Method for tracking location of a mobile unit
Location of a mobile unit is determined by a combined probability, derived from a first probability for possible locations based on a current sample of radio signal characteristics and a second probability that a unit has moved from a prior location or probable location to each possible location.
1. A method 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 said mobile unit and said fixed devices to a database relating said radio signal characteristics to location within said area, wherein at least one portion of said area includes a barrier, comprising;
assigning the at least one portion including the barrier with a probability of zero;
taking sequential samples of said radio signal characteristics;
for each sample of said radio signal characteristics determining two or more possible initial locations for said mobile unit and assigning a location probability that said mobile unit is at each of said possible locations, each location probability modified to account for the barrier;
for each possible location determined using a sample after an initial sample, determining a movement probability that a mobile unit has moved from each possible location for one or more prior samples to said possible location, said movement probability being derived from proximity of said possible location for said one or more prior samples and said possible locations for said current sample, wherein said 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 said possible location for said one or more prior samples and said possible location for a current sample; and
selecting a location for said mobile unit as the most probable location for said current sample based on a combination of said location and movement probabilities.
2. The method as specified in claim 1 wherein said location probability is assigned according to a comparison of said sampled radio signal to radio signal characteristics for said location in said database.
3. The method as specified in claim 1 wherein said database includes data characterizing quality of radio signal characteristics for locations within said area and wherein said location probability is assigned according to said quality characterizing data.
4. The method as specified in claim 1 wherein said movement probability is determined by comparing distance between said locations to expected distance for movement of said mobile unit in a time period between said samples.
5. A method 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 said mobile unit and said fixed devices to a database relating said radio signal characteristics to location within said area, wherein at least one portion said area includes a barrier, comprising;
assigning the at least one portion including the barrier with a probability of zero;
taking sequential samples of said radio signal characteristics;
for each sample of said radio signal characteristics determining two or more possible initial locations for said mobile unit and assigning a location probability that said mobile unit is at each of said possible locations, each location probability modified to account for the barrier;
for each possible location determined using a sample after an initial sample, determining a movement probability that a mobile unit has moved from a selected location determined for one or more prior samples to said possible location, said movement probability being derived from proximity of said possible location for said one or more prior samples and said possible locations for said current sample, wherein said 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 said possible location for said one or more prior samples and said possible location for a current sample; and
selecting a location for said mobile unit as the most probable location for said current sample based on a combination of said location and movement probabilities.
6. The method as specified in claim 5 wherein said location probability is assigned according to a comparison of said sampled radio signal to radio signal characteristics for said location in said database.
7. The method as specified in claim 5 wherein said database includes data characterizing quality of radio signal characteristics for locations within said area and wherein said location probability is assigned according to said quality characterizing data.
8. The method as specified in claim 5 wherein said movement probability is determined by comparing distance between said locations to expected distance for movement of said mobile unit in a time period between said samples.
9. A method, comprising:
receiving a first sample signal from a mobile unit, the first sample signal including first signal characteristics;
comparing the first signal characteristics to a database, the database including characterizing data of a plurality of locations, wherein at least one portion of the locations includes a barrier;
assigning the at least one portion including the barrier with a probability of zero;
assigning a first set of initial locations of the mobile unit and determining first location probabilities for each initial location of the first set based on the comparison of the first signal characteristics to the database, the first location probabilities being modified to account for the barrier;
receiving a further sample signal from the mobile unit, the further sample including further signal characteristics;
comparing the further signal characteristics to the database characterizing the plurality of locations;
assigning a further set of locations of the mobile unit and determining further location probabilities for each location of the further set based on the comparison of the further signal characteristics to the database, the further location probabilities modified to account for the barrier;
determining movement probabilities for each location of the first arid the further sets, the movement probabilities being based on a proximity between each of the locations within the first and further sets and the ability of the mobile unit to move between the locations, the movement probabilities being modified to account for the barrier for the mobile unit between locations; and
combining the first and further location probabilities with the movement probabilities for each of the locations and selecting a location having the highest combined location and movement probabilities as the location of the mobile unit.
10. The method as specified in claim 9 wherein the database includes data characterizing a quality of radio signal characteristics for locations and wherein the location probability is assigned according to the quality characterizing data.
11. The method as specified in claim 9 wherein the movement probability is determined by comparing a distance between the plurality of locations to an expected distance for movement of the mobile unit in a time period between the first and the further samples.