Patent Application
20110148599
This application claims priority to and the benefit of Korean Patent Application No. 10-2009-0127669, filed Dec. 21, 2009, the disclosure of which is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a radio frequency identification (RFID) reader, an RFID tag, and a method of recognizing a plurality of RFID tags, and more particularly to an RFID system and method which controls a protocol and operation between an RFID reader and a plurality of RFID tags to easily recognize the RFID tags while reducing as much collision among the RFID tags as possible.
2. Discussion of Related Art
In general, RFID technology enables information to be read from or recorded in a tag having unique ID information using an RF without contact, so that an animal, person, etc. to which a tag is attached can be recognized, tracked, and managed. An RFID system includes a plurality of RFID tags (electronic tag or transponder; also referred to as tags below) and an RFID reader (interrogator; also referred to as a reader below) for reading or writing information that the tags have.
When the reader sends a command to all the tags in the RFID system according to conventional art, all the tags select random slots and respond to the command according to RFID tag recognition technology. At this time, collisions occur when many tags select the same slot, and backscattering of all the tags interferes with adjacent tags. As a result, tag recognition time increases, or the number of recognizable tags is limited.
The present invention is directed to a radio frequency identification (RFID) system and method that reduce collisions among responses of a plurality of tags using a tag grouping scheme and an inter-tag interference removing scheme in addition to a conventional general tag protocol, and thus can increase the number of recognizable tags to several times that of conventional art.
One aspect of the present invention provides an RFID reader of an RFID system including: a processor for processing a command for an RFID tag and a response from the RFID tag; a modem for modulating the command from the processor or demodulating the response from the RFID; an RF unit for transmitting the modulated command transferred from the modem to the RFID tag, or receiving the response from the RFID tag and transferring the response to the modem; and a memory for storing a tag ID of the RFID tag read by the processor and managing recognized tag IDs according to groups.
Another aspect of the present invention provides an RFID tag of an RFID system including: a power supply unit for generating energy using a radio wave received from an RFID reader; a receiver for demodulating a signal received from the RFID reader; a data processor for performing operation according to the signal demodulated by the receiver; and a transmitter for backscattering a signal from the data processor. Here, the data processor of the RFID tag includes: a protocol processor for performing operation according to a command of the RFID reader; a transmission controller for controlling a backscattering function of the transmitter; and a group selector for selecting a group number of the RFID tag.
Still another aspect of the present invention provides a method of recognizing a plurality of RFID tags in an RFID system including: transmitting, at an RFID reader, a group_select command to at least one of the RFID tags; selecting, at the RFID tag, a group number of the RFID tag on the basis of the group_select command; transmitting, at the RFID reader, a wake_group command including an argument specifying a group number to the RFID tag; determining, at the RFID tag, whether or not the group number specified by the wake_group command and the group number of the RFID tag are identical; and disabling a backscattering function of the RFID tag when the specified group number and the group number of the RFID tag are not identical, and enabling the backscattering function of the RFID tag when the specified group number and the group number of the RFID tag are identical.
The above and other objects, features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which:
Hereinafter, exemplary embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments disclosed below but can be implemented in various forms. The following embodiments are described in order to enable those of ordinary skill in the art to embody and practice the present invention. To clearly describe the present invention, parts not relating to the description are omitted from the drawings. Like numerals refer to like elements throughout the description of the drawings.
Throughout this specification, when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or electrically connected or coupled to the other element with yet another element interposed between them.
Throughout this specification, when an element is referred to as “comprises,” “includes,” or “has” a component, it does not preclude another component but may further include the other component unless the context clearly indicates otherwise. Also, as used herein, the terms “. . . unit,” “. . . device,” “. . . module,” etc., denote a unit of processing at least one function or operation, and may be implemented as hardware, software, or combination of hardware and software.
Referring to
An RFID system and method according to an exemplary embodiment of the present invention will be described in detail below with the appended drawings.
The RFID reader 301 includes a processor 302, a modem 303, an RF unit 304, and a memory 305. The processor 302 processes a command for the RFID tag 306, which is within a predetermined range of the RFID reader 301, and a response from the RFID tag 306. The modem 303 modulates the command from the processor 302 and transfers the modulated command to the RF unit 304, or demodulates a signal received from the RF unit 304 and transfers the demodulated signal to the processor 302. In an exemplary embodiment of the present invention, the modem 303 may include an encoder/decoder (not shown) to encode/decode a signal. The RF unit 304 receives the signal obtained by modulating the command of the processor 302 from the modem and transmits the signal to the outside, or receives an external signal from the RFID tag and transfers the received external signal to the modem 303. The memory 305 stores a tag ID read by the processor 302 and manages recognized tag IDs according to groups.
The RFID tag 306 includes a power supply unit 307, a receiver 308, a transmitter 309, a data processor 310, and a memory 311. The power supply unit 307 receives a radio wave from the RFID reader 301 through an antenna, generates and keeps a direct current (DC) voltage at a fixed level, and supplies power to the components of the RFID tag 306. The receiver 308 demodulates a signal received from the RFID reader 301 through the antenna and transfers the demodulated signal to the data processor 310. The receiver 308 may include a decoder and decode the signal received through the antenna. The data processor 310 includes a protocol processor 310-1 processing data according to a command (e.g., a search command, a read/record command, and a wake_group command) transmitted from the RFID reader 301, a transmission controller 310-2 controlling the backscattering function of the transmitter 309, and a group selector 310-3 selecting a group number according to a command (e.g., a group_select command) transmitted from the RFID reader 301. In an exemplary embodiment of the present invention, the group number may be a random integer. The transmitter 309 backscatters response data processed by the data processor 310. The transmitter 309 includes a blocker 309-1 controlling the backscattering operation of the transmitter 309, and the blocker 309-1 is configured to operate according to a control of the transmission controller 310-2. In an exemplary embodiment, the blocker 309-1 may cut off the power supply connection of the transmitter 309, the antenna connection, or both of the power supply connection and the antenna connection. The memory 311 stores data processed by the data processor 310, and may be a non-volatile memory in an exemplary embodiment of the present invention.
In the group select section, a reader transmits a “group_select(number)” command (also referred to as a “group_select command”) to tags within a predetermined range. Here, the number can denote the maximum number of tag groups, and tags randomly select a group number within the maximum number of tag groups. For example, when the reader transmits a “group_select(3)” command, there can be 3 tag groups(e.g. a group 1, a group 2, and a group 3), and tags can select one of the group 1 to 3. Furthermore, when the reader transmits a “group_select(0)” command, all the tags can select a group 0, and only one group is formed. The following operation conforms to the conventional inventory round rule of EPC C1 Gen2. In an exemplary embodiment of the present invention, the default group of tags is 0. The tags belonging to the group 0 can operate according to the conventional EPC C 1 Gen2 standard, and thus is compatible with conventional technology.
When the reader transmits a “group_select(15)” command in the example shown in
In the inventory round section, the reader transmits a “wake_group(number)” command (also referred to as a “wake_group command”) to select a specific tag group. Here, the number denotes a group number which is equal to or smaller than the maximum number indicated by the group_select command. Every time the reader transmits the wake_group command, the number may increase from 1, or the number may be randomly selected. A tag receiving the wake_group command from the reader determines whether the group number indicated by the wake_group command is identical to a group number selected by the tag itself. When the selected group number is identical to the group number indicated by the wake_group command, the tag is placed into a state in which it is possible to use the backscattering function of the transmitter of the tag and thus can communicate with the reader according to the inventory round rule. On the other hand, when the selected group number is not identical to the group number indicated by the wake_group command, the tag disables the backscattering function of the transmitter and keeps the backscattering function disabled until a wake_group command indicating the same group number as selected by the tag itself is received. When a wake_group command indicating the same group number as selected by the tag itself is received, the tag enables the backscattering function and can communicate with the reader according to the inventory round rule. The reader transmits wake_group commands to all groups corresponding to the number indicated by the group_select command and performs the inventory round process, thereby storing tag IDs according to the groups.
In the group access section, the reader may access a specific tag on the basis of the stored tag IDs. When the reader transmits a wake_group command to select a group to which the specific tag belongs, the backscattering function of tags belonging to groups other than a group having a group number indicated by the wake_group command is disabled, and an access operation to the specific tag belonging to the group enabled to use the backscattering function can be performed according to conventional art.
In an exemplary embodiment of the present invention, it is possible to select a specific group using a wake_group command and command tags belonging to the selected group to select a group again. In
When a group_select command is received from the reader, the tag selects and stores its group number. As described above, when a group_select command is received again from the reader, the tag may reselect its group number on the basis of, for example, an argument for a group number indicated by the reader in the group_select command according to the received group_select command. After this, when a wake_group command is received from the reader, the tag compares the group number selected by the tag itself with a group number specified by the wake_group command. When the selected group number differs from the specified group number, the tag disables the backscattering function of the transmitter, and waits until another wake_group command is received. On the other hand, when the selected group number is identical to the specified group number, the tag enables the backscattering function of the transmitter. Thus, the tag can communicate with the reader according to the conventional inventory round rule. Also, the tag performs an access process together with the reader and waits until a wake_group command is received again from the reader. After a wake_group command is received, the tag may receive a group_select command again, or reselect its group number on the basis of the group_select command.
The RFID reader 301 transmits a group_select command to a plurality of RFID tags (step 801). The group_select command includes an argument indicating the maximum number of groups or the range of groups.
Each RFID tag receiving the group_select command selects a group number (step 802). The group selector 310-3 of the RFID tag 306 randomly selects a group number on the basis of the argument indicated by the group_select command and stores the selected group number. In an exemplary embodiment of the present invention, the group selector 310-3 may select a group number using a random number generator (not shown), and the selected group number may be stored in the memory 311.
The reader 301 transmits a wake_group command to the RFID tags (step 803). The wake_group command includes an argument specifying a group number.
Each RFID tag receiving the wake_group command determines whether or not the group number specified by the wake_group command is identical to a group number selected by the RFID tag itself (step 804). The protocol processor 310-1 of the RFID tag 306 compares the group number stored in the memory 311 with the group number specified by the wake_group command received from the RFID reader 301.
When the group number specified by the wake_group command and the group number selected by the RFID tag 306 are identical, the backscattering function of the RFID tag 306 is enabled (step 810). The transmission controller 310-2 of the RFID tag 306 controls the blocker 309-1 of the transmitter 309 not to operate, thereby maintaining the backscattering function of the transmitter 309. Since the backscattering function of the RFID tag 306 is maintained, the RFID reader 301 and the RFID tag 306 can perform an inventory round process (step 811). Also, an access process to the RFID tag 306 may be performed (step 812).
Meanwhile, when the group number specified by the wake_group command and the group number selected by the RFID tag 306 are not identical to each other, the backscattering function of the RFID tag 306 is disabled (step 820). The transmission controller 310-2 of the RFID tag 306 controls the blocker 309-1 of the transmitter 309 to operate, thereby disabling the backscattering function of the transmitter 309. The blocker 309-1 may be implemented by a switch. The switch may be switched to a connection state or a disconnection state according to a control signal of the transmission controller 310-2, thereby cutting off the power supply of the transmitter 309 or a connection between the transmitter 309 and the antenna. The RFID tag 306 whose backscattering function is disabled waits until a wake_group command is transmitted again, and the process returns to step 804 when a wake_group command is transmitted.
When a plurality of RFID tags piled up and overlapping each other receive a command from a reader, mutual coupling occurs between the tags due to antennas and the backscattering function and slightly interferes with a signal of neighboring tags. According to an exemplary embodiment of the present invention, the backscattering function of an RFID tag belonging to no group is completely disabled in advance, and thus the number of tags between which mutual coupling occurs is reduced. Consequently, interference between tags is reduced, and tag recognition performance is enhanced.
As described above, an RFID system and method according to an exemplary embodiment of the present invention can process several thousand tags or more as it would dozens of tags and thus can easily recognize a plurality of tags.
Also, since the RFID system and method disable the backscattering function of tags belonging to a non-selected group, mutual coupling between tags is reduced, and a recognition rate can be increased even if tags overlap each other. In particular, when a high frequency (HF) Gen2 protocol, such as International Organization for Standardization (ISO)/International Electrotechnical Commission (IEC) 18000-3 mode 3, is applied to the RFID system and method, it is possible to exceptionally improve the multiple tag recognition performance of an HF tag in comparison with other technology.
While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2009-0127669 | Dec 2009 | KR | national |
