CN109543477A - Adaptive multiway tree anti-collision algorithm based on mapping code - Google Patents
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Abstract
The invention discloses the adaptive multiway tree anti-collision algorithms based on mapping code, the characteristic of collision bit can be accurately identified according to Manchester's code, by the value for calculating impact factor μ, estimate the number of labels of collision, dynamic selection fork tree, the advantages of having given full play to respective fork tree, reduces collision time slot, improves the performance of system.On the basis of 8-4-2 dynamic multi-branches tree algorithm, mapping code is introduced, inquiry prefix is determined according to unique mapping relations, successfully eliminates free timeslot present in dynamic multi-branches tree algorithm, recognition time greatly reduces, and the recognition efficiency of system increases.
Description
Technical field
The present invention relates to technical field of RFID, and in particular to the adaptive multiway tree anticollision based on mapping code is calculated
Method.
Background technique
With the fast development of technology of Internet of things, the epoch of all things on earth interconnection are at hand.As the big crucial skill of Internet of Things four
One of art, radio RF recognition technology (Radio Frequency Identification, RFID) become scholars and study
Hot spot.Radio frequency identification (RFID) technology is developed in the 1980s, has nearly 40 years history so far, is that one kind passes through
The new technology of the contactless automatic identification target object of radio signal, widely applies to supply chain management, storage controlling
With to fields such as image tracings.
RFID system is mainly made of reader, electronic tag and central information processing system three parts, with space electricity
Magnetic wave is medium, realizes two-way communication and Information Number between label and reader using the backscattering coupling of spatial electromagnetic wave
According to automatic identification.When multiple labels respond reader simultaneously, i.e., so-called tag-collision can seriously affect RFID system
Recognition efficiency and performance, even result in recognition failures.Therefore, label anti-collision algorithm is an important research direction.
RFID label tag anti-collision algorithm is based primarily upon four kinds of modes, is space division multiple access (space division respectively
Multiple access, SDMA), frequency division multiple access (frequency division multiple access, FDMA), code point
Multiple access (code division multiple access, CDMA) and time division multiple acess (time division multiple
Access, TDMA).Implement that difficulty is relatively high in view of other methods, now most widely used is the method for time division multiple acess.
The anti-collision algorithm of time division multiple acess is mainly divided into two classes again, the nondeterministic algorithm based on ALOHA and the determination algorithm based on tree.
Probabilistic synchronization algorithm based on ALOHA has the advantages that equipment is simple, communication overhead is low, recognition speed is fast, mainly has
Pure ALOHA algorithm, CDMA slotted ALOHA algorithm, Frame Slotted Aloha algorithm, dynamic Frame Slotted Aloha algorithm and based on ALOHA's
Various innovatory algorithms.But all there is " label is hungry to death " in these algorithms, i.e., since recognition time is longer and uncertain
The drawbacks of factor, and cause the phenomenon that a large amount of labels flock together or part labels are idle always, this is probabilistic synchronization algorithm.Based on tree
Deterministic algorithm mainly include that binary tree algorithm (BT) and inquiry tree algorithm (QT) and other improvements type based on tree are calculated
Method avoids " label is hungry to death " problem by gradually separation tags, and recognition efficiency can reach 100%.But tree algorithm is deposited
It is long in recognition cycle, the problems such as system throughput is low.
Adaptive multi-fork tree algorithm is can to accurately identify collision bit using Manchester's code on the basis of multiway tree
Characteristic, by calculating impact factor, dynamic selection fork tree, i.e., selection fork sets more calculation when number of labels is more
Method, on the contrary selection fork sets less algorithm.In paper " the RFID system 8-4-2 dynamic multiway tree anti-collision algorithm of Guo Rongzuo etc.
Design and analysis " in propose a kind of 8-4-2 dynamic multiway tree anti-collision algorithm, dynamically select binary tree, quaternary tree and eight
Fork tree, reduces collision frequency, improves the whole efficiency of system, but due to producing a large amount of when fork tree is increased
Free timeslot, seriously affected the performance of system.
Summary of the invention
The present invention proposes a kind of adaptive multiway tree anti-collision algorithm based on mapping code according to above-mentioned deficiency
(Adaptive multi-tree search algorithm based on mapping code, AMSMC), it is adaptive in dynamic
On the basis of answering multiway tree, mapping relations one by one are introduced, eliminate the free timeslot of adaptive multi-fork tree algorithm, improves and is
The performance of system.
Technical solution:
Based on the adaptive multiway tree anti-collision algorithm of mapping code, comprising steps of
Step (1): reader initial interrogation storehouse Q sends search command Request-all, so that in sphere of action
All label responses；
Step (2): reader judges time slot state by the responsive status of all labels in its sphere of action；When only
It when one label response, identifies successfully, and keeps label silent, go to step (5)；When there are two the above labels to ring simultaneously
When answering, tag-collision occurs, go to step (3)；
Step (3): the specific bit to collide and non-collision position are determined according to Manchester's code principle, will be collided
Information before position is pressed into storehouse Q as inquiry prefix；According to the number of tags of response simultaneously, impact factor μ is calculated, determination is searched
The value of rope fork tree and re-encoding bit length c；C=2 when quaternary tree, c=3 when Octree；
As μ < 0.75, using binary tree search；It determines new inquiry code, is pressed into query stacking, it is former according to binary certainty
Reason Direct Recognition goes out two labels, and return step (2)；As μ >=0.75, reader is determined according to the content of storehouse Q and is inquired
Prefix pre, sends instruction Query (pre, c), and label responds and carries out mapping code；
As 0.75≤μ < 0.97, quaternary tree search is selected, according to table 1, the information corresponding one of the high two collisions prefix of label
0 completion 2 is added in a 4 bit mapping code, inadequate 2 preamble bits；
1 quaternary tree mapping relations of table
As μ >=0.97, Octree search is selected, according to table 2, the information of the high three collisions prefix of label is one 8 corresponding
0 completion is added to 3 in bit mapping code, inadequate 3 preamble bits；
2 Octree mapping relations of table
Step (4): reader sends Request (pre) order, responds with the label of inquiry prefix matching, if do not had
It collides, then identifies one by one, go to step (5)；If colliding, go to step (3)；
Step (5): whether the content for judging storehouse is sky, if not empty, reads stack head prefix, is sent to label, jumps
To step (2)；If it is empty, all labels are all identified.
When carrying out multiway tree search, average timeslot number is Tm=m (1-1/m)n-1, it is possible thereby to calculate, as n < 3, T2<
T4, and as n >=3, T2> T4, n=3 is the critical value of binary tree and quaternary tree, calculates impact factor at this timeAs n < 6, T4< T8, and as n >=6, T4> T8, n=6 is the critical of quaternary tree and Octree
Value calculates impact factor at this timeIt obtains as the μ < 0.75 detected, using binary tree search, when
When 0.75≤μ < 0.97, quaternary tree search is used instead, as μ >=0.97, use Octree search instead.
The utility model has the advantages that the present invention estimates the number of labels of collision by the value of calculating impact factor μ, dynamic selection fork
Tree has given full play to the advantages of respective fork is set, has reduced collision time slot, improve the performance of system.In 8-4-2 dynamic multiway tree
On the basis of algorithm, mapping code is introduced, inquiry prefix is determined according to unique mapping relations, successfully eliminates dynamic multi-fork
Free timeslot present in tree algorithm, recognition time greatly reduce, and the recognition efficiency of system increases.
Detailed description of the invention
Fig. 1 is flow chart of the invention.
Fig. 2 is for AMSMC algorithm of the invention and without idle QuadTree algorithm, CT algorithm, AMS algorithm, Octree algorithm
Total time slot comparison schematic diagram.
Fig. 3 is for AMSMC algorithm of the invention and without idle QuadTree algorithm, CT algorithm, AMS algorithm, Octree algorithm
Throughput comparison schematic diagram.
Specific embodiment
In the following with reference to the drawings and specific embodiments, the present invention is furture elucidated.
Fig. 1 is flow chart of the invention.As shown in Figure 1, the present invention is based on mapping code adaptive multi-fork tree algorithm include
Step:
Step (1): reader initial interrogation storehouse Q sends search command Request-all, so that in sphere of action
All label responses；
Step (2): reader judges time slot state by the responsive status of all labels in its sphere of action；When only
It when one label response, identifies successfully, and keeps label silent, go to step (5)；When there are two the above labels to ring simultaneously
When answering, tag-collision occurs, go to step (3)；
Step (3): the specific bit to collide and non-collision position are determined according to Manchester's code principle, will be collided
Information before position is pressed into storehouse Q as inquiry prefix；According to the number of tags of response simultaneously, impact factor μ is calculated, determination is searched
The value of rope fork tree and re-encoding bit length c；C=2 when quaternary tree, c=3 when Octree；
Calculate impact factor μ:
Assuming that the ID code length of each label is d bit, wherein the bit for generating collision is dc, define impact factorIf there are n labels to be identified in system, wherein any 1 probability not collided isIt is possible thereby to release
When obtaining m fork tree search, average timeslot number is Tm=m (1-1/m)n-1, it is possible thereby to calculate, as n < 3, T2<
T4, and as n >=3, T2> T4, using n=3 as the critical value of binary tree and quaternary tree in the algorithm, calculate impact factor at this timeAs n < 6, T4< T8, and as n >=6, T4> T8, using n=6 as quaternary tree and eight in the algorithm
The critical value of tree is pitched, impact factor at this time is calculatedSo being adopted as the μ < 0.75 that system detection goes out
Quaternary tree search is used instead as 0.75≤μ < 0.97 with binary tree search, as μ >=0.97, uses Octree search instead；
As μ < 0.75, binary tree is selected, determines new inquiry code, is pressed into query stacking, it can according to binary certainty principle
Direct Recognition goes out two labels, and return step (2)；As μ >=0.75, before reader determines inquiry according to the content of storehouse Q
Sew pre, send instruction Query (pre, c), label responds and carries out mapping code；
As 0.75≤μ < 0.97, i.e. selection quaternary tree, the information of the high two collisions prefix of label can correspond to one 4
Code is mapped, 0 completion 2 is added in inadequate 2 preamble bits；As μ >=0.97, Octree, the high three collisions prefix of label are selected
Information can correspond to a 8 bit mapping codes, 0 completion is added to 3 in inadequate 3 preamble bits；Mapping relations are respectively such as 1,2 institute of table
Show:
1 quaternary tree mapping relations of table
2 Octree mapping relations of table
Step (4): reader sends Request (pre) order, responds with the label of inquiry prefix matching, if do not had
It collides, then can identify one by one, go to step (5)；If being collided, go to step (3)；
Step (5): whether the content for judging storehouse is sky, if not empty, reads stack head prefix, is sent to label, jumps
To step (2)；If it is empty, all labels are all identified.
Embodiment:
Assuming that there is 8 labels within the scope of reader, ID is respectively A (11001000), B (10110110), C
(11001011), D (11000101), E (10001011), F (10110000), G (10111001), H (10000010), AMSMC
The identification process of algorithm is as shown in table 3.
3 AMSMC algorithm queries process of table
From table 3 it is observed that inquiring 12 times in total, 3 collisions have occurred, just identify 8 target labels, identification effect
Rate eliminates all free timeslots in adaptive multi-fork tree algorithm 60% or more, and traditional collision tree algorithm needs
15 inquiries, AMSMC algorithm increase compared to traditional algorithm performance.
To AMSMC algorithm proposed by the present invention and without idle QuadTree algorithm, CT algorithm, AMS algorithm, eight forks in Fig. 2
Total time slot of tree algorithm compares.From figure 2 it can be seen that AMSMC algorithm is compared to other algorithms, total timeslot number
It significantly reduces, is more obvious when number of labels is more, only only used 1451 time slots when 1000 number of tags.
The algorithm and Octree algorithm compare, and have used 63% timeslot number less, have compared with without idle QuadTree algorithm, used 41% less
Time slot is compared with AMS algorithm, has used 20% free timeslot less.The algorithm is by reducing with the adaptively selected of multiway tree
Collision timeslot number, and mapping code is introduced, inquiry prefix is determined according to mapping relations, successfully eliminates whole free time
Time slot, so total timeslot number greatly reduces, in comparison performance is optimal.
To AMSMC algorithm proposed by the present invention and without idle QuadTree algorithm, CT algorithm, AMS algorithm, eight forks in Fig. 3
The throughput of tree algorithm compares.It can be seen from the figure that Octree algorithm is gulped down due to that can generate a large amount of free timeslot
The rate of spitting is only 26% or so, and no free timeslot QuadTree algorithm maintains 41% or so, CT algorithmic stability 50% or so,
AMS algorithm dynamic select in binary tree and QuadTree algorithm, reduces collision time slot, and throughput can reach 55% or so.
The throughput of AMSMC algorithm has then reached 68% or so, hence it is evident that is better than other algorithms.
The preferred embodiment of the present invention has been described above in detail, but during present invention is not limited to the embodiments described above
Detail can carry out a variety of equivalents to technical solution of the present invention (in full within the scope of the technical concept of the present invention
Amount, shape, position etc.), these equivalents belong to protection of the invention.
Claims (2)
1. the adaptive multiway tree anti-collision algorithm based on mapping code, it is characterised in that: comprising steps of
Step (1): reader initial interrogation storehouse Q sends search command Request-all, so that owning in sphere of action
Label response；
Step (2): reader judges time slot state by the responsive status of all labels in its sphere of action；When only one
It when label responds, identifies successfully, and keeps label silent, go to step (5)；When what is responded simultaneously there are two the above label
When, tag-collision occurs, go to step (3)；
Step (3): determining the specific bit that collides and non-collision position according to Manchester's code principle, by collision bit it
Preceding information is pressed into storehouse Q as inquiry prefix；According to the number of tags of response simultaneously, impact factor μ is calculated, determines search fork
The value of tree and re-encoding bit length c；C=2 when quaternary tree, c=3 when Octree；
As μ < 0.75, using binary tree search；It determines new inquiry code, is pressed into query stacking, it is straight according to binary certainty principle
It connects and identifies two labels, and return step (2)；As μ >=0.75, reader determines inquiry prefix according to the content of storehouse Q
Pre, sends instruction Query (pre, c), and label responds and carries out mapping code；
As 0.75≤μ < 0.97, quaternary tree search is selected, according to table 1, the information of the high two collisions prefix of label is one 4 corresponding
0 completion 2 is added in bit mapping code, inadequate 2 preamble bits；
1 quaternary tree mapping relations of table
As μ >=0.97, Octree search is selected, according to table 2, information corresponding one 8 of the high three collisions prefix of label are reflected
Code is penetrated, 0 completion is added to 3 in inadequate 3 preamble bits；
2 Octree mapping relations of table
Step (4): reader sends Request (pre) order, responds with the label of inquiry prefix matching, if there is no
Collision, then identify, go to step (5) one by one；If colliding, go to step (3)；
Step (5): whether the content for judging storehouse is sky, if not empty, reads stack head prefix, is sent to label, jumps to step
Suddenly (2)；If it is empty, all labels are all identified.
2. adaptive multiway tree anti-collision algorithm according to claim 1, it is characterised in that: when carrying out multiway tree search,
Average timeslot number is Tm=m (1-1/m)n-1, it is possible thereby to calculate, as n < 3, T2< T4, and as n >=3, T2> T4, n=3
For the critical value of binary tree and quaternary tree, impact factor at this time is calculatedAs n < 6, T4< T8, and work as
When n >=6, T4> T8, n=6 is the critical value of quaternary tree and Octree, calculates impact factor at this time?
To as the μ < 0.75 detected, using binary tree search, as 0.75≤μ < 0.97, use quaternary tree search instead, when μ >=
When 0.97, Octree search is used instead.
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