CN104361370A - Method for judging FM0 coding frame header of ultrahigh frequency RFID (radio frequency identification) reader - Google Patents

Abstract

The invention relates to the technical field of wireless signal processing, in particular to a method for judging an FM0 coding frame header of an ultrahigh frequency RFID (radio frequency identification) reader. The method includes that a main judgment identification V of the frame header is captured by the aid of rules about frame header signals in an EPC (electronic product code) protocol, fault tolerance of code elements at the reception starting section is improved, sensibility in error code judgment is restored after reception is stabilized, efficiency of correct judgment of the frame header is improved, and invalid signals can be assuredly timely discovered to stop communication. The main judgment identifier of the frame header V is captured, the fault tolerance of the code elements at the reception starting section is improved, the sensibility in error code judgment is restored after reception is stabilized, judgment of the symbol 'V' is strengthened, judgment of a lead code and a pilot tone is loose at the beginning and tense in the end, the problem that FM0 receiving signals are misjudged to be invalid communication due to start portion deviation caused by interference is solved, the truly-invalid signals can be assured to be detected out and waste of too much communication time due to the invalid signals is avoided.

Description

A kind of method of discrimination of ultrahigh frequency radio frequency identification (RFID) reader FM0 coding frame head

[technical field]

The present invention relates to wireless signal processing technology field, specifically a kind of method of discrimination of ultrahigh frequency radio frequency identification (RFID) reader FM0 coding frame head.

[background technology]

RFID (radio frequency identification) technology refer to by identify with exchanges data for the purpose of, utilize induction, automatic identification technology that radiowave or microwave carry out noncontact two-way communication, utilize this technology can realize tracking to all physical objecies and management.2006 EPC global (Universal Product electronic code administrative center) include ISO/IEC 18000-6C standard in, in November, 2013, have approved new standard EPC Gen2V2.0, for the RFID technique specification of the UHF of about 900MHz, now by China as the 1st class 2nd generation UHF RFID 860MHz-960MHz communication protocol.Uhf band rfid system has the features such as read or write speed is fast, memory capacity is large, decipherment distance is far away, cost is low, size is little, is more suitable for the application in following logistics, supply chain field, also provides possibility for realizing " Internet of Things ".Therefore the development of ultrahigh frequency RFID system is the emphasis of current rfid system development.Here proposed ultrahigh frequency radio frequency identification (RFID) reader realizes based on EPC Gen2 standard, read write line to the read-write of label by sending radio-frequency (RF) energy and realizing echo detecting, the data return times of label is paroxysmal, a frame head is had to carry out the beginning of identification data before actual data, to the quality that frame head differentiates, sensitivity and the throughput of read write line directly can be had influence on.

According to EPC Gen2 agreement regulation, receiving the data of cutting the throat from label is FM0 coded format, starts with frame head, and frame head is made up of 2 parts: front 12 zero pilot tones formed and 6 certain bits afterwards.Pilot tone forms by 12 zero, the actual frequency of its object mainly in order to allow read write line calculate label return data.Pilot tone can be arranged by read write line and select or do not select.That is, frame head can directly by 6 certain bits, and 6 certain bits are made up of 4 bit data+V+ " 1 ", and wherein, 4 bit data are " 1010 ".V represents and there occurs skew (namely inversion of phases should occur but in fact not have), according to FM0 coding rule, each code element needs upset once when starting, so according to this rule, after 4 bit data " 1010 ", no matter what rear data are, the position of V just should be turned into high level, but not upset herein, Here it is for distinguishing the important symbol of frame head and data, after V, can add the end of 1 redundancy " 1 " as frame head, after this " 1 ", it has been exactly formal numeric data code.

The differentiation flow process of existing frame head has first judged whether pilot tone, first receive the pilot tone of 12 " 0 " if any, then the lead code of " 1010 " is received, then detect the existence whether " 1010 " have " V " below, after " V " being detected, then receive " 1 " of a redundancy, frame head has just received, what start below has been exactly Frame, if frame head is not containing pilot tone, then frame head receives directly from the differentiation of lead code.

But the header signal that the read write line of reality receives, because returning of label is paroxysmal, add the existence of space interference, the signal often received, and it is imperfect, the part particularly started, such frame head part is likely incomplete signal, but once frame header divide receive stable after, data are below often relatively stable, often enter and receive error condition and waste a call duration time, cause the decline of read write line read rate, the pilot tone of 12 should be had to only have now 6, and the start-up portion of " 0 " that receives is not complete, this is in original testing process, all will be considered to the signal of mistake and be grouped into inside error handle go.Situation not with pilot tone, first code element " 1 " of the start-up portion lead code of signal, start at center section, this can be misunderstood into " 0 " in original decoding, such lead code receives will mistake, although the code element of receipt of subsequent is correct, " V " mark is also normal, but because lead code is incorrect, according to original preamble detecting flow process, this situation also can be classified as garbled-reception, so needs one can be fault-tolerant relatively good to frame head start-up portion, after frame head reception is stable, again can to a testing process of the timely error detection of follow-up signal.

[summary of the invention]

Because returning of label is sudden and the existence of space interference when the object of the invention is to solve header signal that traditional read write line receives, make the imperfect technical matters causing frame header sub-signal incompleteness of signal received, design one enhances differentiation to " V " symbol, guarantee to detect that the ultrahigh frequency radio frequency identification (RFID) reader FM0 of real invalid signals encodes the method for discrimination of frame head.

To achieve these goals, design the method for discrimination of a kind of ultrahigh frequency radio frequency identification (RFID) reader FM0 coding frame head, the method utilizes the regulation about header signal in EPC agreement, catch the main discrimination flag V of frame head, improve code element in the fault-tolerance receiving the initial segment, receiving the stable rear sensitivity recovering errorcode decision, thus both improve the efficiency of frame head correct decision, can ensure that again invalid signals is found in time and stops communication;

For the frame head of band pilot tone, 0 initial as pilot tone by 12, method of discrimination is as follows: the problem of the number that have ignored 12 0, and in the incipient stage, allow the existence of error code, after being determined as error code more than three times, just think that this time communication makes mistakes, but when be correctly decoded 0 more than three times after, we just think that the non-steady state of reference position terminates, wait for the arrival of lead code 1010 and frame head identifier V below according to stable accepting state, if there is error code here, then this time communication of thinking is really invalid signals;

For the frame head not with pilot tone, initial have 4 1010 lead code beginnings of encoding, method of discrimination is as follows: allow at reception initial period, lead code is not carried out to the judgement of sequence of symhols, only after makeing mistakes more than 3 symbol decodings, just can think that this communication is invalid, as long as there is symbol decoding success just to enter in the wait of frame head identifier V, as long as there is V to produce, then thinks that frame head receives successfully and enter data receiver.

The present invention utilizes the regulation about header signal in EPC agreement, catch the main discrimination flag V of frame head, improve code element in the fault-tolerance receiving the initial segment, receiving the stable rear sensitivity recovering errorcode decision, enhance the differentiation to " V " symbol, loose at first but afterwards tight differentiation is carried out to the differentiation of lead code and pilot tone, solve FM0 Received signal strength is mistaken for invalid communication problem because interference causes start-up portion deviation, also can guarantee that real invalid signals also can be detected simultaneously, too much call duration time can not be wasted because of invalid signals.

[accompanying drawing explanation]

Fig. 1 is that frame head of the present invention differentiates process flow diagram;

Fig. 2 is FM0 coded frame header structure schematic diagram;

Fig. 3 is existing preamble detecting process flow diagram;

Fig. 4 is the actual map signal of band pilot tone;

Fig. 5 is the actual map signal not with pilot tone;

Specify Fig. 1 as Figure of abstract of the present invention.

[embodiment]

Below in conjunction with accompanying drawing, the invention will be further described, and the structure of this device and principle are very clearly concerning the people of this specialty.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.

The differentiation flow process of existing frame head as shown in Figure 3, first pilot tone has been judged whether, first receive the pilot tone of 12 " 0 " if any, then receive the lead code of " 1010 ", then detect the existence whether " 1010 " have " V " below, after " V " being detected, receive " 1 " of a redundancy, frame head has just received again, and what start below has been exactly Frame, if frame head is not containing pilot tone, then frame head receives directly from the differentiation of lead code.

The present invention is the method for discrimination of a kind of ultrahigh frequency radio frequency identification (RFID) reader FM0 coding frame head, it judges that flow process as shown in Figure 1, about the regulation of header signal in the method flexible utilization EPC agreement, catch the main discrimination flag of frame head " V ", improve code element in the fault-tolerance receiving the initial segment, receiving the stable rear sensitivity recovering errorcode decision, thus both improve the efficiency of frame head correct decision, can ensure that again invalid signals is found in time and stops communication.

As shown in Figure 1, in this flow process still in two kinds of situation, a kind of is band pilot tone, a kind of for not to be with pilot tone, for the frame head of band pilot tone, as shown in Figure 4, it is initial as pilot tone by 12 " 0 ", but under the reception situation of reality, due to the existence of various interference, the start-up portion of very possible 12 " 0 " does not receive or error code.If this is sentenced mistake, so just waste the chance once communicated.So in the present invention, have ignored the problem of the number of 12 " 0 ", and in the incipient stage, allow the existence of error code, after being determined as error code more than three times, just think that this time communication makes mistakes, but when be correctly decoded " 0 " more than three times after, just think that the non-steady state of reference position terminates, after to wait for the arrival of lead code " 1010 " and frame head identifier " V " according to stable accepting state, if there is error code here, then this time communication of thinking is really invalid signals.For the frame head not with pilot tone, as shown in Figure 5, it is initial 4 coding " 1010 " lead codes beginnings, same reason, and at initial period, lead code perhaps can error code or at all cannot decode.So in the present invention, same permission, at reception initial period, does not carry out the judgement of sequence of symhols to lead code, only after makeing mistakes more than 3 symbol decodings, just can think that this communication is invalid.As long as there is symbol decoding success just to enter in the wait of frame head identifier " V ", as long as there be " V " to produce, then think that frame head receives successfully and enter data receiver.

By to the deep interpretation of agreement, can learn, the frame head part of FM0 coding of its regulation, lead code is exactly that pilot tone is especially in order to strengthen this function further in order to allow the speed of receiving end determination code element and form.And " V " symbol, be only real for identifying the diagnostic criterium of frame head, so invention enhances the differentiation to " V " symbol, loose at first but afterwards tight differentiation is carried out to the differentiation of lead code and pilot tone, solves FM0 Received signal strength is mistaken for invalid communication problem because interference causes start-up portion deviation like this.Also can guarantee that real invalid signals also can be detected simultaneously, too much call duration time can not be wasted because of invalid signals.

Claims (1)

1. the method for discrimination of a ultrahigh frequency radio frequency identification (RFID) reader FM0 coding frame head, it is characterized in that the method utilizes the regulation about header signal in EPC agreement, catch the main discrimination flag V of frame head, improve code element in the fault-tolerance receiving the initial segment, receiving the stable rear sensitivity recovering errorcode decision, thus both improve the efficiency of frame head correct decision, can ensure that again invalid signals is found in time and stops communication;

For the frame head of band pilot tone, 0 initial as pilot tone by 12, method of discrimination is as follows: the problem of the number that have ignored 12 0, and in the incipient stage, allow the existence of error code, after being determined as error code more than three times, just think that this time communication makes mistakes, but when be correctly decoded 0 more than three times after, we just think that the non-steady state of reference position terminates, wait for the arrival of lead code 1010 and frame head identifier V below according to stable accepting state, if there is error code here, then this time communication of thinking is really invalid signals;

For the frame head not with pilot tone, initial have 4 1010 lead code beginnings of encoding, method of discrimination is as follows: allow at reception initial period, lead code is not carried out to the judgement of sequence of symhols, only after makeing mistakes more than 3 symbol decodings, just can think that this communication is invalid, as long as there is symbol decoding success just to enter in the wait of frame head identifier V, as long as there is V to produce, then thinks that frame head receives successfully and enter data receiver.