Synchronization method between reader and tag

• US 8,274,374 B2
• Filed: 11/05/2008
• Issued: 09/25/2012
• Est. Priority Date: 12/17/2007
• Status: Expired due to Fees

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Kim, Hyunseok, Lee, Heyung Sub, Seong, Nak Seon, Pyo, Cheol Sig, Chae, Jong-Suk, Choi, Su Na
• Primary Examiner(s): Bugg, George
• Assistant Examiner(s): Dorsey, Renee
• Application Number:
  US12/265,205
• Publication Number:
  US 20090153309A1
• Time in Patent Office: 1,420 Days
• Field of Search: None
• US Class Current: 340/10.5
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer

Abstract

Disclosed is a synchronization method between a reader and tag according to an example embodiment, the method including: transmitting, by the reader, a first write command message to the tag at a first time; detecting, by the tag, the first write command message from the reader at a second time and transmitting a first response message to the reader in response to the first write message; transmitting, by the reader, a second write command message including first time information of the first time to the tag; and correcting, by the tag, a clock offset using a difference between the first time and the second time.

Claims

1. A synchronization method between a reader and a tag, wherein the reader comprises a reader clock, and wherein the tag comprises a tag clock, the method comprising:

transmitting, by the reader, a first write command message to the tag at a first time of the reader clock;

detecting, by the tag, the first write command message from the reader at a second time of the tag clock, and transmitting a first response message to the reader in response to the first write message;

transmitting, by the reader, a second write command message including first time information of the first time to the tag;

adjusting a time of the tag clock by a first value, wherein the first value equals the difference between the first time and the second time;

transmitting, by the tag, a second response message in response to the second write command message at a seventh time of the tag clock;

detecting, by the reader, the second response message from the tag at an eighth time of the reader clock and recording eighth time information of the eighth time in a memory region;

transmitting, by the reader, a third write command message including the eighth time information to the tag at a ninth time of the reader clock;

receiving, by the tag, the third write command message from the reader at a tenth time of the tag clock; and

adjusting a time of the tag clock by a second value, wherein the second value equals one half of the difference between the seventh time and the eighth time.

2. The method of claim 1, wherein the reader and the tag respectively include a Real Time Clock (RTC), and the first adjusting comprises the tag adding the first value to the present time of the tag RTC, or subtracting the first value from the present time of the tag RTC.

3. The method of claim 1, wherein the reader records, in a memory region, the first time information of the first time, fourth time information of a fourth time, the fourth time being a time of the reader clock when the first response message is received from the tag, and fifth time information of a fifth time, the fifth time being a time of the reader clock when the second write command message is transmitted to the tag.

4. The method of claim 1, wherein the tag records the first time information of the first time, second time information of the second time, third time information of a third time, the third time being a time of the tag clock when the first response message is transmitted to the reader, and sixth time information of a sixth time, the sixth time being a time of the tag clock when the second write command message is received from the reader.

5. The method of claim 1, wherein the second adjusting comprises:

adding the second value to the tenth time or subtracting the second value from the tenth time.

12. The method of claim 1, wherein the tag is attached to an object and comprises one or more sensors configured to store time and environment information associated with the object, and wherein the reader is configured to track the location of the object by receiving the time and environment information from the tag.

13. The method of claim 1, wherein the distance between the tag and the reader is unknown, to the reader and to the tag, at the time of the first adjusting.

6. A synchronization method between a reader and tag, wherein the reader comprises a reader clock, and wherein the tag comprises a tag clock, the method comprising:

transmitting a second write command message including first time information of a first time to the tag at a fifth time of the reader clock, wherein the reader receives a first response message from the tag at a fourth time of the reader clock in response to a first write command message transmitted to the tag at the first time of the reader clock;

adjusting a time of the tag clock by a first value, wherein the first value equals the difference between a second time and the first time, the second time being a time of the tag clock when the tag receives the first write command message from the reader;

transmitting, by the tag, a second response message to the reader at a seventh time of the tag clock in response to the second write command message;

transmitting a third write command message including eighth time information of an eighth time of the reader clock at a ninth time of the reader clock, wherein the reader receives the second response message from the tag at the eighth time; and

adjusting a time of the tag clock by a second value, wherein the second value equals one half of the difference between the seventh time and the eighth time.

7. The method of claim 6, wherein the message delay time is generated between the fourth time and the fifth time and between the eighth time and the ninth time.

8. The method of claim 6, the second adjusting comprising:

adding the second value to a tenth time or subtracting the second value from the tenth time, wherein the tenth time is a time of the tag clock when the tag receives the third write command message from the reader.

14. The method of claim 6, wherein the distance between the tag and the reader is unknown, to the reader and to the tag, at the time of the first adjusting and at the time of the second adjusting.

9. A synchronization method between a reader and a tag, wherein the reader comprises a reader clock, and wherein the tag comprises a tag clock, the method comprising:

transmitting, by the reader, a first read command message including first time information to the tag at a first time of the reader clock;

transmitting a first response message including second time information to the reader at a third time of the tag clock, the second time information being information of a second time, the second time being a time of the tag clock when the tag detects the first read command message from the reader;

adjusting a time of the reader clock by a first value, wherein the first value equals the difference between the first time and the second time

transmitting, by the reader, a second read command message to the tag at a fifth time of the reader clock;

transmitting a second response message including third time information of the third time to the reader at a seventh time of the tag clock in response to the second read command message, wherein the tag receives the second read command message from the reader at a sixth time of the tag clock; and

adjusting a time of the reader clock by a second value, wherein the second value equals one half of the difference between the third time and a fourth time, wherein the fourth time is a time of the reader clock when the reader receives the first response message from the tag.

10. The method of claim 9, wherein the first adjusting comprises:

adding the first value to the present time of the reader clock or subtracting the first value from the present time of the reader clock.

11. The method of claim 9, wherein the second adjusting comprises:

adding the second value to an eighth time or subtracting the second value from the eighth time, wherein the eighth time is a time of the reader clock when the reader receives the second response message from the tag.