CN100405775C - Anticollision method for reading ID information in radio frequency - Google Patents
Anticollision method for reading ID information in radio frequency Download PDFInfo
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- CN100405775C CN100405775C CNB2006100008808A CN200610000880A CN100405775C CN 100405775 C CN100405775 C CN 100405775C CN B2006100008808 A CNB2006100008808 A CN B2006100008808A CN 200610000880 A CN200610000880 A CN 200610000880A CN 100405775 C CN100405775 C CN 100405775C
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Abstract
A collision-proof fetching method of radio frequency identification information includes leading in time-slot selection information used for detecting information collision first to carry out pre-estimation on collision state of time slot selected by countermark then using step-variable long skip communication means to skip over time slot being not able to make communication and only commanding countermark selecting with correct and collision free time slot to return back information for realizing purpose of avoiding collision.
Description
Technical field
The present invention relates to the signal collision bypassing method of the communications field, relate in particular to the anticollision method for reading ID of information in radio-frequency (RF) identification (RFID) system.
Background technology
Radio-frequency (RF) identification (RFID) technology is an emerging in recent years very popular automatic identification technology.REID adopts the mode of radio frequency to carry out contactless two-way communication, thereby realizes the identification to object.Compare with the bar code system that extensively adopts at present, RFID adopts radiofrequency signal to make the user to obtain label information automatically at certain distance, can be conveniently used in occasions such as gate control system, library management, logistics management and quartermaster supply, significantly reduce cost, being with a wide range of applications, is one of research field of the potentialization of present wireless communication field.
Radio-frequency recognition system generally is made up of reader and label two parts.Reader is by the information of radio communication reading tag.In the time of reader work, often have in the radio frequency operation scope that a plurality of labels are positioned at reader.If a plurality of labels send signal to reader simultaneously, so a plurality of signals will produce collision at the reader receiving terminal, make demodulation, the information that reads fail.This just requires reader need adopt collision-avoidance mechanism to read the information of a plurality of labels in work.
Field of radio frequency identification is very general to the research of collision-proof method in the world at present, is typically EPC global the most and is organized in the Q parametric technique that provides in its second generation standard (EPC-Generation2) suggestion.This method is based on the random algorithm strategy of time division multiplexing (TDMA), to be divided into a plurality of reading time slots the time selects for label, transmission and adjustment by the parameter Q of number of time slot is read in representative dynamically change the number of the reading time slot of choosing for label, thereby reach the purpose that reduces collision.Specifically will be divided into 2 Q power exactly the time and read time slot, one of label picked at random is read time slot to the reader inverse signal, reader is adjusted parameter Q according to each situation that reads of reading time slot, just increase parameter Q if bump at this reading time slot, if this time slot free time just reduces Q, the dynamically adjustment that continues by to the Q value reaches the purpose that reduces collision.But the algorithm that the EPC standard recommendation provides, after each reads the time slot end, reader all needs to adjust parameter Q, therefore the number of times that needs iteration to adjust is a lot, its main cause is because the special nature of rfid system, when selecting to read time slot, label can't know the information of the reading time slot that other label is selected, causing some to read time slot does not have label transmission information and wastes resource, and some reading time slot has a plurality of labels to transmit simultaneously, causes reader because signal collision can't obtain correct information.When reading a fairly large number of label, just need the long time.
Summary of the invention
At the problems referred to above, the object of the present invention is to provide a kind of anticollision method for reading ID of new information in radio frequency.The basic design of this method is: the process of reader reading tag information is divided into time slot reservation and information reads two stages, at first by introducing a kind of time slot selection information that is used for detecting information collision, collision situation to the selected time slot of label carries out pre-estimation, adopt variable step leapfrog method for communicating to skip the time slot that to communicate by letter then, only the label return information of correct collisionless time slot is chosen in order, avoids the purpose of colliding thereby reach.This method can be avoided effectively because idle time slot and the collision time loss that time slot brought improve the efficient that reads greatly.
According to purpose of the present invention, the anticollision method for reading ID of information in radio frequency comprises time slot reservation and information fetch phase.The time slot reservation stage comprises step:
1. reader sends the estimation time slot sequence number that order notifies each label to choose oneself, chooses number range E and together sends in company with subscription command;
2. the information of each label demodulation reader obtains the numerical value E of the scope of choosing, and numerical value Ai of picked at random and writes down this value as the own time slot sequence number of returning on the time slot counter of this locality in this scope;
3. each label returns to reader with selected Ai value information, and the method for returning can be in the selected time oneself time slot selection information to be sent to reader; Wherein, described time slot selects information that multiple mode can be arranged, and for example can be the short short signal frame of a kind of relative RFID sign indicating number, also can adopt any signal frame form that can collision detection;
4. the selection gap information that returns of reader tags detected, obtain the collision information of each time slot after the demodulation: if there is not signal, then explanation does not have label to select this time slot, and we claim this type of time slot to be " empty slot "; If can detect correct information, explanation has only a label to select this time slot so, and we claim this type of time slot to be " correct time slot "; If detect collision, at least two labels of explanation are selected this same time slot so, and we claim this type of time slot to be " collision time slot ".；
5. reader generates a time slot option table that contains collision information according to collision information, and whether repeats time slot reservation or enter the information read step according to the condition judgment of setting.
Wherein, described time slot option table can have multiple expression mode, for example can be the table that contains collision information, also can be a sequence that comprises collision information, as long as can reflect the collision subscription information.The condition of described setting can roughly be divided into two kinds of situations: 1) number of tags that reads at needs is more, estimate under the bigger situation of number of time slot E, then may before entering the information fetch phase, repeatedly preengage, make the collision time slot number less to one than entering the information fetch phase after the reasonable range again, for example: if the collision time slot is more, then increase time slot and choose scope E, preengage time slot again; (need to prove, if empty slot is more, do not preengage time slot again, but directly enter the information fetch phase.) after the time slot adjustment is suitable, the stage that the information of entering reads.2) number of tags that reads at needs is less, estimate under the less situation of number of time slot E, can only take turns reservation and promptly enter the information fetch phase through one, treat that first round information reads after the end, readjust the E value of estimating time slot according to the number of collision time slot in the first round again, repeat time slot reservation and information read step.Preferably, the condition of described setting can be will the collision time slot number account for ratio and a preset threshold of estimating number of time slot E and compare, preengage time slot again if ratio just increases number of time slot E greater than preset threshold; Otherwise just enter fetch phase.Also actual number and threshold value of collision time slot can be compared, thereby judge again the time slot reservation stage or enter fetch phase.After the estimation number of time slot E that judges the time slot reservation stage need adjust, the method for adjustment E can have multiple, for example the number of E directly can be increased the multiple of a setting, for example can be twice; Also can make full use of the result of time slot reservation last time, the number that increases the collision time slot on the basis of original E is as new E value.
At the information fetch phase, reader adopts the mode of leapfrog to choose the collisionless time slot that can correctly communicate by letter according to the time slot option table and communicates, skip the idle time slot and the time slot of collision.
The information fetch phase comprises step:
1. reader draws the parameter that concerns between the correct time slot of reflection according to the time slot option table, and it is additional for reading a leapfrog parameter of order, sends to each label; Wherein, the leapfrog selection of parameter can have various ways, as long as can indicate the number of time slot of skipping.For example, can transmit between two correct time slots difference, also can transmit the difference of all correct time slots and first time slot as skipping step value.
2. after label is received and read order, demodulate the leapfrog parameter S, and upgrade each self-recording selected time slot sequence number in view of the above;
To show own selected be correct time slot if 3. upgrade the result, and then this label is to the reader return information, otherwise waits for the next order of reading.
After so each reading order sends, have and only have a label return information that is selected from correct time slot, therefore reader can read the information that all have chosen the label of correct time slot successively.
After epicycle reads process and finishes,, proceed the time slot reservation operation of a new round so, carry out leapfrog then and read process and read the remaining label of not reading if still there is the label that is not read.Time slot reservation parameter E can calculate according to last round of time slot reservation result optimizing and provide.Otherwise,, illustrate that so the whole process that reads finishes if reader does not detect " collision time slot " in the time slot reservation stage.
Technique effect of the present invention is: 1) introduced the short signal frame and carried out time slot reservation, can avoid dynamically adjusting in the prior art and read the load that number of time slot Q value is brought, reduced the adjustment load by introducing the short signal frame; 2) adopt the leapfrog method of variable step to choose the time slot that is fit to communication, only the time slot that can correctly read is read, avoided the empty slot and the collision wasting of resources that time slot caused in original method, improved efficient greatly; Reduced the consumption of energy when 3) the time reading efficiency increases; 4) the short signal frame of Yin Ruing can be estimated number of tags under unclassified situation; 5) with respect to the easier realization of original method.
Description of drawings
Fig. 1 represents the flow chart of the embodiment of the invention.
Embodiment
Below by preferred embodiment in conjunction with the accompanying drawings, describe the present invention, but be not construed as limiting the invention.
A kind of new radio frequency identification anti-collision read method is divided into time slot reservation and information and reads two steps, its flow process as shown in Figure 1, in the time slot reservation stage:
The first step, reader are at first determined an initialization estimation time slot window E, and all labels in readable distance send collision pre-estimation order-Estimate order, estimate that number of time slot E sends in company with ordering together.After label in the reader read range receives this order,, and when arriving, this time slot responded to reader transmission short signal frame all with at random a mode selected own answer time slot in given time slot scope E.(1≤Ai≤E) is kept in separately the time slot counter time slot sequence number Ai that each label is chosen.Wherein, the short signal frame is 4 bit random sequences, its effect only is used for the situation of collision detection, therefore, those skilled in the art will be understood that the short signal frame in the present embodiment can also be other length, such as being greater than or less than 4 bits, because its length is not monotechnics feature of the present invention, therefore can not be construed as limiting the present invention.
In second step, after reader is received the short signal frame that label returns, suitably adjust estimating time slot E according to the time slot reservation situation.Concrete grammar is, the reader statistics is returned time slot, does not receive that wherein " empty slot " number of short signal frame is N0, only receives that " correct time slot " number of a short signal frame is N1, " collision time slot " number of receiving two above short signal frames is N2, i.e. N0+N1+N2=E.If the number of collision time slot is more, then suitably increase E, if the number of empty slot is more, then suitably reduce E.In the present embodiment, the Rule of judgment of setting is: if N2/E＞0.2, just increase the number E that estimates time slot, for example E is doubled (to need to prove here, if the number of empty slot is more, then do not need to carry out again time slot reservation, but can directly enter fetch phase, reason is skipped empty slot can not cause epicycle skip label).Adjust after the number of time slot E, reader sends collision pre-estimation order Estimate to label once more, repeats reservation, when number of time slot is suitable, when promptly above-mentioned two Rule of judgment are all ungratified, enters next stage reading tag information.Wherein, judge number of time slot whether can set as the case may be by appropriate condition, those skilled in the art will be understood that two Rule of judgment that present embodiment is lifted can also change becomes other forms, it is not a single feature of the present invention, can not be construed as limiting the invention.
At the information fetch phase, reader adopts the method for leapfrog directly to read the label of correct time slot.Detailed process is as follows: the situation of returning of each label short signal frame when reader is at first finished according to the reservation stage, determine a collision pre-estimation table.This table shows the label selection situation of each time slot that will read: blank, correct or collision.Then reader calculated goes out the time slot sequence number difference S between a current correct time slot and the last correct time slot, and it is additional for reading the step parameter of order Read, sends to each label.After label is received the Read order, demodulate S, and time slot counter Ai that will be separately deducts the S value, and then the time slot counter of having chosen the label of current correct time slot in the time slot reservation stage has just become 0, so this label begins to return to reader the label information of oneself immediately.Because this time slot is only chosen by a label, so other labels can be simultaneously to the reader return information, thereby has avoided information collision.Simultaneously, blank time slot of other between two correct time slots and collision time slot are all skipped, and have improved the utilance of time slot greatly.Reader selects correct time slot successively according to the method for this leapfrog and communicates, promptly, continue to calculate the sequence number difference S between two correct time slots, and the each reading order Read of companion sends to each label, make that like this label that is in correct time slot can be read successively according to this order, select the label of " collision time slot " then to be skipped.
After the first round, information read end, reader judges whether to exist according to collision pre-estimation table did not again read label, and then whether decision is carried out the time slot reservation of a new round and read process.Also have " collision time slot " if collision pre-estimation table shows, so just obtain the numerical value of new round time slot reservation stage parameter E ' according to the number computation optimization of " collision time slot ", in the present embodiment, E ' value is 3 times of the collision time slot.Reader resends collision pre-estimation order-Estimate then, and the time slot reservation and the information of a beginning new round read process.
At last, have only blank time slot and correct time slot in collision pre-estimation table, when not having the collision time slot, all correctly read with regard to care label so, the whole process that reads just is through with.
More than describe the present invention in detail by specific embodiment, those skilled in the art is to be understood that, time slot reservation that the present invention is included and information read two steps and can repeat, time slot reservation that each is taken turns and information read step can be intersected and carried out, also can repeat time slot reservation when adjusting to more suitable time slot scope, the information of carrying out reads again.Therefore,, can make various modifications and distortion, all can realize the present invention embodiment based on design of the present invention.
Claims (7)
1. the anticollision method for reading ID of an information in radio frequency comprises step:
(1) time slot reservation comprises step:
A. reader is to label sending time slots subscription command and estimation number of time slot;
B. each label is all with at random mode selected reservation time slot separately in given time slot scope, and returns time slot and select information, simultaneously the record sequence number of selected time slot separately;
C. reader generates the time slot option table according to the time slot selection information of returning, and whether repeats time slot reservation or enter the information read step according to the condition judgment of setting;
(2) information reads, and reader is taked the method for leapfrog according to the time slot option table, skips empty slot and collision time slot in the time slot option table, reads the label information of correct time slot;
(3) judge whether there is the collision time slot in the time slot option table, then adjust number and repeating step (1) and (2) of estimating time slot, then finish if do not collide time slot if collide time slot in addition.
2. the method for claim 1 is characterized in that, the method for described leapfrog comprises step:
A. reader draws the parameter that concerns between the correct time slot of reflection according to the time slot option table, and it is additional for reading a leapfrog parameter of order, sends to each label;
B. after label is received and read order, demodulate the leapfrog parameter, and upgrade each self-recording selected time slot sequence number in view of the above;
To show own selected be correct time slot if c. upgrade the result, and then this label is to the reader return information, otherwise waits for the next order of reading.
3. the method for claim 1 is characterized in that, described time slot selection information is the short signal frame.
4. the method for claim 1 is characterized in that, described time slot option table is form or the sequence that comprises the time slot selection situation of each label.
5. the method for claim 1, it is characterized in that, the condition of the setting described in the time slot reservation step be will the collision time slot number account for ratio and a preset threshold of estimating number of time slot and compare, or the number that will collide time slot directly compares with a preset threshold.
6. the method for claim 1 is characterized in that, described adjustment estimates that the concrete grammar of number of time slot is: it is directly increased the multiple of a setting, or increase the number of collision time slot on the basis of former numerical value.
7. method as claimed in claim 2 is characterized in that, described leapfrog parameter be between adjacent two the correct time slots of representative difference skip step value, or represent all correct time slots and first time slot difference skip the step-length table.
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| CNB2006100008808A CN100405775C (en) | 2006-01-16 | 2006-01-16 | Anticollision method for reading ID information in radio frequency |
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| CN101436245B (en) * | 2007-11-16 | 2012-05-23 | 中兴通讯股份有限公司 | Label anti-collision method in radio frequency recognition system |
| CN101169818B (en) * | 2007-11-22 | 2011-07-20 | 复旦大学 | Radio frequency identification process frame length selection method based on slotted random |
| CN101661550B (en) * | 2008-08-29 | 2012-05-30 | 佛山市顺德区汉达精密电子科技有限公司 | Method for timing by random code to avoid packet collision in radio frequency identification system, and radio frequency identification system |
| CN102087697B (en) * | 2011-02-25 | 2013-08-14 | 深圳市中兴长天信息技术有限公司 | Data transmission method of reader and wireless tags |
| CN102799842B (en) * | 2011-05-25 | 2016-08-24 | 中兴通讯股份有限公司 | Label counting method and system |
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| CN103336937B (en) * | 2013-06-21 | 2016-08-10 | 无锡赛睿科技有限公司 | A kind of radio-frequency (RF) tag number estimation method based on geometric distribution |
| CN103902942B (en) * | 2014-01-23 | 2016-11-02 | 电子科技大学 | A kind of mixing collision-proof method for Large Copacity multi-tag rfid system |
| CN105095807B (en) * | 2014-05-22 | 2018-02-23 | 北京邮电大学 | Radio frequency identification sensor network collision avoidance system and algorithm based on intercard communication mechanism |
| CN106919879B (en) * | 2015-12-28 | 2020-03-13 | 航天信息股份有限公司 | Double-frequency label anti-collision equipment and method |
| CN106599751B (en) * | 2016-12-23 | 2019-11-29 | 西京学院 | A kind of RFID tag collision-proof method based on flat-sawn iteration |
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