Tag Frequency Control

• US 20080039023A1
• Filed: 05/31/2005
• Published: 02/14/2008
• Est. Priority Date: 06/02/2004
• Status: Active Grant

• Current Assignee: Ubisense Incorporated (IQGeo Group Plc)
• Original Assignee: Ubisense Incorporated (IQGeo Group Plc)
• Inventors: Ward, Andrew
• Granted Patent: US 8,045,930 B2
• Time in Patent Office: Days
• US Class Current: 455/73
• CPC Class Codes: H04B 1/7183 Synchronisation
• CPC Class Codes: H04W 56/001 Synchronization between nodes
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 56/0035 detecting errors in frequency or phase

Abstract

A communication system comprising one or more transceiver units of a first type and one or more transceiver units of a second type capable of communicating with the transceiver units of the first type; each transceiver unit of the first type comprising: a frequency comparison unit for comparing the frequency of a signal received from a transceiver unit of the second type with a reference frequency; a feedback signal generator for generating a feedback signal dependent on the result of that comparison; and a transmitter for transmitting that signal to the transceiver unit of the second type; and each transceiver unit of the second type comprising: a local frequency reference unit on which the frequency of signals transmitted by it are dependent; and a frequency adjustment unit for receiving the feedback signal and adjusting the local frequency reference unit in dependence on the feedback signal.

Claims

1. A communication system comprising one or more transceiver units of a first type and one or more transceiver units of a second type capable of communicating with the transceiver units of the first type;

each transceiver unit of the first type comprising;

a frequency comparison unit for comparing the frequency of a signal received from a transceiver unit of the second type with a reference frequency;

a feedback signal generator for generating a feedback signal dependent on the result of that comparison; and

a transmitter for transmitting that signal to the transceiver unit of the second type; and

each transceiver unit of the second type comprising;

a local frequency reference unit on which the frequency of signals transmitted by it are dependent; and

a frequency adjustment unit for receiving the feedback signal and adjusting the local frequency reference unit in dependence on the feedback signal.

2. A communication system as claimed in claim 1, wherein each transceiver unit of the first type is arranged to, during a communication session with a transceiver unit of the second type, repeatedly perform the said comparison, generate a feedback signal as a result of that comparison and transmit that signal to the said transceiver unit of the second type.

3. A communication system as claimed in claim 1, wherein the frequency adjustment unit comprises a memory and a storage unit for storing in the memory adjustment data dependent on the feedback signal, and is arranged to adjust the local frequency reference unit in dependence on the adjustment data.

4. A communication system as claimed in claim 3, wherein the memory is arranged to store the adjustment data for use after the completion of a communication session with a transceiver unit of the first type.

5. A communication system as claimed in claim 1, comprising:

at least one transceiver unit of a third type with which the transceivers of the second type are capable of communicating; and

a database accessible to the transceiver units of the first type and the transceiver units of the third type;

and wherein;

the transceiver units of the first type are arranged to, on comparing the frequency of a signal received from a transceiver unit of the second type with the reference frequency, store in the database an indication of the result of that comparison together with an identity of that transceiver unit of the second type; and

each transceiver unit of the third type comprises;

a local frequency reference unit on which the operating frequency of that transceiver unit is dependent; and

a frequency adjustment unit for, on receiving a signal from a transceiver unit of the second type for which the database holds an indication of the result of a comparison, comparing the frequency of that signal with the frequency of the respective local frequency reference unit and adjusting the frequency reference unit in accordance with that comparison.

6. A communication system as claimed in claim 5, wherein the frequency adjustment unit of the transceiver unit of the third type is arranged to perform the said adjustment only if the indication held in the database meets at least one further criterion.

7. A communication system as claimed in claim 1, wherein the feedback signal generator is arranged to generate the feedback signal dependent on the result of a plurality of comparisons of the frequency of a signal received from the transceiver unit of the second type with the reference frequency.

8. A communication system as claimed in claim 7, wherein the said comparisons are performed over a period of at least 24 hours.

10. A communication system as claimed in claim 8, wherein the or each transceiver unit of the first type is arranged to communicate with a single one of the transceiver units of the second type at any one time.

13. A communication system as claimed in claim 1, wherein each transceiver unit of the first type is a base station.

14. A communication system as claimed in claim 1, wherein each transceiver unit of the second type is an identification unit.

15. A communication system as claimed in claim 14, wherein each transceiver unit of the second type has a unique identity within the system.

16. A communication system as claimed in claim 15, wherein each transceiver unit of the second type is a mobile transceiver.

17. A communication system as claimed in claim 16, wherein each transceiver unit of the second type is a radio tag.

18. A communication system as claimed in claim 1 wherein each transceiver unit of the second type comprises a power source.

19. A communication system as claimed in claim 1, wherein the system is a locationing system and is capable of determining the location of a transceiver unit of the second type relative to the or each transceiver unit of the first type.

20. A communication system as claimed in claim 1, wherein communication between the transceiver units of the first type and the transceiver units of the second system is by ultrawideband radio.

21. A communication system as claimed in claim 1, wherein the communication system is such that each transceiver unit of the second type can establish communication with each transceiver unit of the first type only if the operating frequencies of those transceiver units are synchronised to better than 2 ppm.

22. A communication system as claimed in claim 1, wherein the or each local frequency reference unit is an oscillator and the or each frequency adjustment unit is capable of altering the oscillation frequency of the oscillator.

9. A communication system comprising:

one or more transceiver units of a first type;

a data store accessible to the or each transceiver unit of the first type;

two or more transceiver units of a second type, the transceiver units of a second type being capable of communicating with the transceiver units of the first type, and each transceiver unit of the second type comprising a local frequency reference unit on which the frequency of signals transmitted by it are dependent;

wherein;

at least one transceiver unit of the first type comprises a frequency comparison unit for comparing the frequency of a signal received from a transceiver unit of the second type with a reference frequency, and a feedback data storage unit for storing in the data store feedback data representative of the result of that comparison in respect of that transceiver unit of the second type; and

the or each transceiver unit of the first type comprises a frequency adjustment unit for adjusting the transmit and/or receive frequency of the transceiver unit of the first type for communication with one of the transceiver units of the second type in accordance with feedback data stored in respect of that transceiver unit of the second type.

11. A communication system comprising:

one or more transceiver units of a first type;

two or more transceiver units of a second type, the transceiver units of a second type being capable of communicating with the transceiver units of the first type, and each transceiver unit of the second type comprising a local frequency reference unit on which the frequency of signals transmitted by it are dependent;

wherein at least one transceiver unit of the first type comprises;

a frequency comparison unit for comparing the frequency of signals received from transceiver units of the second type with a reference frequency and forming an offset signal representative of the average offset between the frequency of the received signals and the reference frequency;

a frequency adjustment unit for adjusting the reference frequency in accordance with the offset signal.

12. A communications system comprising:

one or more transceivers of a first type;

a database accessible to the transceiver units of the first type;

one or more transceiver units of a second type, the transceiver units of a second type being capable of communicating with the transceiver units of the first type, and each transceiver unit of the second type comprising a local frequency reference unit on which the frequency of signals transmitted by it are dependent;

wherein at least two of the transceiver units of the first type comprise a local frequency reference unit;

a frequency comparison unit for comparing the frequency of signals received from a transceiver unit of the second type with the local frequency reference and storing an offset signal based on that comparison in the database; and

a processing unit capable of accessing the database and, for each transceiver of the second type, forming a signal representative of the average of the offset signals stored in the database for that transceiver and communicating that offset signal to that transceiver.

23. A method of adjusting a local frequency reference of a transceiver unit in a communication system comprising one or more transceiver units of a first type and one or more transceiver units of a second type capable of communicating with the transceiver units of the first type;

the method comprising;

comparing the frequency of a signal received from a transceiver unit of the second type with a reference frequency;

generating a feedback signal dependent on the result of that comparison;

transmitting that signal to the transceiver unit of the second type; and

at the transceiver unit of the second type;

receiving the feedback signal; and

adjusting a local frequency reference unit on which the frequency of signals transmitted by the transceiver unit of the second type are dependent in dependence on the feedback signal.

24. A method for adjusting the transmit and/or receive frequency of a transceiver unit in a communication system comprising one or more transceiver units of a first type, the transceiver units of a second type being capable of communicating with the transceiver units of the first type;

the method comprising;

comparing the frequency of a signal received by a transceiver of the first type from a transceiver unit of the second type with a reference frequency;

storing feedback data representative of the result of that comparison in respect of that transceiver unit of the second type; and

adjusting the transmit and/or receive frequency of the transceiver unit of the first type for communication with one of the transceiver units of the second type in accordance with feedback data stored in respect of that transceiver unit of the second type.

25. A method for adjusting a reference frequency of a transceiver unit in a communication system comprising one or more transceiver units of a first type, and two or more transceiver units of a second type, the transceiver units of the second type being capable of communicating with the transceiver units of the first type, each transceiver unit of the second type comprising a local frequency reference unit on which the frequency of signals transmitted by it are dependent;

the method comprising;

comparing the frequency of signals received from transceiver units of the second type with a reference frequency;

forming an offset signal representative of the average offset between the frequency of the received signals and the reference frequency; and

adjusting the reference frequency in accordance with the offset signal.