Synchronization precision specifies the allowable deviation between a base station’s clock and the reference synchronization source to ensure accurate operation. Per 3GPP standards:
- Time synchronization: Base stations must maintain synchronization with a precision of ±1.5 microseconds (µs) relative to the reference time.
- Frequency synchronization: Base stations must achieve a frequency synchronization precision of ±0.05 parts per million (ppm), ensuring accurate frequency alignment critical for seamless network operations and minimized interference.
Frequency synchronization has lower precision requirements compared to time synchronization, with tolerances measured at the millisecond level. In scenarios where the reference clock becomes abnormal, base stations enter holdover mode, relying on their internal clocks to maintain synchronization.
In this mode, base stations can operate effectively for up to 90 days under frequency synchronization. However, in the case of time synchronization, the holdover capability is more limited, allowing proper functionality for a maximum of 24 hours. This distinction underscores the critical precision demands of time synchronization for uninterrupted network performance.
The synchronization precision requirements for basic services in NR (New Radio) are similar to those in LTE. However, advanced coordination technologies like multi-antenna MIMO, CoMP, and CA are more prevalent in NR, necessitating stricter synchronization.
To ensure effective coordination, the time difference between signals from different nodes must be less than the cyclic prefix (CP) duration, requiring time deviations of less than 100 ns. Additionally, NR introduces services such as high-precision positioning, high-speed mobility, and industrial applications, demanding even greater synchronization accuracy for optimal performance.
Prerequisites for this article are: