KR102045110B1 - Apparatus for repetitive transmission of underwater communication and method thereof - Google Patents

Abstract

The present invention relates to underwater communication, and more particularly, to a signal transmission apparatus and method for controlling repetitive transmission of a transmission signal in time / frequency in underwater communication. According to the present invention, when performing underwater communication between the central node and an arbitrary sensor node using the allocated small frequency bands, the allocated small frequency bands are divided into N1 time dimensions and a frequency dimension according to a predetermined algorithm. N1 * M1 repetitive transmissions of the same data are divided into M1 pieces.

Description

Repetitive transmission apparatus and method in underwater communication {APPARATUS FOR REPETITIVE TRANSMISSION OF UNDERWATER COMMUNICATION AND METHOD THEREOF}

The present invention relates to underwater communication, and more particularly, to a repeating transmission apparatus and method for controlling repetitive transmission of a transmission signal in time / frequency in underwater communication.

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. The underwater communication uses ultrasonic waves to perform communication. The communication network for underwater information transmission comprises a sensor node capable of transmitting and receiving underwater information in an underwater environment, and acquiring and controlling underwater information from the sensor node.

Due to the underwater communication environment using ultrasonic waves, the underwater communication network has a relatively small bandwidth of a transmitted signal and a large signal attenuation over distance compared to land communication. In other words, the frequency used in the underwater communication network is very limited in order to perform reliable communication at a distance of several kilometers to several tens of kilometers.

In addition, when the demand for underwater information acquisition using an underwater communication network increases, the number of sensor nodes that perform communication underwater increases. However, in the conventional underwater communication network, due to the limitation of the frequency that can be used in the underwater channel environment, the plurality of sensor nodes could not be efficiently controlled.

That is, when performing communication using only one frequency in the conventional underwater communication network, if the corresponding frequency is assigned to one sensor node, all other sensor nodes could not transmit or receive signals.

In addition, when performing communication using a plurality of frequencies in a conventional underwater communication network, if the number of sensor nodes that want to communicate underwater is greater than the assigned frequency, the number of underwater sensor nodes that exceed the allocated frequency transmits and receives signals. I could not. Moreover, in this case, since all sensor nodes must constantly check which frequencies are allocated to the sensor nodes in the vicinity, the battery consumption in the water is greatly increased and the operating period of the underwater sensor nodes is greatly reduced.

Therefore, in the conventional underwater communication network, the plurality of sensor nodes cannot be managed efficiently, thereby limiting the number of sensor nodes that can communicate. In addition, the increase in the number of sensor nodes is inevitable due to the increased demand for marine information, and in many areas, efficient control of the underwater communication network is required.

In addition, underwater communication is very unstable in signal transmission compared to land communication. There are many reasons for this, but for example, the Doppler frequency caused by tidal currents, waves, etc. is affected by the time base. In addition, due to various multipaths due to sea level, sea level, and terrain, the frequency axis may be affected, and the speed of sound waves depending on the depth of the sea also affects underwater communication. Factors such as salinity, sea temperature, season and time also affect underwater communications. As described above, underwater communication is unstable due to various factors, and this instability degrades the demodulation performance of receiving and demodulating an actual signal.

Accordingly, an object of the present invention is to provide a repetitive transmission apparatus and method for controlling repetitive transmission of a transmission signal in time / frequency resources in underwater communication.

Another object of the present invention is to provide a repetitive transmission apparatus and method for variably controlling repetitive transmission of a transmission signal according to a current underwater characteristic when performing underwater communication using a limited frequency in an underwater communication network.

Another object of the present invention is to divide the limited frequency bandwidth of an underwater communication network into a plurality of smaller bandwidths, and to perform efficient underwater communication using a large number of sensor nodes by allocating the same frequency to a plurality of sensor nodes having similar communication distances. In order to provide a repetitive transmission apparatus and method for controlling a repetitive transmission of a transmission signal in accordance with current underwater characteristics.

In order to solve the above technical problem, the repetitive transmission method of underwater communication according to an embodiment of the present invention, underwater using a central node that collects the detection information from a plurality of sensor nodes for detecting underwater information and transmits it to the ground network In communication,

Split the entire frequency band available to the central node into small frequency bands, and perform the underwater communication by allocating the divided small frequency bands to the respective sensor nodes based on the distance between the central node and the plurality of sensor nodes. ,

When performing underwater communication between the central node and any sensor node using the respective allocated small frequency bands, the allocated small frequency bands are set to N1 time dimensions and M1 frequency dimensions according to a predetermined algorithm. And repeating transmission of N1 * M1 times for the same data.

In the repeated transmission method of underwater communication according to another embodiment of the present invention, in the underwater communication using the central node that collects the detection information from the plurality of sensor nodes for detecting the underwater information and transmits it to the terrestrial network,

Split the entire frequency band available to the central node into small frequency bands, and perform the underwater communication by allocating the divided small frequency bands to the respective sensor nodes based on the distance between the central node and the plurality of sensor nodes. ,

Based on the value of the underwater characteristic obtained through the test signal for the allocated small frequency band, the time dimension is divided into N2 and the frequency dimension into M2, and the same data is controlled for repeated transmission within the range of N2 * M2 times. It is characterized by.

Preferably, the repetitive transmission of the same data is characterized by controlling repetitive transmission by applying different interleaving rules.

Preferably, the repetitive transmission of the same data is characterized by controlling repetitive transmission by applying different scrambling rules.

Preferably, the repetitive transmission of the same data is characterized by controlling repetitive transmission by applying different precoding rules.

In order to solve the above technical problem, the repetitive transmission apparatus for underwater communication according to an embodiment of the present invention, underwater using a central node that collects the detection information from a plurality of sensor nodes for detecting the underwater information and transmits the detection information to the terrestrial network In communication,

Divide the entire frequency band available to the central node into small frequency bands, and perform the underwater communication by allocating the divided small frequency bands to the respective sensor nodes based on the distance between the central node and the plurality of sensor nodes; ,

When performing underwater communication between the central node and any sensor node using the respective allocated small frequency bands, the allocated small frequency bands are set to N1 time dimensions and M1 frequency dimensions according to a predetermined algorithm. The method is characterized in that N1 * M1 repetitive transmissions are performed for the same data.

According to another embodiment of the present invention, an iterative transmission apparatus for underwater communication includes, in underwater communication using a central node that collects detection information from a plurality of sensor nodes for detecting underwater information and transmits the detected information to a terrestrial network.

Divide the entire frequency band available to the central node into small frequency bands, and perform the underwater communication by allocating the divided small frequency bands to the respective sensor nodes based on the distance between the central node and the plurality of sensor nodes; ,

When performing underwater communication between the central node and any sensor node using the respective assigned small frequency bands, based on the value for the underwater characteristic obtained through the test signal, the assigned small frequency band, the time dimension N2 and the frequency dimension are divided into M2, and N2 * M2 repetitive transmissions are performed on the same data.

Preferably, the central node determines the number of repetitive transmissions, and transmits the determined number of repetitive transmissions to the sensor node.

Preferably, the sensor node determines the number of repetitive transmissions, and transmits the determined number of repetitive transmissions to the central node.

According to the present invention, an apparatus and method for transmitting a signal for underwater communication include an appropriate frequency band allocated according to distance information between a central node 20 and a plurality of sensor nodes 10, and carried on a carrier when underwater information communication is performed. By repeatedly transmitting the transmission signal to match the current underwater environment, the effect of improving the reception performance between the plurality of sensor nodes 10 and the central node 20 is obtained.

In addition, the apparatus and method for transmitting a signal for underwater communication according to the present invention allocates the same frequency band to a plurality of sensor nodes 10 within a limited frequency band, and controls a plurality of central nodes 20 under the control of a multiple access method. While performing the underwater communication by efficiently controlling the sensor nodes, by repeatedly transmitting the transmission signal carried on the carrier to match the current underwater environment, it is possible to increase the diversity gain of the receiver.

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 for conceptually illustrating a centrally controlled underwater communication network implemented to explain the 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.
5 is a diagram illustrating a schematic configuration diagram for explaining the underwater communication method according to an embodiment of the present invention as a whole.
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 an operation of the underwater communication method according to an embodiment of the present invention.
9 is a flowchart illustrating an operation of the underwater communication method according to an embodiment of the present invention.
10 is a flowchart illustrating an operation of the underwater communication method according to an embodiment of the present invention.
11 to 13 are exemplary diagrams of frequency / time resources for explaining repeated transmission of a signal in underwater communication of the present invention;
15 to 17 show a relationship between a transmitter and a receiver for determining the number of repetitive transmissions in the underwater communication of the present invention.
18 is a block diagram showing a part of the configuration of the transmitting side when repeatedly transmitting a signal in the underwater communication of the present invention.
19 is a block diagram showing a part of the configuration of the receiving side when repeatedly transmitting a signal in the underwater communication of the present invention.
20 is a flowchart illustrating an operation for repeatedly transmitting and controlling a signal in underwater communication according to the present invention.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings, and the same or similar components are denoted by 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 mixed in consideration of ease of specification, and have meanings or roles that are distinct from each other. It 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 referred to as being "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 between. 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 view showing a general underwater communication network used in the underwater communication shown to help the 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 shown. It is configured to include.

In the underwater communication network configured as described above, the transmission of underwater information is performed as follows. The sensor node 1 to transmit the underwater information detected from the plurality of sensor nodes 1 transmits the underwater information to the sink node 5 through the intermediate node 3 composed of several steps.

However, the underwater communication network configured in this way must pass through the intermediate node 3 in 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, when the transmission error occurs in the process of transferring the underwater information from the sensor node 1 to the sink node 5, the underwater communication network is cumbersome to retransmit the detected underwater information.

In addition, the underwater communication network has to go through the intermediate node (3) of the various stages, and if a problem occurs in the intermediate node for conveying underwater information, the sensor node associated with the intermediate node in which the problem occurs is not used.

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. By improving these points, the present invention seeks to implement a centrally controlled underwater communication network.

In the following description of the present invention, "frequency band" and "frequency" may be used interchangeably. The "frequency" refers to a frequency included in the "frequency band," and since the frequency carries almost the same signal on a frequency included in a predetermined range of the frequency, the two words may be expressed with the same meaning.

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

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

The central control underwater communication network includes one or more sensor nodes 10. The sensor node 10 is installed to be fixed or movable in the underwater environment. The sensor node 10 is provided as much 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 by the plurality of sensor nodes 10. 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 configured as described above 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 exemplary embodiment of the present invention.

Referring to the drawings, underwater communication between the central node 20 and the plurality of sensor nodes 10 is basically performed by ultrasonic waves. In addition, 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 refers to a frequency band included in an area where underwater communication is possible between the central node 20 and the sensor node 10 provided at different distances. That is, the signal can be transmitted from the central node 20 to the sensor node 10 installed at an arbitrary position, and the frequency band used to receive the signal transmitted from the sensor node 10 can be received from the central node 20. Express.

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 signals from all sensor nodes regardless of the distance. Therefore, the frequency band f0 having the lowest frequency is determined as the forward frequency band, and is used when transmitting signals from the central node 20 to the plurality of sensor nodes 10.

The reverse frequency band is used to perform signal transmission from each of the plurality of sensor nodes 10 to the central node 20. Herein, all of the available frequency bands, except for the forward frequency band, are included in the reverse frequency band as a whole.

The reverse frequency band is further divided into a plurality of small frequency bands. In this case, dividing into smaller frequency bands, grouping the sensor nodes that can transmit and receive signals in the same frequency band between the distance to the sensor node with respect to the center node to the same area, the number of frequency bands as small as the number of divided areas (described later) M)

Each of the divided small frequency bands is allocated to be used for signal transmission of the sensor nodes 10 installed at different locations. For example, the frequency band f1 is allocated to the sensor node 10 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, on the basis of the central node 20, the sensor node 10 located at the farthest distance is assigned 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 based on the central node 20. As mentioned earlier, since the communication range increases as the frequency 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 using the frequency band to which the underwater information detected by the sensor node 10 is assigned. Underwater communication is carried out, in which transmission of.

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 detected underwater information to the central node 20. Therefore, if the conditions of the underwater communication network are allowed, it is possible to install the number of 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 a region capable of transmitting signals in the same frequency band. That is, the divided frequency band fM is equally allocated to the sensor nodes existing in the area 1 included in the closest distance with respect to the central node 20. The divided frequency bands f1 are equally allocated to the sensor nodes existing in the region M that is included at the longest distance with respect to the central node 20.

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

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 in which 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 is generated. At this time, as shown in Fig. 4, the sensor node existing in the same area is assigned the same frequency band 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 to which the same frequency band has been assigned can be controlled by various multiple access schemes ( 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 used to communicate with the central node 20. Detailed 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, a general 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.

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.

7 is a diagram illustrating 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. 5, the plurality of sensor nodes 10 collect underwater information and transmit it to the central node 20. In this case, transmission and reception of underwater information using ultrasonic waves, which enable signal transmission due to the characteristics of the medium, are performed between the plurality of sensor nodes 10 and the central node 20 in the underwater communication network 50. In addition, the sensor node 10 transmits its position data together with the central node 20 when the signal is transmitted. The location information of the sensor node 10 is preferably stored and stored in the sensor node 10 at the time when the sensor node 10 is installed at any position in the water. However, the position of the sensor node 10 is difficult to be fixed fixed due to the nature of the underwater environment. Therefore, although expressed as the position information, it is preferable to understand only the sensor node 10 identification information.

The central node 20 transmits the underwater information collected from the plurality of sensor nodes 10 to the ground. The central node 20 transmits the acquired underwater information to the management node 64 of the terrestrial communication network 60. Therefore, 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 to the terrestrial communication network 62 using a radio signal.

Referring to FIG. 6, the sensor node 10 modulates the data sensed by one or more sensor units 30 and each sensor unit 30 to collect data necessary in the water, and converts the data sensed into ultrasonic waves to a center. A data transmitter 36 for transmitting to the node 20, and a data receiver 38 for receiving and demodulating the ultrasonic signal transmitted from the central node 20. The data transmitter 36 and the data receiver 38 are included in the transceiver 40, and a controller 32 that performs control between the sensor unit 30 and the transceiver 40 is further included. And a memory 34 for storing various data and algorithms necessary for the overall operation control of the sensor node 10 and storing the underwater information detected from 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 by the analog signal into 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 basically a digital signal.

The transceiver 40 performs a function of transmitting or receiving data using ultrasonic 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 shown receives the underwater information transmitted from the central node 20 via the data receiving unit 38. At this time, in order to enable the reception of the signal transmitted from the central node 20, the data receiver 38 is set to a frequency included in the forward frequency band. In addition, the data transmission unit 36 is set to a specific frequency included in the frequency band allocated to it, and then transmits the information for transmission to the central node 20 on the set specific frequency. Therefore, the transceiver 40 includes a configuration in which the frequency is set under the control of the controller 32. This configuration is made by a known technique, so 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.

In addition, in the present invention, the sensor node 10 may be fixedly installed at a specific position in the underwater environment, but is inevitably moved in a predetermined area on the underwater environment due to the influence of the current. In this way, since the sensor node 10 is likely to move, the distance measurement with the central node 20 is preferably performed in real time at the time when the underwater information measurement is performed. However, if real-time control is unreasonable, it is also preferable to repeat the measurement at regular time intervals, avoiding the time for underwater communication. In this way, since the use frequency may be changed with respect to 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 variably control the set frequency. That is, the frequency for transmitting information is variably controlled according to the current position of the sensor node 10 so that the information to be transmitted can be transmitted to the central node 20. In addition, the movement position of the sensor node 10 may be made only within a specific radius capable of transmitting and receiving a signal with the central node 20, so as to prevent the risk of loss of the sensor node 10.

The control unit 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. do.

In addition, the controller 32 performs control for detecting a distance between the sensor node 10 and the central node 20. To this end, the control unit 32 includes a configuration capable of receiving a reference signal transmitted by the central node 20 for distance detection by the data receiving unit 38 and detecting a magnitude of the received power. 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. The received power magnitude detection configuration can be applied by various techniques including known power detectors. In addition, the current size can be easily detected by providing a current detecting resistor in the receiver. 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 34.

As another method for detecting the distance, the controller 32 may detect and use a delay time required to arrive at the sensor node 10 after transmitting a signal from the central node 20. For example, the delay time detection may be detected by comparing the time point information at which the central node 20 starts signal transmission with the point information point at which the signal arrives. In order to detect the arrival time information, the control unit 32 preferably includes a time counting function or the like. And distance estimation using the detected delay time can estimate distance using the distance value compared with the delay time previously stored in the said memory 34. FIG.

The memory 34 is used to store various types of information used or needed and detected by the sensor node 10. Detection information of the sensor unit 30 is also stored in the memory 34. In particular, when the distance detection is directly performed in the sensor node 10, the memory 34 stores various pieces of information to be used for distance detection. For example, information for determining the strength of the received power, information for detecting the delay time, information for determining the distance between the central node 20 and the sensor node 10 using the strength of the received power, and estimation Frequency band information and the like which are available for underwater communication are stored according to the distance information. The controller 32 performs a process of distance estimation, requesting a specific frequency band, and the like using various types of information stored in the memory 34.

Referring to FIG. 7, the central node 20 transmits and receives a signal between the sensor node 10 and the first transmission / reception unit 22 and the management node 64 to perform transmission and reception of an underwater signal by ultrasound. It is configured to include a second transceiver 21 for performing this. 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 types of information. The second transceiver 21 may be configured to be transmitted by ultrasonic waves or may be transmitted by a wireless signal according to 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 that can be used by the forward frequency band and the reverse frequency band, and dividing the reverse frequency band into smaller frequency bands. . The frequency divider 27 may be included in the first transceiver 22 because it is used when transmitting and receiving the underwater information with the sensor node 10.

As shown in Fig. 4, the frequency divider 27 is configured to be able 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 to divide the frequency of the frequency divider 27 into the corresponding frequency when transmitting and receiving a signal with an arbitrary sensor node 10. Control the transmission and reception of signals normally.

The data transmitter 26 in the first transceiver 22 is set to the forward frequency band f0 to enable signal transmission to all sensor nodes. 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 before frequency setting is made.

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, power management for each sensor node 10, multiple access control for the sensor node 10 that exists at a distance similar to the traffic control, and the sensor node 10 and the central node as needed Control for detecting the distance between 20 is performed. In the present invention, the distance detection process may be performed by the controller 32 of the sensor node 10, but the distance detection process may be performed by the controller 28 of the central node 20.

Accordingly, the control unit 28 receives the reference signal transmitted by the sensor node 10 for distance detection in the initial setting process in which the frequency of the sensor node is not set by the data receiving unit 24, and the magnitude of the received power. It includes a detectable configuration. 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. The received power magnitude detection configuration can be applied by various techniques including known power detectors. 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 easily detected 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 strength of the detected received signal may be estimated using the distance value compared to the power strength 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. For example, the delay time detection may be detected by comparing the time point information at which the sensor node 10 starts transmitting the 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 the distance estimation using the detected delay time, the distance can be estimated using the distance value compared to 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, when the distance detection is performed at the central node 20, the memory 29 stores various pieces of information to be used for distance detection. 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 and the like which is possible for underwater communication. 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 also includes control information for frequency division, and stores associated information such as a divided frequency band and a sensor node set therein. It also stores underwater information collected from sensor nodes.

8 is a control flowchart of the underwater communication method according to an embodiment of the present invention.

8 is an operation process according to the first control method used when the central node 20 allocates a specific frequency to the sensor node 10.

In the underwater communication network 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 identifies the entire frequency bands that can be used by itself, and divides the available frequency bands into a forward frequency band and a reverse frequency band, as shown in FIG. 3. (200 steps)

In addition, the control unit 28 performs control to divide the reverse frequency band into smaller frequency bands by the number of regions (M) shown in FIG. 4 (step 205). The steps 200 and 205 are preferably controlled to be 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 includes the frequencies that can be transmitted farthest in the forward frequency band and stores the signals. When the central node 20 transmits / receives a signal in an underwater environment, each frequency used in advance distinguishes a distance (area) in which a signal can be transmitted and stores 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 then used in the frequency setting process.

Then, the reference signal to be used for detecting previously stored distance information is read from the memory 29. The reference signal is loaded on 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, The receiver 38 of the sensor node 10 receives a reference signal (step 210).

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 (220). step). 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 own frequency band (step 230). In the case of requesting a specific frequency band in step 230, since the frequency band is assigned to the corresponding sensor node, in this case, the frequency band request signal is transmitted using the frequency band set as the lowest frequency band among the reverse frequency bands. It is done. 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 which is preset and stored.

Thereafter, the central node 20 collects the frequency band information requested from the plurality of sensor nodes 10, allocates a suitable frequency band to each sensor node 10, and assigns the allocated frequency information to the corresponding sensor node. To the side (step 240). Therefore, 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 loaded in a frequency band f0 allocated to a forward frequency band from the central node 20 when transmitting and receiving underwater information with the central node 20. In (20), the underwater information is loaded on the frequency band assigned to the user in the reverse frequency band and transmitted as an ultrasonic signal.

In this process, an appropriate frequency band is adaptively allocated according to the distance information between the central node 20 and the sensor node 10 between the central node 20 and the plurality of sensor nodes 10 to perform underwater information communication. Lose. Accordingly, in the present invention, since a proper frequency according to each distance is assigned 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, the underwater communication between the plurality of sensor nodes 10 and the central node 20 can be efficiently performed.

9 is a control flowchart of the underwater communication method according to an embodiment of the present invention.

9 is an operation process according to the second control method used when the central node 20 allocates a specific frequency to the sensor node 10. The illustrated embodiment is a control process for estimating the distance to each sensor node 10 at its own discretion and assigning a frequency to each sensor node 10 according to the estimated distance.

First, the control unit 28 of the central node 20 identifies the entire frequency bands that can be used by itself, and divides the total available frequency bands into a forward frequency band and a reverse frequency band, as shown in FIG. 3. (300 steps).

The control unit 28 performs a control to divide the reverse frequency band into smaller frequency bands by the number of regions (M) shown in FIG. 4 (step 305). The steps 300 and 305 may be controlled to be 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 includes the frequencies that can be transmitted farthest in the forward frequency band and stores the signals. When the central node 20 transmits / receives a signal in an underwater environment, each frequency used in advance distinguishes a distance (area) in which a signal can be transmitted and stores 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 then used in the frequency setting process.

The reference signal to be used for detecting the stored distance information is read from the memory. The reference signal is carried in the forward frequency band and converted into an ultrasonic signal so that the transmission operation is controlled 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. In the signal transmission / reception process for the detection signal, 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 a frequency band set to the lowest frequency band among the reverse frequency bands. (Step 310). On the other hand, the signal detection operation may be performed directly at the sensor node 10, and the detection control information may be input at 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 performed by using the power node of the received signal of each sensor node, the time delay used for signal transmission, and the like. The distance is estimated (step 320). At this time, the distance can be estimated by using the distance value compared to the power strength previously stored in the memory 29. It is also possible to estimate the distance using the distance value compared to the time delay already 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 loaded 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. 20) loads the underwater information in the frequency band assigned to it in the reverse frequency band and transmits it as an ultrasonic signal.

In this process, an appropriate frequency band is adaptively allocated according to the distance information between the central node 20 and the sensor node 10 between the central node 20 and the plurality of sensor nodes 10 to perform underwater information communication. Lose. 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 control flowchart of the underwater communication method according to an embodiment of the present invention.

10 is an operation process according to the third control method used when the central node 20 allocates a specific frequency to the sensor node 10. In the illustrated embodiment, a process diagram for showing that the same frequency band can be set for a plurality of sensor nodes is shown.

 The control unit 28 of the central node 20 checks all the frequency bands that can be used by itself, and divides the usable frequency bands into a forward frequency band and a reverse frequency band as shown in FIG. 400 steps).

In addition, the controller 28 controls to divide the reverse frequency band into smaller frequency bands by the number of regions M shown in FIG. 4 (step 405). The steps 400 and 405 are preferably controlled to be 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 includes the frequencies that can be transmitted farthest in the forward frequency band and stores the signals. When the central node 20 transmits / receives a signal in an underwater environment, each frequency used in advance distinguishes a distance (area) in which a signal can be transmitted and stores 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 then used in the frequency setting process.

Then, the reference signal to be used for detecting previously stored distance information is read from the memory 29. The reference signal is carried in the 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 ( Step 410).

The sensor nodes 10 that receive 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 in the 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. The distance to the node is estimated (step 420). At this time, the distance can be estimated by using the distance value compared to the power strength previously stored in the memory 29. It is also possible to estimate the distance using the distance value compared to the time delay already 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 nodes capable of transmitting and receiving signals in the same frequency band to the same region 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. 20) 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, the sensor node existing in the same area has 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 assigned 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, a case in which 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 is generated. At this time, as shown in Fig. 4, the sensor node existing in the same area is assigned the same frequency band to control 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. Underwater communication is carried out by controlling. Accordingly, efficient underwater communication control is possible even for more sensor nodes than the number of divided frequency bands.

As described above, in the efficient frequency communication using a plurality of sensor nodes within a limited frequency band, the carrier signal is transmitted using the allocated frequency, and the signal is transmitted to enhance the reception performance of the carrier signal. Let's take a look at the operation of transmitting repeatedly.

In the foregoing process, a frequency (or a frequency band or a small frequency band) to be used between the central node 20 and any sensor node 10 has been allocated. Thereafter, in transmitting the signal between the central node 20 and any sensor node 10, the frequency allocated above is used.

On the other hand, the underwater communication of the present invention uses the OFDM, FBMC, FMT scheme to carry data on a plurality of carriers. For example, a certain number of subcarriers may be allocated and used for a predetermined time.

In the following description, as an example, a process of performing underwater communication by applying the OFDM communication scheme will be described. 11 illustrates a physical resource block used in an OFDM communication scheme. That is, a certain number of subcarriers are allocated for a predetermined time in OFDM communication, which is called a physical resource block, and has both a time dimension and a frequency dimension.

As shown in the drawing, the data repeatedly transmitted is repeatedly transmitted N * M times by dividing the time / frequency resources allocated to the receiving node into N pieces and M pieces, respectively. Resources allocated to the receiving side may be continuous on time / frequency as shown in FIG. 12 or discontinuous as shown in FIG. When a minimum unit of a resource to which data is allocated is called a resource block, the resource block may include one or more resources in time / frequency.

14 shows an exemplary diagram for allocating resources when a signal is repeatedly transmitted using resources allocated to a receiving side.

As shown, the resources allocated to the receiver are divided into N _T pieces on the time axis and N _F pieces on the frequency axis, and the same data is divided into different resources for interleaving, different scrambling methods, and different free methods. Assign by applying coding.

In the illustrated embodiment, a total of 90 resource blocks have been allocated to the receiving side, and a case where a total of 3 * 5 = 15 repetitive transmissions are performed three times on the time axis and five times on the frequency axis is described.

In this case, transmission data is allocated to six resource blocks. The resource block group is transmitted three times on the time axis and five times on the frequency axis.

One transmission data allocated to each resource block group is allocated by applying different methods (interleaving, scrambling, precoding) to each resource block group.

In the underwater communication of the present invention, the most important parameter is a process of determining the number of repetitive transmissions.

As one embodiment, as shown in FIG. 15, the transmission side that transmits a signal is arbitrarily determined.

The node to be used as the transmitting side and the node to be used as the receiving side are determined between the central node and any sensor node. The central node may operate as the transmitting side or the sensor node may operate as the transmitting side according to the operation algorithm and operation method of the network. The node that is not the node determined to be the transmitting side is naturally determined to be the receiving node. For example, a node requesting signal transmission first may be operated as a transmitting side, and the other may be operated as a receiving side. That is, the central node and the sensor node includes a configuration capable of transmitting and receiving, and is configured to be operated to the transmitting side or the receiving side according to the operating state.

And as in the above-described process, 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. 15 is a process according to determining the number of times for repetitive transmission at the node side 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 described as a process of first verifying whether or not a signal can be transmitted and received, such as checking a channel used at a transmitting side and a receiving side. The transmitter determines the number of repetitions based on the signal fed back from the receiver in this process.

Typically the underwater communication situation is very fluid every hour. Therefore, the communication between the transmitter and the receiver for transmitting and receiving the signal first to determine the underwater communication situation through the process of transmitting and receiving, and to determine the number of repetitions to transmit the actual data.

In determining the repetition frequency, various factors that may affect the underwater communication (various parameters affecting the underwater communication including temperature, time, season, salinity, sea temperature, user input value, etc.) are applied. This determines the appropriate number of repetitions.

Therefore, in order to optimally control the number of repetitive transmissions in the present invention, a condition suitable for the current underwater situation should be found. In finding this condition, it can generate | occur | produce according to the program set autonomously by a transmitter or a receiver. At this time, as a variable for determining the number of repetitive transmission, in addition to the above-described parameters, the channel characteristics, the signal-to-noise ratio (or interference ratio) of the received signal, the bit error rate, the packet error rate, and the number of retransmissions may be applied.

In the underwater communication, signal transmission is closely related to the length of the underwater channel (the number of multipaths) and closely related to how quickly the underwater channel changes in time (Doppler frequency). Therefore, when the receiver measures the channel characteristics and transmits the measured channel characteristics to the transmitter, the transmitter may determine the number of repetitive transmissions using the feedback information.

Therefore, in determining the number of repetitive transmissions, the length of the channel, Doppler frequency, RSSI, RSRP, RSRQ, bit error rate, packet error rate, noise level, and the subject that determines the number of repetitive transmissions are different depending on whether it is the transmitting side or the receiving side. Can be done.

As an example, when the underwater channel is severely changed in the frequency axis, it is possible to increase the number of repetitions (N _F ) in the frequency axis so as to obtain a frequency diversity gain at the receiver. In addition, when the underwater channel is severely changed on the time axis, it is possible to control the frequency diversity gain on the receiving side by increasing the number of repetitions N _T on the time axis. As another example, when the noise level of the reception channel is increased, the data detection performance at the receiver may be improved by controlling to increase the number of repetitions. As another example, when the interference level (adjacent cell, adjacent frequency channel, etc.) on the communication link increases, it is possible to control such that data detection performance is improved at the receiving side through control of increasing the number of repetitions for transmitting signals.

In addition, when the size of the received signal (RSSI, RSRP, RSRQ, etc.) decreases, or the bit error rate, packet error rate, retransmission, etc. increases, the signal is repeatedly transmitted in the time axis or the frequency axis or both the time axis and the frequency axis to improve channel estimation performance. Control to increase the number of times can be performed. Therefore, the control of the number of repetitive transmissions may be determined through an algorithm that is preset in the transmitting side. However, the underwater characteristic of the various variable values mentioned above is detected through a test signal, and the detected variable values are determined. You can also set the value for and save it, and apply it using it. The test signal may be performed by adopting a general reference signal transmission method.

When the number of repetitive transmissions is determined by the various parameters as described above, the determined number of repetitive transmissions is then transmitted to the receiving side, and when the receiving side confirms sufficiently, the data to be transmitted is subsequently determined. Will be transmitted repeatedly.

That is, FIG. 15 has described a process of determining the number of repetitive transmissions based on a reference signal transmitted from a receiving side or feedback information about a communication link transmitted from the receiving side.

Next, FIG. 16 is an exemplary diagram illustrating a process of determining a number of repetitive transmissions at a receiving side.

When the transmitting side transmits feedback information about the reference signal or communication link to the receiving side, the receiving side determines the number of repetitive transmissions by receiving and analyzing the received signal, and provides the determined repetitive number of transmission information to the transmitting side. The signal is transmitted as many times as the repeated transmission.

In order to determine the number of repetitive transmissions on the receiving side and notify the transmitting side as shown in FIG. 16, the receiving side must have information corresponding to various parameters and setting values according to the above-described description of FIG. 15. do. In order to satisfy such a part, one method is to pre-store parameter information for determining the number of repetitive transmissions in a memory (not shown) of the receiver.

Next, FIG. 17 is an exemplary diagram for describing a process according to when retransmission is needed after determining the number of repetitive transmissions and performing retransmission of a signal by the determined number of repetitive transmissions.

That is, in this case, the signal has been repeatedly transmitted as many as the predetermined number of repetitive transmissions. However, when an error occurs, it is preferable to increase the number of repetitive transmissions for retransmitted data.

In this case, the increase in the number of repetitive transmissions may be increased by a predetermined promise or transmitted in advance by the transmitting side through a broadcasting channel. Alternatively, the repetitive transmission number information may be previously transmitted to the receiver before data transmission for retransmission.

15 to 17, the repeated number of transmission information is preferably transmitted in the physical layer or MAC layer. In case of transmitting through the physical layer, it is preferable to transmit through a broadcasting channel, a control channel, or a data channel. The information on the number of repetitive transmissions may be independently defined and transmitted, or may be transmitted in combination with other information. For example, it may be transmitted in one of the Modulation and Coding Scheme (MCS) levels.

According to a general technique, the MCS (Modulation and Coding Scheme: MCS) table selects a modulation order and a coding rate corresponding to the corresponding MCS index in the MCS lookup table by using feedback information such as an MCS index returned from a receiver. Done. Therefore, there is also a method of determining, storing and using the number of repetitive transmissions based on the feedback information of the MCS index.

In addition, in transmitting the repetitive transmission information in FIGS. 15 to 17, the time axis repetition number and the frequency axis repetition number may be directly transmitted with respect to the repetitive transmission number information, and index information of the corresponding value among the predetermined values may be transmitted. It may be. In this case, the index information may be expressed as information to help the user know the number of times of repetition of the time axis or the number of times of repetition of the frequency axis. That is, it is information that can recognize the number of repetitive transmissions that are exchanged with each other through a predetermined appointment between the transmitting side and the receiving side. Through this information, the repetitive transmission number information determined by the receiving side or the repetitive transmission number information determined by the transmitting side is transmitted to the counterpart, and the data repetitive transmission by that much is then controlled.

Next, FIG. 18 illustrates a partial configuration of a transmitter for transmitting a signal repeatedly in the underwater communication of the present invention, and FIG. 19 illustrates a partial configuration of a receiver for enabling repetitive transmission in the underwater communication of the present invention. Doing.

The configuration of the transmitting side may be the central node described above or may be a sensor node. Although not shown, it may be an underwater base station. That is, in performing underwater communication, it is a structure provided in a transmitting side. Similarly, the configuration of the receiving side may be a central node or a sensor node or an underwater base station not shown. That is, in performing underwater communication, it is a component included in a receiving side.

The present invention transmits to the receiving side using the transmission data of the OFDM scheme. However, the repeated transmission of the same data causes a large PAPR in time / frequency and is vulnerable to interference between adjacent cells. In order to solve this problem, according to the present invention, when data is repeatedly transmitted, different types of interleaving, different types of scrambling, different types of precoding are performed, and the same data is combined and transmitted.

Therefore, as shown in FIG. 18, the transmitting side of the present invention includes a FEC encoder 600 which performs FEC (Fward Error Correction) encoding according to the OFDM scheme, and interleaves the output signals of the FEC encoder in different schemes. It includes a plurality of interleavers (601 to 604) that are algorithms to enable this. And a plurality of scramblers 605 to 608 that are algorithms to enable different types of scrambling. And a plurality of modulation units 609 ˜ 612 performing modulation operations for enabling transmission of the plurality of scrambling output signals according to an OFDM modulation scheme. And a plurality of precoders 613 to 616 which are algorithms for precoding the output signals of the plurality of modulators in different manners. And a mapper 620 for mapping the precoded signal for transmission. The signal thus mapped is transmitted through the transmit antenna.

The interleaving rule is applied through any one of a plurality of interleavers composed of different algorithms shown in FIG. 18, and the plurality of interleavers may be used sequentially or randomly. Of course, in order to control the deinterleaving operation at the receiving side, the receiving side should also be aware of the information on the order of use of the plurality of interleavers.

The interleaver has the same characteristics as a known interleaver, but referring to an embodiment, the output bits c (n), n = 0, ..., L-1 of the FEC encoder 600 are N _T = 3 on the time axis. Times, N _{F on the} frequency axis = 5 times, 15 times a total of 15 times (3 * 5), the bit C _i (n) to be repeatedly transmitted the i-th it is determined as follows.

If the bit that passed the interleaver in the i iterative transmission is d _i (n),

d _i (n) = c _i (l _q (n)).

Where l _q () is the q th interleaver pattern in the interleaver pattern table. Therefore, l _q (n) is the original position of the nth interleaved bit.

The interleaver pattern index q for each repetitive transmission may be determined as a symbol / slot / subframe / frame index to which the corresponding data is allocated, a subcarrier / resource block index to which the corresponding data is allocated, and a repetition index. That is, it is possible to select an interleaving method between the receiving side and the transmitting side based on the above data fed back from the receiving side.

Ex) q = i → In the case of the third repeated transmission bit, the interleaver pattern corresponding to the third column of the interleaver pattern table is applied.

The application of the scrambling rule is made through one of a plurality of scramblers composed of different algorithms shown in FIG. 18, and may use a plurality of scramblers sequentially or randomly. Of course, in order to control the descrambling operation on the receiving side, the receiving side should also be aware of the information on the order of use of the plurality of scramblers.

The scrambler has the same characteristics as a known scrambler, but in one embodiment, scrambling is applied to the output d _i (n) of the interleaver in the i-th iterative transmission.

e _i (n) = (s (n) + d _i (n)) mod2, where s (n) is the scrambling bit.

The scrambling bit has an initial value and is generated by a pseudo random sequence (PRS) generator provided in the scrambler.

The initial value Cinit (i) of the PRS generator in the i-th iterative transmission may be determined as a symbol / slot / subframe / frame index to which the data is allocated, a subcarrier / resource block index to which the data is allocated, and a repetition index. In other words, it is possible to select a scrambling method between the receiving side and the transmitting side based on the data fed back from the receiving side.

Example) Cinit (i) = n _sf * 2 ⁹ + n _s * 2 ⁴ + ID * 2 ₃ + i

Where n _{sf and} n _s are subframe indexes, ID is a receiving node ID, and i represents a repetitive transmission index of a corresponding bit.

The precoding rule is applied through any one of a plurality of precoders composed of different algorithms shown in FIG. 18, and may use a plurality of precoders sequentially or randomly. Of course, in order to control the deprecoding operation at the receiving side, the receiving side should also be aware of information on the order of use of the plurality of precoders.

The precoder has the same characteristics as the known precoder, but referring to an embodiment, the modulator output symbol * (n) is applied as follows in the i-th iterative transmission.

pj (n, k) is an element of the n th row and the k th column of the q th precoding matrix in the precoding matrix table. For each repetitive transmission, the precoding matrix index j may be determined by a value of a symbol / slot / subframe / frame index to which the data is allocated, a subcarrier / resource block index to which the data is allocated, and a repetition index. In other words, it is possible to select a precoding scheme between the receiving side and the transmitting side based on the above data fed back from the receiving side. In this case, it may be desirable to determine the index value in a manner that the receiving side may most prefer.

Example) j = i → In the case of the third repeated transmission bit, the third precoding matrix is applied in the precoding matrix table.

As described above, the present invention repeatedly transmits a signal, and the interleaving method, the scrambling method, and the precoding method for each repetition number include various parameters (symbol / slot / subframe / frame index to which the corresponding data is allocated and subcarriers to which the corresponding data is allocated). Resource block index, and the value of the iteration index). And a control unit (not shown) that performs control of the interleaver, scrambler, modulator, and precoder with a control value determined from values of the various parameters. In FIG. 18, only the lines to which the control value determined by the values of the parameters are applied to the interleaver 604, the scrambler 608, and the precoder 616 are shown. However, all the interleaver, all the scramblers, It goes without saying that a control value determined by the values of the parameters is applied to all precoders.

19, the receiving side of the present invention includes a demapper 700 for receiving and demapping the OFDM signal transmitted from the transmitting side. The demapping data is sequentially deprecoded, demodulated, descrambled, and deinterleaved. Therefore, a plurality of deinterleavers 713 to 716 for decoding the interleaving rule of the transmitting side are provided at the receiving side, and a plurality of descramblers 709 to 712 for decoding the scrambling rule of the received signal are provided. A plurality of OFDM demodulators 705 to 708 and a plurality of deprecoders 701 to 704 are included. The signal passing through the plurality of deinterleavers is input to the FEC decoder 730 through a Log-Likelihood Ratio (LLR) combining unit 720. The FEC decoder 730 restores the input data.

In addition, the receiving side may control the D as a control value determined by the various parameters (symbol / slot / subframe / frame index to which the corresponding data is assigned, subcarrier / resource block index to which the corresponding data is assigned, and the value of the repetition index). A control unit (not shown) for controlling the interleaver, descrambler and deprecoder is further included. At this time, the control value of the deinterleaver, the descrambler, and the deprecoder is a value set from a controlled value determined when the transmitter controls the interleaver, the scrambler, and the precoder. In FIG. 19, only the lines to which the control value determined by the values of the parameters are applied to the deinterleaver 716, the descrambler 712, and the deprecoder 704 are illustrated. Of course, all descramblers and all deprecoders are granted control values determined by the values of the parameters.

Next, as described above, a carrier signal is transmitted using an allocated frequency in an efficient underwater communication using a plurality of sensor nodes within a limited frequency band, and the same data is repeatedly transmitted to improve reception performance of the carrier signal. Let's look at the behavior.

20 is a flowchart illustrating an operation of controlling repetitive transmission for the same data during data transmission according to the present invention.

In the foregoing process, a frequency (or a frequency band or a small frequency band) to be used between the central node 20 and any sensor node 10 has been allocated. Thereafter, in transmitting the signal between the central node 20 and the arbitrary sensor node 10, the small frequency band allocated above is used (step 800).

That is, in the present invention, a control is performed to increase the diversity gain in the receiver by repeatedly transmitting the same data on a time and / or frequency dimension in a small frequency band allocated to each sensor node.

First, the number of repetitive transmissions is determined. The number of repetitive transmissions is determined according to the algorithms and underwater characteristics set at the transmitting side or the receiving side as described in the processes of FIGS. 15 to 17. In operation 810, a process of transferring the repetitive transmission number information from the transmitting side (or the receiving side) to the receiving side (or the transmitting side) determined such that the determined repetitive number of times information is recognized by both the transmitting side and the receiving side is performed.

The time axis is divided into N _T and the frequency axis is divided into N _F for the small frequency band allocated in step 800. As in the embodiment shown in Fig. 14, when a small frequency band allocated to the receiving side is allocated to 90 resource blocks, for example, if the number of repetitive transmissions is determined to be 15, 3 times on the time axis, Repeated transmission five times to divide the resources of the time axis and the frequency axis to enable a total of 3 * 5 = 15 times of repeated transmission (step 820).

On the contrary, it is also possible to divide the resources of the time base and the frequency base so that 5 times in the time axis and 3 times in the frequency axis can be repeatedly transmitted so that 5 * 3 = 15 times can be repeatedly transmitted. In this case, it is preferable to adjust the direction in which the data detection performance of the received signal can be improved according to the underwater characteristics.

Next, in the situation where the number of repetitive transmissions is determined as described above, repetitive transmission of a signal is controlled by applying interleaving of different methods, scrambling of different methods, and precoding of different methods for each resource divided with the same data.

For example, for a small frequency band allocated to the receiving side, a total of 90 resource blocks are allocated, and if 15 repetitive transmission times are determined, as shown in FIG. 14, transmission data is allocated to 6 resource blocks. do. The resource block group is transmitted three times on the time axis and five times on the frequency axis.

In this case, in the data allocated to each resource block group, one transmission data is applied with a different interleaving rule, a different scrambling rule, and a different precoding rule for each resource block group (step 830).

Therefore, the 15 resource block groups illustrated in FIG. 14 are converted into data to which different interleaving rules, different scrambling rules, and different precoding rules are applied, mapped in the mapper, and then transmitted. It is transmitted to the receiving side through the transmitting and receiving unit (step 840).

Each transmission data transmitted in this way is configured like other data because different interleaving, scrambling, and precoding are performed even when repeatedly transmitting the same data between adjacent cells by a predetermined number of repetitive transmissions.

The transmitter / receiver on the receiving side receives the data and performs deprecoding, demodulation, descrambling, and deinterleaving so as to match each other, thereby implementing the data as an original signal.

The above detailed description should not be construed as limiting in all respects but should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

10: sensor node 20: central 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
50: underwater network 62: terrestrial network
64: managed node 600: FEC encoder
601 ~ 604: Interleaver 605 ~ 608: Scrambler
609 to 612: modulator 613 to 616: precoder
620: Mapper 700: Demapper
701 ~ 704: Deprecoder 705 ~ 708: Demodulator
709 ~ 712: Descrambler 713 ~ 716: Deinterleaver
720: LLR coupling unit 730: FEC decoder

Claims (9)

In underwater communication using a central node that collects detection information from a plurality of sensor nodes that detect underwater information and transmits the detected information to a terrestrial network,
Split the entire frequency band available to the central node into small frequency bands, and perform the underwater communication by allocating the divided small frequency bands to the respective sensor nodes based on the distance between the central node and the plurality of sensor nodes. ,
When performing underwater communication between the central node and any sensor node using the respective allocated small frequency bands, the allocated small frequency bands are set to N1 time dimensions and M1 frequency dimensions according to a predetermined algorithm. The method of repetitive transmission of underwater communication which divides and controls the repetitive transmission of N1 * M1 times for the same data. In underwater communication using a central node that collects detection information from a plurality of sensor nodes that detect underwater information and transmits the detected information to a terrestrial network,
Split the entire frequency band available to the central node into small frequency bands, and perform the underwater communication by allocating the divided small frequency bands to the respective sensor nodes based on the distance between the central node and the plurality of sensor nodes. ,
Based on the value of the underwater characteristic obtained through the test signal for the allocated small frequency band, the time dimension is divided into N2 and the frequency dimension into M2, and the same data is controlled for repeated transmission within the range of N2 * M2 times. Repeated transmission method of underwater communication. The method according to claim 1 or 2,
The repeated data transmission method of the underwater communication to control the repeated transmission by applying different interleaving rules, respectively. The method according to claim 1 or 2,
The repetitive transmission method of underwater communication, wherein the same data repeatedly transmitted is controlled by applying different scrambling rules. The method according to claim 1 or 2,
The repeated transmission of the same data is repeated transmission of the underwater communication to control the repeated transmission by applying different precoding rules. In underwater communication using a central node that collects detection information from a plurality of sensor nodes that detect underwater information and transmits the detected information to a terrestrial network,
Divide the entire frequency band available to the central node into small frequency bands, and perform the underwater communication by allocating the divided small frequency bands to the respective sensor nodes based on the distance between the central node and the plurality of sensor nodes; ,
When performing underwater communication between the central node and any sensor node using the respective allocated small frequency bands, the allocated small frequency bands are set to N1 time dimensions and M1 frequency dimensions according to a predetermined algorithm. Repeated transmission device for underwater communication that transmits N1 * M1 repetitive transmissions for the same data. In underwater communication using a central node that collects detection information from a plurality of sensor nodes that detect underwater information and transmits the detected information to a terrestrial network,
Divide the entire frequency band available to the central node into small frequency bands, and perform the underwater communication by allocating the divided small frequency bands to the respective sensor nodes based on the distance between the central node and the plurality of sensor nodes; ,
When performing underwater communication between the central node and any sensor node using the respective assigned small frequency bands, based on the value for the underwater characteristic obtained through the test signal, the assigned small frequency band, the time dimension Is a repetitive transmission apparatus for underwater communication in which N2 is repeated and N2 * M2 repetitive transmissions are performed on the same data by dividing the frequency dimension into M2. The method according to claim 6 or 7,
And the central node determines the number of repetitive transmissions, and transmits the determined number of repetitive transmissions to the sensor node. The method according to claim 6 or 7,
And the sensor node determines the number of repetitive transmissions, and transmits the determined number of repetitive transmissions to the central node.

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