Enhanced mobile location method and system
View Patent ↗A method and system is disclosed for locating a mobile radio terminal in a radio communications network. The method makes use of additional positional constraints provided as a result of unreported cells. In one form of the invention, a likely reason for a particular cell not being reported is determined and an associated probability term is determined for use in a position location model. The invention also relates to a system for implementing the method.
1. A method for locating a mobile radio terminal in a radio communications network, the method comprising:
identifying a set of cells about an approximated location of the mobile radio terminal;
identifying at least one cell in the identified set that is unreported by the mobile radio terminal, the remaining cells in the identified set being reported;
determining a maximum number of cells that can be reported by checking a network threshold;
if the reported cells in the identified set exceed the maximum number of cells, compare interference levels from the reported cells against a level of signal strength of the weakest reported cell and determine a first probability that an unreported cell is weaker than the weakest of the reported cells;
if the reported cells in the identified set do not exceed the maximum number of cells, compute a maximum interference level from the reported cells in the identified set and determine whether the maximum interference level is greater than a receiver sensitivity threshold of the mobile radio terminal;
if the maximum interference level is greater than the sensitivity threshold, compute a second probability of the unreported cell being weaker than the maximum interference level;
if the maximum interference level is not greater than the sensitivity threshold, compute a third probability that the unreported cell is weaker than the mobile radio terminal sensitivity threshold; and
determining a location of the mobile radio terminal on the basis of at least of the first probability, the second probability and the third probability.
2. The method as claimed in claim 1 , further comprising seeking a network list containing a list of cells that the mobile radio terminal should detect.
3. The method as claimed in claim 2 wherein the network list is a BA list.
4. The method as claimed in claim 3 wherein in the event that the network list is available and the at least one unreported cell is not on the network list, removing the at least one unreported cell from further consideration.
5. A system for locating a mobile radio terminal in a radio communications network, the system comprising at least one processing element configured to:
identify a set of cells about an approximate location of the mobile radio terminal;
identify at least one cell in the set of identified cells that is unreported by the mobile radio terminal, the remaining cells in the identified set being reported; and
determine a maximum number of cells that can be reported by checking a network threshold; wherein
if the reported cells in the identified set exceed the maximum number of cells, the at least one processing element compares interference levels from the reported cells against a level of signal strength of the weakest reported cell and determines a first probability that an unreported cell is weaker than the weakest of the reported cells;
if the reported cells in the identified set do not exceed the maximum number of cells, the at least one processing element computes a maximum interference level from the reported cells in the identified set and determines whether the maximum interference level is greater than a sensitivity threshold of the mobile radio terminal;
if the maximum interference level is greater than the sensitivity threshold, the at least one processing element computes a second probability of the unreported cell being weaker than the maximum interference level; and
if the maximum interference level is not greater than the sensitivity threshold, the at least one processing element computes a third probability that the unreported cell is weaker than the mobile radio terminal sensitivity threshold; wherein the at least one processing element is further configured to:
determine a location of the mobile radio terminal on the basis of at least one of the first probability, the second probability and the third probability.
6. The system as claimed in claim 5 , wherein the at least one processing element is further configured to seek a network list containing a list of cells that the mobile radio terminal should detect.
7. A non-transitory machine readable medium containing instructions to cause a machine to perform the method of any one of claims 1 , 2 , 3 and 4 .