Patent ID: 9231699
Filing Date: 2016-01-05
CPC Classification: G01S,H04B,H04W

Claim Text:
1. A system for determining a location of a portable device, the system comprising: a plurality of stationary infrared (IR) base stations grouped into at least first and second groups, each group including multiple IR base stations, the IR base stations in each group being configured to receive timing synchronization information and, at a common predetermined time based on the received timing synchronization information, to transmit corresponding IR location codes, each IR location code representative of a location of the corresponding IR base station, wherein the IR base stations in the different groups are configured to transmit their corresponding IR location codes at respectively different predetermined times based on the received timing synchronization information; a plurality of portable devices, each portable device configured to detect the IR location codes transmitted by the respective IR base stations and, if one of the IR location codes is detected, transmit an output signal including a portable device ID representative of the portable device and the detected IR location code; and at least one radio frequency (RF) transceiver configured to periodically provide, upon a request, the timing synchronization information to the respective IR base stations relative to a unified time of origin.