Summary of the invention
Technical matters to be solved by this invention is, a kind of multiple tag access method that is used for radio-frequency (RF) identification is provided, and reduces the label collision, realizes the access rapidly and efficiently of many labels.
The invention provides a kind of multiple tag access method that is used for radio-frequency (RF) identification, comprise the steps:
(1) after the reader initialization finishes, sends selection instruction the label of effective on-site is selected;
(2) reader sends the label incoming instruction, begins to receive label, comprises the affirmation information that label is replied frame length information, replied probabilistic information and label is replied in this label incoming instruction;
(3) label of selecting access selects a time slot to reply according to the information in the incoming instruction arbitrarily according to the answer probability in the instruction, in present frame;
(4) reader receives the label return information in the preset time interval, and utilize leading random pulses collision detection method to detect in the described label return information whether conflict is arranged, whether reader is according to there being conflict to upgrade information in the incoming instruction, change the access of next frame over to, return step (2), after reader sends the label incoming instruction, no longer include label and reply, then finish access process.
Whether further, utilize leading random pulses collision detection method to detect in the described label return information in the described step (4) has the step of conflict to comprise:
Reader is noted detected pulse number, and as the number of replying label in this time slot, if number is 0, then this time slot does not have label to insert with this number; If number is 1, then this time slot has 1 label successfully to insert; If number is the integer greater than 1, this time slot label collision then, the number of collision labels is detected pulse number.
Further, the step of upgrading the information in the incoming instruction according to the label return information in the described step (4) comprises:
A, in the label access procedure, the initial value of establishing frame length is N
0, be N at the frame length of i frame
i〉=0 and be integer, i 〉=0 and be integer wherein;
B, be r in the number of i the detected answer label of frame
i, its initial value r
0=0, the frame length N of i+1 frame then
I+1=N
i+ r
i, wherein, r
i=g
i-e
i-s
i, g
iBe the number of tags of colliding in i the frame and be integer, e
iRepresent to reply in i the frame number of tags, s for sky
iRepresent to insert in i the frame successful number of tags;
C, label be at i frame, the selection of the answer timeslot number of selection interval be [1, N
i], select the probability of each interval interior each time slot to be
Wherein,
D, frame length, answer probabilistic information that the label that obtains in the above-mentioned steps is replied are updated in the incoming instruction of reader.
Further, label described in the step (1) is to utilize leading random pulses collision detection method to add the label of random pulses burst region in the leader of Frame.
Further, described step (1) comprising:
The reader initialization, finish the preliminary work with label communication;
Reader sends selection instruction at effective on-site, after label is received selection instruction, mates with alternative condition information in the selection instruction, and the label that satisfies alternative condition enters the label access procedure, and responsive tags inserts relevant instruction.
Further, the affirmation information that label is replied described in the step (2), when the label incoming instruction sends first or when label taking place replying conflict, this information be sky; Described label is replied frame length information, is meant the time width that the label selection is replied, and represents with timeslot number.
Method of the present invention, utilize leading random pulses collision detection method, the tags detected collision, and, redefine the parameter information in the reader reception instruction, and it is upgraded according to the label return information, make that frame length information, probabilistic information when many labels insert are more accurate, reduce the probability of label collision, can realize the access efficiency of many labels, reduced time delay.
Embodiment
, be described in further detail multiple tag access method of the present invention below in conjunction with drawings and the specific embodiments.
As shown in Figure 1, the frame structure synoptic diagram that has shown the label answer data that the present invention relates to.The characteristics of described label restore data frame are: added the random pulses burst region in the leader of Frame.This random pulses burst region is divided into the plurality of sub time interval again, and desire sends the label that this Frame inserts reader, and picked at random is one from these sub-time intervals, and at the interval burst that produces a high level of selected sub-time.All the other times of described random pulses burst region are low level.When a time slot began, all replied label synchronized transmission Frame, and the reader end detects burst in the preset time window, and the record number, thereby determined the number of collision labels in current this time slot.
As shown in Figure 2, shown the idiographic flow of the multiple tag access method that uses this present invention, comprised the steps:
Step 1, the reader initialization mainly is to finish preliminary work with label communication, the i.e. S1 of Fig. 2 by reader.
Step 2, reader is selected the label of effective on-site, i.e. the S2 of Fig. 2.At first, reader sends selection instruction, and after label was received selection instruction, the conditional information in the and instruction mated, and the label that satisfies alternative condition enters the label access procedure, and response inserts relevant instruction with label.
Step 3, reader sends the label incoming instruction, begins to receive label, i.e. the S3 of Fig. 2.
Wherein, the parameter information that comprises in the described label incoming instruction comprises at least: the affirmation information that label is replied frame length information, replied probabilistic information and label is replied.The described affirmation information that label is replied, when sending first and label takes place replying conflict, this information be sky.Described label is replied the time width that frame length information is meant that the label selection is replied, and represents with timeslot number.
Step 4, label with certain probability, select a time slot to reply in present frame arbitrarily, i.e. the S4 of Fig. 2 according to the information in the incoming instruction.
Step 5, reader receives the label return information and it is handled in preset time interval (or claiming frame), i.e. the S5 of Fig. 2; Simultaneously, upgrade the information in the incoming instruction, change the access of next frame over to,, promptly the S6 of Fig. 2 and S3 return step 3.
Wherein, reader is meant to receiving handling of information whether the test returns label information has conflict.The described detection of should dashing forward is the method realization by leading random pulses collision detection.The specific practice of utilizing the method for this leading random pulses collision detection to carry out collision detection is the number that recording impulse under the condition is set in certain parameter, represents this time slot to reply the number of label with number.Reader is noted detected pulse number, and as the number of replying label in this time slot, if number is 0, then this time slot does not have label to insert with this number; If number is 1, then this time slot has 1 label successfully to insert; If number is the integer greater than 1, this time slot label collision then, the number of collision labels is detected pulse number.
Wherein, upgrade the information in the incoming instruction, be meant that upgrading above-mentioned label replys frame information and probabilistic information, it is according to reader the judged result of the return information that receives to be adjusted that institute does renewal, and specifically method of adjustment is as follows:
In the label access procedure, the initial value of establishing frame length is N
0, be N at the frame length of i frame
i(i 〉=0, and be integer; N
i〉=0, and be integer); Number at i the detected answer label of frame is r
i, its initial value r
0=0, then
N
i+1=N
i+r
i (1)
Wherein,
r
i=g
i-e
i-s
i (2)
In the formula (2), g
iBe the number of tags of colliding in i the frame, and be integer; e
iRepresent to reply in i the frame number of tags for sky; s
iRepresent to insert in i the frame successful number of tags.
Label is at i frame, the selection of the answer timeslot number of selection interval be [1, N
i], selecting the probability of each interval interior each time slot is p
i, then
Wherein,
As shown in Figure 3, suppose that reader is selected after, have 4 labels to participate in checking, but for reader, number of tags is unknown, suppose that the initial value of frame length estimation is 3, the access procedure of then described 4 labels is as follows:
(A) reader sends the label incoming instruction, begins to receive label.
If the initial value N that the number of tags in the instruction is estimated
0Be 3, after label is received instruction as can be known by formula (3), with p
1Be that 1/3 probability selects in 3 time slots any one to reply.
(B) reader begins the reception of first frame.
The answer that reader is received 1 label at first time slot, label successfully inserts; Second time slot of reader is received as sky; Reader detects 3 labels at the 3rd time slot and replys, and label bumps.Therefore, behind first frame end, g
1Be 3, e
1Be 1, s
1 Be 1, so r
1Be 1, N
2Be 4.
(C) reader sends the label incoming instruction, can get by formula (1) and formula (2), at this moment, frame length estimated value N
2Be 4; By formula (3) as can be known, label is with p
2Be 1/4 probability, select in 4 time slots any one to reply.
(D) reader begins the reception of second frame.
Reader receives the answer of 1 label at first time slot, successfully inserts; Reader is received as sky at second time slot; The 3rd time slot, reader detects the answer of 2 labels, bumps; The 4th time slot is received as sky; Therefore, behind second frame end, g
2Be 2, e
2Be 2, s
2 Be 1, according to as can be known by formula (1) and formula (2), r
2Be-1, N
3Be 3.
(E) reader sends the label incoming instruction, can get by formula (1) and formula (2), at this moment, frame length estimated value N
3Be 3; By formula (3) as can be known, label is with p
3Be 1/3 probability, select in 3 time slots any one to reply.
(F) reader begins the reception of the 3rd frame.
Reader is at first time slot, and the answer that receives 1 label successfully inserts; At second time slot, be received as sky; At the 3rd time slot, the answer that receives 1 label successfully inserts.
(H) as can be known, frame length N by formula (1) and (2)
4Be updated to 0, whole access process finishes.In whole access process, successfully inserted 4 labels, be three frames service time, 10 time slots, percent of pass are 0.4, near theoretical maximum 0.426.
Step 6 after reader sends the label incoming instruction, no longer includes label and replys, and then finishes access process.