Cellular passive frequency division multiplexing ultrahigh frequency RFID system

Abstract

The invention discloses a cellular passive frequency division multiplexing ultrahigh frequency RFID (Radio Frequency Identification) system, which is applied to the field of communication, and designs a full-link passive frequency division multiplexing UHF RFID system architecture aiming at the key problems of low communication efficiency, small base station coverage range, strong same-frequency receiving and transmitting self-interference, low system throughput rate and the like of the current passive UHF RFID system. A plurality of auxiliary base stations are deployed around a base station in a distributed manner, a base station-auxiliary base station wireless communication channel is planned, one base station accesses and manages the plurality of auxiliary base stations at the same time, and the auxiliary base stations excite universal electronic tags in respective coverage ranges by adopting radio frequency carriers of different frequency points. And meanwhile, the multiple tags execute reflection after frequency offset is superposed at respective excitation carrier frequency points, and parallel receiving and analysis of multi-tag backscattering signals are completed by the base station. By establishing the full-link frequency division multiplexing architecture, the system can fully utilize frequency band resources according to the transmission bandwidth required by each link, and the system is supported to execute a large number of label parallel communication processes, so that the overall throughput rate and the communication efficiency of the system are improved.

Description

Technical Field

[0001] The invention belongs to the field of communications, and in particular relates to an RFID system. Background Art

[0002] In recent years, the country has attached more and more importance to the construction and development of new infrastructure for the Internet of Things. The Internet of Things has become an important part of the new infrastructure in the fields of people's livelihood consumption, social governance, and industry applications. Among them, Radio Frequency Identification (RFID) technology is considered to be one of the most important core technologies in the Internet of Things. With the rapid development of Internet of Things technology, its application scope is also expanding, which puts higher requirements on the throughput and system efficiency of UHF RFID systems.

[0003] In traditional UHF RFID technology, the system adopts an integrated transceiver architecture, and its backscatter receiver and carrier exciter are integrated into an integrated reader-writer device. At this time, there are key problems such as small base station coverage, strong co-frequency self-interference, short system communication distance, and low system communication efficiency. These problems limit the promotion and application of UHF RFID systems in IoT applications. Therefore, a separate transceiver system architecture has been derived. In this architecture, the backscatter receiver and carrier exciter are respectively located in the reader-writer (also known as the base station) and the auxiliary equipment, and the structure and function design of different auxiliary equipment are different. At present, common research mainly arranges new auxiliary equipment around the tag, as a repeater to play the role of amplification and retransmission to expand the reading coverage of the reader-writer. The normal operation of the UHF RFID system needs to meet the relevant standards and regulations, and at the same time comply with the working frequency band, channel bandwidth and transmission spectrum template specifications formulated by various countries and regions for UHF RFID applications. At present, the mainstream UHFRFID air interface standard is the ISO / IEC 18000-6C international standard, and my country has also issued the corresponding UHF RFID standard GB / T29768-2013. According to the latest national spectrum allocation standards, applications for model approval of RFID radio transmitter equipment in the 840-845MHz frequency band will no longer be accepted or approved, so the current UHF RFID system can only communicate in the 920-925MHz frequency band. The traditional separate transmit-receive architecture uses the 840MHz frequency band for base station-auxiliary equipment communication, and the 920MHz frequency band for base station-terminal communication architecture is no longer applicable. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a cellular passive frequency division multiplexing ultra-high frequency RFID system. By establishing a full-link frequency division multiplexing architecture, the system can make full use of frequency band resources according to the transmission bandwidth required by each link, and support the system to execute a large number of tag parallel communication processes, thereby improving the overall system throughput and system communication efficiency.

[0005] The technical solution adopted by the present invention is: a cellular passive frequency division multiplexing ultra-high frequency RFID system, including: a host computer, a base station, an auxiliary base station, and an electronic tag; a base station covers a plurality of auxiliary base stations, and an auxiliary base station covers a plurality of electronic tags; the base station uses a specific channel to achieve parallel access and management of the plurality of auxiliary base stations within its coverage; the auxiliary base station uses carrier exciters with different frequencies to excite the electronic tags within its coverage area; the electronic tag performs reflection after superimposing a frequency offset on its corresponding excitation carrier frequency; the base station acts as a backscatter receiver to complete the parallel reception and analysis of backscatter signals of a plurality of electronic tags.

[0006] Beneficial effects of the present invention: In view of the key problems of low communication efficiency, small base station coverage, strong self-interference of co-frequency transmission and reception, and low system throughput of the current passive UHF RFID system, the present invention proposes a cellular passive frequency division multiplexing ultra-high frequency RFID system for the first time. A full-link passive frequency division multiplexing UHF RFID system architecture is designed, and multiple auxiliary base stations are distributedly deployed around the base station, and the base station-auxiliary base station wireless communication channel is divided. One base station simultaneously accesses and manages multiple auxiliary base stations, and the auxiliary base stations use radio frequency carriers of different frequencies to excite universal electronic tags within their respective coverage areas. At the same time, multiple tags perform reflection after superimposing the frequency offset on their respective excitation carrier frequencies, and the base station completes the parallel reception and analysis of the backscattered signals of multiple tags. By establishing this full-link frequency division multiplexing architecture, the system can make full use of the frequency band resources according to the transmission bandwidth required by each link, and support the system to execute a large number of parallel communication processes of tags, thereby improving the overall throughput of the system and the communication efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a two-point UHF RFID system.

[0008] Figure 2 It is a traditional three-point UHF RFID system.

[0009] Figure 3 Schematic diagram of the cellular passive frequency division multiplexing UHF RFID system architecture.

[0010] Figure 4 Schematic diagram of the system working channel.

[0011] Figure 5 This is the system workflow diagram.

[0012] Figure 6 This is the system working timing diagram. DETAILED DESCRIPTION

[0013] To facilitate those skilled in the art to understand the technical content of the present invention, the present invention is further explained below with reference to the accompanying drawings.

[0014] In view of the key problems of the current passive UHF RFID system, such as low communication efficiency, small base station coverage, strong self-interference of co-frequency transmission and reception, and low system throughput, the present invention proposes a cellular passive frequency division multiplexing ultra-high frequency RFID system for the first time. A full-link passive frequency division multiplexing UHF RFID system architecture is designed, multiple auxiliary base stations are distributedly deployed around the base station, and the base station-auxiliary base station wireless communication channel is planned. One base station simultaneously accesses and manages multiple auxiliary base stations, and the auxiliary base stations use radio frequency carriers of different frequencies to excite universal electronic tags within their respective coverage areas. At the same time, multiple tags perform reflection after superimposing the frequency offset on their respective excitation carrier frequencies, and the base station completes the parallel reception and analysis of the backscattered signals of multiple tags. By establishing this full-link frequency division multiplexing architecture, the system can make full use of the frequency band resources according to the transmission bandwidth required by each link, and support the system to execute a large number of parallel communication processes of tags, thereby improving the overall throughput of the system and the communication efficiency of the system.

[0015] Conventional UHF RFID adopts a transceiver-integrated (also known as two-point) architecture. The system consists of three parts: reader, electronic tag, and host computer. Figure 1 As shown in the figure. The reader integrates a backscatter receiver and a carrier exciter, the tag stores the unique identification of the physical object, and the host computer is used to implement application layer functions and data processing. According to the ISO / IEC 18000-6C international standard, the system uses wireless radio frequency to realize non-contact bidirectional data transmission between the reader and the electronic tag. The reader radiates a continuous radio frequency signal of a fixed frequency through the antenna to start the communication process. When the tag within the radiation range obtains enough energy, it is activated and then modulates its own stored information onto the received radio frequency carrier and backscatters through the built-in antenna. The reader receives the reflected signal of the tag, demodulates and decodes it, and sends it to the system host computer for further data processing. The tag directly modulates and forwards the received radio frequency carrier, and the communication distance is severely limited. In addition, the frequency band of the reader receiving link is the same as that of the sending link, and there is a strong self-interference phenomenon, which causes serious bit errors during signal analysis, thereby affecting the system recognition efficiency.

[0016] To solve the above problems, a three-point architecture was developed, such as Figure 2As shown in the figure, the system mainly includes three parts: UHF RFID base station, auxiliary base station, and electronic tag. The system mainly uses time division multiplexing to perform terminal data communication. The carrier exciter is arranged around the tag as a relay and excitation source to expand the reading coverage of the reader. However, only the tag with a random time slot value solt of 0 can respond to the base station command. When multiple tags respond to the reader command at the same time, a tag signal collision will occur. The tag needs to reselect the random time slot value and wait for the next response time slot, which seriously affects the system throughput and communication efficiency.

[0017] In order to solve the problems of low throughput and communication efficiency of the existing UHF RFID system, the present invention proposes a cellular passive frequency division multiplexing ultra-high frequency RFID system and designs a full-link passive frequency division multiplexing UHF RFID system architecture. By establishing this full-link frequency division multiplexing architecture, the system can make full use of the frequency band resources according to the transmission bandwidth required by each link, and support the system to execute a large number of tags in parallel communication processes, thereby improving the overall system throughput and system communication efficiency. Figure 3 As shown in the figure, the system consists of a host computer, a base station, an auxiliary base station, and tags. According to the application coverage needs, a base station B and n auxiliary base stations H1-H are set up. n , each auxiliary base station covers m tags Tn1-Tn m . According to the design, the base station uses multi-frequency transceiver devices or broadcast protocol commands to activate all or specific auxiliary base stations within the coverage area, and uses specific channels to achieve parallel access and management of multiple auxiliary base stations; the auxiliary base station acts as a carrier exciter, mainly demodulating the base station signal to complete the system networking access, and realizes direct forwarding or frequency conversion forwarding to excite the tags within its coverage area; at the same time, multiple tags perform the data transmission function after superimposing the frequency offset on their respective excitation carrier frequencies, and the base station acts as a backscatter receiver to complete the parallel reception and analysis of the backscatter signals of multiple tags.

[0018] Figure 3 Where f1, f2, f3, ..., fn represent the frequencies used by the base station to communicate with different auxiliary base stations, that is, the excitation frequencies corresponding to the auxiliary base stations; Figure 3 Here, Δf represents the unit frequency deviation.

[0019] According to the 900MHz band radio frequency identification (RFID) radio transmission equipment radio frequency technical requirements issued by the Ministry of Industry and Information Technology: UHF RFID equipment operating frequency band is 920MHz-925MHz; channel center frequency fc (MHz) = 920.125 + M × 0.25 (M is an integer, ranging from 0 to 19), and the occupied bandwidth is not greater than 250kHz; within the frequency range of 920-920.5MHz and 924.5-925MHz, the effective radiated power limit is 100mW (20dBm), and within the frequency range of 920.5-924.5MHz, the effective radiated power limit is 2W (33dBm). The entire system link shares this 5MHz available bandwidth, such as Figure 4 As shown in the figure, the frequency band is divided according to the number of auxiliary base stations n and the channel bandwidth application specifications. Each auxiliary base station uses a channel in the allocated frequency band to complete the interaction with the base station command information and activate the tags within the coverage range on this channel. In the frequency band occupied by each auxiliary base station, the unoccupied channels are also selected and divided according to the number of tags m and the minimum data transmission bandwidth ΔB required by the tags.

[0020] For example, if the available bandwidth of the auxiliary base station is 1M, the tag m=3, and Δf=200k, it can be deployed continuously on three adjacent channels according to the application transmission needs, and three tags can be identified at the same time, but there may be mutual interference and poor signal quality, resulting in identification failure; or it can be deployed on two channels at intervals, requiring at least two rounds of identification to complete the identification of the three tags, but the interference is small and the signal quality is good.

[0021] The system workflow is as follows Figure 5As shown, the system is first powered on and initialized, and the host computer writes the ID of the auxiliary base station to be operated into the memory of the base station. Under the instruction of the host computer, the base station starts the networking process with the auxiliary base station, and according to the circuit structure design of the base station, performs multi-frequency polling or single-frequency broadcasting to send channel division information, that is, the networking command carrying the auxiliary base station ID and the corresponding channel information. The auxiliary base station that receives the networking command transmits a response signal on the specified channel to complete the networking process, and waits to receive the next instruction from the base station. After judging that the networking is completed, the base station controls the auxiliary base station that has been connected to the network to forward the base station command and activate the tag, so that the base station can inventory / access all tags within the coverage of the auxiliary base station. The tag that receives the inventory command randomly selects a channel within the available frequency band to reflect its own binding information. The base station receives the tag reflection signals of multiple channels at the same time, and sends a confirmation beacon according to the parsed tag information. The tag with matching information confirms the response on the original channel. The base station saves the received tag ID into the tag ID list and checks whether the inventory process has timed out / ended. When the inventory is completed, the base station can select a specific tag for access. The access process is the same as the inventory process. The base station will return the received access data to the host computer and check whether the access process has timed out / ended, or directly end the current round of system work.

[0022] The working sequence of the cellular passive frequency division multiplexing ultra-high frequency RFID system is as follows: Figure 6 As shown, during the networking of the base station and the auxiliary base station, the tag does not need to respond. At the same time, a base station can supervise multiple auxiliary base stations to work together. Each auxiliary base station can be designed with multiple transmission channels to provide radio frequency energy for tags within the communication range of the auxiliary base station, and the auxiliary base stations are deployed in a cellular manner to ensure large-capacity and leak-free identification of tags. Multiple tags perform parallel backscattering in their respective channels through a channel selection algorithm, and the colliding tags reselect channels to respond in the next round of inventory, thereby improving the overall throughput of the system. The data interaction timing between the base station and the tag is compatible with the international standard protocol ISO 18000-6C.

[0023] In this embodiment, the channel selection algorithm adopts a random selection method.

[0024] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the scope of protection of the present invention is not limited to such specific statements and embodiments. For those skilled in the art, the present invention may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A cellular passive frequency division multiplexing ultra-high frequency RFID system, characterized in that: include: Host computer, base station, auxiliary base station, and electronic tag; The coverage area of ​​one base station includes multiple auxiliary base stations, and the coverage area of ​​one auxiliary base station includes multiple electronic tags; The base station uses a specific channel to achieve parallel access and management of multiple auxiliary base stations within the coverage area; the auxiliary base station uses carrier exciters with different frequencies to excite the electronic tags within its coverage area; The electronic tag performs reflection after superimposing the frequency offset on its corresponding excitation carrier frequency point; The base station acts as a backscatter receiver, completing the parallel reception and analysis of backscatter signals from multiple electronic tags.

2. A cellular passive frequency division multiplexing UHF RFID system according to claim 1, characterized in that: The base station uses a multi-frequency transceiver device or a broadcast protocol command to activate all or specific auxiliary base stations within the coverage area.

3. A cellular passive frequency division multiplexing UHF RFID system according to claim 1, characterized in that: The frequency band is divided according to the number of auxiliary base stations accessed and the channel bandwidth application specifications. Each auxiliary base station uses a channel within the allocated frequency band to complete the interaction with the base station and activates the tags within the coverage area on the channel.

4. A cellular passive frequency division multiplexing UHF RFID system according to claim 3, characterized in that: In the frequency band occupied by each auxiliary base station, unoccupied channels in the frequency band are divided according to the number of tags and the minimum data transmission bandwidth required by the tags.

5. A cellular passive frequency division multiplexing UHF RFID system according to claim 4, characterized in that: The tag randomly selects a channel to reflect information within its corresponding frequency band.

6. A cellular passive frequency division multiplexing UHF RFID system according to claim 5, characterized in that: The auxiliary base stations are deployed in a cellular manner.

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