A New Position Quality Metric for NR RAT Dependent OTDOA Positioning Methods

Release 9 specification of the Third Generation Partnership Project (3GPP) provided support to Observed Time Difference of Arrival (OTDOA) based positioning method for UE-Assisted mode using Long Term Evolution (LTE) Radio Access Technology (RAT). Evolving to release 16 specification it has been agreed by 3GPP consortium also to support UE-Based New Radio (NR), popularly known as 5G RAT dependent positioning method. UE-Based positioning methods will enable the device to calculate its location by using the Assistance Data (AD) that are transmitted by the Network. The AD may need to be broadcast and since the broadcast resource is constraint in terms of resources and physical size limit of broadcast channel, the AD should be selected carefully. The selection of data in the AD delivery would play a crucial role for the UE to calculate the location with high accuracy. In order to obtain high precision accuracy, the geometry in terms of UE location and the selection of beams would play an important role in NR. Further NR is expected to operate in high bandwidth spectrum where beam based transmission would be more common. Several beams may have to be used to get a focused coverage and it should be directed in various angles. Network should carefully select which beams to be used for the Position Reference Signal (PRS) transmission in order to mitigate interference and optimize the resources. The traditional Geometric Dilution of Precision (GDOP) metric which is based upon geometry between UE and the Transmission Points (TRPs) may not be sufficient as the beams may have different tilt/orientation. In this paper, we discuss the architecture and signaling of UE-Based DL RAT dependent OTDOA Positioning method. We exploit the NR Beam based angular information in selecting the cell sector or beams to be used for location calculation. We propose a new metric for the beam selection for the PRS transmission.