Sign in Subscribe

NR-Primary Synchronization Signal (PSS)

Last updated on 
5G & 6G Prime Membership Telecom


In 5G New Radio (NR) wireless communication, the Primary Synchronization Signal (PSS) is a fundamental component used for cell search and synchronization. The PSS is part of the synchronization signals and channels that help User Equipment (UE) synchronize with the cell and decode subsequent control information. Let's delve into the technical details of NR-Primary Synchronization Signal:

  1. Purpose:
    • The primary purpose of the PSS is to aid UEs in synchronizing with the serving cell.
    • It provides essential timing and frequency synchronization information to assist UEs in aligning their communication parameters with the base station (gNB - gNodeB) accurately.
  2. Timing and Position:
    • The PSS is transmitted periodically within a frame. In the context of NR, a frame is a time division of the radio resources, and the PSS is transmitted in the time domain.
    • The PSS is typically transmitted at specific positions within the frame, making it possible for UEs to predict when and where to look for synchronization signals.
  3. Frequency Domain Characteristics:
    • The PSS is transmitted in the frequency domain at specific subcarrier positions.
    • The frequency location of the PSS subcarriers is defined by the NR numerology, which includes parameters such as subcarrier spacing and bandwidth.
  4. Structure:
    • The PSS consists of a known sequence of symbols that are designed to be easily detectable by UEs.
    • In NR, the PSS consists of two parts: PSS-Four (PSS-F) and PSS-Three (PSS-T).
      • PSS-F provides information about the frame structure and slot configuration.
      • PSS-T provides information about the radio frame number and additional frame timing information.
  5. Sequence Generation:
    • The sequences used in PSS are predefined and known by both the gNB and the UE. They are carefully designed to have good auto-correlation and cross-correlation properties, making them easily recognizable and distinguishable.
  6. Detection and Synchronization Procedure:
    • During cell search, the UE scans the received signal for the PSS.
    • The UE correlates the received signal with the known PSS sequences to detect the presence of the synchronization signal.
    • Once the PSS is detected, the UE can obtain information about the timing and frequency offset of the cell, enabling synchronization.
  7. Multiplexing with Other Signals:
    • The PSS is designed to work in conjunction with other synchronization signals, such as the Secondary Synchronization Signal (SSS) and Cell-specific Reference Signals (CRS), to provide comprehensive synchronization information.
  8. Frame Configuration Impact:
    • The PSS configuration, including its periodicity and location within the frame, is determined during cell setup and configuration.
    • Different numerologies and frame configurations in NR may impact the timing and positioning of the PSS.
  9. Inter-Cell Interference Avoidance:
    • The design of PSS and other synchronization signals takes into consideration the need to avoid interference between neighboring cells to ensure reliable and accurate cell identification.

In summary, the NR-Primary Synchronization Signal plays a crucial role in the initial cell search and synchronization process for UEs in a 5G NR network. It provides essential timing and frequency information, enabling UEs to align their communication parameters with the serving cell accurately.