink and downlink transmissions maintain continuous symmetric timing relationships, ensuring uninterrupted precision timing for industrial automation applications, unlike conventional systems that experience timing variations between transmissions
Data Source
AI summary
Systems, methods, apparatuses, and computer program products for supporting precision timing protocol (PTP) based time sensitive network (TSN) applications are provided. One method includes configuring, by a network node, a user equipment connection and user contexts for an industrial automation and control (IAC) system or configuring at least one time synchronized radio bearer for a user equipment. The method may also include determining synchronization configuration on the at least one time synchronized radio bearer for the industrial automation and control (IAC) system, and distributing the synchronization configuration periodically or on a need basis to one or more serving network nodes for the industrial automation and control (IAC) system.