Large-scale multi-tag RFID system information collection method based on collision stripping

Abstract

The invention discloses a large-scale multi-tag RFID system information collection method based on collision stripping, and the method employs standard Manchester encoding on a physical layer in a multi-tag RFID system. When the time slot of label transmission information is determined, a single-example time slot is considered, and object information which is not obtained in a corresponding collision time slot is decoded by using information obtained in the single-example time slot in combination with the characteristic that a plurality of labels on the same object share information and the decoding characteristic of Manchester encoding. Compared with an existing related protocol in which only a singleton time slot is used for transmitting label information, the method has the advantages that collision time slots are fully utilized, the information of each object is ingeniously extracted by mastering the relationship between different types of time slots, and the utilization rate of the time slots and the information throughput per unit time are improved.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency identification technology, and more specifically, to a large-scale multi-tag RFID system information collection method based on collision peeling. Background Art

[0002] Nowadays, Radio-Frequency Identification (RFID) technology plays a very important role in the Internet of Things, providing an effective solution for the identification, tracking and management of objects. Compared with traditional barcodes, RFID technology has many advantages, such as no need for visual recognition, high-speed reading and multi-tag recognition, long-distance recognition, large-capacity storage, rewritable and dynamic update, etc. With the rapid development of the global Internet of Things market and the growing demand for applications, RFID technology is becoming the focus of attention in all walks of life. From inventory management in the retail industry to production tracking in smart manufacturing, from medical equipment management in smart healthcare to cargo tracking in smart logistics, the application of RFID technology is increasingly penetrating into daily life and work.

[0003] A typical RFID system consists of an RFID tag, an RFID reader, an antenna, and a backend server, which transmit and communicate data through radio signals. (1) Reader: The reader is the bridge between the RFID tag and the backend server. It is responsible for sending radio signals to nearby RFID tags and receiving the tag's response data, thus realizing two-way data transmission and communication. (2) Tag: The tag in the RFID system is a passive or active device used to store and transmit data to identify and track objects. Tags usually consist of a chip and an antenna and can be attached to the surface of an object or embedded inside an object. Each tag has a unique 96-bit ID to identify the object it is bound to. For example, the 96-bit EPC code consists of four fields: an 8-bit header, a 28-bit manufacturer identification code, a 24-bit object classification code, and a 36-bit item serial number. (3) Backend server: The backend server is responsible for receiving, processing, and managing the data read from the RFID reader, and provides users with a variety of functions and application interfaces to identify, track, and manage objects. With the continuous development and popularization of RFID technology, the functions and performance of the backend server are also constantly improving, providing strong support for the development of IoT applications.

[0004] The purpose of the information collection protocol is to collect target information from the tags of the RFID system. For sensor-enhanced RFID systems, the main purpose is to collect the sensory data of the tag sensors, such as the state of the object, the information about the surrounding environment of the object, etc. In the RFID system, the tag can only communicate with the reader, and the tags cannot communicate with each other. If multiple tags send information to the reader at the same time, the collision of signals will cause the reader to be unable to recognize the information of each tag. There are currently three mainstream solutions to this problem: tree-based algorithms, Aloha-based algorithms, and polling-based algorithms. Existing studies often select a representative tag from multiple tags of an object to transmit information when collecting information about the target object, and other tags do not participate in the information collection process. This requires setting the status (participation or non-participation) for each tag, and forcibly converting the multi-tag system into a single-tag system, abandoning the multi-tag collaboration brought about by multiple tags of the same object sharing the same information. In addition, after selecting the representative tag, previous studies only considered singleton slots when selecting the time slot for transmitting information, and abandoned empty slots and collision slots, which greatly limited the frame throughput. Summary of the invention

[0005] The present invention provides a large-scale multi-tag RFID system information collection method based on collision peeling, which solves the technical problem in the prior art that signal collision will cause the reader to be unable to identify the information of each tag.

[0006] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0007] The present invention provides a large-scale multi-tag RFID system information collection method based on collision peeling, comprising:

[0008] Obtain the IDs of all tags in the multi-tag RFID system and the object information they belong to. If the object is a target object, all tags under the object are classified as target tags. If the object is not a target object, all tags under the object are classified as non-target tags.

[0009] Using several seeds of a uniform hash function obtained randomly and a uniform hash function, the IDs of all tags are hashed and mapped to several repeatable virtual time slots of a preset bit vector VF;

[0010] According to the label classification results, the virtual representative time slot of each target object is obtained from the mapped multiple repeatable virtual time slots;

[0011] constructing an indication vector according to the preset bit vector VF and the virtual representative time slot of each target object;

[0012] Constructing a first sequence according to the indicator vector;

[0013] The reader broadcasts the length of the bit vector VF, several seeds, and a uniform hash function to all tags;

[0014] Each tag performs a hash operation according to the plurality of seeds and a uniform hash function;

[0015] A combined signal is formed according to the results of hash operations of all tags and the first sequence and is received by the reader;

[0016] The reader sorts the combined signals according to the receiving time and constructs an execution frame EF;

[0017] According to the virtual representative time slots of the target objects and the execution frame EF, the tag ID and the object information contained in the signal of each time slot in the execution frame EF are determined.

[0018] Furthermore, the length of the preset bit vector VF is f, and f is not less than the number of target objects. Each bit of the preset bit vector VF is called a virtual time slot.

[0019] Furthermore, using several seeds of the uniform hash function obtained randomly and the uniform hash function, the IDs of all tags are hashed and mapped to several repeatable virtual time slots of the preset bit vector VF, including:

[0020] h i =H(ID i ,s r )mod f

[0021] In the formula, h i is the ith tag ID i The mapping result, H(·) is a uniform hash function, s r For the rth seed, 1≤r≤k, k different uniform hash functions are simulated by using k different seeds.

[0022] Furthermore, according to the label classification result, a virtual representative time slot of each target object is obtained from the mapped multiple repeatable virtual time slots, including:

[0023] Among the multiple repeated virtual time slots after mapping, at least one virtual time slot to which a non-target tag is mapped is marked as a virtual time slot to be eliminated;

[0024] Then, from the remaining unmarked virtual time slots, a random selection is made from the homogeneous virtual time slots mapped to the tag ID corresponding to each target object as the virtual representative time slot of the current target object, and the unselected homogeneous time slots are marked as eliminated virtual time slots; for heterogeneous virtual time slots, if there is only one target object that does not have a virtual representative time slot, then the virtual time slot is marked as the virtual representative time slot of the target object, and the rest are marked as eliminated virtual time slots, until all virtual time slots mapped to tags in the bit vector VF are marked or all target objects have virtual representative time slots;

[0025] The homogeneous virtual time slot is a time slot including only one object information, and the heterogeneous virtual time slot is a time slot including multiple object information.

[0026] Further, constructing an indication vector according to the preset bit vector VF and the virtual representative time slot of each target object includes:

[0027] The length of the indication vector is equal to the length of the preset bit vector VF. The indication vector is 1 at the position corresponding to the virtual representative time slot of each target object and 0 at other positions, thereby obtaining the indication vector.

[0028] Further, according to the indicator vector, a first sequence is constructed, including:

[0029] After arranging the position indexes corresponding to the virtual representative time slots in the indication vector in ascending order, we obtain:

[0030] W={w 1 ,w 2 ,w 3 ,…,w m}

[0031] In the formula, w 1 ,w 2 ,w 3 ,…,w m is the position index corresponding to the virtual representative time slots arranged in ascending order;

[0032] Let w 0 =0, the first sequence is:

[0033] ΔD={Δd 1 ,Δd 2 ,Δd 3 ,…,Δd m}

[0034] Δd y =w y -w y-1

[0035] In the formula, Δd y Indicates wy and w y-1 The difference.

[0036] Furthermore, according to the results of hash operations of all tags and the first sequence, a combined signal is formed and received by the reader:

[0037] Each tag holds a register that is initially 0. Each time it receives the value of the incremental sequence broadcast by the reader, the register is added with the corresponding value, and it is determined whether the value in the register is the same as the previously recorded hash result. If they are equal, the tag information is transmitted to the reader. If they are not equal, it waits for a period of time until the next update.

[0038] The transmitted tag information constitutes a combined signal and is received by the reader.

[0039] Furthermore, the transmitted tag information constitutes a combined signal received by the reader, including:

[0040] The transmitted tag information is received by the reader according to the Manchester code to form a combined signal.

[0041] Further, according to the virtual representative time slots of the target objects and the execution frame EF, the tag ID and the object information contained in the signal of each time slot in the execution frame EF are determined, including:

[0042] For homogeneous time slots, the corresponding tag ID and the object information to which it belongs are directly obtained;

[0043] For heterogeneous time slots, based on the known tag IDs and the object information they belong to, the unknown tag IDs and the object information they belong to are obtained in sequence until the object information of all target objects is obtained.

[0044] Furthermore, all the tags also include a flag bit, which is initialized to 1. If the information of the object to which the tag belongs has been received by the reader, it is updated to 0 and no longer participates in the information collection process. The reader will only perform hash calculations on the tag ID with a flag bit of 1, and only tags with a flag bit of 1 will respond to the reader's commands.

[0045] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0046] The present invention considers the problem of tag information collection in a large multi-tag RFID system, and proposes a large multi-tag RFID system information collection method based on collision stripping. Compared with the existing methods, the present invention not only uses singleton time slots when specifying the time slots for tag transmission information, but also considers using some collision time slots by utilizing the characteristics of Manchester encoding. Since multiple tags on the same object share information, the object information that is not obtained in the corresponding collision time slot is decoded by using the information obtained in the singleton time slot. In this way, the deficiencies of existing research are solved to a certain extent, and the utilization rate of time slots and the throughput of information per unit time are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A schematic diagram of a flow chart of a method for collecting information of a large multi-tag RFID system based on collision peeling provided by an embodiment of the present invention;

[0048] Figure 2 A schematic diagram of the Manchester encoding principle provided by an embodiment of the present invention;

[0049] Figure 3 A schematic diagram of the principle of determining the tag ID and the object information contained in the signal of each time slot provided by an embodiment of the present invention;

[0050] Figure 4 A schematic diagram of selecting a virtual representative time slot provided by a specific embodiment of the present invention;

[0051] Figure 5 A schematic diagram of constructing an execution frame provided by a specific embodiment of the present invention;

[0052] Figure 6 It is a schematic diagram of extracting target object information based on collision stripping in a specific embodiment of the present invention;

[0053] Figure 7 A schematic diagram of performance comparison of various algorithms under different numbers of objects and numbers of tag information bits provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0054] The drawings are for illustrative purposes only and should not be construed as limiting the present patent;

[0055] In order to better illustrate the present embodiment, some parts in the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product;

[0056] It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0057] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0058] Example

[0059] This embodiment provides a large-scale multi-tag RFID system information collection method based on collision peeling, such as Figure 1 As shown, including:

[0060] Obtain the IDs of all tags in the multi-tag RFID system and the object information they belong to. If the object is a target object, all tags under the object are classified as target tags. If the object is not a target object, all tags under the object are classified as non-target tags.

[0061] Using several seeds of a uniform hash function obtained randomly and a uniform hash function, the IDs of all tags are hashed and mapped to several repeatable virtual time slots of a preset bit vector VF;

[0062] According to the label classification results, the virtual representative time slot of each target object is obtained from the mapped multiple repeatable virtual time slots;

[0063] constructing an indication vector according to the preset bit vector VF and the virtual representative time slot of each target object;

[0064] Constructing a first sequence according to the indicator vector;

[0065] The reader broadcasts the length of the bit vector VF, several seeds, and a uniform hash function to all tags;

[0066] Each tag performs a hash operation according to the plurality of seeds and a uniform hash function;

[0067] A combined signal is formed according to the results of hash operations of all tags and the first sequence and is received by the reader;

[0068] The reader sorts the combined signals according to the receiving time and constructs an execution frame EF;

[0069] According to the virtual representative time slots of the target objects and the execution frame EF, the tag ID and the object information contained in the signal of each time slot in the execution frame EF are determined.

[0070] In a further embodiment, the length of the preset bit vector VF is f, f is not less than the number of target objects, and each time slot of the preset bit vector VF is called a virtual time slot.

[0071] In this embodiment, the preset bit vector VF is initialized to be completely empty.

[0072] In a further embodiment, a number of seeds of a uniform hash function obtained randomly and a uniform hash function are used to perform a hash operation on the IDs of all tags and map them to a number of repeatable virtual time slots of a preset bit vector VF, including:

[0073] h i =H(ID i ,s r )mod f

[0074] In the formula, h i is the ith tag ID i The mapping result, H(·) is a uniform hash function, s r For the rth seed, 1≤r≤k, k different uniform hash functions are simulated by using k different seeds.

[0075] In a further embodiment, according to the label classification result, a virtual representative time slot of each target object is obtained from the mapped multiple repeatable virtual time slots, including:

[0076] Among the multiple repeated virtual time slots after mapping, at least one virtual time slot to which a non-target tag is mapped is marked as a virtual time slot to be eliminated;

[0077] Then, from the remaining unmarked virtual time slots, a random selection is made from the homogeneous virtual time slots mapped to the tag ID corresponding to each target object as the virtual representative time slot of the current target object, and the unselected homogeneous time slots are marked as eliminated virtual time slots; for heterogeneous virtual time slots, if there is only one target object that does not have a virtual representative time slot, then the virtual time slot is marked as the virtual representative time slot of the target object, and the rest are marked as eliminated virtual time slots, until all virtual time slots mapped to tags in the bit vector VF are marked or all target objects have virtual representative time slots;

[0078] The homogeneous virtual time slot is a time slot including only one object information, and the heterogeneous virtual time slot is a time slot including multiple object information.

[0079] In this embodiment, the virtual representative time slot is used to indicate the time slot actually used to transmit the tag. The time slot involving w (w ≥ 2) object information is called w-heterogeneous time slot. When marking the virtual heterogeneous time slot, start with the 2-heterogeneous virtual time slot. If one of the target objects already has a virtual representative time slot and the other does not, then the time slot is marked as the virtual representative time slot of the latter, and the remaining 2-heterogeneous virtual time slots that do not meet the conditions are marked as virtual time slots to be eliminated. Similarly, 3-heterogeneous virtual time slots, 4-heterogeneous virtual time slots, etc. are processed in sequence until the end condition is met.

[0080] In a further embodiment, constructing an indication vector according to the preset bit vector VF and the virtual representative time slot of each target object includes:

[0081] The length of the indication vector is equal to the length of the preset bit vector VF. The indication vector is 1 at the position corresponding to the virtual representative time slot of each target object and 0 at other positions, thereby obtaining the indication vector.

[0082] In a further embodiment, constructing a first sequence according to the indicator vector includes:

[0083] After arranging the position indexes corresponding to the virtual representative time slots in the indication vector in ascending order, we obtain:

[0084] W={w 1 ,w 2 ,w 3 ,…,w m}

[0085] In the formula, w 1 ,w 2 ,w 3 ,…,w m is the position index corresponding to the virtual representative time slots arranged in ascending order;

[0086] Let w 0 =0, the first sequence is:

[0087] ΔD={Δd 1 ,Δd 2 ,Δd 3 ,…,Δd m}

[0088] Δd y =w y -w y-1

[0089] In the formula, Δd y Indicates w y and w y-1 The difference.

[0090] In a further embodiment, a combined signal is received by the reader based on the result of the hash operation of all tags and the first sequence:

[0091] Each tag holds a register that is initially 0. Each time it receives the value of the incremental sequence broadcast by the reader, the register is added with the corresponding value, and it is determined whether the value in the register is the same as the previously recorded hash result. If they are equal, the tag information is transmitted to the reader. If they are not equal, it waits for a period of time until the next update.

[0092] The transmitted tag information constitutes a combined signal and is received by the reader.

[0093] In a further embodiment, the transmitted tag information constitutes a combined signal received by a reader, comprising:

[0094] The transmitted tag information is received by the reader according to the Manchester code to form a combined signal.

[0095] In this embodiment, the Manchester encoding principle is as follows: Figure 2 As shown in , the main motivation for using Manchester coding is that it can decode the last signal when receiving a combined signal and knowing the other signals in a combined signal. Figure 2 As shown, in Manchester encoding, "1" and "0" represent high-to-low and low-to-high signal transitions, respectively. Tags A, B, and C store three 7-bit object information: "1010000", "1001001", and "1001000". If they reply to the reader in the same time slot using Manchester encoding, the combined signal received by the reader is "10XX00X", where "X" represents a collision bit. Only the different bits in the responses of the three tags will cause a collision bit to appear in the combined signal, and the appearance of the collision bit is equivalent to the difference between the responses of the three tags. Therefore, if the reader knows any two of the three tags, the response of another tag can be extracted from the combined signal through Manchester encoding.

[0096] In a further embodiment, according to the virtual representative time slots of the target objects and the execution frame EF, the tag ID and the object information contained in the signal of each time slot in the execution frame EF are determined, such as Figure 3 As shown, including:

[0097] For homogeneous time slots, the corresponding tag ID and the object information to which it belongs are directly obtained;

[0098] For heterogeneous time slots, based on the known tag IDs and the object information they belong to, the unknown tag IDs and the object information they belong to are obtained in sequence until the object information of all target objects is obtained.

[0099] In a specific embodiment, Figure 3 As shown in the figure, there are five target objects. In order to collect information about the five target objects, time slots 2, 4, 6, 10, and 13 can be selected as representative time slots. Since time slot 4 is a singleton time slot, the reader can directly collect information about object A in the time slot. According to the characteristics of Manchester encoding, when receiving a combined signal, the combined signal can be decoded by a known signal. The reader can further extract information about object B by stripping off the information about object A that has been obtained in time slot 2. Similarly, the information about C and D can be extracted in the order shown by the arrows in the figure.

[0100] In a further embodiment, all the tags also include a flag bit, which is initialized to 1. If the information of the object to which the tag belongs has been received by the reader, it is updated to 0 and no longer participates in the information collection process. The reader will only perform hash calculations on the tag ID with a flag bit of 1, and only tags with a flag bit of 1 will respond to the reader's commands.

[0101] Therefore, if the flag bit of the tags on all target objects is 0, the whole process ends; otherwise, the tags with the flag bit 1 continue to repeat the information reading.

[0102] This embodiment also provides a specific embodiment for illustrating the method of this embodiment, specifically:

[0103] See also Figure 4 , Figure 5 , Figure 6 In the specific example, objects A, B, C, D, and F are target objects, and object E is not a target object. Each object has two tags. When collecting target object information, this implementation includes the following process:

[0104] Step D1: Set f=17 to create a bit vector VF of length f, obtain the IDs of all tags and the information of the objects they belong to, and classify the tags into target tags and non-target tags according to whether the objects are target objects. Obtain two seeds of the uniform hash function in a random manner.

[0105] Step D2: Using the above seed and uniform hash function H(·), perform hash operation on each tag ID and map it to two repeatable virtual time slots of VF.

[0106] Step D3: Figure 4 As shown, for any virtual time slot, if at least one non-target tag is mapped to it, it is marked as an eliminated virtual time slot, including virtual time slots 10, 12, 15, and 17; while virtual time slots 3, 4, and 11 are unmarked homogeneous time slots. Since virtual time slots 3 and 4 are homogeneous time slots that only contain the tag of object A, virtual time slot 4 is randomly selected as the virtual representative time slot of object A, then virtual time slot 3 is marked as an eliminated virtual time slot, and virtual time slot 11 is marked as the virtual representative time slot of object D. Virtual time slots 2 and 13 are unmarked 2-heterogeneous virtual time slots. Virtual time slot 2 can be used as the virtual representative time slot of object B, and virtual time slot 13 can be used as the virtual representative time slot of object F. And 3-heterogeneous virtual time slot 6 can be used as the virtual representative time slot of object C, and virtual time slot 10 is eliminated.

[0107] Step D4: The reader constructs an indicator vector IV by setting the values ​​of virtual representative time slots 2, 4, 6, 11, and 13 to "1" and all other virtual time slots (including the eliminated virtual time slots) to "0".

[0108] Step D5: The reader arranges the indices of the virtual representative time slots in step D4 (i.e., the indices with the value "1" in IV) in ascending order to obtain the index sequence {2, 4, 6, 11, 13}, and then constructs an incremental sequence {2, 2, 2, 5, 2} based on the difference between adjacent indexes.

[0109] Step D6: The reader broadcasts the IV length f, 2 seeds, uniform hash function and other parameters, and then broadcasts the values ​​in the incremental sequence in turn. Figure 5 As shown, the tag performs the same hash process as D2 according to the above-mentioned seed and uniform hash function and records the result. Each tag holds a register that is initially 0. Each time it receives the value of the incremental sequence broadcast by the reader, the register is added with the corresponding value, and it is determined whether the value in the register is the same as the previously recorded hash result. When the value of the register is 2, tags 1, 3, and 4 transmit information; when the value of the register is 4, tag 2 transmits information; when the value of the register is 6, tags 3, 4, 5, 6, and 7 transmit information; when the value of the register is 11, tag 7 transmits information; when the value of the register is 13, tags 8 and 11 transmit information. The tag information transmitted at the same time constitutes a combined signal according to Manchester coding and is received by the reader.

[0110] Step D7: The reader sorts the information from the tags by reception time and constructs the execution frame EF

[0111] Step D8: Figure 6 As shown, according to the process of steps D2 to D3, determine which tag information and the objects to which the signal of each time slot in EF contains; for example, time slot 1 contains the information of objects A and B, and time slot 2 contains the information of object A. Since time slots 2 and time slot 4 in EF are singleton time slots, the reader can easily decode their response signals, thereby collecting the information of objects A and D. Since the tag response signals in the same time slot are synchronously transmitted using Manchester coding, the reader can strip the information of objects A and D from the response signals recorded in time slots 1, 3, and 5. In this case, time slots 1 and 5 can be regarded as homogeneous time slots, while time slot 3 can be regarded as 2-heterogeneous time slots. Therefore, the reader can extract the information of objects B and F from the response signals of time slots 1 and 5. Similarly, by stripping the information of object B from the signal recorded in time slot 3, the information of object C can also be extracted. So far, the information of all five target objects has been successfully collected.

[0112] Step D9: Update the flags of all tags on A, B, C, D, and F to 0. Since the tag flags of all target objects are 0, this step ends.

[0113] Next, this embodiment will show the simulation performance comparison between the method of the present invention (hereinafter referred to as BCP algorithm) and the prior art under different numbers of objects and different numbers of tag information bits:

[0114] By default, the total number of objects is 2. 14 , the number of target objects accounts for 90% of the total number of objects, the number of tags on each object is 3, the number of tag information bits is 16, and the number of seeds is 4;

[0115] like Figure 7 As shown in (a), in this implementation case, the execution time increases linearly with the number of objects. BCP performs best, IPP performs similarly to BCP, slightly worse than BCP, followed by MIC, and CPP is the worst.

[0116] like Figure 7 As shown in (b), in this implementation case, as the number of tag information bits increases from 1 to 32, the execution time of each algorithm increases rapidly. The comparison result is similar to that in 7(a), which is BCP>IPP>MIC>>CPP.

[0117] In general, this implementation case shows the following conclusions: (1) The number of objects and the number of tag information bits have a linear effect on the execution time of each algorithm; (2) The BCP algorithm outperforms other algorithms in terms of time overhead, showing a significant improvement.

[0118] The same or similar reference numerals correspond to the same or similar components;

[0119] The terms used in the drawings to describe positional relationships are only used for illustrative purposes and should not be construed as limiting this patent;

[0120] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for collecting information of a large multi-tag RFID system based on collision peeling, characterized in that: include: Obtain the IDs of all tags in the multi-tag RFID system and the object information they belong to. If the object is a target object, all tags under the object are classified as target tags. If the object is not a target object, all tags under the object are classified as non-target tags. Using several seeds of a uniform hash function obtained randomly and a uniform hash function, the IDs of all tags are hashed and mapped to several repeatable virtual time slots of a preset bit vector VF; According to the label classification results, the virtual representative time slot of each target object is obtained from the mapped multiple repeatable virtual time slots; constructing an indication vector according to the preset bit vector VF and the virtual representative time slot of each target object; Constructing a first sequence according to the indicator vector; The reader broadcasts the length of the bit vector VF, several seeds, and a uniform hash function to all tags; Each tag performs a hash operation according to the plurality of seeds and a uniform hash function; A combined signal is formed according to the results of hash operations of all tags and the first sequence and is received by the reader; The reader sorts the combined signals according to the receiving time and constructs an execution frame EF; According to the virtual representative time slots of the target objects and the execution frame EF, the tag ID and the object information contained in the signal of each time slot in the execution frame EF are determined.

2. The information collection method for a large multi-tag RFID system based on collision peeling according to claim 1 is characterized in that: The length of the preset bit vector VF is f, and f is not less than the number of target objects. Each bit of the preset bit vector VF is called a virtual time slot.

3. The information collection method of a large multi-tag RFID system based on collision peeling according to claim 2 is characterized in that: Using several seeds of the uniform hash function obtained randomly and the uniform hash function, the IDs of all tags are hashed and mapped to several repeatable virtual time slots of the preset bit vector VF, including: h i =H(ID i ,s r )mod f In the formula, h i is the ith tag ID i The mapping result, H(·) is a uniform hash function, s r For the rth seed, 1≤r≤k, k different uniform hash functions are simulated by using k different seeds.

4. The information collection method of a large multi-tag RFID system based on collision peeling according to claim 1 is characterized in that: According to the label classification results, the virtual representative time slots of each target object are obtained from the mapped repeatable virtual time slots, including: Among the multiple repeated virtual time slots after mapping, at least one virtual time slot to which a non-target tag is mapped is marked as a virtual time slot to be eliminated; Then, from the remaining unmarked virtual time slots, a random selection is made from the homogeneous virtual time slots mapped to the tag ID corresponding to each target object as the virtual representative time slot of the current target object, and the unselected homogeneous time slots are marked as eliminated virtual time slots; for heterogeneous virtual time slots, if there is only one target object that does not have a virtual representative time slot, then the virtual time slot is marked as the virtual representative time slot of the target object, and the rest are marked as eliminated virtual time slots, until all virtual time slots mapped to tags in the bit vector VF are marked or all target objects have virtual representative time slots; The homogeneous virtual time slot is a time slot including only one object information, and the heterogeneous virtual time slot is a time slot including multiple object information.

5. The information collection method of a large multi-tag RFID system based on collision peeling according to claim 4 is characterized in that: Constructing an indication vector according to the preset bit vector VF and the virtual representative time slot of each target object, including: The length of the indication vector is equal to the length of the preset bit vector VF. The indication vector is 1 at the position corresponding to the virtual representative time slot of each target object and 0 at other positions, thereby obtaining the indication vector.

6. The information collection method of a large multi-tag RFID system based on collision peeling according to claim 5 is characterized in that: According to the indicator vector, a first sequence is constructed, including: After arranging the position indexes corresponding to the virtual representative time slots in the indication vector in ascending order, we obtain: <h2 style=";text-align:left;direction:ltr">W = {w1,w2,w3,…,w<h2 style=";text-align:left;direction:ltr"> m <h2 style=";text-align:left;direction:ltr">} Where w1, w2, w3, …, w m is the position index corresponding to the virtual representative time slots arranged in ascending order; Let w0=0, the first sequence is: ΔD={Δd1,Δd2,Δd3,…,Δd m } Δd y =in y -In y-1 In the formula, Δd y Indicates w y and w y-1 The difference.

7. The information collection method of a large multi-tag RFID system based on collision peeling according to claim 6 is characterized in that: The combined signal is received by the reader based on the results of the hash operations of all tags and the first sequence: Each tag holds a register that is initially 0. Each time it receives the value of the incremental sequence broadcast by the reader, the register is added with the corresponding value, and it is determined whether the value in the register is the same as the previously recorded hash result. If they are equal, the tag information is transmitted to the reader. If they are not equal, it waits for a period of time until the next update. The transmitted tag information constitutes a combined signal and is received by the reader.

8. The information collection method of a large multi-tag RFID system based on collision peeling according to claim 7 is characterized in that: The transmitted tag information constitutes a combined signal received by the reader, including: The transmitted tag information is received by the reader according to the Manchester code to form a combined signal.

9. The method for collecting information of a large multi-tag RFID system based on collision peeling according to claim 7 is characterized in that: According to the virtual representative time slots of the target objects and the execution frame EF, determining the tag ID and the object information contained in the signal of each time slot in the execution frame EF, including: For homogeneous time slots, the corresponding tag ID and the object information to which it belongs are directly obtained; For heterogeneous time slots, based on the known tag IDs and the object information they belong to, the unknown tag IDs and the object information they belong to are obtained in sequence until the object information of all target objects is obtained.

10. The method for collecting information of a large multi-tag RFID system based on collision peeling according to any one of claims 1 to 9, characterized in that: All the tags also include a flag bit, which is initialized to 1. If the information of the object to which the tag belongs has been received by the reader, it will be updated to 0 and will no longer participate in the information collection process. The reader will only perform hash calculations on the tag ID with a flag bit of 1, and only tags with a flag bit of 1 will respond to the reader's commands.

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