Cellular Network Positioning Performance Improvements by Richer Device Reporting

Positioning of people and things is becoming a key component in many applications. A fundamental requirement is ubiquitous coverage of the positioning service, including conditions without a clear view of the sky as in urban and indoor areas. The main challenges and error contributions in cellular network positioning stem from multipath propagation and non line-of-sight (NLOS) radio propagation conditions. These will impact measurements related to the distance between the base stations and the user equipment (UE), and induce both variance and bias in the measurement errors. Conventionally, in the Observed Time Difference of Arrival (OTDOA) positioning method, the UE makes a hard decision about what is a reliable first path of the received signal and use that as the time of arrival (TOA) estimate. In this paper we present an alternative approach, which allows the UE to report multiple possible paths per cell to the location server. Thereby, more accurate information about the TOA distribution is transferred from the UE side to the network side, which improves the positioning accuracy. The different reporting configurations are compared, and using reporting of multiple paths per cell compared to only one path results in a 50% positioning accuracy improvement. The approach has been already standardized in Long Term Evolution (LTE) 3GPP Release 14, and this paper tries to shed some light on the technical details and resulting performance improvements of the concept.