Patent ID: 7873368

Claim:
A system for locating within an area a mobile unit arranged for a wireless radio communications with fixed devices, wherein location is determined by comparing radio signal characteristics between the mobile unit and the fixed devices to a database relating the radio signal characteristics to location within the area, wherein at least one portion of the area includes a barrier, comprising; means for assigning the at least one portion including the barrier with a probability of zero; means for taking sequential samples of the radio signal characteristics; for each sample of the radio signal characteristics, means for determining two or more possible initial locations for the mobile unit and assigning a location probability that the mobile unit is at each of the possible locations, each location probability modified to account for the barrier; for each possible location determined using a sample after an initial sample, means for determining a movement probability that the mobile unit has moved from each possible location for one or more prior samples to the possible location, the movement probability being derived from proximity of the possible location for the one or more prior samples and the possible locations for the current sample, wherein the movement probability is modified by factors including at least the probability of zero for the at least one portion including the barrier of the mobile unit between the possible location for the one or more prior samples and the possible location for a current sample; and means for selecting a location for the mobile unit as the most probable location for the current sample based on a combination of the location and movement probabilities.