Prior NLOS Ratio Estimate and Measurements Rating in Wireless Cellular Networks

The main drawback to improve the precision in cellular location systems based on time delays is the presence of non-line-of-sight (NLOS) propagation, introducing significant and hardly predictable errors in the measurements used in location. In this paper we propose a technique to previously detect and estimate the NLOS ratio present in the measurements. A comprehensive research on the Time of Arrival (TOA) dependence on the NLOS ratio existing in the measurements leads to estimate that ratio from the deviation calculated directly from the available measurements. NLOS detection and ratio estimate is very useful to classify and weight the measurements available in order to perform the following location estimate with the most accurate ones. Several simulations have been conducted to show the precision of ratio estimate and the measurements rating based on it.