KR102039910B1 - A preamble signal generating method for underwater ultra-wideband communication and a device thereof - Google Patents

Abstract

The present invention discloses a method and apparatus for generating a preamble signal for underwater ultra-wideband communication. In this method, (a) the baseband signal generation unit receives information data from an external source and maps it to a symbol signal of an orthogonal frequency division multiple modulation, and converts the mapped symbols to N-fold up-sampled baseband signals by inverse Fourier transform. Outputting; (b) a preamble signal generator sets a subcarrier offset in the orthogonal frequency division multiplexing modulation, arranges a signal string having a predetermined length at equal intervals, and then inversely transforms the arranged signal sequence to an N-fold up-sampled preamble signal. Generating a corresponding symbol string; (c) multiplexing and outputting a sample string of the baseband signal or a sample string of the preamble signal according to a signal frame structure by a transmission signal multiplexing unit; And (d) a transmitting unit receiving the multiplexed sample string and modulating the carrier frequency band to transmit the multiplexed sample string. According to the present invention, in an ultra-wideband communication system using orthogonal frequency division multiple modulation underwater, even when a Doppler shift occurs, data can be accurately recovered at a receiving node and easily used even when a DC frequency component is not transmitted. Will be.

Description

Preamble signal generating method for underwater ultra-wideband communication and a device

The present invention relates to a method and apparatus for generating a preamble signal, and in particular, in an ultra-wideband communication system using orthogonal frequency division multiple modulation in water, even when a Doppler shift occurs, the position of the preamble signal can be accurately located at a receiving node, and the DC frequency The present invention relates to a method and apparatus for generating a preamble signal for underwater ultra-wideband communication that can be easily used even when no component is transmitted.

In general, an underwater communication system has a carrier frequency in the range of several kHz to several tens of kHz, and the bandwidth used for information transmission uses a range of several kHz to several tens of kHz.

The ratio of the carrier frequency to the bandwidth to be used is about tens of percent, which is characteristic of an ultra-wideband signal.

In addition, a signal reaching the receiver due to relative movement of the communication nodes undergoes a Doppler shift. In the case of underwater communication, even when the communication nodes are fixed, the Doppler shift may occur due to the effects of currents and waves.

The Doppler shift is caused by the relative movement of the transmitting node and the receiving node, and this relative movement causes distortion in the time domain and the frequency domain.

In general, in the air communication, Doppler shift occurs due to the movement of the communication terminal, and distortion occurs in the time domain and the frequency domain, but the narrow band signal has a characteristic of a carrier band and the bandwidth used within a few%. Compared to the moving speed of the terminal, the moving speed of the radio wave is very fast, and thus the normalized Doppler shift has a very small value.

Due to this characteristic, the distortion in the time domain is effectively ignored because there is almost no change in symbol length in the time domain due to the Doppler shift, and the bandwidth used is very narrow compared to the carrier frequency. Model the same amount of frequency shift as occurring.

Based on this modeling, the Doppler shift is compensated for by using the phase and frequency synchronization functions present in the receiver.

However, in the case of underwater communication, the bandwidth used is wider than the carrier frequency, and a change in the symbol length effectively increases or decreases in the time domain due to the Doppler shift, and in the frequency domain depending on the frequency within the bandwidth used. Different frequency shifts occur.

In addition, due to the relatively large frequency change due to the Doppler shift, a frequency deviation larger than the subcarrier spacing may occur even at a low relative moving speed in a scheme such as orthogonal frequency division multiplexing.

 Here, the orthogonal frequency division multiplexing scheme refers to a scheme in which digital information is divided into multiple carriers (carriers) and multiplexed and transmitted by adding orthogonality to minimize the interval between the divided carriers. Each carrier of the is called a subcarrier.

For example, if an underwater communication system using Orthogonal Frequency Division Multiplexing (OFDM) has 1024 subcarriers and the symbol length is 32 ms, the subcarrier spacing is 31.25 Hz and a bandwidth of 32 kHz is required. Do.

Considering the feasibility of such a communication system, the carrier frequency of the orthogonal frequency division multiplexed modulated signal is assumed to be 128 kHz, which is four times the required bandwidth.

In this case, when the relative moving speed of the underwater communication node moves at 5 m / s, and the carrier frequency is 128 kHz and the sound velocity of the underwater sound wave is 1500 m / s, the normalized Doppler shift is 5/1500 (= about 0.0033), and the carrier The maximum Doppler shift frequency in frequency is about 426 Hz, which corresponds to about 13.7 subcarrier spacings in orthogonal frequency division multiplexing with a subcarrier spacing of 31.25 Hz.

When such a Doppler shift occurs in the orthogonal frequency division multiplexing of the underwater ultra-wideband communication, since the received signal is interpreted as a subcarrier signal different from the subcarrier band transmitted, the preamble signal cannot be detected correctly even when the signal is received. There was also a problem that can not be properly restored data transmitted through.

Therefore, in order to solve this problem, the present inventors, when Doppler shift greater than the subcarrier spacing occurs due to the relative movement of the transmitting node and the receiving node during orthogonal frequency division multiplex modulation in underwater ultra-wideband communication, A method of generating a preamble signal for underwater ultra-wideband communication that can accurately detect a preamble signal by allowing a correlation value to be close to an impulse response, and exclude a subcarrier corresponding to a DC frequency without any limitation in assigning a symbol string to a subcarrier. And the invention has been invented.

KR 10-0586532 B1

According to the present invention, in an ultra-wideband communication system using orthogonal frequency division multiple modulation in which a Doppler shift occurs larger than a subcarrier spacing in water, a symbol is obtained by converting a signal assigned to a subcarrier at regular intervals into a signal in a time domain. It is to provide a method of generating a preamble signal for underwater ultra-wideband communication using orthogonal frequency division multiple modulation that can accurately detect a preamble at a receiving node even when a Doppler shift occurs.

Another object of the present invention is to provide an apparatus for generating a preamble signal for underwater ultra-wideband communication for achieving the above object.

In order to achieve the above object, a method of generating a preamble signal for underwater ultra-wideband communication according to the present invention includes (a) a baseband signal generation unit receiving information data from an external device and mapping the data signal into a symbol signal of an orthogonal frequency division multiple modulation, wherein the mapped symbol Inverse Fourier transform to output an N-fold up-sampled baseband signal; (b) a preamble signal generator sets a subcarrier offset in the orthogonal frequency division multiplexing modulation, arranges a signal string having a predetermined length at equal intervals, and then inversely transforms the arranged signal sequence to an N-fold up-sampled preamble signal. Generating a corresponding symbol string; (c) multiplexing and outputting a sample string of the baseband signal or a sample string of the preamble signal according to a signal frame structure by a transmission signal multiplexing unit; And (d) a transmitting unit receiving the multiplexed sample string and modulating the carrier frequency band to transmit the multiplexed sample string.

In order to achieve the above object, the step (a) of the method of generating a preamble signal for underwater ultra-wideband communication according to the present invention may include (a-1) the symbol transmitted on each subcarrier of orthogonal frequency division multiple modulation from information received from the outside. The signal is mapped; (a-2) mapping the mapped symbol signal to each subcarrier of the orthogonal frequency division multiple modulation in a predetermined order; (a-3) determining a method of performing N-fold up-sampling; (a-4) when the method for performing N-fold up-sampling is to perform the up-sampling in a frequency domain, adding (N-1) times subcarriers in a high frequency band; And setting '0' to the added subcarrier and performing an inverse Fourier transform operation. (A-5) The N-fold up-sampling method performs the up-sampling in a time domain. Performing an inverse Fourier transform operation having a size equal to that of a subcarrier; Adding (N-1) sampling time points between samples in the inverse Fourier transform result; And setting '0' at the added sampling time point and performing interpolation filtering to generate N times and a sampled signal sequence. (A-6) Generated by the N-fold up-sampling method. And outputting a signal to be output.

In the step (b) of the preamble signal generation method of the underwater ultra-wideband communication of the present invention for achieving the above object, (b-1) one periodic signal storage unit takes into account the preamble generation parameter and the number of subcarriers, and thus the up-sampling multiple N Setting a and storing a result of calculating a signal corresponding to a first period of a signal to be repeated by the number of repetitions determined by a generation parameter in calculating the preamble signal; (b-2) calculating and storing a value which is multiplied by a signal output stored in the one periodic signal storage unit to generate the preamble signal sequence by a phase shifting and scaling storage unit; (b-3) storing the output value when the memory buffer advances one cycle in synchronization with the output signal cycle of the one cycle signal storage unit; And (b-4) performing a complex multiplication by receiving the output signal of the one periodic signal storage unit and the value stored in the memory buffer, and outputting the preamble signal by performing a complex multiplication.

In the step (b-1) of the method of generating a preamble signal for underwater ultra-wideband communication of the present invention for achieving the above object, the calculation of the signal corresponding to the first period is (b-1-1) N-fold up-sampling. Calculating an inverse Fourier transformed signal of one circular shifted Zadoff weight signal; (b-1-2) calculating a phase shift occurring in a section corresponding to a first period of a signal repeated in the preamble signal determined by the preamble generation parameter; And (b-1-3) the one period signal by rotating the inverse Fourier transform signal calculated in the step (b-1-1) by the phase shift calculated in the step (b-1-2). Storing in the storage unit.

The inverse pre-transformed signal in the step (b-1-1) of the preamble signal generation method of the underwater ultra-wideband communication of the present invention for achieving the above object corresponds to an inverse-Fourier transform of the Jadopuchu signal which is circularly shifted. It is characterized by calculating using a formula representing a circular shift shifted Zadoff weight signal sequence.

In the step (b-2) of the method of generating a preamble signal for underwater ultra-wideband communication of the present invention for achieving the above object, a signal stored in the one periodic signal storage unit to generate the N-fold up-sampled preamble signal. Is calculated by multiplying when the signal is repeated for the number of repetitions determined according to the preamble generation parameter and the number of subcarriers, and is stored for the preamble signal generation while the one periodic signal storage unit outputs the signal for one stored period. It is characterized by having the same value during the period and having a different value in each period by the preamble generation parameter.

(C) step (c) of the preamble signal generation method of the underwater ultra-wideband communication of the present invention for achieving the above object is the step of outputting the sample string of the preamble signal in the preamble symbol period; And (c-2) outputting a sample string of the baseband signal part in the data symbol period after the preamble symbol period.

According to another aspect of the present invention, there is provided a method of generating a preamble signal for underwater ultra-wideband communication, comprising: receiving a signal output from the transmitter and performing sampling at a predetermined multiple per symbol; Performing a frequency shift to reduce a frequency by a carrier frequency by receiving the sampled signal by a demixing unit; A low pass filter receiving the frequency shifted signal and passing only a signal corresponding to the baseband signal and removing a signal component corresponding to a harmonic component; A correlation value calculating unit receiving an output of the low pass filter to calculate a correlation value with a conjugate complex number of a preamble signal sequence already known; And receiving, by the received signal processor, the calculated correlation value to calculate energy to detect the start of the signal frame.

The received signal processing unit of the preamble signal generation method of the underwater ultra-wideband communication of the present invention for achieving the above object receives a Doppler shift, a symbol time shift, and a frequency shift by using the output of the low pass filter by receiving the calculated correlation value. , To compensate for the phase shift.

에 의해 생성되되, 상기 M은 부반송파의 개수로 M=Q*

의 관계가 있고, 상기

는 자도프추 심볼열의 크기이며, 상기 q는 상기

길이의 심볼열을 Q개만큼 균일하게 떨어진 부반송파에 할당할 때, DC에서의 오프셋 값이고, 상기 n은 샘플링 시간으로서

의 관계를 가지며, 상기 r은 0부터 (Q-1) 이하의 정수이고, 상기 s는 0부터 (

-1) 이하의 값을 갖는 실수인 것을 특징으로 한다.In order to achieve the above object, the sample sequence on the time axis of the preamble signal of the preamble signal generation method of the underwater ultra-wideband communication according to the present invention is a first equation without inverse Fourier transform.

Generated by M = Q *, where M is the number of subcarriers

There is a relationship between

Is the size of the Zadoffchu symbol string, and q is the

When assigning the length of the symbol string to subcarriers uniformly separated by Q, it is an offset value in DC, and n is a sampling time.

R is an integer of 0 to (Q-1) or less, and s is 0 to (

-1) It is a real number which has the following values.

항은 제2 수학식

에 의해 산출되되, 상기

는

의 정수배를 더하거나 빼서

사이의 값으로 변환된 값인 것을 특징으로 한다.In the first equation of the method of generating a preamble signal for underwater ultra-wideband communication of the present invention for achieving the above object

The term is the second equation

Calculated by the above

Is

By adding or subtracting an integer multiple of

Characterized in that the value is converted to the value between.

항은 제3 수학식

에 의해 산출되되, 상기

는 0부터 (

-1) 이하의 값을 갖는 실수 s 범위에서 신호열의 길이이고, 상기

는 0부터 (

-1) 이하의 값을 갖는 실수 s 범위에서

범위의 값인 것을 특징으로 한다.In the second equation of the preamble signal generation method of underwater ultra-wideband communication of the present invention for achieving the above object

The term is the third equation

Calculated by the above

From 0 (

-1) the length of the signal sequence in the real s range having a value less than or equal to

From 0 (

-1) in real s range with a value less than or equal to

It is characterized by the value of the range.

항은 상기

가 짝수인 경우,

=

이고, 상기

가 홀수인 경우,

=

에 의해 산출되되, 상기

는 제4 수학식

이고, 상기

항은 제5 수학식

이며, 상기

항은 제6 수학식

이고, 상기 s는 0부터 (

-1) 이하의 값을 갖는 실수이고, 상기

는 신호열의 길이이며, 상기

이고, 상기 R은 신호열 생성시 자도프 추 신호열에 대해 원형 시프트한 값으로서, 0부터 (

-1)까지의 정수 중 하나로 사용자에 의해 설정할 수 있는 값인 것을 특징으로 한다.In the third equation of the method of generating a preamble signal for underwater ultra-wideband communication of the present invention for achieving the above object

Term above

Is an even number,

=

And above

Is an odd number,

=

Calculated by the above

Is the fourth equation

And above

The term is the fifth equation

And said

The term is the sixth equation

S is from 0 (

-1) is a real number with a value less than or equal to

Is the length of the signal string,

R is a value shifted circularly with respect to the Zadoff weight signal sequence when generating the signal sequence.

Characterized by the user as one of the integers up to -1).

로 사용하여 상기 프리앰블 신호의 샘플열을 생성하는 것을 특징으로 한다.In order to achieve the above object, a method of generating a preamble signal for underwater ultra-wideband communication according to the present invention is R;

It is characterized by generating a sample string of the preamble signal using.

In order to achieve the above object, the sample string of the preamble signal of the preamble signal generation method of underwater ultra-wideband communication according to the present invention is characterized in that it is a Zadoff-Chu complex symbol string.

In order to achieve the above object, a method of generating a preamble signal for underwater ultra-wideband communication according to the present invention includes (a) a baseband signal generation unit receiving information data from an external device and mapping the data signal into a symbol signal of an orthogonal frequency division multiple modulation, wherein the mapped symbol Inverse Fourier transform to output an N-fold up-sampled baseband signal; (b) a preamble signal generator sets a subcarrier offset in the orthogonal frequency division multiplexing modulation, arranges a signal string having a predetermined length at equal intervals, and then inversely transforms the arranged signal sequence to an N-fold up-sampled preamble signal. Generating a corresponding symbol string; (c) multiplexing and outputting a sample string of the baseband signal or a sample string of the preamble signal according to a signal frame structure by a transmission signal multiplexing unit; And (d) a transmitting unit receiving and transmitting the multiplexed sample string, wherein the generated preamble signal is modulated to have a characteristic of a chirp signal.

According to another aspect of the present invention, an apparatus for generating a preamble signal for underwater ultra-wideband communication receives information data from an external source, maps the information signal into a symbol signal of an orthogonal frequency division multiple modulation, and inversely performs Fourier transform on the mapped symbol signal. A baseband signal generator for outputting a double up-sampled baseband signal; A preamble signal generator configured to set subcarrier offsets in the orthogonal frequency division multiplexing modulation, arrange signal sequences having a predetermined length at equal intervals, and inversely Fourier transform the arranged symbols to generate N-fold up-sampled preamble signals; A transmission signal multiplexing unit multiplexing a sample string of the baseband signal or a sample string of the preamble signal according to a signal frame structure; And a transmitter configured to receive the multiplexed sample string and modulate it in a carrier frequency band for transmission.

The preamble signal generation unit of the preamble signal generation apparatus of the underwater ultra-wideband communication of the present invention for achieving the other object sets the up-sampling multiple N in consideration of a preamble generation parameter and the number of subcarriers, and a part of the preamble signal One period signal storage unit for storing the result of calculating the; A phase shift and scaling storage unit for storing a result of calculating the remaining term of the preamble signal; A memory buffer configured to store a value output when the cycle progresses by one period in synchronization with an output signal period of the one period signal storage unit; And a complex multiplier configured to receive the output signal of the one periodic signal storage unit and a value stored in the memory buffer to perform a complex multiplication to output the preamble signal.

According to another aspect of the present invention, there is provided a preamble signal generation apparatus for underwater ultra-wideband communication, which receives a signal output from the transmitter and performs sampling at a predetermined multiple per symbol and outputs the signal; A demixing unit which receives the sampled signal and performs a frequency shift to lower the frequency by a carrier frequency; A low pass filter receiving the frequency shifted signal and passing only a signal corresponding to the baseband signal and removing a signal component corresponding to a harmonic component; A correlation value calculation unit receiving the output of the low pass filter and calculating a correlation value with a conjugate complex number of a preamble signal sequence already known; And a received signal processor configured to detect the start of the signal frame by calculating energy by receiving the calculated correlation value.

Specific details of other embodiments are included in the "details for carrying out the invention" and the accompanying "drawings".

Advantages and / or features of the present invention and methods for achieving them will become apparent with reference to the various embodiments described below in detail in conjunction with the accompanying drawings.

However, the present invention is not limited to the configuration of each embodiment disclosed below, but may be implemented in a variety of different forms, each embodiment disclosed herein is only to complete the disclosure of the present invention, It should be understood that the present invention is provided to fully inform those skilled in the art to which the invention pertains, and the present invention is defined only by the scope of each claim of the claims.

According to the present invention, when orthogonal frequency division multiplexing modulation is used, even when a Doppler shift occurs larger than a subcarrier spacing due to relative movement of a transmitting node and a receiving node, the position of a preamble symbol can be accurately detected. Can be.

In addition, in the orthogonal frequency division multiple modulation, a subcarrier corresponding to a DC frequency can be excluded without any limitation in assigning a symbol string to a subcarrier, and thus it can be easily used in an orthogonal frequency division multiple modulation method that does not transmit DC frequency components. Will be.

1 is a block diagram of an apparatus for generating preamble signals for underwater ultra-wideband communication according to the present invention.
FIG. 2 is an internal block diagram of the preamble signal generator 200 in the preamble signal generator shown in FIG. 1.
3 is a block diagram of an orthogonal frequency division multiple modulation scheme frame for applying the present invention.
4 is a block diagram of an orthogonal frequency division multiple symbol in which a cyclic prefix is copied and added to one orthogonal frequency division multiple symbol.
5 is a flowchart illustrating a process of generating a preamble signal for underwater ultra-wideband communication according to the present invention.
FIG. 6 is a flowchart illustrating a partial operation of step S100 of the method of generating a preamble signal shown in FIG. 5.
FIG. 7 is a flowchart illustrating a partial operation of step S200 of the method of generating the preamble signal shown in FIG. 5.
FIG. 8 is a flowchart illustrating a partial operation of one period generating operation in step S300 of the method of generating a preamble signal shown in FIG. 5.
9 is a graph showing a real part (a) and an imaginary part (b) of a Zadoff weight symbol string having a length of 128 in the frequency domain according to the present invention.
FIG. 10 is a graph illustrating a signal changed to a time axis by using an inverse Fourier transform operation on the real part (a) and the imaginary part (b) of the symbol string shown in FIG. 9.
FIG. 11 is a graph illustrating a 128-length symbol string modified according to the present invention with respect to the real part (a) and the imaginary part (b) of the symbol string shown in FIG. 9.
FIG. 12 is a graph illustrating signals converted to a time axis by using an inverse Fourier transform operation on the real part (a) and the imaginary part (b) of the symbol string shown in FIG. 11.
FIG. 13 is a graph showing a real part (blue) and an imaginary part (red) of a sample sequence of a time domain of a signal in which a transformed symbol is arranged at eight subcarrier intervals in an orthogonal frequency division multiplex signal having 1024 subcarriers according to the present invention; to be.
FIG. 14 is a graph of a time domain sample sequence illustrated in FIG. 13 on a two-dimensional signal plane.
15 and 16 illustrate a 16-time up-sampled signal using an inverse Fourier transform operation after inserting as many zero subcarriers as necessary (15 * 1024) into the time domain sample sequence shown in FIG. It is a graph.
17 is a graph of a 16-fold up-sampled preamble signal sequence using an inverse Fourier transform operation in accordance with the present invention.
FIG. 18 is a flowchart illustrating a subsequent operation after step S500 of the method of generating a preamble signal shown in FIG. 5.
19 is a graph showing a result of calculating a correlation value between a received signal and a preamble signal when there is 1% normalized Doppler shift.
20 is a graph of the result of measuring the peak value change of the correlation value according to the normalized Doppler shift.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Before describing the present invention in detail, the terms or words used in the present specification should not be construed as being limited to ordinary or dictionary meanings, and in order for the inventor of the present invention to explain his invention in the best way. Concepts of various terms may be properly defined and used, and furthermore, it is to be understood that these terms or words should be interpreted as meanings and concepts corresponding to the technical spirit of the present invention.

In other words, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting the teachings of the invention. It should be understood that the term is defined in consideration.

In addition, in the present specification, the singular expressions may include the plural expressions unless the context clearly indicates otherwise, and similarly, the plural expressions may include the singular meanings. do.

Throughout this specification, when a component is described as "comprising" another component, the component may further include any other component rather than excluding any other component unless otherwise stated. It can mean that you can.

Furthermore, if a component is described as being "inside, or in connection with," another component, the component may be directly connected or installed in contact with another component, The components may be spaced apart from each other, and in the case of spaced apart from each other, there may be a third component or means for fixing or connecting the components to other components. It should be understood that the description of the components or means of 3 may be omitted.

On the other hand, if a component is described as being "directly connected" or "directly connected" to another component, it should be understood that no third component or means exists.

Similarly, other expressions describing the relationship between each component, such as "between" and "immediately between", or "neighboring to" and "directly neighboring to", have the same purpose. Should be interpreted as

In addition, in this specification, terms such as “one side”, “other side”, “one side”, “other side”, “first”, “second”, and the like, if used, refer to this one component for one component. Is used to clearly distinguish from other components, and it should be understood that such terms do not limit the meaning of the components.

In addition, terms related to positions such as “up”, “down”, “left”, “right”, etc., when used herein, should be understood to indicate relative positions in the corresponding drawings with respect to the corresponding components, if used. Unless an absolute position is specified with respect to these positions, these position related terms should not be understood as referring to an absolute position.

Moreover, in the specification of the present invention, the terms "… unit", "… unit", "module", "device" and the like, if used, means a unit capable of processing one or more functions or operations, which is hardware Or software, or a combination of hardware and software.

In addition, in the present specification, in designating the reference numerals for each component of each drawing, the same reference numerals refer to the same components so as to have the same reference numerals even though they are shown in different drawings, that is, the same reference numerals throughout the specification. The symbols indicate the same components.

In the accompanying drawings, the size, position, coupling relationship, etc. of each component constituting the present invention may be partially exaggerated or reduced or omitted in order to sufficiently convey the spirit of the present invention or for convenience of description. It may be described, so the proportion or scale may not be exact.

In addition, in the following, in the following description of the present invention, detailed descriptions of configurations known to unnecessarily obscure the subject matter of the present invention, for example, known technologies including the prior art, may be omitted.

1 is a block diagram of an apparatus for generating a preamble signal for underwater ultra-wideband communication according to the present invention, which includes a baseband signal generator 100, a preamble signal generator 200, a transmit signal multiplexing unit 300, and a transmitter 400. And a receiver 500, a demixer 600, a low pass filter 700, a correlation value calculator 800, and a received signal processor 900.

FIG. 2 is an internal block diagram of the preamble signal generator 200 in the preamble signal generator shown in FIG. 1. The periodic signal storage 210, the phase shift and scaling storage 220, and the memory buffer 230 are illustrated in FIG. And a complex multiplication unit 240.

3 is a block diagram of an orthogonal frequency division multiple modulation scheme frame for applying a method for generating a preamble signal for underwater ultra-wideband communication according to the present invention.

4 is a configuration diagram of an orthogonal frequency division multiple symbol in which a cyclic prefix is copied and added to one orthogonal frequency division multiple symbol.

5 is a flowchart illustrating a process of generating a preamble signal for underwater ultra-wideband communication according to the present invention.

FIG. 6 is a flowchart illustrating a partial operation of step S100 of the method of generating a preamble signal shown in FIG. 5.

FIG. 7 is a flowchart illustrating a partial operation of step S200 of the method of generating the preamble signal shown in FIG. 5.

FIG. 8 is a flowchart illustrating a partial operation of one period generating operation in step S300 of the method of generating a preamble signal shown in FIG. 5.

Referring to Figures 1 to 8 schematically illustrate the process of the preamble signal generation method of underwater ultra-wideband communication of the present invention.

The baseband signal generator 100 receives information data from an external source and maps the information data to a symbol signal of each subcarrier according to an arrangement rule defined on a subcarrier of an orthogonal frequency division multiple modulation, and performs an inverse Fourier transform and an N-fold up-sampling method. By using the N-fold up-sampled baseband signal is output (S100).

In this case, the N-fold up-sampling method can be largely divided into a method performed in the frequency domain and a method performed in the time domain, or a combination of the two methods can be used.

Here, the method of N-fold up-sampling in the frequency domain adds (N-1) -fold subcarriers in the high frequency band, sets a value of '0' to the added subcarriers, and performs an inverse Fourier transform operation. Generate an N-fold up-sampled signal sequence.

In the time domain, the method of N-fold up-sampling includes inverse Fourier transform by the number of subcarriers, (N-1) sampling time points are added between samples in the inverse Fourier transform operation, and '0' is added to the added sampling time point. The N-fold up-sampled signal sequence is generated by performing interpolation filtering.

The preamble signal generator 200 sets a subcarrier offset in an orthogonal frequency division multiplexing modulation having a predetermined number of subcarriers, arranges a differentially shifted doped weight signal sequence of a predetermined length at regular intervals, and inversely performs Fourier transform on the subcarrier. A symbol string corresponding to the up-sampled preamble signal is generated (S200).

In this case, the inverse Fourier transform of the subcarrier signal of the orthogonal frequency division multiple modulation in which the circularly shifted doped weight signal sequence is arranged has a periodic characteristic, and the result of the inverse Fourier transform of the circularly shifted Zadoff weight signal is also modified. Characteristic that can be represented by using a signal, the preamble signal during N-fold up-sampling does not perform operations such as inverse-Fourier transform operation and interpolation according to the present invention, which moves along a circle having a predetermined size on the signal constellation. And generate an N-fold up-sampled preamble signal.

The transmission signal multiplexing unit 300 multiplexes the sample string of the baseband signal generator 100 or the sample string of the preamble signal generator 200 according to the signal frame structure (S400).

The transmitter 400 transmits a signal by modulating a sample string received from the transmission signal multiplexing unit 300 into a carrier frequency band (S500).

The receiver 500 receives a signal transmitted from the transmitter 400, performs sampling at a predetermined multiple per symbol, and outputs the signal at step S610.

The demixing unit 600 receives a sampled signal received at a predetermined multiple per symbol and performs a frequency shift that lowers the frequency by the carrier frequency (S620).

The low pass filter receives a frequency shift signal from the demixing unit 600 and passes only a signal corresponding to the baseband signal and performs low pass filtering to remove signal components corresponding to the harmonic component (S630).

The correlation value calculator 800 calculates a correlation value between the conjugate complex number of the preamble signal sequence already known and the output of the low pass filter 700 (S640).

The correlation value calculation result can be used to detect the start of the signal frame and to estimate the Doppler shift.

The received signal processor 900 receives the correlation value calculated by the correlation value calculator 800 to calculate the energy to detect the start of the signal frame (S650).

In addition, a Doppler shift, a symbol time shift, a frequency shift, a phase shift, and the like are compensated for by using the output of the low pass filter 700 corresponding to the detected frame signal.

5 and 6, a partial operation of step S100 of the preamble signal generation method for underwater ultra-wideband communication according to the present invention will be described as follows.

The symbol signal S110 of the orthogonal frequency division multiplexing modulated by receiving information data from the outside is transmitted in each subcarrier of the orthogonal frequency division multiplexing in a predetermined order (S120).

It is determined how to perform the N-fold up-sampling (S140). When up-sampling in the frequency domain, subcarriers of (N-1) times are added in the high frequency band (S150).

'0' is set to the added subcarrier (S160), and an inverse Fourier transform operation is performed (S170) to output a signal generated by the N-fold up-sampling method (S190).

As a result of the determination in step S140, when the N-fold up-sampling is performed in the time domain, an inverse Fourier transform operation is performed using only a predetermined subcarrier (S145). Number of sampling points are added (S155), '0' is set at the added sampling point (S165), and N times up-sampled signal sequence is generated by performing interpolation filtering (S175) (S185). A signal generated by the fold up-sampling method is output (S190).

2 and 7, a partial operation of step S200 of the preamble signal generation method for underwater ultra-wideband communication according to the present invention will be described as follows.

The periodic signal storage unit 210 sets the up-sampling multiple N in consideration of the preamble generation parameter and the number of subcarriers, and in the baseband preamble signal calculation, the first period of the signal which is repeated by the number of repetitions determined by the generation parameter. The signal string corresponding to the storage is stored (S210).

The signal sequence corresponding to this first period is an interval corresponding to the first period of the signal repeated in the inverse pre-converted signal of the N-fold up-sampled circular shifted Zadoff weight signal and the preamble signal determined by the preamble generation parameter. This is a signal sequence applying the generated phase shift.

Here, the inverse pre-transformed signal of the N-fold up-sampled shifted Zadoff weights signal is subjected to the inverse Fourier transform of the circularly shifted Zadoff weights signal, followed by a signal along a circle having a constant magnitude in the signal constellation. Obtains the same calculation result as N-fold up-sampling to change, but does not use the inverse Fourier transform and the N-fold up-sampling method described with reference to FIG. Calculate using

Phase shifting and scaling storage 220 generates a preamble signal while a signal stored in the periodic signal storage 210 outputs a signal for one period to generate the N-fold up-sampled preamble signal sequence. In order to store the signal size and the amount of phase change to be multiplied during each period, the same value is used during the output of one period signal of the one period signal storage unit 210 (S220).

The memory buffer 230 may shift the phase corresponding to a corresponding period to be multiplied when the one period signal storage unit 210 outputs a signal for one period in synchronization with the output signal period of the one period signal storage unit 210. And storing the output value of the scaling storage unit 220, and outputting the value to the input of the complex multiplication unit 240 (S230).

In addition, the complex multiplier 240 receives the output signal of the one periodic signal storage unit 210 and the value stored in the memory buffer 230 to perform a complex multiplication to output a preamble signal (S240).

A detailed operation of the method for generating a preamble signal for underwater ultra-wideband communication of the present invention with reference to FIGS. 1 to 8 will be described later.

The orthogonal frequency division multiplexed modulation signal considered in the present invention has one frame structure, one frame is composed of L orthogonal frequency division multiple symbols, one orthogonal frequency division multiplex symbol is composed of K subcarriers do.

As shown in FIG. 3, one orthogonal frequency division multiple symbol transmitted consists of a cyclic prefix (CP) portion and an orthogonal frequency division multiple symbol portion.

The cyclic prefix is located at the beginning of each symbol, and its length is determined by considering channel effects such as multipaths, and the length is called a guard interval (GI).

The cyclic prefix is copied as the length of the boundary section at the end of each orthogonal frequency division multiple symbol and used as the cyclic prefix of the symbol.

It is assumed that a preamble symbol known to both the transmitter and the receiver is transmitted at the beginning of the frame in one frame structure.

In addition, some of the data symbols of the frame may be used as pilot symbols for channel equalization or the like.

A complex symbol string called Zadoff-Chu, which is widely used as a preamble symbol in an orthogonal frequency division multiple modulation method, is defined as in Equations 1 and 2 for the case where the symbol strings are even and odd. do.

-1) 사이의 정수 중

와 서로소인 관계가 있는 자연수이며,

는 자도프추 심볼열의 크기다.Where u is from 1 (

Of integers between -1)

Is a natural number that has a mutual relationship with

Is the size of the Zadofchu symbol string.

Generalizing the Zadoff symbol strings in Equations 1 and 2 may be expressed as Equation 3 below.

는 x에 y의 정수배를 더하거나 빼서 0이상 y 미만([0, y))의 범위의 값으로 바꾸는 연산을 의미한다. here,

Denotes an operation that adds or subtracts an integer multiple of y to x to a value in the range of 0 or greater than y ((0, y)).

인 경우는 가장 높은 주파수를 갖는 부반송파의 신호로 사용된다.In Xp (k) of Equation 3, k = 0 is used as a signal of a subcarrier having the lowest frequency, and is used as a signal of a subcarrier having a high frequency sequentially according to k, and k =

Is used as the signal of the subcarrier with the highest frequency.

A subcarrier corresponding to a carrier of orthogonal frequency division multiple modulation is a subcarrier located in the center of the subcarriers, and a subcarrier located in the center of the subcarriers corresponding to the carrier corresponds to a frequency component having a DC component in the baseband.

In addition, subcarriers having a lower frequency than subcarriers corresponding to the carrier have a negative frequency at baseband, and subcarriers having a higher frequency than the subcarriers corresponding to the carrier correspond to a positive frequency band at baseband.

 By applying this characteristic, an inverse Fourier transform (IFT) operation of the orthogonal frequency division multiplex signal mapped in the baseband may be performed as an equation (4) to convert the signal into a time axis signal.

이고, floor(x)는 x보다 크지 않은 최대 정수를 얻는 연산이다. Where n = 0,1, ...,

Floor (x) is an operation to obtain the largest integer not greater than x.

As an example, using u = 1 and obtaining a Chadov weight symbol string having 128 lengths, the result is as shown in FIG. 9, and the result of the inverse Fourier transform operation is converted into a time axis signal as shown in FIG. 10.

9 is a graph showing a real part (a) and an imaginary part (b) of a Zadoff weight symbol string having a length of 128 in the frequency domain according to the present invention.

FIG. 10 is a graph illustrating a signal converted to a time axis by using an inverse Fourier transform operation on the real part (a) and the imaginary part (b) of the symbol string shown in FIG. 9.

FIG. 11 is a graph illustrating a 128-length symbol string modified according to the present invention with respect to the real part (a) and the imaginary part (b) of the symbol string shown in FIG. 9.

FIG. 12 is a graph illustrating signals converted to a time axis by using an inverse Fourier transform operation on the real part (a) and the imaginary part (b) of the symbol string shown in FIG. 11.

In FIG. 9, the doddochu symbol string (y-axis) is shown for k (x-axis).

Referring to the frequency domain data of the Zadoff weight symbol string of FIG. 9, the change amount of the signal is large (high frequency component) at the center of the symbol string corresponding to the carrier frequency region, and the change amount of the signal decreases as it moves away from the carrier frequency region (low frequency component). ) Shows characteristics.

Accordingly, the present embodiment is devised by modifying the equation as shown in Equation 5 to show a shape similar to that of the chirp signal.

Here, the chirp signal is a signal whose frequency changes with time, also referred to as a linear frequency modulation signal.

의 주기를 갖는 특성이 있으므로, R 은 0과

사이의 임의의 정수로 정의한다.Here, R may use any integer, but the signal of Equation 5

R has a property of 0 and R is 0

Defined as any integer in between.

/2)의 값을 갖는 것을 고안한다.In this embodiment, to have a shape similar to that of the chirp signal, u has a value of 1 and R is floor (

Devise a value of 2).

Here, floor (x) means an operation of obtaining a maximum integer not greater than x.

11 and 12, it can be seen that the frequency component close to the carrier frequency has a relatively small amount of change, and the larger the frequency difference between both sides of the carrier frequency, the larger the amount of change.

에 대해 주기적이라는 특성을 이용하여 수학식 5는 수학식 3을 이용하여 수학식 6과 같이 표현할 수 있음을 용이하게 증명할 수 있다.Zadoff Chu Symbol Column

Equation 5 can be easily demonstrated using Equation 3 using Equation 3.

That is, the new signal sequence generated by Equation 5 may be referred to as a signal sequence circular shifted by R with respect to the Zadoff weight signal sequence generated by Equation 3.

에 대하여 주기적인 특성을 가짐을 용이하게 증명할 수 있다. New signal sequence generated by Equation 5 also the size of the signal sequence

It can be easily proved to have a periodic characteristic with respect to.

길이의 신호열을 다음의 수학식 8과 같이 표현한다.Using Equations 6 and 7 for ease of expression in the inverse Fourier transform operation of a new signal sequence, etc.

The signal sequence of length is expressed as in Equation 8 below.

이고,

은

를

만큼 원형 시프트(circular shift)시킨 것으로,

을 이용한 역 푸리에 변환은 수학식 9와 같이 되며, 이는 일반적으로 알고 있는 역 푸리에 변환식을 그대로 사용할 수 있게 하기 위해 표현을 달리 한 것이다. From here,

ego,

silver

To

Is circular shifted by

The Inverse Fourier Transform using Equation 9 is expressed as Equation 9, which is a different expression in order to use the inverse Fourier transform generally known.

개의 길이를 갖는 신호열을 이용하여, 신호열의 Q 배의 크기에 해당하는 부반송파 개수를 갖는 직교 주파수 분할 다중 변조의 프리앰블 신호 생성을 위해 Q*

개의 부반송파를 수학식 10과 같이 배치한다. As shown in Equations 5 to 8

To generate a preamble signal of orthogonal frequency division multiple modulation with subcarriers corresponding to Q times the signal sequence

Subcarriers are arranged as shown in Equation (10).

In the present invention, it is assumed that a subcarrier located at the center of a subcarrier is a carrier frequency of orthogonal frequency division multiple modulation for orthogonal frequency division multiple modulation.

은 직교분할 다중변조의 가장 낮은 주파수를 갖는 부반송파(0번째 부반송파)부터

번째 부반송파의 심볼이고, q는 사용자의 목적에 따라 0부터 (Q-1) 사이의 값을 가질 수 있으며, l=0,1,..., Q*

-1 이며, L=0, 즉, R = floor(N_ZC/2)을 사용한다. From here,

Is the subcarrier with the lowest frequency of orthogonal multimodulation (0th subcarrier).

Q is the symbol of the first subcarrier, q may have a value between 0 and (Q-1) according to the user's purpose, and l = 0,1, ..., Q *

-1, L = 0, that is, R = floor (N _ZC / 2).

An inverse Fourier transform is performed to convert a signal sequence mapped to a subcarrier into a signal on a time axis for generating a preamble symbol.

개의 부반송파에

개의 신호를 배치하고, 이의 역 푸리에 변환 연산을 다음과 같이 정의할 수 있다.M = Q * as in Equation 10

Subcarriers

Signals can be arranged and their inverse Fourier transform operations can be defined as follows.

로 표현하고, s는 0부터 (

-1) 이하의 정수이고, r은 0부터 (Q-1) 이하의 정수라고 정의하고, 이를 수학식 11에 대입하여 식을 정리하면 다음의 수학식 12와 같다.here,

Where s is from 0 (

-1) is an integer below and r is defined as an integer of 0 to (Q-1) or less, and substituted into Equation 11 to arrange the equation as shown in Equation 12 below.

의 역푸리에 변환이다. The last bracket in Equation 12 is the same as in Equation 9.

Inverse Fourier Transform.

In Equation 12, the inverse Fourier transform of the signal sequence of the present invention in the square bracket of Equation 12 is repeated Q times, and when repeated, the phase changes according to the signal sample index in the time domain, and the signal size is 1 /. You can see that it is multiplied by Q times.

길이를 갖는

의 역푸리에 변환이 시간에 따라 위상을 변화하면서 Q번 반복되며,

의 역푸리에 변환시 아래 수학식 13의

의 개수만큼의 주파수 증가와 감소가 반복되는 신호 형상을 보인다. That is, the signal on the time axis of the preamble symbol of orthogonal frequency division multiple modulation on the time axis proposed by the present invention is

Having a length

The inverse Fourier transform of is repeated Q times as the phase changes over time,

Inverse Fourier Transformation of Equation 13 below

Frequency increase and decrease by the number of times shows the repeated signal shape.

만큼의 주파수 증가와 감소가 반복되는 형상을 보인다. 이러한 시간축에서의 유사한 신호가 반복되는 개수는 주파수 축상의 신호열의 길이(

)를 조정하여 Q를 조정함으로써 변경할 수 있으므로, 본 발명에서는

및

인 경우로 한정한다. Accordingly, Q * in one preamble symbol period

As the frequency increases and decreases, the shape is repeated. The number of repetitions of similar signals in this time axis is determined by the length of the signal sequence on the frequency axis.

Can be changed by adjusting Q).

And

It is limited to the case.

The inverse Fourier transform of the Chadov weight signal sequence in square brackets in Equation 12 is designed in the present invention, and can be summarized as Equation 13 below by substituting Equation 3 above.

는 1부터

-1 사이의 정수로

의 모듈로 연산(

)에서 u의 곱셈에 대한 역이고,

는 x에 대하여

의 모듈로 연산으로 x에

의 정수배를 더하거나 빼서 0부터

사이의 값으로 변환하는 연산이며, x^*은 x의 공액 복소수를 나타낸다.here,

From 1

As an integer between -1

Modulo operation of

Is the inverse of the multiplication of u in

For x

Modulo operation of x

From zero by adding or subtracting integer multiples of

Is an operation that converts to a value between and x ^* represents a conjugate complex number of x.

는 다음의 수학식 14와 같이 표현된다.In addition,

Is expressed by Equation 14 below.

를 주기로 하는 주기 신호의 특성을 가짐으로 인하여 상기 수학식 14의

은 n에 관계 없이 같은 값을 가지며, 아래 수학식 15의 주기적 특성은 수학식 13의 정리 과정에서도 사용된다. The signal sequence devised in the present invention is as shown in Equation 15 below.

Equation (14) due to the characteristics of the periodic signal to

Has the same value irrespective of n, and the periodic characteristic of Equation 15 below is also used in the theorem of Equation 13.

개의 부반송파에

개의 신호를 배치하고, 이의 역 푸리에 변환 연산을 함에 있어, 수학식 11에 정의된 역 푸리에 변환 연산의 모든 과정을 수행하지 않고, 주파수영역에서 프리앰블로 사용되는 신호열과 시간 영역에서의 인덱스에 의한 위상 편이량을 곱하고, 차도프 추 신호열에 의해 정해지는 상수값을 곱하는 것으로 간략하게 시간 영역의 신호를 얻을 수 있다.Using Equations 12-14, M = Q *

Subcarriers

In order to arrange the four signals and perform the inverse Fourier transform operation, the phase by the signal sequence used as the preamble in the frequency domain and the index in the time domain without performing all the processes of the inverse Fourier transform operation defined in Equation (11) By multiplying the deviation amount and multiplying the constant value determined by the Chadov weight signal sequence, a signal in the time domain can be obtained simply.

=128, L=0을 적용하여 수학식 10에 따라 수학식 8에서 생성된 신호열을 배치하고, 이를 역 푸리에 변환 연산을 통하여 시간 축의 데이터로 바꾸면 도 13과 같이 된다. In one embodiment, q = 2 and Q = 8 are applied, M = 1024 subcarriers,

By applying = 128 and L = 0, the signal string generated in Equation 8 is arranged according to Equation 10, and the resultant is converted into data on the time axis through inverse Fourier transform.

FIG. 13 is a graph showing a real part (blue) and an imaginary part (red) of a sample sequence of a time domain of a signal in which a transformed symbol is arranged at eight subcarrier intervals in an orthogonal frequency division multiplex signal having 1024 subcarriers according to the present invention; to be.

FIG. 14 is a graph for redrawing the sample sequence of the time domain shown in FIG. 13 onto the signal plane.

In FIG. 13, it can be seen that a signal having a different phase is repeated eight times.

In addition, in FIG. 14, the red cross is 1024 inverse Fourier transform values, and the blue line is a concatenation between successive inverse Fourier transform values, whereby the tendency of the signal to change in the time axis can be confirmed.

Referring to FIG. 14, it can be seen that the path of change of the signal over time (blue line) almost fills the red circle, which means that there is a portion in which the size of the signal decreases in the time axis.

After generating the baseband signal of the orthogonal frequency division multiple modulation as described above, it is subjected to the modulation process to convert to the signal of the carrier frequency band.

In digital modulation, the orthogonal frequency division multiple baseband signal calculated above is further up-sampled by N times, and multiplied by the digital carrier frequency to convert the signal into a carrier frequency band signal.

In this case, a method of performing N-fold interpolation of baseband orthogonal frequency-division multi-signal samples on the time axis by N-fold up-sampling of the orthogonal frequency-division multiple baseband signal and a frequency band corresponding to a high frequency on the frequency axis. If the inverse Fourier transform operation is performed by adding (N-1) times subcarriers and setting '0' to the added subcarriers, the N times and the sampled signal sequence can be obtained.

Among the two methods described above, the baseband orthogonal frequency division multiplexing signal is 16 times up-sampled by applying the inverse Fourier transform operation. It is shown as 15 and FIG.

15 and 16 illustrate a 16-time up-sampled signal using an inverse Fourier transform operation after inserting as many zero subcarriers as necessary (15 * 1024) into the time domain sample sequence shown in FIG. It is a graph.

15 and 16, it can be seen that the up-sampled preamble signal has a signal size that is not the same as in FIGS. 13 and 14, and the signal size increases and decreases.

In the present invention, in order to reduce the change in the amplitude of the baseband preamble signal during the up-sampling of the orthogonal frequency division multiplexing baseband signal, the change in the signal during the up-sampling of the orthogonal frequency division multiplexing baseband preamble signal is measured in unit units (unit on the signal plane). Up-sampling signal of an orthogonal frequency division multiple baseband preamble signal is generated as follows.

로 한정하면, 다음의 수학식 16과 같이 정리할 수 있다. First, using Equations 12 to 14, u = 1 and as described above

In this case, it can be summarized as in the following equation (16).

는 x의 공액 복소수를 의미하며,

를 적용하였다. From here,

Means a conjugate complex of x,

Was applied.

의 관계가 있고, 상기

는 자도프추 심볼열의 크기이며, 상기 q는 상기

길이의 심볼열을 Q개만큼 균일하게 떨어진 부반송파에 할당할 때, DC에서의 오프셋 값이고, 상기 n은 샘플링 시간으로서

의 관계를 가지며, 상기 r은 0부터 (Q-1) 이하의 정수이고, 상기 s는 0부터 (

-1) 이하의 값을 갖는 실수로 정의하였다.In addition, M is the number of subcarriers M = Q *

There is a relationship between

Is the size of the Zadoffchu symbol string, and q is the

When assigning the length of the symbol string to subcarriers uniformly separated by Q, it is an offset value in DC, and n is a sampling time.

R is an integer of 0 to (Q-1) or less, and s is 0 to (

-1) It was defined as a real number with the following values.

-1) 이하의 실수로 범위를 확장하면, 수식에 변경 없이 적용이 가능하다. To apply this to the up-sampling signal, s is from 0 (

-1) If the range is expanded by mistake, it can be applied without changing the formula.

Equation 16 is expressed as the product of six terms, where the first term is a constant, the second term and the third term are constant values that vary with time on the time axis, and the fifth and sixth terms are The constant determined when L is determined.

Therefore, if the fourth term of Equation 16 is calculated according to s and multiplied with the remaining known values, the complex inverse Fourier transform is directly used for the time-base sample string generated by the symbol string arranged on the subcarrier for generating the preamble symbol on the frequency axis. You can get it without.

To obtain the fourth term of Equation 16, operations are performed in the following order.

= 0인 경우, if

If = 0,

가 1인 경우, 수학식 18을 이용하여

을 계산하고,

의 연산 결과의 부호를 판단하여 다음의 수학식 19와 같이 결정한다.And calculate

Is 1, using Equation 18

, And

The sign of the result of the calculation of is determined by the following equation (19).

-1) 이하의 값을 갖는 실수이고, 상기

는 신호열의 길이이며, 상기

이고, 상기 R은 신호열 생성시 자도프 추 신호열에 대해 원형 시프트한 값으로서, 0부터 (

-1)까지의 정수 중 하나로 사용자에 의해 설정할 수 있는 값인데, R을

로 사용하여 신호열을 생성할 수 있다.In this case, s is from 0 (

-1) is a real number with a value less than or equal to

Is the length of the signal string,

R is a value shifted circularly with respect to the Zadoff weight signal sequence when generating the signal sequence.

One of the integers up to -1) that can be set by the user.

It can be used to generate a signal sequence.

가 음수가 되는 값의 영역은 L에 의해 정해지므로, 수학식 19와 같이

의 곱셈 결과를 이용하지 않고 L에 의해 사전에 정해진 s의 구간에

를 더하는 방법도 있다. In equation (19)

Since the area of the negative value is determined by L, as shown in Equation 19,

In the interval of s previously determined by L without using the multiplication result of

There is also a way to add.

가 짝수인 경우

는 수학식 18의

를 의미하고,

가 홀수인 경우

는 수학식 19의

를 의미하는 것으로 정의하고 다음의 수학식 20과 같이 전개한다.

Is an even number

Of equation (18)

Means,

Is odd

Of equation (19)

Is defined as meaning and expands as shown in Equation 20 below.

는

의 정수배를 더하거나 빼서

사이의 값으로 변환된 값으로서, 상기

는 0부터 (

-1) 이하의 값을 갖는 실수 s 범위에서 신호열의 길이이고, 상기

는 0부터 (

-1) 이하의 값을 갖는 실수 s 범위에서

범위의 값이다.From here,

Is

By adding or subtracting an integer multiple of

A value converted to a value between

From 0 (

-1) the length of the signal sequence in the real s range having a value less than or equal to

From 0 (

-1) in real s range with a value less than or equal to

The value of the range.

항은 상기

가 짝수인 경우,

=

이고, 상기

가 홀수인 경우,

=

에 의해 산출된다.In addition,

Term above

Is an even number,

=

And above

Is an odd number,

=

Calculated by

를 이용하여 상기 수학식 16의 네번째 항을 다음의 수학식 21과 같이 계산한다.Equation 20 calculated through the above process

The fourth term of Equation 16 is calculated using Equation 21 as follows.

Using Equation 17 to Equation 21, a fourth term of Equation 16 can be obtained, and an upsampled sample sequence on the time axis of the preamble symbol can be obtained using the equation.

As in the case of FIG. 16, an example of generating a 16-fold up-sampled baseband preamble signal sequence by applying Q = 16 is illustrated in FIG. 17.

17 is a graph of a 16-fold up-sampled preamble signal sequence using an inverse Fourier transform operation in accordance with the present invention.

In FIG. 17, it can be seen that the up-sampled signal is present along the unit circle, so that there is no change in signal size during transmission.

FIG. 18 is a flowchart illustrating a subsequent operation after step S500 of the method of generating a preamble signal shown in FIG. 4.

Referring to Figures 1 to 18 will be described in detail the process of the preamble signal generation method of underwater ultra-wideband communication of the present invention.

The baseband signal generator 100 receives information data to be transmitted from the outside and maps the received data to a symbol signal so that the received data can be transmitted in each subcarrier of orthogonal frequency division multiple modulation in a predetermined order.

The mapped symbol signal is converted into data in the time domain using an inverse Fourier transform, and N-fold up-sampling is performed.

At this time, N-fold up-sampling may be performed on the frequency axis or the time axis.

When performing on the frequency axis, add (N-1) times the subcarriers in the high frequency band on the frequency axis, set '0' to the added subcarriers, and perform inverse Fourier transform operation to perform N times and sampled signal sequence. Create

On the other hand, when N-fold up-sampling is performed on the time axis, an inverse Fourier transform operation is performed by using a signal of a subcarrier, and (N-1) sampling time points are added between samples in the result, and the added Set '0' at sampling time point and perform N-times and sampled signal sequence by performing interpolation filtering.

길이의 차도프 추 신호열을 Q*

개의 부반송파를 갖는 직교 주파수 분할 다중 변조에서 DC에서 q(0<= q < Q, q는 정수)개의 부반송파 오프셋을 설정하고 Q개의 등간격으로 상기의 미리 정해진 차도프 추 신호열을 배치한다.The preamble signal generator 200 is predetermined

Q * of the length of the Chadov weight signal sequence

In orthogonal frequency division multiplexing with 10 subcarriers, q (0 < = q < Q, q is an integer) subcarrier offsets are set in DC, and the predetermined differential doped weight signal sequences are arranged at Q equal intervals.

Then, its inverse Fourier transform is performed to convert it to data in the time domain.

In this case, an operation that obtains the same result is performed without actually performing the inverse Fourier transform by using the characteristics of the preamble signal that performs the Inverse Fourier transform.

Then, after obtaining a signal corresponding to an inverse Fourier transform, N-fold up-sampling is performed by setting it to change along a single circle in constellation.

The transmission signal multiplexing unit 300 transmits a sample string of the preamble signal, which is an output of the preamble signal generation unit 200, to the transmitter 400 in the preamble symbol period according to the signal frame structure, and the baseband signal in the subsequent data symbol period. The sample string of the generator 100 is output to the transmitter 400.

The transmitter 400 transmits a signal by modulating a sample string received from the transmission signal multiplexing unit 300 into a carrier frequency band.

In this case, the transmitter 400 may additionally perform up-sampling on the received sample string.

The receiver 500 receives a signal transmitted from the transmitter 400, performs sampling at a predetermined multiple per symbol, and outputs the signal.

The demixing unit 600 receives a sampled signal at a predetermined multiple per symbol and performs a frequency shift that lowers the frequency by the carrier frequency.

The low pass filter receives a frequency shift signal from the demixing unit 600 and passes only a signal corresponding to the baseband signal and performs low pass filtering to remove signal components corresponding to the harmonic component.

The correlation value calculator 800 calculates a correlation value between the conjugate complex number of the preamble signal sequence and the output of the low pass filter 700.

The correlation value calculation result can be used to detect the start of the signal frame and to estimate the Doppler shift.

The received signal processor 900 receives the correlation value calculated by the correlation value calculator 800 to calculate the energy to detect the start of the signal frame.

In addition, the output of the low pass filter 700 corresponding to the detected frame signal is compensated for Doppler shift, symbol time shift, frequency shift, phase shift, and the like, and further received signal processing is performed to determine the transmitted information. Output

As shown in FIG. 2 and FIG. 9, the one periodic signal storage unit 210 applies the preamble generation parameter q and the subcarrier number M and sets up-sampling multiple N according to the implemented system. This function saves the result of calculating the multiplication of the third and fourth terms of 16, and outputs the stored results sequentially.

That is, the signal sequence stored in one periodic signal storage unit 210 is the first of the signal repeated in the inverse pre-converted signal of the N-fold up-sampled circular shifted Zadoff weight signal and the preamble signal determined by the preamble generation parameter. The signal sequence to which the phase shift occurring in the period corresponding to the period is applied.

Here, the inverse pre-transformed signal of the N-fold up-sampled shifted Zadoff weights signal is subjected to an inverse Fourier transform of the circularly shifted Zadoff weights signal and then along a circle having a constant magnitude in the signal constellation. The same calculation results as those calculated by N-fold up-sampling to change the signal are obtained, but the circularly shifted Jadopuchu signal without the inverse-Fourier transform and the N-fold up-sampling method described with reference to FIG. Calculate using

The phase shifting and scaling storage unit 220 corresponds to a period of one period signal storage unit 210, and r is 0 to Q for the remaining terms required to generate the N-fold up-sampled preamble signal sequence of Equation 16 above. Save the result calculated according to r value until -1).

In addition, one value is output when the signal of the one period signal storage unit 210 progresses by one period in synchronization with the signal output period of the one period signal storage unit 210, and the output value is output to the memory buffer 230. Save it.

The complex multiplier 240 receives a value stored in the memory buffer 230 and an output signal of the one period signal storage 210 to perform complex multiplication to output a preamble sample.

That is, the signal stored in one periodic signal storage unit 210 is repeatedly outputted Q times, and in synchronization with this, the value stored in the phase shift and scaling storage unit 220 per cycle is output to the memory buffer 230 once, The preamp sample string is generated by multiplying the value of the memory buffer 230 by the output of the periodic signal storage 210.

One periodic signal stored in one periodic signal storage unit 210 shown in FIG. 2 is generated through the same procedure as that of FIG. 8.

과 부반송파에 할당하는

길이의 새로운 신호열 및 부반송파에 Q개 간격으로 새로운 신호열을 할당함에 있어 DC에서 q개 만큼의 부반송파 오프셋은 미리 정해져 있으며, N배 업-샘플링한다고 가정한다. To generate one periodic signal, the number of subcarriers, M = Q *

Assigned to and subcarriers

In allocating a new signal sequence of length Q to a new signal sequence and subcarriers, it is assumed that q subcarrier offsets from DC are predetermined and up-sampled by N times.

및

를 계산한다(S410).First, equations (17) and (18) are applied to calculate the inverse Fourier transform of the new signal sequence.

And

To calculate (S410).

의 값이 홀수인지 여부를 판단하여(S420),

의 값이 홀수인 경우 수학식 20에 따라

를 계산한 후에(S430)

를 계산한다(S440).

Determine whether the value of is odd (S420),

If the value of is odd according to equation (20)

After calculating (S430)

To calculate (S440).

의 값이 홀수가 아닌 경우

를 대입하여

를 계산한다(S435).if,

Is not an odd number

By substituting

To calculate (S435).

사이로 한정하도록 변환하는

를 수학식 20과 같이 계산한다(S450).Next, the range of phase values for the inverse Fourier transform

To constrain to

It is calculated as in Equation 20 (S450).

를 계산하고(S460), 계산한 결과를

과 곱한다(S470). Using Equation 21

To calculate (S460), the calculated result

Multiply by (S470).

-1/N)까지의 범위를 갖는 값이 되며, 한 주기 신호 저장부(210)에 저장된 한 주기 신호의 샘플길이는 N*

개가 된다.Where s is 0 to 1 / N intervals (assuming that N times up-sampling)

-1 / N), and the sample length of one period signal stored in one period signal storage 210 is N *.

It becomes a dog.

19 is a graph showing a result of calculating a correlation value between a received signal and a preamble signal when there is 1% normalized Doppler shift.

20 is a graph of the result of measuring the peak value change of the correlation value according to the normalized Doppler shift.

As shown in FIG. 20, it can be seen that there are nine points having peak values, which means that there are eight repeated structures (Q = 8) present in the preamble symbol interval and one cycle repeated in the cyclic prefix. Nine peak values are observed.

When the normalized Doppler shift varies between -1% and 1%, the peak value of the correlation value is calculated, and the modeled symbol structure has a value of about 5800 to 8100, and shows the point where the peak value exists and the point does not exist. It can be clearly distinguished.

That is, even when there is a relatively large normalized Doppler shift, the preamble symbol sequence generated in this embodiment can be easily detected by the receiver 500.

As shown in FIG. 20, when the normalized Doppler shift varies from -1% to 1%, the peak value of the correlation value measured through computer simulation of the maximum value of the correlation value between the received signal and the preamble signal is the preamble symbol. It is of sufficient size to detect the presence of.

As described above, the method of generating a preamble signal of the underwater ultra-wideband communication according to the present invention allocates a symbol string to a subcarrier at regular intervals in an ultra-wideband communication system using an orthogonal frequency division multiple modulation in which Doppler shift occurs larger than subcarrier spacing. By converting a signal into a signal in a time domain and repeating it in one symbol, a method for generating a preamble signal for underwater ultra-wideband communication capable of accurately detecting a preamble symbol at a receiving node even when a Doppler shift occurs is provided.

In this case, when orthogonal frequency division multiplexing is used, even when a Doppler shift occurs larger than the subcarrier spacing due to the relative movement of the transmitting node and the receiving node, the data of the received signal is obtained through additional signal processing after detecting the preamble symbol. Can be restored accurately.

In addition, in the orthogonal frequency division multiple modulation, a subcarrier corresponding to a DC frequency can be excluded without any limitation in assigning a symbol string to a subcarrier, and thus it can be easily used in an orthogonal frequency division multiple modulation method that does not transmit DC frequency components. Will be.

While various embodiments of the present invention have been described with reference to some examples, the descriptions of the various embodiments described in the "Specific Embodiments of the Invention" section are merely illustrative, and the present invention has been described. Those skilled in the art will understand from the above description that the present invention can be variously modified or implemented in accordance with the present invention.

In addition, the present invention is not limited by the above description because it can be implemented in a variety of other forms, the above description is intended to complete the disclosure of the present invention is usually in the technical field to which the present invention belongs It should be understood that the present invention is provided only to fully convey the scope of the present invention to those skilled in the art, and the present invention is defined only by the claims of the claims.

100: baseband signal generator
200: preamble signal generation unit
300: transmission signal multiplexing unit
400: transmitter
500: receiver
600: demixing unit
700: low pass filter
800: correlation value calculation unit
900: reception signal processing unit

Claims (19)

(a) a baseband signal generation unit receiving information data from an external source and mapping the data into an orthogonal frequency division multiple modulation symbol signal, and outputting an N-fold up-sampled baseband signal by inverse Fourier transforming the mapped symbols ;
(b) a preamble signal generator sets a subcarrier offset in the orthogonal frequency division multiplexing modulation, arranges a signal string having a predetermined length at equal intervals, and then inversely transforms the arranged signal sequence to an N-fold up-sampled preamble signal. Generating a corresponding symbol string;
(c) multiplexing and outputting a sample string of the baseband signal or a sample string of the preamble signal according to a signal frame structure by a transmission signal multiplexing unit; And
(d) a transmitter receiving the multiplexed sample string and modulating the carrier frequency band in a carrier frequency band;
Including,
Step (b)
(b-1) A periodic signal storage unit sets the up-sampling multiple N in consideration of the preamble generation parameter and the number of subcarriers, and the repetition determined by the generation parameter in calculating the N-fold up-sampled preamble signal. Storing a result of calculating a signal corresponding to a first period of the signal repeated a number of times; And
(b-2) calculating and storing a value to be multiplied by a signal output stored in the one periodic signal storage unit to generate a symbol string corresponding to the N-fold up-sampled preamble signal by a phase shifting and scaling storage unit; ;
Including;
Step (b-2)
The value to be multiplied is calculated and stored when a signal stored in the one periodic signal storage unit is repeated for a repetition number determined according to the preamble generation parameter and the number of subcarriers to generate the N-fold up-sampled preamble signal. Characterized by
Preamble signal generation method for underwater ultra-wideband communication.
The method of claim 1,
Step (a) is
(a-1) mapping the symbol signal transmitted in each subcarrier of orthogonal frequency division multiple modulation from information received from the outside;
(a-2) mapping the mapped symbol signal to each subcarrier of the orthogonal frequency division multiple modulation in a predetermined order;
(a-3) determining a method of performing N-fold up-sampling;
(a-4) when the N-fold up-sampling method is to perform the up-sampling in the frequency domain,
Adding (N-1) times the subcarriers in the high frequency band; And
And setting an '0' to the added subcarrier and performing an inverse Fourier transform operation.
(a-5) when the N-fold up-sampling method is to perform the up-sampling in a time domain,
Performing an inverse Fourier transform operation having a size as large as a subcarrier;
Adding (N-1) sampling time points between samples in the inverse Fourier transform result; And
And setting '0' at the added sampling time point and performing interpolation filtering to generate N times and a sampled signal sequence.
(a-6) outputting a signal generated by the N-fold up-sampling method;
Characterized in that it comprises a,
Preamble signal generation method for underwater ultra-wideband communication.
The method of claim 1,
Step (b)
(b-3) storing the output value when the memory buffer advances one cycle in synchronization with the output signal cycle of the one cycle signal storage unit; And
(b-4) a complex multiplication unit receiving the output signal of the one periodic signal storage unit and a value stored in the memory buffer and performing a complex multiplication to output the preamble signal;
Characterized in that it further comprises,
Preamble signal generation method for underwater ultra-wideband communication.

The method of claim 3,
In the step (b-1)
The calculation of the signal corresponding to the first period is
(b-1-1) calculating an inverse Fourier transformed signal of the N-fold up-sampled circular shifted Zadoff weight signal;
(b-1-2) calculating a phase shift occurring in a section corresponding to a first period of a signal repeated in the preamble signal determined by the preamble generation parameter; And
(b-1-3) Store the one periodic signal by rotating the inverse Fourier transform signal calculated in the step (b-1-1) by the phase shift calculated in the step (b-1-2). Storing in wealth;
Characterized in that it comprises a,
Preamble signal generation method for underwater ultra-wideband communication.
The method of claim 4, wherein
In the step (b-1-1)
The inverse Fourier transformed signal
Characterized in that it is calculated using a formula expressing a circularly shifted Zadoff weight signal sequence corresponding to an inverse-Fourier transform of the circularly shifted Jadofu weight signal,
Preamble signal generation method for underwater ultra-wideband communication.
The method of claim 3,
Step (b-2)
The one periodic signal storage unit has a signal magnitude that must be multiplied for one period for generating a preamble signal while outputting the signal for one stored period, and a value obtained by applying a phase change amount in each period by the preamble generation parameter. Characterized by having,
Preamble signal generation method for underwater ultra-wideband communication.
The method of claim 1,
Step (c) is
(c-1) outputting a sample string of the preamble signal in a preamble symbol period; And
(c-2) outputting a sample string of the baseband signal generator in a data symbol period after the preamble symbol period;
Characterized in that it comprises a,
Preamble signal generation method for underwater ultra-wideband communication.
The method of claim 1,
The preamble signal generation method
After step (d)
Receiving, by a receiver, the signal output from the transmitter, sampling and outputting the signal at a predetermined multiple per symbol;
Performing a frequency shift to reduce a frequency by a carrier frequency by receiving the sampled signal by a demixing unit;
A low pass filter receiving the frequency shifted signal and passing only a signal corresponding to the baseband signal and removing a signal component corresponding to a harmonic component;
A correlation value calculating unit receiving an output of the low pass filter to calculate a correlation value with a conjugate complex number of a preamble signal sequence already known; And
Receiving, by the received signal processor, the calculated correlation value to calculate energy to detect the start of a signal frame;
Characterized in that it further comprises,
Preamble signal generation method for underwater ultra-wideband communication.
The method of claim 8,
The received signal processing unit
Receiving the calculated correlation value to compensate for Doppler shift, symbol time shift, frequency shift, and phase shift using the output of the low pass filter,
Preamble signal generation method for underwater ultra-wideband communication.
The method of claim 1,
The sample string on the time axis of the preamble signal is
Without inverse Fourier transform
First equation

Generated by
M is the number of subcarriers, M = Q *

There is a relationship between

Is the size of the Zadoffchu symbol string, and q is the

When assigning the length of the symbol string to subcarriers uniformly separated by Q, it is an offset value in DC, and n is a sampling time.

R is an integer of 0 to (Q-1) or less, and s is 0 to (

-1) characterized in that the real number having the following values,
Preamble signal generation method for underwater ultra-wideband communication.
The method of claim 10,
In the first equation

Term
Second equation

Which is calculated by
Preamble signal generation method for underwater ultra-wideband communication.
The method of claim 11,
In the second equation

Term
Third equation

Calculated by
remind

From 0 (

-1) the length of the signal sequence in the real s range having a value less than or equal to

From 0 (

-1) in real s range with a value less than or equal to

Characterized in that the value of the range
Preamble signal generation method for underwater ultra-wideband communication.
The method of claim 12,
In the third equation

Term
remind

Is an even number,

=

ego,
remind

Is an odd number,

=

Calculated by
remind

Is
Fourth Equation

ego,
remind

Term
5th equation

Is,

remind

Term
6th equation

ego,
S from 0 (

-1) is a real number with a value less than or equal to

Is the length of the signal string,

R is a value shifted circularly with respect to the Zadoff weight signal sequence when generating the signal sequence.

Characterized by the user as one of the integers up to -1),
Preamble signal generation method for underwater ultra-wideband communication.
The method of claim 13
R above

Using to generate a sample string of the preamble signal
Preamble Signal Generation Method for Underwater Ultra-Wideband Communication
The method of claim 12,
The sample string of the preamble signal is
Characterized in that Zadoff-Chu complex symbol string,
Preamble signal generation method for underwater ultra-wideband communication.
(a) a baseband signal generation unit receiving information data from an external source and mapping the data into an orthogonal frequency division multiple modulation symbol signal, and outputting an N-fold up-sampled baseband signal by inverse Fourier transforming the mapped symbols ;
(b) a preamble signal generator sets a subcarrier offset in the orthogonal frequency division multiplexing modulation, arranges a signal string having a predetermined length at equal intervals, and then inversely transforms the arranged signal sequence to an N-fold up-sampled preamble signal. Generating a corresponding symbol string;
(c) multiplexing and outputting a sample string of the baseband signal or a sample string of the preamble signal according to a signal frame structure by a transmission signal multiplexing unit; And
(d) a transmitting unit receiving and transmitting the multiplexed sample string;
Step (b)
(b-1) A periodic signal storage unit sets the up-sampling multiple N in consideration of the preamble generation parameter and the number of subcarriers, and the repetition determined by the generation parameter in calculating the N-fold up-sampled preamble signal. Storing a result of calculating a signal corresponding to a first period of the signal repeated a number of times; And
(b-2) calculating and storing a value to be multiplied by a signal output stored in the one periodic signal storage unit to generate a symbol string corresponding to the N-fold up-sampled preamble signal by a phase shifting and scaling storage unit; ;
Including;
Step (b-2)
A value to be multiplied is calculated and stored when a signal stored in the one periodic signal storage unit is repeated for a repetition number determined according to the preamble generation parameter and the number of subcarriers to generate the N-fold up-sampled preamble signal,
The generated preamble signal is characterized in that the modulated to have a characteristic of the chirp (Chirp) signal,
Preamble signal generation method for underwater ultra-wideband communication.
A baseband signal generation unit which receives information data from an external source and maps it to a symbol signal of orthogonal frequency division multiple modulation, and outputs an N-fold up-sampled baseband signal by inverse Fourier transforming the mapped symbols;
After setting the subcarrier offset in the orthogonal frequency division multiplexing modulation and arranging a signal string having a predetermined length at equal intervals, the arranged signal sequence is inverse Fourier transformed to generate a symbol sequence corresponding to an N-fold up-sampled preamble signal. A preamble signal generator;
A transmission signal multiplexing unit multiplexing a sample string of the baseband signal or a sample string of the preamble signal according to a signal frame structure; And
A transmitter which receives the multiplexed sample string and modulates the carrier frequency band and transmits the received frequency;
And
The preamble signal generator
A periodic signal storage unit configured to set the up-sampling multiple N in consideration of a preamble generation parameter and the number of subcarriers, and to store a result of calculating a part of the preamble signal; And
A phase shift and scaling storage unit for storing a result of calculating the remaining term of the preamble signal;
Equipped with,
The value to be multiplied is calculated and stored when a signal stored in the one periodic signal storage unit is repeated for a repetition number determined according to the preamble generation parameter and the number of subcarriers to generate the N-fold up-sampled preamble signal. Characterized by
Preamble signal generation device for underwater ultra-wideband communication.
The method of claim 17,
The preamble signal generator
A memory buffer configured to store a value output when the cycle progresses by one period in synchronization with an output signal period of the one period signal storage unit; And
A complex multiplier configured to perform complex multiplication by receiving an output signal of the one periodic signal storage unit and a value stored in the memory buffer to output the preamble signal;
Characterized in that further comprising,
Preamble signal generation device for underwater ultra-wideband communication.
The method of claim 17,
A receiver which receives the signal output from the transmitter and performs sampling at a predetermined multiple per symbol and outputs the sampling;
A demixing unit which receives the sampled signal and performs a frequency shift to lower the frequency by a carrier frequency;
A low pass filter receiving the frequency shifted signal and passing only a signal corresponding to the baseband signal and removing a signal component corresponding to a harmonic component;
A correlation value calculation unit receiving the output of the low pass filter and calculating a correlation value with a conjugate complex number of a preamble signal sequence already known; And
A received signal processor configured to receive the calculated correlation value and calculate energy to detect a start of a signal frame;
Characterized in that it further comprises,
Preamble signal generation device for underwater ultra-wideband communication.

Images