CN102682312A - Data encoding method for passive radio frequency identification from reader-writer to tag - Google Patents

Abstract

The invention discloses a data encoding method for passive radio frequency identification from a reader-writer to a tag. The method comprises the following steps of: grouping binary data to be sent according to two bits; and if the binary data to be sent is an odd bit, adding '0' into the binary data and then grouping. Compared with the existing methods, according to the method disclosed by the invention, under the condition that a data transmission speed is the same, the bandwidth occupied by a signal is narrower and the spectrum effectiveness is better; the unit bit can provide more energy for the tag and the problem of supplying passive tag energy can be better solved; and on the premise that the bandwidth occupied by the signal is the same, the data transmission speed can be effectively improved.

Description

Be used for the data-encoding scheme of the read write line of passive radio frequency identification to label

Technical field

The invention belongs to the RF identification communication technical field, be specifically related to a kind of data-encoding scheme of passive radio frequency identification system from the read write line to the label that be used for.

Background technology

The RF identification communication technology is a kind of non-contact automatic identification technology, and rfid system mainly is made up of label, read write line and computer network system.Read write line communicates through radiofrequency signal and label, obtains the identifying information of storing on the label, through computer network system the label information that reads is managed and information transmission simultaneously.

Rfid system can be divided into passive RFID system and active RFID system.In passive RFID system, read write line utilizes through coding and modulation radiofrequency signal transmission information later and gives label, to label energy is provided through radiofrequency signal on the one hand, through the backward scattered signal of label it is discerned on the other hand.Adopt half-duplex mode to communicate between read write line and the label.

For passive RFID system; The coding method of read write line end generally includes in the existing international standard: Manchester coding and PIE coding; For example: adopted the Manchester coding among the ISO 18000-6Type B, and all adopted the PIE coding among ISO 18000-6 Type A and the ISO 18000-6 Type C.

Manchester coding utilizes the variation of wave level to distinguish data: level is during by low uprising, representative data " 0 "; Level is during by high step-down, representative data " 1 "; And the saltus step of phase place occurs in the constantly middle of symbol period.Having carried abundant timing and synchronizing information in the Manchester coding, is a kind of motor synchronizing coding; The no dc shift of coding is realized simple simultaneously.Yet for passive RFID system, the subject matter that the Manchester coding brings is that the probability that high and low level occurs in the signal behind the coding is 50%, and the energy efficiency of supply of label is not high.Data " 0 " and " 1 " all are expressed as the low level form that connects regular length behind the high level of certain-length in the PIE coding; As shown in Figure 1; Through increasing the duration of high level in the data " 1 ", solved the under-supply problem of tab end energy in the Manchester coding effectively.Yet, owing to represent data " 1 ", cause the transmission time of unit bit elongated through introducing longer high level, under the constraint of same channel bandwidth, reduced the message transmission rate of read write line end.

Summary of the invention

Technical matters to be solved by this invention is to the prior art deficiency, a kind of data-encoding scheme that is used for the read write line of passive radio frequency identification to label to be provided, the problem of solution passive label energy supply, raising message transmission rate.

For solving the problems of the technologies described above, the technical scheme that the present invention adopted is: a kind of data-encoding scheme that is used for the read write line of passive radio frequency identification to label is provided, and this method step is:

Step 1, binary data to be sent is divided into groups by every dibit,, divide into groups again after then needing mend " 0 " it if binary data to be sent is an odd bits.

Step 2, to every group of data, encode as follows:

To data divide into groups " 00 ", use length as the high level of L1 after the spreading degree represent as the low level of L,

To data divide into groups " 01 ", use length as the high level of L2 after the spreading degree represent as the low level of L,

To data divide into groups " 11 ", use length as the high level of L3 after the spreading degree represent as the low level of L,

To data divide into groups " 10 ", use length as the high level of L4 after the spreading degree represent as the low level of L;

Wherein, L1＜L2＜L3＜L4.。

In sum; The read write line end adopts data-encoding scheme of the present invention to compare with adopting the PIE coding method in the passive radio frequency identification system: under the situation that message transmission rate equates; The bandwidth that signal takies is narrower; Spectrum efficiency is better, and the unit bit can provide more energy for label, has solved the problem of passive label energy supply better; Under the identical prerequisite of signal occupied bandwidth, can effectively improve message transmission rate, can provide and the suitable energy of PIE coding for label.

Description of drawings

Fig. 1 is the data symbol synoptic diagram of PIE coding embodiment;

Fig. 2 is for adopting the data symbol synoptic diagram of the embodiment of the invention;

Fig. 3 is for adopting the coding example schematic of the embodiment of the invention;

Fig. 4 is the power spectrum density comparison diagram of the employing embodiment of the invention with the coded signal that adopts PIE coding embodiment.

Embodiment

Below in conjunction with accompanying drawing specific embodiment of the present invention is described in detail.

Fig. 1 has provided the encode data symbol synoptic diagram of a specific embodiment of PIE.In Fig. 1, spreading was represented as the low level of 0.5Ts after data " 1 " used length as the high level of 1.5Ts; Spreading was represented as the low level of 0.5Ts after data " 0 " used length as the high level of 0.5Ts.Wherein, Ts is a unit reference time length, confirms according to the specific requirement of message transmission rate.

Fig. 2 is the data symbol synoptic diagram that adopts a specific embodiment of the present invention, in Fig. 2:

Binary data divide into groups " 00 " be encoded into: length is that the spreading degree is the low level of L=0.5Ts behind the high level of L1=0.5Ts;

Binary data divide into groups " 01 " be encoded into: length is that the spreading degree is the low level of L=0.5Ts behind the high level of L2=1.5Ts;

Binary data divide into groups " 11 " be encoded into: length is that the spreading degree is the low level of L=0.5Ts behind the high level of L3=2.5Ts;

Binary data divide into groups " 10 " be encoded into: length is that the spreading degree is the low level of L=0.5Ts behind the high level of L4=3.5Ts.

Suppose that read write line binary data to be sent is: " 0111001011000100110101 ".

At first data to be sent are divided into groups by every dibit; Be grouped into: " 01|11|00|10|11|00|01|00|11|01|01 "; Then above-mentioned digital coding is become: " +++-| ++ +++-|+-| ++ ++ +++-| ++ +++-|+-| +++-|+-| ++ +++-| +++-| +++-"; Wherein, "+" represents length is the lasting high level of 0.5Ts, and "-" represents length is the lasting low level of 0.5Ts.Fig. 3 representes the coding result of above-mentioned binary data to be sent.

Be object with specific embodiment shown in Figure 2 below, analyze the performance comparison that the bandwidth that message transmission rate equates and signal takies when read write line equates coding method of the present invention and PIE coding method under the both of these case.

(1) when message transmission rate equates

Suppose that the reference time Ts of unit among Fig. 1 does

The reference time Ts of unit does among Fig. 2

Suppose that simultaneously high and low level corresponding among two width of cloth figure all is respectively: V _HAnd V _LBoth message transmission rates are respectively R _PIE, R _APIE:

$R_{\mathrm{PIE}}=\frac{2}{{3T}_s^{\mathrm{PIE}}}$ $R_{\mathrm{APIE}}=\frac{4}{{5T}_s^{\mathrm{<figure-callout\; id="1"\; label="APIE"\; filenames="HDA0000067397820000011.png,HDA0000067397820000012.png"\; state="\{\{state\}\}">APIE</figure-callout>}}}$ ①

Work as R _APIE=R _PIEThe time, have: The energy that this moment, two kinds of coding method unit's bits offered label is respectively: E _PIEAnd E _APIE

$E_{\mathrm{PIE}}=E\left({\&Integral;}_0^{T_s}{v}^2\mathrm{dt}\right)=\frac{T_s^{\mathrm{PIE}}}{2}[2V_H^2+V_L^2]$ ②

$E_{\mathrm{APIE}}=E\left({\&Integral;}_0^{T_s}{v}^2\mathrm{dt}\right)=\frac{T_s^{\mathrm{APIE}}}{4}[4V_H^2+V_L^2]=\frac{3T_s^{\mathrm{PIE}}}{10}[4V_H^2+V_L^2]$ ③

Will be 3. subtract each other and obtain with 2. formula:

$\mathrm{\&Delta;E}=E_{\mathrm{APIE}}-E_{\mathrm{PIE}}=\frac{T_s^{\mathrm{PIE}}\&CenterDot;(V_H^2-V_L^2)}{5}>0$ ④

Can find out that from 4. formula the every bit of coding method that the present invention proposes can provide more energy for label, (this moment V when particularly depth of modulation is high more _H/ V _LBig more) advantage is obvious more.

When following surface analysis equates when message transmission rate, the situation of two kinds of coded signal occupied bandwidths, and then both spectrum efficiencies of comparison:

Fig. 4 is respectively the power spectrum density comparison diagram of coded signal of the specific embodiment of a specific embodiment of the present invention and PIE.The horizontal ordinate of Fig. 4 is represented digitization frequencies, and ordinate is represented power spectrum normalization amplitude.Curve 41 representes to carry out according to the present invention the power spectrum density of encoded signals, and curve 42 carries out the power spectrum density of encoded signals according to the PIE coding.Can find out that on scheming both bandwidth at first are 2/Ts at zero point, by the reference time Ts of the unit decision of coding.Both signal bandwidths are respectively B _PIE, B _APIE:

$B_{\mathrm{PIE}}=\frac{2}{T_s^{\mathrm{PIE}}}$ $B_{\mathrm{APIE}}=\frac{2}{T_s^{\mathrm{APIE}}}=\frac{5}{3T_s^{\mathrm{PIE}}}$ ⑤

Can find out by 5. formula: B _APIE＜B _PIE, the narrow bandwidth that the bandwidth ratio PIE coded signal that adopts coded signal of the present invention to take takies is described, spectrum efficiency is high.

When the bandwidth that (2) takies when coded signal equates

Can know according to top condition; When both bandwidth of coded signal equate, require

and this moment read write line message transmission rate be respectively:

$R_{\mathrm{PIE}}=\frac{1}{(1+2)T_s^{\mathrm{PIE}}/2}=\frac{2}{3T_s^{\mathrm{PIE}}}=\frac{2}{3T_s^{\mathrm{APIE}}}$ ⑥

$R_{\mathrm{APIE}}=\frac{2}{(1+2+3+4)T_s^{\mathrm{APIE}}/4}=\frac{4}{{5T}_s^{\mathrm{APIE}}}$

Can find out: R _APIE＞R _PIE, explain that the coding method that the present invention proposes can effectively improve the message transmission rate of read write line under the prerequisite of identical channel width constraint.

In addition, can know 2. with 3. that this moment, the unit bit was respectively to the energy that label provides according to formula:

$E_{\mathrm{PIE}}=\frac{T_s^{\mathrm{PIE}}}{2}[2V_H^2+V_L^2]$ $E_{\mathrm{APIE}}=\frac{T_s^{\mathrm{PIE}}}{4}[4V_H^2+V_L^2]$

Both are kept to mutually: $E_{\mathrm{APIE}}-E_{\mathrm{PIE}}=-\frac{V_L^2\&CenterDot;T_s^{\mathrm{PIE}}}{4}\&RightArrow;0$

Because low level V _LVery little, so following formula levels off to 0.Can find out that when the bandwidth that takies when both coded signals equated, every bit of coding method of the present invention can provide the energy suitable with the PIE method.

Claims (2)

1. a data-encoding scheme that is used for the read write line of passive radio frequency identification to label is characterized in that, steps of the method are:

Step 1 is divided into groups binary data to be sent by every dibit, if binary data to be sent is an odd bits, it is mended after " 0 " divide into groups;

Step 2, to every group of data, encode as follows:

1) to data divide into groups " 00 ", use length as the high level of L1 after the spreading degree represent as the low level of L;

2) to data divide into groups " 01 ", use length as the high level of L2 after the spreading degree represent as the low level of L;

3) to data divide into groups " 11 ", use length as the high level of L3 after the spreading degree represent as the low level of L;

4) to data divide into groups " 10 ", use length as the high level of L4 after the spreading degree represent as the low level of L.

2. the data-encoding scheme that is used for the read write line of passive radio frequency identification to label according to claim 1 is characterized in that, said coded system satisfies simultaneously: L1＜L2＜L3＜L4.

Images