5G/NR  -  Positioning  




DL Positioning Reference Signal

The 5G Positioning Reference Signal (PRS) is a feature introduced in 5G networks to support positioning services. Unlike previous generations, 5G networks aim to provide high-accuracy location information, which is critical for various applications, including vehicle navigation, drone control, and the management of robots in factories.

Why PRS ? How to Deploy ?

Purpose: PRS is designed to improve the accuracy of positioning information. It is used by devices to measure the time of arrival (ToA) and angle of arrival (AoA), which are crucial for determining the device's location.

Deployment: PRS can be deployed across multiple frequency layers and can be beamformed to increase signal strength and accuracy of positioning. With capabilities for multi-layer deployment and beamforming, PRS boosts signal strength and positioning precision.

Usage: The signal is used by UE to perform measurements for positioning. These measurements are then reported back to the network, which calculates the UE's position using trilateration or triangulation methods. Devices utilize PRS for location measurements, crucial for network-based position computation through methods like trilateration.

Integration: 5G PRS is integrated with other technologies such as GNSS (Global Navigation Satellite System) to provide a comprehensive positioning solution that works both indoors and outdoors.

Physical Resources for PRS ?

Following illustration shows how PRS signal is generated and allocated to 5G/NR physical resource grid.  It describes on the initialization sequence c_init using the PRS scrambling identity, the slot number, and other parameters.

  •   The sequence r(m) represents the resource elements for PRS.
  •   Time domain and frequency domain locations for these elements are defined by specific indices and parameters, such as lPRSstart and KPRScomb
  •   The table (38.211-Table provides symbol number mapping within the downlink resource grid. In short, it gives k' value based on KPRScomb and (l - lPRSstart)
  •   The formula k = m * KPRScomb + ((kPRSoffset + k') mod KPRScomb indicates the frequency domain location of PRS.

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