An analytic solution for computing RSTD uncertainty in generating assistance data for OTDOA positioning

OTDOA (Observed Time Difference of Arrival) is a positioning method available in LTE. User Equipment (UE) that supports OTDOA requires assistance data from a location server. The quality of the assistance data directly impacts the UE measurement accuracy. The assistance data are specifications of a reference and neighbor cells for UE to measure. Expected RSTD (Reference Signal Time Difference) is included with the neighbor cell information. An analytic solution for computing the Expected RSTD and Expected RSTD uncertainty is proposed. The analytic solution is applied during generation of assistance to avoid possible PCI (Physical Cell Identity) ambiguity in OTDOA positioning. The overall goal with this analytic solution is to increase the final OTDOA positioning accuracy.