KR102043830B1 - Underwater laser communication apparatus and the communication method using thereof - Google Patents

Abstract

According to one embodiment of the present invention, provided is an underwater laser communication method, which is an underwater laser communication method using binary data including the most significant bit and a lower significant bit. The underwater laser communication method comprises the following steps: receiving a laser signal including a pulse from an external communication device; acquiring the lower significant bit based on position information of a pulse in a symbol which is a time section of the laser signal; and acquiring the most significant bit based on an inclination code of the pulse in the symbol.

Description

Underwater laser communication device and communication method using same {UNDERWATER LASER COMMUNICATION APPARATUS AND THE COMMUNICATION METHOD USING THEREOF}

The present invention disclosed by the present application relates to an underwater laser communication apparatus and an underwater laser communication method using the same, and more particularly, to an underwater laser communication apparatus using the slope and position information of the pulse and an underwater laser communication method using the same.

Underwater wireless communication networks have been developed and are commercially available because acoustic attenuation is relatively small compared to the air. Underwater acoustic channels, however, have limited bandwidth and are not suitable for data-intensive applications. In addition, slow propagation of underwater sound also introduces significant delay in the underwater communication link.

Thus, a new approach, which is the area of research that is most noticed to overcome the shortcomings of underwater acoustics, is underwater wireless optical communication. Recently, underwater wireless optical communication using LD (Laser Diode) as well as inexpensive LED (Light Emitting Diode) has been studied. In particular, LDs can outperform LED performance in terms of data rate. Even though long-range transmission is difficult with LD, the point-to-point method, which takes advantage of the strong directivity of the laser, can be used to solve the problem between symbol and eavesdropping security related to multipath propagation. have.

As an underwater wireless laser communication method, an IM / DD (Intensity Modulation / Direct Detection) method, which is easy to implement and has an advantage of low cost, has been widely applied. The IM / DD method is representative of On-Off Keying (OOK) and Pulse Position Modulation (PPM).

The on-off keying method is easy to implement but weak in noise, and has a disadvantage of having to set an appropriate threshold for distinguishing symbols between “0” and “1” and depending on turbidity. This causes increased errors due to multiple scattering effects in coastal waters with high turbidity. The pulse position modulation method divides one symbol section into several sections and loads information on the position of the pulse, which is more power efficient than the on-off keying method and does not require a threshold. There is a problem that the discrimination performance is reduced.

An object according to an embodiment is to provide an underwater laser communication device and a communication method using the same, in addition to the position information of the pulse in the symbol, and transmits the bit information in the laser signal by using the gradient information of the pulse.

Another object of the present invention is to provide an underwater laser communication device for obtaining bit information contained in a received laser signal and a communication method using the same, based on the slope information of the pulse and the position information of the pulse.

The problem to be solved is not limited to the above-described problem, and the problems that are not mentioned will be clearly understood by those skilled in the art from the present specification and the accompanying drawings.

The underwater laser communication method according to an embodiment of the present invention is a method of underwater laser communication using binary data including a most significant bit and a lower bit, the method comprising: receiving a laser signal including a pulse from an external communication device; The method may include obtaining a lower bit based on position information of a pulse in a symbol, and obtaining a most significant bit based on a slope code of a pulse in the symbol.

In addition, the most significant bit may be obtained based on a cumulative value of a pulse signal value sampled at a plurality of sampling time points constituting a symbol.

In addition, the symbol may include a first section including a pulse, which is determined according to the position information of the pulse, and the plurality of sampling time points may be located in the first section.

The most significant bit is the first equation

In this case, the MSB may be the most significant bit, N may be a sampling number for the pulse signal value, and r (t _n ) may be a pulse signal value.

Further, the lower bit may be obtained based on a chip time point at which the cumulative value of the laser signal values sampled at the plurality of chip time points constituting the symbol becomes maximum.

According to another embodiment, an underwater laser communication method using binary data including a most significant bit and a least significant bit, wherein a symbol is a time interval of a laser signal and pulses according to a slope sign of a pulse in a symbol determined based on the most significant bit. Generating a; Modulating the position of the pulse in accordance with the position information of the pulse in the symbol determined based on the lower bit; And transmitting the laser signal including the pulse to an external communication device.

In addition, the underwater laser communication method, the second equation

에 따라 레이저 신호를 생성하는 단계를 더 포함하고, t는 시간, T_S는 심볼의 길이, L은 심볼을 구성하는 칩 시점의 개수, m은 1부터 L까지의 정수일 수 있다.

The method may further include generating a laser signal, wherein t may be a time, T _S may be a length of a symbol, L may be a number of chip views constituting the symbol, and m may be an integer from 1 to L.

According to yet another embodiment, a computer-readable recording medium for storing a computer program for performing the underwater laser communication method may be provided.

According to another embodiment, an underwater laser communication device is an underwater laser communication device using binary data including a most significant bit and a lower bit, the laser communication unit and a laser signal for receiving a laser signal including a pulse from an external communication device The controller may include a control unit that obtains a lower bit based on position information of a pulse in a symbol that is a time interval and obtains a most significant bit based on a slope code of a pulse in a symbol.

According to another embodiment, an underwater laser communication apparatus using binary data including a most significant bit and a lower bit, comprising: a pulse generator for generating a pulse according to a slope code of a pulse in a symbol determined based on the most significant bit And a pulse position modulator for modulating the position of the pulse according to the position information of the pulse in the symbol determined based on the bit, and a laser communicator transmitting the laser signal including the pulse to an external communication device.

The underwater laser communication method according to an embodiment may transmit one bit information according to the type of slope by using a pulse having a slope and a position modulated signal for wireless laser communication having a high transmission rate in an underwater channel. If the lengths are the same, the transmission rate is higher than that of the conventional method and the power efficiency is improved.

The underwater laser communication method according to another embodiment obtains bits in a symbol based on a plurality of signal values sampled in a symbol and a cumulative value of the signal values at a receiving end, so that the calculation amount is small and the structure is simple.

Effects are not limited to the above-described effects, and effects that are not mentioned will be clearly understood by those skilled in the art from the present specification and the accompanying drawings.

1 is a view of the configuration of the underwater laser communication system according to an embodiment.
2 is a block diagram of an underwater laser communication apparatus according to an embodiment.
3 is a diagram of a method of generating a laser signal including a pulse by an underwater laser communication apparatus according to one embodiment.
4 is a flowchart illustrating an operating method of the underwater laser communication device of FIG. 3.
5 is a diagram of a signal according to a conventional pulse position modulation scheme.
FIG. 6 is a diagram of a signal of an underwater laser communication method using SL-PPM, according to an exemplary embodiment.
7 is a flowchart of a method of acquiring a bit by receiving a laser signal including a pulse by an underwater laser communication apparatus according to another exemplary embodiment.
8 is a diagram illustrating acquiring a most significant bit based on an accumulated value of a pulse signal value sampled at a plurality of sampling time points in a symbol in the underwater laser communication method according to an exemplary embodiment.
9 to 11 are views illustrating a water tank experimental apparatus using the underwater laser communication method according to an embodiment.
12 is a diagram comparing bit error rates between the underwater laser communication method measured by the tank experimental apparatus and the conventional OOK method.

With reference to the drawings will be described in detail a specific embodiment of the present invention. However, the spirit of the present invention is not limited to the embodiments presented, and those skilled in the art who understand the spirit of the present invention may deteriorate other inventions or the present invention by adding, modifying, or deleting other elements within the scope of the same idea. Other embodiments that fall within the scope of the inventive concept may be readily proposed, but they will also be included within the scope of the inventive concept.

In addition, the components with the same functions within the scope of the same idea shown in the drawings of each embodiment will be described using the same reference numerals.

The terminology used in the embodiments was selected as widely used as possible terms in consideration of functions in the present invention, but may vary according to the intention or precedent of a person skilled in the art, the emergence of new technologies, and the like. In addition, in certain cases, there is also a term arbitrarily selected by the applicant, in which case the meaning will be described in detail in the description of the invention. Therefore, the terms used in the present invention should be defined based on the meanings of the terms and the contents throughout the present invention, rather than the names of the simple terms.

When any part of the specification is to "include" any component, this means that it may further include other components, except to exclude other components unless otherwise stated. In addition, the terms "?", "?" Module, etc. described in the specification mean a unit for processing at least one function or operation, which may be implemented in hardware or software, or a combination of hardware and software.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

1 is a diagram illustrating a configuration of an underwater laser communication system according to an embodiment, and FIG. 2 is a block diagram of an underwater laser communication apparatus according to an embodiment.

The first underwater laser communication device 100 and the second underwater laser communication device 200 may transmit and receive data through a communication network underwater. The first underwater laser communication device 100 and the second underwater laser communication device 200 may communicate by mapping bit information using the gradient information of the pulse and the position information of the pulse.

The underwater laser communication device 100 may include a laser communication unit 120 and a control unit 140.

The laser communication unit 120 is an optical system using a laser diode LD, and may transmit a laser signal generated by the controller 140, or may receive a laser signal from an external communication device and convert the laser signal into an electrical signal, and then control the controller 140. ) Can be delivered.

Laser diodes can use lasers of various wavelengths and colors. For example, laser diodes can generate and receive cyan lasers. At short distances, the blue-green laser exhibits minimal energy fading at sea, with a fading rate of about 0.155 to 0.5 dB / m. Thus, underwater wireless laser communications using low absorption windows of sea water in the turquoise portion of the electromagnetic spectrum can provide secure, efficient and high data rate communications over short distances. Of course, the laser used by the laser diode is not limited to cyan, and lasers of various wavelengths suitable for the underwater environment may be used.

The controller 140 may include a pulse generator 142 and a pulse position modulator 144. The pulse generator 142 and the pulse position modulator 144 are logical and conceptual units classified functionally to perform the underwater laser communication method step by step on a computer program, and the pulse generator 142 and the pulse are necessarily. The position modulators 144 need not be physically distinct from each other. For example, the pulse generator 142 and the pulse position modulator 144 may be executed through the same processor or may be executed through separate processors.

The matters described with respect to the controller 140 throughout the specification may be performed by any one of the configuration of the pulse generator 142 and the pulse position modulator 144. However, the controller 140 is not limited to the pulse generator 142 and the pulse position modulator 144, but may further include other components. It may be performed by other configurations. In addition, the controller 140 may include only a part of the pulse generator 142 and the pulse position modulator 144.

The pulse generator 142 may be a device or a circuit that generates a voltage or current pulse of a desired waveform. The pulse generator 142 may generate a pulse reflecting the bits of the digital input signal according to the digital input signal including the input most significant bit and other lower bits. The pulse generator 142 may be configured to discharge, for example, energy charged in a microwave pulser, a capacitor, or the like to modulate a microwave carrier through a saturable reactor or an electron tube, or after resonantly charging a pulse forming line from a power source, a discharge tube switch, It may include a configuration for outputting through a pulse transformer, and the like, but is not limited to the above-described example.

The waveform including the pulse generated by the pulse generator 142 may be transferred to the laser communicator 120 to generate a laser according to the pulse.

The pulse position modulator 144 may modulate a position on the time axis of the pulse according to the digital input signal with respect to the generated pulse. The pulse position modulator 144 selects at least several times the highest frequency included in the communication content to which the repetitive frequency is transmitted by using a short pulse of a constant amplitude, and modulates the pulse generation position according to the change in the signal amplitude. This is a type of pulse time modulation.

When the control unit 140 receives a laser signal including a pulse through the laser communication unit 120, the control unit 140 may read an electronic signal corresponding to the laser signal to acquire, determine, or determine the most significant bit and other lower bits from the pulse. Can be.

The controller 140 divides the electronic signal corresponding to the laser signal including the received pulse according to the symbol section, obtains the pulse position information by identifying the position of the pulse in each symbol section, and in each symbol section. The slope of the pulse may be determined to obtain information such as a pulse slope code. The controller 140 may thereby obtain bits and information included in the carrier. The controller 140 may perform a related operation for this purpose, which will be described later in more detail.

3 is a diagram illustrating a method of generating a laser signal including a pulse by an underwater laser communication apparatus according to an exemplary embodiment, and FIG. 4 is a flowchart illustrating a method of operating the underwater laser communication apparatus 100 of FIG. 3.

The underwater laser communication apparatus 100 may determine the gradient code of the pulse in the symbol and generate the pulse based on the most significant bit (S1100).

A symbol is one operation unit processed for digital communication, and operations such as modulation, coding, transmission, and detection may be performed for each symbol. For example, the symbol may be a time interval constituting a laser signal including a digital input signal or a pulse.

이고, 1인 경우에 기울기는

가 된다. The underwater laser communication apparatus 100 may first determine a sign of a slope according to a ₀ value, which is a most significant bit (MSB) of M bits constituting one symbol. For example, as shown in FIG. 6, when one symbol is composed of two bits, and the time corresponding to one symbol length is T _s and the amplitude is A, one of the most significant bits is 0. The slope in the pulse interval is

If is 1, the slope is

Becomes

Thereafter, the underwater laser communication apparatus 100 may determine the position information of the pulse in the symbol and the pulse position modulator 144 based on the lower bits (S1200).

When the sign of the slope of the pulse is determined, the underwater laser communication apparatus 100 may determine the position information of the pulse through the pulse position modulator 144 using the lower bits, which are the remaining bits except the most significant bit. In the case where the lower bit is 0, the pulse position may be modulated so that the pulse is formed in the front section, and in the case where the lower bit is 1, the pulse is formed in the rear section. Therefore, the waveform of the modulated pulse is shown in Equation 1.

Here, t is time, T _S is the length of the symbol, L is the number of chip views constituting the symbol, and m is an integer from 1 to L.

The underwater laser communication apparatus 100 may transmit a laser signal including a pulse to an external communication device (S1300). The first underwater laser communication device 100 may be transmitted to the second underwater laser communication device 200 through the laser communication unit 120 through the laser communication unit 120 according to the waveform of the generated pulse. The second underwater laser communication device 200 may receive the laser signal through the laser communication unit 120 and determine the most significant bit and the least significant bit.

FIG. 5 is a diagram of a signal according to a conventional pulse position modulation scheme, and FIG. 6 is a diagram of a signal according to the underwater laser communication method using the SL-PPM.

Referring to FIG. 5, the conventional PPM method uses only pulse position information and does not use slope of a pulse. Therefore, the conventional PPM method uses a rectangular pulse. Accordingly, one symbol may include only one bit that is determined depending on whether the pulse is in the front section of the symbol or whether the pulse is in the back section of the symbol.

6, the underwater laser communication method using the SL-PPM uses a pulse having a slope. According to this, it is superior to the conventional method in terms of bandwidth efficiency. By using the slope and position modulated signals in the underwater channel, one bit of information can be transmitted further depending on the type of slope, thereby increasing the length of the pulse interval. When the conventional PPM technique can transmit log2M bits per symbol, the underwater laser communication method using SL-PPM can transmit log2M + 1 bits per symbol. M is the number of chips per symbol. Thus, according to the underwater laser communication method using the SL-PPM, the size of the data packet is smaller, so that the data rate and bandwidth efficiency are increased.

6 shows an example of two bits in one symbol. The MSB value is determined by the slope of the pulse and the second bit value is determined by the position of the pulse. As shown in Figure 1, if there is a pulse in the front of the symbol, it consists of "0", and if there is a pulse in the back, it becomes "1".

7 is a flowchart illustrating a method of acquiring a bit by receiving a laser signal including a pulse by an underwater laser communication apparatus according to another exemplary embodiment. Referring to FIG. 7, the underwater laser communication device 100 may receive a laser signal including a pulse from an external communication device (S2100). The first underwater laser communication device 100 may receive a laser signal from the second underwater laser communication device 200 through the laser communication unit 120, and transmit an electrical signal corresponding thereto to the controller 140.

The underwater laser communication apparatus 100 may process an electrical signal corresponding to a laser signal and acquire a lower bit based on position information of a pulse in a symbol (S2200). The lower bit may be obtained based on the chip time point at which the cumulative value of the laser signal values sampled at the plurality of chip time points constituting the symbol is maximum.

As a specific example, the controller 140 obtains position information of a pulse by using a plurality of chip viewpoints. When the signal received in one symbol period is r (t), the controller 140 obtains an accumulation value of a signal received in each chip at an interval of T _s / L which is a chip duration. The controller 140 determines the lower bits based on the section representing the largest cumulative value. The controller 140 determines that a pulse is formed until the chip time point at which the cumulative value is maximum, and determines that the pulse is not included at the chip time point at which the cumulative value decreases. Thus, the controller 140 may determine the position information of the pulse and obtain the lower bit.

The underwater laser communication apparatus 100 may obtain the most significant bit based on the slope code of the pulse in the symbol (S2300). The slope code may be obtained based on the accumulated value of the pulse signal values sampled at the plurality of sampling time points.

In this case, the chip time point for determining the lower bit and the sampling time point for determining the most significant bit may be different from each other, or may be the same. For example, two or more sampling points may be arranged in each chip section.

For example, the controller 140 may measure at a plurality of sampling points t ₁ , t ₂ , ..., t _N in a section where the cumulative value is maximum, that is, a section including a pulse, in order to obtain a slope of the pulse. The received signal values r (t ₁ ), r (t ₂ ,), ..., r (t _N ) may be used. The controller 140 determines the slope of the pulse using the discriminant shown in Equation 2 or 3 and determines the most significant bit value accordingly. A method of obtaining the most significant bit will be described later in more detail with reference to FIG. 8.

8 is a diagram illustrating acquiring a most significant bit based on an accumulated value of a pulse signal value sampled at a plurality of sampling time points in a symbol in the underwater laser communication method according to an embodiment. 8 (a) is an example of two sampling time points. 8 (b) shows an example of multiple sampling time points of a single gradient pulse.

As shown in FIG. 8A, two sampling values may be used as follows.

Here, r (tf) means a value received at the front sampling time point tf in the inclined pulse, and r (tb) means a value received at the sampling time point tb in the backward direction in the tilted pulse. MSB is the most significant bit. If the received value at the front is less than the received value at the back, the sign of the pulse slope is considered positive and the MSB bit is determined to be "0".

As shown in FIG. 8 (b), multiple points may be used within one chip spacing. In this case, the absolute value of the first half and the absolute value of the second half are accumulated based on the center point of the pulse and the magnitude is compared. This symbol decision is given by Equation 3.

Where N is the number of sampling values of a single tilted pulse. Conventionally, a matched filter has been used for symbol determination, but the method according to SL-PPM does not use a matched filter and has a lower computational complexity and is more efficient than the conventional method.

9 to 11 are views illustrating a water tank experimental apparatus using the underwater laser communication method according to an embodiment. Experiments were conducted to verify the performance of the underwater wireless laser communication method using SL-PPM.

The signal generated by the arbitrary waveform generator is converted into an optical signal at the laser diode and transmitted to the tank. Both walls of the tank were equipped with anti-reflective (AR) coated glass to minimize transmission signal attenuation and averaged over 95%. Reflective mirrors were also used to increase the transmission distance. At the receiver, the light is collected by a Fresnel lens and converted into an electrical signal by an avalanche photo diode and transmitted.

A blue laser diode with a wavelength of 450 nm was used. Since blue-green lasers have minimal energy fading in the ocean, underwater wireless laser communication using low-absorption windows of sea water in the turquoise portion of the electromagnetic spectrum is safe and efficient over short distances.

Table 1 shows the experimental results of the uncoded bit error rate when the channel coding method is not applied to the method invented at a transmission rate of 100 Mbps at a transmission distance of 12 m. As shown by the attenuator gain (attenuator). Larger attenuation gains reduce the signal-to-noise ratio as the strength of the received signal decreases.

Attenuation Gain (dB) 20 25 30 uncoded BER

12 is a diagram comparing bit error rates between the underwater laser communication method measured by the tank experimental apparatus and the conventional OOK method. Tank experiments were performed under conditions of turbidity of 0.8 NTU (Nephelometric Turbidity Unit), transmission distance of 8m, and data rate of 100 Mbps.

When comparing the bit error rates of the SL-PPM method and the conventional on-off keying (OOK) method according to the received power, the SL-PPM method has a lower probability of error occurrence than the conventional OOK method based on the same received power. You can see that. Here, the turbidity of 0.8 NTU is the actual turbidity value of seawater collected in major domestic ports.

Those skilled in the art will appreciate that the invention may be implemented in combination with other program modules and / or as a combination of hardware and software. For example, the invention may be embodied by a computer-readable medium.

Any medium that can be accessed by a computer can be a computer readable medium, which can be volatile and nonvolatile media, transitory and non-transitory media, removable and non-transitory media. Removable media. By way of example, and not limitation, computer readable media may comprise computer readable storage media and computer readable transmission media.

Computer-readable storage media are volatile and nonvolatile media, temporary and non-transitory media, removable and non-removable implemented in any method or technology for storing information such as computer readable instructions, data structures, program modules or other data. Media. Computer-readable storage media may include RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital video disk or other optical disk storage device, magnetic cassette, magnetic tape, magnetic disk storage device or other magnetic storage. It includes, but is not limited to, a device or any other medium that can be accessed by a computer and used to store desired information.

Computer-readable transmission media typically embody computer readable instructions, data structures, program modules or other data in a modulated data signal, such as a carrier wave or other transport mechanism, and the like. Includes all information delivery media. The term modulated data signal means a signal that has one or more of its characteristics set or changed to encode information in the signal. By way of example, and not limitation, computer readable transmission media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared, or other wireless media. Combinations of any of the above should also be included within the scope of computer readable transmission media.

One of ordinary skill in the art would appreciate that the various exemplary logical blocks, modules, processors, means, circuits and algorithm steps described in connection with the embodiments disclosed herein may be implemented in electronic hardware, It will be appreciated that for purposes of the present invention, various forms of program or design code, or combinations thereof, may be implemented. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the particular application and design constraints imposed on the overall system. Those skilled in the art may implement the described functionality in various ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The various embodiments presented herein may be embodied in a method, apparatus, or article of manufacture using standard programming and / or engineering techniques. The term "article of manufacture" includes a computer program, carrier, or media accessible from any computer-readable device. For example, computer-readable storage media may include magnetic storage devices (eg, hard disks, floppy disks, magnetic strips, etc.), optical disks (eg, CDs, DVDs, etc.), smart cards, and flashes. Memory devices (eg, EEPROM, cards, sticks, key drives, etc.), but are not limited to these. The term “machine-readable medium” includes, but is not limited to, wireless channels and various other media capable of storing, retaining, and / or delivering instruction (s) and / or data.

It is to be understood that the specific order or hierarchy of steps in the processes presented is an example of exemplary approaches. Based upon design priorities, it is understood that the specific order or hierarchy of steps in the processes may be rearranged within the scope of the present invention. The accompanying method claims present elements of the various steps in a sample order, but are not meant to be limited to the specific order or hierarchy presented.

The description of the presented embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the invention. Thus, the present invention should not be limited to the embodiments set forth herein but should be construed in the broadest scope consistent with the principles and novel features set forth herein.

100, 200 underwater laser communication device
120 laser communication unit
140 control unit
142 pulse generator
144 pulse position modulator

Claims (10)

An underwater laser communication method using binary data including a most significant bit and a least significant bit,
Receiving a laser signal comprising a pulse from an external communication device;
Acquiring the lower bit based on position information of a pulse in a symbol that is a time interval of the laser signal;
Obtaining the most significant bit based on a slope sign of a pulse in the symbol,
Underwater laser communication method. According to claim 1,
The most significant bit is
Obtained based on a cumulative value of a pulse signal value sampled at a plurality of sampling time points constituting the symbol,
Underwater laser communication method. The method of claim 2,
The symbol includes a first section including the pulse, determined according to the position information of the pulse,
The plurality of sampling points are located in the first section.
Underwater laser communication method. The method of claim 2,
The most significant bit is a first equation

Determined by
MSB is the most significant bit, N is the number of samplings for the pulse signal value, r (t _n ) is the pulse signal value,
Underwater laser communication method. According to claim 1,
The lower bit,
The cumulative value of the laser signal values sampled at the plurality of chip views constituting the symbol is obtained based on the chip view point at which the maximum value is obtained.
Underwater laser communication method. An underwater laser communication method using binary data including a most significant bit and a least significant bit,
A symbol is a time interval of a laser signal, and generating a pulse according to a slope sign of a pulse in a symbol determined based on the most significant bit;
Modulating the position of the pulse according to the position information of the pulse in the symbol determined based on the lower bit; And
Transmitting a laser signal comprising a pulse to an external communication device,
Underwater laser communication method. The method of claim 6,
Second equation

Generating the laser signal according to;
t is the time, T _S is the length of the symbol, L is the number of chip time points constituting the symbol, m is an integer from 1 to L,
Underwater laser communication method. A computer-readable recording medium storing a computer program for performing the underwater laser communication method according to any one of claims 1 to 7. An underwater laser communication apparatus using binary data including a most significant bit and a least significant bit,
A laser communication unit receiving a laser signal including a pulse from an external communication device; And
And a controller configured to acquire the lower bit based on position information of a pulse in a symbol that is a time interval of the laser signal, and obtain the most significant bit based on a slope code of the pulse in the symbol.
Underwater laser communication device. An underwater laser communication apparatus using binary data including a most significant bit and a least significant bit,
A pulse generator configured to generate a pulse according to a slope code of a pulse in a symbol determined based on the most significant bit;
A pulse position modulator for modulating a position of a pulse according to position information of a pulse in a symbol determined based on the lower bit; And
It includes a laser communication unit for transmitting a laser signal containing a pulse to an external communication device
Underwater laser communication device.

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