Method for processing command by tag in radio frequency identification system and tag thereof

Technical field

The present invention relates to the technical field of radio frequency identification (RFID) and, particularly, to a method for processing by a tag a command from a reader in an RFID system and a tag for implementing the method.

Background art

In recent years, RFID technology has gained more and more attention. Since hundreds of targets can be identified instantly by way of RFID technology, RFID technology can be applied in a variety of situations such as logistics and production sites. However, no matter in which application situation it is used, its processing efficiency is always one of the important criteria for evaluating the system performance of an RFID system.

According to the provisions of the protocol "EPC Radio- Frequency Identity Protocols Class-1 Generation-2 UHF RFID Protocol for Communications at 860MHz-960MHz Version 1.0.9" established by the worldwide EPC organization, EPC global, in an RFID system, when the distance between a tag and a reader is within the reading range of the reader, the reader will initiate a process to identify the tag. After the reader has successfully completed the identification of the tag, the tag will enter an Open or a Secure state, then the reader may send a command to the tag in the Open/Secure state, instructing the tag to perform a corresponding operation. For example, the reader can send a Write command, a Kill command, a Lock command, a BlockWrite command or a BlockErase command to the tag in the Open/Secure state, to instruct the tag to perform a corresponding Write, Kill, Lock, BlockWrite or BlockErase operation. Accordingly, after the tag in the Open/Secure state has received the command from the reader, the tag will first carry out a cyclic redundancy check (CRC) on the received command, and, if the CRC check is successful, then it performs the operation corresponding to the received command and feeds back to the reader a response to inform the reader of the processing result of the received command; otherwise, if the check is failed, the tag discards the received command, and then continues waiting for a new command from the reader. At the same time, the reader, after having sent a command, will further send a continuous-wave (CW) to the tag in the Open/Secure state, so as to provide the tag with the energy required for performing the corresponding operation, and at the same time wait for the response from the tag. According to the provisions of the protocol, the longest time period for the reader to wait for the response from the tag is 20 milliseconds (ms) , that is, if the reader receives a response from the tag within 20 ms after sending a command, it will stop sending the CW after having received the response from the tag; otherwise, if no response from the tag is received within 20 ms after sending the command, it will immediately stop sending the CW. After having stopped sending the CW, the reader can go on to send a new command to the tag in the Open/Secure state. For ease of description, the time period from the moment when the reader sends out a command to the moment when the reader receives a response from the tag can be referred to as the tag's response time T _REPLY . It can be found by statistics that, if both the reader and the tag operate at the highest transmission rate, T _REPLY is approximately 2.8 ms, which is far less than 20 ms; while even if the reader and the tag both have the lowest transmission rate, T _REPLY is approximately 18 ms, which is still less than 20 ms .

It can be seen from the above-described execution process that, if the tag in the Open/Secure state fails in the CRC check of the received command, the tag will discard the received command without feeding back any response to the reader. Therefore, in this case the reader needs to send the CW continuously for 20 ms, that is to say, in this case the reader has to wait for at least 20 ms before it can send a new command to the tag. Since in normal circumstances the response time of a tag is far less than 20 ms, it leads to an excessively long waiting time period for the reader in the case that the CRC check of the command sent from the reader to the tag fails, and this significantly affects the processing efficiency of the RFID system.

The object of the invention is to solve the above-mentioned problem. The embodiments of the present invention provide a method for processing a command by a tag and a tag for implementing the method, so as to improve the processing efficiency and performance of the whole RFID system.

The method for processing a command by a tag described in the embodiments of the present invention comprises:

receiving a command from a reader and carrying out a cyclic redundancy check on the received command;

if the received command passes the cyclic redundancy check, performing an operation corresponding to the received command and feeding back a response to the reader; otherwise, discarding the received command and feeding back to the reader a response about the failure of the cyclic redundancy check.

In this case, the above-mentioned command is a command for revising data or a flag in the tag, comprising a write command, a kill command, a lock command, a BlockWrite command and a BlockErase command.

The above-mentioned command further comprises predefining a response to the failure of the cyclic redundancy check.

Alternatively, the above-mentioned command further comprises: predefining an error code for identifying the failure of the cyclic redundancy check; in this case said feeding back to the reader the response about the failure of the cyclic redundancy check comprises: generating the error code for identifying the failure of the cyclic redundancy check; and feeding back a tag error response carrying the generated error code to the reader.

The tag as described in the embodiments of the present invention comprises:

a command receiving unit for receiving a command from a reader;

a cyclic redundancy checking unit for carrying out the cyclic redundancy check on the received command;

a command performing and responding unit, for performing an operation corresponding to the received command and feeding back to the reader a response in the case that the cyclic redundancy check on the received command is passed; and

a cyclic redundancy check failure responding unit, for discarding the received command and feeding back to the reader a response about the failure of the cyclic redundancy check in the case that the cyclic redundancy check on the received command fails.

In this case, said cyclic redundancy check failure responding unit comprises:

an error code generating module, for generating an error code for identifying the failure of the cyclic redundancy check; and

a tag error responding module, for feeding back to the reader a tag error response carrying the generated error code.

By way of the method and the tag in the embodiments of the present invention, even in the case that a CRC check on the command sent from the reader to the tag fails, the reader can still receive a response from the tag about the failure of the cyclic redundancy check within 20 ms of sending the command, the reader can thereby detect the failure of the cyclic redundancy check on the command to the tag as early as possible, stop sending a continuous wave (CW) in advance and send a new command to the tag in advance without having to wait for a time period as long as 20 ms, thus improving the processing efficiency and the performance of the whole RFID system.

Brief description of the accompanying drawings

Fig. 1 is a flowchart of the method for processing a command by a tag according to the embodiments of the present invention; and

Fig. 2 is an internal structural diagram of the tag described in the embodiments of the present invention.

Exemplary embodiments

In order to make the objects, technical solutions and advantages of the present invention more clear, the present invention will be described in detail hereinbelow in conjunction with the accompanying drawings and particular embodiments .

The embodiments of the present invention provide a method for processing a command from a reader by a tag. In the embodiments, the tag is a tag in an Open/Secure state. The implementation process of the method for processing by the tag a command from the reader according to the embodiments of the present invention is shown in Fig.l, which mainly comprises:

Step 101: receiving a command from a reader, and carrying out a CRC check on the received command.

In this embodiment, said command from the reader can be a command for revising the data or a flag in the tag, such as Write, Kill, Lock, BlockWrite or BlockErase and so on.

Step 102: if the CRC check on the received command is passed, perform step 103; otherwise perform step 104. Step 103: perform an operation corresponding to the received command and feed back a response to the reader.

According to the provisions of the RFID protocol, after successfully performing the operation corresponding to the received command, a tag will feed back a response to the reader to inform the reader of the success in performing the operation. Even if the operation corresponding to the received command is not performed successfully, the tag will still feed back to the reader a tag-error reply carrying an error code, informing the reader the reasons for the failure.

Step 104: discard the received command, and feed back to the reader a response about the failure of the cyclic redundancy check.

In this step, a new message can be predefined between the reader and the tag as said response about the failure of the cyclic redundancy check. The newly defined message can adopt any user-defined format.

Of course, in order to minimize changes the existing RFID systems as much as possible, said response about the failure of the cyclic redundancy check fed-back from the tag to the reader can adopt the format of a tag-error reply provided in the existing RFID protocol, that is, it can include a 1-bit header, an 8-bit error code, a 16-bit RN and a 16-bit CRC-16 check code. Then in this step, when the received command is discarded, it will further generate an error code for identifying the failure of the cyclic redundancy check, and feed back to the reader the tag-error response carrying the generated error code. At the moment, there are 5 error codes already defined in the RFID protocol, which are respectively: 00000000 , 00000011 , 00000100 , 00001011 and 00001111. Therefore, in this embodiment, the tag and the reader need to predefine an error code for identifying the failure of the cyclic redundancy check, and the predefined error code for identifying the failure of the cyclic redundancy check should be different from the error codes already defined in the existing RFID protocol, for example, any 8 bits other than the above mentioned 5 error codes, such as 11111111, can be chosen as the error code for identifying the CRC check error. Or alternatively, the tag can carry any error code in said response about the failure of the cyclic redundancy check without having to consider whether the reader can identify the error code, as long as the purpose of informing the reader to stop sending the CW and terminate waiting for response can be achieved.

In this way, even in the case that the CRC check on the command sent from the reader to the tag fails, the reader can still receive from the tag a response about the failure of the cyclic redundancy check within 20 ms of sending the command. Therefore, by using the method as described in this embodiment, the reader can detect the failure of a CRC check on the command to the tag as early as possible, stop sending the continuous wave (CW) in advance and send a new command to the tag in advance without having to wait for a time period as long as 20 ms, thus improving the processing efficiency and the performance of the whole RFID system.

In addition to the above-mentioned method for processing a command, the embodiment of the present invention also provides a tag for implementing the above-mentioned method. The internal structure of the tag described in the embodiment of the present invention is shown in Fig. 2, which mainly comprises:

a command receiving unit for receiving a command from a reader;

a cyclic redundancy checking unit for carrying out a cyclic redundancy check on the received command;

a command performing and responding unit, for performing an operation corresponding to the received command and feeding back a response to the reader in the case that the cyclic redundancy check on the received command is passed; and a cyclic redundancy check failure responding unit, for discarding the received command and feeding back to the reader a response about the failure of the cyclic redundancy check in the case that the cyclic redundancy check on the received command fails.

In this case, said cyclic redundancy check failure responding unit comprises:

an error code generating module, for generating an error code for identifying the failure of the cyclic redundancy check; and

a tag error responding module, for feeding back a tag error response carrying the generated error code to the reader.

It is found from statistics that the time period for a response about the failure of the cyclic redundancy check to transmit from the tag to the reader is far less than 20 ms, for example, if both the reader and the tag operate at the highest transmission rate, the time period for the response to transmit from the tag to the reader is merely approximately 0.1 ms, and even if both the reader and the tag have only the lowest transmission rate, the time period for the failure of the cyclic redundancy check response to transmit from the tag to the reader is still merely about 1.5 ms . Therefore, in the case that the CRC check on the command sent from the reader to the tag fails, the time spent by the reader in sending the CW can be reduced significantly, and the processing efficiency and performance of the RFID system can be improved substantially.

By way of example, assuming that the signalling from the reader to the tag adopts pulse-interval encoding (PIE) , the transmission rate of the tag is from 40 kbps to 640 kbps . It is found from statistics that, when the transmission rate of the tag is 640 kbps, by using the method described in the embodiments of the present invention, the time period for the RFID system to process a command which fails a cyclic redundancy check will be reduced to 15% of the original time period, and even if the transmission rate of the tag is merely 40 kbps, the processing time will still be reduced by half, therefore the processing efficiency of the RFID system is considerably improved.

What are described above are merely preferred embodiments of the present invention, they are not intended to limit the present invention, and all modifications, equivalent replacements, improvements and so on within the spirit and principle of the present invention should be covered in the protective scope of the present invention.