KR20080078266A - Method for recognizing rfid tag in rfid system - Google Patents

Abstract

A method for recognizing an RFID(Radio Frequency IDentification) tag in an RFID system is provided to improve performance of the RFID system by enabling an RFID reader to measure a channel environment between the RFID tag and the RFID reader, and enabling the RFID reader to select an FMO(Flexible Marcoblock Ordering) or Miller encoding mode depending on the measured channel environment. An EMT(Encoding Mode Table) corresponding to a range of a channel environment measurement value is set up(S200). A response signal received from an RFID tag is received(S230). A channel environment between the RFID tag and an RFID reader is measured from the response signal(S240). A new encoding mode is determined corresponding to the measured channel environment measurement value when the measured channel environment measurement value is out of a usual encoding mode range(S270). Set encoding mode information is transmitted to the RFID tag when the new encoding mode is set up(S280).

Description

Tag Recognition Method for Radio Frequency Recognition System {METHOD FOR RECOGNIZING RFID TAG IN RFID SYSTEM}

1 is a block diagram showing the basic configuration of an RFID system according to the prior art.

2 is a block diagram showing the basic operation of the RFID system according to the prior art.

3 is a block diagram showing in more detail the structure of the reader 10 that can be applied to the RFID system according to the present invention shown in FIG.

4A illustrates the basic function of FMO encoding, which is one of the encoding methods when a tag transmits.

4B illustrates an FM0 symbol and sequence.

FIG. 5 illustrates the basic function of Miller encoding, which is one of encoding methods when a tag transmits. FIG.

6 illustrates a subcarrier sequence of Miller encoding.

7 is a flowchart illustrating a communication method of a radio frequency identification (RFID) system according to an embodiment of the present invention.

The present invention relates to a tag recognition method of a radio frequency identification (RFID) system that reads or records identification information of an RFID tag in a non-contact manner using radio frequency, and more particularly, a reader between a tag and a reader. The present invention relates to a tag recognition method of a radio frequency identification system capable of improving the performance of an RFID system by measuring a channel environment and selecting an encoding method between an FM0 encoding and a Miller encoding according to the measured channel environment.

In general, Radio Frequency IDentification (RFID) inputs identification information unique to the smallest IC chip, and can recognize, track, and manage an object or animal to which the chip is attached using radio frequency (RF). Says technology. Such an RFID system is composed of an RFID tag (Tag or Transponder) to which unique identification information is input and attached to an object or animal, and a reader (Reader or Interrogator) to read or write the identification information of the tag without contact. An information processing apparatus such as a computer is connected to the reader to process data collected from a tag.

1 is a block diagram showing the basic configuration of an RFID system according to the prior art. The RFID system consists of a reader 10 and a tag 20. As shown, the tag 20 is a passive tag which does not have a power supply by itself, and is composed of a small semiconductor IC chip and an antenna, and the IC chip has RF circuits, logic, and memory embedded therein. These tags 20 have various sizes and shapes. And the reader 10 is configured to include a transmitter for transmitting the RF signal of a specific frequency band to the tag 20, a receiver for receiving a signal from the tag 20 and an antenna for transmitting and receiving it.

2 is a block diagram showing the basic operation of the RFID system according to the prior art. As shown, the reader 10 transmits an RF signal of a predetermined frequency band including a high frequency carrier signal and a predetermined question signal. When the tag 20 is located in the electromagnetic field of the reader 10 formed by the RF signal, the tag 20 receives operating power required to operate the IC chip from the high frequency carrier signal of the reader 10. That is, the high frequency carrier signal transmitted from the reader 10 generates alternating current to the antenna of the tag, and the generated alternating current is rectified and used as electrical energy for the IC chip. In addition, the tag 20 modulates the received RF signal and reflects the data stored in the tag 20 based on the received RF signal and transmits the received RF signal to the reader 10 as a response signal. As described above, the conventional RFID system performs power transmission for activating a passive tag as well as information transmission between the reader 10 and the tag 20.

3 is a block diagram showing in more detail the structure of the reader 10 that can be applied to the RFID system according to the present invention shown in FIG.

Referring to FIG. 3, when data is transmitted to the tag 20, the data output from the digital processor 30 is mixed with a predetermined carrier output from the frequency synthesizer 50 by the transmitter 40, and then a predetermined level. By amplifying and transmitting to the tag 20 through the coupler 60 and the RF antenna 70.

When receiving data from the tag 20, the receiver 80 receives a predetermined signal output from the frequency synthesizer 50 in response to the response signal of the tag 20 received through the RF antenna 70 and the coupler 60. The demodulated signal is generated by mixing with the carrier and then output to the digital processor 30.

When the tag is transmitted to the reader, the tag performs encoding according to the encoding method specified by the reader. The encoding methods are FM0 encoding and Miller encoding. Miller encoding is also called Delay Modulation.

4A is a diagram for explaining a basic function of FMO encoding, which is one of encoding methods when a tag transmits. In FM0 encoding, the phase is inverted at each symbol boundary, and in the case of symbol '0', there is another phase inversion in the middle of the symbol. 4B is a diagram illustrating FM0 symbols and sequences.

5 is a diagram illustrating a basic function of Miller encoding, which is one of encoding methods when a tag transmits. In Miller encoding, the phase is inverted between two '0' symbols, and there is also a phase inversion in the middle of the symbol '1'.

In the case of Miller encoding, it may have several subcarriers per bit. 6 is a diagram illustrating a subcarrier sequence of Miller encoding. Where M represents the number of subcarrier cycles.

In general, FM0 can achieve higher throughput (data rate) compared to Miller subcarriers of the same link frequency, and Miller subcarriers have the advantage of securing a relatively wide guard band. It is estimated to be.

Conventionally, a reader can select and use a tag encoding method or a user can select it through a user interface, but in this case, it is difficult to cope with changes in the dynamic channel environment between the tag and the reader.

The present invention has been made to solve the problems of the RFID system according to the prior art, the main object of the present invention is to measure the channel environment between the reader and the tag, the tag encoding method according to the measured channel environment By selecting between the FM0 encoding and the Miller encoding to provide a communication method of a radio frequency identification system that can improve the performance of the RFID system.

Tag recognition method of a radio frequency identification (RFID) system according to the present invention is a tag recognition method of a radio frequency identification (RFID) system consisting of a tag and a reader, the reader measures the channel environment between the tag and the reader, And selecting one of FM0 encoding and Miller encoding as the encoding method of the tag according to the measured channel environment.

The reader may measure the channel environment between the tag and the reader by using the strength of the received signal received from the tag.

In addition, the reader may measure the channel environment between the tag and the reader using the bit error rate of the received signal received from the tag.

One of 2, 4, and 8 may be selected as the value of the subcarrier according to the measured channel environment.

The encoding method selection step includes: (a) setting an encoding scheme table corresponding to a range of channel environment measurement values; (b) receiving a response signal sent from the tag; (c) measuring a channel environment between a tag and a reader from a response signal sent from the tag; (d) setting a new encoding method corresponding to the measured channel environment measurement value when the measured channel environment measurement value is out of the existing encoding method range; And (e) transmitting the set encoding scheme information to the tag when a new encoding scheme is set.

Step (c) preferably includes the step of measuring the channel environment between the tag and the reader by turning off the Tx signal and measuring the strength of the received signal in the channel.

Hereinafter, with reference to the accompanying drawings an embodiment of the present invention will be described in detail.

7 is a flowchart illustrating a communication method of a radio frequency identification (RFID) system according to an embodiment of the present invention.

Referring to FIG. 7, an encoding scheme table EMT corresponding to a range of channel environment measurement values is set (S200).

In the case of the ISO 18000-6 type C (EPC C1 Gen-2) standard, FM0 encoding and Miller encoding may be used as the encoding method of the tag 20, and Miller encoding is used as the encoding method of the tag 20. It may have a subcarrier of 2, 4, 8. The M value is used to indicate the number of subcarrier cycles, and when M is 1, it corresponds to FM0 encoding.

The encoding method is set to a predetermined initial value (S210). FM0 encoding (M = 1) may be set as an initial value.

A transmission message including the encoding scheme information of the tag 20 is transmitted to the tag 20 (S220). The tag 20 receiving the transmission message transmits a signal according to the encoding scheme set by the reader 10.

In step S230, a response signal transmitted from the tag 20 is received. Decode the response signal from the tag according to the set tag encoding scheme.

The channel environment between the tag and the reader is measured from the response signal transmitted from the tag 20 (S240). The reader 10 may measure a channel environment between the tag and the reader by using the strength of the received signal received from the tag 20. In addition, the reader 10 may measure the channel environment between the tag and the reader by using the bit error rate or the symbol error rate of the received signal received from the tag 20. In another embodiment, the channel environment between the tag and the reader may be measured by turning off the Tx signal and measuring the strength of the received signal on the channel.

The EMT table is searched to determine whether the measured channel environment measurement value is within the range of the existing encoding scheme (S250).

If the channel environment measurement value is within the range of the existing encoding method, the existing encoding method is maintained (S260).

If the channel environment measurement value is out of the range of the existing encoding method, the EMT table is searched to set a new encoding method corresponding to the measured channel environment measurement value (S270). If the channel environment is best, you can use FM = 1 encoding with M = 1, and as the channel environment gets worse, you can use M = 2 Miller encoding, M = 4 Miller encoding, and M = 8 Miller encoding.

The better the channel environment, the higher the FM0 encoding with M = 1, and the worse the channel environment, the higher the Miller encoding with M = 2, the Miller encoding with M = 4, and the Miller encoding with M = 8. Therefore, if the optimal encoding scheme is variably set corresponding to the measured channel environment measurement value, the best performance can be obtained.

When the new encoding scheme is set, a transmission message including the set new encoding scheme information is transmitted to the tag 20 (S280). After the transmission of the transmission message, the decoding method of the receiving device of the reader 10 is also changed to a new method.

As described above, in the communication method of the radio frequency identification system according to the present invention, a reader measures a channel environment between a tag and a reader, and selects an encoding method of a tag between FM0 encoding and Miller encoding according to the measured channel environment. It can improve the performance of RFID system.

In addition, a preferred embodiment of the present invention is for the purpose of illustration, those skilled in the art will be able to various modifications, changes, replacements and additions through the spirit and scope of the appended claims, such modifications and changes are the following claims It should be seen as belonging to a range.

Claims (6)

In a tag recognition method of a radio frequency identification (RFID) system consisting of a tag and a reader, And measuring, by the reader, a channel environment between the tag and the reader, and selecting one of FM0 encoding and Miller encoding according to the measured channel environment. ) How to recognize tags in your system. The method of claim 1, The reader measures the channel environment between the tag and the reader using the strength of the received signal received from the tag tag recognition method of a radio frequency identification (RFID) system. The method of claim 1, And the reader measures a channel environment between a tag and a reader using the bit error rate of the received signal received from the tag. The method of claim 1, wherein one of 2, 4, and 8 is selected as a value of the subcarrier according to the measured channel environment. The method of claim 1, The encoding method selection step, (a) setting an encoding scheme table corresponding to a range of channel environment measurement values; (b) receiving a response signal sent from the tag; (c) measuring a channel environment between a tag and a reader from a response signal sent from the tag; (d) setting a new encoding method corresponding to the measured channel environment measurement value when the measured channel environment measurement value is out of the existing encoding method range; And (e) transmitting the set encoding method information to the tag when a new encoding method is set; Tag recognition method of a radio frequency identification (RFID) system comprising a. The method of claim 5, wherein Step (c) of the tag recognition method of the radio frequency identification (RFID) system comprising the step of measuring the channel environment between the tag and the reader by turning off the Tx signal and measuring the strength of the received signal on the channel .

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