Query tree based tag identification method in RFID systems

1. A tag identification method in REID systems including a reader and a plurality of tags, the method comprising the steps of:

(a) forming a temporary ID for each of the tags;

(b) comparing an inquiry of the reader with a portion of the temporary ID in each tag when receiving the inquiry from the reader;

(c) if the inquiry and the portion of the temporary ID are identical to each other, transmitting a remainder of the temporary ID in each tag to the reader;

(d) if a collision occurs in the step (c), generating new inquiries for storing them in the reader;

(e) if there is no collision in the step (c), transmitting an ACK signal to each tag whose temporary ID is identified to receive its real tag ID therefrom; and

(f) repeating the steps (b) to (e) until there is no inquiry in the reader,

wherein, in step (d), in case the tag responds with only a last bit of its temporary ID after step (c), the reader identifies two temporary IDs if there is any collision.

2. The tag identification method in REID systems of claim 1 , wherein the inquiry includes n-bit and the portion of the temporary ID includes first n-bit of the temporary ID.

3. The tag identification method in REID systems of claim 2 , wherein the remainder of the temporary ID includes (n+1)- th bit to last bit of the tag ID without the first n-bit.

4. The tag identification method in REID systems of claim 1 , wherein the new inquiry includes two inquiries which are formed by adding ‘0’ and ‘1’ to the inquiry.

5. The tag identification method in REID systems of claim 1 , wherein the ACK signal includes the code indicating the status of ACK.

6. The tag identification method in REID systems of claim 1 , wherein the ACK signal is used for security and authentication and includes the status of ACK and the temporary ID added thereto.

7. The tag identification method in REID systems of claim 1 , wherein the temporary ID includes 16-bit.