RFID system, reader-writer, and RFID tag

1. A radio frequency identification (RFID) system, comprising:

a plurality of RFID a tags, each having a tag antenna and a tag circuit that stores identification information; and

a reader-writer including a first transceiver that reads the identification information of the plurality of RFID tags using an antenna,

wherein, when the identification information is not read from one of the plurality of RFID tags due to an occurrence of a reading error in the first transceiver after a reading command for reading the identification information is transmitted from the first transceiver via the antenna, the reader-writer adds reading error information, which indicates the occurrence of the reading error, to a next reading command to be transmitted, and transmits the next reading command from the first transceiver via the antenna, and

wherein each of the plurality of RFID tag includes:

a reading error detector that analyzes the reading error information added to the reading command to determine whether the reading error occurs;

a reading-completion flag that indicates information on whether the identification information is completely read by the reader-writer; and

a controller that sets the reading-completion flag based on a determination result of the reading error detector.

2. The RFID system according to claim 1 , wherein the controller

sets the reading-completion flag to a reading-incompletion state when the reading error is detected by the reading error detector, and

sets the reading-completion flag to a reading-completion state when the reading error is not detected by the reading error detector and the identification information is completely read by the reader-writer.

3. The RFID system according to claim 2 , wherein the controller replies to a subsequent reading error when the reading-completion flag indicates the reading-incompletion state and does not reply to the subsequent reading error when the reading-completion flag indicates the reading-completion state.

4. The RFID system according to claim 1 , wherein the reading error information is 1-bit information.

5. A radio frequency identification (RFID) system, comprising:

a plurality of RFID tags, each having a tag antenna and a tag circuit that stores identification information; and

a reader-writer including a first transceiver that reads the identification information of the plurality of RFID tags using an antenna,

wherein, when the identification information is not read from one of the plurality of RFID tags due to an occurrence of a reading error in the first transceiver after a reading command for reading the identification information is transmitted from the first transceiver via the antenna, the reader-writer adds reading error information, which indicates the occurrence of the reading error, to a next reading command to be transmitted and transmits the next reading command from the first transceiver via the antenna,

wherein the tag circuit of each of the plurality of RFID tags includes a second transceiver that communicates with the reader-writer via the tag antenna, a presence signal transmitter that returns a presence signal to the reader-writer via the second transceiver when the reading command is received from the reader-writer via the second transceiver, and a memory that stores the identification information, and

wherein the reader-writer includes a presence signal detector that detects the presence signal returned from the plurality of RFID tags via the antenna and the first transceiver after transmitting the reading command to the plurality of RFID tags, and a controller that controls a process of collecting the identification information based on the presence signal detected by the presence signal detector, the controller ending the process of collecting the identification information when the presence signal is not detected by the presence signal detector.

6. The RFID system according to claim 5 , wherein the reader-writer includes a division number specifier that specifies a division number of time slots, and the controller controls the division number to be specified by the division number specifier based on a magnitude of the presence signal detected by the presence signal detector.

7. The RFID system according to claim 6 , wherein the controller increases the division number when the magnitude of the presence signal is greater than a predetermined detected value and decreases the division number when the magnitude of the presence signal is less than the predetermined detected value.

8. The RFID system according to claim 5 , wherein the tag circuit includes a reading-completion flag that indicates information on whether the identification information is completely read by the reader-writer and a controller that performs a control based on the information of the reading-completion flag, and

the controller stops returning the presence signal in response to the reading command when the reading-completion flag includes the information indicating the reading-completion state.

9. The RFID system according to claim 5 , wherein the tag circuit includes a controller that controls a return of the presence signal based on slot counter information, and

the controller stops returning the presence signal in response to the reading command after the slot counter information is 0 in a predetermined round.

10. The RFID system according to claim 5 , wherein the reading error information is 1-bit information.

11. A radio frequency identification (RFID) system comprising:

a plurality of RFID tags, each having a tag antenna and a tag circuit that stores identification information; and

a reader-writer including a first transceiver that reads the identification information of the plurality of RFID tags using an antenna,

wherein, when the identification information is not read from one of the plurality of RFID tags due to an occurrence of a reading error in the first transceiver after a reading command for reading the identification information is transmitted from the first transceiver via the antenna, the reader-writer adds reading error information, which indicates the occurrence of the reading error, to a next reading command to be transmitted and transmits the next reading command from the first transceiver via the antenna,

wherein each of the plurality of RFID tags includes a reading-completion flag that indicates whether the identification information is completely read, an auxiliary flag that indicates whether the reading-completion flag is initialized, and a controller that sets one of the reading-completion flag and the auxiliary flag, and

wherein the reader-writer includes an auxiliary reset command transmitter that transmits an auxiliary reset command to the plurality of RFID tags for initializing the reading-completion flag based on a state of the auxiliary flag.

12. The RFID system according to claim 11 , wherein the auxiliary flag indicates initialization when a corresponding RFID tag receives the auxiliary reset command.

13. The RFID system according to claim 11 , wherein the controller initializes the reading-completion flag based on the auxiliary reset command when the auxiliary flag indicates non-initialization.

14. The RFID system according to claim 11 , wherein the controller sets the auxiliary flag to indicate non-initialization when the reading-completion flag is switched to a reading-completion state from a reading-incompletion state.

15. The RFID system according to claim 11 , wherein the auxiliary flag is switched to a non-initialized state in a predetermined time after the auxiliary flag is set to indicate an initialization.

16. The RFID system according to claim 11 , wherein the reading error information is 1-bit information.

17. A radio frequency identification tag, comprising:

a tag antenna; and

a tag circuit that stores identification information,

wherein the tag circuit includes a transceiver that reads a reading command transmitted from a reader-writer via the tag antenna, a reading error detector that analyzes reading error information of the identification information added to the reading command read by the transceiver to determine whether a reading error occurs, a reading-completion flag that indicates whether the identification information is completely read by the reader-writer, and a controller that sets the reading-completion flag based on a determination result of the reading error detector, and

wherein the controller sets the reading-completion flag to a reading-incompletion state when the reading error is detected by the reading error detector, and sets the reading-completion flag to a reading-completion state when the reading error is not detected by the reading error detector and the identification information is completely read by the reader-writer.