Patent ID: 6819286
Filing Date: 2004-11-16
Classification: G01S

Abstract:
A location determination method for a mobile unit using Bluetooth, the location determination method performed by a location master and a plurality of location subsidiaries, the location determination method comprising the steps of:measuring a first elapsed time, by the location master, between sent and received messages to the mobile unit; measuring at least one of second elapsed times, by the plurality of location subsidiaries, between sent and received messages to the mobile unit; processing by the location master the first and second elapsed times to determine a location of the mobile unit; providing by the location master the location to the mobile unit, said location relative to the location master; sending by the location master a paging message to the mobile unit; responding by the mobile unit to the location master using Bluetooth timing; the step of measuring a first elapsed time further includes a step of recording the first elapsed time between a paging message sent by the location master and the responding by the mobile unit; transferring control by the location master to one of the plurality of location subsidiaries; sending a paging message by the one of the plurality of location subsidiaries to the mobile unit; responding by the mobile unit to the one of the plurality of location subsidiaries using Bluetooth timing; recording by the one of the plurality of location subsidiaries one of the at least one of second elapsed times between the paging message and the responding by the mobile unit; forwarding by the one of the location subsidiaries the one of the at least one of second elapsed times to the location master; determining whether a threshold number of the plurality of location subsidiaries have been used for the location determination method; and if less than the threshold number of location subsidiaries have been used then there is further included the steps of: selecting another location subsidiary of the plurality of location subsidiaries; and iterating the steps of: transferring control, sending a paging message; responding by the mobile unit; recording; forwarding and determining whether the threshold number has been used.