Geo-location using distributed composite GPS signals
View Patent ↗A wireless communication arrangement provides GPS coverage in areas where GPS satellites or macrocells are not directly detectable by a mobile station that is used for placing an emergency call. A detector detects a plurality of GPS satellites and provides a composite GPS signal that is re-radiated through a distributed antenna system to provide GPS signal coverage within a selected area such as inside of a building. The signal reach at each re-radiator assembly is individually controlled to keep the composite GPS signal coverage area within a selected limit. A mobile station used to place an emergency call reports the composite GPS signal information in a data call or SMS message that is associated with the emergency voice call. That information is then used for GEO-location to determine the location of the mobile station. A disclosed example includes a technique for addressing a scenario where a mobile station directly detects a satellite and detects the composite GPS signal.
1. A method of handling an emergency call from a mobile station, comprising:
receiving an emergency call from a mobile station in a location where the mobile station does not directly detect enough global positioning system (GPS) satellites or enough macrocells to provide location information;
receiving an indication of at least a composite GPS signal that was detected by the mobile station at the location, the composite OPS signal being based on information regarding GPS satellites, wherein the received indication is based on a number of satellites; and
determining the location of the mobile station from the received indication by
determining whether the received indication provides sufficient information for locating the mobile station;
determining possible mobile station locations from information regarding each of a plurality of subcombinations of the number of satellites; and
selecting one of the possible mobile station locations that corresponds to a known location as the location of the mobile station.
2. The method of claim 1 , comprising
removing one of the number of satellites from consideration to establish a first subset of the satellites during one attempt at determining the possible mobile station locations; and
subsequently removing a different one of the number of satellites from consideration to establish a next subset of satellites during another attempt at determining the possible mobile station locations.
3. The method of claim 2 , comprising
performing the subsequently removing until one of the following is achieved
i) each of the number of satellites has been removed from consideration; or
ii) a possible mobile station location that corresponds to an identifiable location is obtained.
4. The method of claim 3 , comprising
using the obtained possible mobile station location as the determined location of the mobile station.
5. The method of claim 3 , comprising
sequentially removing an increasing plurality of the number of satellites from consideration to establish additional subsets of satellites for determining the possible mobile station location; and
continuing the sequentially removing and considering until a possible mobile station location that corresponds to an identifiable location is obtained.