Method of Preventing Collisions Between Rfid Readers in Rfid System

• US 20090002129A1
• Filed: 01/07/2007
• Published: 01/01/2009
• Est. Priority Date: 01/12/2006
• Status: Active Grant

• Current Assignee: KT&C Co., Ltd.
• Original Assignee: KT&C Co., Ltd.
• Inventors: Shin, Kwang-Yoon
• Granted Patent: US 8,222,997 B2
• Time in Patent Office: Days
• US Class Current: 340/10.100
• 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
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas
• CPC Class Codes: H04W 74/0816 with collision avoidance
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

Disclosed herein is a method of preventing collisions between readers in an RFID system. The method includes a first step of RFID readers selecting transmitting channels by examining channels, a second step of transmitting signals via the selected transmitting channels, a third step of receiving signals via channels having the same frequencies as the selected transmitting channels; a fourth step of determining whether a collision has occurred by examining the status of the signals that are received via the transmitting channels; a fifth step of, if, as a result of the determination at the fourth step, it is determined that a collision between the readers has occurred, repeating the first to fourth steps after delays of random time periods based on a predetermined equation, and a sixth step of, if, as a result of the fourth step, no collision between readers is detected, communicating with the corresponding RFID tags.

Claims

1. A method of preventing collisions between readers in a Radio Frequency Identification (RFID) system, comprising:

a first step of RFID readers selecting transmitting channels by examining channels;

a second step of transmitting signals via the selected transmitting channels;

a third step of receiving signals via channels having same frequencies as the selected transmitting channels;

a fourth step of determining whether a collision has occurred by examining status of the signals that are received via the transmitting channels;

a fifth step of, if, as a result of the determination at the fourth step, it is determined that a collision between the readers has occurred, repeating the first to fourth steps after delays of random time periods based on a predetermined equation; and

a sixth step of, if, as a result of the fourth step, no collision between readers is detected, communicating with the corresponding RFID tags.

2. The method as set forth in claim 1, wherein the fourth step is performed by determining that a collision between the readers has occurred if the status of the signals is noise status.

3. The method as set forth in claim 1, wherein the second step is performed by transmitting data, the third step is performed by receiving data, and the fourth step is performed by comparing the transmitted data with the received data, and determining that a collision has occurred if the transmitted data does not coincide with the received data.

4. The method as set forth in any one of claims 1 to 3, wherein the random time periods of the fifth step are determined by the following equation:

T=n×

t_response

where n is a random number and t_response is a tag response time.