KR102078943B1 - Underwater communication method adaptive to underwater environment - Google Patents

Abstract

Disclosed are an underwater communication method and an underwater communication system that are adaptive to changes in the underwater environment. Underwater communication method according to the present invention, a plurality of sensor nodes for detecting the underwater information, and underwater communication of the underwater communication system including a central node that collects the underwater information detected by each sensor node and transmits to the terrestrial network A method comprising: (a) determining a multi-frequency communication scheme or a single frequency communication scheme; (b) determining a frame structure parameter corresponding to the determined communication scheme; (c) determining a communication parameter corresponding to the determined communication scheme; (d) performing communication by applying a power control scheme; And (e) determining whether the communication performance satisfies the target performance, and determining whether the communication condition satisfies the set condition when the target performance is not satisfied. Perform underwater communication adaptively to the environment.

Description

Underwater communication method adaptive to underwater environment {UNDERWATER COMMUNICATION METHOD ADAPTIVE TO UNDERWATER ENVIRONMENT}

The present invention relates to an underwater communication method, and more particularly, to an underwater communication method adaptive to the underwater environment.

Recently, with increasing interest and importance in marine resource exploration, marine environment monitoring, underwater military defense, etc., the demand for underwater communication that can collect various underwater information in the ocean is increasing.

Such underwater communication performs communication using sound waves due to the characteristics of the medium. Here, the communication network for underwater information transmission comprises a sensor node capable of transmitting and receiving underwater information in the underwater environment, and obtaining and controlling the underwater information from the installed sensor node.

Underwater communication networks have a relatively small bandwidth of transmitted signals and attenuation over distance due to the underwater communication environment using sound waves. In other words, the frequency used in the underwater communication network in order to perform reliable communication at a distance of several km to several tens of kilometers is very limited.

The communication channel environment in water varies greatly in spatial characteristics according to geographic and geological factors, and the characteristic changes in time due to water temperature, salinity, and depth. In terrestrial communications, radio waves travel at the speed of light, but the speed of sound waves used in underwater communications is about 1500 m / s, much slower than light. Therefore, it is very difficult to grasp the change of the communication channel in real time in the underwater communication environment. As the demand for underwater information acquisition using an underwater communication network increases, the number of sensor nodes performing underwater communication increases accordingly. In this case, it is very difficult to identify and respond to changes in the underwater communication channel environment experienced by each sensor node in real time.

Therefore, a new method for acquiring a reliable communication link by adaptively responding to an underwater communication environment that changes in time and space must be sought.

Publication No. 10-2010-0031445 (Publishing date: March 22, 2010)

The present invention was devised to solve the above-described problems, and in addition to selecting the optimal underwater communication channel adaptively according to the underwater environment in spatially different places, in the underwater channel environment continuously changing in time, each channel environment It is an object of the present invention to provide an underwater communication method adaptive to the underwater environment in which an optimal underwater communication method can be selected.

Underwater communication method according to an aspect of the present invention for achieving the above object, a plurality of sensor nodes for detecting the underwater information, and the center of collecting the underwater information detected by each sensor node to transmit to the ground network An underwater communication method in an underwater communication system comprising a node, comprising: (a) determining a multi-frequency communication method or a single frequency communication method; (b) determining a frame structure parameter corresponding to the determined communication scheme; (c) determining a communication parameter corresponding to the determined communication scheme; (d) performing communication by applying a power control scheme; And (e) determining whether the communication performance satisfies the target performance, and determining whether the communication condition satisfies the set condition when the target performance is not satisfied. Perform underwater communication adaptively to the environment.

Here, when the above-described underwater communication method satisfies the set condition, step (a) is performed again.

In addition, if the set conditions do not meet, step (d) is performed again to control power.

In addition, when the target performance is satisfied, communication is performed by maintaining the current power control method and communication method.

At this time, in the above-described underwater communication method, the transmitting side of the plurality of sensor nodes and the central node may determine to perform the adaptive underwater communication.

Here, the transmitter determines to perform adaptive underwater communication based on the reference signal transmitted from the receiver or feedback information about the communication link transmitted from the receiver.

In addition, the transmitting side may transmit adaptive underwater communication information and communication data separately in time / frequency / spatial resources or transmit them by multiplexing.

In addition, in the above-described underwater communication method, the receiving side of the plurality of sensor nodes and the central node may determine to perform the adaptive underwater communication.

At this time, the receiver determines to perform adaptive underwater communication based on the reference signal transmitted from the transmitter or feedback information about the communication link transmitted from the transmitter.

In step (a), the communication method may be determined based on at least one of a channel condition, a battery state, a Signal to Noise Ratio (SNR), a Signal to Interference Noise Ratio (SINR), and an Error Vector Magnitude (EVM).

In addition, the multi-frequency communication method is Orthogonal Frequency Division Multiplexing (OFDM), Filter Bank Multi Carrier (FBMC), Filtered Multi Tone (FMT), Universal filtered Multi Carrier (UFMC), Generalized Frequency Division Multiplexing (GFDM), SC-FDMA ( Single Carrier Frequency Division Multiple Access).

In addition, the single frequency communication method may be one of communication methods including Direct Sequence Spread Spectrum (DSSS) as a method in which communication data occupies a given bandwidth.

(b) step (b-1) selecting a cyclic prefix (CP) when the multi-frequency communication scheme is determined; And (b-2) selecting an interval of pilot symbols.

Here, step (b-1) selects one CP among CPs having different lengths based on at least one of a channel condition, an SNR, an SINR, an EVM, and a battery state.

In addition, step (b-2) selects the interval of the pilot symbol in the frequency and time domain, respectively, based on at least one of the channel condition, the SNR, the SINR, the EVM, and the battery status.

The step (b) includes (b-3) selecting a spreading factor when a single frequency communication scheme is determined; And (b-4) selecting the density of the pilot symbol.

Here, step (b-3) selects one of the spreading factors among different spreading factors based on at least one of a channel condition, an SNR, an SINR, an EVM, and a battery state.

In addition, step (b-4) selects the density of the pilot symbol in the frame based on at least one of the channel condition, the SNR, the SINR, the EVM, and the battery status.

(c) step (c-1) selecting the number of repetitive transmissions; And (c-2) selecting a modulation scheme and a code rate.

Here, in step (c-1), when the multi-frequency communication method is selected, the number of repetitive transmissions is selected in the frequency and time domains based on at least one of channel conditions, SNRs, SINRs, EVMs, and battery conditions.

In addition, step (c-2) selects a preset modulation scheme and code rate based on at least one of channel conditions, SNRs, SINRs, EVMs, and battery conditions.

In this case, in step (c-1), when the single frequency communication method is selected, the number of repetitive transmissions in the time domain is selected based on at least one of channel conditions, SNRs, SINRs, EVMs, and battery conditions.

Underwater communication system according to an aspect of the present invention for achieving the above object, a plurality of sensor nodes for detecting underwater information; And a central node that collects the underwater information detected by each sensor node and transmits the information to a terrestrial network, including a reference signal transmitted from a receiving side or a receiving side of the plurality of sensor nodes and the central node. Based on the feedback information about a communication link, it determines to perform underwater communication adaptive to changes in the underwater environment.

Underwater communication system according to another aspect of the present invention for achieving the above object, a plurality of sensor nodes for detecting underwater information; And a central node that collects the underwater information detected by each sensor node and transmits the information to a terrestrial network, including a reference signal transmitted from a transmitting side or a transmitting side of the plurality of sensor nodes and the central node. Based on the feedback information about a communication link, it determines to perform underwater communication adaptive to changes in the underwater environment.

According to the present invention, not only the optimal underwater communication channel is adaptively selected according to the underwater environment in spatially different places, but also in the underwater channel environment that changes continuously in time, the optimal underwater communication method is selected for each channel environment. It becomes possible.

1 is a view showing a general underwater communication network used in the underwater communication shown to help the understanding of the present invention.
FIG. 2 is a diagram conceptually illustrating a centrally controlled underwater communication network implemented to explain an underwater communication method according to an embodiment of the present invention.
3 is a diagram illustrating a process of dividing a frequency band for underwater communication within a limited frequency bandwidth according to an embodiment of the present invention.
4 is a diagram illustrating a process of allocating the same frequency band to a plurality of sensor nodes according to a communication distance within a limited frequency bandwidth according to an embodiment of the present invention.
FIG. 5 is a schematic block diagram illustrating the underwater communication method according to an embodiment of the present invention.
FIG. 6 is a diagram illustrating a schematic configuration of a sensor node for explaining the underwater communication method according to an embodiment of the present invention.
FIG. 7 is a diagram illustrating a schematic configuration of a central node for explaining the underwater communication method according to an embodiment of the present invention.
8 is a flowchart illustrating a method of underwater communication according to a first embodiment of the present invention.
9 is a flowchart illustrating a method of underwater communication according to a second embodiment of the present invention.
10 is a flowchart illustrating an underwater communication method according to a third embodiment of the present invention.
11 shows a mutual relationship with a receiving side when the transmitting node determines the adaptive underwater communication method.
12 shows the mutual relationship with the transmitting side when the receiving node determines the adaptive underwater communication method.
13 is a flowchart illustrating a method of underwater communication according to a fourth embodiment of the present invention.
FIG. 14 is a diagram illustrating frame structure parameter determination and communication parameter determination in the underwater communication method shown in FIG. 13.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings, and the same or similar components will be given the same reference numerals regardless of the reference numerals, and redundant description thereof will be omitted. The suffixes "part", "node", "axis" and "dimension" for components used in the following description are given or used in consideration of ease of specification, meanings or roles distinguished from each other in themselves. Does not have

In addition, in describing the embodiments disclosed herein, when it is determined that the detailed description of the related known technology may obscure the gist of the embodiments disclosed herein, the detailed description thereof will be omitted. In addition, the accompanying drawings are intended to facilitate understanding of the embodiments disclosed herein, but are not limited to the technical spirit disclosed herein by the accompanying drawings, all changes included in the spirit and scope of the present invention. It should be understood to include equivalents and substitutes.

Terms including ordinal numbers such as first and second may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

When a component is said to be "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in the middle. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

Singular expressions include plural expressions unless the context clearly indicates otherwise.

In this application, the terms "comprises" or "having" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It is apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit and essential features of the present invention.

1 is a diagram illustrating a general underwater communication network used for underwater communication, which is shown for better understanding of the present invention.

In the underwater communication network shown in FIG. 1, a plurality of sensor nodes 1, a sink node 5, and an intermediate node 3 which serves to transfer information between the sensor node 1 and the sink node 5 are illustrated. It is configured to include. In the underwater communication network configured as described above, the transmission of underwater information is performed as follows.

Referring to FIG. 1, a sensor node 1 to transmit detected underwater information among the plurality of sensor nodes 1 is underwater to a sink node 5 through an intermediate node 3 composed of several steps. Send the information.

However, the underwater communication network configured in this way must pass through the intermediate node 3 of several stages in transferring the underwater information detected from the sensor node 1 to the sink node 5. Therefore, in the underwater communication network connected to the sensor node 1, the intermediate node 3 of various stages, and the sink node 5, a routing algorithm for transmitting the detected underwater information is complicated.

In addition, in such an underwater communication network, if a transmission error occurs in the process of transferring the underwater information from the sensor node 1 to the sink node 5, the process for retransmission of the detected underwater information is cumbersome.

In addition, such an underwater communication network has a problem of having to pass through the intermediate node 3 of several stages, and thus, if a problem occurs in the intermediate node for transmitting underwater information, the use of the sensor node associated with the intermediate node in which the problem occurs is impossible.

Due to these parts, the general underwater communication network shown in FIG. 1 inevitably decreases the use efficiency of equipment including data transmission efficiency in the process of acquiring and transmitting various underwater information. To solve this problem is a centrally controlled underwater communication network.

In the following description of the present invention, "frequency band" and "frequency" may be used interchangeably. Here, "frequency" refers to a frequency included in the "frequency band," and since the frequency includes almost the same signal at a frequency included in a predetermined range of the frequency, the two words may be considered to have the same meaning. .

FIG. 2 is a diagram conceptually illustrating a centrally controlled underwater communication network implemented to explain a method of underwater communication according to an embodiment of the present invention.

The central control underwater communication network used in the embodiment of the present invention is configured by connecting sensor nodes centrally in an underwater environment.

Here, the central control underwater communication network includes one or more sensor nodes 10. At this time, the sensor node 10 is installed to be fixed or movable in the underwater environment. In addition, the sensor node 10 is provided as many as possible in order to acquire a lot of underwater information.

The central control type underwater communication network includes a central node 20 which collects underwater information acquired from a plurality of sensor nodes 10. Here, the central node 20 performs a function of transmitting the underwater information collected by the plurality of sensor nodes 10 to a terrestrial network (not shown).

The central control type underwater communication network comprised in this way is controlled as follows as a whole.

3 is a diagram illustrating a process of dividing a predetermined number of small frequency bands within a limited frequency band to control underwater communication according to an embodiment of the present invention.

Referring to FIG. 3, underwater communication between the central node 20 and the plurality of sensor nodes 10 is basically performed by sound waves. The entire frequency band usable in the central node 20 is divided into a forward frequency band and a reverse frequency band.

Here, the entire frequency band usable by the central node 20 means that underwater communication with the central node 20 is possible for the sensor nodes 10 installed at different distances from the central node 20. Refers to the frequency band. That is, it is possible to transmit a signal from the central node 20 to the sensor node 10 installed at an arbitrary position, and express the frequency band used to receive the signal transmitted from the sensor node 10 at the central node 20. do.

In addition, the forward frequency band is used when transmitting signals from the central node 20 to the plurality of sensor nodes 10. The frequency band used at this time is set to the lowest frequency band f0 among the frequency bands available to the central node 20.

In general, the lower the frequency of the transmission and reception in the underwater communication environment increases the communication range. Therefore, when transmitting a signal from the central node 20 to the sensor node 10, it should be possible to receive the signal from all sensor nodes 10 regardless of the distance. Therefore, the frequency band f0 having the lowest frequency is determined as the forward frequency band and used when transmitting signals from the central node 20 to the plurality of sensor nodes 10.

In addition, the reverse frequency band is used when performing signal transmission from each of the plurality of sensor nodes 10 to the central node 20. Of all the frequency bands usable herein, all of the remaining frequency bands except the forward frequency band are included in the reverse frequency band.

The reverse frequency band is further divided into a plurality of small frequency bands. At this time, the division into smaller frequency bands, the sensor nodes capable of transmitting and receiving signals in the same frequency band between the distance to the sensor node 10 with respect to the center node 20 in the same area, the frequency band as small as the number of divided areas It divides into numbers (M area | regions mentioned later).

At this time, each divided small frequency band is allocated to be used for signal transmission of the sensor node 10 installed at different positions. For example, the frequency band f1 is allocated to the sensor node 10 which is located farthest from the central node 20. The frequency band fM is allocated to the sensor node 10 located at the closest distance to the central node 20.

In this case, the sensor node 10 located at the longest distance from the center node 20 is allocated the lowest frequency band among the frequency bands included in the reverse frequency band. On the contrary, the highest frequency band among the frequency bands included in the reverse frequency band is allocated to the sensor node 10 located at the closest distance with respect to the central node 20. As mentioned earlier, since the communication range increases as the frequency to be transmitted and received is lower in the underwater communication environment, the frequency f1 of the low frequency band is allocated as the frequency for the long-distance communication. The frequency fM of the highest frequency band is allocated to the frequency for the short-range communication.

In this process, each sensor node 10 is assigned a frequency band for underwater communication, and then the underwater information to the central node 20 is assigned using the frequency band to which the underwater information detected by the sensor node 10 is assigned. Underwater communication is carried out in which the transmission takes place.

4 is a diagram illustrating a process of allocating the same frequency band to a plurality of sensor nodes within a limited frequency bandwidth according to an embodiment of the present invention.

Underwater communication is more affected by environmental factors than land communication. Therefore, in the process of detecting the underwater information using the underwater sensor in the sensor node 10, due to environmental impact, the loss situation of the sensor node 10 is bound to occur. In addition, even if any sensor node 10 detects the underwater information normally, the success rate of data transmission may not always be 100% satisfied in the process of transmitting the underwater information detected by the sensor node 10 to the central node 20. Therefore, if the conditions of the underwater communication network are allowed, it is possible to install the number of the sensor nodes 10 as much as possible, so that the underwater information can be obtained more accurately and variously.

On the other hand, as shown in Figure 4, between the central node 20 and the sensor node 10, there is an area capable of transmitting signals in the same frequency band. That is, the divided frequency band fM is equally allocated to the sensor nodes 10 existing in the area 1 included in the closest distance with respect to the central node 20. The divided frequency band f1 is equally allocated to the sensor nodes 10 existing in the region M that is included at the longest distance with respect to the central node 20.

The division of the area between the center node 20 and the sensor node 10 into the same area or another area is performed within a range in which signals can be transmitted and received between the center node 20 and the sensor node 10. That is, the sensor nodes capable of underwater communication in the same frequency band fM are included in the region 1. In addition, sensor nodes capable of underwater communication in the same frequency band f1 are included in the area M. FIG.

The allocation of the same frequency band to multiple sensor nodes in this way is because the frequency band usable in the central node 20 is limited. For example, in order to acquire the underwater information more accurately and variously, the number of sensor nodes has to be increased. In this case, a case where the number of sensor nodes 10 installed in the entire frequency band usable by the central node 20 is larger than the divided number of reverse frequency bands may occur. In such a case, as shown in Fig. 4, the same frequency band is assigned to the sensor node existing in the same area to control underwater communication.

On the other hand, when the same frequency band is assigned to a plurality of sensor nodes as described above, the plurality of sensor nodes 10 in the same area assigned the same frequency band is controlled by various control methods of the central node 20 ( A frequency division multiple access method, a time division multiple access method, a code division multiple access method, a carrier sensing multiple access method, etc.) are performed to communicate with the central node 20. Here, the description of the known multiple access scheme will be omitted.

Next, in order to enable adaptive communication according to the distance between the central node and the sensor node in the underwater communication network according to an embodiment of the present invention, a process of detecting distance information between the sensor node and the central node is required. Prior to this description, an approximate configuration for transmitting and receiving underwater information between the central node and the sensor node of the present invention will be described.

5 is a diagram illustrating a schematic configuration diagram for explaining the underwater communication method according to an embodiment of the present invention.

Referring to FIG. 5, the plurality of sensor nodes 10 collect underwater information and transmit the collected underwater information to the central node 20. In this case, transmission and reception of underwater information using sound waves are performed between the plurality of sensor nodes 10 and the central node 20 to enable signal transmission due to the characteristics of the medium within the underwater communication network 50. In this case, each sensor node 10 preferably transmits the predetermined identification information together with the underwater information so that the central node 20 can identify when transmitting the signal of the underwater information to the central node 20. .

The central node 20 transmits the underwater information collected from the plurality of sensor nodes 10 to the ground. Here, the central node 20 transmits the underwater information acquired to the management node 64 of the terrestrial communication network 60. Accordingly, the central node 20 performs underwater communication with the plurality of sensor nodes 10 in the underwater communication network 50 and simultaneously with the ground management node 64. The management node 64 connects the underwater information received through the central node 20 with the terrestrial communication network 62 using a radio signal.

6 is a diagram illustrating a schematic configuration diagram of a sensor node applied to the underwater communication method according to an embodiment of the present invention.

Referring to FIG. 6, the sensor node 10 modulates data sensed by one or more sensor units 30 and each sensor unit 30 to collect necessary data in water, converts the data into sound waves, and then converts the center node into a central node. A data transmitter 36 for transmitting to 20, and a data receiver 38 for receiving and demodulating the sound wave signals transmitted from the central node 20. FIG. Here, the data transmitter 36 and the data receiver 38 are included in the transceiver 40. The sensor node 10 may further include a controller 32 that performs control between the sensor unit 30 and the transceiver unit 40. In addition, the sensor node 10 may include a memory 34 that stores various data and algorithms required for overall operation control and stores underwater information detected by the sensor unit 30.

The plurality of sensor units 30 sense various kinds of underwater information including water temperature, dissolved oxygen amount, seismic wave, and output the sensed data to the controller 32 according to its purpose. Although the sensor unit 30 may be a digital sensor, the sensor unit 30 may be configured to convert the data sensed as an analog signal to digital output. In this case, the sensor unit 30 may include an analog / digital converter for converting an analog signal into a digital signal. In all the configurations of the present invention, the signal processed data is based on digital signals.

The transceiver 40 performs a function of transmitting or receiving data using sound waves underwater. That is, the data transmitter 36 modulates the underwater information detected by the sensor unit 30, converts the underwater information into an ultrasonic signal, and transmits the ultrasonic signal to the central node 20. The data receiver 38 receives and demodulates the ultrasonic signal transmitted from the central node 20 and outputs the demodulated signal to the controller 32.

The sensor node 10 receives the underwater information transmitted from the central node 20 through the data receiver 38. At this time, in order to enable the reception of the signal transmitted from the central node 20, the data receiver 38 is frequency set to the frequency included in the forward frequency band. In addition, the data transmitter 36 is then set to a specific frequency included in the frequency band allocated to itself, and transmits the information for transmission to the central node 20 on the set specific frequency. Therefore, the transceiver 40 includes a configuration for setting a frequency under the control of the controller 32. Since this configuration is made by a known technique, the description is omitted. In the initial setting process in which the frequency setting of each sensor node 10 is not made, the signal is set to the forward frequency band when receiving the signal from the central node 20, and the signal is transmitted to the central node 20 before the initial setting. Is controlled to be set to the lowest frequency band among the divided reverse frequency bands.

On the other hand, the sensor node 10 may transmit the underwater information to the central node 20 according to the set period, or may transmit the underwater information to the central node 20 in response to a request from the central node 20. However, since the underwater environment is severely changed in time and space, when the sensor node 10 transmits the underwater information to the central node 20 according to a set cycle or when there is a request for underwater information, the underwater environment changes. Differences can occur between the time of transmission and the time of transmission of underwater information.

In addition, the sensor node 10 may measure the underwater information at a set cycle, and may transmit the measured underwater information to the central node 20 whenever the underwater information is measured. In this case, however, if the measurement period of the underwater information is set short, it can respond quickly to the change of the underwater environment, but the central node 20 must receive and process the underwater information from the plurality of sensor nodes 10, thereby congesting traffic. May result.

Therefore, the sensor node 10 measures the underwater information at a set period, but compares the previously measured underwater information and the currently measured underwater information, and when the comparison result is more than the set difference to the underwater information to the central node 20 Can transmit In addition, the sensor node 10 transmits the underwater information in a period set at a relatively long time interval by combining the above-described schemes, when there is a request signal from the central node 20 and when there is a change more than the value set in the underwater information Edo can also transmit underwater information to the central node 20. At this time, the measurement of the underwater information of the sensor node 10 and the transmission of the underwater information is preferably made in real time. However, if the real-time control of underwater information measurement is unreasonable, it is also possible to repeat the measurement at regular time intervals, avoiding the time when underwater communication is performed. In this case, since the use frequency may be changed relative to the distance, the sensor node 10 needs to variably control a usable frequency band in real time for underwater communication with the central node 20.

In such a part, the transceiver 40 of the sensor node 10 is preferably configured to be able to variably control the set frequency. That is, the frequency for transmitting information is variably controlled according to the installed position of the sensor node 10 so that the information to be transmitted can be transmitted to the central node 20.

The controller 32 performs a control for storing various kinds of underwater information detected by the sensor unit 30 in the memory 34, or performs a function of controlling transmission and reception of underwater information made through the transceiver unit 40.

In addition, the controller 32 performs control for measuring the underwater information of the sensor unit 30. To this end, the control unit 32 receives a reference signal transmitted by the central node 20 for the measurement of the underwater information by the data receiving unit 38 and includes a configuration for calculating the underwater information. The calculation of the underwater information may be applied to a variety of calculators corresponding to the underwater information to be measured by the sensor unit 30, for example, seawater temperature, seawater salinity, and the like, and thus, a detailed description thereof will be omitted. .

The memory 34 stores various information used or needed and detected by the sensor node 10. Preferably, the underwater information detected by the sensor unit 30 is also stored in the memory 34. In particular, the memory 34 stores various information to be transmitted to the central node 20 when the sensor node 10 intends to directly transmit the underwater information measured by the sensor unit 30 to the central node 20. .

7 is a view showing a schematic configuration diagram of a central node applied to the underwater communication method according to an embodiment of the present invention.

Referring to FIG. 7, the central node 20 may be configured to perform transmission and reception of signals with the sensor node 10 and the first transmission / reception unit 22 for performing transmission and reception of an underwater signal with sound waves, and the management node 64. It is configured to include a second transceiver 21. In addition, the central node 20 includes a control unit 28 that controls the first and second transceivers, controls information storage, and a memory 29 that stores various kinds of information. Here, the second transceiver 21 may be configured to be transmitted by ultrasonic waves or may be configured to be transmitted by a wireless signal, depending on whether the position of the central node 20 is above or below the surface of the water.

In addition, the central node 20 includes a frequency divider 27 for dividing the entire frequency band which can be used by the forward frequency band and the reverse frequency band, and dividing the reverse frequency band into smaller frequency bands. In this case, since the frequency divider 27 is used to transmit and receive the underwater information with the sensor node 10, the frequency divider 27 may be included in the first transceiver 22.

As shown in FIG. 4, the frequency divider 27 is configured to divide the entire frequency band usable by the central node 20 into frequency bands as small as the number of regions (M). Therefore, the controller 28 controls the frequency division of the frequency divider 27, and then controls the frequency of the frequency divider 27 to be divided into the corresponding frequency when transmitting and receiving a signal with an arbitrary sensor node 10 to transmit and receive a signal. This is controlled to be done normally.

The data transmitter 26 in the first transceiver 22 is set to the forward frequency band f0 to enable signal transmission to all the sensor nodes 10. The data receiver 24 in the first transceiver 22 is set to all reverse frequencies existing in the frequency band assigned to any sensor node to which underwater communication is to be performed. However, in the initial setting process in which no frequency is set in each sensor node 20, the data receiver 24 is set to the lowest frequency band among the divided reverse frequencies. This is to enable the sensor node 10 to receive a signal transmitted from the sensor node existing at all distances since the sensor node 10 is set before the frequency is set.

To this end, a frequency divider is performed through the frequency divider 27 under the control of the controller 28, and a series of processes in which the frequency of the data receiver 24 is set to the divided frequency is controlled. The frequency division operation of the frequency divider is preferably performed digitally. In addition, the data receiver 24 includes a variable frequency control configuration to enable normal signal reception in the process of transmitting and receiving signals with all sensor nodes.

In addition, the control unit 28 may control the sensor node 10 and the central node 20 according to the power management for each sensor node 10, multiple access control for the sensor node 10 existing at a similar distance to the traffic control, and the need. Control to detect the distance between In the exemplary embodiment of the present invention, the distance detection process may be performed by the control unit 32 of the sensor node 10, but the distance detection process may be performed by the control unit 28 of the central node 20. Do.

Therefore, the controller 28 receives the reference signal transmitted by the sensor node 10 for distance detection by the data receiver 24 in the initial setup process in which the frequency of the sensor node is not set, and the magnitude of the received power. It includes a detectable configuration. Here, the power strength of the received signal can be detected by a simple calculation process by directly detecting the power of the received signal or by detecting current or voltage. Also, the received power magnitude detection configuration can be applied by various techniques including known power detectors. In addition, the detection of the received power magnitude may be performed by the sensor node and receive only the detection information. In addition, the current size can be detected simply by providing a current detecting resistor in the receiver. Similarly, the current magnitude detection may be performed at the sensor node and provided with only the detection information. Since these detection parts use a known technique, a detailed description thereof will be omitted. The distance estimation using the power intensity of the detected received signal may be estimated using the distance value compared to the power intensity previously stored in the memory 29.

As another method for detecting the distance, the controller 28 may detect and use a delay time required to arrive at the central node 20 after transmitting a signal from the sensor node 10. Here, for example, the delay time detection may be detected by comparing the time point information at which the sensor node 10 starts transmitting a signal with the time point information signal arriving at the central node 20. In order to detect the arrival time information, the control unit 28 preferably includes a time counting function or the like. In addition, the distance estimation using the detected delay time can estimate the distance using the distance value compared with the delay time previously stored in the memory 29.

The memory 29 is used for storing various types of information used or needed and detected by the sensor node 10. In particular, the memory 29 stores various information to be used for distance detection when the distance detection is performed at the central node 20. For example, by using the received power strength, delay time, etc. received from the sensor node 10, the information for determining the distance between the central node 20 and the sensor node 10, and the allocation according to the estimated distance information It stores frequency band information that can be communicated underwater. The controller 28 estimates the distance using various kinds of information stored in the memory 29 and selects a specific frequency band to be allocated to any sensor node. The memory 29 may store control information for frequency division, and may also store related information such as a divided frequency band and a sensor node set therein. The memory 29 may also store underwater information collected from sensor nodes.

8 is a flowchart illustrating a method of underwater communication according to the first embodiment of the present invention. 8 illustrates a control method used when the central node 20 allocates a specific frequency to the sensor node 10.

Referring to FIG. 8, in the underwater communication network according to the embodiment of the present invention, distance information between the central node 20 and the sensor node 10 should be detected. A specific frequency band is allocated to the sensor node 10 according to the detected distance information. In other words, it is necessary to adaptively allocate a specific frequency according to the detected distance information.

First, the control unit 28 of the central node 20 checks all available frequency bands of the central node 20, and divides the identified available all frequency bands into a forward frequency band and a reverse frequency band, as shown in FIG. (200 steps)

In addition, as shown in FIG. 4, the controller 28 performs control to divide the reverse frequency band into smaller frequency bands by the number of regions (M) (step 205). Steps 200 and 205 are preferably preset according to the performance of the central node. That is, when the central node 20 transmits and receives a signal in the underwater environment, the central node 20 may store and store a frequency that can be transmitted farthest in the forward frequency band. In addition, when the central node 20 transmits and receives a signal in an underwater environment, each use frequency may distinguish and store a distance (area) in which a signal can be transmitted. The divided distance and frequency values are stored in the memory 29 of the central node 20 and the memory 34 of the sensor node 10, and may be used later in the frequency setting process.

The controller 28 reads from the memory 29 a reference signal to be used for detecting previously stored distance information. The reference signal is carried in a forward frequency band, and is converted into an ultrasonic signal through the data transmitter 26 and transmitted to all sensor nodes 10 included in all available frequency bands of the central node 20, and the sensor node 10 In operation 210, the receiving unit 38 receives the reference signal.

The sensor nodes 10 receiving the reference signal in step 210 detect the power strength of the received signal, the time delay used for signal transmission, and estimate the distance from the central node 20 using the detection signal (step 220). ). The distance estimation between the sensor node 10 and the center node 20 is estimated using the power strength of the received signal.

After the distance estimation is made in step 220, the sensor node 10 requests to allocate a frequency band corresponding to the distance estimated by the central node 20 to its frequency band (step 230). In a specific frequency band request process in step 230, the frequency band request signal is transmitted using the frequency band set to the lowest frequency band among the reverse frequency bands since the frequency band is assigned to the corresponding sensor node. In addition, the frequency band value corresponding to the distance estimated in step 230 is also selected based on the stored value of the memory 34.

Thereafter, the central node 20 collects the requested frequency band information from the plurality of sensor nodes 10, allocates a suitable frequency band to each sensor node 10, and sends the allocated frequency information to the corresponding sensor node. Transmit (step 240). Accordingly, the data receiver 24 of the central node 20 is also set to the forward frequency band until step 240.

Thereafter, the sensor node 10 receives an ultrasonic signal carried in the frequency band f0 allocated to the forward frequency band from the central node 20 when transmitting and receiving underwater information with the central node 20, and the central node 20. ) Transmits the ultrasonic wave information with the underwater information in the frequency band allocated to the frequency band in the reverse frequency band.

In this process, an appropriate frequency band is adaptively allocated between the central node 20 and the plurality of sensor nodes 10 according to the distance information between the central node 20 and the sensor node 10 to perform underwater information communication. Therefore, in the present invention, since a proper frequency according to each distance is allocated to the plurality of sensor nodes 10 within a limited frequency band, an unusable sensor node is not generated due to an unreasonable allocation frequency. That is, underwater communication between the plurality of sensor nodes 10 and the central node 20 can be efficiently performed.

9 is a flowchart illustrating a method of underwater communication according to a second embodiment of the present invention. FIG. 9 is a control method used when the central node 20 allocates a specific frequency to the sensor node 10. The central node 20 estimates the distance from each sensor node 10 at its own discretion and estimates. A control process for allocating a frequency to each sensor node 10 according to the specified distance is shown.

First, the control unit 28 of the central node 20 checks all the available frequency bands and divides all the available frequency bands into a forward frequency band and a reverse frequency band as shown in FIG. 3 (300). step).

As shown in FIG. 4, the controller 28 performs control to divide the reverse frequency band into smaller frequency bands by the number of regions (M) (step 305). Steps 300 and 305 are preferably preset according to the performance of the central node 20. That is, when the central node 20 transmits and receives a signal in the underwater environment, the central node 20 stores the frequency that can be transmitted farthest in the forward frequency band. When the central node 20 transmits and receives a signal in the underwater environment, each frequency used in advance distinguishes and stores a distance (area) in which a signal can be transmitted. The divided distance and frequency values are stored in the memory 29 of the central node 20 and the memory 34 of the sensor node 10, and may be used later in the frequency setting process.

The controller 28 reads from the memory a reference signal to be used for detecting previously stored distance information. The reference signal is carried in a forward frequency band, and is converted into an ultrasonic signal and controlled to be transmitted from all sensor nodes 10 to the central node 20. The central node 20 receiving the reference signals transmitted from the plurality of sensor nodes 10 through the data receiver 24 detects the power strength of the received signal from each sensor node, the delay time used for the transmission time, and the like. do. The signal transmission / reception process for the detection signal is a state before the frequency band is allocated to the corresponding sensor node. Accordingly, the data transmitter 36 of the sensor node 10 and the data receiver 24 of the central node 20 transmit and receive signals using the frequency band set to the lowest frequency band among the reverse frequency bands (step 310). . On the other hand, it is also possible to perform a signal detection operation directly in the sensor node 10, and input the detection control information in the central node 20 to be used for subsequent distance estimation.

The central node 20 that detects the signal for distance estimation in step 310 is the distance between the central node and each sensor node using the power strength of the received signal of each sensor node and the time delay used for signal transmission. Estimate (step 320). At this time, the distance can be estimated using the distance value compared to the power strength previously stored in the memory 29. In addition, it is possible to estimate the distance using the distance value compared to the time delay previously stored in the memory 29.

Thereafter, the central node 20 adaptively allocates a frequency band suitable for each sensor node 10 according to the estimated distance, and transmits the allocated frequency information to the corresponding sensor node (steps 330 and 340). ).

Subsequently, the sensor node 10 receives an ultrasonic signal carried in the frequency band f0 allocated to the forward frequency band from the central node 20 when transmitting and receiving underwater information with the central node 20, and the central node 20. ) Transmits the ultrasonic wave information with the underwater information in the frequency band allocated to the frequency band in the reverse frequency band.

In this process, an appropriate frequency band is adaptively allocated between the central node 20 and the plurality of sensor nodes 10 according to the distance information between the central node 20 and the sensor node 10 to perform underwater information communication. Accordingly, the present invention enables efficient underwater communication between the plurality of sensor nodes 10 and the central node 20 within a limited frequency band.

10 is a flowchart illustrating an underwater communication method according to a third embodiment of the present invention. 10 illustrates a control method used when the central node 20 allocates a specific frequency to the sensor node 10. The embodiment of the present invention shows that the same frequency band can be set for the plurality of sensor nodes.

 The control unit 28 of the central node 20 checks all the available frequency bands and divides all the available frequency bands into a forward frequency band and a reverse frequency band as shown in FIG. ).

In addition, as shown in FIG. 4, the controller 28 performs a control to divide the reverse frequency band into smaller frequency bands by the number of regions (M) (step 405). Steps 400 and 405 may be preset according to the performance of the central node. That is, when performing the transmission and reception of signals in the underwater environment, the central node 20 includes the frequency that can be transmitted farthest in the forward frequency band and stores it. In addition, when performing the transmission and reception of the signal in the underwater environment, the central node 20 distinguishes and stores the distance (area) in which each frequency can transmit the signal in advance. The divided distance and frequency values are stored in the memory 29 of the central node 20 and the memory 34 of the sensor node 10, and may be used later in the frequency setting process.

The controller 28 reads from the memory 29 a reference signal to be used for detecting previously stored distance information. The reference signal is carried in the forward frequency band, is converted into an ultrasonic signal through the data transmitter 26, and transmitted to all the sensor nodes 10 included in all available frequency bands of the central node 20 (step 410). ).

The sensor nodes 10 receiving the reference signal transmitted in step 410 through the data receiver 38 detect the power strength of the received signal, and / or the time delay used for signal transmission, and detect the detected signal as a central node. 20). In the detection signal transmission process, since the frequency band is assigned to the corresponding sensor node, in this case, the detection signal is transmitted to the central node 20 using the lowest frequency band among the reverse frequency bands.

The control unit 28 of the central node 20 receiving the detection signal uses the power level of the received signal input from each sensor node and / or the time delay used for signal transmission, and the like. Estimate the distance with (step 420). At this time, the distance can be estimated using the distance value compared to the power strength previously stored in the memory 29. In addition, it is possible to estimate the distance using the distance value compared to the time delay previously stored in the memory 29.

Thereafter, the central node 20 adaptively allocates a frequency band suitable for each sensor node 10 according to the estimated distance (step 430). When assigning a frequency to the sensor node 10 in step 430, as shown in Figure 4, the same frequency band is assigned to the sensor node at the same or similar distance. At this time, the central node 20 binds the sensor node capable of transmitting and receiving signals in the same frequency band to the same area based on the reference. The same frequency band is allocated to the same area.

In operation 430, the frequency band information allocated to each region is transmitted to the plurality of sensor nodes.

When the sensor node 10 transmits and receives underwater information with the central node 20, the sensor node 10 receives an ultrasonic signal from the central node 20 in the frequency band f0 allocated to the forward frequency band, and the central node 20. The furnace loads the underwater information in the frequency band assigned to it in the reverse frequency band and transmits it as an ultrasonic signal.

On the other hand, sensor nodes existing in the same area have the same frequency band and the underwater signal is transmitted. Therefore, in this case, the control unit 28 in the central node 20 needs to appropriately control underwater communication with a plurality of sensor nodes existing in the same area. In this case, the underwater communication control according to the multiple access scheme is performed as described above (step 450).

In this way, the same frequency is allocated to several sensor nodes because the frequency band usable in the central node 20 is limited. For example, in order to acquire the underwater information more accurately and variously, the number of sensor nodes has to be increased. In this case, the number of sensor nodes 10 installed in the entire frequency band usable by the central node 20 may be larger than the divided number of reverse frequency bands. At this time, as shown in Figure 4, the sensor node existing in the same area is assigned the same frequency band to control the underwater communication.

According to the embodiment of FIG. 10, the present invention allocates the same frequency band to the plurality of sensor nodes 10 within a limited frequency band, and efficiently controls the plurality of sensor nodes by controlling the multiple access method of the central node 20. Controlling to perform underwater communication. Therefore, it is possible to efficiently control the underwater communication even for more sensor nodes than the number of divided frequency bands.

Meanwhile, a node to be used as a transmitting side and a node to be used as a receiving side are determined between the central node and any sensor node. According to an operation algorithm and operation method of underwater communication according to an embodiment of the present invention, the central node may operate as a transmitting side, and the sensor node may operate as a transmitting side. When the transmitting side is determined among the central node and the sensor node, the node communicating with the transmitting side is determined as the receiving side. For example, a node that first requests signal transmission may operate as the transmitting side, and the other side that is requested to transmit the signal may operate as the receiving side. That is, the central node and the sensor node can both transmit and receive, and are configured to be operated by the transmitting side or the receiving side according to the operating state.

In addition, as described above, a small frequency band to be used for underwater communication between the central node and any sensor node is allocated between the central node and any sensor node.

In a state where the transmitting node and the receiving node are determined, FIG. 11 shows the mutual relationship with the receiving side when the adaptive underwater communication method is determined at the node determined as the transmitting side.

First, a basic process of transmitting and receiving a reference signal is performed between the transmitting side TX and the receiving side RX to check the status of each other. This process may be referred to as a process of testing / confirming whether a signal can be transmitted and received, such as checking a channel to be used by the transmitting side and the receiving side. In this process, the transmitting side may determine to perform the adaptive underwater communication method based on the signal fed back from the receiving side.

In general, the situation of underwater communication is very flexible both temporally and spatially. Therefore, the situation of underwater communication is first determined through the process of sending and receiving reference signals between the transmitting side and the receiving side transmitting and receiving signals, and when there is a change in the underwater communication situation, the underwater communication method is immediately and adaptively adjusted accordingly. It is.

In determining the adaptive underwater communication method, various factors that may affect the underwater communication environment may be considered. These factors include seawater temperature, season, salinity, channel characteristic parameters, sender battery condition, delay spread, Doppler spread, Doppler scaling, signal to noise ratio, SNR, Signal to Interference Noise Ratio (SINR), Error Vector Magnitude (EVM), and the like. However, the factors affecting the underwater communication environment are not limited to those described, and of course, various factors may be considered.

When the adaptive underwater communication method is determined at the transmitting side, the transmitting side transmits information on the determined adaptive underwater communication method to the receiving side. When the receiving side confirms the transmitted adaptive underwater communication method, the transmitting side transmits the data to be transmitted to the receiving side according to the determined adaptive underwater communication method. In this case, the transmitting side may multiplex and transmit the information on the determined adaptive underwater communication method together with the data to be transmitted.

Fig. 12 shows the mutual relationship with the transmitting side when the adaptive underwater communication method is determined at the node determined as the receiving side in a state where the transmitting node and the receiving node are determined.

When the transmitting side transmits feedback information about the reference signal or the communication link to the receiving side, the receiving side determines the adaptive underwater communication method based on the received reference signal or the feedback information about the communication link, and the determined adaptive underwater Information on the communication method is provided to the sender. In this case, the transmitting side transmits the data to be transmitted to the receiving side according to the adaptive underwater communication method information transmitted by the receiving side. Here, the factors considered when the receiver determines the adaptive underwater communication method are the same as those in the case where the above-mentioned transmitter determines the adaptive underwater communication method, and thus repeated description is omitted.

13 and 14 are flowcharts illustrating an underwater communication method according to a fourth embodiment of the present invention. Here, FIG. 13 shows a control method for adaptively communicating with changes in the underwater environment, and FIG. 14 shows a method of determining frame structure parameters and determining communication parameters in the underwater communication method shown in FIG.

When the transmitting side or the receiving side determines the adaptive underwater communication method (step 502), it is first determined whether the underwater communication method is multi-frequency communication or single frequency communication. Here, the multi-frequency communication method is Orthogonal Frequency Division Multiplexing (OFDM), Filter Bank Multi Carrier (FBMC), Filtered Multi Tone (FMT), Universal filtered Multi Carrier (UFMC), Generalized Frequency Division Multiplexing (GFDM), SC-FDMA ( Single Carrier Frequency Division Multiple Access). In addition, the single frequency communication method may be a direct sequence spread spectrum (DSSS) communication method. However, the multi-frequency communication method or the single-frequency communication method is not limited to the described communication method, but may be various multi-frequency communication methods or a single frequency communication method.

When the multi-frequency communication method is determined (step 504), the transmitting side or the receiving side determining the adaptive underwater communication method determines a frame structure parameter according to the multi-frequency communication method (step 506).

In this case, the transmitting side or the receiving side may select a cyclic prefix (CP) according to the determined multi-frequency communication method (step 506-1). In this case, the transmitting side or the receiving side may select one CP among CPs having different lengths in consideration of the requirements of at least one underwater communication environment such as channel status, SNR, SINR, EVM, battery status, and the like. In this case, the CP may be selected using various selection criteria such as selecting the smallest CP among CPs larger than the delay spread value or selecting the largest CP when the delay spread value is larger than all selectable CPs. Channel conditions also include root mean square (RMS) delay spread, maximum delay spread, Doppler spread, Doppler scaling, Doppler shift, channel covariance matrix, etc. do.

In addition, the transmitting side or the receiving side determining the adaptive underwater communication method selects an interval of pilot symbols according to the determined multi-frequency communication method (step 506-2). In this case, the transmitting side or the receiving side may select the interval of the pilot symbol in the frequency and time domain, respectively, in consideration of the requirements of at least one underwater communication environment such as channel status, SNR, SINR, EVM, battery status, and the like. In this case, when the delay spread value is larger than the set value, the pilot interval in the frequency domain may be reduced, or when the Doppler spread value is large, the pilot interval in the time domain may be decreased, or the pilot symbol interval may be selected by combining various methods.

When the frame structure parameter is determined, the transmitting side or the receiving side determining the adaptive underwater communication method determines the communication parameter according to the multi-frequency communication (step 508). At this time, the transmitting side or the receiving side determines the number of repetitive transmissions for repetitive transmission of signals in underwater communication (step 508-1). In this case, the transmitting side or the receiving side may first determine the situation of the underwater communication through the process of sending and receiving the reference signal, and determine the number of repetitive transmissions to transmit the actual data. In this case, the transmitting side or the receiving side may determine the number of repetitive transmissions in the frequency and time domains in consideration of the requirements of at least one underwater communication environment such as channel status, SNR, SINR, EVM, battery status, and the like.

In addition, the transmitting side or the receiving side having determined the adaptive underwater communication method selects a modulation scheme and a code rate (step 508-2). In this case, the transmitting side or the receiving side may select a modulation scheme and a code rate within a preset modulation scheme and code rate in consideration of the requirements of at least one underwater communication environment such as channel condition, SNR, SINR, EVM, battery state, and the like. . In this case, the transmitting side or the receiving side uses a variety of criteria such as selecting a low level modulation method and a code rate when the delay spread value is large, or selecting a low level modulation method and a code rate when the Doppler spread value is large. And code rate can be selected.

The transmitting side and the receiving side apply underwater power control to perform underwater communication (steps 510 and 512). In this case, the power control method may use a known power control method, and a detailed description thereof will be omitted.

The transmitting side or the receiving side determines whether each time data is transmitted or received or periodically performed underwater communication satisfies the target performance (step 514). At this time, if the currently performed underwater communication satisfies the target performance, the underwater communication between the transmitting side and the receiving side is continuously performed by the current underwater communication method.

If the currently performed underwater communication does not satisfy the target performance, it is determined whether the current underwater communication satisfies a preset condition (step 516). Whether the current underwater communication meets the preset conditions may be applied by changing the channel status, SNR, SINR, EVM, battery status, etc., and whether the preset power control method is applied. Can be. The method of determining whether the present underwater communication meets a predetermined condition described herein has been described for the purpose of understanding, and besides, the present underwater communication can be judged by comparing with various reference conditions. In this case, if the current underwater communication meets a preset condition, it is determined that a change has occurred in the environment of the underwater communication, and accordingly, the method is repeatedly performed to determine the underwater communication method. In addition, if the current underwater communication does not meet the preset conditions, the communication is continuously performed by adjusting the power control method of the current underwater communication. To this end, it is preferable that the transmitting side or the receiving side sets and stores reference conditions for determining a change in the underwater communication environment.

When the single frequency communication method is determined (step 504), the transmitting side or the receiving side having determined the adaptive underwater communication method determines a frame structure parameter according to the single frequency communication method (step 518).

In this case, the transmitting side or the receiving side may select a spreading factor according to the determined single frequency communication method (step 518-1). In this case, the transmitting side or the receiving side may select one spreading factor among different spreading factors in consideration of the requirements of at least one underwater communication environment such as channel status, SNR, SINR, EVM, battery condition, and the like. In this case, the spreading factor may be determined in inverse proportion to the SNR, the SINR, the EVM, the battery state, or the like, or the spreading factor may be selected using various selection criteria.

In addition, the transmitting side or the receiving side determining the adaptive underwater communication method selects the density of pilot symbols according to the determined single frequency communication method (step 518-2). In this case, the transmitting side or the receiving side may select the density of the pilot symbols in the frame in consideration of the requirements of at least one underwater communication environment such as channel status, SNR, SINR, EVM, battery status, and the like. At this time, if the delay spread value is larger than the set value, the pilot symbol density is increased; if the Doppler spread value is larger than the set value, the pilot symbol density is decreased; The density of pilot symbols may be selected by selecting or combining various methods.

When the frame structure parameter is determined, the transmitting side or the receiving side determining the adaptive underwater communication method determines the communication parameter according to the single frequency communication (step 520). At this time, the transmitting side or the receiving side determines the number of repetitive transmissions for repetitive transmission of signals in underwater communication (step 520-1). In this case, the transmitting side or the receiving side may first determine a situation of underwater communication through a process of sending and receiving a reference signal, and determine the number of repetitive transmissions to transmit the actual data. In this case, the transmitting side or the receiving side may determine the number of repetitive transmissions in the time domain in consideration of the requirements of at least one underwater communication environment such as channel status, SNR, SINR, EVM, battery status, and the like. In addition, the number of repetitive transmissions may be selected by applying various methods such as selecting a larger number of repetitive transmissions as the delay spread value is larger or selecting a larger number of repetitive transmissions as the Doppler spreading value is larger.

In addition, the transmitting side or the receiving side determining the adaptive underwater communication method selects a modulation scheme and a code rate (step 520-2). In this case, the transmitting side or the receiving side may select a modulation scheme and a code rate within a preset modulation scheme and code rate in consideration of the requirements of at least one underwater communication environment such as channel condition, SNR, SINR, EVM, battery state, and the like. . In this case, the transmitting side or the receiving side selects a low level modulation scheme and a code rate when the delay spread value is larger than the set value, or selects a low level modulation scheme and code rate when the Doppler spread value is larger than the set value. The criteria can be used to select the modulation scheme and code rate.

Since the processes of steps 522 to 528 in the single frequency communication method are the same as steps 510 to 516 in the multi-frequency communication method, detailed descriptions thereof are omitted here.

Although embodiments according to the present invention have been described above, these are merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent embodiments of the present invention are possible therefrom. Therefore, the protection scope of the present invention should be defined not only by the following claims, but also by their equivalents.

10: sensor node 20: center node
21, 22, 40: transceiver 23, 26, 36: data transmitter
24, 25, 38: data receiver 27: frequency divider
28, 32: control unit 29, 34: memory

Claims (24)

In the underwater communication method of the underwater communication system comprising a plurality of sensor nodes for detecting underwater information, and a central node for collecting and transmitting the underwater information detected by each of the sensor nodes,
(a) determining a multi-frequency communication scheme or a single frequency communication scheme;
(b) determining a frame structure parameter corresponding to the determined communication scheme;
(c) determining a communication parameter corresponding to the determined communication method;
(d) performing communication by applying a power control scheme; And
(e) determining whether the communication performance satisfies the target performance, and determining whether or not the predetermined condition is met when the communication performance does not satisfy the target performance;
It includes, step (b),
(b-1) selecting a cyclic prefix (CP) when the multi-frequency communication scheme is determined; And
(b-2) selecting an interval of pilot symbols;
Including,
Underwater communication method characterized in that for performing the underwater communication adaptive to the underwater environment according to the result determined by step (e).
The method of claim 1,
If the set condition is met, the method of underwater communication, characterized in that performing step (a) again.
The method of claim 1,
If it does not meet the set condition, the underwater communication method characterized in that to perform the step (d) again to control the power.
The method of claim 1,
If the target performance is satisfied, the underwater communication method characterized in that for performing communication by maintaining the current power control method and communication method.
The method of claim 1,
Underwater communication method characterized in that the transmitting side of the plurality of the sensor node and the central node determines to perform the adaptive underwater communication.
The method of claim 5,
And wherein the transmitting side determines to perform adaptive underwater communication based on the reference signal transmitted from the receiving side or feedback information about the communication link transmitted from the receiving side.
The method of claim 5,
And said transmitting side transmits the adaptive underwater communication information and communication data by multiplexing.
The method of claim 1,
Underwater communication method characterized in that the receiving side of the plurality of the sensor node and the central node determines the performance of the adaptive underwater communication.
The method of claim 8,
And the receiving side determines to perform adaptive underwater communication based on the reference signal transmitted from the transmitting side or feedback information on the communication link transmitted from the transmitting side.
The method of claim 1,
In step (a),
An underwater communication method comprising determining a communication method based on at least one of a channel condition, a battery state, a signal to noise ratio (SNR), a signal to interference noise ratio (SINR), and an error vector magnitude (EVM).
The method of claim 1,
The multi-frequency communication method is Orthogonal Frequency Division Multiplexing (OFDM), Filter Bank Multi Carrier (FBMC), Filtered Multi Tone (FMT), Universal filtered Multi Carrier (UFMC), Generalized Frequency Division Multiplexing (GFDM), SC-FDMA (Single) Underwater communication method, characterized in that one of the Carrier Frequency Division Multiple Access.
The method of claim 1,
The single frequency communication method is one of the communication method including a DSSS (Direct Sequence Spread Spectrum).
delete The method of claim 1,
Step (b-1),
And selecting one CP among CPs having different lengths based on at least one of a channel condition, an SNR, an SINR, an EVM, and a battery condition.
The method of claim 1,
Step (b-2),
And selecting intervals of pilot symbols in the frequency and time domains, respectively, based on at least one of channel conditions, SNRs, SINRs, EVMs, and battery conditions.
In the underwater communication method of the underwater communication system comprising a plurality of sensor nodes for detecting underwater information, and a central node for collecting and transmitting the underwater information detected by each of the sensor nodes,
(a) determining a multi-frequency communication scheme or a single frequency communication scheme;
(b) determining a frame structure parameter corresponding to the determined communication scheme;
(c) determining a communication parameter corresponding to the determined communication method;
(d) performing communication by applying a power control scheme; And
(e) determining whether the communication performance satisfies the target performance, and determining whether or not the predetermined condition is met when the communication performance does not satisfy the target performance;
It includes, step (b),
(b-3) selecting a spreading factor when the single frequency communication scheme is determined; And
(b-4) selecting the density of the pilot symbol;
Including,
Underwater communication method characterized in that for performing the underwater communication adaptive to the underwater environment according to the result determined by step (e).
The method of claim 16,
Step (b-3),
And a spreading factor of one of different spreading factors, based on at least one of a channel condition, an SNR, an SINR, an EVM, and a battery state.
The method of claim 16,
Step (b-4) is,
And selecting a density of a pilot symbol in a frame based on at least one of a channel condition, an SNR, an SINR, an EVM, and a battery condition.
The method according to claim 1 or 16,
In step (c),
(c-1) selecting the number of repetitive transmissions; And
(c-2) selecting a modulation scheme and a code rate;
Underwater communication method comprising a.
The method of claim 19,
Step (c-1),
And selecting the number of repetitive transmissions in the frequency and time domains based on at least one of channel conditions, SNRs, SINRs, EVMs, and battery conditions when the multi-frequency communication scheme is selected.
The method of claim 19,
Step (c-2),
And a predetermined modulation scheme and a code rate based on at least one of a channel condition, an SNR, an SINR, an EVM, and a battery state.
The method of claim 19,
Step (c-1),
And selecting the number of repetitive transmissions in the time domain based on at least one of channel conditions, SNRs, SINRs, EVMs, and battery conditions when the single frequency communication scheme is selected.
delete delete

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