KR101595298B1 - Mobile Magnetic Field Communication Method - Google Patents

Abstract

The mobile magnetic field communication protocol is a wireless communication technology for transmitting and receiving data using a magnetic field signal in a low frequency band (30 KHz to 300 KHz) on the move. The lower operating frequency of the wireless communication is 128 KHz, and the modulation method uses a frequency shift keying (FSK) method. Manchester coding and non-return-to-zero level (NRZ-L) coding, interleaving coding, Hamming coding, and scrambling to vary the data rate. Thereby providing a data rate of several Kbps at a distance of several meters.
The mobile magnetic field communication protocol affects the data transmission rate because the transmission channel state changes flexibly. The data transmission speed can be flexibly selected according to the transmission channel state. Also, by selecting an interleaving coding method and a Hamming coding method having an error correction function, the data transmission rate can be increased. This can be applied to sensor networks, home networks, and application services such as construction, agriculture, and transportation.

Description

[0001] The present invention relates to a mobile magnetic field communication method,

The present invention defines a physical layer of a wireless network for transmitting information using a magnetic field signal while moving in a low frequency band, and more specifically, defines a frame structure, a coding and a modulation scheme in a mobile field communication physical layer.

Magnetic Field Communication (Magnetic Field Communication) refers to a wireless communication technology for transmitting and receiving data using a magnetic field signal in a low frequency band. Mobile Magnetic Field Communication refers to a wireless communication technology for transmitting and receiving data using a magnetic field signal while moving in a low frequency band. A wireless communication protocol is required to efficiently perform such mobile magnetic field communication.

It is an object of the present invention to provide a wireless communication protocol for transmitting and receiving data using a magnetic field signal while moving in a low frequency band (30 KHz to 300 KHz). The center frequency of the wireless communication is 128 kHz, and the modulation method uses a frequency shift keying (FSK) method. Manchester coding and non-return-to-zero level coding (NRZ-L) coding, interleaving coding, and Hamming coding are used to diversify the data rate and adaptability in the radio propagation environment. Coding, and scrambling, thereby providing a data transmission rate of several kbps at a distance of several meters.

The method includes configuring a data frame to transmit via magnetic field communication; Transforming the data frame; And transmitting the transformed data frame using a frequency shift keying scheme.

Wherein the step of configuring a data frame to be transmitted through the magnetic field communication comprises forming a data frame including a preamble, a header and a payload, the header including a data rate and a coding field, a payload data length field, And the payload includes a data field and a frame check sequence field.

The data rate and coding field includes information on a data rate and a coding scheme applied to a payload of a data frame to be transmitted.

The header checks for errors in the header using a header check sequence generated using an 8-bit cyclic redundancy code.

The payload does not include a frame check sequence if the data length of the data field is 0, and checks the error of the data field using a frame check sequence generated using a 16-bit cyclic redundancy code.

Wherein the step of converting the data frame includes selecting a conversion scheme according to a data rate and a coding scheme, converting a payload included in the data frame according to the selected conversion scheme, Converts the preamble and header.

Wherein the step of transforming the data frame transforms the data frame using at least one of a Manchester coding scheme, a Nonreturn-to-Zero Level (NRZ-L) coding scheme, an interleaving coding scheme and a Hamming coding scheme, And converting the payload included in the data frame and scrambling the converted payload.

The present invention will contribute greatly to the development of USN and RFID technology as a wireless communication technology for transmitting information using a magnetic field signal while moving in a low frequency band. This technology can be applied to sensor network field for monitoring underground facility management, environmental pollution, natural disaster, etc., home network, and application service field such as construction, agriculture and traffic.

1 is a view showing an envelope form.
2 shows an FSK modulated signal;
3 is a diagram showing a frame structure of a physical layer;
4 shows a preamble structure.
5 shows a header structure.
6 is a diagram showing a coding circuit of a header check cyclic redundancy code.
7 shows a payload structure.
8 is a diagram showing a modulation method;
Figure 9 shows the definition of Manchester coding.
10 illustrates the definition of NRZ-L coding;
11 shows an interleaving matrix.
12 shows a scrambler structure;
13 is a diagram illustrating a process of modulating and coding a preamble.
14 is a diagram showing a process of modulating and coding a header;
15 shows a process of modulating and coding a payload;

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. And is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined by the claims.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. &Quot; comprises " and / or "comprising" when used in this specification is taken to specify the presence or absence of one or more other components, steps, operations and / Or add-ons. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Mobile magnetic field communication protocol

( Mobile Magnetic Field Communication Protocol )

1. Overview

The mobile magnetic field communication protocol is a wireless communication technology for transmitting and receiving data using a magnetic field signal in a low frequency band (30 KHz to 300 KHz) on the move. The lower operating frequency of the wireless communication is 128 KHz, and the modulation method uses a frequency shift keying (FSK) method. Manchester coding and non-return-to-zero level (NRZ-L) coding, interleaving coding, Hamming coding, and scrambling to vary the data rate. Thereby providing a data rate of several Kbps at a distance of several meters.

The mobile magnetic field communication protocol affects the data transmission rate because the transmission channel state changes flexibly. The data transmission speed can be flexibly selected according to the transmission channel state. Also, by selecting an interleaving coding method and a Hamming coding method having an error correction function, the data transmission rate can be increased. This can be applied to sensor networks, home networks, and application services such as construction, agriculture, and transportation.

2. Composition and scope of standards

This standard defines the physical layer of a wireless network that transmits data using magnetic field signals during movement in the low frequency band. In particular, it defines the mobile field communication physical layer frame structure, data rate, coding and modulation. This standard specifies a method of communicating in a low frequency band (30 KHz ~ 300 KHz) by constructing a few Kbps wireless network within a few meters of distance. This can be applied to sensor networks, home networks, and application services such as construction, agriculture, and transportation. This standard is to comply with the emission limit regulations that are allowed for non-licensed devices in each country.

3. Reference standards (Recommendations)

- None

4. Definitions

4.1. Terms

Magnetic Field Communication (Magnetic Field Communication): Wireless communication technology that transmits and receives data using magnetic field signals in low frequency band

Mobile Magnetic Field Communication: Wireless communication technology that transmits and receives data by using a magnetic field signal while moving in a low frequency band

4.2. Abbreviation

CRC cyclic redundancy check

HCS header check sequence

FCS frame check sequence

FSK frequency shift keying

5. Wireless Interface

5.1 Frequency

In mobile magnetic field communication, a minimum frequency-shift keying scheme is used for efficient wireless communication during movement. In the minimum frequency shift keying scheme, the difference between the low operating frequency (f ₀ ) and the high operating frequency (f ₁ ) is equal to half the bit rate. Therefore, the difference between the waveform representing 0 and 1 bit exactly matches half of the cycle. The maximum frequency deviation (δ) is 0.25 f _1. At this time, the center frequency f _c of the low operating frequency f ₀ and the high operating frequency f ₁ is 128 KHz, and the maximum tolerance of the frequency is ± 20 ppm.

5.2 Signal waveform

The converted bit signal according to the definitions in Chapters 6 and 7 is made of the envelope defined in Fig. 1 and Table 1.

Figure 1 shows the envelope shape, and Table 1 shows the envelope parameter. In Table 1, A is the size of the envelope. The magnitude of the envelope size can be divided into the positive change magnitude (M _h ) and the negative change magnitude (M _I ). The maximum value of M _h and M _I is within 10% of A

parameter symbol maximum Amount of Change M _h 0.1A Change of sound M _I 0.1A

The signal transmitted to the antenna is an FSK modulated signal according to the envelope defined in this section as shown in FIG.

6. Physical layer frame structure

This section defines the frame structure of the physical layer. As shown in FIG. 3, the physical layer frame includes a preamble, a header, and a payload. The frame is transmitted from the least significant bit (LSB).

6.1 Preamble

Preamble (Preamble) is composed of a 16-bit sequence, a 12-bit '0 (s)' and 16-bit and 4-bit 0101 8888 _{h 2} as shown in FIG. The first 12 bits of the preamble are used for packet synchronization and symbol time adjustment at the receiving end. 12 bits The following 16 bits are used for characterizing the magnetic field channel and are used for normal recovery of the received signal in the equalizer. The preamble is coded using the TYPE 0 scheme defined in Section 6.2.

6.2 Header

As shown in FIG. 5 and Table 2, the header includes a 4-bit data rate and coding field, an 8-bit payload data length field, a 4-bit reserved field, and an 8-bit header check sequence field. Since the header is transmitted from the LSB, the data rate and the LSB of the coding field are transmitted first, and the most significant bit (MSB) of the header check sequence is transmitted last. Headers are coded using the TYPE 0 scheme defined in this section.

beat Contents Remarks b3-b0 Data rate and coding The value of b3-b0 (4 bits) specifies the data rate and coding scheme. b11-b4 Payload data length The value of b11-b4 (8 bits) indicates the data length of the payload in bytes. The MSB is b11 and the LSB is b4. b15-b12 Reserved Reserved b23-b16 Header check sequence b23-b16 (8 bits) circulant residue code.

6.2.1 Data rate  And coding fields

The data rate and coding field specifies the data rate and coding scheme applied to the payload of a frame to be transmitted, and is represented by 4 bits as shown in Table 3. [

The bits (b3 b2 b1 b0) Data rate and coding 0000 TYPE 0 0001 TYPE 1 0010 TYPE 2 0011 TYPE 3 0100 TYPE 4 0101 TYPE 5 0110 TYPE 6 0111 TYPE 7 1000 TYPE 8 1001 TYPE 9 1010 TYPE 10 1011 TYPE 11 1100 TYPE 12 1101 TYPE 13 1110 TYPE 14 1111 TYPE 15

The data rate and coding method according to the data rate and the coding field value are defined as shown in Table 4. TYPE 0, TYPE 1, TYPE 2 use Manchester coding and the data rates are 1kbps, 2kbps and 4kbps, respectively. TYPE 3, TYPE 4, and TYPE 5 are scrambled after NRZ-L coding and the data rates are 2kbps, 4kbps and 8kbps, respectively. TYPE 6, TYPE 7 and TYPE 8 are scrambled after interleaving and Hamming coding, and data rates are 1kbps, 2kbps and 4kbps, respectively.

Data rate and coding Data rate Coding method Remarks TYPE 0 1 kbps Manchester - TYPE 1 2 kbps Manchester - TYPE 2 4 kbps Manchester - TYPE 3 2 kbps NRZ-L + scrambling - TYPE 4 4 kbps NRZ-L + scrambling - TYPE 5 8 kbps NRZ-L + scrambling - TYPE 6 1 kbps Interleaving + Hamming + Scrambling - TYPE 7 2 kbps Interleaving + Hamming + Scrambling - TYPE 8 4 kbps Interleaving + Hamming + Scrambling - TYPE 9-15 Reserved Reserved -

6.2.2 Payload  Data length field

The payload data length field consists of a total of 8 bits. The payload data length indicates the number of payload data of the transmitted frame in units of bytes. The payload data length is from 0 bytes to a maximum of 255 bytes.

6.2.3 Header Check Sequence Field

The header checks for errors using a header check sequence (HCS). The header check sequence is generated using an 8-bit cyclic redundancy code (CRC), and a primitive polynomial for this is given by Equation 1 below.

6 is an example of a coding circuit of a header check cyclic redundancy code. The initial value of the register of the encoding circuit is set to [0000 0000], data is input in the state that the switch S shown in FIG. 6 is '1', and when the last bit is inputted, the state of S is changed to '2' Transmits the sequence from the register. At this time, the value stored in D ⁷ is transmitted.

6.3 Payload

The payload is composed of a data field to be transmitted and a frame check sequence (FCS) field for checking an error therebetween as shown in FIG. When the length of the data is 0, the frame check sequence is not included. Therefore, the length of the payload is 0 to 257 bytes. The payload can select and transmit the data rate and coding scheme defined in Section 6.2 depending on the transmission channel state.

6.3.1 Frame Check Sequence Field

The frame check sequence field is generated using a 16-bit cyclic redundancy code. The frame check sequence is calculated for the payload data, and if the length of the payload data is 0, the frame check sequence is not generated. The frame check sequence is computed according to the definition in Table 5, and then it is replaced with 1's complement and sent after the data.

CRC type Length Polynomial Initial value Surplus value ISO / IEC 13239 16bits X ¹⁶ + X ¹² + X ⁵ + 1 0xFFFF 0x1D0F

7. Physical layer modulation and coding scheme

7.1 Modulation method

In mobile magnetic field communication, a minimum frequency-shift keying scheme is used for efficient wireless communication during movement. As shown in FIG. 8, the signal converted into each TYPE i (i = 0 to 8) is modulated to 0 at a low operating frequency ( f _c -x ) and 1 at a high frequency ( f _c + x ).

7.2 Coding scheme

7.2.1 Manchester

The Manchester coding changes the signal level in the middle of each bit interval (T _bit ) as shown in FIG. At this time, when the data bit is '0', the level changes from level '1' to level '0'. Conversely, when the data bit is '1', the level changes from level '0' to level '1'.

7.2.2 NRZ -L

The Nonreturn-to-Zero Level (NRZ-L) is matched to level '0' when the data bit is '0' and to level '1' when the data bit is '1' as shown in FIG.

7.2.3 Interleaving

The interleaving is defined as depth 6 and codeword length 8 as shown in FIG.

The position i of the output data is determined by the following equation (2). k means a value of 0 (codeword-1).

7.2.4 Hamming

The Hamming code is composed of a data bit and a parity bit for error detection / correction. The number of parity bits according to the number of data bits to be transmitted is obtained by the following equation (3).

d is the number of data bits, p is the number of parity bits, and the number of parity bits is the minimum value satisfying the formula. The parity bits are placed in the 2 ⁿ positions from the lowest 1. The parity check bits for each parity bit are read by the number of positions of each bit including itself and skipped by the number of positions. However, when calculating the parity, it excludes itself and applies even parity.

7.2.5 Scrambling

The payload of a frame using NRZ-L coding and interleaving coding is scrambled through a scrambler. However, the preamble and header are not scrambled. The primitive polynomial g (D) of the scrambler is given by the following equation (4).

Where D is a bit delay element. Fig. 12 shows a structure of a scrambler. Here, d _k is made according to the following equation (5).

는 GF(2) 덧셈(Exclusive OR)이다. 다항식의 초기값은 모두 1로 둔다. 데이터 입력 s_k를 스크램블링 되기 전의 비트라 두면 스크램블된 데이터 출력 b_k는 다음의 수학식 6과 같다.
At this time

Is a GF (2) addition (Exclusive OR). The initial value of the polynomial is set to 1. If the data input s _k is a bit before being scrambled, the scrambled data output b _k is given by Equation 6 below.

7.3 Modulation and coding process

In this section, a frame is formed for each of the preamble, the header, and the payload, and a series of processes for modulating and coding are defined.

7.3.1 Preamble

As shown in FIG. 13, the preamble transforms the preamble sequence defined in section 6.1 into the TYPE 0 scheme defined in section 6.2, and transmits the result using FSK modulation.

7.3.2 Headers

The header carries a total of 24 bits as defined in Section 6.2. As shown in FIG. 14, first, 8 bits of the header check sequence are added to 16 bits of the pure header information, the conversion is performed to the TYPE 0 scheme defined in Section 6.2, and the FSK modulation is used.

7.3.3. Payload

As shown in FIG. 15, the payload adds 16 bits of the payload check sequence to the data to be transmitted as described in Section 6.3, and selects one of the 9 types of conversion methods TYPE i (i = 0 to 8) are selected and converted and then transmitted using FSK modulation.

The foregoing description is merely illustrative of the technical idea of the present invention and various changes and modifications may be made without departing from the essential characteristics of the present invention. Therefore, the embodiments described in the present invention are not intended to limit the scope of the present invention, but are intended to be illustrative, and the scope of the present invention is not limited by these embodiments. It is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents, which fall within the scope of the present invention as claimed.

Claims (10)

A mobile magnetic field communication method for transmitting a data frame using a magnetic field signal during movement in a low frequency band (30 KHz to 300 KHz)
Constructing a data frame to transmit via magnetic field communication;
Transforming the data frame; And
And transmitting the transformed data frame using a minimum frequency shift keying scheme,
The data frame including a preamble, a header and a payload,
The header includes a 4-bit data rate and coding field applied to the payload,
Each of the data rate and the value of the coding field corresponds to one of TYPE 0 to TYPE 15 which indicates information on a data rate and a coding scheme applied to a data frame to be transmitted,
Wherein the step of transmitting the transformed data frame using a minimum frequency shift keying scheme comprises:
And transmits the data frame by using the minimum frequency shift keying after converting the sequence of the preamble and the header included in the data frame into the TYPE 0 scheme and selecting the payload from the TYPE 0 to the TYPE 8 And transmits using the minimum frequency deviation modulation,
Among TYPE 0 to TYPE 15, TYPE 0 to TYPE 2 are coded according to the Manchester coding scheme, TYPE 3 to TYPE 5 are coded according to NRZ-L (Nonreturn-to-Zero Level) coding scheme, To TYPE 8 are coded according to an interleaving coding scheme and a Hamming coding scheme and then scrambled.
2. The method of claim 1, wherein configuring a data frame for transmission via the magnetic field communication comprises:
A data frame including a preamble, a header and a payload,
The header includes a data rate and a coding field, a payload data length field, a reserved field and a header check sequence field, and the payload further includes a data field and a frame check sequence field
Wherein the method comprises the steps of:
delete 3. The method of claim 2, wherein the header checks for errors in the header using a header check sequence generated using an 8-bit cyclic redundancy code.
3. The method of claim 2, wherein the payload does not include a frame check sequence if the data length of the data field is zero.
The mobile magnetic field communication method of claim 2, wherein the payload checks an error of the data field using a frame check sequence generated using a 16-bit cyclic redundancy code.
delete The method according to claim 1,
The TYPE 0 uses the Manchester coding scheme,
Wherein the step of transforming the data frame comprises:
And converting the preamble and the header included in the data frame using the Manchester coding scheme according to the TYPE 0
Wherein the method comprises the steps of:
The method according to claim 1,
Some of TYPE 0 to TYPE 8 include a coding scheme and a scrambling operation,
Wherein the step of transforming the data frame comprises:
And converting the payload selected from the TYPE 0 to TYPE 8 using the coding scheme included in the selected TYPE and scrambling
Wherein the method comprises the steps of:
delete

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