CN102609672A - Anti-collision method of radio frequency identification (RFID) system - Google Patents
Anti-collision method of radio frequency identification (RFID) system Download PDFInfo
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Abstract
The invention relates to an anti-collision method of a radio frequency identification (RFID) system, being an anti-collision scheme of the RFID system and mainly solving the collision problem when a tag in the RFID system is read. The anti-collision method comprises the following three steps of: 1) firstly identifying digits of collision and primarily estimating number of labels; 2) then selectively reading the labels which meet conditions within time in a given frame size; and 3) and then updating frame size parameters according to secondary collision information, so as to realize secondary label reading, wherein a passive label collision problem of an ultrahigh frequency RFID system based on an EPCUHFClass1Gen2 protocol is mainly solved. By adopting the anti-collision method disclosed by the invention, reliability of the system can be guaranteed, anti-collision period can be shortened, and utilization rate of a channel and throughput rate of the system can be improved.
Description
Technical field
The present invention relates to the Internet of Things field, particularly, is a kind of anticollision scheme of radio-frequency recognition system, mainly solves the collision problem when label reads in the radio-frequency recognition system.
Background technology
(Radio Frequency Identification is a kind of space coupling that utilizes radiofrequency signal or the transport property of reflection RFID) to RF identification, realizes the automatic identification technology to wireless, contactless, the two-way communication that is identified object.At present, the standard of radio frequency identification comprises EPCglobal standard, Japanese UID standard, ISO international standard etc.
In the rfid system application process, through regular meeting a plurality of readers or label appear in same rf coverage area territory, share same wireless channel, the phase mutual interference between this reader or the label will inevitably produce conflict, is referred to as collision (Collision).Wherein, label collision is meant and in the readable range of a reader, has a plurality of labels simultaneously, and then the answer signal that returns of label is because the phase mutual interference forms data collision, thereby causes the communication failure between reader and the label.
Multiplexed in the wireless communication system generally has: space division multiple access (SDMA) method, frequency division multiple access (FDMA) method, CDMA (CDMA) method and time division multiple access (TDMA) (TDMA) method.Wherein, time division multiple access (TDMA) (TDMA) method is that a physical channel is divided into several timeslices by the time, and alternately is distributed to a plurality of signals and used.This method realizes simple, is widely used in the rfid system, and can avoids the label collision problem well.TDMA anticollision protocol at present commonly used comprise based on the stochastic pattern agreement of ALOHA and based on binary tree the search agreement of finalizing the design really.
Summary of the invention
Technical matters:The collision-proof method that the purpose of this invention is to provide a kind of radio-frequency recognition system mainly solves the agreement based on EPC UHF Class1 Gen2, the passive label collision problem of hyper band rfid system.The present invention can guarantee the reliability of system, shortens the cycle of anticollision, improves the utilization factor of channel and the throughput of system.
Technical scheme:The collision-proof method of radio-frequency recognition system of the present invention comprises three steps:
1) elder generation passes through identification collision bit, number of tags according to a preliminary estimate: reader sends order, lets all interior labels of its working range respond, and through work characteristics and the Manchester's cde characteristic of utilizing RF tag, realizes the judgement of reader to code violation; If there is not a data collision, correct identification label then, and label is carried out related application operate; If there is collision, then write down collision bit N and the highest collision position D;
2) selectively the label that satisfies condition is read in the time at given frame length then: through the collision bit N that step 1 obtains, the frame length time slot does according to a preliminary estimate
, reader sends order, and making the highest collision position D is that zero label selects at random that (0, any time slot between L-1) sends answer signal; If there is not data collision, then correctly identification label is also carried out relevant application operating; If there is collision, then record collides time slot rate P
c
3), upgrade the frame length parameter, to realize the secondary reading tag: according to step 2 again according to secondary collision information) frame slot length L and collision time slot rate P
c, utilize formula
, estimate number of tags n, upgrade next frame frame slot length
, reader sends order, make the highest collision position D be zero label select at random (0, L
'-1) any time slot between sends answer signal; If there is not a data collision, correct the go forward side by side application operating of line correlation of identification label then; If there is collision, then still exist label to discern, continue execution in step 1), 2), 3), realize the real-time monitoring and control of reader to label.
Beneficial effect:Use this scheme that following advantage is arranged:
1. reduce the collision rate of system:Step 1 pair collision information is analyzed, if the collision of N position is arranged, then the collision labels number is (2 ~ 2
N) between value, frame slot length according to a preliminary estimate
, make L be unlikely to obtain excessive and the waste frame slot, also be unlikely to obtain too small and the increase collision rate, reduced deviation from randomness, the information of leakage is also less.
. improve the reliability of system:Conditional request is set in the step 2: the highest collision position is that zero label just can send answer signal, has reduced the label collision probability, has improved channel utilization.And to be 1 label have two kinds of situation in the highest collision position: (1) sequence number is 1 entirely, and after every other label had read, in next one circulation, step 1 read this unique tags, does not produce collision, reader continuation execution in step 1 real-time listening; (2) figure place must be arranged less than the highest collision position in the sequence number, and the value of this position is zero, then waits to be recycledly, during for the highest collision, read this label until this zero-bit.The reliability of system is able to guarantee.
. the performance of optimization system:Step 3 has been utilized the collision rate that obtains in the step 2, supposes the binomial distribution of label obedience, estimates number of tags n, the frame slot length L that obtains upgrading according to system effectiveness again
', dynamically adjust the anticollision cycle, optimization of system performance.
Description of drawings
Fig. 1 is the anticollision scheme working mechanism of radio-frequency recognition system, and being divided into is three steps.
Fig. 2 is the anticollision scheme process flow diagram of radio-frequency recognition system, realizes the real-time listening function of reader.
Embodiment
When a plurality of RFID labels send answer signal response reader simultaneously; When if same data bit has different value; The signal rising edge and the negative edge that receive are cancelled each other; Causing the signal in whole bit length all is continual subcarrier signal, thereby causes reader can't judge this coding, can not identification label.In the existing protocol, lower based on the stochastic pattern protocol channels utilization factor of ALOHA, the anticollision cycle is longer; Search is finalized the design really based on binary tree, and the agreement time delay is long, reveal information is more.Method of the present invention is through estimating number of tags, dynamically updating frame slot length, in order to address the aforementioned drawbacks problem.
One, architecture
It is three steps that this scheme is divided into: 1) earlier through identification collision bit, number of tags according to a preliminary estimate; 2) selectively the label that satisfies condition is read in the time at given frame length then; 3), upgrade the frame length parameter, to realize the secondary reading tag again according to secondary collision information.Fig. 1 has provided the working mechanism of this scheme.
Step 1, through work characteristics and the Manchester's cde characteristic of utilizing RF tag, reader is realized the judgement to code violation.If there is not a data collision, correct identification label then, and label is carried out related application operate.If there is collision, then writes down collision bit and the highest collision position, and carry out twice frame slot Card Reader operation.
Step 2, the collision bit that gets through step 1, frame slot length L according to a preliminary estimate reads the highest collision position and is zero label.
Step 3 according to the collision time slot rate of frame slot in the step 2, is utilized correlation formula, upgrades the frame slot length L
', still making the highest collision of reader identification position is zero label, carries out secondary and reads.
After step 3 was accomplished, execution in step 1 once more, with the real-time monitoring and control of realization reader, and to the required application operating of label execution.
The operating characteristic that this scheme relates to has:
The work characteristics of RF tag:Reader sends the REQUEST order; If when label self sequence number is not more than the sequence number of reader transmission, then system is made response, and through pseudorandom number generator (RNG); Produce the pseudo random number RN16 of 16bit, as the answer signal first that sends to reader.Behind the correct identification label of reader, will send ACK and confirm order to this label, label returns the value of PC, EPC and CRC-16 again and gives reader.Behind the correct identification label of reader, can carry out the related application operation to it, for example: SELECT reads write operation, and READ-DATE reads the storage data, UNSELECT dormancy label.
The Manchester's cde characteristic:When a plurality of RFID labels adopt Manchester's cde to send answer signal simultaneously; If identical data has different numerical on the position; The signal rising edge and the negative edge that then receive are cancelled each other; Causing in whole bit length all is continual subcarrier signal, thereby makes reader translate wrong code word, and step-by-step identifies collision.
Frame slot:Be divided into a plurality of discrete time slots (slot) to the time, and each slot length is greater than the time span that label is replied data, forms a frame to L time slot again, label is selected time slot transmission data at random in each frame.
Time slot A LOHA:If frame slot length is L, number of tags is n, and then multiple Bernoulli Jacob's distribution is obeyed in label distribution of time slot in frame.Because time slot probability impartial
then has the probability of k label to be in a time slot:
in the frame.
Suppose that each time slots equates that at interval do not consider environmental factor, it is n that free number of time slot is then arranged in the frame slot
0, empty slot rate P
0, successful number of time slot is n
s, successful time slot rate P
s, the collision number of time slot is n
c, collision time slot rate P
c:
By formula
;:
,
.
System effectiveness η:The ratio of success time slot and total time slot, the theoretical system efficient of frame slot ALOHA algorithm
η is asked the derivative
about L; Can release when frame length is L, most effective label number of responses is:
.When number of tags is n; The frame length optimum value is:
; When n is very big, with the following formula Taylor expansion:
.Therefore; When number of tags is identical with the frame slot number; I.e.
, the reading efficiency of reader is the highest.
Two, method flow
The key issue of rfid system time slot anticollision technology is: how to confirm number of tags and time slot frame length.Fig. 2 has provided the groundwork flow process of this scheme:
1. reader sends a maximum sequence number, lets all interior labels of its working range respond.
2. the answer signal decoding of reader to receiving, if there is data bit to discern, then judging has collision, changes 3.If there is not a data collision, correct identification label then, and label carried out application operating, and make its entering " noiseless " state after the completion, change 1 again.
3. define collision, then write down the highest collision position and collision bit, difference assignment D and N are as next step operating parameter.
4. according to collision bit; Frame slot length
according to a preliminary estimate; Reader sends order lets the D position be zero label response; The label that satisfies condition selects at random that (0, any time slot between L-1) sends answer signal.If there is data bit to discern, then judging has collision.If there is not a data collision, correct identification label then, and label carried out application operating, make its entering " noiseless " state after the completion.
5. according to frame slot length L in 4 and collision time slot rate P
c, reader utilizes formula
Estimate number of tags n, and according to formula
, assignment next frame frame slot length
According to formula
, can derive
.
6. reader sends order and lets the highest collision position D be zero label response, the label that satisfies condition select at random (0, L
'-1) any time slot between sends answer signal, carries out new one and takes turns the operation of frame slot Card Reader.If there is data bit to discern, then judging has collision.If there is not a data collision, correct identification label then, and label carried out application operating, make its entering " noiseless " state after the completion.
7. carry out 1 once more, realize the real-time monitoring and control of reader.
Describe for ease, we have following application example at supposition:
Supposing has 3 labels, label a=11111111, label b=10101010, label c=10111110 in the reader working field.
1. original state is opened reader, and utilizes order REQUEST (11111111) to send a maximum sequence number; All label a in its working range then; The sequence number that b, c self sequence number all send less than reader is all replied reader with self sequence number as answer signal.
2. reader is deciphered the answer signal that receives, and produces data collision, writes down the highest collision position D=6, collision bit N=3.
3. according to collision bit, frame slot length according to a preliminary estimate
, L=2 then
3=8, reader sends order REQUEST (6,0), promptly lets the 6th to be zero label response, and this moment, label b and c satisfied condition.Reader sends Query (3) once more, lets label b and c (0 ~ 2
3-1) select any time slot to send answer signal between at random.
4. if data collision is arranged, then label can't correctly be discerned.If no datat collision, the correct identification label of reader then, and do relevant read operation, the order UNSELECT that redispatches is changed to label " noiseless " state.Collision time slot rate according to this frame; Reader utilizes formula
to estimate number of tags n, and makes next frame frame length
.According to formula
, can derive
.
5. reader sends order QueryAdjust (N
'), let the highest collision position D be zero label response, the label that satisfies condition select at random (0, L
'-1) any time slot between sends answer signal, carries out new one and takes turns the operation of frame slot Card Reader.If there is data bit to discern, then judge to have collision.If there is not a data collision, correct identification label then, and label carried out application operating, accomplish the back transmission and order UNSELECT to make its entering " noiseless " state.
6. after twice frame slot Card Reader operation, reader resends order REQUEST (11111111), and the operation steps before carrying out once more all is read until label b and c.
7. reader sends order REQUEST (11111111) once more, has only unique tags a response this moment, and then correct reading tag, and label carried out application operating is accomplished the back and sent and order UNSELECT to make its entering " noiseless " state.Reading tag operation this time, collisionless produces, and then need not carry out twice frame slot Card Reader operation again.
8. reader sends order REQUEST (11111111) once more, seeks to have or not label that does not read or the label of newly putting in its working field, realizes the real-time listening function.
Claims (1)
1. the collision-proof method of a radio-frequency recognition system is characterized in that this method comprises three steps:
1) elder generation passes through identification collision bit, number of tags according to a preliminary estimate: reader sends order, lets all interior labels of its working range respond, and through work characteristics and the Manchester's cde characteristic of utilizing RF tag, realizes the judgement of reader to code violation; If there is not a data collision, correct identification label then, and label is carried out related application operate; If there is collision, then write down collision bit N and the highest collision position D;
2) selectively the label that satisfies condition is read in the time at given frame length then: through the collision bit N that step 1 obtains, the frame length time slot does according to a preliminary estimate
, reader sends order, and making the highest collision position D is that zero label selects at random that (0, any time slot between L-1) sends answer signal; If there is not data collision, then correctly identification label is also carried out relevant application operating; If there is collision, then record collides time slot rate P
c
3), upgrade the frame length parameter, to realize the secondary reading tag: according to step 2 again according to secondary collision information) frame slot length L and collision time slot rate P
c, utilize formula
, estimate number of tags n, upgrade next frame frame slot length
, reader sends order, make the highest collision position D be zero label select at random (0, L
'-1) any time slot between sends answer signal; If there is not a data collision, correct the go forward side by side application operating of line correlation of identification label then; If there is collision, then still exist label to discern, continue execution in step 1), 2), 3), realize the real-time monitoring and control of reader to label.
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| CN103324902A (en) * | 2013-06-25 | 2013-09-25 | 浙江银江研究院有限公司 | Accurate tag estimating method of RFID system |
| CN103679099A (en) * | 2013-12-13 | 2014-03-26 | 浙江银江研究院有限公司 | Anti-collision method applied to mass-RFID-label system |
| CN103955657A (en) * | 2014-05-22 | 2014-07-30 | 江西理工大学 | Anti-collision algorithm for frame time slot ultrahigh frequency RFID system based on blind separation |
| CN104573593A (en) * | 2015-01-20 | 2015-04-29 | 江西理工大学 | Underdetermined blind source separation RFID anti-collision method based on frame slots |
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| CN106446741A (en) * | 2016-09-27 | 2017-02-22 | 西京学院 | Radio frequency identification secondary slot time pre-distribution tag anti-collision method |
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| CN103324902B (en) * | 2013-06-25 | 2015-12-02 | 浙江银江研究院有限公司 | Accurate label method of estimation in a kind of rfid system |
| CN103324902A (en) * | 2013-06-25 | 2013-09-25 | 浙江银江研究院有限公司 | Accurate tag estimating method of RFID system |
| CN103679099A (en) * | 2013-12-13 | 2014-03-26 | 浙江银江研究院有限公司 | Anti-collision method applied to mass-RFID-label system |
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| CN103955657B (en) * | 2014-05-22 | 2017-06-06 | 江西理工大学 | A kind of frame slot ultrahigh frequency RFID system anti-collision method based on blind separation |
| CN103955657A (en) * | 2014-05-22 | 2014-07-30 | 江西理工大学 | Anti-collision algorithm for frame time slot ultrahigh frequency RFID system based on blind separation |
| CN104573593A (en) * | 2015-01-20 | 2015-04-29 | 江西理工大学 | Underdetermined blind source separation RFID anti-collision method based on frame slots |
| CN104573593B (en) * | 2015-01-20 | 2017-05-31 | 江西理工大学 | A kind of deficient based on frame slot determines blind separation RFID anti-collision method |
| CN106096476A (en) * | 2016-06-06 | 2016-11-09 | 西北工业大学 | Based on multi channel reader collision avoidance method in a kind of rfid system |
| CN106446741A (en) * | 2016-09-27 | 2017-02-22 | 西京学院 | Radio frequency identification secondary slot time pre-distribution tag anti-collision method |
| CN106446741B (en) * | 2016-09-27 | 2019-06-04 | 西京学院 | A kind of secondary pre-allocation slot label anti-collision method of radio frequency identification |
| CN108537081A (en) * | 2018-04-04 | 2018-09-14 | 顺丰科技有限公司 | A kind of read method and logistic label system of batch logistic label |
| CN108537081B (en) * | 2018-04-04 | 2021-09-28 | 顺丰科技有限公司 | Reading method of batch logistics labels and logistics label system |
| CN109104420A (en) * | 2018-07-30 | 2018-12-28 | 太原理工大学 | A kind of data rapid transmission method based on EPC communication protocol |
| CN109104420B (en) * | 2018-07-30 | 2021-01-08 | 太原理工大学 | Data rapid transmission method based on EPC communication protocol |
| CN109511105A (en) * | 2018-12-21 | 2019-03-22 | 大连大学 | Random number homogenising treatment method and radio frequency know the methods and applications for reducing collision number of timeslots |
| CN114448470A (en) * | 2020-11-02 | 2022-05-06 | 凌通科技股份有限公司 | Radio frequency identification communication method and radio frequency identification communication system using same |
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Application publication date: 20120725 |