Methods for synchronizing multiple devices and determining location based on the synchronized devices

• US 10,462,762 B2
• Filed: 11/09/2016
• Issued: 10/29/2019
• Est. Priority Date: 11/09/2015
• Status: Active Grant

• Current Assignee: WISER Systems, Inc.
• Original Assignee: WISER Systems, Inc.
• Inventors: Hollar, Seth Edward-Austin
• Primary Examiner(s): Hamza, Faruk
• Assistant Examiner(s): Decker, Cassandra L
• Application Number:
  US15/767,522
• Publication Number:
  US 20180302869A1
• Time in Patent Office: 1,084 Days
• Field of Search: None
• CPC Class Codes: G01S 11/08 using synchronised clocks
• CPC Class Codes: G01S 5/00 Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using active systems G01S13/00, G01S15/00, G01S17/00
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/0263 by combining or switching between positions derived from two or more separate positioning systems
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04H 20/18 Arrangements for synchronising broadcast or distribution via plural systems
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 56/0025 synchronizing potentially movable access points
• CPC Class Codes: H04W 56/006 using known positions of transmitter and receiver
• CPC Class Codes: H04W 56/0065 using measurement of signal travel time
• CPC Class Codes: H04W 56/007 Open loop measurement

Abstract

Methods for synchronizing multiple transceivers to a single master clock are provided including broadcasting a message from a master device, the broadcasted message including a device identification number identifying the master device to at least one known device within range of the master device; receiving the message at the at least one other known device and recording a time of arrival (T_arrival-kd) at the at least one other known device; repeatedly broadcasting and receiving messages and recording associated times of arrival at the at least one other known device; and applying a fit curve to the recorded arrival times to estimate a time of an event. Related devices and systems are also provided.

Claims

1. A method for synchronizing multiple transceivers to a single master clock, the method comprising:

receiving a message broadcast from a master device at at least one known device, the broadcasted message including a departure time in master clock time units (T_DEPART-MD);

recording a time of arrival at the at least one known device in the at least one known device time units (T_ARRIVAL-KD);

repeatedly receiving messages including an associated departure time in master clock time units (T_DEPART-MD) and recording associated times of arrival at the at least one known device in the at least one known device time units (T_ARRIVAL-KD) to provide a plurality of departure time, arrival time pairs (T_DEPART-MD, T_ARRIVAL-KD); and

translating a time of any target event from known device time units to master device time units by applying a fit curve to the departure time, arrival time pairs and applying an offset of a known travel time for a radio frequency signal from the master device to the at least one known device in master clock time units (T_TRAVEL-MD).

2. The method of claim 1, wherein the fit curve is a linear interpolation of at least two of the departure time, arrival time pairs.

3. The method of claim 1, wherein both the master device and the at least one known device are wide band radio frequency devices.

4. The method of claim 1, further comprising:

rebroadcasting the message from the at least one known device, the at least one known device being a rebroadcast device (RD) and the message including a departure time from the rebroadcast device in master clock time units (T_DEPART-RD); and

receiving the rebroadcasted message, at a device that is out of RF range of the master device but within range of the rebroadcast device, such that the device that is out of RF range is synchronized to the master device even when out of RF range using the rebroadcast device as an intermediate master broadcaster.

5. The method of claim 4, further comprising:

rebroadcasting the message from the device that is out of RF range, the device that is out of range being an out of range rebroadcast device (ORRD) and the message including a departure time from the out of range rebroadcast device in master clock time units (T_DEPART-ORRD);

receiving the rebroadcasted message at a second device that is out of RF range of the master device; and

synchronizing the second device that is out of RF range by using the out of range rebroadcast device as an intermediate master broadcaster.

6. The method of claim 1, further comprising:

receiving a plurality of broadcast time synchronization signals at the at least one known device from a plurality of master devices; and

applying a weighting algorithm to the plurality of broadcast time synchronization signals to determine an arrival time of the message.

7. The method of claim 6, wherein applying a weighting algorithm comprises averaging.

8. A known device in a network including a plurality of known devices and a master device, the known device comprising:

a receiver configured to receive a message broadcast from the master device, the broadcasted message including a departure time in master clock time units (T_DEPART-MD); and

a processor configured to;

record a time of arrival of the broadcast message at the known device in the known device time units (T_ARRIVAL-KD);

repeatedly receive messages including an associated departure time in master clock time units (T_DEPART-MD) and record associated times of arrival at the known device in the known device time units (T_ARRIVAL-KD) to provide a plurality of departure time, arrival time pairs (T_DEPART-MD, T_ARRIVAL-KD); and

translate a time of any event from known device time units to master device time units by applying a fit curve to the departure time, arrival time pairs and applying an offset of a known travel time for a radio frequency signal from the master device to the known device in master clock time units (T_TRAVEL-MD).

9. The known device of claim 8, wherein the processor is configured to translate the time of any target event by applying a linear interpolation of at least two of the departure time, arrival time pairs.

10. The known device of claim 8, wherein both the master device and the plurality of known devices are wide band radio frequency devices.

11. The known device of claim 8, wherein the device further comprises a transmitter configured to rebroadcast the message from the known device, the known device being a rebroadcast, device (RD) and the message including a departure time from the rebroadcast device in master clock time units (T_DEPART-RD), such that the rebroadcasted message is received at a device that is out of RF range of the master device but within range of the rebroadcast device and that the device that is out of RF range is synchronized to the master device even when out of RF range using the rebroadcast device as an intermediate master broadcaster.

12. The known device of claim 8:

wherein the receiver is further configured to receive a plurality of broadcast time synchronization signals from a corresponding plurality of master devices; and

wherein the processor is configured to apply a weighting algorithm to the plurality of signals to determine an arrival time of the message.

13. A system including a plurality of devices synchronized to a single master clock, the system comprising:

a plurality of known devices including a processor; and

a master device configured to broadcast a message, the broadcasted message including a departure time in master clock time units (T_DEPART-MD);

wherein at least one of the plurality of known devices receives the broadcasted message and records a time of arrival at the at least one of the plurality of known devices in the at least one of the plurality of known devices time units (T_ARRIVAL-KD);

wherein the master device is configured to repeatedly broadcast messages;

wherein the at least one of the plurality of known devices is configured to repeatedly receive the broadcast messages including an associated departure time in master clock time units (T_DEPART-MD) and record associated times of arrival at the at least one of the plurality of known devices in the at least one of the plurality of known device time units (T_ARRIVAL-KD) to provide a plurality of departure time, arrival time pairs (T_DEPART-MD, T_ARRIVAL-KD); and

wherein a time of any target event is translated from known device time units to master device time units by applying a fit curve to the departure time, arrival time pairs and applying an offset of a known travel time for a radio frequency signal from the master device to the at least one known device in master clock time units (T_TRAVEL-MD).

14. The system of claim 13, wherein the master device and the plurality of known devices are wide band radio frequency devices.

15. The system of claim 13, wherein the plurality of known devices are configured to receive a plurality of broadcast time synchronization signals from a corresponding plurality of master devices and apply a weighting algorithm to the plurality of signals to determine an arrival time of the message.