CN107742088B - Passive computable RFID anti-collision method based on energy prediction - Google Patents

Passive computable RFID anti-collision method based on energy prediction Download PDF

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CN107742088B
CN107742088B CN201710947976.3A CN201710947976A CN107742088B CN 107742088 B CN107742088 B CN 107742088B CN 201710947976 A CN201710947976 A CN 201710947976A CN 107742088 B CN107742088 B CN 107742088B
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李付江
李灯熬
赵菊敏
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Taiyuan University of Technology
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/10009—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
    • G06K7/10019—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers.
    • G06K7/10029—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers. the collision being resolved in the time domain, e.g. using binary tree search or RFID responses allocated to a random time slot

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Abstract

The invention discloses a passive computable RFID anti-collision method based on energy prediction, and relates to the technical field of radio frequency identification in wireless communication; based on the estimation of the energy E, the charging time required by a passive calculable RFID tag to successfully complete one-time data communication is converted into the time slot number or the frame number of the tag, the tag does not carry out any data communication with a reader within the time slot number or the frame number, and the reader carries out communication with the tag when the time slot number or the frame number is exceeded; the passive calculable RFID tag and the reader have the advantages that invalid communication between the passive calculable RFID tag and the reader is avoided, conflicts among the passive calculable RFID tags are reduced, and the transmission efficiency of the passive calculable RFID tag and the reader is improved.

Description

Passive computable RFID anti-collision method based on energy prediction
Technical Field
The invention relates to the technical field of radio frequency identification in wireless communication, in particular to a passive computable RFID anti-collision method based on energy prediction.
Background
Radio Frequency Identification (RFID) is a wireless communication technology that can identify a specific object and read and write related data by radio signals without establishing mechanical or optical contact between the identification system and the specific object. The RFID system mainly comprises an electronic tag, a reader, a back-end database, an antenna and the like. The RFID is divided into active RFID, semi-active RFID and passive RFID according to the power supply form of the electronic tag. Passive computable RFIDs (crfrids) are a class of passive RFIDs that employ ultra-low power microcontrollers to achieve wireless node sensing, computation, and communication by harvesting Radio Frequency (RF) energy. Unlike battery-powered active RFID systems, passive CRFIDs store the rf energy emitted by an inductive reader in a capacitor to perform sensor sensing, microcontroller calculations, and reverse link data transmission. Passive CRFIDs are capable of sensing, calculating, and storing, as opposed to merely identifying, as compared to conventional passive RFID systems.
In the use occasion of the RFID, generally, the tag stores the related information of the article, and then one reader is used to identify a plurality of tags in the occasion, that is, the relationship between the number of the readers and the number of the tags is generally one-to-many, so that tag collision is more likely to occur. The time slot anti-collision algorithm based on the time slot anti-collision algorithm and the time slot anti-collision algorithm based on the frame are anti-collision algorithms based on a Time Division Multiple Access (TDMA) technology, and are label anti-collision algorithms which are researched more mature at present. The Slot-based anti-collision algorithm is to divide a given transmission time period equally into a plurality of small time periods, which are called slots (slots), and each Slot is absolutely longer than the time T required for transmitting a data packet of a tag. And the time slot for each tag to transmit a data packet is controlled by the clock circuit of the RFID system. The time slot anti-collision algorithm based on the frame combines F time slots into a frame on the basis of the time slot anti-collision algorithm, and the label randomly selects one time slot in each frame to send data. When the reader generates an inquiry request signal, the tag activates itself by using the coupling current to respond to the request of the reader.
The anti-collision algorithm based on the TDMA technology assumes that once the tag communicates with the reader, the whole communication process can be successfully completed. For the passive CRFID, because sensing, calculation and reverse communication are needed, the energy consumption is large, when the charging time is short and the energy stored in the capacitor is small, the communication with the reader cannot be successfully completed at a high probability, the data transmission fails, the communication needs to be reestablished, the transmission overhead of the reader is greatly increased, and the collision between subsequent tags is greatly increased.
Disclosure of Invention
The passive calculable RFID tag and the reader have the advantages that invalid communication between the passive calculable RFID tag and the reader is avoided, conflicts among the passive calculable RFID tags are reduced, and the transmission efficiency of the passive calculable RFID tag and the reader is improved.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a passive computable RFID anti-collision method based on energy prediction comprises the following steps: the charging time required by the passive calculable RFID tag to successfully complete one-time data communication is converted into the time slot number or the frame number of the tag, the tag does not carry out any data communication with the reader within the time slot number or the frame number, and the reader carries out communication with the tag when the time slot number or the frame number is exceeded.
Preferably, the reader communicates with the tag by using a time slot-based anti-collision algorithm or a frame time slot-based anti-collision algorithm.
The preferred pre-test reader and passive calculable RFID tag have the energy E required for a successful data transmission and the distance D between the reader and passive calculable RFID tag, a relationship is established to calculate the required charging time Tcharge at this distance D.
By assuming that the reader and the passive system can calculate the data transmission time slot Tslot of the RFID tag, the charging time Tcharge required by the tag to successfully complete one data communication is converted into the time slot number or frame number of the tag.
The adopted specific technical scheme is as follows.
a) The method comprises the steps of testing the energy E required by a reader and a passive calculable RFID tag for successfully carrying out data transmission once in advance, calculating the distance D between the reader and the passive calculable RFID tag, and establishing charging time TchargeThe distance D is related to the energy E required to successfully complete a communication (Ӏ), and the charging time T required for the distance D is calculatedcharge。
Figure DEST_PATH_IMAGE001
Wherein the content of the first and second substances,
Figure 778251DEST_PATH_IMAGE002
the energy required for the tag and reader to successfully complete a communication,
Figure DEST_PATH_IMAGE003
the reader antenna is transmitting a wavelength of electromagnetic waves,
Figure 604255DEST_PATH_IMAGE004
is the distance between the tag antenna and the reader antenna,
Figure DEST_PATH_IMAGE005
in order to transmit power to the reader,
Figure 627706DEST_PATH_IMAGE006
in order to gain the antenna of the reader,
Figure DEST_PATH_IMAGE007
in order to gain the tag antenna,
Figure 357021DEST_PATH_IMAGE008
the transmission coefficient is 0 to 1,
Figure DEST_PATH_IMAGE009
the value is 0-1 for the polarization loss of the tag antenna,
Figure 407891DEST_PATH_IMAGE010
the value is 0 to 1 for the conversion efficiency of the charging circuit,
Figure DEST_PATH_IMAGE011
the charging time required for the tag and the reader to successfully complete one communication.
b) RFID tag data transmission time slot T can be calculated by assuming reader and passiveslotCharging time T required for the tag to successfully complete one-time data communicationchargeConverted to the slot or frame number for that tag.
c) And calculating the number of time slots or frames required by all passive calculable RFID tags to wait, and establishing a lookup table of the distance D and the number of waiting time slots or frames at the reader end.
d) According to the lookup table, the tag does not perform any data communication with the reader within the time slot number or the frame number, and the reader performs communication with the tag by adopting a time slot anti-collision algorithm or a frame time slot anti-collision algorithm if the time slot number or the frame number is exceeded.
Compared with the prior art, the invention has the following beneficial effects: according to the invention, the energy E required by successful data transmission of the reader and the passive calculable RFID tag is predicted, and the time slot number or the frame number required by the passive calculable RFID tag is finally obtained, so that the communication in the waiting time slot number or the frame number can not only cause invalid communication, but also cause conflict between the tags, and the communication is stopped in the waiting time slot number or the frame number, thereby avoiding the invalid communication between the passive calculable RFID tag and the reader, effectively reducing the conflict between the passive calculable RFID tag, and improving the transmission efficiency of the passive calculable RFID tag and the reader.
Detailed Description
The technical solutions of the present invention are described in detail below with reference to examples, but the scope of protection is not limited thereto.
Example 1
In the case of a small number of passive calculable RFID tags.
(1) The reader and the passive calculable RFID tag estimate the energy E required for a successful data transmission. (2) Establishing a charging time T under the condition that the distance D between the reader and the label is a fixed valuechargeDistance D is related to the energy E required to successfully complete a communication:
Figure 924455DEST_PATH_IMAGE012
wherein the content of the first and second substances,
Figure 282755DEST_PATH_IMAGE002
the energy required for the tag and reader to successfully complete a communication,
Figure 940612DEST_PATH_IMAGE003
the reader antenna is transmitting a wavelength of electromagnetic waves,
Figure 257324DEST_PATH_IMAGE004
is the distance between the tag antenna and the reader antenna,
Figure 854658DEST_PATH_IMAGE005
in order to transmit power to the reader,
Figure 718447DEST_PATH_IMAGE006
in order to gain the antenna of the reader,
Figure 452048DEST_PATH_IMAGE007
in order to gain the tag antenna,
Figure 939661DEST_PATH_IMAGE008
the transmission coefficient is 0 to 1,
Figure 289871DEST_PATH_IMAGE009
the value is 0-1 for the polarization loss of the tag antenna,
Figure 757017DEST_PATH_IMAGE010
the value is 0 to 1 for the conversion efficiency of the charging circuit,
Figure 876283DEST_PATH_IMAGE011
the charging time required for the tag and the reader to successfully complete one communication. The charging time T required at this distance D can be calculated from the relationcharge。
Suppose the reader and the tag data transmission time slot are TslotCarry out M = Tcharge/TslotAnd (5) calculating to obtain the time slot number M of the label needing to wait. And calculating the number of time slots required to wait by all the tags, and establishing a static lookup table of the distance D and the waiting time slot at the reader end.
In the case that the distance D between the reader and the tag is dynamically changed, first, the range of the distance change between all the tags and the reader is determined. Establishing a charging time TchargeA relation between the minimum value of the distance D and the energy E required for successfully completing one communication; establishing a charging time TchargeMaximum, distance dmax, and energy E required to successfully complete a communication. The charging time T required under the minimum value of the distance D can be calculated according to the relationminchargenAnd the charging time T required at the maximum value of the distance Dmaxmaxchargen。
Suppose the data transmission time slot of the reader and the tag is TslotCarry out Mmin=Tminchargen/TslotCalculating to obtain the minimum value M of the number of the time slots needing to waitmin(ii) a Carry out Mmax=Tmaxchargen/TslotCalculating to obtain the maximum value M of the number of the time slots needing to waitmax。
At MminAnd MmaxIn between, every other time slot, reverse-deducing to obtain the corresponding distance DiSo that different distances within the distance range can be obtainedA look-up table of leave and wait slots.
(3) According to the lookup table, the tag does not perform any data communication with the reader within the waiting time slot number, and the reader performs communication with the tag by adopting a time slot-based anti-collision algorithm when the waiting time slot number is exceeded.
Example 2
In the case of a large number of passive calculable RFID tags.
(1) The reader and the passive calculable RFID tag estimate the energy E required for a successful data transmission. (2) Establishing a charging time T under the condition that the distance D between the reader and the label is a fixed valuechargeDistance D is related to the energy E required to successfully complete a communication:
Figure 738060DEST_PATH_IMAGE012
wherein the content of the first and second substances,
Figure 841145DEST_PATH_IMAGE002
the energy required for the tag and reader to successfully complete a communication,
Figure 843474DEST_PATH_IMAGE003
the reader antenna is transmitting a wavelength of electromagnetic waves,
Figure 82825DEST_PATH_IMAGE004
is the distance between the tag antenna and the reader antenna,
Figure 381083DEST_PATH_IMAGE005
in order to transmit power to the reader,
Figure 705885DEST_PATH_IMAGE006
in order to gain the antenna of the reader,
Figure 514834DEST_PATH_IMAGE007
in order to gain the tag antenna,
Figure 343113DEST_PATH_IMAGE008
the transmission coefficient is 0 to 1,
Figure 77851DEST_PATH_IMAGE009
the value is 0-1 for the polarization loss of the tag antenna,
Figure 624370DEST_PATH_IMAGE010
the value is 0 to 1 for the conversion efficiency of the charging circuit,
Figure 234080DEST_PATH_IMAGE011
the charging time required for the tag and the reader to successfully complete one communication. The charging time T required at this distance D can be calculated from the relationcharge。
Suppose the data transmission time slot of the reader and the tag is TslotEach frame has n time slots, L = Tcharge/(n*Tslot) The number of frames that the tag needs to wait is obtained L. the number of frames that all tags need to wait is calculated, and a static lookup table of the distance D and the waiting frames can be established at the reader end.
In the case that the distance D between the reader and the tag is dynamically changed, first, the range of the distance change between all the tags and the reader is determined. Establishing a charging time TchargeA relation between the minimum value of the distance D and the energy E required for successfully completing one communication; establishing a charging time TchargeMaximum, distance dmax, and energy E required to successfully complete a communication. The charging time T required under the minimum value of the distance D can be calculated according to the relationminchargenAnd the charging time T required at the maximum value of the distance Dmaxmaxchargen。
Suppose the data transmission time slot of the reader and the tag is TslotEach frame having n slots, proceed Lmin=Tminchargen/(n*Tslot) Calculating to obtain the minimum value L of the number of frames to waitminProceed from Lmax=Tmaxchargen/(n*Tslot) Calculating to obtain the maximum value L of the waiting frame numbermax。
At LminAnd LmaxAnd performing reverse thrust every other frame number to obtain a corresponding distance DiThus, a look-up table of different distances and waiting frame numbers in the distance range can be obtained.
(3) According to the lookup table, the tag does not perform any data communication with the reader within the waiting frame number, and the reader performs communication with the tag by adopting a frame time slot-based anti-collision algorithm when the waiting frame number is exceeded.
While the invention has been described in further detail in connection with specific embodiments thereof, it will be understood that the invention is not limited thereto, and that various other modifications and substitutions may be made by those skilled in the art without departing from the scope of the invention, which is to be determined by the claims appended hereto.

Claims (2)

1. The passive calculable RFID anti-collision method based on energy prediction is characterized in that charging time required by a passive calculable RFID tag to successfully complete one-time data communication is converted into the time slot number or the frame number of the tag, the tag does not carry out any data communication with a reader within the time slot number or the frame number, and the reader carries out communication with the tag beyond the time slot number or the frame number; the method specifically comprises the following steps:
1) estimating the energy E required by the reader and the passive calculable RFID tag for successfully carrying out data transmission for one time;
2) establishing a charging time T under the condition that the distance D between the reader and the label is a fixed valuechargeDistance D is related to the energy E required to successfully complete a communication:
Figure FDA0002446596840000011
wherein E is the energy required by the tag and the reader to successfully complete one-time communication, lambda is the wavelength of the electromagnetic wave transmitted by the reader antenna, D is the distance between the tag antenna and the reader antenna, and P is the distance between the tag antenna and the reader antennarTransmitting power for the reader, GrFor reader antenna gain, GtTaking tau as transmission coefficient, taking 0-1, taking rho as polarization loss of the tag antenna, taking 0-1, taking η as conversion efficiency of the charging circuit, taking 0-1, and taking T as gain of the tag antennachargeCharging time required for the tag and the reader to successfully complete one-time communication; the charging time T required at this distance D can be calculated from the relationcharge；
Suppose the reader and the tag data transmission time slot are TslotBy doing so with M ═ Tcharge/TslotCalculating to obtain the time slot number M of the label needing waiting; calculating the number of time slots required to wait for all the tags, and establishing a static lookup table of the distance D and the waiting time slot at the reader end;
under the condition that the distance D between the reader and the tag is dynamically changed, firstly determining the distance change range between all the tags and the reader; establishing a charging time TchargeA relation between the minimum value of the distance D and the energy E required for successfully completing one communication; establishing a charging time TchargeMaximum, distance dmax and energy E required to successfully complete a communication; the charging time T required under the minimum value of the distance D can be calculated according to the relationminchargenAnd the charging time T required at the maximum value of the distance Dmaxmaxchargen；
Suppose the data transmission time slot of the reader and the tag is TslotCarry out Mmin＝Tminchargen/TslotCalculating to obtain the minimum value M of the number of the time slots needing to waitmin(ii) a Carry out Mmax＝Tmaxchargen/TslotCalculating to obtain the maximum value M of the number of the time slots needing to waitmax；
At MminAnd MmaxIn between, every other time slot, reverse-deducing to obtain the corresponding distance DiThus, a lookup table of different distances and waiting time slots in the distance range can be obtained;
3) according to the lookup table, the tag does not perform any data communication with the reader within the waiting time slot number, and the reader performs communication with the tag by adopting a time slot-based anti-collision algorithm when the waiting time slot number is exceeded.
2. The passive calculable RFID collision avoidance method based on energy prediction as claimed in claim 1, characterized in that the reader communicates with the tag using a slot-based collision avoidance algorithm or a frame slot collision avoidance algorithm.
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