BTS Holdover Timing via Neighbor Preamble Phase Locking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Wireless communication networks face disruptions and shutdowns due to loss of synchronization among base transceiver stations (BTSs), as existing solutions rely on secondary external reference clocks or internal oscillator stability, which can lead to interference and premature shutdowns when primary synchronization fails.
Innovation Solution
Deriving a reference timing signal from a physical layer training signal received from a neighbor network node to synchronize downlink transmissions, allowing BTSs to continue operation indefinitely by periodically measuring and phase-locking to neighbor BTS preambles, thereby avoiding shutdowns and maintaining network coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a BTS operates in holdover mode using its internal oscillator after losing external synchronization, then the BTS can continue downlink transmissions for a limited time, but the internal oscillator will drift over time and eventually require shutdown
Solution Approach 1:
The patent introduces a neighbor BTS as an intermediary synchronization source. When the primary external reference is lost, the BTS derives timing from physical layer training signals (preambles) of neighboring BTSs, which act as mediators to maintain synchronization without requiring shutdown. This resolves the contradiction by providing an alternative timing source that extends holdover duration while maintaining reliability through periodic re-synchronization to the network.
2Object-affected harmful factors
If a BTS shuts down downlink transmissions when synchronization is lost, then interference to other BTSs is avoided, but network coverage and availability are reduced
Solution Approach 1:
The patent implements feedback by continuously monitoring the timing of received neighbor BTS preambles and adjusting the local oscillator accordingly. This closed-loop synchronization allows the BTS to maintain accurate timing and avoid interference to other cells while remaining operational, thus preserving network availability without causing harmful interference through uncontrolled drift.
3Measurement precision
If secondary external reference clocks are used for synchronization, then synchronization accuracy can be maintained, but device complexity and cost increase
Solution Approach 1:
The patent uses a copying approach by deriving timing information from copies of neighbor BTS transmission signals (physical layer training signals). Instead of requiring additional external reference clock hardware, the system extracts and copies timing characteristics from existing neighbor cell transmissions, maintaining synchronization accuracy while avoiding the complexity and cost of secondary external reference clock systems.
Data Source
AI summary
A host base transceiver station BTS derives a reference timing signal from a physical layer training signal (such as a preamble) received from a neighbor network node/BTS. Downlink transmissions are then synchronized to the derived reference timing signal. This may be used as a holdover timing mode, such as when the host BTS determines that synchronization from a primary source is no longer reliable. In an embodiment, a reference oscillator of the host BTS is phase locked to the derived reference timing signal. Variations include one or multiple such training signals from one or multiple neighbor BTSs, selecting one BTS when the primary synchronization mechanism fails for several BTSs in the same area, and how to phase lock the oscillator without dithering about the target frequency. Apparatus and computer programs are also detailed.