CN101196978B - Method and system for reading RFID tags - Google Patents
Method and system for reading RFID tags Download PDFInfo
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- CN101196978B CN101196978B CN2007101868011A CN200710186801A CN101196978B CN 101196978 B CN101196978 B CN 101196978B CN 2007101868011 A CN2007101868011 A CN 2007101868011A CN 200710186801 A CN200710186801 A CN 200710186801A CN 101196978 B CN101196978 B CN 101196978B
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Abstract
A method and a system for reading radio frequency identification (RFID) tags are provided. The method includes the following steps. First, receive a tag signal from the RFID tag. Recover a data clock rate from the tag signal according to statistics of pulse lengths of the tag signal. Next, determine a frame synchronization point of a data frame following a preamble in the tag signal by a signal correlation between the preamble and a predetermined signal pattern according to the data clock rate. Finally, decode the data frame by using an adaptive Viterbi algorithm on an extended trellis diagram. The extended trellis diagram includes a plurality of nodes and a plurality of branches connecting the nodes. The nodes and the branches are arranged according to the modulation scheme of the data frame and possible variations of the data clock rate.
Description
Technical field
The present invention relates to a kind of reading rfid tags (radio frequency identificationtag, abbreviation RFID tag) method and system, and particularly relate to a kind of method and system that reads printing RFID tag (printed RFID tag).
Background technology
Fig. 1 shows a traditional radio-frequency (RF) identification reading machine 101 and three RFID tag 102-104.Reading machine 101 send ultrahigh frequency (ultra high frequency, UHF) or high frequency (highfrequency, HF) electromagnetic wave enabled labels 102-104, make label 102-104 can backscattering (backscatter) label signal to reading machine 101.The data-modulated that RFID tag sends is in this label signal.In order to detect data, this RFID tag reading machine must receive this label signal and produce above-mentioned data according to this label signal then.This Data Generation Program is called as input, decoding or demodulation.
Illustrate, RFID tag 102-104 can use FM0 modulation system (modulationscheme) to come coded data.Fig. 2 shows the datagraphic (datapattern) of four FM0 modulation systems.In Fig. 2, four figure S1-S4 are arranged.S1 or S4 representative data symbol 1.S2 or S3 representative data symbol 0.According to the FM0 modulation system, must there be a state-transition (from low state to high state or from high state to low state) between two continuous symbols.Fig. 3 is the label signal waveform example according to the FM0 modulation system, and waveform 301 is a complete muting label signal waveform.
There are two kinds of classic methods can do input, also are rim detection (edge detection) and filter (matched filtering) with coupling.The state-transition of rim detection by medium line 305 tags detected signal waveforms is then according to the statistics construction data bit again of state-transition.For example: data symbol 1 does not have state-transition in its symbol period, and data symbol 0 has state-transition in the middle of its symbol period.Rim detection is only useful when the label signal waveform has relative low noise.As shown in Figure 3, waveform 302 be one beyond 2 meters distance receive, have the label signal waveform of noise, and carrying the data identical with waveform 301.Though waveform 302 suffers the noise distortion, its datagraphic still can be rebuild by rim detection.Giving one example illustrates again, waveform 303 has the label signal waveform of noise for another distance beyond 8 meters receives, and also still carries the data identical with waveform 301.But severe noise causes waveform 303 that the false transition of many leap medium lines 305 is arranged.So, can make rim detection misread datagraphic.
Coupling is filtered has bigger noise tolerance compared with rim detection.Coupling is filtered and is mated to come the data reconstruction position by the figure between datagraphic S1-S4 and label signal waveform.Yet, correctly to work in order to allow coupling filter, the data clock speed of label signal is necessary for known, and must be stable.And the stable data clock rate is not all to obtain easily in any situation, particularly the data clock speed of printing radio frequency recognition volume label.
The printing RFID tag is by printing of inkjet printer really.The printing RFID tag is than cheap many of traditional implantation chip label.Yet the printing RFID tag has the shortcoming of very unsettled data clock speed.The data clock speed that the amplitude drift reaches 20%-50% is very typical.And its data clock speed is forever all in drift.The data clock speed of a last symbol (symbol) perhaps can be with the data clock speed difference of next symbol.Therefore, if the label signal of printing radio frequency recognition volume label has noise, it is infeasible using rim detection or coupling filtering technique.
Summary of the invention
The invention provides a kind of method of reading rfid tags, more effective than traditional reading rfid tags method.
The present invention proposes a kind of system that reads radio frequency recognition volume label.This system can solve from the clock that noise signal is arranged of printing radio frequency recognition volume label and reply, synchronously and the problem of Frame (data frame) decoding.Therefore, this system is more effective than conventional art.
The invention provides a kind of method of reading rfid tags.The method comprises the steps.At first, receive a label signal from radio frequency recognition volume label.Statistics according to the pulse length of label signal is replied its data clock speed (data clock rate).Then, carry out a Frame of this EACH_PREAMBLE_NUM_FRACs certificate is followed in the signal correction computing (signal correlation) between one section lead data (preamble) in a preset signals figure (signal patter) and the label signal in the label signal with decision synchronous points according to this data clock speed.At last, go up use adaptability viterbi algorithm (adaptive Viterbi algorithm) decoded data frame at expansion trellis diagram (extended trellis diagram), arrange the node of expanding on the trellis diagram (node) and branch line (branch) according to may changing of data clock speed.Wherein, the step of answer data clock speed more comprises: the pulse length statistics according to the label signal produces a signal histogram; Produce a plurality of figure histograms, wherein each described figure histogram all produces according to the pulse length statistics of the modulation system of the label signal of corresponding one default clock rate, and described default clock rate is to choose according to default rate interval in a preset range; Signal histogram and each described figure histogram are compared; And select the pairing default clock rate of figure histogram of approach signal histogram to be used as data clock speed.
The present invention provides a kind of system that reads radio frequency recognition volume label in addition.This system comprises receiver, replys unit, lock unit and decoding unit.Receiver receives the label signal from radio frequency recognition volume label.Reply the unit and be coupled to receiver, in order to reply the data clock speed of label signal according to the statistics of the pulse length of label signal.Lock unit is coupled to the answer unit, follows the synchronous points of a Frame of this EACH_PREAMBLE_NUM_FRACs certificate with decision in order to carry out in a preset signals figure and the label signal signal correction computing between one section lead data according to this data clock speed in the label signal.Decoding unit is coupled to lock unit, in order to use adaptability viterbi algorithm decoded data frame on the expansion trellis diagram, wherein, arranges the node and the branch line of this expansion trellis diagram according to may changing of this data clock speed.Reply the pulse length statistics generation one signal histogram of unit according to the label signal; Reply the unit and also produce a plurality of figure histograms, each described figure histogram all produces according to the pulse length statistics of the modulation system of the label signal of corresponding one default clock rate; Default clock rate is to choose according to default rate interval in a preset range; Reply the unit with the described figure histogram comparison of signal histogram and each, and select the pairing default clock rate of figure histogram of approach signal histogram to be used as data clock speed.
Description of drawings
Fig. 1 is the label reading machine of existing radio frequency recognition volume label system and the synoptic diagram of RFID tag.
Fig. 2 is the data symbol oscillogram of FM0 modulation system.
Fig. 3 shows from noiseless waveform of the type signal of radio frequency recognition volume label and two noise waveform.
Fig. 4 is the process flow diagram according to the reading rfid tags method of one embodiment of the invention.
Fig. 5 is the detail flowchart according to the clock recovery stage of one embodiment of the invention.
Fig. 6 A is the signal histogram of noisy received signal in one embodiment of the invention.
Fig. 6 B-6D is the figure histogram of muting received signal in one embodiment of the invention.
Fig. 7 shows according to the clock answering method of one embodiment of the invention and the comparison of two classic methods.
Fig. 8 shows the waveform of the lead data that standard lead data figure and several according to one embodiment of the invention receive.
Fig. 9 shows according to the method for synchronous of one embodiment of the invention and the comparison of classic method.
Figure 10 shows the trellis diagram of a traditional F M0 modulation system.
Figure 11 shows the expansion trellis diagram according to the FM0 modulation system of one embodiment of the invention.
Figure 12 shows according to the coding/decoding method of one embodiment of the invention and the comparison of classic method.
Figure 13 is for reading the calcspar of the system of radio frequency recognition volume label according to an embodiment of the invention.
The reference numeral explanation
101: the RFID tag reading machine
102-104: RFID tag
S1-S4: data symbol figure
301-303: label signal waveform
305: the medium line of label signal
410-440,421-424: the flow chart step of reading rfid tags method
800: standard lead data figure
801-803: the waveform of the lead data that receives
1000: the trellis diagram of traditional F M0 modulation system
1010: traditional trellis paths
1100: the expansion trellis diagram of the FM0 modulation system of one embodiment of the invention
1110: the trellis paths of expansion trellis diagram
1101: the node of expansion trellis diagram
1102: the branch line of expansion trellis diagram
1103: the super node of expansion trellis diagram
1300: the system of reading rfid tags
1301: receiver
1302: reply the unit
1303: lock unit
1304: decoding unit.
Embodiment
In typical label signal, RFID tag can repeat the transmission data continuously.The label data of Chong Fuing all is included in the Frame the inside each time.And guide each Frame by lead data.Each lead data and Frame comprise a plurality of symbols.Fig. 4 is the emphasis process flow diagram according to the reading rfid tags method shown in one embodiment of the invention.At first, receive label signal (being step 410), reply the data clock speed (being step 420) of label signal then from RFID tag.After identifying data clock speed, carry out synchronisation steps, calculate lead data and follow the position (being step 430) of the frame synchronization point between the Frame of this EACH_PREAMBLE_NUM_FRACs certificate.The point that this frame synchronization point begins for lead data end and Frame.After identifying data clock speed and frame synchronization point, this flow process will proceed to decode this Frame and obtain label data (being step 440).
Though circuit differences causes the data clock rate drift of printing RFID tag, yet this drift is slower with respect to symbol period, and the method step of present embodiment can adapt to clock drift.Therefore, the data clock speed of being replied by label signal can be used for calculating the frame synchronization point.The data clock speed of replying can also be used for being used as initial clock rate and decode and follow Frame after frame synchronization point.The step of Fig. 4 is described in detail as follows.
In the present embodiment, clock return phase (step 420 of Fig. 4) can further resolve into 4 step 421-424 of Fig. 5.At first, the pulse length statistics according to label signal produces signal histogram (signal histogram) (being step 421).Work as example with the FM0 modulation system and do explanation.One of label signal part (promptly not passing through medium line) that does not have state-transition is represented in a pulse herein.Pulse length is then represented the length between two continuous states of label signal change.Fig. 6 A shows from the printing RFID tag and the signal histogram of the label signal with noise that comes.The probability statistics of the pulse length of the signal histogram display label signal of Fig. 6 A.The Z-axis representative of signal histogram is from probability mass function (probability mass function, probability size PMF) of pulse length.The transverse axis of signal histogram is represented pulse length.The unit of pulse length is a sampling spot number within the pulse.The RFID tag reading machine is with default fixed intervals sampling label signal.As shown in Figure 6A because serious noise, in the signal histogram the most normal appearance be that length is the extremely short pulse of a sampling spot.
Produce after the signal histogram, flow process proceeds to produce a plurality of figure histograms (patternhistogram) (being step 422).Each figure histogram is that the pulse length statistics according to the modulation system (being FM0 at present embodiment) of the label signal that meets a default clock rate produces, and the default clock rate of these figure histograms is to select according to the clock rate interval of presetting within preset range.Illustrate, Fig. 6 B-6D is presented at three kinds of figure histograms that produce under the method.The representative of the figure histogram of each Fig. 6 B-6D meets the probability statistics of pulse length of noiseless label signal of the FM0 modulation system of default clock rate separately.Shown in Fig. 2 and 6B-6D, according to the FM0 modulation system two kinds of pulse kenels are arranged, promptly be short pulse and long pulse.The probability of short pulse is the twice of long pulse.If the default clock rate of corresponding a certain figure histogram is four times of RFID tag reading machine sampling frequency, the figure histogram that is then produced such as Fig. 6 B.If the default clock rate of corresponding a certain figure histogram is six times of RFID tag reading machine sampling frequency, the figure histogram that is then produced such as Fig. 6 C.If the default clock rate of corresponding a certain figure histogram is the octuple of RFID tag reading machine sampling frequency, the figure histogram that is then produced such as Fig. 6 D.The possible mobility scale of the data clock speed that comprises the printing RFID tag is set the preset range of above-mentioned default clock rate in suggestion.
Produce after the figure histogram, flow process is proceeded comparison signal histogram and each figure histogram (being step 423), selects the default clock rate of the figure histogram of approach signal histogram to be used as the data clock speed (being step 424) of label signal then.For example, can be chosen in the figure histogram that has smallest match mistake (minimum matching error) in all figure histograms in the present embodiment.
For clock answer preferably, in other embodiments of the invention, the noiseless pulse on the figure histogram can use the Gaussian profile figure (Gaussian profile) based on noiseless pulse to replace.It is easier and have the signal histogram coupling of noise to have the figure histogram of Gaussian profile figure, can reply data clock speed more accurately.In addition, in other embodiments of the invention, because the figure histogram is not associated with other label signal, so the figure histogram can result from and receive before other label signal, and in repeated use after a while.In this case, after the figure histogram produced, step 422 can be left in the basket in the fetch program at ensuing label.
Fig. 7 is according to the two kinds of clock answering methods of present embodiment and the comparison of two kinds of classic methods.The logarithm square error of the symbol period that the Z-axis of Fig. 7 is replied for each method (mean square error, MSE).The lower preferable clock recoverability of square error representative.The transverse axis of Fig. 7 be the label signal that received signal to noise ratio (S/N ratio) (signal-to-noise ratio, SNR).Lower signal to noise ratio (S/N ratio) representative is than the label signal of tool noise.Fig. 7 compares four kinds of methods altogether, is respectively first test method(s) (First Trial), most method (Majority), simple statistics method (Simple Statistics) and advances rank statistic law (Advanced Statistics).First test method(s) is a classic method, and way is to take the label signal pulse length of state-transition for the first time, calculates the inverse of its symbol period then and is used as data clock speed.The method is very simple, can only operate under the stable and high situation of signal to noise ratio (S/N ratio), but for the printing RFID tag, have stable and high signal to noise ratio (S/N ratio) hardly.Most methods are another kind of classic method, and way is to obtain the repeatedly a plurality of pulse lengths between the state-transition of label signal, then on average coming the compute sign cycle by majority voting (ma jority vote) or pulse length.Compute sign cycle reciprocal and be assigned therein as data clock speed afterwards.The method is comparatively complicated, when signal to noise ratio (S/N ratio) on during level usefulness good slightly.Yet, waveform 303 as shown in Figure 3, when signal to noise ratio (S/N ratio) was very high, severe noise caused the false transformation of many signal conditions.The short pulse that first test method(s) and most method all cause because of false transition and performing poor.Simple statistics method according to one embodiment of the invention is the clock answering method that comprises the figure histogram of noiseless pulse, is the clock answering method that comprises the figure histogram of Gaussian profile figure and advance the rank statistic law according to another embodiment of the present invention.As shown in Figure 7, no matter these the two kinds methods according to present embodiment all can be better than traditional method under the low or high situation of signal to noise ratio (S/N ratio).The usefulness of advancing the rank statistic law in addition can be more better than simple statistics Fa Laide.
After data clock was replied, next stage was the frame synchronization point of following the Frame of lead data in the computation tag signal.Present embodiment carries out the signal correction computing between a lead data and a preset signals figure that calculates according to data clock speed (signal pattern).More particularly, this preset signals figure is the defined lead data figure of standard specification (preamble pattern) that the printing RFID tag is followed.In addition, the signal correction computing that is used in present embodiment is window slip related operation (window-sliding correlation).Since the frame synchronization point is a lead data finish to begin with Frame in, present embodiment utilizes signal correction computing decision lead data in the position of label signal, just can determine to follow in the label signal position of the Frame of lead data then.
Please refer to Fig. 8 now, the lead data waveform 801-803 that Fig. 8 shows the defined lead data figure 800 of standard specification and receives from label, waveform 801-803 is based on three kinds of different data clock speed.Lead data waveform 800 knows usually that for be defined in the standard specification and have in the technical field for this reason the knowledgeable is known.Lead data 801-803 is similar to lead data figure 800.Lead data 801-803 and lead data figure 800 do not exist together that drift is caused by noise and data clock.The window slip related operation of present embodiment is meant that the lead data waveform that will receive slides from left to right and crosses over the lead data figure 800 of standard.Frame is just since the best match position of two figures.The data clock speed of replying in step 420 is an estimation of the data clock speed of the lead data that receives of reading machine.Even this estimation has some not match with the data clock speed of the lead data of actual reception, window slip related operation is still effective.If but the data clock speed of the lead data of above-mentioned estimation and actual reception differs too much, window slip related operation will be failed.Here it is, and why data clock speed must be estimated before data-frame sync.The data clock speed of estimating in step 420 provides good reference point to the signal correction computing.The length that please notes standard lead data figure 800 may have decisive influence to synchronous accuracy.The length of lead data figure 800 is long more, and the degree of accuracy of data-frame sync is just high more.
Fig. 9 shows a kind of conventional synchronization method and according to the comparison of a kind of method for synchronous of present embodiment.The Z-axis of Fig. 9 is the square error of the synchronisation offset (synchronizationoffset) of linear graduation (linear).The transverse axis of Fig. 9 is the signal to noise ratio (S/N ratio) of the label signal that receives.Power critical method (Power Threshold) is the conventional synchronization method, and way is the starting point that the state-transition first time of the label signal that will be received is considered as Frame.In the comparison of Fig. 9, the power critical method has two kinds of variations.First kind change to be used length is that the lead data of four symbols is done synchronously label signal.Second kind change to be used length is that the lead data of ten symbols is done synchronously label signal.Related operation method (Correlator) is the method for synchronous according to present embodiment.Similarly, in the comparison of Fig. 9, the related operation method also has two kinds of variations.First kind change to be used length is that the lead data of four symbols is done synchronously label signal.Second kind change to be used length is that the lead data of ten symbols is done synchronously label signal.As shown in Figure 9, the usefulness of related operation method is much better than the power critical method, and long lead data performance is preferable.
After calculating frame synchronization point, next step is the decoded data frame with construction again from the data of label.In order to overcome the drift of noise and data clock, present embodiment uses adaptability viterbi algorithm decoded data frame on the expansion trellis diagram.The expansion trellis diagram is the extension of traditional trellis diagram.For example Figure 10 shows traditional trellis diagram 1000, and Figure 11 shows the expansion trellis diagram 1100 of being derived by traditional F M0 trellis diagram.Spread F M0 trellis diagram 1100 comprises the branch line (for example branch line 1102) of a plurality of nodes (for example node 1101) and a plurality of connected nodes.Wherein come arranged nodes and branch line with may changing of data clock speed according to the modulation system (is FM0 at present embodiment) of Frame.
As shown in figure 11, the node in the expansion trellis diagram is formed a plurality of super nodes.Each super node comprises three nodes, as super node 1103.Super node on the expansion trellis diagram 1100 is similar to the node on traditional trellis diagram 1000.Arrange super node according to the issuable symbol sebolic addressing of Frame modulation system.On the other hand, arrange each super node node wherein according to may changing of data clock speed.It is that the data clock speed of last symbol deducts a default clock rate unit that node above being among the super node is represented the data clock speed of present symbol.For example Yu She clock rate unit can be the sampling frequency of RFID tag reading machine.The node that mediates among super node represents the data clock speed of present symbol identical with previous symbol.It is that the data clock speed of last symbol adds default clock rate unit that node below being among the super node is represented the data clock speed of present symbol.Therefore application adaptability viterbi algorithm (Viterbi algorithm) can solve the problem of noise and data clock drift on expansion trellis diagram 1100.
Super node on expansion trellis diagram 1100 can extend to and comprise more nodes.For example each super node can comprise five nodes, but not three nodes among Figure 11.In the super node that comprises five nodes, it is that the data clock speed of last symbol deducts two default clock rate unit that uppermost node is represented the data clock speed of present symbol, it is that the data clock speed of last symbol adds two default clock rate unit that nethermost node is represented the data clock speed of present symbol, and its excess-three node is identical with foregoing original three nodes.The rest may be inferred, and each super node can further extend to and comprise that more nodes are to adapt to bigger data clock range of drift.General rule is must be corresponding one by one between all nodes among each super node and a plurality of default clock rate.And above-mentioned default clock rate must be in a preset range be chosen according to default rate interval, this preset range must be covered by Frame during in may the changing of data clock speed.
Present embodiment uses adaptability viterbi algorithm decoded data frame.The adaptability viterbi algorithm can adapt to the timing variations of data clock rate drift and frame synchronization point on certain degree.The decoded data frame can be divided into three steps.First step be each super node as being a single node, and in the expansion trellis diagram corresponding first trellis paths of finding out minimal error in might the possessive case subpath (trellis path) of state transitions.This step is similar to and finds out the minimal error path on traditional trellis diagram, for example the path 1010 that indicates with thick line among Figure 10.Second step is respectively to get among each super node on first trellis paths in the possessive case subpath that a node connected into, and finds out second trellis paths of minimal error, as the path 1110 that indicates with thick line among Figure 11.Last the 3rd step provides by the result of the indicated leftmost symbol of above-mentioned second trellis paths as the decoded data frame.
Figure 12 shows the comparison according to the coding/decoding method of present embodiment and two kinds of classic methods.The Z-axis of Figure 12 is the bit error rate (bit error rate) of coding/decoding method.The transverse axis of Figure 12 is the signal to noise ratio (S/N ratio) of the label signal that received.Edge detection method and coupling filtration method all are traditional coding/decoding methods that the prior art of front is partly mentioned.The adaptability viterbi algorithm then is the coding/decoding method according to present embodiment.As shown in figure 12, no matter signal to noise ratio (S/N ratio) is low or high, and the adaptability viterbi algorithm all has minimum bit error rate.
Except the method for the reading rfid tags of above embodiment, the present invention also comprises the system of reading rfid tags.Please refer to Figure 13, system 1300 is the system of reading rfid tags according to another embodiment of the present invention.This system comprises receiver 1301, replys unit 1302, lock unit 1303 and decoding unit 1304.Reply unit 1302 and be coupled to receiver 1301.Lock unit 1303 is coupled to replys unit 1302.Decoding unit 1304 is coupled to lock unit 1303.The label signal that receiver 1301 receives from RFID tag.Reply unit 1302 and reply the data clock speed of label signal according to the pulse length statistics of label signal.Lock unit 1303 carries out in a preset signals figure and the label signal Frame of this EACH_PREAMBLE_NUM_FRACs certificate is followed in signal correction computing between one section lead data in label signal with decision frame synchronization point position according to this data clock speed.Decoding unit 1304 uses adaptability viterbi algorithm decoded data frame on the expansion trellis diagram.
In fact, the method as the flow performing reading rfid tags of Fig. 4 is abideed by by system 1300.There is corresponding relation closely between the flow process of Fig. 4 and the system 1300.Receiver 1301 execution in step 410.Reply unit 1302 execution in step 420.Lock unit 1303 execution in step 430.Decoding unit 1304 execution in step 440.Because the ins and outs of step 410-440 have been exposed among the embodiment of front, do not repeat them here.
In sum, method and system provided by the invention uses the signal statistics data to reply the data clock speed of label signal, use signal graph related operation decision frame synchronization point position, and use adaptability viterbi algorithm decoded data frame at the expansion trellis diagram.Therefore, method and system provided by the invention is for the usefulness that has noise signal have be better than classic method of decoding from the printing RFID tag.The adaptability viterbi algorithm is the error of tolerable data clock drift and frame synchronization point to a certain extent.Therefore, in recovery stage data estimator clock rate and calculate frame synchronization point at synchronous phase and do not need very accurate.The problem that this data clock that helps to overcome the printing RFID tag drifts about often.The usefulness of method and system provided by the present invention is similar to maximum likelihood demoder (maximum likelihooddecoder, ML decoder).Yet the complexity of method and system provided by the present invention is far below the maximum likelihood demoder, and this is because method and system of the present invention is just followed the trail of character boundary, rather than the border of each symbol of calculating of being done as the maximum likelihood demoder.In addition, though only using, the method and system of the foregoing description reading the printing RFID tag, method and system of the present invention also can be signed the excellent usefulness of performance, the label that for example reads non-printing RFID tag and follow the electronic product code first order/second generation standard (Electronic Product CodeClass 1/Generation 2) at the radio frequency identification marking that reads other kind.
Though the present invention discloses as above with embodiment; right its is not in order to limit the present invention; have in the technical field under any and know the knowledgeable usually; without departing from the spirit and scope of the present invention; when can doing a little change and retouching, so protection scope of the present invention is as the criterion when looking the claim person of defining of the present invention.
Claims (26)
1. the method for a reading rfid tags comprises:
Receive a label signal from this radio frequency recognition volume label;
Statistics according to the pulse length of this label signal is replied a data clock speed from this label signal;
Carry out a Frame of this lead data is followed in the signal correction computing between the lead data in a preset signals figure and this label signal in this label signal with decision the position of frame synchronization point according to this data clock speed; And
On an expansion trellis diagram, use an adaptability viterbi algorithm this Frame of decoding, wherein, arrange node and branch line on this expansion trellis diagram according to may changing of this data clock speed,
Wherein, the step of replying this data clock speed more comprises:
Pulse length statistics according to this label signal produces a signal histogram;
Produce a plurality of figure histograms, wherein, each described figure histogram all produces according to the pulse length statistics of the modulation system of the label signal of corresponding one default clock rate, and described default clock rate is to choose according to default rate interval in a preset range;
This signal histogram and each described figure histogram are compared; And
Select default clock rate to be used as this data clock speed near this figure histogram of this signal histogram is pairing.
2. the method for reading rfid tags as claimed in claim 1, wherein, this preset range is the possible mobility scale of the data clock speed of this radio frequency recognition volume label.
3. the method for reading rfid tags as claimed in claim 1, wherein, each described figure histogram representative is to the noiseless probability statistics of the pulse length of the modulation system of the label signal that should preset clock rate.
4. the method for reading rfid tags as claimed in claim 1, wherein, each described figure histogram comprises the Gaussian profile figure that the noiseless probability statistics to the pulse length of the modulation system of the label signal that should preset clock rate are produced.
5. the method for reading rfid tags as claimed in claim 1, wherein, the defined lead data figure of standard specification that this preset signals figure is followed for this radio frequency recognition volume label.
6. the method for reading rfid tags as claimed in claim 1, wherein, this signal correction computing is a window slip related operation.
7. the method for reading rfid tags as claimed in claim 1, wherein, described node constitutes a plurality of super nodes, and each described super node comprises a plurality of described nodes.
8. the method for reading rfid tags as claimed in claim 7 wherein, is arranged described super node according to the modulation system of this Frame.
9. the method for reading rfid tags as claimed in claim 7 wherein, is arranged node among each described super node according to may changing of this data clock speed.
10. the method for reading rfid tags as claimed in claim 7 wherein, has relation one to one between the described node of each described super node and a plurality of default clock rate.
11. the method for reading rfid tags as claimed in claim 10, wherein, described default clock rate is selected according to default rate interval in a preset range.
12. the method for reading rfid tags as claimed in claim 11, wherein, this data clock speed may change within this preset range comprised during this Frame.
13. the method for reading rfid tags as claimed in claim 7 wherein, uses the decode step of this Frame of this adaptability viterbi algorithm more to comprise on this expansion trellis diagram:
Each described super node is considered as a single node, and in this expansion trellis diagram corresponding one first trellis paths of finding out minimal error in might the possessive case subpath of state transitions;
Respectively get among each described super node on this first trellis paths in the possessive case subpath that a node connected into, find out one second trellis paths of minimal error; And
The result of an indicated symbol of this second trellis paths as this Frame of decoding is provided.
14. a system that reads radio frequency recognition volume label comprises:
One receiver receives the label signal from a radio frequency recognition volume label;
One replys the unit, is coupled to this receiver, in order to reply the data clock speed of this label signal according to the statistics of the pulse length of this label signal;
One synchronous unit, be coupled to this answer unit, in this label signal, follow the position of frame synchronization point of a Frame of this lead data with decision in order to carry out the signal correction computing between the lead data in a preset signals figure and this label signal according to this data clock speed; And
One decoding unit is coupled to this lock unit, uses an adaptability viterbi algorithm this Frame of decoding on an expansion trellis diagram, wherein, arranges node and branch line on this expansion trellis diagram according to may changing of this data clock speed,
Wherein, this replys the pulse length statistics generation one signal histogram of unit according to this label signal;
Wherein, this answer unit also produces a plurality of figure histograms, and each described figure histogram all produces according to the pulse length statistics of the modulation system of the label signal of corresponding one default clock rate;
Wherein, described default clock rate is to choose according to default rate interval in a preset range;
Wherein, this answer unit compares this signal histogram and each described figure histogram, and selects should default clock rate be used as this data clock speed near this figure histogram of this signal histogram is pairing.
15. the system that reads radio frequency recognition volume label as claimed in claim 14, wherein, this preset range is the possible mobility scale of the data clock speed of this radio frequency recognition volume label.
16. the system that reads radio frequency recognition volume label as claimed in claim 14, wherein, each described figure histogram is represented the noiseless probability statistics to the pulse length of the modulation system of the label signal that should preset clock rate.
17. the system that reads radio frequency recognition volume label as claimed in claim 14, wherein, each described figure histogram comprises the Gaussian profile figure that the noiseless probability statistics to the pulse length of the modulation system of the label signal that should preset clock rate are produced.
18. the system that reads radio frequency recognition volume label as claimed in claim 14, wherein, the defined lead data figure of standard specification that this preset signals figure is followed for this radio frequency recognition volume label.
19. the system that reads radio frequency recognition volume label as claimed in claim 18, wherein, this signal correction computing is a window slip related operation.
20. the system that reads radio frequency recognition volume label as claimed in claim 14, wherein, described node constitutes a plurality of super nodes, and each described super node comprises a plurality of described nodes.
21. described super node wherein, is arranged according to the modulation system of this Frame by the system that reads radio frequency recognition volume label as claimed in claim 20.
22. node among each described super node wherein, is arranged according to may changing of this data clock speed by the system that reads radio frequency recognition volume label as claimed in claim 20.
23. wherein, there is relation one to one in the system that reads radio frequency recognition volume label as claimed in claim 20 between the described node of each described super node and a plurality of default clock rate.
24. the system that reads radio frequency recognition volume label as claimed in claim 23, wherein, described default clock rate is selected according to default rate interval in a preset range.
25. the system that reads radio frequency recognition volume label as claimed in claim 24, wherein, this data clock speed may change within this preset range comprised during this Frame.
26. the system that reads radio frequency recognition volume label as claimed in claim 20, wherein, this decoding unit is considered as a single node with each described super node, and corresponding one first trellis paths of finding out minimal error in might the possessive case subpath of state transitions in this expansion trellis diagram, respectively get among each described super node on this first trellis paths then in the possessive case subpath that a node connected into, find out one second trellis paths of minimal error, the result of an indicated symbol of this second trellis paths as this Frame of decoding is provided then.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US86854306P | 2006-12-05 | 2006-12-05 | |
| US60/868,543 | 2006-12-05 |
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| CN101196978A CN101196978A (en) | 2008-06-11 |
| CN101196978B true CN101196978B (en) | 2010-09-15 |
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| CN2007101868011A Expired - Fee Related CN101196978B (en) | 2006-12-05 | 2007-11-14 | Method and system for reading RFID tags |
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| TW (1) | TWI334576B (en) |
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| US7986217B2 (en) * | 2007-09-27 | 2011-07-26 | Intel Corporation | Mitigating processing latency in RFID exchanges |
| CN102932105B (en) * | 2012-10-31 | 2016-02-17 | 上海坤锐电子科技有限公司 | Based on the coding/decoding method that the FM0 of viterbi algorithm encodes |
| CA3129198A1 (en) * | 2019-02-08 | 2020-08-13 | Allflex Australia Pty Ltd | Electronic animal identification tag reader synchronisation |
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| CN1388903A (en) * | 2000-06-23 | 2003-01-01 | 密克罗奇普技术公司 | Method, system and apparatus for calibrating a pulse position modulation (PPM) decoder to a PPM signal |
| CN1601547A (en) * | 2004-10-21 | 2005-03-30 | 复旦大学 | Power self-adaptive variable data rate communicator and method based on RF identification |
| CN1630825A (en) * | 2002-08-01 | 2005-06-22 | 株式会社日立制作所 | Interrogator of moving body identification device |
| CN1790367A (en) * | 2005-12-28 | 2006-06-21 | 北京邮电大学 | Modulation and demodulation method for electronic label detection of RFID system |
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2007
- 2007-08-13 TW TW96129846A patent/TWI334576B/en not_active IP Right Cessation
- 2007-11-14 CN CN2007101868011A patent/CN101196978B/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1388903A (en) * | 2000-06-23 | 2003-01-01 | 密克罗奇普技术公司 | Method, system and apparatus for calibrating a pulse position modulation (PPM) decoder to a PPM signal |
| CN1630825A (en) * | 2002-08-01 | 2005-06-22 | 株式会社日立制作所 | Interrogator of moving body identification device |
| CN1601547A (en) * | 2004-10-21 | 2005-03-30 | 复旦大学 | Power self-adaptive variable data rate communicator and method based on RF identification |
| CN1790367A (en) * | 2005-12-28 | 2006-06-21 | 北京邮电大学 | Modulation and demodulation method for electronic label detection of RFID system |
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| TWI334576B (en) | 2010-12-11 |
| CN101196978A (en) | 2008-06-11 |
| TW200825941A (en) | 2008-06-16 |
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