Real-time locating system using gps time difference of arrival with digital off-air access units and remote units

Abstract

A real-time locating system (RTLS) for localization using satellite navigation signals in a Distributed Antenna System includes Off-Air Access Units (OAAUs), each being operable to receive an individual satellite navigation signal from a satellite and to route signals optically to a digital access unit (DAU). Remote digital remote units (DRUs) are located at Remote locations and are operable to receive signals the DAUs. Each individual satellite navigation signal can be appropriately delayed (in a manner that accounts for a DRU's location). For each antenna, a separation distance between a mobile station and a DRU can be estimated based on a signal receipt time at the station. In combination, these distances can be used to estimate the mobile station's precise indoor position.

1 . (canceled) 
     
     
         2 . A method for localization comprising:
 receiving, by an Off-Air Access Unit (OAAU), a first satellite navigation signal and a second satellite navigation signal; and   routing, by the OAAU, the first satellite navigation signal and the second satellite navigation signal to a Digital Remote Unit (DRU) at a location remote from the OAAU;   receiving, by the DRU, the first satellite navigation signal and the second satellite navigation signal from the OAAU;   transmitting the first satellite navigation signal to a first antenna during a first time frame; and   transmitting the second satellite navigation signal to a second antenna during a second time frame, wherein the second time frame is after the first time frame.   
     
     
         3 . The method of  claim 2  further comprising:
 receiving, by a digital access unit (DAU), the first satellite navigation signal and the second satellite navigation signal from the OAAU; and 
 transmitting the first satellite navigation signal and the second satellite navigation signal from the OAAU to the DRU. 
 
     
     
         4 . The method of  claim 3  wherein the OAAU is connected to the DAU via an Ethernet cable, Optical Fiber, or Wireless Link. 
     
     
         5 . The method of  claim 3  further comprising a plurality of DAUs coupled together via an Ethernet cable, Optical Fiber, or Wireless Link. 
     
     
         6 . The method of  claim 2  wherein the DRU is further configured to determine a first delay amount based on a first feedback loop utilizing a known location of the first antenna and a second delay amount based on a second feedback loop utilizing a second known location of the second antenna. 
     
     
         7 . The method of  claim 2  wherein the DRU further comprises a switch, and wherein transmitting the first satellite navigation signal and the second satellite navigation signal depends on a position of the switch. 
     
     
         8 . The method of  claim 7  further comprising:
 configuring the switch to be in a second position; and 
 transmitting, by the switch in the second position, the first satellite navigation signal to the second antenna. 
 
     
     
         9 . The method of  claim 2  wherein the first satellite navigation signal and the second satellite navigation signal comprise a GPS, GLONASS, Galileo, QZSS, or BeiDou signal. 
     
     
         10 . A method for indoor localization comprising:
 receiving, at a mobile station, a one or more signals from one or more base stations, wherein each base station of the one or more base stations is associated with a GPS position;   determining a transmission time and a receive time associated with each signal of the one or more signals from the one or more base stations;   determining a time difference associated with each of the one or more signals based on the transmission time and the receive time for each of the one or more signals from the one or more base stations;   determining a position of the mobile station using the time difference associated with each of the one or more signals and the GPS position of a base station associated with each of the one or more signals;   transmitting the position of the mobile station causing a second device to determine a distance separating the mobile station and the second device; and   receiving a message from the second device based on the distance separating the mobile station and the second device.   
     
     
         11 . The method of  claim 10  wherein the one or more base stations are configured to transmit the one or more signals at time-synchronized intervals. 
     
     
         12 . The method of  claim 10  wherein receiving the one or more signals from the one or more base stations further comprises:
 receiving a plurality of delayed satellite signals from a first base station of the one or more base stations; and 
 determining a first GPS position associated with the first base station of the one or more base stations. 
 
     
     
         13 . The method of  claim 12  wherein receiving the one or more signals from the one or more base stations further comprises:
 receiving a second plurality of delayed satellite signals from a second base station of the one or more base stations; and 
 determining a second GPS position associated with the second base station of the one or more base stations. 
 
     
     
         14 . The method of  claim 10  wherein determining the transmission time and the receive time associated with each of the one or more signals from the one or more base stations further comprises:
 analyzing each signal of the one or more signals to determine the transmission time, wherein each signal identifies the transmission time; and 
 detecting, by the mobile station, the receive time associated with each signal of the one or more signals based on a time of arrival of the one or more signals. 
 
     
     
         15 . The method of  claim 10  wherein the message from the second device is based on a threshold distance. 
     
     
         16 . The method of  claim 10  further comprising receiving an indication from a user that identifies the second device. 
     
     
         17 . The method of  claim 10  further comprising transmitting, by the mobile station, the message from the second device.