Enhanced mobile station localization using a hybrid TOA/AOA map-matching algorithm

The time of arrival (TOA) and angle of arrival (AOA) measurements from base stations (BS) can be used to obtain the location of the mobile station (MS). For TOA Location estimation, Line of Position (LOP) and Least Square (LS) Algorithms are usually used. To reduce the Non- line-of-sight (NLOS) errors maximum likelihood estimation (MLE) is performed in the constrained region. In this paper we propose few modifications in the NLOS LS method so as to improve the location estimation accuracy. In case of low NLOS noise environment, we observe that the Virtual Base Station (VBS) approach with modified NLOS LS method gives very high location estimation accuracy. In this paper the AOA method using residual test has also been proposed to obtain the height of Mobile Station above the ground. The AOA method also helps to obtain the location estimate when there are only two hearable BS. Using the location estimates thus obtained, we propose a hybrid TOA/AOA map-matching algorithm to obtain highly accurate location of the Mobile Station.