PTP Synchronization Accuracy in Asymmetric Small Cell Networks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In asymmetric networks without on-path support, small cell sites in LTE networks face challenges in achieving precise frequency and phase synchronization due to varying bidirectional delays and lack of clocking support, making it costly and impractical to deploy GPS receivers for synchronization, especially in congested areas where small cells are deployed to enhance coverage.
Innovation Solution
The method involves continuously measuring one-way delays and offsets between a host site and anchored site, calculating a dynamic corrective offset for each unanchored small cell site, and applying this offset to PTP messages to synchronize clocks accurately, even without external clock support, using a ratio-based approach to adjust timestamps and delay offsets for precise synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS receivers are deployed at each small cell site for synchronization, then frequency and phase synchronization accuracy is improved, but deployment cost and device complexity increase significantly
Solution Approach 1:
An anchored small cell site acts as an intermediary between the master small cell site and other unanchored small cell sites. The anchored site receives synchronization signals from the master site and relays timing information to unanchored sites, eliminating the need for GPS receivers at each location while maintaining synchronization accuracy through this intermediate node.
Solution Approach 2:
The synchronization function is copied from the traditional GPS-based approach to a network-based PTP approach. Instead of each site independently obtaining timing from GPS, the timing information is copied and distributed through the network infrastructure using PTP messages, achieving the same synchronization function through a different mechanism.
2Ease of operation
If traditional PTP synchronization is used in asymmetric networks, then implementation simplicity is improved, but synchronization accuracy deteriorates due to varying bidirectional delays
Solution Approach 1:
The system continuously measures one-way delays in both directions (downlink and uplink) between the master and anchored sites. This feedback information about actual network conditions is used to dynamically calculate and adjust the corrective offset, compensating for asymmetric delays and maintaining high synchronization accuracy despite varying network conditions.
Solution Approach 2:
The corrective offset is made dynamic rather than static. It is continuously updated based on real-time measurements of one-way delays in both directions. This dynamic adjustment allows the system to adapt to changing network conditions and maintain synchronization accuracy even when traffic patterns and delay characteristics vary over time.
3Measurement precision
If one-way delay measurements are continuously performed in both directions, then synchronization accuracy is improved, but measurement and calculation complexity increases
Solution Approach 1:
The same measurement infrastructure and PTP messaging mechanism is used to achieve multiple functions: synchronization timing distribution, one-way delay measurement in both directions, and dynamic corrective offset calculation. This multi-functionality reduces overall system complexity by using a single unified approach rather than separate systems for each function.
Data Source
AI summary
Systems, methods, and computer-readable media for improving accuracy for providing precision time protocol (PTP) frequency and phase synchronization to each unanchored small cell site in a cluster over non on-path supported networks are provided. In embodiments, the method includes continuously measuring one-way delay down (OWDd) and delay offset down from a host site to an anchored site and one-way delay up (OWDu) and delay offset up from the anchored site to the host site. Round trip (RT) delay from the host site to each unanchored site is continuously measured. A one-way delay down prime (OWDd′) is determined for each unanchored site by applying the ratio of OWDu/OWDd to the corresponding RT delay for each unanchored small cell site. An adjusted dynamic corrective offset (DCO) is determined for each unanchored site by adding the respective OWDd′ to the respective time stamp and the delay offset down.