Enhanced LTE TOA/OTDOA estimation with first arriving path detection

With increasing importance of location based services, requirements for TOA (time of arrival) and TDOA (time difference of arrival) measurements have been specified in 3GPP LTE Rel. 9 to ensure accurate TIE (user equipment) positioning. In order to meet these requirements, it is vital to accurately estimate the first signal arriving path. This is, however, not trivial, especially in multipath environments. In this work, we describe methods for LTE TOA and TDOA measurements with enhanced first arriving path detection. The conventional maximum likelihood based correlation profile is used as detection metric. After grossly determining the signal region by a moving window, three methods, namely peak detection, SNR based threshold and adaptive threshold based on noise floor and metric peak value are employed to estimate the first arriving path. Simulations results show that the proposed adaptive threshold based method is robust against channel variations and can meet all 3GPP requirements under various multipath channels.