Networking communication method for cellular passive frequency division multiplexing ultra-high frequency RFID system

Abstract

The application discloses a kind of cellular passive frequency division multiplexing ultra-high frequency RFID system networking communication method, applied to communication field, the contraction of working frequency band intensifies the collision of system communication signal and base station receiving end interference source, further influence the problem of communication efficiency and reliability of system;The application proposes cellular passive frequency division multiplexing ultra-high frequency RFID system multi-band synchronous networking access method, with system multi-device channel collaborative switching networking access method, design base station-assisted base station wireless networking protocol, standardize system network communication process, ensure the reliability and stability of cellular passive frequency division multiplexing ultra-high frequency RFID system long-distance efficient identification communication work, to realize passive UHF RFID object system with low-cost wide-area coverage.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of communication, and particularly relates to a networking communication technology of an RFID system. BACKGROUND

[0002] Radio Frequency Identification (RFID) technology, which identifies physical objects through wireless communication, has become the cornerstone of the implementation of Internet of Things technology. The theory and industry of RFID technology are gradually maturing and perfecting. According to the different working frequencies, RFID technology can be divided into four main types: low frequency (125 / 134 kHz), high frequency (13.56 MHz), ultra-high frequency (860-960 MHz) and microwave (2.4 / 5.8 GHz). Low frequency and high frequency RFID technology adopts near field coupling principle, is suitable for near distance identification, and is currently the most widely used. Ultra-high frequency (UHF) RFID and microwave RFID adopt far field coupling principle, and have the ability of long distance identification and high speed transmission.

[0003] The traditional UHF RFID system adopts a transceiver integrated architecture (also known as a two-point architecture), in which the reader integrates a backscatter receiver and a carrier exciter, thereby generating key problems such as small reader coverage, strong transceiver same frequency self-interference, and low system communication efficiency. Further, a transceiver separation system architecture (also known as a three-point architecture) is derived, that is, a backscatter receiver (also known as a base station) and a carrier exciter (also known as an auxiliary base station) are respectively set up, and the carrier exciter is arranged around the terminal (tag) to expand the system coverage. The existing three-point UHF RFID system mainly adopts a time division multiplexing mode for data communication, that is, the base station can only receive the backscatter signal of one tag or issue an instruction to one auxiliary base station at the same time, so that the data transmission in the system is limited by the communication time slot. When multiple tags respond to the reader at the same time, tag signal collision occurs, the reader is difficult to correctly parse the tag information or tag information identification error occurs, which seriously affects the system throughput. When the base station detects the collision, according to the UHF RFID standard protocol specification, the tag needs to reselect a random time slot value, and the base station needs to perform corresponding state jump and protocol command issuing to re-start the tag identification process, which further affects the communication efficiency of the three-point UHF RFID system.

[0004] According to the latest spectrum allocation standards from the Ministry of Industry and Information Technology (MIIT), current UHF RFID systems can only communicate in the 920-925 MHz frequency band. This narrowing operating frequency band exacerbates signal collisions and interference at the base station receiver, further impacting system communication efficiency and reliability. Furthermore, due to the performance limitations of existing domestically manufactured discrete components, it will be difficult to meet the timing specifications of the system link in the standard protocol without proper design of the system's communication frequency band and communication process. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention proposes a cellular passive frequency division multiplexing ultra-high frequency RFID system networking communication method.

[0006] The technical solution adopted by the present invention is: a cellular passive frequency division multiplexing ultra-high frequency RFID system networking communication method, the cellular passive frequency division multiplexing ultra-high frequency RFID system includes: a host computer, a base station, multiple auxiliary base stations deployed within the coverage area of ​​the base station, and electronic tags within the coverage area of ​​each auxiliary base station; the auxiliary base station acts as a carrier exciter, and the auxiliary base station excites the electronic tags within the coverage area according to the forwarding signal of the base station; the electronic tags perform reflection after superimposing a frequency offset on their corresponding excitation carrier frequency point, and the base station acts as a backscatter receiver. Specifically, a multi-band synchronous networking access method is adopted, including the following process:

[0007] First, the system is initialized. The base station uses USB2.0 to implement two-way information exchange with the host computer. The host computer writes the IDs of all auxiliary base stations within the base station coverage area into the auxiliary base station ID list in the base station memory.

[0008] The host computer first sends the sub-channel division information of each auxiliary base station to the base station;

[0009] The base station activates a specific auxiliary base station through the auxiliary base station ID under the initialization channel configuration and transmits the available channel information;

[0010] The auxiliary base station that matches its own ID returns a confirmation beacon on the specified channel to complete the activation, while the inactivated auxiliary base station continues to listen to the next command signal from the base station.

[0011] After the auxiliary base station networking is completed, the activated auxiliary base stations stimulate the electronic tags within the coverage area on their respective channels and forward the base station commands;

[0012] After receiving the inventory command, electronic tags within the coverage of different auxiliary base stations superimpose a random frequency shift within the sub-channel range on the excitation carrier frequency and then reflect their own information. The base station simultaneously receives and parses the reflected information of tags on multiple channels. Electronic tags that do not receive a confirmation beacon that matches their own ID wait for the next inventory command and reselect a channel to respond.

[0013] The base station transmits the self-binding information of the electronic tag and the corresponding auxiliary base station ID and other information to the upper computer.

[0014] When the number of allocated channels is less than the number of auxiliary devices currently required for networking, the process of sharing the communication channel is further included, and when the base station monitors the current networking state for a preset working time, the current signal is allocated to the unconnected auxiliary device according to the identification efficiency of each channel in the current stage.

[0015] If the identification efficiency of a certain channel in the current stage is greater than or equal to the first proportion of the average identification efficiency, the currently connected auxiliary device is retained, or the current signal is re-allocated to a random unconnected auxiliary device within the first distance range from the connected auxiliary device.

[0016] If the identification efficiency of a certain channel in the current stage is less than the first proportion of the average identification efficiency, the current channel is re-allocated to a random unconnected auxiliary device outside the first distance range from the connected auxiliary device.

[0017] The beneficial effects of the present application are as follows: The present application is aimed at the system heterogeneous networking of multiple auxiliary base stations in a cellular passive frequency division multiplexing ultra-high frequency RFID system, and the networking access mode of multiple auxiliary base stations in the system and the corresponding communication protocol are finely designed, a multiple frequency band synchronous networking access method for the cellular passive frequency division multiplexing ultra-high frequency RFID system is proposed, a system multi-device channel collaborative switching networking access method is designed, a corresponding base station-auxiliary base station wireless networking protocol is designed, the system network communication process is standardized, and the reliability and stability of the cellular passive frequency division multiplexing ultra-high frequency RFID system for long-distance efficient identification communication are ensured, thereby realizing a passive UHF RFID object system with low cost and wide area coverage. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Fig. 3 is a structural schematic diagram of a three-point UHF RFID system;

[0019] Figure 2 Fig. 4 is a deployment schematic diagram of a cellular passive frequency division multiplexing ultra-high frequency RFID system;

[0020] Figure 3 Fig. 5 is a flowchart of a multiple frequency band synchronous networking communication method of an auxiliary base station;

[0021] Figure 4 Fig. 6 is a flowchart of a channel collaborative switching networking communication method between auxiliary base stations. DETAILED DESCRIPTION

[0022] In order to facilitate those skilled in the art to understand the technical content of the present application, the content of the present application is further explained below in conjunction with the drawings.

[0023] Under the background of current passive UHF RFID system frequency band shrinkage and the performance limitation of domestic discrete devices, the system has problems such as low communication efficiency, terminal identification blind spot, small base station coverage, and strong self-interference of transceiver same frequency, etc. The application proposes a multi-frequency synchronous networking access method for the cellular passive frequency division multiplexing ultra-high frequency RFID system with multiple auxiliary base stations, a system multi-device channel collaborative switching networking access method, a base station-auxiliary base station wireless networking protocol, and a system network communication process specification to ensure the reliability and stability of the cellular passive frequency division multiplexing ultra-high frequency RFID system for long-distance efficient identification communication, and to realize a passive UHF RFID object system with low cost and wide coverage.

[0024] The transceiver separation type (also known as three-point type) UHF RFID system architecture is shown in Figure 1 The existing three-point type UHF RFID system mainly adopts time division multiplexing mode for data communication, and the base station can only receive the backscattering signal of one tag or issue instructions to one auxiliary base station at the same time. The system data transmission is still limited by the current communication time slot state. When multiple tags respond to the reader's instructions at the same time, tag signal collision will occur, and the reader will have difficulty in correctly parsing the tag information or be prone to tag information identification error. This seriously affects the system throughput. After the base station detects the conflict, according to the UHF RFID standard protocol specification, the tag needs to reselect a random time slot value, and the base station needs to perform corresponding state jump and protocol command issuance to restart the tag identification process, which further affects the communication efficiency of the three-point type UHF RFID system.

[0025] According to the new rules of the State Ministry of Industry and Information Technology, the current UHF RFID system can only work in the frequency band of 920-925 MHz, which is too narrow, and the transmission data rate is limited by the performance of existing RFID RF chips. If the communication between the base station and the auxiliary base station and the communication frequency band and communication process of the auxiliary base station are not reasonably designed, signal collision is easy to occur in the full-duplex system communication, which makes the tag unable to correctly receive the command forwarded by the auxiliary base station, and the base station receiving end cannot correctly analyze the tag reflection signal, and it is difficult to meet the timing requirements of the standard protocol for system operation. Therefore, the present application is aimed at the heterogeneous networking of the multi-assistant base station in the cellular passive frequency division multiplexing ultra-high frequency RFID system, and the networking access method and the corresponding communication protocol of the multi-assistant base station in the system are designed in detail, and a multi-frequency band synchronous networking access method of the cellular passive frequency division multiplexing ultra-high frequency RFID system is proposed. The channel collaborative switching networking access method between the system and the corresponding base station-auxiliary base station wireless networking protocol is designed, the system network communication process is standardized, the reliability and stability of the long-distance efficient identification communication of the cellular passive frequency division multiplexing ultra-high frequency RFID system are ensured, and then the passive UHF RFID object system with low-cost wide-area coverage is realized.

[0026] The present application proposes a cellular passive frequency division multiplexing ultra-high frequency RFID system based on domestic discrete devices as shown in Figure 2 The base station (Base-Station) covers the range (BS Work area) and distributes multiple auxiliary base stations (Helper) in the range. The auxiliary base station is a carrier exciter, which mainly demodulates the base station signal to complete the system networking access, and realizes the functions of direct forwarding or frequency conversion forwarding. The signal forwarded by the auxiliary base station will excite the electronic tags (Tag) in its coverage area (H Work area), and the tags realize data parallel transmission function through backscattering the auxiliary base station radio frequency carrier, and the base station is used as a backscattering receiver to receive and analyze the ID information reflected by the electronic tags. Considering the possible scenarios in the working of the cellular object system, multiple auxiliary base station networking access methods and corresponding communication protocols are designed to ensure the reliability and stability of the system operation.

[0027] The auxiliary base station multi-frequency band synchronous networking communication method is designed as Figure 3As shown, first, system initialization is performed, the base station uses USB2.0 to realize bidirectional information interaction with the host computer, the host computer writes all the auxiliary base station IDs in the coverage range of the base station into the base station memory (Helper ID list), when the auxiliary base station does not change, that is, there is no new addition or removal of available auxiliary base stations in the coverage range of the base station, the host computer can not change the auxiliary base station ID list in the base station. The host computer first issues each auxiliary base station subchannel division information to the base station to start the networking process, and the base station activates a specific auxiliary base station through the auxiliary base station ID under the initialization channel configuration and transmits available channel information. The auxiliary base station matching its own ID returns an acknowledgement beacon on the specified channel, thereby achieving the function of the auxiliary base station accessing the system network (i.e., auxiliary base station networking), and the auxiliary base stations that have not been activated continue to listen to the next command signal of the base station. After judging that the auxiliary base station networking is completed, that is, all the auxiliary base station IDs of the allocated channels have returned the acknowledgement beacon, the activated auxiliary base stations in the respective channels stimulate the tags in the coverage range and forward the base station commands, thereby enabling the base station to simultaneously inventory multiple tags covered by different auxiliary base stations. After the tags in the coverage range of different auxiliary base stations parse the inventory command, they reflect their own information after superimposing a random frequency shift amount in the subchannel range on the basis of the stimulated carrier frequency point, the base station simultaneously receives and parses the tag reflection information of multiple channels, the tags that do not receive the acknowledgement beacon matching their own ID wait for the next inventory command and reselect the channel for response. The base station returns the tag self-binding information and corresponding auxiliary base station ID and other information to the host computer.

[0028] The above system workflow is for the case that multiple auxiliary base stations in the coverage range of the base station work simultaneously, but due to the shrinkage of the available frequency band of the current UHF RFID system, when the system deployment scale is large or the data transmission bandwidth requirement is high, it is impossible to guarantee sufficient spectrum resources, that is, the available frequency band resources do not match the number of auxiliary base stations / transmission bandwidth demand, and there are also interferences such as multipath effect when some devices at some physical locations use some frequency bands for communication, which results in low identification efficiency. At this time, the frequency band can also be switched to improve the identification efficiency, so there is such a switching decision condition. To guarantee the continuity and stability of the efficient identification work of the system, part of the auxiliary base stations will share the communication channel, at this time, part of the auxiliary base stations in the coverage range of the base station exist time-sharing work conditions, that is, the system work process will involve switching networking access between multiple auxiliary base stations, thereby realizing the inventory identification of more area tags.

[0029] Aiming at this problem, a low-latency channel cooperative switching networking communication method between multiple devices is designed, such as Figure 4As shown, the auxiliary base station switching networking can be specified by the host computer command switching or base station autonomous switching. The host computer command specifies the switching process consistent with the multi-band synchronous networking method, that is, each round of networking is started by the base station receiving the host computer networking command, and the base station sends the networking signal carrying the updated networking channel division information and the ID of the auxiliary base station in the current round. The auxiliary base station with matching ID is activated and starts to perform the forwarding task after confirmation. The auxiliary base station not activated or removed from the system in the current round of networking clears the channel allocation information and continues to monitor the base station command. The base station autonomous switching networking process is based on the preset switching time interval. The preset value of the switching interval can estimate the number of tags to be identified in real time, and the identification efficiency in the continuous sliding monitoring stage as the decision condition, and dynamically update according to the different condition weight settings. The channels involved in the cooperative switching can be the identification efficiency of each channel stage and the physical location of the auxiliary base station occupying the channel as the selection condition. If the channel identification efficiency is high, the current access device is planned to be reserved or assigned to the auxiliary base station close to the current access device, and vice versa. When the base station monitors the current networking state to reach the preset working time, according to the channel cooperative selection information, the corresponding ID is selected from the stored auxiliary base station ID list to construct a complete switching networking command and execute the command issuing function, and the switching networking information is returned to the host computer.

[0030] The calculation method of the preset switching time interval in this embodiment is:

[0031] The preset switching time interval = f1*the number of tags to be identified + f2*the identification efficiency

[0032] Wherein, f1, f2 are weights;

[0033] If the switching interval is 1h, it means that switching is performed every 1h, and the working time is also 1h.

[0034] Assuming that the minimum time unit is s, the average identification efficiency of a certain system is 50 / s, the current monitoring stage identification efficiency is 30 / s, that is, 60% of the average identification efficiency of the system, and the estimated number of tags to be identified is 5000. If the goal is to reduce the total identification time, the weight f1 = 1 / 50 and f2 = ln0.6 can be designed according to the principle that the number of tags to be identified is proportional to the switching time and the identification efficiency is inversely proportional to the switching time. The preset switching time interval = (1 / 50)*5000+(ln0.6)*30 = 85s, and the calculation result can be rounded according to the minimum time unit.

[0035] The identification efficiency in this embodiment = the number of terminals (tags) identified per unit time.

[0036] In the embodiment, the recognition efficiency is considered to be high if it is greater than or equal to 80% of the average recognition efficiency, and is considered to be low otherwise. In actual applications, the proportion of the average recognition efficiency can be adjusted according to needs to adjust the division of high and low recognition efficiencies.

[0037] When the recognition efficiency is high, the current channel is allocated to a random one of the auxiliary devices within the first distance range from the currently accessed auxiliary device; when the recognition efficiency is low, the current accessed channel is allocated to a random one of the auxiliary devices beyond the first distance range from the current auxiliary device. In the embodiment, the first distance range is the distance between the auxiliary device closest to the currently accessed auxiliary device, and if there are multiple auxiliary devices closest to the currently accessed auxiliary device, a random one of the auxiliary devices is selected.

[0038] If the transmission delay is ignored, T=T', to ensure that there is no loss of signal transmission, it is necessary to ensure that the starting point T1 of each round of switching networking of the system is greater than or equal to an integer multiple of T4, and the base station buffers the commands according to this principle, and controls the switching networking process to be executed according to the preset switching priority.

[0039] The networking command data frame sent by the base station is composed of a command code, a device quantity, a device parameter, a frequency band information, and a CRC check bit, as shown in Table 1.

[0040] Table 1 Base station networking command data frame structure

[0041]

[0042] After the auxiliary base station receives the base station networking command, it transmits a response signal to the base station on the specified channel, and the response data frame is composed of a response code and a response parameter, as shown in Table 2.

[0043] Table 2 Auxiliary base station response data frame structure

[0044]

[0045] The delimiter and the pilot header are added to each data frame before it is sent, and when the ID parameter in the response signal received by the base station matches, it indicates that the Helper controlled by the base station is in an activated state, and the base station can send other function commands, and the activated Helper will forward the base station commands.

[0046] Those skilled in the art will appreciate that the embodiments described herein are intended to help the reader understand the principles of the present application and should be understood as not limiting the scope of protection of the present application to such specific statements and embodiments. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the claims of the present application.

Claims

1. A cellular passive frequency division multiplexing ultra-high frequency RFID system networking communication method, characterized in that: The cellular passive frequency division multiplexing (PFM) ultra-high frequency RFID system includes: a host computer, a base station, multiple auxiliary base stations deployed within the base station's coverage area, and electronic tags within the coverage area of ​​each auxiliary base station. The auxiliary base station acts as a carrier exciter, and the auxiliary base station excites the electronic tags within the coverage area based on the base station's forwarding signal. The electronic tags reflect after adding a frequency offset to their corresponding excitation carrier frequency, and the base station acts as a backscatter receiver. Specifically, a multi-band synchronous networking access method is used, including the following process: First, the system is initialized. The base station uses USB2.0 to implement two-way information exchange with the host computer. The host computer writes the IDs of all auxiliary base stations within the base station coverage area into the auxiliary base station ID list in the base station memory. The host computer first sends the sub-channel division information of each auxiliary base station to the base station; The base station activates a specific auxiliary base station through the auxiliary base station ID under the initialization channel configuration and transmits the available channel information; The auxiliary base station that matches its own ID returns a confirmation beacon on the specified channel to complete the activation, while the inactivated auxiliary base station continues to listen for the next command signal from the base station; When the base station monitors the current networking status for a preset working time, it allocates the current channel to the auxiliary device that has not been connected based on the recognition efficiency of each channel at the current stage.

2. The cellular passive frequency division multiplexing ultra-high frequency RFID system networking communication method according to claim 1, characterized in that: After the auxiliary base station networking is completed, the activated auxiliary base stations stimulate the electronic tags within the coverage area on their respective channels and forward the base station commands; After receiving the inventory command, electronic tags within the coverage of different auxiliary base stations superimpose a random frequency shift within the sub-channel range on the excitation carrier frequency and then reflect their own information. The base station simultaneously receives and parses the reflected information of tags on multiple channels. Electronic tags that do not receive a confirmation beacon that matches their own ID wait for the next inventory command and reselect a channel to respond. The base station transmits the binding information of the electronic tags counted and the corresponding auxiliary base station ID and other information back to the host computer.

3. The cellular passive frequency division multiplexing ultra-high frequency RFID system networking communication method according to claim 1, characterized in that: If the recognition efficiency of a certain channel in the current stage is greater than or equal to the first proportion of the average recognition efficiency, the auxiliary device connected to the current channel is retained, or the current channel is reallocated to a random non-connected auxiliary device within the first distance range from the connected auxiliary device.

4. The cellular passive frequency division multiplexing ultra-high frequency RFID system networking communication method according to claim 3, characterized in that: If the recognition efficiency of a certain channel at the current stage is less than the first proportion of the average recognition efficiency, the current channel is reallocated to a random non-connected auxiliary device outside the first distance range from the connected auxiliary device.

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