Model for 5G UDN Positioning System Topology Search Using Dilution of Precision Criterion

Positioning of User Equipment (UE) in 5G Ultra-Dense Networks (UDN) promises significant improvement in location accuracy estimation due to densification of Access Points (AP) infrastructure. For range and bearing primary measurements network geometry plays a significant role in the resultant positioning accuracy, regardless of time (TOA) and angle (AOA) of arrival secondary processing technique. Existing approaches for positioning system topology search in terrestrial cellular networks utilize geometric dilution of precision (GDOP) minimization under certain conditions, satisfying application requirements. Drawback of existing approaches, yielding tractable analytical results, is that they predominantly have assumption of 2-dimensional (2D) AP distribution according to regular hexagonal grid, square lattice or Poisson point process (PPP). If for previous 2G-4G cellular networks it is justified, for 5G UDN these assumptions do not retain. According to latest 3GPP specifications, enhanced positioning service area should provide sub-meter 3D UE location estimation in horizontal and vertical planes. The contribution of current research is a simulation model for 5G UDN positioning system topology search using well known in Global Navigation Satellite Systems (GNSS) horizontal (HDOP), vertical (VDOP) and position (PDOP) dilution of precision (DOP) criterion. Simulation results reveal, that fixed AP number topology, achieving DOP criterion in horizontal plane, does not provide satisfying DOP in vertical one.