CN115545131A - Frequency division multiplexing RFID system communication identification method - Google Patents

Abstract

The invention discloses a communication identification method of a frequency division multiplexing RFID system, which comprises the following steps: step a, a reader sends a carrier signal to activate a label; step b, sending a command to the tag; step c, analyzing the received command by the label, if an FDMSELECT command is received, executing step d, if an FDMQuery command is received, executing step e, and if an FDMACK command is received, executing step f; d-f, respectively processing the three commands; step g, the reader-writer detects the data returned by the label and carries out collision detection; h, the upper computer detects that label collision exists in the received signal fed back by the reader-writer, then jumps to b, otherwise jumps to i; and step i, the reader completes communication with all the tags, the reader is powered off, and all the modules stop working. The frequency division multiplexing RFID system provided by the invention has the advantages of high identification efficiency and high data throughput rate, and can effectively reduce the probability of collision when a plurality of labels simultaneously respond to a reader-writer command, thereby further reducing the label missing identification rate.

Description

Communication identification method of frequency division multiplexing type RFID system

Technical Field

The invention belongs to the technical field of communication, and particularly relates to a frequency division multiplexing RFID system structure, a frequency division multiplexing communication protocol and a frequency division multiplexing RFID system communication identification method.

Background

With the development of science and technology, radio Frequency Identification (RFID) technology is regarded as one of the most promising information technologies in the new era due to its wide application prospects and technical characteristics. The RFID system has the advantages of low power consumption, long identification distance, high identification efficiency and the like, so that the RFID system is widely applied to the fields of logistics, access control, article management and the like.

The RFID system generally includes a base station, a terminal, and a background processing system (upper computer), where the base station generally refers to a reader/writer, and the terminal generally refers to a tag. The RFID system is a non-contact automatic identification system, which can automatically identify a target object by a radio frequency wireless signal and acquire related data. The upper computer can control the reader-writer to send various commands, the electronic tag can return self related data to the reader-writer after receiving the inventory command of the reader-writer, and then the reader-writer can transmit the received tag data to the upper computer for storage and management.

The traditional RFID (UHF RFID) system generally adopts a time division multiplexing technology, namely, a reader can only receive information of one label at the same time, otherwise, the labels collide with each other, and the identification efficiency and the throughput rate of the RFID system are greatly reduced. Therefore, reducing the probability of a collision being sent when tags respond to reader commands simultaneously would be expected to improve the recognition efficiency and throughput of the system.

Because the existing UHF RFID system has the defects, the existing UHF RFID system is not suitable for the application scene of simultaneously accessing massive terminals in the future large-scale Internet of things.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide the communication identification method of the frequency division multiplexing type RFID system, which has the advantages of high identification efficiency and high throughput rate and can effectively reduce the collision probability when a plurality of labels simultaneously respond to the commands of a reader.

The purpose of the invention is realized by the following technical scheme: the communication identification method of the frequency division multiplexing RFID system comprises the following steps:

step a, powering on a reader-writer, and then sending a carrier signal to activate a label in a coverage range;

b, the upper computer sends a command to the reader-writer, and then the reader-writer transmits the command to the tag; the commands include an FDMSelect command, an FDMQuery command and an FDMACK command;

step c, analyzing the received command by the label, judging whether the CRC-16 check of the command passes, if the command passes, executing the content of the command, if an FDMSelect command is received, executing the step d, if an FDMQuery command is received, executing the step e, and if an FDMACK command is received, executing the step f; otherwise, the label ignores the command and waits for the next command sent by the reader-writer;

d, if the label receives the FDMSelect command, the label in the coverage area of the reader-writer compares whether the corresponding bit of the ID of the label is matched with the mask information in the command, if so, the label is selected by the reader-writer, a channel is selected according to the channel distribution information in the command, and the FDMQuery command is waited for, otherwise, the command is ignored;

step e, if the tag receives the FDMQuery command, judging whether the FDMshelf command is received or not, if so, sending self-related data information in a selected channel by the tag, and after sending the data, waiting for the next command of the reader-writer by the tag; otherwise, ignoring the FDMQuery command;

step f, if the tag receives the FDMACK command, judging whether the FDMSelect command and the FDMQuery command are received or not, if so, comparing whether the ID of the tag which has sent the relevant data information of the tag is consistent with the ID information carried by the FDMACK command or not, if so, indicating that the tag is identified, entering an identification state, and not responding to the FDMSelect and the FDMQuery command of the reader-writer, otherwise, continuing to wait for the reader-writer command; if the tag has not received the FDMSelact command and/or the FDMQuery command, ignoring the FDMACK command;

step g, if the reader-writer sends an FDMQuery command, the reader-writer detects the returned data of the tag, when the reader-writer receives the data of the tag, the reader-writer analyzes the received signals in each channel, and if no signal exists in a certain channel, the reader-writer indicates that no tag returns the data in the channel; if a signal exists in a certain channel and no collision exists, the fact that only one tag returns data in the channel is indicated, the tag is identified by the reader-writer, and the reader-writer transmits the ID information of the tag which is successfully received to the upper computer; if the signal in a certain channel has collision, the reader-writer needs to send the FDMQuery command again to enable the collided label to return the relevant data information of the reader-writer;

h, if the upper computer detects that the received signal fed back by the reader-writer has label collision, the communication between the reader-writer and the label is not finished, the step b is skipped, otherwise, the step i is skipped;

and step i, the reader completes communication with all the tags, the reader is powered off, and all the modules stop working.

The invention has the beneficial effects that: the frequency division multiplexing RFID system framework provided by the invention has the advantages of high identification efficiency and high throughput rate, and can effectively reduce the probability of collision when a plurality of tags simultaneously respond to a reader-writer command, so that the system structure can provide reference for improving the identification efficiency and the throughput rate of a UHF RFID system. Moreover, the system can realize the function of simultaneously storing a plurality of labels by the reader-writer, and can overcome the defect that the battery of the active label needs to be frequently replaced by adopting the passive label. Meanwhile, in the system, if the number of M values selectable by the tags is more, namely the number of channels for returning information selectable by the tags is more, the probability of collision between the tags is smaller, so that the frequency division multiplexing RFID system can be suitable for application scenes requiring simultaneous access of massive terminals in a large-scale Internet of things. The frequency division multiplexing method provided by the invention is mainly based on M value selection channel, which is a baseband signal processing method, and the tag responds data through ASK, is irrelevant to the specific system working frequency, and can be suitable for systems with different frequencies only by performing corresponding processing on different frequencies during circuit design, so that the frequency division multiplexing type RFID system communication identification method provided by the invention is suitable for processing and realizing communication identification signals of the frequency division multiplexing type RFID system with frequency bands of low frequency, high frequency, microwave and the like.

Drawings

FIG. 1 is a block diagram of a frequency division multiplexed RFID communication system of the present invention;

FIG. 2 is a communication flow diagram for the case where tag information is unknown according to the present invention;

FIG. 3 is a communication flow diagram of the present invention with known tag information;

fig. 4 is a timing diagram of the operation of the uhf RIFD system of the present invention.

Detailed Description

The technical scheme of the invention is further explained by combining the attached drawings.

The structure of the frequency division multiplexing RFID communication system of the present invention is shown in fig. 1, and the architecture of the system is as follows: the label-based wireless communication system comprises an upper computer, a reader-writer and a plurality of labels (four label modules are used in the figure, namely a first label Tag1, a second label Tag2, a third label Tag3 and a fourth label Tag 4), wherein arrows pointing to the reader-writer of the labels are respectively a channel 1-a channel 4 from left to right. All tags may select a channel to transmit data, and all tags may select the same channel to transmit data at the same time.

Each command received by the tag to the reader requires CRC-16 verification, and if the verification fails, the tag ignores the command. Meanwhile, the reader-writer also performs CRC-16 verification after receiving the tag data, and if the verification fails, the reader-writer sends a command to enable the tag to send self information again.

The FDMSelect command mainly selects a tag to be communicated with the reader and sends channel related information of return data to the tag, and can be divided into FDMSelect-1 and FDMSelect-2 commands according to the way in which the reader selects the tag. The FDMSelect-1 command may cause the tags to randomly select channels to return data based on the initial M value and the initial BLF, and the FDMSelect-2 command specifies by masking certain tags to return data on a particular channel. And after receiving the label analysis command of the FDMSselect command, storing the channel information, but not returning the information. The FDMQuery command is mainly used for storing the selected tags, the tags randomly select a time slot number according to the Q value in the FDMQuery command, and when the time slot number becomes zero, the tags select channels according to the stored channel information to send own data. The FDMACK command is mainly used to make the tag that has successfully received the information by the reader enter an identification state, and temporarily disregard the inventory command. Communication between the reader and the tag can be performed in two cases: communication when tag information is unknown and communication when tag information is known. Wherein the communication for which the tag information is unknown corresponds to having the tag randomly select a channel to return data using the FDMSelect-1 command and the communication for which the tag information is known corresponds to having the tag specify to return data on a particular channel using the FDMSelect-2 command.

In the above frequency division multiplexing UHF RFID system, the frequency division multiplexing communication protocol mainly includes three frequency division multiplexing communication commands, namely, an fdmselect command, an fdmqquery command, and an FDMACK command. The functional contents of the frequency division multiplexing communication protocol are shown in table 1.

TABLE 1

Example 1

If the reader wants the tag to randomly select a channel to send its own related data information, the general reader does not know any information of the tag, as shown in fig. 2, the communication identification method of the frequency division multiplexing RFID system includes the following steps:

step a, powering on a reader-writer, and then sending a carrier signal to activate a label in a coverage range;

b, the upper computer sends a command to the reader-writer, then the reader-writer transmits the command to the label, and at the moment, the reader-writer does not carry out channel allocation on the label; the commands include an FDMSelect command, an FDMQuery command and an FDMACK command;

step c, analyzing the received command by the label, judging whether the CRC-16 check of the command passes, if the command passes, executing the content of the command, if an FDMSelect command is received, executing the step d, if an FDMQuery command is received, executing the step e, and if an FDMACK command is received, executing the step f; otherwise, the label ignores the command and waits for the next command sent by the reader-writer;

step d, if the label receives an FDMSelct command (the command contains mask information for selecting the label and channel related information such as an initial M value, an initial backscattering frequency BLF and the like), the label in the coverage range of the reader-writer compares whether corresponding bits of the ID of the label are matched with the mask information in the command, if the corresponding bits are matched, the label is selected by the reader-writer, a channel is selected according to channel distribution information in the command (the channel is selected by the method that a random number of 1-8 is generated, then a channel for sending data is selected according to the random number, the initial M value and the initial backscattering frequency BLF), and an FDMQuery command is waited, otherwise, the command is ignored;

step e, if the tag receives the FDMQuery command, judging whether the FDMshelf command is received or not, if so, sending self-related data information such as ID, CRC and the like in a selected channel by the tag, and after the data is sent, waiting for the next command of the reader-writer by the tag; otherwise, ignoring the FDMQuery command;

step f, if the tag receives an FDMACK command (carrying ID information of the identified tag), judging whether the FDMSelect command and the FDMQuery command are received or not, if so, comparing whether the ID of the tag which has sent the self-related data information is consistent with the ID information carried by the FDMACK command or not, if so, indicating that the tag is identified and enters an identification state, and not responding to the FDMSselect and the FDMQuery command of the reader-writer any more, otherwise, continuing to wait for the reader-writer command; if the tag does not receive the FDMSelect command and/or the FDMQuery command, ignoring the FDMACK command;

step g, if the reader-writer sends an FDMQuery command, the reader-writer detects the returned data of the tag, when the reader-writer receives the data of the tag, the reader-writer analyzes the received signals in each channel, and if no signal exists in a certain channel, the reader-writer indicates that no tag returns the data in the channel; if a signal exists in a certain channel and no collision exists, the fact that only one tag returns data in the channel is indicated, the tag is identified by the reader-writer, and the reader-writer transmits the ID information of the tag successfully received to the upper computer; if the signal in a certain channel has collision, the reader-writer needs to send the FDMQuery command again to enable the collided label to return the relevant data information of the reader-writer;

h, if the upper computer detects that the received signal fed back by the reader-writer has label collision, the communication between the reader-writer and the label is not finished, the step b is skipped, otherwise, the step i is skipped;

and step i, the reader completes communication with all the tags, the reader is powered off, and all the modules stop working.

Example 2

If the reader-writer wants to designate some tags to send their own ID information in a designated channel, the reader-writer knows the relevant information of the tags at this time, as shown in fig. 3, the step of performing communication between the reader-writer and the tags includes:

step a, powering on a reader-writer, and then sending a carrier signal to activate a label in a coverage range;

b, the upper computer sends a command to the reader-writer, then the reader-writer transmits the command to the label, and the reader-writer performs channel allocation on the label before sending the command; the commands include an FDMSelect command, an FDMQuery command and an FDMACK command;

step c, analyzing the received command by the label, judging whether the CRC-16 check of the command passes, if the CRC-16 check of the command passes, executing the command content, if an FDMSelect command is received, executing the step d, if an FDMQuery command is received, executing the step e, and if an FDMACK command is received, executing the step f; otherwise, the label ignores the command and waits for the next command sent by the reader-writer;

step d, if the label receives an FDMSelelct command (the command contains mask information for selecting the label and channel related information such as an initial M value, an initial BLF and an appointed channel number), the label in the coverage range of the reader-writer compares whether the corresponding bit of the ID of the label is matched with the mask information in the command, if so, the label is selected by the reader-writer, a channel is selected according to channel distribution information in the command (the channel selection method is that a channel for sending data is selected according to the initial M value, the initial BLF and the appointed channel number), and the FDMQuery command is waited, otherwise, the command is ignored;

the treatment methods of the subsequent steps e to i are the same as those of e to i of example 1.

Because the FDMSelect command only contains partial mask information, the information of multiple tags may be matched with the partial mask in the command, so that the tags are all allocated to the same channel to transmit data, and collision occurs between the tags, so that the reader-writer cannot successfully receive the information of the tags. The collision detection of step g needs to be performed.

Fig. 4 is a timing diagram of the operation of the uhf RIFD system, after the reader sends an fdmqquery command, the first tag selects a channel of M =2, the second tag selects a channel of M =4, the third tag selects a channel of M =6, and the fourth tag selects a channel of M = 4. In the frequency division multiplexing UHF RFID system, the same M value in the same initial BLF indicates that the channels through which the tags transmit data are the same, so that the second tag and the fourth tag collide, which results in that the reader-writer cannot successfully receive the data information transmitted by the second tag and the fourth tag, i.e., the reader-writer is required to transmit an fdmqquery command to cause the second tag and the fourth tag to transmit its own data again. The channels selected by the first label and the third label are different from the channels of other labels, and the channels do not collide with other labels, so that the reader-writer can successfully receive the data information sent by the first label and the third label, and the two labels are identified.

It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.

Claims (1)

1. The communication identification method of the frequency division multiplexing RFID system is characterized by comprising the following steps:

step a, powering on a reader-writer, and then sending a carrier signal to activate a label in a coverage range;

step b, the upper computer sends a command to the reader-writer, and then the reader-writer transmits the command to the label; the commands include an FDMSelect command, an FDMQuery command and an FDMACK command;

step c, analyzing the received command by the label, judging whether the CRC-16 check of the command passes, if the CRC-16 check of the command passes, executing the command content, if an FDMSelect command is received, executing the step d, if an FDMQuery command is received, executing the step e, and if an FDMACK command is received, executing the step f; otherwise, the label ignores the command and waits for the next command sent by the reader-writer;

d, if the tag receives the FDMSelct command, the tag in the coverage of the reader-writer compares whether the corresponding bit of the ID of the tag is matched with the mask information in the command, if so, the tag is selected by the reader-writer, a channel is selected according to the channel distribution information in the command, and the FDMQuery command is waited for, otherwise, the command is ignored;

step e, if the tag receives the FDMQuery command, judging whether the FDMelelct command is received or not, if so, sending self-related data information in a selected channel by the tag, and waiting for the next command of the reader-writer after the data is sent; otherwise, ignoring the FDMQuery command;

step f, if the tag receives the FDMACK command, judging whether the FDMSELECT command and the FDMQuery command are received or not, if so, comparing whether the ID of the tag which sends the relevant data information of the tag is consistent with the ID information carried by the FDMACK command or not, if so, indicating that the tag is identified, entering an identification state, and not responding to the FDMSELECT and the FDMQuery command of the reader-writer any more, otherwise, continuing to wait for the reader-writer command; if the tag has not received the FDMSelact command and/or the FDMQuery command, ignoring the FDMACK command;

step g, if the reader-writer sends an FDMQuery command, the reader-writer detects the returned data of the tag, when the reader-writer receives the data of the tag, the reader-writer analyzes the received signals in each channel, and if no signal exists in a certain channel, the reader-writer indicates that no tag returns the data in the channel; if a signal exists in a certain channel and no collision exists, the fact that only one tag returns data in the channel is indicated, the tag is identified by the reader-writer, and the reader-writer transmits the ID information of the tag successfully received to the upper computer; if the signal in a certain channel has collision, the reader-writer needs to send the FDMQuery command again to enable the collided label to return the relevant data information of the reader-writer;

h, if the upper computer detects that the received signal fed back by the reader-writer has label collision, the communication between the reader-writer and the label is not finished, the step b is skipped, otherwise, the step j is skipped;

and step i, the reader completes communication with all the tags, the reader is powered off, and all the modules stop working.

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