CN104331679A - Radio frequency identification tag anti-collision method based on physical layer network coding - Google Patents
Radio frequency identification tag anti-collision method based on physical layer network coding Download PDFInfo
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Abstract
The invention provides a radio frequency identification tag anti-collision method based on physical layer network coding. According to the method, aiming at the problem that a multi-tag anti-collision method in radio frequency identification is low in read-write speed, a physical layer network coding through is introduced, multi-tag collision information discarded by the traditional anti-collision method is used for decoding the information of the tags which have not been read, so that interaction between a reader-writer and each tag is reduced, and identification speed of the plurality of tags is improved. Compared with the existing radio frequency identification tag anti-collision method, the invention applies physical layer network coding into the radio frequency identification tag anti-collision method, utilizes the multi-tag collision information discarded by the traditional anti-collision method to perform physical layer network coding operation with the read tag information to decode to obtain the information of the tag which have not been read, and thereby interaction between a reader-writer and each tag is reduced, and read-write speed of the plurality of tags by using the anti-collision method is improved.
Description
Technical field
The invention belongs to technical field of RFID, be specially the RFID tag anti-collision method of a kind of physically based deformation layer network coding, mainly be applicable to the conflict set recognition problem solving many labels in radio-frequency recognition system, physical-layer network coding thought is incorporated in RFID tag anti-collision method, based on binary tree search algorithm, utilize physical layer network coding technique, analyze and utilize the multi-label collision data message abandoned by classic method, improving radio-frequency recognition system to the recognition efficiency of multiple label.
Background technology
Radio-frequency (RF) identification (Radio Frequency Identification, RFID) technology is a kind of automatic identification technology.RFID does not need to be identified object and just can work in recognition object horizon range, has the features such as accuracy rate is high, reading distance, storage data volume is large, durability is strong.
Because RFID has obvious technical advantage, the various fields such as industrial automation, business automation, communications and transportation control and management are widely used at present: such as Hospital medical management; The vehicles such as automobile, train are monitored; Auto Express-way Toll Collector System; Managing system of car parking; Production line balance robotization; Safety is come in and gone out inspection; Warehousing management; The care of animal; Vehicle anti-theft, article anti-counterfeit etc.REID, as the important component part of technology of Internet of things, belongs to national strategy new industry, and it develops and applies significant.
A typical rfid system is made up of label, read write line, data process subsystem 3 parts, as shown in Figure 1.Label is made up of label antenna and label chip, preserves data message in label chip, i.e. electronic code information.Read write line is an embedded system, comprises the interfaces etc. such as radio frequency processing module, control module, the element be coupled with label, serial ports or Ethernet.
Realized the Space Coupling of radiofrequency signal between label and read write line by coupling element, in coupling channel, according to sequential relationship, realize the transmission of energy and the exchange of data.Read write line can be mutual by radio frequency signal and label, can read data from label, or will need the information write label being stored into label.The data message that read write line reads, by serial ports or the network equipment, is sent to the data process subsystem of rear end.Data process subsystem is connected with read write line, for receiving, stored tag information provide related service to upper application software.
The principle of work of rfid system is: read write line sends the radiofrequency signal of characteristic frequency by emitting antenna, when electronic tag enters effective perform region, produce induction current, thus acquisition energy, electronic tag is activated, and self coded message is sent by built-in rf antenna by electronic tag; Read write line receiving antenna receives the modulation signal sent from label, is sent to read write line signal processing module through antenna adjustments device, effective information is delivered to the process that back-end data processing subsystem carries out being correlated with after demodulation code; Data process subsystem, according to the identity of this label of logical operation identification, is made corresponding process for different settings and controls, and finally sends command signal control read write line and completes corresponding read-write operation.
For the data communication process of label to read write line, its working method comprises: when (1) label receives the radio-frequency (RF) energy of read write line, is namely activated and the data message stored to read write line retro-reflective label; (2), after label is activated, proceeds to data according to read write line instruction and send state or dormant state.In these two kinds of working methods, the former belongs to one-way communication, and the latter belongs to half-duplex bidirectional communication.
At present, collision problem is the major issue affecting rfid system result of use.The conflict of rfid system is divided into label collision and read write line to conflict two kinds.Read write line conflict refers to, label simultaneously in the effective coverage of multiple read write line, the signal that label responds a read write line receive by another neighbours' read write line.Label collision refers in the identification range of read write line, has multiple label to send response signal at synchronization to read write line, then the signal of communication of these labels will superpose mutually, causes interference and conflict, as shown in Figure 2.What the present invention mainly studied and solved is the tag collision problems shown in Fig. 2.
Due in rfid system, the processing power of label is generally limited, and the anti-collision method of label substantially all adopts time division multiple access (TDMA) TDMA (Time Division Multiple Access) method.At present, mainly contain the label anti-confliction method that two classes utilize TDMA technology: (1) random tags anti-collision algorithms, mainly based on Aloha algorithm; (2) determinacy label anti-confliction algorithm, mainly based on Binary tree search method.
Random tags anti-collision algorithms is a kind of algorithm based on probability, and by creating time difference contention-free, algorithm is simple, but easily occurs that phenomenon " died of hunger " by label, and causing cannot to the identification completely of all labels.Determinacy label anti-confliction algorithm is a kind of deterministic algorithm, is bound to identify all labels, but the tag reading time of this algorithm is usually longer.The present invention is based on Binary tree search method, belong to a kind of determinacy label anti-confliction algorithm.
Above two class label anti-confliction methods all belong to time division multiple access method, final purpose guarantees that each label is is correctly read and write by read write line separately, and in algorithm implementation, the conflicting information that multiple label sends information generation is directly dropped simultaneously, and be not fully utilized.Therefore existing label anti-confliction method performance is more or less the same, and tag read efficiency is lower.
Network coding technique, forwards after allowing the intermediate node in network to encode to the data received, and multicast transmission speed can be made to reach, and theoretical upper limit that max-flow min-cut determines becomes possibility, and its encoding operation carries out in network layer.Physical-layer network coding is then carry out data union operation in Physical layer, utilize electromagnetic superimposed characteristics, regard radio magnetic wave the merging process of signal as in the superposition naturally in space, be namely equivalent to the network code process of Physical layer, obtain information needed at receiving end by decoding.
In rfid system, when multi-label collision occurs, collision signal is the superposition of multiple label signal, just a kind of physical-layer network coding computing.But traditional radio-frequency (RF) tag anti-collision method, all abandons this collision signal, and does not make full use of the information wherein comprised.The technical characterstic of physical-layer network coding, the collision problem produced when making it be suitable for the answer signal superposition processing many labels in rfid system.
Summary of the invention
Technical matters: the present invention proposes the RFID tag anti-collision method of a kind of physically based deformation layer network coding.Compared to existing RFID tag anti-collision method, its singularity and novelty are, the method introduces physical layer network coding technique, use abandoning no many label superposition conflicting informations in classic method, analyze and utilize useful information wherein, improve radio-frequency recognition system to the recognition speed of many labels and computing overhead, solve the problem that existing RFID tag anti-collision method is low to many tag recognition efficiency, expense is large.
Technical scheme: the RFID tag anti-collision method that the present invention is based on physical-layer network coding, physical-layer network coding is incorporated in RFID tag anti-collision method, analyze and utilize the conflicting information abandoned by traditional anti-collision method, improve tag recognition efficiency, specifically comprise the following steps:
Step a. initialized reference sequence number, by it, each is set to 1, and the sequence number of such as electronic tag is 8, then reference sequences number is initialized as 11111111, and it is 0 that initialization retreats variable i.
Step b. read write line performs read request command REQ (REQuset), and in selected set of tags, tag serial number is less than or equal to the electronic tag response of reference sequences number, and passes the sequence number of this label back.
Step c is according to Manchester code coding principle, read write line carries out demodulation to the received signal, whether decoding also detects and clashes: if the front semiperiod of certain code element and later half cycle are all non-zero level, then show that this code element produces conflict, by conflict restituted signal corresponding for this collision signal press-in conflict restituted signal storehouse, then the highest conflict bit is found out, the highest conflict bit of decoded signal is set to 0, 1 is set to lower than this, remaining unchanged higher than this, then in this, as the canonical sequence number of request command REQ next time, perform step b, if the front semiperiod of each code element and second half interim, one of them is high level, and another one is low level, then do not produce conflict, and read write line can identify the information of this label, perform steps d.
Steps d. to the label chosen, read write line performs sense data order RD-DATA (ReaD-Data) to be carried out reading tag data and preserves, and then performs and removes select command UNSEL (UNSELect), make label enter " dormancy " state.
Step e. judges whether conflict restituted signal storehouse is empty, if be empty, represent that all label informations obtain all, then algorithm terminates.Otherwise the conflict restituted signal that the label data read and restituted signal storehouse stack top of conflicting store is done subtraction by read write line, perform i=i+1 computing: if conflict free coded signal cannot be obtained, namely there is conflict all the time in operation result, performs step f; As conflict free coded signal can be obtained, then obtain 1 non-reading tag information, this label information is stored, then read write line performs and removes select command UNSEL, make this label enter " dormancy " state, the stack top element of conflict restituted signal storehouse is popped, and repeats step e; If obtaining signal is full low level, shows that the information of all labels in this collision signal has all been decoded and obtain, conflict restituted signal storehouse stack top element is popped, repeat step e.
I, using i-th read write line reciprocal and the label reference sequences used alternately canonical sequence number as request command REQ next time, is re-set as 0, then performs step g by step f..
Step g. return step b, until identify all labels.
Beneficial effect: the RFID tag anti-collision method that the present invention proposes a kind of physically based deformation layer network coding, the method tool has the following advantages:
(1) physical-layer network coding is introduced, the multi-label collision data analyzed and utilize conventional radio frequency identification label anti-collision method to abandon, thus reduce read write line to the number of times needed for many tag reader, improve radio-frequency recognition system to the reading rate of many labels, save energy;
(2) this inventive method has good extensibility and adaptivity, can be applicable to the radio-frequency recognition system of various frequency range, various energy method of supplying.
Accompanying drawing explanation
Fig. 1 is radio-frequency recognition system theory of constitution figure.
Fig. 2 is radio-frequency (RF) identification multi-label collision schematic diagram.
Fig. 3 is radio-frequency (RF) identification many label information superpositions conflict exemplary plot.
Fig. 4 is the RFID tag anti-collision method processing flow chart of physically based deformation layer network coding.
Fig. 5 is the exemplary plot of the RFID tag anti-collision method of physically based deformation layer network coding.
Embodiment
Existing RFID tag anti-collision method, need to guarantee to only have a label to send data to avoid conflict, and the superposition of data that multiple label sends data generation is simultaneously dropped as conflicting information at every turn.This method, have ignored the multiple labels be dropped and sends useful information implicit in the superposition of data of data generation simultaneously, add the number of times of tag recognition, reduce tag recognition speed.Object of the present invention is mainly for the tag collision problems of radio-frequency (RF) identification, the RFID tag anti-collision method of a kind of physically based deformation layer network coding is proposed, utilize physical layer network coding technique, analyze and utilize the information of colliding data that abandons by classic method, reduce the number of times of tag recognition, improve radio-frequency recognition system to the speed of many tag recognition.
The RFID tag anti-collision method of physically based deformation layer network coding of the present invention, based on binary search algorithm, the modulation system selecting range modulation of the information communication between label and read write line, coding mode selection Manchester code is so that find conflict, be used for memory conflict information at read write line internal maintenance collision message storehouse, mainly comprise following content:
(1) conflict finds
In the present invention, the information coding of label adopts the Manchester code being easier to find mistake.Corresponding to information code element 1, before Manchester code code element, the semiperiod is 1, and the later half cycle is 0.Corresponding to information code element 0, before Manchester code code element, the semiperiod is 0, and the later half cycle is 1.The code element that every information that tag memory stores up is corresponding, is called information code element.Information code element, after Manchester code coding, is called code symbols.
After being used by label information Manchester code to encode, label also will carry out amplitude modulation(PAM) to these data.Corresponding to 1, the amplitude of being modulated to is the sine wave signal of unit 1.Corresponding to 0, be modulated to low level.Signal after amplitude modulation(PAM), is called modulation signal.Modulation signal sends to read write line by label.
Therefore, when the modulation signal of n label is at space overlapping, can judge whether to clash by the coding rule of the amplitude and Manchester code that judge superposed signal: if in certain code-element period, the front semiperiod is zero level, the sine wave signal of the later half cycle, to be amplitude be n, superposed signal then in this code-element period is all obtained by the modulation signal of the label of 0 superposes by n information code element, shows that this code element is not conflicted generation; If in certain code-element period, the sine wave signal of the front semiperiod, to be amplitude be n, the later half cycle is zero level, then the superposed signal in this code-element period, be all obtained by the modulation signal of the label of 1 superposes by n information code element, show that this code element is not conflicted generation; Modulation signal superposition in other situations, shows that this code element there occurs conflict.
When Fig. 3 gives 3 tag modulates Signal averaging, there is the example of label collision.
(2) conflicting information stores
Can be found by Fig. 3, tag modulates Signal averaging is generally that partial symbols clashes, and other code element information do not clash.Traditional RFID tag anti-collision method, directly abandons this superposed signal, thus lost the information of code element of wherein not conflicting, and does not make full use of it.
In addition, can find from Fig. 3, if after the information correctly obtaining any 2 labels in 3 labels, by the coded signal of the restituted signal of superposed signal and these 2 labels is done subtraction, directly can obtain the information of residue 1 Unknown Label, and without the need to mutual with this Unknown Label again, thus the interaction times of read write line and label can be reduced, accelerate read-write speed.In like manner, if the modulation intelligence superposition of n label, and to clash, then the restituted signal of this superposed signal can store, so that after the information correctly obtaining n-1 label, obtained the information of last 1 Unknown Label by computing.
For this reason, this superposition solution tonal signal, after each discovery one comprises the superposition solution tonal signal of conflict, is stored in storehouse by the present invention, used in order to decoding below.This storehouse is called conflict restituted signal storehouse.
(3) single label correctly reads:
If certain read write line and label mutual in, not conflict in the response message that label returns to read write line, show only there is a label return data, then read write line will directly read this label information, and preserve in its memory.
(4) conflicting information decoding
Read write line is after the information of each correct reading 1 label, the conflict restituted signal that conflict restituted signal storehouse stack top stores can be popped, and do subtraction with the coded signal of the multiple labels read, as Lothrus apterus signal can be obtained, show that this Lothrus apterus signal is the information of a non-reading tag, namely obtain by Physical layer decoding the information that 1 is not read label, thus decrease the interaction times between read write line and label, accelerate the recognition rate of label.
The process flow diagram of the RFID tag anti-collision method of physically based deformation layer network coding as shown in Figure 4, further describes technical scheme of the present invention and method flow below by a concrete example, as shown in Figure 5.
Now in radio-frequency recognition system, there is a read write line, have 4 labels within the scope of the read-write of read write line: Tag1, Tag2, Tag3, Tag4.The information of each label is respectively Tag1:10110010, Tag2:10100011, Tag3:10110011, Tag4:11100011.
(1) initial reference sequences number is 11111111, read write line performs request command REQ, all tag responses also return sequence number, read write line obtains 1X1X001X (wherein X represents conflict bit) according to the decoding of Manchester code coded system, show to clash, by the conflict restituted signal information of correspondence press-in conflict restituted signal storehouse.The 6th of decoding is the highest conflict bit, by the 6th position 0, puts 1 lower than this, remains unchanged, be 10111111, as the canonical sequence number in REQ order next time higher than this position.
(2) be set to 10111111 with reference to sequence number, read write line performs request command REQ, and Tag1, Tag2, Tag3 reply and return their sequence number, and Tag4 does not reply.Read write line obtains 101X001X according to the decoding of Manchester code coded system, shows to clash, by the conflict restituted signal information of correspondence press-in conflict restituted signal storehouse.The 4th of decoding is the highest conflict bit, by the 4th position 0, puts 1 lower than this, remains unchanged, be 10101111, as the canonical sequence number in REQ order next time higher than this position.
(3) be set to 10101111 with reference to sequence number, read write line performs request command REQ, only has Tag2 to reply and returns its sequence number.Be decoded as 10100011, do not produce conflict, Tag2 is identified by read write line, and read write line communicates with, and makes it enter " dormancy " state.Read write line, by the information of Tag2 label, does subtraction with the signal of the restituted signal storehouse stack top element that conflicts, and finds that result still has conflict, cannot be correctly decoded.Then the canonical sequence number of request command REQ is next time obtained from father node, namely 10111111.
(4) 10111111 are set to reference to sequence number, read write line performs request command REQ, Tag2 is in " dormancy ", and state is not replied, Tag1, Tag3 reply, read write line obtains 1011001X according to the decoding of Manchester code coded system, show to clash, by the conflict restituted signal information of correspondence press-in conflict restituted signal storehouse.The 0th of decoding is the highest conflict bit, and by the 0th position 0, put 1 lower than this, remaining unchanged higher than this position, be 10110010, is the canonical sequence number in REQ order next time.
(5) be set to 10110010 with reference to sequence number, read write line performs request command REQ, only has Tag1 to reply and returns its sequence number.Be decoded as 10110010, do not produce conflict, Tag1 is identified by read write line, and read write line communicates with, and makes it enter " dormancy " state.Read write line, by the information of Tag1 label, does subtraction with the signal of the restituted signal storehouse stack top element that conflicts, and finds that decoding obtains the information of Tag3 label, and conflict restituted signal storehouse stack top element is popped.Then Tag3 is that read write line decoding identifies, read write line communicates with, and makes it enter " dormancy " state.By the information of Tag1, Tag2, Tag3, do subtraction with the signal of the restituted signal storehouse stack top element that conflicts, result is full low level, is popped by this stack top element.By the information of Tag1, Tag2, Tag3, do subtraction with the signal of the restituted signal storehouse stack top element that conflicts, find that decoding obtains the information of Tag4 label.So far, the information of all labels all correctly obtains.
Claims (1)
1. the RFID tag anti-collision method of a physically based deformation layer network coding, it is characterized in that, physical-layer network coding is introduced in RFID tag anti-collision method by the method, utilize the conflicting information abandoned by traditional anti-collision method, improve tag recognition efficiency, the method comprises the following steps:
Step a. initialized reference sequence number, by it, each is set to 1, and the sequence number of such as electronic tag is 8, then reference sequences number is initialized as 11111111, and it is 0 that initialization retreats variable i;
Step b. read write line performs read request command REQ, and in selected set of tags, tag serial number is less than or equal to the electronic tag response of reference sequences number, and passes the sequence number of this label back;
Step c. according to Manchester code coding principle, read write line carries out demodulation to the received signal, whether decoding also detects and clashes: if the front semiperiod of certain code element and later half cycle are all non-zero level, then show that this code element produces conflict, by conflict restituted signal corresponding for this collision signal press-in conflict restituted signal storehouse, then the highest conflict bit is found out, the highest conflict bit of decoded signal is set to 0, 1 is set to lower than this, remaining unchanged higher than this, then in this, as the canonical sequence number of request command REQ next time, perform step b, if the front semiperiod of each code element and second half interim, one of them is high level, and another one is low level, then do not produce conflict, and read write line can identify the information of this label, perform steps d,
Steps d. to the label chosen, read write line performs sense data order RD-DATA to be carried out reading tag data and preserves, and then performs and removes select command UNSEL, make label enter " dormancy " state;
Step e. judge whether conflict restituted signal storehouse is empty, if be empty, represent that all label informations obtain all, then algorithm terminates, otherwise the conflict restituted signal that the label data read and restituted signal storehouse stack top of conflicting store is done subtraction by read write line, perform i=i+1 computing: if cannot obtain conflict free coded signal, namely operation result exists conflict all the time, perform step f; As conflict free coded signal can be obtained, then obtain 1 non-reading tag information, this label information is stored, then read write line performs and removes select command UNSEL, make this label enter " dormancy " state, the stack top element of conflict restituted signal storehouse is popped, and repeats step e; If obtaining signal is full low level, shows that the information of all labels in this collision signal has all been decoded and obtain, conflict restituted signal storehouse stack top element is popped, repeat step e;
Step f. using i-th read write line reciprocal and the label reference sequences used alternately canonical sequence number as request command REQ next time, i is re-set as 0, then performs step g;
Step g. return step b, until identify all labels.
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