What is "otdoa"

OTDOA (Observed Time Difference Of Arrival) is a positioning feature introduced in rel9 E-UTRA ( LTE radio). It's a multilateration method in which the User Equipment (UE) measures the time difference between some specific signals from several enodeBs and reports these time differences to a specific device in the network (the ESMLC). The ESMLC based on these time differences and knowledge of the enodeBs locations calculates the UEs' position.