AUTONOMOUS ULTRASONIC INDOOR LOCATION SYSTEM, APPARATUS AND METHOD

• US 20090295639A1
• Filed: 05/28/2009
• Published: 12/03/2009
• Est. Priority Date: 05/29/2008
• Status: Active Grant

• Current Assignee: NEC Company Limited
• Original Assignee: NEC Company Limited
• Inventors: Wang, Yongcai, Zhao, Junhui
• Granted Patent: US 8,203,910 B2
• Time in Patent Office: Days
• US Class Current: 342/387
• CPC Class Codes: G01S 11/16 using difference in transit time between electrical and acoustic signals
• CPC Class Codes: G01S 5/30 Determining absolute distances from a plurality of spaced points of known location

Abstract

An autonomous ultrasonic indoor location system includes a location beacon transmitting apparatus and a location beacon receiving apparatus. The location beacon transmitting apparatus is configured to sequentially transmit US signals at a predetermined time interval upon transmission of a signal containing synchronization information. The location beacon receiving apparatus is configured to synchronize with the location transmitting apparatus when synchronization information is detected, determine transmission order of the received US signals based on the obtained synchronization timing, infer transmission timings of the respective US signals based on the determined transmission order, calculate TOA information corresponding to each of the received US signal from the transmission timings and reception timings of the respective US signals, and determine location of the location beacon receiving apparatus on basis of the positions of the US transmitters in the transmitting apparatus and the calculated TOA information sequence.

Claims

1. A location-beacon transmitting apparatus, comprising

a first-signal transmitter for transmitting a first-signal containing synchronization information;

a plurality of second-signal transmitters; and

a second-signal transmission controlling means for controlling the plurality of second-signal transmitters to sequentially transmit second-signals in a predetermined order at a predetermined time-interval upon the transmission of the first-signal.

2. The transmitting apparatus according to claim 1, wherein the first-signal transmitter further transmits part or all of the following additional information:

transmitter-position determination information about the plurality of second-signal transmitters, information indicating the predetermined time-interval, and a backoff time which is a time delay between a transmission timing of the first transmitted second-signal and a transmission timing of the first-signal.

3. The transmitting apparatus according to claim 2, wherein the transmitter-position determination information is a structure information of the plurality of second-signal transmitters or a position information of the plurality of second-signal transmitters.

4. The transmitting apparatus according to claim 1, wherein the first-signal is a radio-frequency signal, a microwave signal or an infrared signal, and the second-signal is an ultrasonic signal.

5. The transmitting apparatus according to claim 1, wherein the plurality of second-signal transmitters have a predetermined topology structure.

6. The transmitting apparatus according to claim 1, wherein the first-signal transmitter transmits the first-signal containing the synchronization information periodically.

7. A location-beacon receiving apparatus for receiving a location-beacon from a transmitting apparatus, comprising

a first-signal receiver for receiving a first-signal containing synchronization information;

a second-signal receiver for sequentially receiving second-signals;

a synchronizing unit for synchronizing with the transmitting apparatus utilizing the synchronization information contained in the first-signal and obtaining a synchronization timing;

an order identification unit for identifying a transmission order for the respective second-signals received by the second-signal receiver based on the synchronization timing;

a TOA acquisition unit for acquiring a TOA information sequence corresponding to the respective second-signals based on the transmission order of the respective second-signals identified by the order identification unit; and

a position calculation unit for calculating the position of the receiving apparatus based on the positions of the transmitting sources of the respective second-signals received by the second-signal receiver and the TOA information sequence acquired by the TOA acquiring unit.

8. The receiving apparatus according to claim 7, wherein the first-signal is a radio-frequency signal, a microwave signal or an infrared signal, and the second-signal is an ultrasonic signal.

9. The receiving apparatus according to claim 7, wherein the first-signal receiver further receives part or all of a transmitting-source position determination information for the transmitting sources of the respective second-signals, a transmission time-interval information of the second-signal transmitting sources, and a backoff time which is a time delay between a transmission timing of the first transmitting source and a transmission timing of the first-signal containing the synchronization information.

10. The receiving apparatus according to claim 7, further comprising a memory which stores in advance part or all of a transmitting-source position determination information for the transmitting sources of the respective second-signals, a transmission time-interval information of the second-signal transmitting sources, and a backoff time which is a time delay between a transmission timing of the first transmitting source and a transmission timing of the first-signal containing the synchronization information.

11. The receiving apparatus according to claim 9, wherein the transmitting-source position determination information is a structure information of the transmitting sources of the respective second-signals or a position information of the transmitting sources of the respective second-signals, and the position calculation unit determines the positions of the transmitting sources of the respective second-signals based on the structure information or the position information.

12. The receiving apparatus according to claim 11, wherein the order identification unit comprises

a transmission ordinal number determination part which divides a time period that begins from the transmission timing of the first second-signal transmitting source into n intervals at the transmission time-interval and determines that the transmission ordinal number of a received second-signal is i if the reception timing of the second-signal is in the ith interval, where n is the number of the second-signal transmitting sources and i=1, 2, . . . , n;

and

a second-signal transmission timing inferring part for inferring a transmission timing for each of the received second-signals based on the transmission ordinal numbers determined by the transmission ordinal number determination part.

13. The receiving apparatus according to claim 12, wherein the TOA acquisition unit calculates the TOA information sequence corresponding to the respective second-signals by subtracting the transmission timings of the respective received second-signal from the reception timings of the respective second-signals.

14. The receiving apparatus according to claim 12, wherein the transmission timing of the first second-signal transmitting source is the synchronization timing or a timing that is obtained by adding the backoff time to the synchronization timing.

15. The receiving apparatus according to claim 14, wherein the synchronization unit comprises a bit-synchronization part for compensating a bit-synchronization error by using a bit-synchronization technique and obtaining a corrected-synchronization timing through subtracting the bit-synchronization error from the synchronization timing.

16. The receiving apparatus according to claim 7, a time period from when the first-signal receiver receives the first first-signal to when the first-signal receiver receives the second first-signal is an emission period, wherein the position calculation unit comprises

a consecutive triangulation part for applying a three-length sliding window along the TOA information sequence acquired by the TOA acquisition unit and calculating in real time the position of the receiving apparatus based on three temporal-neighboring TOA information samples in an emission period and the positions of the transmitting sources of the respective second-signals by triangulation, thereby obtaining a series of position information of the receiving apparatus in the emission period;

and

a consecutive median filter part for removing any outlier from the series of position information to obtain a plurality of real-time positions of the receiving apparatus in the emission period.

31. The receiving apparatus according to claim 10, wherein the transmitting-source position determination information is a structure information of the transmitting sources of the respective second-signals or a position information of the transmitting sources of the respective second-signals, and the position calculation unit determines the positions of the transmitting sources of the respective second-signals based on the structure information or the position information.

17. A method for transmitting a location-beacon comprising the steps of

transmitting a first-signal containing synchronization information;

and

transmitting sequentially second-signals in a predetermined order at a predetermined time-interval upon transmission of the first-signal.

18. The method according to claim 17, further comprising transmitting part or all of the following additional information:

transmitter-position determination information for a plurality of second-signal transmitters which transmit sequentially the second-signals, information indicating the predetermined time-interval, and a backoff time that is a time delay between a transmission timing of the first transmitted second-signal and a transmission timing of the first-signal containing the synchronization information.

19. The method according to claim 18, wherein the transmitter-position determination information is a structure information of the plurality of second-signal transmitters or a position information of the plurality of second-signal transmitters.

20. The method according to claim 18, wherein the first-signal is a radio-frequency signal, a microwave signal or an infrared signal, and the second-signal is an ultrasonic signal.

21. The method according to claim 18, wherein the first-signal containing the synchronization information is transmitted periodically.

22. A method for receiving a location beacon in a receiving apparatus from a transmitting apparatus, comprising the steps of

receiving a first-signal containing synchronization information, synchronizing with the transmitting apparatus by utilizing the synchronization information, and obtaining a synchronization timing;

sequentially receiving second-signals;

identifying a transmission order for the respective second-signals received based on the synchronization timing;

acquiring a TOA information sequence corresponding to the respective second-signal based on the identified transmission order; and

calculating the position of the receiving apparatus according to the positions of the transmitting sources of the respective second-signals and the acquired TOA information sequence.

23. The method according to claim 22, wherein the first-signal is a radio-frequency signal, a microwave signal or an infrared signal, and the second-signal is an ultrasonic signal.

24. The method according to claim 22 further comprising a step of

receiving or locally storing in advance part or all of a transmitting-source position determination information for the transmitting sources of the respective second-signal, a transmission time-interval information of the second-signal transmitting sources, and a backoff time that is a time delay between a transmission timing of the first transmitting source and a transmission timing of the first-signal.

25. The method according to claim 24, wherein the transmitting-source position determination information is a structure information of the transmitting sources of the respective second-signals or a position information of the transmitting sources of the respective second-signals, and in the step of calculating the position of the receiving apparatus, the positions of the transmitting sources of the respective second-signals are determined based on the structure information or the position information.

26. The method according to claim 25, wherein the step of identifying the transmission order for the respective second-signal received comprises

dividing a time period that begins from the transmission timing of the first second-signal transmitting source into n intervals at the transmission time-interval and determining that the transmission ordinal number of a received second-signal is i if the reception timing of this second-signal is in the ith interval, where n is the number of the second-signal transmitting sources and i=1, 2, . . . , n;

and

inferring transmission timings for each of the received second-signals based on the transmission ordinal numbers determined in the step of determining the transmission ordinal numbers of the second-signals.

27. The method according to claim 26, wherein

in the step of acquiring the TOA information sequence, the TOA information sequence corresponding to the respective second-signals is calculated by subtracting the transmission timings of the respective received second-signals from the reception timings of the corresponding second-signals.

28. The method according to claim 26, wherein the transmission timing of the first second-signal transmitting source is the synchronization timing or a timing which is obtained by adding the backoff time to the synchronization timing.

29. The method according to claim 28, wherein the step of obtaining the synchronization timing comprises compensating a bit-synchronization error by using a bit-synchronization technique and obtaining a corrected-synchronization timing through subtracting the bit-synchronization error from the synchronization timing.

30. The method according to claim 22, a time period from when the first first-signal is received to when the second first-signal is received is an emission period, wherein the step of calculating the position of the receiving apparatus comprises

a step of consecutive triangulation in which a three-length sliding window is applied along the TOA information sequence acquired in the step of acquiring the TOA information sequence, and the position of the receiving apparatus is calculated in real time based on three temporal-neighboring TOA information samples in an emission period and the positions of the transmitting sources of the respective second-signals by triangulation, thereby a series of position information of the receiving apparatus in the emission period is obtained;

and

a step of consecutive median filtering in which any outlier is removed from the series of position information to obtain a plurality of real-time positions of the receiving apparatus in the emission period.