WO2011009768A2

WO2011009768A2 - A method and reader for reading tag data a radio frequency identification system

Info

Publication number: WO2011009768A2
Application number: PCT/EP2010/060050
Authority: WO
Inventors: Xiao Dong Deng; Dieter Horst; Dan Yu; Yong Yuan
Original assignee: Siemens Aktiengesellschaft
Priority date: 2009-07-20
Filing date: 2010-07-13
Publication date: 2011-01-27
Also published as: CN101957923A; WO2011009768A3

Abstract

The present invention provides a method for reading data in the tags in the radio frequency identification (RFID) system, wherein said RFID system includes more than one reader and a group of tags, and each of said tags includes a group of data and a group of characteristic descriptions, wherein the method includes the steps of : first, the first reader or said tag encodes said characteristic descriptions using a code capable of error detection and error correction and writes said codes into said tag; secondly, said first reader or second reader reads said tag, receives said encoded characteristic descriptions, and decodes said characteristic descriptions according to said codes; finally, said first reader or second reader reads the corresponding data according to the decoded characteristic descriptions. By protecting the characteristic descriptions in a tag, the present invention effectively help readers to learn the characteristics of said tag and thus more accurately read the data stored in the tag.

Description

A method and reader for reading tag data a Radio Frequency

Identification system

Technical field

The present invention is directed to a Radio Frequency Identification (RFID) technology, and more particularly to a method for reading tag data in the Radio Frequency Identification system and readers for implementing the method.

Background technology

UHF wireless RFID technology is drawing more and more attention recently. Since UHF RFID is capable of identifying millions of unique objects per second, it creates a lot of application opportunities in logistics related fields. With quick development of new technologies such as near field UHF technology and battery assisted passive tags, UHF RFID is also considered a potential solution for manufacturing applications (e.g. operation of the pharmaceutical production lines) . Since UHF RFID complies with the globally recognized EPC C1G2 standard (EPC Radio-Frequency Identity Protocols Class-1 Generation-2 UHF RFID Protocol for Communications at 860MHz - 960MHz) and is unique in high-speed reading/writing, it can achieve better performances compared with the traditional HF band solutions in the manufacturing applications.

However, reliability of tag reading/writing is critical to continuous operation of the production lines in manufacturing applications. In these applications, the biggest challenge that UHF RFID faces is poor reliability of the reading/writing. For all read/write operations, the first step is to read the Electronic Product Code (EPC) in the EPC C1G2 standard. It can be said that the reliability of EPC reading will determine the reliability and speed of the whole reading/writing process. Usually, the EPC reading may fail in three circumstances: the reader has a time-out in reading the RN16 prefix, the reader has a time-out in reading the EPC data prefix and the reader has an error performing CRC check of the EPC data. As shown in Figure 1, the process of the EPC reading may be divided into two stages. First, the reader sends a Query command to the tag, and then the tag sends a 16-digit random number or a pseudorandom number (RNl 6) as a handle to the reader. Next, the reader sends an ACK command with a valid handle to the tag and the tag backscatters its EPC data after receiving the ACK command. In addition to the EPC codes, the EPC data includes the Protocol Control (PC) bits and Cyclic Redundancy Check (CRC) . In case of failure to capture the RN16 prefix or the EPC data prefix, RN16 time-out and EPC time-out will arise respectively. Also, an invalid handle as a result of tag conflicts may cause EPC time-out. Furthermore, since the reader uses CRC only for checking in EPC reading, some wrong bits in EPC transmission will cause CRC errors when the reader is doing CRC check, or even cause failure of EPC receiving.

Since the tag design is very simple, usually no complicated methods (for example, signal source and signal channel encoding) of communication is required for the tag in order to reduce the chance of occurrence of the above three circumstances. In the patent application of Siemens numbered 200810004983.0, "a method and device for supplying power to a passive tag in a radio frequency identification system" is provided, which preferably solves the first two failure circumstances. However, in many UHF RFID applications such as manufacturing applications, a great deal of interferences due to simple design of tags will make the reader unable to correctly receive EPC, causing CRC error of the reader when reading EPC data. For many applications with special requirements for reading/writing speed, the efficiency and reliability of receiving EPC data are very important. There are some solutions in the prior art for the problem of CRC error occurring in reading EPC data due to failure to correctly receive EPC by the reader. When receiving EPC data, for example, for some readers, such as ALR8800, once an error occurs when reading EPC data, the reader can resend an acknowledge command ACK to backscatter EPC data in case EPC data cannot pass the detection.

However, as shown in Figure 2, it is difficult for the reader to detect the end of transmission of tag backscattering due to a poor end of the message. The reader can only rely on the first byte of the PC in the EPC data to confirm the digit to be received in EPC receiving (EPC code included in two-byte PC data, or the length of EPC data) . Figure 3 shows the basic flow chart of obtaining EPC codes in the prior art by resending an acknowledgement command ACK.

First, the reader sends a Query command to the tag. When the tag receives the Query command, it returns a 16-digit random number RNl 6 as a handle to the reader. If the reader does not receive the random number RN16, it will resend the Query command after a certain period of time.

Second, when the reader receives the random number RNl6 sent by the tag, it sends an acknowledgement command ACK to the tag. When the tag receives the acknowledgement command ACK, it returns the prefix of the EPC. If the reader does not detect the prefix, it will resend the Query command after a certain period of time.

Further, when the reader receives the first byte of the PC, it obtains the length of the EPC (since the length of the PC and the length of the CRC are fixed, the length of EPC obtained represents the length of the whole EPC data) .

Then, the reader sets the data received by it at the length of the EPC plus 32 bits, and prepares to receive data.

After a certain period of waiting time, the reader will receive EPC data. Then the reader will carry out CRC against - A - the received data. If the check is successful, the reader will send the next query command QueryRep to the tag; if the check fails, the reader will resend an acknowledgement command ACK to the tag and detect the prefix of EPC data.

If the reader can correctly detect the PC, the process shown in Figure 3 can solve the problem of CRC error. However, if any errors occur in receiving PC, the reader will wrongly analyze the EPC length. Then a lot of time will be wasted in sending the next command, as shown in Figure 4. The upper picture in Figure 4 shows the original length of EPC data, and the lower picture in Figure 4 shows that the reader fails to correctly receive PC, so the length of EPC is wrongly determined. In the worst scenario, the time wasted may be as long as (496+32-8) *0.025=13ms, while normal EPC reading will take only around 2~3ms. On the other hand, due to time-out as a result of loss of synchronization, it will not respond to the next command. Therefore, wrongly receiving the PC will significantly affect the reliability and efficiency of the whole system.

The object of the present invention is to provide a type of method for reading the data in tags in a radio frequency identification system and a reader for implementing said method, which can protect the information of characteristic descriptions in reading the tag, so as to allow the reader to correctly detect and receive the characteristic descriptions and thus correctly obtain the data in the tag.

In order to realize the object described above, a method for reading the data in tags in a Radio Frequency Identification (RFID) system is provided, wherein said RFID system includes more than one reader and a group of tags, wherein each of said tags includes a group of data and a group of characteristic descriptions, and the method includes the following steps: (1) the first reader or said tag encodes the characteristic descriptions using a code capable of error detection and error correction and writes said codes into said tag;

(2) said first reader or second reader reads said tag, receives said encoded characteristic descriptions, and decodes the characteristic descriptions according to said code;

(3) said first reader or second reader reads the corresponding data according to the decoded characteristic descriptions .

As a preferred solution, in said Step (1), said code capable of error detection and error correction includes an Error Detection Code (EDC) and an Error Correction Code (ECC) .

According to an embodiment of the present invention, the data of said tag are the data in the data bank of the Electronic Product Code (EPC) , said characteristic descriptions of said tag are the Protocol Control (PC) , and the length of the EPC in said EPC data bank is recorded in the PC;

in said Step (1), said first reader encodes said PC using said EDC and said ECC, and writes the codes into said tag' s EPC data;

in said Step (2), said first reader or second reader reads the EPC data in said tag, receives said encoded PC, and decodes said encoded PC;

in said Step (3) , said first reader or second reader sets the data bits to be received according to the decoded PC and prepares to receive the data.

As a preferred solution of the present invention, said Step (1) includes the following steps:

(11) the length recorded by said PC is set to the sum of the lengths of said EPC, EDC, and ECC;

(12) a protection mark is set in the bit Reserved for Future Use (RFU) of said PC;

(13) said EDC is calculated for said PC;

(14) said ECC is calculated for said PC and said EDC; (15) said EDC and said ECC are stored in the initial position of said EPC.

As a preferred solution of the present invention, in said Step (2), the decoding of said encoded PC by said first reader or second reader further includes:

said first reader or second reader detects and corrects any error in said PC and said EDC through said ECC;

said first reader or second reader detects any error in said PC through said EDC to obtain the correct length of the EPC.

As a preferred solution of the present invention, if said EDC detects an error in said PC, said first reader or second reader will set the length of said EPC to be received to the length of the EPC of the previous tag. Or, if said EDC detects an error in said PC, said first reader or second reader will set the length of said received EPC to 96 bits. Or, if said EDC detects an error in said PC, said first reader or second reader will first wait for a period of time required for reading the longest EPC, and then initiate a new tag reading process, wherein the length of said longest EPC is 496 bits.

As a preferred solution of the present invention, in said Step (3) , said first reader or second reader sets the data bits to be received to the result of the length of said EPC plus 32 bits.

As a preferred solution of the present invention, if the length of said EPC changes, said first reader will rewrite said EDC and ECC into said electronic product code data.

As a preferred solution of the present invention, the following steps are included before said Step (1) : said first reader or second reader sends a protected tag selection command to the tags in its read/write area, to select the tags in said read/write area which have said protection marks set in the RFUs. In addition, after said Step (3), said first reader or second reader sends a normal tag selection command to the tags in its read/write area, to select the normal tags in its read/write area which do not have said protection marks set in the RFUs, and the data in the normal tags, which do not have said protection marks set, are read according to the normal reading process.

As a preferred solution of the present invention, before said Step (1), a register protection mode category mark is set in said first reader or second reader, and when said register is in the first protection mode, said Step (1) will continue.

As a preferred solution of the present invention, said first reader or second reader selects at least one period from the period of waiting to receive RN16 and the period of waiting to receive the EPC data as the enhanced period, and said reader adjusts the gain of signal transmission so that the carrier signal in the enhanced period will be sent with an enhanced sending power.

According to the second embodiment of the invention, the data of said tag includes the data in the EPC data bank and the data in the user memory bank, the characteristic description information of said tag are PC, and said PC identifies if there is valid data in said user memory bank.

In Step (1), said first reader encodes the PC by using said EDC and said ECC, and writes the codes into said tag' s EPC data;

In Step (2), said first reader or second reader reads the EPC data in said tag, receives said encoded PC, and decodes said encoded PC;

In Step (3) , said first reader or second reader decides based on the decoded PC whether or not to send the data reading command to read the data in the user memory bank. According to a preferred solution in the second embodiment of the present invention, said Step (1) includes the following steps :

(12) a protection mark is set in the RFU of said PC;

(13) said EDC is calculated for said PC;

(14) said ECC is calculated for said PC and said EDC;

(15) said EDC and ECC are stored in the initial position of said EPC.

According to the third embodiment of the present invention, the data of said tag includes the data in the EPC data bank and the data in the user memory bank, the characteristic description information of said tag is PC and Extended Protocol Control (XPC) , and said XPC identifies the recommissioning of said tag after it is killed;

in said step (1), said first reader encodes said PC and said XPC using said EDC and said ECC, and writes said codes into said tag;

in said Step (2), said first reader or second reader reads said tag, receives said encoded PC and XPC, and decodes said encoded PC and XPC;

in said Step (3) , said first reader or second reader decides on the recommissioning of the tag based on the decoded PC and XPC.

According to a preferred solution in the third embodiment of the present invention, in said step (1), encoding of said PC and said XPC by said first reader using said EDC and said ECC, and writing said codes into said tag include the steps of:

(11) the length recorded by the PC is set to the sum of the lengths of said EPC, EDC, and ECC;

(12) a protection mark is set in the RFU of said PC;

(13) said EDC is calculated for said PC;

(14) said ECC is calculated for said PC and EDC; (15) said EDC and said ECC are stored in said tag.

According to a preferred solution in the third embodiment of the present invention, in said Step (15), said EDC and ECC are stored in the initial position of said EPC. Or, in said Step (15), said EDC and said ECC are stored in said XPC.

The present invention also provide a method for reading the data in tags in the RFID system, wherein said RFID system includes more than one reader and a group of tags, each of said tags includes the data in the EPC data bank, said each EPC data includes the PC, EPC and Cyclic Redundancy Check (CRC) , characterized in that the method includes the following steps:

(1) an interface is defined between the reader and the host connected with said reader, and said host configures the length of said EPC to a fixed length through said interface;

(2) said reader stores the length of the EPC configured by said host in its register;

(3) when said reader reads the data in said tag, the length of said tag's EPC is obtained from the register of the reader;

(4) said reader sets the data bits to be received and prepares to receive the data.

According to a preferred solution of the present invention, in said Step (4), said first reader or second reader sets the data bits to be received to the length of said EPC plus 32 bits.

According to a preferred solution in another method, before said Step (1), a register protection mode category mark is set in said reader, and when the register is in the second protection mode, said Step (1) will continue.

According to a preferred embodiment in another method, said reader selects at least one period from the period of waiting to receive RN16 and the period of waiting to receive EPC data as the enhanced period, and said reader adjusts the gain of signal transmission so that the carrier signal in the enhanced period will be sent with an enhanced sending power.

Accordingly, the present invention provides a reader for reading the data in tags in the RFID system, characterized in that, said reader includes:

an encoding unit for encoding the characteristic descriptions using a code capable of error detection and error correction;

a writing unit for writing the code into a tag;

a reading unit for reading the data in said tag and receiving said encoded characteristic descriptions;

a decoding unit for decoding said characteristic descriptions using said code;

a receiving unit for reading the corresponding data according to the decoded characteristic descriptions.

As a preferred solution of the present invention, said writing unit further includes:

a setting unit for setting the length of the PC in said tag to the sum of lengths of the EPC, EDC and ECC, and setting a protection mark in the RFU of said PC;

a calculating unit for calculating said EDC for said PC and calculating said ECC for said PC and said EDC;

a storage unit for storing said EDC and said ECC into the beginning of said EPC.

As a preferred solution of the present invention, said reader further includes a command sending module for sending a protected tag selection command to the tags in its read/write area to select the tags in the read/write area which have said protection marks set in the RFU; or for sending a common tag selection command to the tags in its read/write area to select the tags in the read/write area which do not have said protection marks set in the RFU, and read the data in said common tags which do not have said protection marks set according to the common reading process.

In another method for reading data in tags in the radio frequency identification system, the present invention further proposes a reader wherein said reader includes:

an interface unit for defining an interface between the reader and the host connected with said reader so that said host configures the length of said EPC to a fixed length through said interface;

a storage unit for storing the length of the EPC configured by said host into the register of said reader;

a reading unit for acquiring the length of said tag' s EPC from the register of the reader when reading the data in said tag;

a receiving unit for setting the data bits to be received and preparing to receive the data.

The method and devices for reading data in tags in the radio frequency identification system according to the present invention have the following advantages:

First, by protecting the characteristic descriptions in a tag, the present invention effectively helps the reader to learn the characteristics of the tag and thus more accurately read the data stored in the tag. Using the method provided by the present invention, a reader can look up the correct EPC length before receiving the EPC. The reader will be well synchronized with the tag so that it does not have take time to wait for a response from the tag, thus improving the efficiency. On the other hand, thanks to the good synchronization, the reader can send the ACK command at the right time to request the EPC again, which will lead to greatly improved reliability.

Second, by supplying power to the tag, the reader can quickly increase the power to capture the T2R preamble. In combination with the method for supplying power to the tag as described above, the present invention can further improve the reliability without significantly interfering with other devices. Based on the above two advantages, the method according to the present invention is ideal for applications, e.g. manufacturing applications, where major interferences and multiple readers are present.

In addition, the implementation of the method according to the present invention only requires minor changes to the reader, and the method of the present invention is cost effective and can be implemented easily in tags and readers currently used in the market since the method completely conforms to the EPC C1G2 standard.

Description of the Drawings

The embodiments of the present invention are further described below in combination with drawings, wherein:

Figure 1 shows the schematic diagram of errors that may occur when a reader reads a tag in the prior art;

Figure 2 shows the ending status of the signals when a tag is backscattering as found in the prior art;

Figure 3 shows the process flow wherein the EPC data length is determined based on the first byte in the PC in the prior art;

Figure 4 illustrates an incorrect analysis of the EPC length by the reader as a result of certain errors during receipt of the PC in the prior art;

Figure 5 is a schematic diagram of PC and XPC;

Figure 6 shows the structure of the EPC data when the reader writes one EDC and one ECC into the tag EPC data;

Figure 7 shows a specific EDC and a specific ECC in Figure 6 when the first 5 digits of the PC is used to identify the EPC length of the tag or the 6th digit of the PC is used to identify whether there is valid data in the user memory bank;

Figure 8 shows the process of writing the length of the protected EPC into PC; Figure 9 shows the process when the reader reads a tag with a protected PC- Figure 10 shows a specific EDC and a specific ECC in Figure 6 when the REC digit in an XPC is used to identify the recommissioning of the tag after it is killed;

Figure 11 shows the schematic diagram of tag classification query when both common tags and tags with protected PC are present;

Figure 12 shows the process when the reader reads a tag with a protected PC and a common tag;

Figure 13 is a schematic diagram in which at least one of the two enhanced periods in Embodiments 3 to 5 is chosen to adjust the gain of signal transmission;

Figure 14 is a schematic diagram of the interface defined between a reader and the host connected with it;

Figure 15 shows the process when the reader reads the data in a tag with a fixed EPC;

Figure 16 shows the setting of a real-world manufacturing application with interference sources for simulation purpose in a test;

Figure 17 is a diagram of BER performances vs. interference power;

Figure 18 is a diagram showing the percentage of RN16 timeout vs. interference power;

Figure 19 shows the time range Tinit and TEPCRetry in the reading/writing process;

Figure 20 shows a comparison of the time for normally reading a single tag and the time for reading a single tag using the solutions of the present invention, wherein the range of BER is le-4 to le-2;

Figure 21 shows a comparison of the time for normally reading a single tag and the time for reading a single tag using the solutions described herein, wherein, the range of BER is le-2 to 5e-2;

Figure 22 compares the reading reliability between the method of tag reading according to the present invention wherein the EPC is fixed and the method of supplying power to the tag as described in Siemens' patent application No. 200810004983.0.

Figure 23 compares the reading speed between the tag reading method according to the present invention when the EPC is fixed and the method of supplying power to the tag as described in Siemens' patent application No. 200810004983.0.

Preferred Embodiments

In a radio frequency identification system, data is stored in a tag. Such data may be classified into two types: data, which will be actually used in the radio frequency identification system, and data, which describes the first type of data that will be actually used, the latter being called characteristic description information of the tag. More specifically, all data in the tag is stored in three banks, i.e. tag identifier (TagID) bank, EPC data bank and user memory bank. In this case, the tag characteristic description information is mainly stored in the beginning of the EPC data bank, and the remaining data in said three banks is the data which will be actually used in the RFID system.

The tag characteristic description information is defined mainly through PC and XPC (XPC is defined in the latest UHF RFID standard), as shown in Figure 5. In Figure 5, the PC consists of two bytes and the definition of each bit can be found in the figure to the lower left. In addition, the XPC consists of Wl and W2, with each part consisting of two bytes. Currently, some bits in Wl have been defined, as shown in the figure to the lower right, wherein the bit in digit 0 is the bit Reserved for Future Use. For the reserved byte in W2, there is no definition of any bit in the byte.

The characteristic description information mainly helps the reader to learn the characteristic of a tag so as to effectively read the information stored in the tag. For example, the first 5 bits of the PC identifies the length of the EPC in the EPC bank of the tag, so that the reader can set the length of reading EPC based on this information. Further, the sixth bit of the PC may be used to identify if there is valid data in the user memory so that the reader can determine whether to initiate a data reading command based on this information. Also, the REC of the XPC may identify the recommissioning of the tag after it is killed so that the reader can determine the recommissioning based on this information, thus judging the locking of the user memory bank and adopting a different strategy for reading data. In summary, this characteristic description information has a significant impact on the efficiency of data reading, and reading may fail if an error occurs during transmission, so it is very import to transmit this information reliably.

The core of the present invention is to improve the reliability of data reading by protecting such characteristic description information, and specific solutions may include the following steps:

first, the first reader or the tag encodes the characteristic descriptions with a code which has the function of error detection and error correction and writes the codes into the tag;

second, the first reader or the second reader reads the tag, receives the characteristic descriptions after encoding, and decodes the characteristic descriptions according to the code;

finally, the first reader or the second reader reads the corresponding data according to the characteristic descriptions after the decoding.

A radio frequency identification system comprising a reader and a tag is used below to illustrate the specific embodiments of the present invention. In the radio frequency identification system, the reliability of tag reading depends greatly on the reader' s abilities to capture the RN16 prefix, to capture the prefix of the data in the EPC data bank (hereinafter "the EPC data") and to correct CRC errors when receiving the data in the EPC data bank. The EPC data includes the PC, EPC and CRC, wherein the length of the EPC is very important for the reader to know the end of the EPC backscattering. In Embodiment 1 of the present invention below, there is detailed description of how the reader first protects the length information of the EPC, and then receives the length information of the protected EPC so as to correctly receive the EPC data.

The radio frequency identification system in the Embodiment 1 of the present invention includes more than one reader and a group of tags, wherein each tag has the EPC data and the EPC data further includes the PC, EPC and CRC. The length of the PC is 16 bits, the length of the EPC ranges from 96 bits to 496 bits, and the length of CRC is 16 bits. The length of the EPC is recorded in said PC.

When the reader reads a tag for the first time, it uses an Error Detection Code (EDC) and an Error Correction Code (ECC) to code the PC, and writes the code into EPC data bank. Figure 6 shows the structure of the EPC data when the code is written. In this case, the beginning part is the PC whose length is 16 bits, and is marked as Nl bits for the convenience of subsequent calculation. The PC usually uses five bits in the first byte to record the EPC length. Other than the above- mentioned five bits, the PC has some bits Reserved for Future Use (RFU) . The reader uses two bits of such RFUs to set a protection mark which indicates that the length information of the EPC of the tag is protected. Following the PC is the protection bit of Npro, including one EDC and one ECC. The sum of said Nl bit and Npro bit is marked as Np bits. The EPC comes next, and its length ranges from 96 bits to 496 bits, and is marked as N2 bits. The last one is CRC whose length is 16 bits.

Figure 7 shows a specific EDC and a specific ECC in Figure 6. The EDC picks a CRC of 5 bits and the ECC picks a BCH (31, 21) code, wherein 21 means the length to be coded is 21 bits, that is, a PC of 16 bits plus CRC of 5 bits for use as EDC; 31 means that the length of the coded BCH is 31 bits, therefore, it can be concluded that the length of the ECC is 10 bits (i.e. 31-16-5=10 bits) . In another word, the sum of the EDC and ECC is Npro=15 bits (5+10=15 bits) .

Figure 8 shows the process of writing the length of protected EPC into the PC, including:

First, the length of the EPC to be changed in an open-loop application (that is, the length to change the whole EPC data) is identified. The so-called open-loop application means the tag may be used in multiple loops, for example, the tag may be used in each of the loops, including processing, logistics, distributor, retailer and user. For instance, for a distribution, it may receive different tags from different places, and the EPC length of the tags received from different places may vary. It can be further concluded that, for each of the above loops, the length of EPC received from the previous loop may be different, so it is necessary to protect the tags which have such EPC length changes.

Second, the reader sets the length recorded by the PC to the sum of the lengths of the EPC, EDC and ECC. In other words, the lengths of EDC and ECC are part of the EPC.

Further, the reader sets a protection mark in the RFU of the PC to indicate that the length information of the EPC of the tag is protected. For example, the last two digits of a 16- bit PC may be used as the protection mark.

Then, the reader calculates the EDC for the PC. The calculation process, which is a prior art, is not repeated here . Next, the reader calculates the ECC for the PC and EDC. As with the previous step, the calculation process is a prior art.

Finally, the EDC and ECC are stored in the beginning of the EPC, and its location is shown in Figures 6 and 7. Now the reader can start its normal reading.

The reader will implement the above steps when it reads the tag for the first time, in other words, the length information of the EPC code of the tag is protected after the above steps are performed. If the EPC length changes, for example in the open-loop application mentioned above, the reader needs to write the EDC and ECC into the EPC data bank again.

The writing process described in the above is completed by a reader; however, the process may not be necessarily completed by a reader, and the tag itself may also complete said code writing process.

When said reader, which is writing the EDC and ECC, or another reader is reading the data from the EPC data bank in the tag, the reader performing the reading can obtain the information of the protected PC by decoding, thereby obtaining the correct EPC length. Figure 9 shows the process of a reader reading tags with a protected PC.

Second, when the reader receives the random number RNl 6 from the tag, it sends an acknowledgement command ACK to the tag. When the tag receives the acknowledgement command ACK, it returns the prefix of the EPC. If the reader does not detect the prefix, it will resend the Query command after a certain period of time.

Further, if the reader detects the prefix of the EPC data, it will read the data in the EPC data bank of the tag, and receive the PC, EDC and ECC.

Then, the reader will conduct error detection and error correction for the PC and EDC through the ECC. In other words, if the ECC detects an error in the PC or EDC and it is able to correct such an error, the ECC will correct the error.

Next, the reader detects the error against the PC through the EDC. If an error is detected in the PC, the reader may perform processing by adopting one of the following three ways:

First, the length of the EPC to be received is set to the length of the EPC of the previous tag. It is assumed that the tag is of the same type as the previous one.

Second, the length of the EPC to be received is set at the length of 96 bits. 96 bits are EPC.

Third, the reader first waits for the time required for reading the longest EPC, of which the length is 496 bits, and then a new tag reading process is initiated, that is, the reader resends a Query command to the tag.

When the reader is trying to detect any error in the PC through the EDC, if no error is detected in the PC, that means the reader obtains the correct EPC length; or after the first and second processing methods for the errors detected in PC as described above, it is assumed that the reader obtains the correct EPC length. Therefore, the reader sets the data bits to be received to the length of the EPC plus 32 bits, and prepares to receive the data.

After a certain period of waiting, the reader will receive the EPC data. Then the reader will perform a CRC check on the received data. If the check is successful, the reader will send the next query command QueryRep to the tag, and report the EPC data received to the host connected to the reader. However, the EPC data reported to the host does not include ECC or EDC. If the check fails, the reader will resend an acknowledgement command ACK to the tag and test the prefix of the EPC.

In Embodiment 2 of the present invention, the sixth bit of the PC is protected. The bit may be used to identify if there is valid data in the User Memory bank, and the reader determines whether to initiate the data reading command based on this information.

Since both the sixth bit to be protected and the first five bits to be protected in Embodiment 1 for recording the EPC length are located in the PC, the protection process is similar to that in Embodiment 1. In this case, the EDC and ECC that are the same as those in Embodiment 1 may be used to encode the PC, and write the code into EPC data bank. The EDC and ECC used to encode the PC are shown in Figure 7. The process of encoding the PC by using the EDC and ECC is shown in Figure 8. The reader reads the EPC data in the tag, receives the encoded PC, and encodes the PC, as shown in Figure 9. After encoding, the PC is obtained. The sixth bit of the PC is used to determine whether to initiate the data reading command and read the data in said user memory data bank.

In Embodiment 3 of the present invention, the REC bits of the XPC are protected. Such bits can identify the recommissioning of the tag after it is killed so that the reader can determine the recommissioning of the tag, thus judging the locking of the user memory data bank to take a different strategy for reading data. The protection process is similar to those in the above two embodiments, with the difference that:

First, since the REC bit is the Wl stored in the XPC, so the Wl of the PC and XPC is to be protected in Embodiment 3, and as such the EDC and ECC used are different from the two described in the above. Drawing 10 (a) shows a specific EDC and a specific ECC of Figure 6 when the REC in the XPC is used to identify the recommissioning of the tag after it is killed; wherein, the EDC picks the CRC of the fifth bit, and the ECC picks the BCH (63, 39) code.

Second, the process of decoding of the PC using EDC and ECC is as shown in Figure 8 except that the PC in Figure 8 is changed to Wl of the PC and XPC. Further, the EDC and ECC are stored in the tag. Different from the above two embodiments, the encoding can be stored at a different place in the tag, and Figure 10 (b) and Figure 10 (c) show these two storage methods, respectively. Since at present W2 of the XPC is reserved, the EDC and ECC in Figure 10 (b) are stored in W2 of the XPC. In Figure 10 (c) , however, the EDC and ECC are stored in the beginning of the EPC.

The reader reads the EPC data in the tag, receives the encoded PC and XPC, and encodes the PC and XPC in a process similar to that shown in Figure 9. After the encoding, the PC and XPC are obtained. The REC bits of the XPC will determine the recommissioning of the tag, thus judging the locking of the user memory data bank to take a different strategy for reading the data.

As a supplement to Embodiments 1 to 3, in the reading area of the reader there may be tags with a protected PC and common tags without a protected PC.

Figure 11 shows the schematic diagram of tag classification query when there are both common tags and tags with protected PC. In such a case, the reader first sends a selection command Select to all tags in its reading area, and selects the tags which have the protection marks set in the RFUs. Then, the reading process for the tags with protected PCs shown in Figure 9 is imitated. Next, the reader sends a selection command Select to its reading area again, selects the common tags which do not have the protection marks set in the RFUs, and then reads the data in the common tags which do not have said protection marks set according to the common reading process.

Figure 12 shows how said reader reads a tag with a protected PC and a common tag, respectively.

Of course, the reader may also first select the data in the common tags, and then read the data in the tags with a protected PC.

In addition, in Embodiment 1, this is, mainly for the process of receiving EPC data, a solution for CRC check error as a result of any error occurring in the transmission of any bit in the EPC data. It is mentioned in the background technology that, there are three circumstances that may cause failure of reading EPC data, and they are: the reader has timeout reading the RN16 prefix, the reader has time-out reading the EPC data prefix, and the reader has errors performing the CRC check. Solutions for the first two circumstances have been presented in Siemens' patent application No. 200810004983.0. In order to further improve the reliability of the reader in reading data in the tags and as a solution to improve the embodiments of the present invention, the reader may choose the period waiting to receive RN16 as the enhanced period while using the method of protecting EPC length according to the present invention; and in the enhanced period, the reader adjusts the gain of signal sending so that the carrier signal in the enhanced period is sent with an enhanced sending power.

As a solution to the improvement of the embodiments according to the present invention, the reader may choose the period waiting to receive EPC data as the enhanced period while using the method of protecting the EPC length according to the present invention, and in the enhanced period, the reader adjusts the gain of signal sending so that the carrier signal in the enhanced period is sent with an enhanced sending power. As another solution to the improvement of the embodiments according to the present invention, the reader may choose the period waiting to receive EPC data as the enhanced period while using the period waiting to receive RN16 and the period waiting to receive EPC length data as the enhanced period, and in the enhanced period, the reader adjusts the gain of signal transmission so that the carrier signal in the enhanced period is sent with an enhanced sending power. Figure 13 is a schematic diagram showing that at least one of the two enhanced periods in Embodiments 3 to 5 is chosen to adjust the gain of signal transmission.

The above embodiments and their improvements are examples of using the present invention in open-loop applications. However, other than open-loop applications, there are many occasions of close-loop applications. In a close-loop application, the tag usually circulates within one system, for example, circulating in a processing cycle. Since such a tag is in a close-loop occasion, usually it can be recycled instead of entering the subsequent circulation cycle. For tags in such close-loop applications, the EPC of the tags is fixed. For the purpose of reliably reading EPC in the close-loop applications, the present invention provides another solution.

The radio frequency identification system in Embodiment 4 of the present invention includes one or more readers and a group of tags, wherein each tag has the EPC data and the EPC data further includes the PC, EPC and CRC. The length of the PC is 16 bits, the length of the EPC is a fixed number of bits ranging from 96 bits to 496 bits, and the length of CRC is 16 bits. The length of the EPC is recorded in said PC.

According to the solutions of the present invention, first, an interface is defined between the reader and the host connected with it. The host configures the EPC to a fixed length n_EPC, and then the EPC length is communicated to the reader through the interface.

Second, when the reader receives the EPC length, it will store the EPC length n_EPC in the register. Figure 14 shows the schematic diagram of the interface defined between a reader and the host connected with it.

After the above configuration and storage, the reader can read the data in the tag with a fixed EPC. Figure 15 shows how a reader reads the data in a tag with a fixed EPC.

Further, if the reader detects the prefix of the EPC, it will obtain the EPC length n_EPC stored in the register. In other words, in this embodiment, although the EPC length is recorded in said PC, in the process of actual use, the EPC length information is obtained by the reader from its register instead of the PC. In this way, it can be ensured that the EPC length will be obtained even when there is an error in the bits that record the EPC length information in the PC during reading of EPC data.

Then the reader sets the data bits to be received to the EPC length n_EPC plus 32 bits, and prepares to receive the data.

After waiting for a certain period of time, the reader will receive the EPC data. Then the reader will perform a CRC check on the received data. If the check is successful, the reader will send the next query command QueryRep to the tag, and report the EPC data received to the host connected to the reader. If the check fails, the reader will resend an acknowledgement command ACK to the tag and test the prefix of the EPC.

Similar to the improvement solution to Embodiment 1, Embodiment 4 can also be combined with Siemens' patent application No. 200810004983.0 to further improve the reliability of data reading. As an improvement of Embodiment 4, the reader may choose the period waiting to receive RN16 as the enhanced period while using the method of reading a tag with a fixed EPC length according to the present invention, and in the enhanced period, the reader adjusts the gain of signal transmission so that the carrier signal in the enhanced period is sent with an enhanced sending power.

As another improvement of Embodiment 4, the reader may choose the period waiting to receive EPC data as the enhanced period while using the method of reading tags with a fixed EPC length according to the present invention, and in the enhanced period, the reader adjusts the gain of signal transmission so that the carrier signal in the enhanced period is sent with an enhanced sending power.

As another improvement of Embodiment 4, the reader may choose the two periods, i.e. the period waiting to receive RN16 and the period waiting to receive EPC data, as the enhanced period while using the method of reading tags with a fixed EPC length according to the present invention, and in the enhanced period, the reader adjusts the gain of signal transmission so that the carrier signal in the enhanced period is sent with an enhanced sending power.

As described in the above, Embodiment 1 and its improvements are the solutions to reading tags in the open-loop applications, and Embodiment 4 and its improvements are the solutions to reading tags in the close-loop applications. As a matter of fact, a mode selection method can be set up in the reader to distinguish the open loop and the close loop, so that the reader will know if it is reading in an open-loop application or in a close-loop application. When the mode selection method identifies that the reader is using the first mode, the solution for reading tags in an open-loop application is used, that is, the solution of protecting EPC length. When the mode selection method identifies that the reader is using the second mode, the solution for reading tags in a close-loop application is used, that is, the solution of reading tags with a fixed EPC length.

Corresponding to the method of protecting the EPC length as shown in Embodiment 1 of the present invention, the present invention further provides a reader for reading data in a tag in the radio frequency identification system, and the reader includes :

a writing unit for writing said code into a tag;

a reading unit for reading the data in said tag and receiving the encoded characteristic description information; a decoding unit for decoding the characteristic description information through said code;

a receiving unit for reading the corresponding data according to the decoded characteristic description information .

In this case, said writing unit further includes:

a setting unit for setting the length of the PC in said tag to the sum of the lengths of the EPC, EDC and ECC, and setting a protection mark in the RFU of said PC;

a calculating unit for calculating said EDC for said PC, and calculating said ECC for said PC and said EDC; a storage unit for storing said EDC and said ECC into the beginning of said EPC.

In another aspect, the reader further includes a command sending module which sends a protected tag selection command to the tags in its writing area, selects the tags with a protection mark set in the RFU, and then reads the data in the protected tags according to the method of protecting the EPC length; or sends a common tag selection command to the tags in its writing area, selects the tags without a protection mark set in the RFU, and then reads the data in the common tags according to the common reading process.

For the method of reading tags with a fixed EPC length as shown in Embodiment 4, the present invention provides another reader for reading data in tags in the radio frequency identification system, and said reader includes:

an interface unit for defining an interface between the reader and the host connected with said reader, and the host configures the EPC to a fixed length through the interface; a storage unit for storing the EPC length configured by the host in the reader's register;

a reading unit for acquiring the length of the tag' s EPC from the register of the reader when reading the data in the tag;

The following tests have been done in order to further demonstrate the advantages of the method according to the present invention. These tests are to simulate the real-world manufacturing applications with interference sources. The settings of the tests are shown in Figure 16. In Figure 16, the two readers are based on the Indy RlOOO platform. Table 1 shows the setting of the test parameters. Table 1 Setting of Test Parameters

The reader for reading the data will be operated in accordance with the link parameters listed in Table 2.

Table 2 Link parameters of the reader

Figure 17 shows the BER performance vs. interference power. From Figure 17, it can be seen that BER increases quickly as the interference power increases. The methods of the present invention are usually used when BER is below 0.1. Figure 18 is a diagram of percentage of RN16 time-out vs. interference power. From Figure 18, it can be seen that in a bigger BER zone, there are many RN16 time-outs.

To investigate the reading rate of a single tag in the normal reading process and in the methods of the present invention, the time for reading a single tag based on these two reading methods will be compared and simulated.

For the normal reading process, formula (1) may be used to calculate the time for reading a single tag.

In this case, P_b is BER; P_e is the PER transmitted by package 16 of PC+EPC+CRC; P_PC is the probability of PC errors; P_Epc is the probability of EPC data errors; T is the time for reading a single tag based on the basic process. Formula (1) has no restrictions on the number of attempts to resend the ACK command. T_irilt and T_EPCRetry are the time intervals used at different stages of the protocol shown in Figure 19.

In the method of the present invention for obtaining the EPC correctly by protecting the PC, the encoding is made with CRC-5, BCH (31, 21), and formula (2) can be used to calculate the time for reading a single tag through the method of the present invention.

P_EPC = ι-(i-P_b)^N2

P P v T -A- P v T

rp _ rp , rp ^λ _e , ^λ PC ¹PCRETRY ^ ^λ EPC ¹EPCRETRY . ψ

^{1 ~ 1}IHIt ^"•^{" 1}EPCReI₁J ^""^" _* p p p ^{'t l} ζ)ueιy Rep

^ ^{~ 1 ^}e ¹ PC ^{+ 1} EPC / 2 )

In this case, N_P is the number of digits of PC, and the rest have the same meanings as those in formula (1) .

Compare the time for reading a single tag normally and the time for reading a single tag using the method of the present invention, the results are shown in Figures 20 and 21.

Based on the simulation results, it can be concluded that, when the BER is small, the performance of reading a tag using the method of the present invention is similar to that of the normal reading process (due to use of redundancy, the method of the present invention has a slightly poorer performance than the normal reading process) . When the BER is big (BER>=le-3) , there is greater advantage in using the method of the present invention to read tags. (For example, when BER=O.05, over half of the reading time can be saved by using the method of the present invention to read a tag) . Therefore, the method of the present invention can effectively solve the problems of CRC errors .

Additionally, to evaluate the overall performance of the method of the present invention, the method for reading tags with a fixed EPC according to the present invention and the method of supplying power to tags as described in the patent application No. 200810004983.0 of Siemens, or the combination of these two methods are implemented on the Indy RlOOO platform. Specifically, (1) normal reading is performed; (2) the tags are read using the methods of fixed EPC according to the present invention; (3) the tags are read using the method of fixed EPC according to the present invention, and the period of time waiting to receive RN16 is selected as the enhanced period for supplying power to the tags; (4) the tags are read using the method of fixed EPC according to the present invention, and the period of time waiting to receive EPC data is selected as the enhanced period for supplying power to the tags; (5) the tags are read using the method of fixed EPC according to the present invention, and the period of time waiting to receive RN16 and the period of time waiting to receive EPC data are selected as the enhanced period for supplying power to the tag. The results of comparing the reading reliability and reading rates between these five methods are shown in Figures 22 and 23. It can be seen in these two drawings that:

first, the RN16 time-out, EPC time-out and CRC errors are reduced, leading to greatly improved rates of success in reading tag data by the reader. When the interference frequencies range from -9dBm to -5dBm, the success rate of reading 1000 times in the method according to the present invention is approximately 40% higher than that in the normal reading. Especially, when the interference frequency is -9dBm, the success rate of reading 1000 times in the method according to the present invention is approximately 90%, a very high reading reliability. However, the success rate of reading 1000 times in the normal reading is only 50%.

Second, the reader can read a tag at a higher speed. As shown in Figure 23, when the interference frequencies are in the range of -5dBm to -9dBm, 25 more tags can be read using the method according to the present invention compared with the normal reading methods. Especially, the reading speed of the method according to the present invention can be as high as 100 tags per second, which meets the requirements of most RFID applications .

Finally, the method according to the present invention may cause a little interference to other devices. The reason is that the reader will transiently increase its power in order to have a higher reading speed, but the power will immediately be restored to the normal level.

In summary, the present invention provides a method of protecting the characteristic description information of tags in the radio frequency identification system so as to achieve a higher reading speed and a higher reliability. Based on the measurement results, the present invention can greatly increase tag reading reliability and speed, especially in a noisy environment. Therefore, the method is ideal for improving reading/writing reliability and efficiency for applications in noisy environments, for example, manufacturing applications. On the other hand, the method can be easily implemented only by changing the reader firmware. Furthermore, the method is completely in compliance with the EPC C1G2 standard, and can be easily implemented in existing tags and readers.

The above only describes the preferred implementation of the method according to the present invention. It should be noted that, for those skilled in the art, certain improvements and modifications may be made without departing from the spirit of the present invention, and such improvements and modifications should also fall within the protective scope of the present invention.

Claims

1. A method for reading data in tags in a Radio Frequency Identification (RFID) system, wherein said RFID system includes more than one reader and a group of tags and each of said tags includes a group of data and a group of characteristic descriptions, wherein the method includes the steps of:

(1) the first reader or said tag encodes the characteristic descriptions using a code capable of error detection and error correction and writes said code into said tag;

(3) said first reader or second reader reads the corresponding data according to the decoded characteristic descriptions.

2. The method for reading the data in tags in the RFID system as claimed in claim 1, characterized in that in said Step (1), said code capable of error detection and error correction includes an Error Detection Code (EDC) and an Error Correction Code (ECC) .

3. The method for reading the data in tags in the RFID system as claimed in claim 2, characterized in that the data of said tag are the data in the data bank of the Electronic Product Code (EPC) , said characteristic descriptions of said tag are the Protocol Control (PC) , and the length of the EPC in said EPC data bank is recorded in said PC;

in said Step (1), said first reader encodes said PC using said EDC and said ECC, and writes the code into said tag's EPC data; in said Step (2), said first reader or second reader reads the EPC data in said tag, receives said encoded PC, and decodes said encoded PC; in said Step (3) , said first reader or second reader sets the data bits to be received according to the decoded PC and prepares to receive the data.

4. The method for reading the data in tags in the RFID system as claimed in claim 3, characterized in that said Step (1) further includes the following steps:

(13) said EDC is calculated for said PC;

(14) said ECC is calculated for said PC and said EDC;

(15) said EDC and said ECC are stored in the initial position of said EPC.

5. The method for reading the data in tags in the RFID system as claimed in claim 3, characterized in that in said Step (2), the decoding of said encoded PC by said first reader or second reader further includes;

said first reader or second reader detects any error in said PC through said EDC to obtain the correct length of said EPC.

6. The method for reading the data in tags in the RFID system as claimed in claim 5, characterized in that if said EDC detects an error in said PC, said first reader or second reader will set the length of said EPC to be received to the length of the EPC of the previous tag.

7. The method for reading the data in tags in the RFID system as claimed in claim 5, characterized in that if said EDC detects an error in said PC, said first reader or second reader will set the length of said received EPC to 96 bits.

8. The method for reading the data in tags in the RFID system as claimed in claim 5, characterized in that, if said EDC detects an error in said PC, said first reader or second reader will first wait for a period of time required for reading the longest EPC, and then initiate a new tag reading process.

9. The method for reading the data in tags in the RFID system as claimed in claim 8, characterized in that said longest EPC is 496 bits.

10. The method for reading the data in tags in the RFID system as claimed in claim 3, characterized in that in said Step (3), said first reader or second reader sets the data bits to be received to the result of the length of said EPC plus 32 bits.

11. The method for reading the data in tags in the RFID system as claimed in claim 3, characterized in that, if the length of said EPC changes, said first reader will rewrite said EDC and said ECC into said electronic product code data.

12. The method for reading the data in tags in the RFID system as claimed in claim 3, characterized in that it further includes the following step before said Step (1) :

said first reader or second reader sends a protected tag selection command to the tags in its read/write area, to select the tags in said read/write area which have said protection marks set in the RFUs .

13. The method for reading the data in tags in the RFID system as claimed in claim 12, characterized in that it further includes the following step after said Step (3) : said first reader or second reader sends a normal tag selection command to the tags in its read/write area, to select the normal tags in its read/write area which do not have said protection marks set in the RFUs, and the data in said normal tags which do not have said protection mark set, are read according to the normal reading process.

14. The method for reading the data in tags in the RFID system as claimed in claim 3, characterized in that it further includes the following steps before said Step (1) : setting a mode selecting method in said first reader or second reader so that said Step (1) will start when said reader selects said mode selecting method.

15. The method for reading the data in tags in the RFID system as claimed in claim 3 or claim 4, characterized in that said first reader or second reader selects at least one period from the period of waiting to receive RN16 and the period of waiting to receive the EPC data as the enhanced period, and said reader adjusts the gain of signal transmission so that the carrier signal in said enhanced period will be sent with an enhanced sending power.

16. The method for reading the data in tags in the RFID system as claimed in claim 2, characterized in that the data of said tag includes the data in the EPC data bank and the data in the user memory bank, the characteristic description information of said tag are PC, and said PC identifies if there is valid data in said user memory bank;

in said Step (1), said first reader encodes said PC by using said EDC and said ECC, and writes said codes into said tag' s EPC data;

in said Step (2) , said first reader or second reader reads the EPC data in said tag, receives said encoded PC, and decodes said encoded PC; in said Step (3) , said first reader or second reader decides based on the decoded PC whether or not to send the data reading command to read the data in said user memory bank.

17. The method for reading the data in tags in the RFID system as claimed in claim 16, characterized in that said Step (1) further includes the following steps:

(12) a protection mark is set in the RFU of said PC;

(13) said EDC is calculated for said PC;

(14) said ECC is calculated for said PC and said EDC;

(15) said EDC and said ECC are stored in the initial position of said EPC.

18. The method for reading the data in tags in the RFID system as claimed in claim 2, characterized in that the data of said tag includes the data in the EPC data bank and the data in the user memory bank, the characteristic description information of said tag is PC and Extended Protocol Control (XPC) , and said XPC identifies the recommissioning of said tag after it is killed;

19. The method for reading the data in tags in the RFID system as claimed in claim 18, characterized in that said Step (1) includes : (11) the length recorded by said PC is set to the sum of the lengths of said EPC, EDC, and ECC;

(12) a protection mark is set in the RFU of said PC;

(13) said EDC is calculated for said PC;

(14) said ECC is calculated for said PC and said EDC;

(15) said EDC and said ECC are stored in said tag.

20. The method for reading the data in tags in the RFID system as claimed in claim 19, characterized in that in said Step (15), said EDC and said ECC are stored in the initial position of said EPC.

21. The method for reading the data in tags in the RFID system as claimed in claim 19, characterized in that in said Step (15), said EDC and said ECC are stored in said XPC.

22. A method for reading the data in the tag in the RFID system, wherein said RFID system includes more than one reader and a group of tags, each of said tags includes the data in the EPC data bank, said each EPC data includes the PC, EPC and Cyclic Redundancy Check (CRC) , characterized in that the method includes the following steps:

23. The method for reading the data in tags in the RFID system as claimed in claim 22, characterized in that in said Step (4), said first reader or second reader sets the data bits to be received to the length of said EPC plus 32 bits.

24. The method for reading the data in tags in the RFID system as claimed in claim 22 or claim 23, characterized in that it further includes the following step before said Step (1): setting a mode selecting method in said first reader or second reader so that said Step (1) will start when said reader selects said mode selecting method.

25. The method for reading the data in tags in the RFID system as claimed in claim 22 or claim 23, characterized in that said reader selects at least one period from the period of waiting to receive RN16 and the period of waiting to receive EPC data as the enhanced period, and said reader adjusts the gain of signal transmission so that the carrier signal in said enhanced period will be sent with an enhanced sending power.

26. A reader for reading the data in tags in the RFID system, characterized in that said reader includes:

an encoding unit for encoding the characteristic descriptions using a code capable of error detection and error correction; a writing unit for writing said code into a tag;

a decoding unit for decoding the characteristic descriptions using said code;

27. The reader for reading the data of the tag in the RFID system as claimed in claim 26, characterized in that said writing unit further includes: a setting unit for setting the length of the PC in said tag to the sum of the lengths of the EPC, EDC and ECC, and setting a protection mark in the RFU of said PC;

a calculating unit for calculating said EDC for said PC, and calculating said ECC for said PC and said EDC;

28. The reader for reading the data in tags in the RFID system as claimed in claim 27, characterized in that said reader further includes a command sending module for sending a protected tag selection command to the tags in its read/write area to select the tags in the read/write area which have said protection marks set in the RFU; or for sending a common tag selection command to the tags in its read/write area to select the tags in the read/write area which do not have said protection marks set in the RFU, and read the data in said common tags which do not have said protection marks according to the common reading process.

29. A reader for reading the data in tags in the RFID system, characterized in that, said reader includes:

a reading unit for acquiring the length of said tag' s EPC from the register of the reader when reading the data in said tag; a receiving unit for setting the data bits to be received and preparing to receive the data.