A closed-loop STTD scheme using limited feedback unitary precoding for MIMO-OFDM-OSTBC system

The performance of mobile location systems is often limited by large errors primarily caused by non-line-of-sight (NLOS) propagation conditions. Nonparametric kernel-based estimators for location of mobile terminals using measurements of propagation delays have been proposed to mitigate the NLOS error. This paper proposes a novel estimation algorithm based on non-parametric density approximation of the measurements using a survey of time difference measurements. This method estimates the joint density function based on the Least Square Support Vector Machine (LS-SVM) solving linear operator equations. Utilizing kriging we interpolate the measurements to specific points that we are interested in to get more survey data. Simulation results indicate that the proposed algorithm provides better location accuracy even in severe NLOS conditions.