JP2011234190A - Method of configuring physical layer in magnetic field based low frequency band radio communication and computer readable recording medium with program for executing the method recorded thereon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide magnetic field based low frequency band radio communication for supporting a packet format, coding and modulation systems suitable between a master and a slave so as to carry out radio communication with a data rate or coding system variable according to peripheral environments in the magnetic field based low frequency band radio communication applied to adverse environments.SOLUTION: In a method of configuring a physical layer in magnetic field based low frequency band radio communication, a data rate and a coding system of a payload field contained in a request frame and a response frame between a master and a frame is made variable in accordance with a peripheral communication environment within a predetermined range. In such a configuration, the request frame and the response frame may be comprised of the same format but such request frame and response frame may include a preamble field, a header field and a payload field, respectively.

Description

  The present invention relates to a method for configuring a physical layer in a wireless communication based on a magnetic field and a computer-readable recording medium on which a program for executing the method is recorded, and more particularly to a magnetic field-based low-frequency recording medium applied to a bad environment. The present invention relates to a method for configuring a physical layer in magnetic field-based low-frequency band wireless communication that can efficiently support frequency-band wireless communication, and a computer-readable recording medium on which a program for executing this method is recorded.

  As is well known, RFID (Radio Frequency IDentification) embeds identification information in a tag, which is an ultra-small semiconductor, and uses radio frequency to read, track and track objects, animals or people with such tags attached. It is one of the ubiquitous computing infrastructure technologies that can be managed. Such RFID technology is active (active), passive (semi-active) or semi-active depending on whether the tag operates with its own power supply or operates by obtaining energy from radio waves received by an interrogator. It is classified as active type (Semi-Active). Depending on the application field and recognition distance, low frequency (LF) in the band of 135 kHz or less, high frequency (HF) in the 13.56 MHz band, ultra high frequency (UHF) in the 433.92 MHz or 860 to 960 MHz band, and microwave in the 2.45 GHz band. Use the radio frequency. Among these, the RFID technology using a low frequency (LF) in a band of 135 kHz or less operates on a magnetic field base and is resistant to the influence of the surrounding environment. As a result, oil pipes covered with soil, concrete, etc. The physical layer (PHY layer), which can be used effectively to recognize objects in underground environments such as sewer pipes or various adverse environments such as water, metals and disaster-prone environments That is, the air interface standard is defined in detail in ISO / IEC 18000-2 (hereinafter referred to as “prior art”).

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

  First, when an instruction word is sent to a slave tag by a master, for example, an RFID interrogator, the general request format shown in FIG. 1 is used. As a data coding method at this time, PIE (Pulse Interval Encoding) is used. The average data rate is about 5.1 kbps. On the other hand, when the slave sends a response to the command word of FIG. 1, a general response format is used as shown in FIG. Also, the command word of the caller is divided into an inventory command and an international standard command, and when a response to the inventory command is sent, a double pattern data coding (dual While using the pattern data coding scheme, the Manchester coding scheme is used at 4 kbps when sending responses to other international standard commands.

  Furthermore, the prior art defines two types of tags, such as A type (FDX) and B type (HDX), but the A type tag is permanently set by the interrogator, including during transmission between the tag and interrogator. Whereas the power is supplied, the B type tag is supplied by the interrogator at other times except during transmission between the tag and the interrogator. While the Manchester coding method and the ASK (Amplitude Shift Keying) method are used, in the case of the B type, the NRZ (Non Return-to-Zero) coding method and the FSK (Frequency Shift Keying) modulation method are used.

  As described above, according to the prior art, the data rate between the master and the slave is fixed at a single value, and the data coding and modulation method are also fixed without any choice. Therefore, there is a problem that it is impossible to carry out efficient communication by actively adapting to.

  Furthermore, according to the prior art, since the slave, for example, the tag is defined as passive, not only the length of the response frame is limited, but also active communication to the master, for example, the interrogator is impossible. Therefore, there are problems that impose many restrictions on the application field.

  The present invention has been devised to solve the above-described problems, and in a magnetic field-based low frequency band wireless communication applied to a bad environment, a variable data rate and coding method depending on the surrounding environment. Method for configuring physical layer in magnetic field-based low-frequency wireless communication and supporting program for supporting suitable packet format, coding and modulation scheme between master and slave so that wireless communication can be performed in Is to record a computer-readable recording medium.

  To achieve the above object, the present invention provides a data rate of a payload field included in a request frame and a response frame between a master and a slave in a physical layer configuration method in magnetic field-based low frequency band wireless communication. The coding method can be changed in accordance with the surrounding communication environment within a predetermined range.

  In the above configuration, the request frame and the response frame may have the same format, but the request frame and the response frame may each include a preamble field, a header field, and a payload field. it can. Meanwhile, the preamble field may be composed of a fixed sequence of 16 bits, and the preamble field may be BPSK modulated after being Manchester coded at a data rate of 1 kbps.

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

  Meanwhile, the payload field may include a 0-255 byte data area and a 2-byte frame check sequence, but the payload field may be Manchester coding with a data rate of 1, 2, or 4 kbps, or 2, 4, or After selective coding of NRZ-L coding with a data rate of 8 kbps, BPSK modulation may be performed.

  Further, the NRZ-L coded result may be scrambled and then BPSK modulated.

  According to the magnetic layer-based low frequency wireless communication method of the present invention and the computer-readable recording medium on which the program for executing the method is recorded and read by a computer, the magnetic field-based Supports suitable packet formats, coding and modulation methods, etc. between master and slave so that wireless communication can be performed with variable data rate and coding method depending on the surrounding environment in frequency band wireless communication By doing so, communication performance and efficiency can be improved.

FIG. 10 is a frame configuration diagram of a general request format from a master to a slave in a conventional configuration method of a physical layer in a magnetic field-based low frequency band wireless communication. FIG. 6 is a frame configuration diagram of a general response format from a slave to a master in a conventional configuration method of a physical layer in low-frequency wireless communication based on a magnetic field. FIG. 2 is a frame configuration diagram of a bidirectional communication format between a master and a slave in the physical layer configuration method in the magnetic field-based low frequency band wireless communication of the present invention. FIG. 4 is a frame configuration diagram of a preamble field of FIG. 3. FIG. 4 is a frame configuration diagram of a payload field in FIG. 3. It is a figure for demonstrating the Manchester coding and NRZ-L coding system which can be applied to the method of this invention. It is a block block diagram of a scrambler that can be applied to the present invention. FIG. 5 is a diagram illustrating a preamble coding and modulation process in the method of the present invention. FIG. 6 is a diagram illustrating a header coding and modulation process in the method of the present invention. FIG. 4 is a diagram illustrating a process for coding and modulating payload data in the method of the present invention.

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

  FIG. 3 is a frame configuration diagram of a bidirectional communication format between a master and a slave in the physical layer configuration method in the magnetic field-based low frequency band wireless communication of the present invention, and FIG. 4 is a preamble field frame of FIG. FIG. 5 is a block diagram of the payload field in FIG. 3. First, as shown in FIG. 3, according to the physical layer configuration method in the magnetic field-based low frequency band wireless communication of the present invention, the bidirectional communication frame between the master and the slave can be configured in the same format. Desirably, since the length of the communication frame from the master to the slave is long, it is desirable to implement the slave, for example, the tag, in an active type that operates by itself. Of course, the slave can also be embodied as a passive type or a semi-active type that variably operates in a passive type or an active type depending on the data length.

  In FIG. 3, the communication frame can be roughly composed of a preamble, a header, and a payload field, where the preamble field is a frame in a conventional general request format or general response format. It performs the same function as the Start (SOF) field. Such a preamble field is further composed of the least significant bit (LSB) to the most significant bit (MSB). The preamble is composed of a 12-bit “000000000000” sequence and a 4-bit “1010”. 'Sequence.

  Next, as shown in FIG. 3, the header field can be composed of a total of 3 bytes, but in order from the least significant bit to the most significant bit, for example, a 3-bit data rate and a coding information area, for example, an 8-bit payload It can be composed of a data length area, for example, a 5-bit reserved area and an 8-bit header check sequence (HCS). The length field of 8-bit payload data in such a header field indicates the length of data included in the payload in byte units. The header check sequence may be composed of, for example, an 8-bit cyclic redundancy check (CRC).

  Finally, the payload field can consist of a data area consisting of a maximum of 255 bytes and a frame check sequence of 2 bytes, for example, to protect it, but when the data length is 0, naturally the frame check The sequence is not included. The data rate and coding method for the preamble field, header field, and payload field are expressed by 3 bits, and can support a total of 8 methods as shown in Table 1 below.

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

  FIG. 6 is a diagram for explaining Manchester coding and NRZ-L coding that can be applied to the method of the present invention. As shown in FIG. 6, in the Manchester coding method, the signal level changes in the middle of the bit interval. When the data bit is “0”, the data bit changes from the level “1” to the level “0”. In the case of “1”, the level changes from “0” to “1”. The NRZ-L coding scheme is matched with level “0” when the data bit is “0” and level “1” when the data bit is “1”. As a result, the Manchester coding scheme has fewer DC components than the NRZ-L coding scheme, and is therefore advantageous, while it is disadvantageous in using twice the frequency band. Therefore, the NRZ-L coding method can be used when the communication environment is relatively good, and the Manchester coding method can be flexibly changed and used otherwise.

  FIG. 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 method has a disadvantage in that there are more DCs than the Manchester coding method, so that the result of NRZ-L coding to overcome this is scrambled as shown in FIG. It is desirable to suppress the DC component by processing.

  Here, “scrambler” means that the timing information of continuous input data is prevented from being lost, and a single frequency component generated by repeating a periodic data pattern is suppressed in the transmission line section. This is a known circuit for converting input data into a random code sequence to prevent mixing / modulation of the signal. On the receiving side, that is, a master or a slave, the original data is obtained by a descrambler having an opposite calculation function. The data signal can be reproduced.

  FIG. 8 is a diagram for explaining a preamble coding and modulation process in the method of the present invention. FIG. 9 is a diagram for explaining a header coding and modulation process in the method of the present invention. FIG. 6 is a diagram illustrating a process of coding and modulating payload data in the inventive method.

  First, as shown in FIG. 8, in the method of the present invention, the coding and modulation process for the preamble field is performed by encoding the generated preamble sequence using the type 0 of Table 1 above, that is, the Manchester coding method having a data rate of 1 kbps. After that, BPSK modulation is further performed. Similarly, the coding and modulation process for the header field has a data rate of type 0, that is, 1 kbps in Table 1 above after adding a header check sequence to protect the generated header sequence. Encoding is performed by the Manchester coding method, and further BPSK modulation is performed.

  On the other hand, in the case of the payload field, a payload check sequence for protecting this is added to the upper level of the data, and an appropriate data rate and coding method are selected from types 0 to 7 in Table 1 above. Encoding is performed, and the resulting encoded product is further BPSK modulated.

  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 with a Manchester coding scheme that is relatively stable against intermodulation interference, regardless of the surrounding communication environment. The payload field uses an appropriate data rate and coding method depending on the communication environment, and further improves communication performance by using Binary Phase Shift Keying (BPSK) modulation method. It can respond adaptively.

  In the configuration method of the physical layer in the wireless communication of the magnetic field based low frequency band according to the present invention, the slave, for example, the tag can be configured to be active, so that the tag can also issue an instruction to the interrogator, thereby The appropriate data rate and coding scheme can also be actively performed by both master and slave.

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

Claims (10)

In the configuration method of the physical layer in the magnetic field-based low frequency band wireless communication,
The magnetic field base is characterized in that the data rate and the coding method of the payload field included in the request frame and the response frame between the master and the slave can be changed within a predetermined range according to the surrounding communication environment. A configuration method of a physical layer in low-frequency wireless communication.   The method of claim 1, wherein the request frame and the response frame have the same format.   The method of claim 2, wherein the request frame and the response frame each include a preamble field, a header field, and a payload field.   4. The method of claim 3, wherein the preamble field is Manchester-coded at a data rate of 1 kbps and then BPSK modulated.   The magnetic field base of claim 4, wherein the header field includes 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. Of configuring the physical layer in low-frequency wireless communication.   The method of claim 5, wherein the header field is Manchester-coded at a data rate of 1 kbps and then BPSK-modulated.   7. The method of configuring a physical layer in magnetic field-based low frequency wireless communication according to claim 6, wherein the payload field includes a data area of 0-255 bytes and a frame check sequence of 2 bytes. .   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. 8. A configuration method of a physical layer in magnetic field-based low frequency wireless communication according to 7.   The method of claim 8, wherein the NRZ-L coded result is scrambled and then BPSK modulated.   A computer-readable recording medium on which a program for executing the physical layer configuration method in the magnetic field-based low-frequency band wireless communication according to any one of claims 1 to 9 is recorded.

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