A radio frequency identification network planning modeling method based on multi-stage cascading and supply chain hierarchy

Abstract

A new Radio Frequency Identification (RFID) Network Planning (RNP) modeling method based on multi-stage cascading and supply chain hierarchy is disclosed, which comprises the following steps: firstly, according to the connectivity between tags and readers, between adjacent readers, and between readers and terminals, a new RNP communication link equation with multi-stage cascading characteristics is obtained; secondly, the new RNP problem is described based on the supply chain structure, the roles of the readers are classified, and three new link connection modes are proposed; and then, an RNP optimization target model is constructed around the positioning accuracy, tag coverage and forwarding hop number. The new RNP modeling method designed by the application has certain guiding significance for the deployment of readers and the selection of links in large RNP problems.

Description

Technical Field

[0001] This invention belongs to the field of Internet of Things (IoT) and relates to a modeling method for multi-level cascaded and supply chain-hierarchical Radio Frequency Identification (RFID) network planning (RNP). Background Technology

[0002] With the rapid rise of the Internet of Things (IoT) industry in recent years, new-generation information technologies have shone brightly across various industries, including radio frequency identification (RFID), sensor technology, embedded system technology, and current research hotspots such as cloud computing and mass computing. Among these, RFID technology, playing a core role in IoT applications, has been particularly prominent in industry, scientific research, and commerce. However, practical RFID applications typically require large-scale deployment of readers and antennas to achieve the identification and monitoring of massive numbers of tags. Therefore, how to arrange the positions of the readers and rationally deploy the number of readers are key issues that RFID applications need to address, and these issues are also known as the RNP problem.

[0003] Current RNP modeling methods are mainly based on single-level and single-layer approaches, which are insufficient to meet the needs of complex multi-level cascaded and supply chain networks in RFID systems. To address this issue, this invention proposes a multi-level cascaded and supply chain-hierarchical RNP modeling method. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-level cascaded and supply chain-hierarchical RNP modeling method to address the need for identification and monitoring of massive numbers of tags and to rationally arrange the location and number of readers. The modeling scheme adopted in this invention establishes transmission link functions between tags and readers, between adjacent readers, and between readers and application terminals based on the connectivity between multiple readers. This maps tags, readers, and application terminals in the RFID system to various parts of the supply chain, classifies readers by role, proposes three link connection methods based on reader role classification, obtains corresponding matrix expressions, and then proposes three novel objective functions to jointly construct the RNP problem model. Specifically, the following steps are included:

[0005] Step 1: Construct an RNP network scenario based on the communication between tags and readers, between readers, and between readers and terminals. The RNP modeling method includes two technical points: first, deriving the RNP communication link equation with multi-level cascading characteristics; second, describing RNP based on the supply chain hierarchy and modeling the relationship between objects in the cascading RNP network.

[0006] Step 2: To derive the communication link equation in the RNP scenario, it is assumed that the tag and reader, adjacent readers of the same type, and readers and terminals all use uplink and downlink for communication, that is, there are bidirectional information transmission links.

[0007] Step 3: To derive the maximum communication distance between the tag and the reader, define d. forward d represents the forward link transmission distance. reverse To determine the backward link transmission distance, the maximum communication distance from the tag to the reader is calculated as D1, i.e., when d forward <d reverse hour, When d forward >d reverse hour, Where λ is the wavelength, τ is the modulation efficiency, and μ T For transmission efficiency, The threshold for the reader's transmit power. This is the power threshold received by the passive tag in the forward link. The power threshold received by the backward link reader. G is the transmission power threshold for the tag. reader and G tag These are the gains of the reader antenna and the tag antenna, respectively;

[0008] Step 4: Considering that the uplink and downlink communication distances between readers are equal, solve for the maximum communication distance between adjacent readers, and define reader R. I and R J The coordinates are (x) I y I ) and (x J y J The Euclidean distance between the two is With Reader R I For the transmitter, reader R J For the receiver, the reader R is derived based on Friis's formula. I With Reader R J The maximum communication distance between them is in, For Reader R J Antenna gain, For Reader R I Antenna gain, For Reader R J The transmission power, For Reader R I The received power threshold;

[0009] Step 5: To obtain the maximum transmission distance between the reader and the terminal, define the reader R. H The coordinates are (x H y H The coordinates of application terminal A are (x...). A y A The Euclidean distance between the two is When application terminal A sends a message to reader R H When sending a message, the reader R is derived based on Friis's formula. H Maximum transmission distance of downlink communication with terminal A When reader R H When sending information to application terminal A, reader R H Maximum transmission distance of uplink communication with terminal A Among them, G A For the antenna gain of application terminal A, For Reader R H Antenna gain, P A t and Application terminal A and reader R are respectively. H The transmission power, and Application terminal A and reader R are respectively. H The received power threshold;

[0010] Step 6: Based on the hierarchical classification concept in supply chain network planning and design, and in accordance with the horizontal dimension in the supply chain hierarchy, the RFID system is divided into three levels: the first level is passive tags, the second level is readers, and the third level is application terminals. Three links are defined for tags to reach the terminal via readers: Link 1 is when the tag reaches the terminal via a single reader, Link 2 is when the tag reaches the terminal via cascaded communication between two readers, and Link 3 is when the tag reaches the terminal via cascaded communication between three readers.

[0011] Step 7: To classify the readers in the link connection methods of Step 6, define the number of tags in the RNP scenario as I, the number of readers as M, and the number of terminals as K. The corresponding tag group set, reader group set, and terminal group set are IT = {IT1, IT2, ..., IT...} I}, IR={IR1, IR2,..., IR M}, IS={IS1, IS2,..., IS K}, among which, IT i Let IR be the identifier ID of the i-th label. m IS is the identifier ID of the m-th reader. kLet i be the identifier ID of the k-th terminal, and i ∈ [1, I], m ∈ [1, M], k ∈ [1, K];

[0012] Step 8: Redefine the functional role of readers in the RFID system by introducing the basic characteristics of the supply chain. Classify readers based on the distance between the reader and the tag, the distance between the reader and the terminal, and the role of the reader in its respective link. First, divide readers into two categories: data acquisition readers and data upload readers. Define the functions used to read RFID tag data and satisfy the discrimination formula. The device is a data acquisition reader. Based on the positional relationship between the tag and the reader, it can obtain the data that can be acquired from the i-th tag. i Collection of readers for communication Among them, L i For the use of IT tags i The number of data acquisition readers that communicate directly. For the i-th label IT i The l-th collector reader, l∈[1,L] i ], For the label IT i and collection reader The distance between the tag and the reader is D1, which is the maximum communication distance between them. When the distance between the tag and the reader is less than D1, they can establish communication, upload RFID tag data to the upper-level system, and satisfy the discrimination formula. The device is defined as an upload reader. Based on the location relationship between the terminal and the reader, it can obtain the information that can communicate with the k-th terminal via IS. k Collection of readers for communication Among them, O k To connect with the terminal IS k The number of upload readers communicating directly. For the i-th label IT i Related to and corresponding to the k-th terminal IS k The o-th uploader, o∈[1, O] k ], Uploaded Reader and terminal IS k The distance between them, D3 is the maximum communication distance between the reader and the terminal. When the distance between the reader and the terminal is less than D3, they can establish communication.

[0013] Step 9: To facilitate the analysis of link conditions in the RNP scenario, based on the reader classification results in Step 8, readers are further divided into four types: direct-connection readers, uplink readers, jump-connection readers, and jump-jump readers. A device that satisfies both the definition of a data acquisition reader and the definition of an uplink reader is defined as a direct-connection reader, i.e., it must satisfy the discrimination formula. and The collection of readers is Among them, A i For the use of IT tags i The number of directly connected readers in the communication. For the i-th label IT i The a-th directly connected reader, a∈[1, A i ], Represents a direct-connect reader and the IT tag i The distance between them Represents a direct-connect reader and terminal IS k The distance between them, when the direct-connect reader and the tag and terminal respectively satisfy the discrimination formula, can establish communication and form the working path of link 1 in step 6. The device that meets the definition of the acquisition reader but not the definition of the upload reader is defined as the uplink reader, that is, it must meet the discrimination formula. and The collection of readers is Among them, U i For the use of IT tags i The number of connected readers in the communication. For the i-th label IT i The u-th uplink reader, u∈[1, U i ], Representing the IT label i Connect to the reader The distance between them Represents the connected reader and upload reader The distance between them Represents the connected reader and terminal IS k The distance between them, when the discriminant formula is satisfied between the uplink reader and the tag, upload reader, and terminal respectively, communication can be established and the working path of link 2 in step 6 can be formed. The acquisition reader in link 3 is defined as a jump reader. The discriminant formula and functions of this reader are the same as those of the uplink reader. The set of jump readers is as follows: Among them, B i For the use of IT tags i The number of jump readers in the communication. For the i-th label IT i The b-th jump reader, b∈[1, B] iA jump reader is defined as a device that can neither communicate directly with the tag nor directly with the terminal, but can still transmit tag information to the terminal through a data acquisition reader and an upload reader. This means it must satisfy the discrimination formula. and This type of reader is a collection of Among them, Z i To the number of readers that can be redirected, For the i-th label IT i The z-th jump reader, z∈[1, Z] i ], Representing the IT label i and jump reader The distance between them Represents a jump-connected reader and jump reader The distance between them Represents a jump reader and upload reader The distance between them Represents a jump reader and terminal IS k The distance between them is such that when the jump reader satisfies the discrimination formula with the tag, the jump reader, the upload reader, and the terminal respectively, communication can be established and the working path of link 3 in step 6 can be formed. Therefore, the three links in step 6 can be simplified as follows: Link 1: Tag - Direct Reader - Terminal; Link 2: Tag - Uplink Reader - Upload Reader - Terminal; Link 3: Tag - Jump Reader - Jump Reader - Upload Reader - Terminal. Thus, based on the naming rules and classification criteria of each reader, a matrix expression of the number of links traversed by the tag and the types of readers used can be obtained.

[0014] Step 10: Model the RNP problem, selecting the option with maximum label coverage, minimum localization error, and a certain label IT. i The output is a set of reader locations and excitations with the minimum number of forwarding hops along the traversed link, in mathematical form as follows: Where Ω = [(x1, y1), (x2, y2), ..., (x... y1)], (x2, y2), ..., (x... y1) M y M )], F=ω1f1+ω2f2+ω3f3, Ω is a candidate solution of RNP, and the position coordinates of the m-th reader antenna are (x m y m The objective function F is a linear weighted sum of three sub-functions: f1 is the proportion of labels not covered, f2 is the positioning accuracy error, f3 is the normalized forwarding hop count, and ω1, ω2, and ω3 are the weight coefficients.

[0015] Step 11: To maximize tag coverage, define the following based on the link status between readers: Indicates the connectivity of the link, if but like but Among them, dist(R) x R y () represents the Euclidean distance between the x-th reader and the y-th reader, where x, y ∈ [1, M]. This represents the maximum communication distance between the x-th reader and the y-th reader, defined based on the link status between the reader and the terminal. Perform a judgment, if but like but in, Indicates the uploader With terminal IS k European distance, Let x represent the maximum communication distance between the x-th reader and the k-th terminal, and define the availability of the m-th reader to the i-th tag as... The location of the i-th tag is considered successful if it is recognized by three or more readers. The location of the i-th tag can be determined by S. i It means that if Then S i =1, if Then S i =0, f1 in step 10 is defined as a non-covering form, that is

[0016] Step 12: To achieve accurate assessment of positioning accuracy, the Geometric Dilution of Precision (GDOP) factor based on the lower bound of Cramer-Rao is used to evaluate the impact of reader deployment on positioning accuracy. Define... The coordinates of the l-th reader are (x) l y l (l=1,2,...,L;L≥3), the relative angle between the reader and the target tag is α. l (l = 1, 2, ..., L; L ≥ 3), the distance from the l-th reader to the target tag is d. l Then the Jacobian matrix based on the Time of Arrival (TOA) is expressed as: The positional relationship between the target tag and the reader is obtained by calculating the... and In the TOA positioning system, H TMultiplying by H yields Tr(H) T If H) = L, then the expression for GDOP can be represented as: In step 10, f2 is defined as the positioning accuracy error, i.e. Where S i This indicates the locatability of the tag mentioned in step 11;

[0017] Step 13: To achieve long-distance RFID transmission and reduce reader hop count, the number of tag hops the reader identifies in the entire RFID system is expressed as... Among them, i n For the label IT i The number of times the information passes through the nth link, w n Let f3 be the reader forwarding hop count for the nth link. Based on the three proposed link structures, the value of n will vary from 1 to 3. In step 10, f3 is defined as the normalized forwarding hop count, i.e.

[0018] It should be noted that, based on the naming rules and classifications of various readers, the process of obtaining the matrix expression for the number of links traversed by the tag and the types of readers used in step 9 is as follows:

[0019] Step 1: After naming and categorizing, different communication links are formed between the readers, tags, and terminals. Based on the differences in the number and location of readers in each link, the tag communication link connection methods are mainly divided into three types, with tag IT as the main component. i For example, suppose this label has multiple links to the application terminal IS. k The links, all of which can correspond to three link connection methods, are labeled IT. i The link from the reader to the terminal and the type of reader used can be determined by... This indicates that each column in the matrix represents a different type of reader, from the leftmost to the rightmost column: direct-connect reader, uplink reader, jump-connect reader, jump-to-reader, and upload reader. Each tag is IT. i There can be multiple readers of different types connected to it, from the first row to the last row of the matrix, representing the tag IT. i The number of links that transmit information to the application terminal;

[0020] Step 2: To select the most suitable link in the information transmission process of the RFID system, an RNP problem model is constructed based on the three novel objective functions proposed above. For the second passive tag, when there is only one terminal device, there are three transmission links between the tag and the application terminal. The first link is via a direct connection to the reader. Upon reaching the terminal, the second step is via an upstream reader. Upload Reader Upon reaching the terminal, the third step is via a jump-connected reader. Jump to Reader Upload Reader Upon reaching the terminal, all links can be accessed. The matrix representation of .

[0021] This invention provides a multi-level cascaded and supply chain hierarchical RNP modeling method. The method first derives the link equations for communication between tags and readers, between adjacent readers, and between readers and terminals in an RFID system. Then, it maps each part of the RNP to the parts of the supply chain network structure and proposes an RNP scenario framework based on the hierarchical characteristics of the supply chain. Based on the limitations of transmission distance between readers and their roles, it classifies readers into roles and proposes three novel link connection methods based on these roles, obtaining the corresponding matrix expressions. Finally, it proposes three novel objective functions to jointly construct the RNP problem model, providing guidance for reader deployment and link selection in large and complex network structures. Attached image description:

[0022] Figure 1 This is a system framework diagram of the present invention;

[0023] Figure 2 This is a schematic diagram of RNP link transmission according to the present invention;

[0024] Figure 3 This is a schematic diagram of the link between the tag and the reader of this invention;

[0025] Figure 4 This is a schematic diagram of the link between the readers of this invention;

[0026] Figure 5 This is a schematic diagram of the link between the reader and the terminal of this invention;

[0027] Figure 6 This is a schematic diagram of RNP based on the hierarchical structure of the supply chain in this invention;

[0028] Figure 7 This is a schematic diagram of the reader for collecting data according to the present invention;

[0029] Figure 8 This is a schematic diagram of the upload reader of the present invention;

[0030] Figure 9 This is a schematic diagram of the direct-connect reader of the present invention;

[0031] Figure 10 This is a schematic diagram of the reader connected to the present invention;

[0032] Figure 11 This is a schematic diagram of the jump reader of the present invention;

[0033] Figure 12 This is a schematic diagram illustrating the classification of readers in an RNP scenario, using a certain tag as an example. Detailed implementation method:

[0034] The purpose of this invention is to provide a multi-level cascaded and supply chain-hierarchical RNP modeling method. This method first derives the link equations for communication between tags and readers, between adjacent readers, and between readers and terminals in an RFID system. Then, it maps each part of the RNP to the parts of the supply chain network structure, and proposes an RNP scenario framework based on the hierarchical characteristics of the supply chain. Based on the limitations of transmission distance between readers and their roles, it classifies readers by role and proposes three novel link connection methods based on these classifications, obtaining the corresponding matrix expressions. Finally, it proposes three novel objective functions to jointly construct the RNP problem model, providing guidance for reader deployment and link selection in large-scale RNP problems.

[0035] The following is in conjunction with the appendix Figure 1 Appendix Figure 2 Appendix Figure 3 Appendix Figure 4 Appendix Figure 5 Appendix Figure 6 Appendix Figure 7 Appendix Figure 8 Appendix Figure 9 Appendix Figure 10 and appendix Figure 11 The embodiments of the present invention will be described in further detail below.

[0036] This invention is based on the design concept of multi-level cascading and supply chain hierarchy, and is designed based on the characteristics and needs of RFID systems in practical applications.

[0037] The system framework of this invention is attached. Figure 1 As shown, based on the connectivity between readers and between readers and terminals as the basis for solving the RNP problem, three link connection methods are proposed to provide a basis for selecting communication links for long-distance tag information transmission. The RNP problem is described based on the supply chain structure. The relationship between objects in the RNP network is reasonably modeled by using the hierarchical characteristics of the supply chain and the role classification of each reader is performed. Then, the RNP problem is mathematically described, and a global optimization problem model of RNP is constructed.

[0038] As attached Figure 2As shown, the communication of RFID systems exhibits multi-level cascading characteristics. Therefore, when planning RNP in a scenario, it is necessary to consider not only the transmission link between the tag and the reader, but also the transmission link between readers and between readers and terminals. Thus, when planning RNP in a scenario, the communication link mainly includes two parts: 1) the link from the tag to the reader; 2) the link from the reader to the terminal.

[0039] The communication link equation is derived based on the characteristics of the communication link, as shown in the appendix. Figure 3 As shown, to derive the maximum communication distance between the tag and the reader, d is defined. forward d represents the uplink transmission distance. reverse To find the downlink transmission distance, the maximum communication distance from the tag to the reader is D1, which is the distance when d forward <d reverse hour, When d forward >d reverse hour, Where λ is the wavelength, τ is the modulation efficiency, and μ T For transmission efficiency, The threshold for the reader's transmit power. This is the power threshold received by the passive tag in the forward link. The power threshold received by the backward link reader. G is the transmission power threshold for the tag. reader and G tag These are the gains of the reader antenna and the tag antenna, respectively.

[0040] As attached Figure 4 As shown, adjacent readers of the same type communicate via downlink and uplink. Assuming the communication distances of the uplink and downlink are equal, the maximum communication distance between adjacent readers is calculated. Reader R is defined as follows. I and R J The coordinates are (x) I y I ) and (x J y J The Euclidean distance between the two is With Reader R I For the transmitter, reader R J For the receiver, the reader R is derived based on Friis's formula. I With Reader R J The maximum communication distance between them is in, For Reader R J Antenna gain, For Reader R I Antenna gain, For Reader R J The transmission power, For Reader R I The received power threshold.

[0041] As attached Figure 5 As shown, there is a bidirectional information transmission link between the reader and the terminal. The reader R is defined as follows: H The coordinates are (x H y H The coordinates of application terminal A are (x...). A y A The Euclidean distance between the two is When application terminal A sends a message to reader R H When sending a message, the reader R is derived based on Friis's formula. H Maximum transmission distance of downlink communication with terminal A When reader R H When sending information to application terminal A, reader R H Maximum transmission distance of uplink communication with terminal A Among them, G A For the antenna gain of application terminal A, For Reader R H Antenna gain, and Application terminal A and reader R are respectively. H The transmission power, and Application terminal A and reader R are respectively. H The received power threshold.

[0042] The internal members of supply chains and RFID systems share certain similarities in their roles. Therefore, by incorporating the fundamental characteristics of supply chains and referencing the hierarchical classification concept in supply chain network planning and design, an RNP model based on the hierarchy of the supply chain is derived, as shown in the appendix. Figure 6 As shown, this model, in accordance with the horizontal dimension of the supply chain hierarchy, divides the RFID system into three levels: the first level is passive tags, the second level is readers, and the third level is application terminals. The colored lines in the figure represent different transmission links. Taking passive tag 2 as an example, there are three links from the tag to the terminal via the reader: link 1 is defined as the tag information directly reaching the application terminal via reader 1; link 2 is defined as the tag information reaching the remote terminal via readers 2 and 4; and link 3 is defined as the tag information reaching the remote terminal via readers 3, 5, and 6.

[0043] By analyzing the information transmission links of individual tags, readers in the second layer are classified according to their roles. This classification is based on the distance between the reader and the tag, the distance between the reader and the terminal, and the role the reader plays in each link, as shown in the appendix. Figure 7 ~Attached Figure 11 As shown, the categorized readers are as follows: collection reader, upload reader, direct connection reader, uplink reader, jump connection reader, and jump reader.

[0044] As attached Figure 7 As shown, a formula is defined for reading RFID tag data and satisfying the discrimination formula. The device is a data acquisition reader. Based on the positional relationship between the tag and the reader, it can obtain the data that can be acquired from the i-th tag. i Collection of readers for communication Among them, L i For the use of IT tags i The number of readers communicating directly. For the i-th label IT i The first collector reader, l∈[1,L] i ], For the label IT i and collection reader The distance between the tag and the reader is D1, which is the maximum communication distance between the tag and the reader. When the distance between the tag and the reader is less than D1, they can establish communication.

[0045] As attached Figure 8 As shown, the RFID tag data is uploaded to the upper-layer system and satisfies the discrimination formula. The device is defined as an upload reader. Based on the location relationship between the terminal and the reader, it can obtain the information that can communicate with the k-th terminal via IS. k Collection of readers for communication Among them, O k To connect with the terminal IS k The number of readers communicating directly. For the i-th label IT i Related to and corresponding to the k-th terminal IS k The o-th uploader, o∈[1, O] k ], Uploaded Reader and terminal IS k The distance between them is D3, which is the maximum communication distance between the reader and the terminal. When the distance between the reader and the terminal is less than D3, they can establish communication.

[0046] As attached Figure 9As shown, a device that satisfies both the definition of a data acquisition reader and the definition of an upload reader is defined as a directly connected reader, i.e., it must satisfy the discrimination formula. and The collection of readers is Among them, A i For the use of IT tags i The number of directly connected readers in the communication. For the i-th label IT i The a-th directly connected reader, a∈[1, A i ], Represents a direct-connect reader and the IT tag i The distance between them Represents a direct-connect reader and terminal IS k The distance between them is such that when the direct-connect reader satisfies the discrimination formula with the tag and the terminal respectively, communication can be established and a working path of link 1 can be formed.

[0047] As attached Figure 10 As shown, a device that meets the definition of a data acquisition reader but not the definition of an upload reader is defined as an uplink reader, i.e., it must satisfy the discrimination formula. and The collection of readers is Among them, U i For the use of IT tags i The number of connected readers in the communication. For the i-th label IT i The u-th uplink reader, u∈[1, U i ], Representing the IT label i Connect to the reader The distance between them Represents the connected reader and upload reader The distance between them Represents the connected reader and terminal IS k The distance between them, when the discriminant formula is satisfied between the uplink reader and the tag, the uplink reader, and the terminal respectively, allows communication to be established and a working path of link 2 to be formed.

[0048] To distinguish between different communication links, the acquisition reader in link 3 is defined as a jump-connection reader. The discrimination formula and functions of this reader are similar to those of the uplink reader; the discrimination formula is the same. The set of jump-connection readers is as follows: Among them, B i For the use of IT tags i The number of jump readers in the communication. For the i-th label IT i The b-th jump reader, b∈[1, B] i ].

[0049] As attached Figure 11 As shown, a device that cannot communicate directly with the tag or the terminal, but can still transmit tag information to the terminal through a data acquisition reader and an upload reader, is defined as a jump reader, which must satisfy the discrimination formula. and This type of reader is a collection of Among them, Z i For the use of IT tags i The number of jump readers in the communication. For the i-th label IT i The z-th jump reader, z∈[1, Z] i ], Representing the IT label i and jump reader The distance between them Represents a jump-connected reader and jump reader The distance between them Represents a jump reader and upload reader The distance between them Represents a jump reader and terminal IS k The distance between them, when the jump reader and the tag, jump link reader, upload reader and terminal satisfy the discrimination formula respectively, can establish communication and form the working path of link 3.

[0050] In RNP scenarios, multiple communication links exist between tags and terminals. Tag information can reach the application terminal through multiple hops via two or more readers. Based on the reader classification method described above, the tag information can be simplified. Figure 6 The three types of links are shown in the appendix. Figure 12 As shown, the three links can be simplified as follows: Link 1: Tag – Direct Connected Reader – Terminal; Link 2: Tag – Uplinked Reader – Uploaded Reader – Terminal; Link 3: Tag – Jump Connected Reader – Jump Reader – Uploaded Reader – Terminal. Therefore, for the second passive tag, when only one terminal device exists, there are three transmission links between the tag and the application terminal. The first link is via the direct connected reader. Upon reaching the terminal, the second step is via an upstream reader. Upload Reader Upon reaching the terminal, the third step is via a jump-connected reader. Jump to Reader Upload Reader Upon reaching the terminal, all links can be accessed. The matrix representation of .

Claims

1. A radio frequency identification (RFID) network planning and modeling method based on multi-level cascading and supply chain hierarchy, characterized in that, The specific steps are as follows: Step 1: Construct a Radio Frequency Identification (RFID) Network Planning (RNP) scenario based on the communication between tags and readers, between readers, and between readers and terminals. The RNP modeling method includes two technical points: first, deriving the RNP communication link equation with multi-level cascade characteristics; second, describing RNP based on the supply chain hierarchy and modeling the relationships between objects in the cascaded RNP network. Step 2: To derive the communication link equation in the RNP scenario, it is assumed that the tag and reader, adjacent readers of the same type, and readers and terminals all use uplink and downlink for communication, that is, there are bidirectional information transmission links. Step 3: To derive the maximum communication distance between the tag and the reader, define d. forward d represents the uplink transmission distance. reverse To find the downlink transmission distance, the maximum communication distance from the tag to the reader is D1, which is the distance when d forward <d reverse hour, When d forward >d reverse hour, Where λ is the wavelength, τ is the modulation efficiency, and μ T For transmission efficiency, The threshold for the reader's transmit power. This is the power threshold received by the passive tag in the forward link. The power threshold received by the backward link reader. G is the transmission power threshold for the tag. reader and G tag These are the gains of the reader antenna and the tag antenna, respectively; Step 4: Considering that the uplink and downlink communication distances between readers are equal, solve for the maximum communication distance between adjacent readers, and define reader R. I and R J The coordinates are (x) I y I ) and (x J y J The Euclidean distance between the two is With Reader R I For the transmitter, reader R J For the receiver, the reader R is derived based on Friis's formula. I With Reader R J The maximum communication distance between them is in, For Reader R J Antenna gain, For Reader R I Antenna gain, For Reader R J The transmission power, For Reader R I The received power threshold; Step 5: To obtain the maximum transmission distance between the reader and the terminal, define the reader R. H The coordinates are (x H y H The coordinates of application terminal A are (x...). A y A The Euclidean distance between the two is When application terminal A sends a message to reader R H When sending a message, the reader R is derived based on Friis's formula. H Maximum transmission distance of downlink communication with terminal A When reader R H When sending information to application terminal A, reader R H Maximum transmission distance of uplink communication with terminal A Among them, G A For the antenna gain of application terminal A, For Reader R H Antenna gain, P A t and Application terminal A and reader R are respectively. H The transmission power, and Application terminal A and reader R are respectively. H The received power threshold; Step 6: Based on the hierarchical classification concept in supply chain network planning and design, and in accordance with the horizontal dimension in the supply chain hierarchy, the RFID system is divided into three levels: the first level is passive tags, the second level is readers, and the third level is application terminals. Three links are defined for tags to reach the terminal via readers: link 1 is when the tag reaches the terminal via a single reader, link 2 is when the tag reaches the terminal via cascaded communication between two readers, and link 3 is when the tag reaches the terminal via cascaded communication between three readers. Step 7: To classify the readers in the link connection methods of Step 6, define the number of tags in the RNP scenario as I, the number of readers as M, and the number of terminals as K. The corresponding tag group set, reader group set, and terminal group set are IT = {IT1, IT2, ..., IT...} I }, IR={IR1, IR2,..., IR M }, IS={IS1, IS2,..., IS K }, among which, IT i Let IR be the identifier ID of the i-th label. m IS is the identifier ID of the m-th reader. k Let i be the identifier ID of the k-th terminal, and i ∈ [1, I], m ∈ [1, M], k ∈ [1, K]; Step 8: Redefine the functional role of readers in the RFID system by introducing the basic characteristics of the supply chain. Classify readers based on the distance between the reader and the tag, the distance between the reader and the terminal, and the role of the reader in its respective link. First, divide readers into two categories: data acquisition readers and data upload readers. Define the functions used to read RFID tag data and satisfy the discrimination formula. The device is a data acquisition reader. Based on the positional relationship between the tag and the reader, it can obtain the data that can be acquired from the i-th tag. i Collection of readers for communication Among them, L i For the use of IT tags i The number of data acquisition readers that communicate directly. For the i-th label IT i The l-th collector reader, l∈[1,L] i ], For the label IT i and collection reader The distance between the tag and the reader is D1, which is the maximum communication distance between them. When the distance between the tag and the reader is less than D1, they can establish communication, upload RFID tag data to the upper-level system, and satisfy the discrimination formula. The device is defined as an upload reader. Based on the location relationship between the terminal and the reader, it can obtain the information that can communicate with the k-th terminal via IS. k Collection of readers for communication Among them, O k To connect with the terminal IS k The number of upload readers communicating directly. For the i-th label IT i Related to and corresponding to the k-th terminal IS k The o-th uploader, o∈[1, O] k ], Uploaded Reader and terminal IS k The distance between them, D3 is the maximum communication distance between the reader and the terminal. When the distance between the reader and the terminal is less than D3, they can establish communication. Step 9: To facilitate the analysis of link conditions in the RNP scenario, based on the reader classification results in Step 8, readers are further divided into four types: direct-connection readers, uplink readers, jump-connection readers, and jump-jump readers. A device that satisfies both the definition of a data acquisition reader and the definition of an uplink reader is defined as a direct-connection reader, i.e., it must satisfy the discrimination formula. and The collection of readers is Among them, A i For the use of IT tags i The number of directly connected readers in the communication. For the i-th label IT i The a-th directly connected reader, a∈[1, A i ], Represents a direct-connect reader and the IT tag i The distance between them Represents a direct-connect reader and terminal IS k The distance between them, when the direct-connect reader and the tag and terminal respectively satisfy the discrimination formula, can establish communication and form the working path of link 1 in step 6. The device that meets the definition of the acquisition reader but not the definition of the upload reader is defined as the uplink reader, that is, it must meet the discrimination formula. and The collection of readers is Among them, U i For the use of IT tags i The number of connected readers in the communication. For the i-th label IT i The u-th uplink reader, u∈[1, U i ], Representing the IT label i Connect to the reader The distance between them Represents the connected reader and upload reader The distance between them Represents the connected reader and terminal IS k The distance between them, when the discriminant formula is satisfied between the uplink reader and the tag, upload reader, and terminal respectively, communication can be established and the working path of link 2 in step 6 can be formed. The acquisition reader in link 3 is defined as a jump reader. The discriminant formula and functions of this reader are the same as those of the uplink reader. The set of jump readers is as follows: Among them, B i For the use of IT tags i The number of jump readers in the communication. For the i-th label IT i The b-th jump reader, b∈[1, B] i A jump reader is defined as a device that can neither communicate directly with the tag nor directly with the terminal, but can still transmit tag information to the terminal through a data acquisition reader and an upload reader. This means it must satisfy the discrimination formula. and This type of reader is a collection of Among them, Z i To the number of readers that can be redirected, For the i-th label IT i The z-th jump reader, z∈[1, Z] i ], Representing the IT label i and jump reader The distance between them Represents a jump-connected reader and jump reader The distance between them Represents a jump reader and upload reader The distance between them Represents a jump reader and terminal IS k The distance between them is such that when the jump reader satisfies the discrimination formula with the tag, the jump reader, the upload reader, and the terminal respectively, communication can be established and the working path of link 3 in step 6 can be formed. Therefore, the three links in step 6 can be simplified as follows: Link 1: Tag - Direct Reader - Terminal; Link 2: Tag - Uplink Reader - Upload Reader - Terminal; Link 3: Tag - Jump Reader - Jump Reader - Upload Reader - Terminal. Thus, based on the naming rules and classification criteria of each reader, a matrix expression of the number of links traversed by the tag and the types of readers used can be obtained. Step 10: Model the RNP problem, selecting the option with maximum label coverage, minimum localization error, and a certain label IT. i The output is a set of reader locations and excitations with the minimum number of forwarding hops along the traversed link, in mathematical form as follows: Where Ω = [(x1, y1), (x2, y2), ..., (x... y1)], (x2, y2), ..., (x... y1) M y M )], F=ω1f1+ω2f2+ω3f3, Ω is a candidate solution of RNP, and the position coordinates of the m-th reader antenna are (x m y m ), m∈[1,M], the objective function F is the linear weighted sum of three sub-functions, namely: f1 is the proportion of labels not covered, f2 is the positioning accuracy error, f3 is the normalized forwarding hop count, and ω1, ω2, ω3 are the weight coefficients; Step 11: To maximize tag coverage, define the following based on the link status between readers: Indicates the connectivity of the link, if but like but Among them, dist(R) x R y () represents the Euclidean distance between the x-th reader and the y-th reader, where x, y ∈ [1, M]. This represents the maximum communication distance between the x-th reader and the y-th reader, defined based on the link status between the reader and the terminal. Perform a judgment, if but like but in, Indicates the uploader With terminal IS k European distance, Let x represent the maximum communication distance between the x-th reader and the k-th terminal, and define the availability of the m-th reader to the i-th tag as... This means that the i-th tag is considered successfully located when it is recognized by three or more readers, and the localization of the i-th tag can be determined by S. i It means that if Then S i =1, if Then S i =0, f1 in step 10 is defined as a non-covering form, that is Step 12: To achieve accurate assessment of positioning accuracy, the Geometric Dilution of Precision (GDOP) factor based on the lower bound of Cramer-Rao is used to evaluate the impact of reader deployment on positioning accuracy. Define... The coordinates of the l-th reader are (x) l y l ), l=1,2,...,L;L≥3, the relative angle between the reader and the target tag is α. l， l = 1, 2, ..., L; L ≥ 3, the distance from the l-th reader to the target tag is d. l Then the Jacobian matrix based on the Time of Arrival (TOA) is expressed as: The positional relationship between the target tag and the reader is obtained by calculating the... and In the TOA positioning system, H T Multiplying by H yields Tr(H) T If H) = L, then the expression for GDOP can be represented as: In step 10, f2 is defined as the positioning accuracy error, i.e. Where S i This indicates the locatability of the tag mentioned in step 11; Step 13: To achieve long-distance RFID transmission and reduce reader hop count, the number of tag hops the reader identifies in the entire RFID system is expressed as... Among them, i n For the label IT i The number of times the information passes through the nth link, w n Let f3 be the reader forwarding hop count for the nth link. Based on the three proposed link structures, the value of n will vary from 1 to 3. In step 10, f3 is defined as the normalized forwarding hop count, i.e.

2. The method according to claim 1, characterized in that, The implementation process of obtaining the matrix expression for the number of links traversed by the tag and the types of readers used in step 9, based on the naming rules and classifications of each reader, is as follows: Step 9-1: After naming and categorizing, different communication links are formed between the readers, tags, and terminals. Based on the differences in the number and location of readers in each link, the tag communication link connection methods are divided into three types, with tag IT as the primary factor. i For example, suppose this label has multiple links to the application terminal IS. k The links, all of which can correspond to three link connection methods, are labeled IT. i The link from the reader to the terminal and the type of reader used can be determined by... This indicates that each column in the matrix represents a different type of reader, from the leftmost to the rightmost column: direct-connect reader, uplink reader, jump-connect reader, jump-to-reader, and upload reader. Each tag is IT. i There can be multiple readers of different types connected to it, from the first row to the last row of the matrix, representing the tag IT. i The number of links that transmit information to the application terminal; Step 9-2: To select the most suitable link for the RFID system during information transmission, According to claim 1, the three novel objective functions jointly construct the RNP problem model. For the second passive tag, when there is only one terminal device, there are three transmission links between the tag and the application terminal. The first link is via a direct-connect reader. Upon reaching the terminal, the second step is via an upstream reader. Upload Reader Upon reaching the terminal, the third step is via a jump-connected reader. Jump to Reader Upload Reader Upon reaching the terminal, all links can be accessed. The matrix representation of .

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