CN109886052A - A kind of restoration methods of ultrahigh frequency RFID label signal - Google Patents
A kind of restoration methods of ultrahigh frequency RFID label signal Download PDFInfo
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Abstract
The present invention discloses a kind of ultrahigh frequency RFID label signal restoration methods comprising following steps: step S1. is based on down conversion module and received radiofrequency signal is down-converted to base band；Step S2. eliminates the carrier component in digital baseband signal based on the baseband signal after digitlization, using carrier cancellation module, according to the DC component in DC component cancellation module removal signal；Step S3. estimation label quantity and channel coefficient matrix；Step S4. is based on label signal separation module and restores each RFID label tag signal.This method reduces the loss in efficiency because caused by increasing number of labels, can significantly improve the handling capacity of RFID system using the statistical information of redundancy in label collision signal.
Description
Technical field
The present invention relates to signal processing technology more particularly to a kind of ultrahigh frequency RFID label signal restoration methods.
Background technique
In recent years, radio frequency identification (RFID) technology has been successfully applied to many different fields, if storehouse is taken inventory, asset tracking
And person identification.In typical multi-tag hyperfrequency (UHF) RFID system, different passive labels can be reversed simultaneously
The information for scattering them causes label signal interfering with each other.This phenomenon is commonly known as label collision, to RFID system
The decline of access efficiency has apparent influence.In the various RFID standards including ISO 18000-6C, solves this and ask
A kind of common solution of topic is the CDMA slotted ALOHA algorithm based on frame structure.But this kind of algorithm is only capable of processing comprising one
The time slot of label signal, therefore its maximum system throughput is limited.
Recently, the time slot of conflict is converted into available time slot by decomposing collision signal, thus in physical layer solution award of bid
Label conflict becomes a new research hotspot.However, current physical layer anti-collision algorithms all have ignored one of label signal
Key statistics characteristic, i.e., when observing label signal by the card reader of quadrature receiving structure, it is believed that reader or label
The real value RFID waveform of generation is a kind of non-circular complex signal with maximum non-circular characteristic.For non-circular complex signal, when connecing
When the collection of letters number and its complex conjugate are handled simultaneously, additional performance gain can be obtained, this solution is commonly known as width
Linearly (WL) is handled.In the label anti-confliction problem of passive UHF RFID system, WL processing method does not have application also.
Summary of the invention
In view of the problems of the existing technology, the present invention proposes a kind of ultrahigh frequency RFID label signal restoration methods, base
In wide linear minimum mean-squared error (WLMMSE) criterion, this method is reduced using the statistical information of redundancy in label collision signal
The loss in efficiency because caused by increasing number of labels can significantly improve the handling capacity of RFID system.
To achieve the above object the present invention adopts the following technical scheme:
One kind being based on ultrahigh frequency RFID label signal restoration methods, comprising:
Down conversion module, for the received radiofrequency signal of receiving antenna to be down-converted to base band；Carrier cancellation module, is used for
Offset the carrier signal that the transmission antenna for receiving and including in signal issues；DC component cancellation module is returned for removing label
Switch modulation signal (OOK) signal in DC component, be converted into binary phase shift keying (BPSK) signal；
Number of labels estimation module is used for estimation label quantity；
Channel estimation module, for estimating channel coefficient matrix；
Label signal separation module, for using based on wide linear MMSE criterion by the label signal of conflict into
Row separation；
Described method includes following steps:
Step S1. is based on down conversion module and received radiofrequency signal is down-converted to base band；
Step S2. eliminates the carrier wave in digital baseband signal to the baseband signal after down coversion, using carrier cancellation module
Component, according to the DC component in DC component cancellation module removal signal；
Step S3. estimation label quantity and channel coefficient matrix；
Step S4. is based on label signal separation module and restores each RFID label tag signal.
Preferably, also include in step S2, according to the DC component in DC component cancellation module removal signal, by its turn
It is changed to binary phase shift keying (BPSK) signal.
Preferably, also include S0 before step S1, obtain one of block of information of multi-tag signal response, as wait divide
From block of information.
Preferably, step S1 includes that the corresponding radiofrequency signal of the block of information is down-converted to base band；
Preferably, step S3 includes to judge whether number of labels is 0, is to be back to step S0；Otherwise it enters step
S31,
The estimated channel coefficient matrix of configuration is P, and obtains the channel coefficient matrix of augmentation formStructure
Build the received signal vector of augmentation formThe augmentation cross-correlation covariance matrix for sending signal and receiving signal is calculated,
The augmentation auto-correlation covariance matrix of signal is received,
Calculate the power density E (v of white noise v (n)HV)=N0I,
Wherein I is unit matrix,
Preferably, in step S4, comprising to the augmentation auto-correlation covariance matrix C for receiving signal ss Invert, and by its
With the augmentation cross-correlation covariance matrix C for sending signal and reception signal as Multiplication obtains estimation coefficient；By the estimation coefficient with
The received signal vector of augmentation formsIt is multiplied, the label signal after being separated
Further, the label signal after separationFor augmentation form, its top half is takenFor final mark
Label separation signal.
It preferably, also include that demodulation module is adjusted based on label signal, the label signal after separation is demodulated into after S4
Binary data.
Scheme in compared with the existing technology, advantages of the present invention:
(1) the non-circular statistical property of second order in multi-label collision signal, while to the collision signal received and it is multiple
Conjugation carries out Combined Treatment, obtains additional performance boost；
(2) relative to traditional signal recovery method based on linear model, when number of labels increases, conflict can be utilized
Statistical redundancy in signal is to compensate the loss in efficiency due to caused by spatial redundancy reduction, and the advantage increases in number of labels
It is more obvious when big.
Detailed description of the invention
The invention will be further described with reference to the accompanying drawings and embodiments:
Fig. 1 is the block diagram based on ultrahigh frequency RFID label signal recovery system of the embodiment of the present invention；
Fig. 2 is the WLMMSE and linear least mean-square (LMMSE) of the embodiment of the present invention, and force zero (ZF) label collision signal is extensive
The bit error rate (BER) performance comparison of double calculation method in different signal-to-noise ratio (SNR) and different number of labels；
Fig. 3 is the goodput of two kinds of label collision signal recovery algorithms of WLMMSE and LMMSE of the embodiment of the present invention
Performance comparison；
Fig. 4 is RFID system of embodiment of the present invention figure.
Specific embodiment
Above scheme is described further below in conjunction with specific embodiment.It should be understood that these embodiments are for illustrating
The present invention and be not limited to limit the scope of the invention.Implementation condition used in the examples can be done according to the condition of specific producer
Further adjustment, the implementation condition being not specified is usually the condition in routine experiment.
Embodiment:
It is as shown in Figure 1 the block diagram based on ultrahigh frequency RFID label signal recovery system, it includes
Radiofrequency signal down conversion module, for the received radiofrequency signal of receiving antenna to be down-converted to base band；
Carrier cancellation module, the carrier signal issued for offsetting the transmission antenna for receiving and including in signal；
DC component cancellation module, the DC component in switch modulation signal (OOK) signal for removing label return,
It is converted into binary phase shift keying (BPSK) signal；
Number of labels estimation module is used for estimation label quantity；
Channel estimation module, for estimating channel coefficient matrix；
Label signal recovery module is based on wide linear MMSE criterion (WLMMSE) for the mark of conflict for utilizing
Label signal is separated.
Label signal adjust demodulation module, for by separation after label signal be demodulated into binary code stream (also referred to as two into
Data processed).
Next label signal restoration methods of the description based on the system, this method includes:
Step S0. obtains one of block of information of multi-tag signal response, as block of information to be separated, subsequently into step
Rapid S1；
The corresponding radiofrequency signal of the block of information is down-converted to base band by step S1. first, and enters step S2；
Step S2. digitizes the baseband signal, estimates and eliminates the carrier component in digital baseband signal, while removing letter
DC component in number, subsequently into step S3；
Step S3. estimation label quantity and channel coefficient matrix judge whether number of labels is 0, are then return steps
S0；Otherwise S31 is entered step；The estimated channel coefficient matrix of configuration is P, and obtains the channel coefficient matrix of augmentation form
The received signal vector of step S31. building augmentation formCalculate the augmentation for sending signal and receiving signal
Cross-correlation covariance matrix
Receive the augmentation auto-correlation covariance matrix of signal
Calculate the power density E (v of white noise v (n)HV)=N0I,
Wherein I is unit matrix,
Subsequently into step S4.
Step S4. is for the augmentation auto-correlation covariance matrix C for receiving signal ss Invert, and in turn with send signal
With the augmentation cross-correlation covariance matrix C for receiving signal as Multiplication obtains estimated coefficient；By the augmentation shape of coefficient and reception signal
FormulasIt is multiplied, the label signal after being separatedLabel signal after separationFor augmentation
Form takes its top halfSignal is separated for final label.
Demodulation module is adjusted based on label signal, the label signal after separation is demodulated into binary code stream.
Connect down through Fig. 2,3 come describe the application proposition embodiment and existing method comparison.Fig. 2's and Fig. 3
In simulated environment, the RFID system used meets 29768 standard of ISO 18000-6C agreement and GB/T, wherein receiving antenna
Quantity NtIt is 4, the channel between each label and card reader is assumed to be independent identically distributed quasistatic Rayleigh fading channel.
If Fig. 2 is the WLMMSE and LMMSE for showing the embodiment of the present invention, ZF label collision signal recovery algorithms are in difference
Signal-to-noise ratio (SNR) and different number of labels (NtIn the case of the bit error rate (SER) performance comparison as can be seen from Figure: this hair
The restoration methods (WLMMSE) of bright proposition have the lower bit error rate relative to LMMSE method and ZF method.Work as number of labels
NtWhen increasing to 4 from 2, performance advantage is become apparent.
If Fig. 3 is the reality for showing two kinds of label collision signal recovery algorithms of WLMMSE and LMMSE of the embodiment of the present invention
Border throughput performance comparison, as can be seen from Figure: restoration methods (WLMMSE) proposed by the present invention handling capacity achieved with
It can restore the increase of number of labels, and than traditional linear least mean-square (LMMSE) method closer to ideal throughput.
It is illustrated in figure 4 the RFID system figure of present example, includes 1 card reader and NtA label, wherein card reader
It is upper to be furnished with 1 transmitting antenna and NrRoot receiving antenna.
Ultrahigh frequency RFID label signal restoration methods in above embodiment are based on wide linear minimum mean-squared error
(WLMMSE) criterion.
The above embodiments merely illustrate the technical concept and features of the present invention, and its object is to allow person skilled in the art
It is to can understand the content of the present invention and implement it accordingly, it is not intended to limit the scope of the present invention.It is all according to the present invention
The equivalent transformation or modification that Spirit Essence is done, should be covered by the protection scope of the present invention.
Claims (6)
1. a kind of ultrahigh frequency RFID label signal restoration methods, comprising: down conversion module is used for the received radio frequency of receiving antenna
Signal is down-converted to base band；Carrier cancellation module, the carrier signal issued for offsetting the transmission antenna for receiving and including in signal；
DC component cancellation module, the DC component in switch modulation signal (OOK) signal for removing label return, is converted
For bpsk signal；Number of labels estimation module is used for estimation label quantity；Channel estimation module, for estimating channel coefficients square
Battle array；
Label signal separation module, for being divided the label signal of conflict using based on wide linear MMSE criterion
From；
Described method includes following steps:
Step S1. is based on down conversion module and received radiofrequency signal is down-converted to base band；
Step S2. eliminates the carrier component in digital baseband signal to the baseband signal after digitlization, using carrier cancellation module,
According to the DC component in DC component cancellation module removal signal；
Step S3. estimation label quantity and channel coefficient matrix；
Step S4. is based on label signal separation module and restores each RFID label tag signal.
2. according to the method described in claim 1, it is characterized by:
Also include S0 before the step S1, one of block of information of multi-tag signal response is obtained, as information to be separated
Block.
3. according to the method described in claim 1, it is characterized by:
The step S3 includes to judge whether number of labels is 0, is to be back to step S0；Otherwise S31 is entered step, institute is configured
The channel coefficient matrix of estimation is P, and obtains the channel coefficient matrix of augmentation formBuilding augmentation form connects
Receive signal vectorIt calculates
It sends signal and receives the augmentation cross-correlation covariance matrix of signal
Receive the augmentation auto-correlation covariance matrix of signal
Calculate the power density E (v of white noise v (n)HV)=N0I,
Wherein I is unit matrix,
4. according to the method described in claim 1, it is characterized by:
In the step S4, comprising to the augmentation auto-correlation covariance matrix C for receiving signal ss It inverts, and by itself and transmission
Signal and the augmentation cross-correlation covariance matrix C for receiving signal as Multiplication obtains estimation coefficient；
By the received signal vector of the estimation coefficient and augmentation formsIt is multiplied, the label signal after being separated
5. according to the method described in claim 4, it is characterized by:
Label signal after separationFor augmentation form, its top half is takenSignal is separated for final label.
6. according to the method described in claim 1, it is characterized by:
It also include that demodulation module is adjusted based on label signal, the label signal after separation is demodulated into two after the step S4
Binary data.
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| CN111641438A (en) * | 2020-04-27 | 2020-09-08 | 苏州大学 | System, method and processor readable medium for estimating number of RFID tags |
| CN113014358A (en) * | 2021-03-05 | 2021-06-22 | 苏州至善视界信息技术有限公司 | Self-adaptive decoding method and decoding system applied to backscattering system |
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