KR20110100182A - Phy layer of low frequency band based on wireless magnetic field communication - Google Patents

Abstract

The present invention provides a suitable packet format, coding, and modulation scheme between a master and a slave to perform wireless communication in a magnetic field-based low frequency band wireless communication applied to a difficult environment at a variable data rate or coding method according to the surrounding environment. The present invention relates to a physical layer configuration method of a low frequency band wireless communication based on a supported magnetic field, and a computer readable recording medium having recorded thereon a program for executing the method.
The present invention relates to a physical layer configuration method of a low frequency band wireless communication based on a magnetic field, wherein a data rate and a coding scheme of a payload field included in a request frame and a response frame between a master and a slave are determined in a peripheral communication environment within a predetermined range. It can be changed according to the features.
In the above configuration, the request frame and the response frame may be formed in the same format. The request frame and the response frame may each include a preamble field, a header field, and a payload field.

Description

Method for configuring physical layer of low frequency band wireless communication based on magnetic field, and computer readable recording medium recording program for executing the method {PHY layer of low frequency band based on wireless magnetic field communication}

The present invention relates to a physical layer configuration method of a low frequency band wireless communication based on a magnetic field and a computer readable recording medium having recorded thereon a program for executing the method. In particular, the present invention relates to a low frequency band wireless communication based on a magnetic field applied to a difficult environment. The present invention relates to a physical layer construction method of magnetic field-based low frequency band wireless communication, and a program for executing the method, which can be efficiently supported, and to a computer readable recording medium.

As is well known, RFID (Radio Frequency IDentification) is a ubiquitous system that can input identification information into a tag, which is a small semiconductor, and read, track, and manage an object, animal, or person with such a tag using radio frequency. It is one of the computing infrastructure technologies. This RFID technology can be active, passive, or semi-active, depending on whether the tag is powered by its own power source or derives energy from radio waves received from an interrogator. Can be classified. Also, depending on the application or recognition distance, low frequency (LF) in the band of 135 ㎑ or less, high frequency in the 13.56 MHz band, high frequency in the 433.92 MHz or 860 to 960 MHz band, and radio frequency in the 2.45 ㎓ band use. Among them, RFID technology using low frequency (LF) of band of 135㎑ or less is strong in the influence of the surrounding environment because it operates on the basis of magnetic field, and accordingly underground works such as oil pipelines and water / sewage pipes covered with soil or concrete Alternatively, it can be effectively used to recognize objects in various difficult environments such as water, metal or disaster environment. The physical layer (PHY layer), that is, the air interface standard, is referred to as ISO / IEC 18000-2 (hereinafter referred to as 'prior art'). ) Is defined in detail.

1 is a frame configuration of a general request format from the master to the slave in the air interface method of the conventional low frequency band wireless communication, Figure 2 is a frame of the general response format from a slave to master in the air interface method of a conventional low frequency band wireless communication It is a block diagram. According to the air interface method of the conventional low frequency band wireless communication, the packet format, the coding (coding) method, and the data rate of the master and the slave do not all match, and a passive tag is used.

First of all, the general request format of FIG. 1 is used to send a command to a tag in which a master, for example, an RFID pager is a slave. In this case, PIE (Pulse Interval Encoding) is used. The data rate is about 5.1 kbps. On the other hand, when the slave sends a response to the command of FIG. 1, the general response format as shown in FIG. 2 is used. In addition, when a response to the inventory command is transmitted by dividing the pager command into an inventory command and an international standard command, a dual pattern data coding method using 2kbps is used. When sending a response to an international standard command, the Manchester coding method is used at 4kbps.

Moreover, the prior art defines two types of tags: type A (FDX) and type B (HDX), which are permanently powered by the pager as well as during the tag-call period transmission. The type tag is powered by the pager at all times except during the tag-call period. In the case of type A, Manchester coding and ASK (Amplitude Shift Keying) are used. In case of Type B, Non-Return-to-Zero (NRZ) coding and Frequency Shift Keying (FSK) modulation are used.

As described above, according to the related art, since the data rate between the master and the slave is fixed to a single value, and the data coding and modulation schemes are also fixed without a choice, the present invention actively adapts to the surrounding communication environment to perform efficient communication. There was a problem that can not be.

Furthermore, according to the prior art, since the slave, for example tag, is defined as passive, not only is there a limitation in the length of the response frame, but also active communication with the master, for example, a pager, is not possible. There were problems with many restrictions.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. In the low frequency band wireless communication based on the magnetic field, wireless communication can be performed at a variable data rate or coding method according to the surrounding environment. It is an object of the present invention to provide a computer-readable recording medium in which a physical layer configuration method of a magnetic field-based low frequency band wireless communication supporting a suitable packet format, coding and modulation scheme, and a program for executing the method are recorded.

In order to achieve the above object, the present invention provides a method for configuring a physical layer in a low frequency band wireless communication based on a magnetic field, wherein a data rate and a coding scheme of a payload field included in a request frame and a response frame between a master and a slave are determined in advance. It can be changed according to the surrounding communication environment within the range.

In the above configuration, the request frame and the response frame may be formed in the same format. The request frame and the response frame may each include a preamble field, a header field, and a payload field.

On the other hand, the preamble field may be composed of a sequence that is alternatively designated by the user and a predetermined fixed sequence among two or more sequences each having a predetermined number of bits, the preamble field is Manchester coding at a data rate of 1kbps Can be modulated BPSK.

The header field may include an area indicating a data rate and coding information of the payload field, an area indicating a data length of the payload field, and a header check sequence. The header field may have a data rate of 1 kbps. BPSK can be modulated after being Manchester coded.

Meanwhile, the payload field may include a data region of 0-255 bytes and a frame check sequence of 2 bytes. The payload field may be Manchester coding or 2, 4 or 1, 2 or 4 kbps data rate. BPSK can be modulated after being selectively coded among NRZ-L coding at a data rate of 8 kbps.

Moreover, the NRZ-L coded output may be modulated in the BPSK after being scrambled.

According to the magnetic layer-based low frequency band wireless communication physical layer configuration method and a computer-readable recording medium recording a program for executing the method, the surrounding environment in a magnetic field-based low frequency band wireless communication applied to difficult environments According to the present invention, it is possible to improve communication performance and efficiency by supporting an appropriate packet format, coding, and modulation method between a master and a slave so that wireless communication can be performed at a variable data rate or coding method.

1 is a frame configuration diagram of a general request format from a master to a slave in a physical layer configuration method of a conventional magnetic field based low frequency band wireless communication;
2 is a frame configuration diagram of a general response format from slave to master in a physical layer configuration method of a conventional magnetic field based low frequency band wireless communication;
3 is a frame configuration diagram of a bidirectional communication format between a master and a slave in a method for configuring a physical layer in a low frequency band wireless communication based on a magnetic field of the present invention;
4 is a frame configuration diagram of a preamble field in FIG. 3;
5 is a frame configuration diagram of a payload field in FIG. 3;
6 is a view for explaining Manchester coding and NRZ-l coding schemes applicable to the method of the present invention;
7 is a block diagram of a scrambler that can be applied to the present invention;
8 is a diagram illustrating a coding and modulation process of a preamble in the method of the present invention;
9 is a view for explaining a coding and modulation process of a header in the method of the present invention;
10 is a diagram illustrating a coding and modulation process of payload data in the method of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the physical layer configuration method of the magnetic field-based low-frequency band wireless communication of the present invention.

3 is a frame configuration diagram of a bidirectional communication format between a master and a slave in the method for configuring a physical layer of low frequency band wireless communication based on the present invention, FIG. 4 is a frame configuration diagram of a preamble field in FIG. 3 is a frame configuration diagram of a payload field. First, as shown in Figure 3, according to the physical layer configuration method of the magnetic field-based low frequency band wireless communication of the present invention, it is preferable to configure the bidirectional communication frame between the master and the slave bar, from the master to the slave Because of the length of the communication frame, it is desirable to implement a slave, for example, a tag, which is active by its own power supply. Of course, the slave may be implemented in a passive type or semi-active type in which a variable or passive type variable operation is performed depending on the length of data.

Referring back to FIG. 3, the communication frame may be composed of a preamble, a header, and a payload field in order, where the preamble field is a frame start of a conventional general request format or a general response format. It performs the same function as the Of Frame (SOF) field. This preamble field is again in order from the least significant bit (LSB) to the most significant bit (MSB), for example a length of 0, 4, 8 or 12 bits specified by the user. It may consist of a sequence of 0 ', a' 0000 'sequence of 4 bits, and a' 1010 'sequence of 4 bits. As a result, when the user-specified sequence is 0 bit, the user-specified sequence does not exist, and the preamble will be composed of a 4-bit '0000' sequence and a 4-bit 1010 sequence.

Next, as shown in FIG. 3, the header field may be composed of a total of 3 bytes. In the order of least significant bit to most significant bit, for example, 3 bits of data rate and coding information area, for example, 8 bits The payload data length region, for example, a 5-bit reserved region and an 8-bit header check sequence (HCS) may be included. The payload data length region of 8 bits in this header field indicates the length of data included in the payload in bytes. The header check sequence may consist of, for example, an 8-bit Cyclic Reduncy Check (CRC).

Finally, the payload field may consist of a data area of up to 255 bytes and a frame check sequence of 2 bytes to protect the data area. For example, when the length of data is 0, the frame check sequence is not included. The data rate and coding method for the preamble field, header field, and payload field are expressed in 3 bits to support a total of eight methods as shown in Table 1 below.

Data rate and coding Data rate Coding method b2b1b0 = 000 (type 0) 1 kbits / s Manchester b2b1b0 = 001 (type 1) 2 kbits / s Manchester b2b1b0 = 010 (type 2) 4 kbits / s Manchester b2b1b0 = 011 (type 3) 2 kbits / s NRZ-L + scrambling b2b1b0 = 100 (type 4) 4 kbits / s NRZ-L + scrambling b2b1b0 = 101 (type 5) 8 kbits / s NRZ-L + scrambling b2b1b0 = 110 (type 6) Reserved - b2b1b0 = 111 (type 7) Reserved -

As described in Table 1 above, one of a Manchester coding scheme and a NonReturn-to-Zero Level (NRZ-L) coding scheme may be selected as a coding scheme according to the method of the present invention.

6 is a diagram for explaining Manchester coding and NRZ-l coding schemes applicable to the method of the present invention. As shown in FIG. 6, in the Manchester coding scheme, the signal level changes in the middle of the bit interval. When the data bit is '0', the data bit changes from level '1' to level '0' while the data bit is '1'. ', It changes from level' 0 'to level' 1 '. The NRZ-L coding scheme matches level '0' when the data bit is '0' and level '1' when the data bit is '1'. As a result, the Manchester coding scheme is advantageous because it has less DC components than the NRZ-L coding scheme, but is disadvantageous in that it uses twice the frequency band. Therefore, when the communication environment is relatively good, the NRZ-L coding scheme is used, while in other cases, the Manchester coding scheme can be flexibly changed and used.

7 is a block diagram of a scrambler that can be applied to the present invention. On the other hand, as described above, the NRZ-L coding scheme has a lot of DC disadvantages compared to the Manchester coding scheme. To overcome this, the NRZ-L coding result is treated with a scrambler as shown in FIG. 7. It is preferable to suppress the DC component.

In this case, the scrambler is input to prevent loss of timing information among consecutive input data and to suppress cross-modulation in a transmission path by suppressing a single frequency component generated by repeating a periodic data pattern. Since it is a well-known circuit for converting data into a random code sequence, the receiving side, i.e., the master or the slave, can reproduce the original data signal by a descrambler having the opposite calculation function.

8 is a diagram illustrating a coding and modulation process of a preamble in the method of the present invention, FIG. 9 is a diagram illustrating a coding and modulation process of a header in the method of the present invention, and FIG. 10 is a diagram of a method of the present invention. A diagram for describing a coding and modulation process of payload data.

First, as shown in FIG. 8, in the method of coding and modulating a preamble field in the method of the present invention, the generated preamble sequence is encoded by using a Manchester coding scheme having a data rate of type 0 of Table 1, that is, 1 kbps. After that, BPSK modulation is performed again. Similarly, the coding and modulation process for the header field is also coded by using a Manchester coding scheme having a data rate of type 0, that is, 1 kbps in Table 1, after adding a header check sequence to protect the header field. Later on, BPSK modulation will occur again.

On the other hand, in the case of the payload field, the payload check sequence is added to the upper end of the data to protect it, and the encoding is performed by selecting an appropriate data rate and coding method among types 0 to 7 in Table 1 above. The encoded result is BPSK modulated again.

As described above, in the method of the present invention, the preamble field and the header field are encoded to have a low data rate using a Manchester coding scheme that is relatively stable to intermodulation interference regardless of the surrounding communication environment, while the payload field is appropriate to the communication environment. By using the data rate and coding method, and further, by using BPSK (Binary Phase Shift Keying) modulation method, not only can the communication performance be improved, but also it can adapt adaptively to the surrounding communication environment.

In the physical layer configuration method of the low frequency band wireless communication based on the present invention, since the slave, for example, the tag may be actively configured, the tag may give a command to the pager. Coding schemes may also be actively performed on both master and slave.

The physical layer configuration method of the magnetic field-based low frequency band wireless communication and the computer-readable recording medium in which the program for executing the method are recorded are not limited to the above-described embodiments, but the scope of the technical idea of the present invention allows. Various modifications can be made within the apparatus.

Claims (11)

In the physical layer configuration method of the low frequency band wireless communication based on the magnetic field,
Physical field of the low frequency band wireless communication based on the magnetic field, characterized in that the data rate and coding method of the payload field included in the request frame and the response frame between the master and the slave can be changed according to the surrounding communication environment within a predetermined range. How to organize tiers. The method of claim 1,
The request frame and the response frame are physical layer configuration method of the magnetic field-based low frequency band wireless communication, characterized in that the same format. The method of claim 2,
The request frame and the response frame each include a preamble field, a header field, and
A method for configuring a physical layer in a low frequency band wireless communication based on a magnetic field, comprising a payload field. The method of claim 3, wherein
The preamble field is a physical layer configuration method of a magnetic field-based low frequency band wireless communication, characterized in that the sequence consisting of a predetermined sequence and a predetermined sequence of two or more among the sequence of two or more each having a predetermined number of bits. The method of claim 4, wherein
The preamble field is BPSK modulated after being Manchester coded at a data rate of 1 kbps. The method of claim 5, wherein
The header field includes a region indicating a data rate and coding information of the payload field, a region indicating a data length of the payload field, and a header check sequence. Configuration method. The method according to claim 6,
The header field is BPSK modulated after Manchester coded at a data rate of 1 kbps. The method of claim 7, wherein
The payload field comprises a data region of 0-255 bytes and a frame check sequence of 2 bytes. The method of claim 8,
The payload field is BPSK modulated after being selectively coded among Manchester coding at a data rate of 1, 2 or 4 kbps or NRZ-L coding at a data rate of 2, 4 or 8 kbps. Method of configuring physical layer of wireless communication. The method of claim 9,
And the NRZ-L coded product is scrambled and then BPSK modulated. A computer-readable recording medium having recorded thereon a program for executing a method for constructing a physical layer of the magnetic field-based low frequency band wireless communication according to any one of claims 1 to 10.

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