CN102024134A - High-efficiency multi-tag anti-collision radio frequency identification (RFID) method - Google Patents

Abstract

The invention discloses a high-efficiency multi-tag anti-collision radio frequency identification (RFID) method, which mainly comprises a tag division process and a tag searching process. An ALOHA frame or other signal frames are established in the tag division process; and in the tag division process, time slots are randomly selected for tags to transmit IDs, and function in dividing a tag group consisting of all the tags in the range of a reader-writer into a plurality of independent small tag groups. In the tag searching process, a plurality of message frames are involved; and each frame corresponds to a specific collision time slot in the tag division process, and in the frame, the tags can be identified one by one by a backtracking binary-tree searching method and the like. The method can greatly reduce collision phenomena in a multi-tag identification process and reduce times of information interaction between the tags and the reader-writer, and ensures high efficiency and security.

Description

The recognition methods of a kind of efficient RFID multiple labels anti-collision

Technical field

Technology is avoided in the collision that the present invention relates in a kind of wireless communication procedure, relates in particular to radio-frequency (RF) identification (RFID) multiple labels anti-collision and quick identification technology.

Background technology

(Radio Frequency Identification, RFID) collision problem of system is divided into read write line collision and label collision to radio-frequency (RF) identification.Effective perform region of contiguous a plurality of read write lines is if exist overlapping, two or more read write lines are discerned a label or during data read-write operation simultaneously, may cause label can't correctly discern the read write line instruction, thereby the phenomenon that can't make correct response is referred to as the read write line collision.There are a plurality of labels in certain read write line perform region, and two or more labels are arranged, and instruction responds to read write line in same time slot, thereby produce the signal stack at the read write line receiving end, cause read write line correctly the phenomenon of identification tag responses signal be called label and collide.

At present, the RFID technology is as one of crucial identify label technology of Internet of Things, the gate inhibition, warehousing management, production line, the logistics transportation, small amount payment, the location waits the social life every field to obtain using extremely widely with tracking, and the picture logistics supply chain management, warehousing management, often need simultaneously a large amount of destination objects to be discerned in exhibition center/application such as people from museum flow monitoring, and the simple passive RFID tags of function itself does not have the ability that detects conflict and find adjacent label, and therefore setting up perfect label anti-collision agreement in the communication process of rfid system just seems most important.

The label anti-collision agreement mainly is divided into two classes: stochastic pattern anti-collision algorithm (based on the anti-collision algorithm of ALOHA) and definite type anti-collision algorithm (based on the anti-collision algorithm of binary tree).Based on the label anti-collision algorithm of ALOHA for example ALOHA algorithm, time slot A LOHA algorithm, frame slot ALOHA algorithm, dynamic frame length ALOHA algorithm etc., all be by reducing the speed that probability that the label collision takes place improves many tag recognition.Efficient is higher in the ALOHA class algorithm should be dynamic frame length ALOHA algorithm, as the used Q algorithm of EPCglobal C1G2 standard both had been such algorithm, read write line is set up the Frame of a regular length by the broadcasting particular command, label can select arbitrary time slot to send response at random, if having the label response, certain time slot then is not empty slot, if this label is correctly validated to have only a label to respond then, if there are a plurality of label responses then to bump, read write line is by the empty slot in this frame of statistics, single label response time slot, the quantity of collision time slot is used as the length of parameter adjustment Next Command frame, do not have the collision time slot in certain identification frame, both all labels all were identified.The binary tree search algorithm by the tandom number generator of label inside produce at random " 0 " and " 1 " will produce the collision population of tags constantly be subdivided into two sub-population of tags, when one of them subtab group only comprises a label, read write line just can correctly be discerned this label, so repeatedly, all be identified up to all labels.Studies show that, when number of labels more for a long time, the efficient of these two kinds of methods all is quite low.

The major defect of existing RFID multi-label anti-collision algorithm is: the efficient of ALOHA class algorithm relies on the prediction of number of labels very much, when its identification frame length when equating with number of labels to be identified, the high workload efficient of its theory can be near 1/e (≈ 36.8%) label/time slot.In addition, ALOHA class algorithm is very unsettled, and can there be bigger fluctuation in the repeatedly recognition result of same quantity label, and especially more when number of labels, when read write line can't accurately be predicted number of labels, its algorithm performance will obviously descend.In the evolution algorithmic of binary tree class, recoverable query tree algorithm is most effective a kind of, this algorithm is that (2M-1) is inferior to the identification number of times of M label, when number of labels more for a long time can be near 50% label/time slot, yet under the more situation of label, collide in order to handle a large amount of labels, read write line is had to repeatedly send label ID number and is come the splitting label group, the potential danger that has caused label information to reveal like this.

Therefore, the invention discloses a kind of RFID multi-label anti-collision method that is different from existing stochastic pattern and definite type, proposed a kind of new more efficient and safe many tag recognition of RFID algorithm structure.

Summary of the invention

At the problems referred to above, the object of the present invention is to provide a kind of new many label identification methods of more efficient, safe radio-frequency (RF) identification.The basic design of this method is: the communication process of rfid interrogator being discerned many labels is divided into label cutting procedure and two stages of label search procedure, at first cut apart frame by the label of setting up a length-specific, label selects a time slot to send response in this frame at random, the population of tags random division that to form by all labels that are in the effective perform region of read write line and a plurality of population of tags of not being combined into of composition again by small numbers of tags, select little population of tags one by one by select command then, label among the group is searched for, and then finished identifying all labels.Theoretical analysis proves, this method can improve the recognition efficiency of label greatly, and can reduce the repeated communications number of times that the label search procedure is carried out in one's power to same label greatly by big population of tags being divided into the method for carrying out the label search after a plurality of little population of tags again, reduce the system information disclosure risk.Rfid system is to the data manipulation (read/write operation) of certain label, can successfully be carried out immediately after the identification at this label, also can all discern at all labels selects this label to operate separately by read write line after finishing, this data read-write operation does not exert an influence to the anticollision process of label, does not become restriction of the present invention yet.

According to purpose of the present invention, radio-frequency (RF) identification multiple labels anti-collision process comprises label cutting procedure and two stages of label search procedure.Label is cut apart the stage and is comprised step:

1, read write line sends Select command selection specific label group and carries out identifying operation, and this step can not done, and all will not participate in subsequently identifying if do not make all labels in the read write line efficient working range then;

2, read write line sends the Query order and sets up a label and cut apart frame, comprises parameter--the N of this frame tagging response number of timeslots of indication in the Query command format;

3, label correctly receives Query order back and obtains timeslot number N, and the tandom number generator of label inside produces a random number (n, 0≤n＜N), save as the time slot mark symbol; Label only sends response signal at its selected time slot,

Be generally label ID information,, all keep mourning in silence at every other time slot no matter whether bump; Three kinds of possibility situations can appear at each label response time slot:

1, this time slot does not have label to send response signal, is empty slot, and then read write line is waiting for that the no label response of special time affirmation back sends the NextSlot order, enters next time slot operations;

2, if having only a label to send response, then this label is successfully discerned, and read write line sends the NextSlot order equally, enters next time slot operations;

3, if there are a plurality of labels to send response, then bump at the read write line receiving end, system can not discern arbitrary label, and then read write line deposits this timeslot number in collision time slot tabulation { T _k, and send the NextSlot order, enter next time slot operations;

The purpose of label search phase is that label is cut apart the small numbers of tags that is comprised in each collision time slot in the frame to be discerned one by one, the realization of concrete label searching method can have various ways, for example use the searching method of label ID prefix, or produce " 0 " and " 1 " splitting label group method etc. at random by label.The specific implementation method will be set forth in conjunction with inventive embodiments in " embodiment " part.

Technique effect of the present invention is: 1) based on the higher binary tree search basic idea of relative work efficiency, introduce label and cut apart frame, population of tags in the read write line working range is carried out based on equally distributed random division, thereby obtain a plurality of independently little population of tags, greatly dwindled the scope of each label search, reduce the collision frequency of the required experience of the final identification label of read write line, improved recognition efficiency, strengthened Information Security; 2) through theoretical analysis with based on the Matlab simulating, verifying of monte carlo method, multiple labels anti-collision recognition efficiency of the present invention has been broken through the restriction of traditional ALOHA algorithm and binary tree search algorithm, has realized a new height; 3) the present invention has broken through traditional algorithm for the quantitative limitation of many number of tags, is applicable to the quick identification to a large amount of labels.

Description of drawings

Fig. 1 (a) represents label to be identified in the specific embodiment of the present invention and the tag tree that is constituted thereof

The label cutting procedure of Fig. 1 (b) expression specific embodiment of the present invention

The label search procedure of Fig. 1 (c) expression specific embodiment of the present invention

Fig. 2 represents the employed Manchester's cde method of a specific embodiment of the present invention

Fig. 3 represents that the optimal performance condition of a specific embodiment of the present invention finds the solution

Fig. 4 represents the performance simulation result of a specific embodiment of the present invention when the varying number label is discerned

Fig. 5 represents the performance simulation result of a specific embodiment of the present invention when 100 labels are repeatedly discerned

Embodiment

Below by preferred embodiment in conjunction with the accompanying drawings, describe the present invention, but be not construed as limiting the invention.

One, principle of work of the present invention

In many tag recognition of RFID process, can be by selecting a kind of suitable coding method to identify the accurate character position that a plurality of label response messages bump to the data transmission of reader for label.Manchester (Manchester) coding can satisfy such condition.As shown in Figure 2, the Manchester coding is that a certain position is represented in the change (rising/negative edge) that is used in the level in the position window.The data bit that sends simultaneously when a plurality of labels has different values, and then rising edge of Jie Shouing and negative edge are cancelled out each other, so that " does not change " within the window of some positions, therefore accurate position that in this way can conflict of qualification.The embodiment of the invention will adopt the Manchester coding.

It is L that the label of the embodiment of the invention is cut apart frame length, promptly is made of L label response time slot, and label is equally distributed in cutting apart frame, so the probability P that label responds on any time slot in frame can be expressed as:

P＝1/L (1)

Then, label is cut apart the probability P that r label response arranged on certain time slot in the frame _rCan calculate by (2) formula.

$P_r=L^{-N}\left(\begin{array}{c}r\\ N\end{array}\right){(L-1)}^{N-r}---\left(2\right)$

When r 〉=2, owing to adopted Manchester's cde, r label on this collision time slot will be discerned by the label search procedure in the k frame of back one by one, and the required timeslot number of this search procedure is

L(k，r)＝2(r-1)r≥2(3)

(N L) can be expressed as (4) formula to throughput U when therefore, using the embodiment of the invention that N label discerned.

U(N，L)＝N/[L+B(N，r)] (4)

Wherein

$B(N,r)=L\left[\underset{r=2}{\overset{N}{\mathrm{\Σ}}}\left(\begin{array}{c}r\\ N\end{array}\right){\left(\frac{1}{L}\right)}^r{(1-\frac{1}{L})}^{N-r}2(r-1)\right]---\left(5\right)$

$=\underset{r=2}{\overset{N}{\mathrm{\Σ}}}\underset{i=0}{\overset{N-r}{\mathrm{\Σ}}}\left(\begin{array}{c}r\\ N\end{array}\right)\left(\begin{array}{c}i\\ N-r\end{array}\right){(-1)}^{N-r-i}{\left(\frac{1}{L}\right)}^{N-i-1}2(r-1)$

Fig. 3 be the embodiment of the invention the throughput function U (N, L) along with label is cut apart the curve that the ratio L/N of frame length and number of labels changes, red curve is a result of calculation, blue curve is a simulation result, simulation result is the average of 100 identifyings.As can be seen from the figure, when L/N ≈ 0.6, (U (N, L)) ≈ 0.62 label/time slot is higher than the efficient of traditional ALOHA algorithm and binary tree search algorithm far away to obtain Max.And Fig. 3 demonstration, N is big more, and the simulation result curve is level and smooth more, illustrates when number of labels is more, and the result of the each identification of the embodiment of the invention is very approaching, and is bad unpredictable in the time of can not looking like stochastic pattern arithmetic result fashion.

Two, implementation step of the present invention is described in conjunction with the preferred embodiments

This part (is illustrated in figure 1 as T by the preferred embodiments of the present invention to 8 labels ₀, T ₁, T ₂, T ₃, T ₄, T ₈, T ₁₀, T ₁₅) process discerned sets forth the present invention.The ID of 8 labels constitutes the leaf node on the tag tree as shown in Figure 1.This algorithm requires read write line to use a two-dimensional storage space M, and { T, SID}, T are the timeslot number vector that bumps, the label mixing id information that SID receives for read write line on the corresponding collision time slot.

The label cutting procedure is:

1) read write line sends the Query order, and the label that to set up a length be L is cut apart frame, and waits for that the label response is (in this example, L=8).All labels of receiving the read write line communication request obtain the present frame length L by resolving the read write line order, and produce a random number k that is not more than L (0≤k≤L), be that label will send its id information at k time slot of present frame, label is stored in this k value in the tag ram simultaneously.As shown in Figure 2, by monte carlo simulation methodology, read write line will obtain following information in this frame: time slot S ₁, S ₄Be empty slot, do not have the label response; Time slot S ₂, S ₅, S ₆, S ₇A label response is arranged, the label T on these four time slots respectively ₀, T ₁, T ₄, T ₈Successfully discerned by read write line; And time slot S ₀And S ₃On have label collision.Read write line will collide timeslot number and write the M space, at this moment

$M=\{\left[\begin{array}{c}0\\ 3\end{array}\right],\left[\begin{array}{c}\mathrm{xx}1x\\ x01x\end{array}\right]\}$

2) because present embodiment has adopted Manchester's cde, the bit that specifically bumps can effectively be differentiated by system, so the SID in the M space can equivalence be

$\mathrm{SID}=\left\{\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="SID"\; filenames="HSA00000320532400012.png,HSA00000320532400022.png"\; state="\{\{state\}\}">SID</figure-callout>}}_1\\ \mathrm{SI}{D}_2\end{array}\right\}=\left\{\begin{array}{c}\left[\begin{array}{c}\mathrm{0,00,0010}\\ \mathrm{0,00,0011}\\ \mathrm{0,01,0110}\\ \mathrm{0,01,0111}\\ \mathrm{1,10,1010}\\ \mathrm{1,10,1011}\\ \mathrm{1,11,1110}\\ \mathrm{1,11,1111}\end{array}\right]\\ \left[\begin{array}{c}\mathrm{0,0010}\\ \mathrm{0,0011}\\ \mathrm{1,1010}\\ \mathrm{1,1011}\end{array}\right]\end{array}\right\}$

The label search procedure can be passed through accomplished in many ways, and the simplest a kind of searching method of answering top down is:

1) read write line sends Query (T (1), SID ₁₁₁) instruction, wherein T (1) is the 1st element in the collision timeslot number vector, SID ₁₁₁For searching for first first element of row of the ID prefix matrix that needs transmission to label on the corresponding time slot of T (1).In the present embodiment, the parameter that first Query order that read write line sent after the label search procedure began comprises is (0,0).

2) label receives that relatively T (1) whether and oneself to cut apart the time slot of selecting in the frame at label consistent, SID in read write line instruction back ₁₁₁Whether consistent with the preceding i position of the ID of oneself, if k=T (1) and Prefix (ID, i)=SID ₁₁₁, then label sends the ID response; If k ≠ T (1) or Prefix (ID, i) ≠ SID ₁₁₁, then label does not respond.

Among Fig. 3, when read write line sends first Query instruction Query (0,0), has only label T ₂Satisfy condition, promptly have only T ₂Send id information, so T ₂Successfully discerned by read write line.

2 kinds of possibility situations will appear this moment:

A) have only 1 label to send response message, then read write line is correctly discerned this label, and SID in the deletion M space ₁First the row all elements, at this moment

I. if SID ₁Be not empty, then continue 1) step;

Ii. if SID ₁Be sky, then delete T (1) and SID ₁, if M is then identifying end of sky, if M does not then continue 1 for sky) and step.

B) if there are a plurality of labels to send response message, the label collision takes place promptly, then SID in the read write line deletion M space ₁In first element of first row, continue 1) step.

The above; only be one embodiment of the present invention, but protection scope of the present invention is not limited thereto, anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.

Claims (7)

1. the invention discloses the recognition methods of a kind of efficient RFID multiple labels anti-collision, mainly comprise two parts based on the signaling procedure of the many tag recognition of RFID of this method: label cutting procedure and label search procedure.

(1) label cutting procedure comprises step:

A) read write line sends command selection specific label group and carries out identifying operation, and this step can not done yet, and is not in label in the read write line efficient working range and all will participates in subsequently identifying if do not do then all;

B) read write line sends order and sets up a label and cut apart frame, comprises the parameter of this frame tagging response number of timeslots of indication in this command format;

C) label obtains the present frame number of timeslots after correctly receiving the read write line order, and the tandom number generator of label inside produces a random number (n, 0≤n＜N), save as the time slot mark symbol; Label only sends response signal at its selected time slot, is generally label ID information;

(2) purpose of label search procedure is that label is cut apart the small numbers of tags that is comprised in each collision time slot in the frame to be discerned one by one, the realization of concrete label searching method can have various ways, for example use the searching method of label ID prefix, or produce " 0 " and " 1 " splitting label group method etc. at random by label.

2. label cutting procedure as claimed in claim 1 can be ALOHA frame or other signal frames of a suitable length, label selects a time slot to send corresponding identify label signal at random in this process, can be user's unique identifier (UUID), label unique identifier (TUID) etc., it act as the population of tags that all labels in the read write line scope are constituted and is divided into several separate little population of tags, as shown in Figure 1.

3. label dividing method as claimed in claim 2 is characterized in that: in the label cutting procedure, directly successfully do not discerned by read write line because of bumping when the part label sends response message.

4. the length that label as claimed in claim 2 is cut apart frame is suitably chosen according to number of labels to be identified can the optimized Algorithm performance.

5. the present invention as claimed in claim 1 is characterized in that: can be used in combination with the respective labels quantitative forecasting technique, obtain number of tags to be identified by the label prediction and estimate before the inventive method is implemented, and set the length that label is cut apart frame with this.The label that studies show that the preferred embodiment of the present invention is cut apart label response number of timeslots that frame comprises when being 0.6 times total number of labels, algorithm performance the best.

6. label search procedure as claimed in claim 1 can be made up of a plurality of message frames, a collision time slot in each frame corresponding label cutting procedure can be by the one by one identification of accomplished in many ways such as recoverable binary tree search, inquiry binary tree search to label in this frame.

7. as claim 1 or the described method of claim 4, it is characterized in that: based on the higher binary tree search basic idea of relative work efficiency, introduce label and cut apart frame, population of tags in the read write line working range is carried out based on equally distributed random division, thereby obtain a plurality of independently little population of tags, greatly dwindled the scope of each label search, reduced the collision frequency of the required experience of the final identification label of read write line, improve recognition efficiency greatly, strengthened Information Security.

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