KR20180057896A - Apparatus for controlling reference signal of underwater communication and method thereof - Google Patents

Abstract

The present invention relates to a reference signal device for downlink demodulation in underwater communication and a method thereof. The reference signal device has an effect of enhancing reception performance between a plurality of sensor nodes and a central node by variably controlling an insertion interval of a modulation reference signal transmitted within a carrier wave and effectively adjusting the demodulation reference signal inserted according to a field situation when an appropriate frequency band is allocated according to distance information between the plurality of sensor nodes and the central node and underwater information communication is performed.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a reference signal control apparatus for a submersible communication,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underwater communication, and more particularly, to a reference signal control apparatus and method for demodulating underwater communication.

As interest and importance of marine resource exploration, marine environmental monitoring, and underwater military defense have increased, demand for underwater communication that can collect various underwater information in the ocean is increasing. The underwater communication performs communication using ultrasonic waves due to the characteristics of the medium. The communication network for underwater information transmission includes a sensor node that can transmit and receive underwater information to an underwater environment, and acquires and controls underwater information from the sensor node.

Due to the underwater communication environment using the ultrasonic wave, the underwater communication network has a smaller signal bandwidth to be transmitted and a greater signal attenuation to the distance than the terrestrial communication. That is, the frequency used for the underwater communication network is very limited in order to perform reliable communication at a distance of several kilometers to several tens of kilometers.

Furthermore, as the demand for underwater information acquisition using the underwater communication network increases, the number of sensor nodes performing communication in the water increases. However, in the conventional underwater communication network, it is impossible to efficiently control a plurality of sensor nodes because of the frequency limitation in the underwater channel environment.

That is, when communication is performed using only one frequency in the conventional underwater communication network, if the corresponding frequency is allocated to one sensor node, all other sensor nodes can not transmit / receive signals.

In addition, when communication is performed using a plurality of frequencies in a conventional underwater communication network, if the number of sensor nodes desired to communicate in the water is greater than the assigned frequency, the number of sensor nodes in the water, I could not. In this case, all the sensor nodes must continuously check what frequency the sensor nodes are using, so that the consumption of the battery in the water greatly increases and the operation period of the sensor node in the water is greatly reduced.

Therefore, in the conventional underwater communication network, a plurality of sensor nodes can not be efficiently managed, thereby limiting the number of communicable sensor nodes. In addition, due to various demands for marine information, the number of sensor nodes is inevitably increased, and efficient control of underwater communication networks is further required in various areas.

In addition, the underwater communication is very unstable in signal transmission compared to the land communication. There are many reasons for this, but one example is affected by the time base due to the Doppler frequency caused by algae, waves, and the like. In addition, due to various multipaths due to sea level, sea floor, topography, etc., the frequency axis can be influenced. Also, the phenomenon that the velocity of sound wave varies with the depth of the sea also affects the underwater communication. In addition, factors such as salinity, seawater temperature, season and time also affect underwater communication. Underwater communication is unstable due to various factors, and such instability degrades the demodulation performance of receiving and demodulating actual signals.

It is therefore an object of the present invention to provide a reference signal control apparatus and method that can provide various demodulation reference signals for demodulation in underwater communication.

Another object of the present invention is to provide an apparatus and method for controlling a reference signal capable of variably controlling a demodulation reference signal for demodulation in accordance with a field situation 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 the underwater communication network into a plurality of smaller bandwidths and allocate the same frequency to a plurality of sensor nodes in a similar communication distance to perform efficient underwater communication using a large number of sensor nodes And to provide a reference signal control apparatus and method capable of variably controlling the demodulation reference signal for demodulation according to the field conditions.

According to an aspect of the present invention, there is provided a method of controlling a reference signal of a submersible communication, the method including: receiving a detection information from a plurality of sensor nodes that detect underwater information and transmitting the detected information to a terrestrial network; In underwater communication,

The entire frequency band that can be used by the central node is divided into small frequency bands, and the divided small frequency bands are allocated to the respective sensor nodes based on the distances between the central node and the plurality of sensor nodes, ,

When performing underwater communication between the central node and an arbitrary sensor node using the allocated small frequency bands, channel estimation to be carried on a carrier according to a predetermined algorithm and transmission of a demodulation reference signal to be used for data demodulation Is variably controlled.

A method of controlling a reference signal of an underwater communication according to another embodiment of the present invention is a method of controlling a reference signal in an underwater communication using a central node for collecting detection information from a plurality of sensor nodes for detecting underwater information,

The entire frequency band that can be used by the central node is divided into small frequency bands, and the divided small frequency bands are allocated to the respective sensor nodes based on the distances between the central node and the plurality of sensor nodes, ,

When carrying out underwater communication between the central node and an arbitrary sensor node using the respective allocated small frequency bands, channel estimation and data to be transmitted on a carrier using data on the underwater characteristic obtained through a test signal, And the transmission of the demodulation reference signal to be used for demodulation is variably controlled.

Preferably, the demodulation reference signal of the present invention variably controls the number of insertions, the insertion interval, and the insertion type.

Preferably, the demodulation reference signal of the present invention is variably adjusted in the frequency dimension in the resource block.

Preferably, the demodulation reference signal of the present invention is variably adjusted in a time dimension in a resource block.

In the underwater communication using a central node for collecting detection information from a plurality of sensor nodes for detecting underwater information and transmitting the same to a terrestrial network,

The entire frequency band that can be used by the central node is divided into small frequency bands, and the divided small frequency bands are allocated to the respective sensor nodes based on the distances between the central node and the plurality of sensor nodes, ,

When carrying out underwater communication between the central node and an arbitrary sensor node using the respective allocated small frequency bands, it is possible to variably adjust the insertion interval of the demodulation reference signal to be used for channel estimation and data demodulation, .

Preferably, in the underwater communication reference signal control apparatus of the present invention, when performing underwater communication between the central node and an arbitrary sensor node, a node operating on the transmitting side transmits demodulation reference signal transmission scheme information to the receiving node , The node operating on the receiving side recognizes the demodulation reference signal transmission scheme information and then transmits the demodulation reference signal between the transmitting side and the receiving side node.

Preferably, in the underwater communication reference signal control apparatus of the present invention, when performing underwater communication between the central node and an arbitrary sensor node, the node operating on the receiving side transmits the demodulation reference signal transmission scheme information to the transmitting node , And the transmitting node then transmits the demodulation reference signal to the receiving node based on the received reference signal transmission scheme information.

Preferably, the reference signal control apparatus of the underwater communication of the present invention is characterized in that the reference signal transmission scheme information is transmitted with corresponding index information of a frequency dimension or a time dimension in a resource block which is variably controlled in the demodulation reference signal .

Preferably, in the reference signal control apparatus for underwater communication according to the present invention, the reference signal transmission scheme information is transmitted from a physical layer or a MAC layer.

Preferably, the reference signal transmission method information of the present invention is a method of transmitting information for selecting one of the above-mentioned examples in a state in which information related to a plurality of predetermined reference signal insertion examples can be confirmed by both the transmitting side and the receiving side .

According to another aspect of the present invention, there is provided a method of transmitting a reference signal for underwater communication, the method comprising: receiving a demodulation reference signal to be used for demodulating a received signal between a transmitter and a receiver, Setting and storing various insertion methods;

Selecting one demodulation reference signal inserting method among the plurality of stored demodulation reference signal inserting methods;

Transmitting information on a predetermined demodulation reference signal and the selected demodulation reference signal insertion method in an initial connection procedure between the transmitting side and the receiving side;

Receiving the information, decoding it using a predetermined demodulation reference signal, and recognizing the selected demodulation reference signal inserting method on both the transmitting side and the receiving side; And

And transmitting the underwater information using the perceived demodulation reference signal inserting method.

An apparatus and method for controlling a reference signal of an underwater communication according to the present invention are characterized in that a proper frequency band is allocated according to distance information between a central node 20 and a plurality of sensor nodes 10, The reception interval between the plurality of sensor nodes 10 and the center node 20 can be increased by adjusting the insertion interval of the demodulation reference signal to be transmitted in a variable manner, .

In addition, the apparatus and method for controlling a reference signal of underwater communication according to the present invention are characterized in that the same frequency band is allocated to a plurality of sensor nodes 10 within a limited frequency band, The underwater channel estimation and the demodulation performance of the receiver can be improved by controlling the insertion interval of the demodulation reference signal transmitted on the carrier according to the field conditions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a general underwater communication network used for underwater communication shown in order to facilitate understanding of the present invention. FIG.
2 is a conceptual illustration of a central control type underwater communication network implemented to explain an underwater communication method according to an embodiment of the present invention.
3 is a diagram illustrating a process of dividing a frequency band for underwater communication within a limited frequency bandwidth according to an embodiment of the present invention.
4 is a diagram illustrating a process of allocating the same frequency band to a plurality of sensor nodes according to a communication distance within a limited frequency bandwidth according to an embodiment of the present invention.
FIG. 5 is a schematic diagram for explaining an underwater communication method according to an embodiment of the present invention. Referring to FIG.
6 is a diagram illustrating a schematic configuration of a sensor node for explaining an 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 an underwater communication method according to an embodiment of the present invention.
8 is a flowchart illustrating an operation of an underwater communication method according to an embodiment of the present invention.
9 is a flowchart illustrating an operation of an underwater communication method according to an embodiment of the present invention.
10 is a flowchart illustrating an operation of an underwater communication method according to an embodiment of the present invention.
FIGS. 11 to 15 illustrate examples of a resource block of a carrier wave to which a demodulation reference signal is inserted in the underwater communication of the present invention.
16 to 18 are diagrams showing a relationship between a transmitting side and a receiving side for explaining a process of a demodulation reference signal transmission method in underwater communication of the present invention.
Fig. 19 is a block diagram showing a part of the configuration of the transmitting side in the underwater communication of the present invention. Fig.
20 is a block diagram showing a part of the configuration of the receiver side in the underwater communication of the present invention.
21 is a block diagram showing an internal configuration of a demodulation reference signal generation unit in underwater communication of the present invention.
FIG. 22 is an operational flowchart for demodulating reference signal control in underwater communication of the present invention. FIG.
23 to 27 are illustrations showing resource blocks of a carrier wave when a plurality of demodulation reference signals are used.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals are used to designate identical or similar elements, and redundant description thereof will be omitted. The suffix "part " and" node ", " axis ", and " dimension " for components used in the following description are to be given or mixed in consideration of ease of specification, .

In the following description of the embodiments of the present invention, a detailed description of related arts will be omitted when it is determined that the gist of the embodiments disclosed herein may be blurred. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. , ≪ / RTI > equivalents, and alternatives.

Terms including ordinals, such as first, second, etc., may be used to describe various elements, but the elements are not limited to these terms. The terms are used only for the purpose of distinguishing one component from another.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The singular expressions include plural expressions unless the context clearly dictates otherwise.

In the present application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a component, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

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

1 is a diagram showing a general underwater communication network used for underwater communication shown in order to facilitate understanding of the present invention.

1 includes a plurality of sensor nodes 1, a sink node 5 and an intermediate node 3 serving as an information transferring function between the sensor node 1 and the sink node 5, .

The transmission of underwater information in the underwater communication network constructed as described above is performed as follows. The sensor node 1 to transmit the detected underwater information among the plurality of sensor nodes 1 transmits underwater information to the sink node 5 through the intermediate node 3 having a plurality of stages.

However, the underwater communication network constructed in this way must pass through the intermediate nodes 3 at various stages in transmitting the underwater information detected from the sensor node 1 to the sink node 5. Therefore, the routing algorithm for transmitting the detected underwater information is complicatedly implemented in the underwater communication network connected to the sensor node 1, the intermediate node 3 and the sink node 5 at various stages.

Also, if a transmission error occurs in the process of transmitting the underwater information from the sensor node 1 to the sink node 5, the above-mentioned underwater communication network is troublesome for retransmission of the detected underwater information.

In addition, if the problem occurs in the intermediate node for transmitting the underwater information due to the problem that the underwater communication network must pass through the intermediate nodes 3 at various stages, the sensor node related to the intermediate node in which the problem occurs should not be used.

Because of these parts, the general underwater communication network shown in FIG. 1 is inevitably deteriorated in efficiency of use of equipment including data transmission efficiency in the process of acquiring and transmitting various underwater information. By improving these points, the present invention intends to realize a central control type underwater communication network.

In the following description of the present invention, "frequency band" and "frequency" may be used in combination. Since the "frequency" refers to a frequency included in the "frequency band", and the frequency is substantially the same for frequencies included in a certain range of the frequency, the two words can be expressed in the same meaning.

2 is a conceptual illustration of a central control type underwater communication network implemented to explain an underwater communication method according to an embodiment of the present invention.

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

The central control type underwater communication network includes at least one sensor node 10. The sensor node 10 is installed so as to be fixed or movable in an underwater environment. The sensor node 10 is installed as much as possible in order to acquire a large amount of underwater information.

The central control type underwater communication network includes a central node (20) for collecting underwater information acquired from the plurality of sensor nodes (10). The central node 20 functions to transmit the underwater information collected by the plurality of sensor nodes 10 to a ground network (not shown).

The central control type underwater communication network configured as described above is entirely controlled as follows.

3 is a diagram illustrating a process of dividing a certain number of small frequency bands into a limited frequency band in order to control underwater communication according to an 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. And divides the entire available frequency band of the central node 20 into a forward frequency band and a reverse frequency band. Here, the entire frequency band that the central node 20 can use is a frequency band included in a region where underwater communication is possible between the central node 20 and the sensor node 10 installed at different distances. That is, it is possible to transmit a signal to the sensor node 10 installed at an arbitrary position in the central node 20 and to transmit the signal transmitted from the sensor node 10 to the central node 20 in a frequency band Express.

The forward frequency band is used when a signal is transmitted from a central node 20 to a plurality of sensor nodes 10. The frequency band used at this time is set to the lowest frequency band (f0) among the usable frequency bands of the central node 20. [

Generally, in the underwater communication environment, the communication range increases as the frequency to be transmitted and received becomes lower. Therefore, when a signal is transmitted from the central node 20 to the sensor node 10, it must be possible to receive signals from all the 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 for signal transmission to the plurality of sensor nodes 10 at the central node 20. [

And the reverse frequency band is used to perform signal transmission from each of the plurality of sensor nodes 10 to the central node 20. [ Among all the available frequency bands, all the remaining frequency bands except for the forward frequency band are included in the reverse frequency band.

The reverse frequency band is further divided into a plurality of small frequency bands. At this time, the division into small frequency bands is performed by grouping the sensor nodes capable of transmitting and receiving signals in the same frequency band between the distances from the sensor node and the center node to the same region, M).

And the divided small frequency bands are allocated to be used for signal transmission of the sensor node 10 installed at different positions. For example, the frequency band f1 is allocated to the sensor node 10 located at the farthest distance from the central node 20. And a frequency band fM is allocated to the sensor node 10 located closest to the central node 20. [

In this case, the sensor node 10 located at the farthest distance from the center node 20 is allocated the lowest frequency band among the frequency bands included in the reverse frequency band. Conversely, the highest frequency band among the frequency bands included in the reverse frequency band is allocated to the sensor node 10 located closest to the center node 20. As mentioned above, since the communication range increases as the frequency to be transmitted and received becomes lower in the underwater communication environment, the frequency f1 in the lower frequency band is allocated to the longest communication frequency. And the frequency (fM) of the highest frequency band is allocated to the shortest communication frequency.

In this way, frequency bands for underwater communication are allocated to the respective sensor nodes 10, and then the underwater information to the central node 20 is transmitted to the central node 20 using the frequency band allocated to the underwater information detected by the sensor node 10 The underwater communication is performed.

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

Underwater communications are more affected by environmental factors compared to terrestrial communications. Therefore, in the process of detecting underwater information using the underwater sensor in the sensor node 10, the loss of the sensor node 10 due to environmental influences can not be avoided. Also, even if an arbitrary sensor node 10 normally detects underwater information, the data transmission success rate can not always be 100% satisfied in the process of transmitting the detected underwater information to the central node 20. Therefore, if the condition of the underwater communication network is allowed, it is possible to obtain the underwater information more accurately and diversely by installing as many sensor node 10 as possible.

Meanwhile, as shown in FIG. 4, there is an area between the central node 20 and the sensor node 10 in which signals can be transmitted in the same frequency band. That is, the divided frequency bands fM are allocated to the sensor nodes existing in the region 1 included in the closest distance based on the central node 20. The divided frequency bands f1 are equally allocated to the sensor nodes located in the farthest distance M with respect to the central node 20. [

The division of the area between the central node 20 and the sensor node 10 into the same area or another area is performed within a range in which signal transmission / reception between the central node 20 and the sensor node 10 is possible. That is, the sensor nodes capable of underwater communication in the same frequency band (fM) are included in the zone 1. In addition, sensor nodes capable of underwater communication in the same frequency band (f1) are included in the area M.

The reason why the same frequency band is assigned to a plurality of sensor nodes is that there is a limit to the frequency band that can be used by the central node 20. For example, in order to acquire underwater information more accurately and diversely, it is necessary to increase the number of sensor nodes. In this case, the number of sensor nodes 10 installed in the entire frequency band available at the central node 20 may be greater than the number of reverse frequency bands divided. At this time, as shown in FIG. 4, the same frequency band is allocated to the sensor nodes existing in the same area to control underwater communication.

When the same frequency band is allocated to a plurality of sensor nodes as described above, a plurality of sensor nodes 10 in the same area allocated the same frequency band are controlled by the central node 20, A frequency division multiple access scheme, a time division multiple access scheme, a code division multiple access scheme, a carrier sensing multiple access scheme, and the like). A 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 the embodiment of the present invention, it is necessary to detect the distance information between the sensor nodes in the central node. Prior to this description, a schematic 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 schematic block diagram illustrating an underwater communication method according to an embodiment of the present invention.

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

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

Referring to FIG. 5, a plurality of sensor nodes 10 collects underwater information and transmits the collected information to a central node 20. At this time, underwater information is transmitted and received between the plurality of sensor nodes 10 and the central node 20 using the ultrasonic wave, which enables signal transmission in the underwater communication network 50 due to the characteristics of the medium. The sensor node 10 transmits its own position data at the time of signal transmission from the sensor node 10 to the central node 20. The position information of the sensor node 10 is preferably recorded and stored in the sensor node 10 at a time when the sensor node 10 is installed at an arbitrary position in the water. However, it is difficult for the sensor node 10 to be fixedly installed due to the characteristics of the underwater environment. Therefore, although it is described as the above-mentioned position information, it is preferable to understand it as 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 underwater information acquired by the management node 64 of the terrestrial communication network 60. Accordingly, the central node 20 performs underwater communication with a plurality of sensor nodes 10 in the underwater communication network 50 and performs communication with the ground management node 64. The management node 64 performs a function of connecting the underwater information transmitted through the central node 20 to the terrestrial communication network 62 using a wireless signal.

Referring to FIG. 6, the sensor node 10 includes at least one sensor unit 30 for collecting necessary data in water, a sensor unit 30 for modulating data sensed by the sensor unit 30, And a data receiving unit 38 for receiving and demodulating the ultrasonic signals transmitted from the central node 20. The data transmitting unit 36 transmits the ultrasonic signals to the node 20, The data transmitting unit 36 and the data receiving unit 38 may further include a controller 32 included in the transmitting and receiving unit 40 and performing control between the sensor unit 30 and the transmitting and receiving unit 40. And a memory 34 for storing various data and algorithms required for the overall operation control of the sensor node 10 and for storing the underwater information detected by the sensor unit 30.

The plurality of sensor units 30 sense various kinds of underwater information including water temperature, dissolved oxygen amount, seismic wave, and the like, and output sensed data to the control unit 32 according to their purpose. The sensor unit 30 may be a digital sensor, but it may be configured to convert data sensed by an analog signal into digital data and output it. In this case, the sensor unit 30 may include an analog-to-digital converter for converting an analog signal into a digital signal. In all the configurations of the present invention, the signal processed data is a digital signal.

The transceiver 40 performs the function of transmitting or receiving data by using ultrasonic waves in water. That is, the data transmitting section 36 modulates the underwater information detected by the sensor section 30, converts the underwater information into an ultrasonic signal, and transmits the ultrasonic signal to the central node 20. The data receiving unit 38 receives and demodulates the ultrasound signals transmitted from the central node 20, and outputs the ultrasound signals to the control unit 32.

The illustrated sensor node 10 receives the underwater information transmitted from the central node 20 via the data receiving unit 38. [ At this time, in order to enable reception of the signal transmitted from the central node 20, the data receiver 38 sets the frequency to a frequency included in the forward frequency band. Further, the data transmitting unit 36 is set to a specific frequency included in the frequency band allocated to itself, and transmits information to be transmitted to the central node 20 by loading the specific frequency. Therefore, the transmission / reception unit 40 includes a configuration in which the frequency is set under the control of the control unit 32. Such a configuration is made by a known technique, and a further explanation is omitted. In the initial setting process in which the frequency of each sensor node 10 is not set, the forward frequency band is set at the time of receiving the signal from the central node 20, and the signal is transmitted to the central node 20 before the initial setting Is set to the lowest frequency band among the divided reverse frequency bands.

In the present invention, the sensor node 10 can be fixedly installed at a specific position in an underwater environment, but it can only be moved in a certain region due to the influence of an ocean current. Since the sensor node 10 is likely to move in this way, it is preferable that the distance measurement with the central node 20 is performed in real time at the time when the underwater information measurement is performed. However, if the real-time control is unreasonable, it is preferable to repeatedly measure at intervals of a certain time avoiding the time during which underwater communication is performed. Since the frequency of use relative to the distance can be changed, the sensor node 10 needs to variably control the available frequency band for underwater communication with the central node 20 in real time.

In this case, it is preferable that the transmitting / receiving unit 40 of the sensor node 10 is configured to be able to variably control the set frequency. That is, the frequency for transmitting the information is variably controlled according to the current position of the sensor node 10, so that information to be transmitted can be transmitted to the central node 20. It is preferable that the movement position of the sensor node 10 is limited only within a certain radius in which signals can be transmitted and received with the central node 20 to prevent the risk of the sensor node 10 being lost.

The control unit 32 performs control to store various kinds of underwater information detected by the sensor unit 30 in the memory 34 or controls transmission and reception of underwater information through the transmission and reception unit 40 do.

The control unit 32 also performs control for detecting the 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 from the central node 20 for distance detection by the data receiving unit 38 and detecting the magnitude of the received power. The power intensity of the received signal can be detected by a simple calculation process by directly detecting the power of the received signal or detecting the current, voltage, and the like. The received power magnitude detection configuration is applicable by various techniques including a known power detector. The current magnitude can be easily detected by providing a current detecting resistor in the receiving section. Since these detection portions utilize a known technique, detailed description thereof will be omitted. The distance estimation using the detected power intensity of the received signal can estimate the distance using the distance value stored in the memory 34 with respect to the power intensity.

In addition, the control unit 32 may detect and use a delay time required until the center node 20 transmits a signal and arrives at the sensor node 10 as another method for distance detection. The delay time detection can be detected by comparing the time information for starting the signal transmission at the central node 20 with the time information at which the signal arrived, for example. In order to detect the arrival time information, the control unit 32 preferably includes a time counting function or the like. In the distance estimation using the detected delay time, it is possible to estimate the distance using the distance value compared with the delay time previously stored in the memory 34.

The memory 34 is used for storing various kinds of information that the sensor node 10 uses or needs. The detection information of the sensor unit 30 is also stored in the memory 34. [ Particularly, when the distance is directly detected by the sensor node 10, the memory 34 stores various information to be used for the distance detection. For example, information for determining the distance between the central node 20 and the sensor node 10 using the information for determining the strength of the received power, the information for detecting the delay time, and the strength of the received power, And frequency band information that can be communicated underwater according to the distance information. Using the various information stored in the memory 34, the controller 32 performs distance estimation, a specific frequency band request, and the like.

7, the central node 20 includes a first transceiver 22 for transmitting and receiving underwater signals to and from the sensor node 10, and a second transceiver 22 for transmitting / And a second transmission / reception unit 21 for performing the second transmission / reception. The central node 20 includes a controller 28 for controlling the first and second transceivers and for controlling information storage, and a memory 29 for storing various information. The second transceiver 21 is preferably configured to be able to transmit ultrasonic waves according to whether the position of the central node 20 is above the water surface or below the water surface, or to be transmittable with a radio signal or the like.

In addition, the central node 20 includes a frequency divider 27 for dividing the entire usable frequency band into a forward frequency band and a reverse frequency band, and further dividing the reverse frequency band into a small frequency band . The frequency divider 27 may be included in the first transceiver 22 because it is used when transmitting and receiving underwater information with the sensor node 10.

The frequency divider 27 is configured to be able to divide the entire frequency band available in the central node 20 into frequency bands as small as the number of regions (M), as shown in Fig. Therefore, the control unit 28 controls the frequency division of the frequency divider 27, and controls the frequency divider 27 to divide the frequency of the frequency divider 27 into a corresponding frequency when transmitting / receiving signals to / from an arbitrary sensor node 10 So that transmission and reception of signals can be normally performed.

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

For this, a frequency division is performed through the frequency divider 27 under the control of the control unit 28, and a series of processes of setting the frequency of the data receiving unit 24 at the divided frequency is controlled. The frequency dividing operation of the frequency divider is preferably performed in a digital manner. In addition, the data receiving unit 24 includes a frequency variable control structure to enable normal signal reception during signal transmission / reception with all the sensor nodes.

In addition, the controller 28 controls the multiple accesses to the sensor nodes 10 existing at a distance similar to the power management and traffic control for each sensor node 10, (20). In the present invention, the control unit 32 of the sensor node 10 may perform the distance detection process, but the control unit 28 of the central node 20 may perform the distance detection process.

Therefore, the controller 28 receives the reference signal transmitted from the sensor node 10 for distance detection by the data receiving unit 24 in the initial setup process in which the frequency of the sensor node is not set, As shown in Fig. The power intensity of the received signal can be detected by a simple calculation process by directly detecting the power of the received signal or detecting the current, voltage, and the like. The received power magnitude detection configuration is applicable by various techniques including a known power detector. It is also possible that the received power magnitude detection is performed in the sensor node and only the detected information is received. The current magnitude can be easily detected by providing a current detecting resistor in the receiving section. Similarly, it is also possible that the current magnitude detection is performed by the sensor node and only the detected information is received. Since these detection portions utilize a known technique, detailed description thereof will be omitted. The distance estimation using the power intensity of the detected received signal can estimate the distance using the distance value stored in the memory 29 with respect to the power intensity.

In addition, the control unit 28 can detect and use the delay time required for the sensor node 10 to arrive at the central node 20 after transmitting the signal. The delay time detection can be detected by comparing the time information of starting the signal transmission at the sensor node 10 with the time information of the arrival of the signal at the central node 20, for example. In order to detect the arrival time information, the control unit 28 preferably includes a time counting function or the like. And, in the distance estimation using the detected delay time, the distance can be estimated by using the distance value compared with the delay time previously stored in the memory 29.

The memory 29 is used for storing various kinds of information that are used or required by the sensor node 10 and detected. Particularly, when the distance is detected at the central node 20, the memory 29 stores various information to be used for distance detection. For example, information for determining the distance between the central node 20 and the sensor node 10 using the intensity of the received power supplied from the sensor node 10, the delay time, etc., And frequency band information enabling possible underwater communication. Using the various information stored in the memory 29, the controller 28 estimates the distance and selects a specific frequency band to be allocated to an arbitrary sensor node. The memory 29 also includes control information for frequency division, and also stores related information such as a divided frequency band and a sensor node set therein. And it also stores underwater information collected from sensor nodes.

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

8 is an operation procedure according to a first control method used when a specific frequency is allocated to the sensor node 10 at the central node 20. [

The distance information between the central node 20 and the sensor node 10 must be detected in the underwater communication network of the present invention. A specific frequency band is allocated to the sensor node 10 according to the detected distance information. That is, 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 usable frequency band and divides the usable whole frequency band into the forward frequency band and the reverse frequency band as shown in FIG. 3 (Step 200)

In addition, the control unit 28 performs control to divide the reverse frequency band into a small frequency band by the number of regions (M number) shown in FIG. 4 (operation 205). It is preferable that the steps 200 and 205 are controlled so as to be set according to the performance of the central node. That is, when the central node 20 performs transmission and reception of signals in the underwater environment, the center node 20 stores frequencies that can be transmitted the farthest in the forward frequency band. When the central node 20 transmits and receives a signal in an underwater environment, the distance (area) in which each frequency of use transmits a signal is previously classified and stored. The distances and frequency values thus set are preferably 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 the stored distance information is read from the memory 29. The reference signal is transmitted to all the sensor nodes 10 that are loaded in the forward frequency band and converted into an ultrasonic signal through the data transmission unit 26 and included in the entire usable frequency band of the central node 20, The receiving unit 38 of the sensor node 10 receives the reference signal (step 210).

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

After the distance is estimated in step 220, the sensor node 10 requests to allocate a frequency band corresponding to the distance estimated by the central node 20 to its frequency band in step 230. In step 230, since a frequency band is allocated to the corresponding sensor node, the frequency band request signal is transmitted using the frequency band set to the lowest frequency band among the reverse frequency bands. . Also, the frequency band corresponding to the distance estimated in step 230 is also selected based on the stored value of the memory 34, which is stored in advance.

Thereafter, the central node 20 collects the frequency band information requested from the plurality of sensor nodes 10, allocates a frequency band suitable for each sensor node 10, and transmits the allocated frequency information to the sensor node 10 (Step 240). Therefore, the data receiving unit 24 of the central node 20 is set to the forward frequency band up to step 240. [

The sensor node 10 receives an ultrasonic signal transmitted in the frequency band f0 allocated to the forward frequency band from the central node 20 at the time of transmitting / receiving information underwater with the central node 20, (20) transmits the ultrasound signals by loading the underwater information in the frequency band allocated to the user in the reverse frequency band.

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

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

9 shows an operation procedure according to a second control method used when a specific frequency is allocated to the sensor node 10 at the central node 20. [ The illustrated embodiment is a control process for estimating the distance to each sensor node 10 under its own judgment at the central node 20 and allocating the frequency to each sensor node 10 according to the estimated distance.

First, the control unit 28 of the central node 20 identifies the entire usable frequency band and divides the usable whole frequency band into the forward frequency band and the reverse frequency band as shown in FIG. 3 (Step 300).

The control unit 28 performs control to divide the reverse frequency band into a small frequency band by the number of areas (M number) shown in FIG. 4 (step 305). It is preferable that the steps 300 and 305 are controlled so as to be set according to the performance of the central node 20. That is, when the central node 20 performs transmission and reception of signals in the underwater environment, the center node 20 stores frequencies that can be transmitted the farthest in the forward frequency band. When the central node 20 performs transmission and reception of signals in an underwater environment, the distance (area) at which each frequency is used for signal transmission is previously classified and stored. The distances and frequency values thus set are preferably 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 the stored distance information is read from the memory. The reference signal is transmitted in the forward frequency band, converted into an ultrasonic signal, and the transmission operation from all the sensor nodes 10 to the central node 20 is controlled. The central node 20 receiving the reference signal transmitted from the plurality of sensor nodes 10 through the data receiving unit 24 detects the power intensity of the received signal from each sensor node and the delay time used for the transmission time, do. In the signal transmission / reception process for the detection signal, a frequency band is allocated to the corresponding sensor node. The data transmission unit 36 of the sensor node 10 and the data reception unit 24 of the central node 20 transmit and receive signals using the frequency band set to the lowest frequency band among the reverse frequency bands (Step 310). On the other hand, it is also possible to perform the signal detection operation directly at the sensor node 10, input the detection control information at the central node 20, and then use it for distance estimation.

In step 310, the central node 20 detects a signal for distance estimation. The central node 20 calculates the distance between the central node and each sensor node using the power intensity of the received signal of each sensor node, The distance is estimated (step 320). In this case, the distance can be estimated by using the distance value stored in the memory 29 with respect to the power intensity. It is also possible to estimate the distance using the time delay vs. distance value stored in the memory 29.

Subsequently, 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 side (steps 330, 340 ).

The sensor node 10 receives the ultrasound signals transmitted in the frequency band f0 allocated to the forward frequency band from the central node 20 and transmits the ultrasound signals to the central node 20 20) transmits the ultrasound signals by loading the underwater information in the frequency band allocated to itself in the reverse frequency band.

In this way, an appropriate frequency band is adaptively allocated between the central node 20 and the plurality of sensor nodes 10 according to the distance information between the central node 20 and the sensor node 10, Loses. Therefore, the present invention enables efficient communication of a plurality of sensor nodes 10 and the central node 20 in the water within a limited frequency band.

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

10 is an operation procedure according to a third control method used when a specific frequency is allocated to the sensor node 10 at the central node 20. [ In the illustrated embodiment, the same frequency band can be set for a plurality of sensor nodes.

 The control unit 28 of the central node 20 identifies the entire usable frequency band and divides the usable whole frequency band into the forward frequency band and the reverse frequency band as shown in Figure 3 Step 400).

Also, the control unit 28 performs control to divide the reverse frequency band into a small frequency band by the number of regions (M number) shown in FIG. 4 (Step 405). Preferably, steps 400 and 405 are controlled to be preset according to the performance of the central node. That is, when the central node 20 performs transmission and reception of signals in the underwater environment, the center node 20 stores frequencies that can be transmitted the farthest in the forward frequency band. When the central node 20 transmits and receives a signal in an underwater environment, the distance (area) in which each frequency of use transmits a signal is previously classified and stored. The distances and frequency values thus set are preferably 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 the stored distance information is read from the memory 29. The reference signal is transmitted to all the sensor nodes 10 that are loaded in the forward frequency band, converted into ultrasonic signals through the data transmission unit 26, and included in the entire usable frequency band of the central node 20 Step 410).

The sensor nodes 10 receiving the reference signal transmitted in step 410 through the data receiving unit 38 detect the power intensity of the received signal and / or the time delay used for signal transmission, (20). 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 signals detects the power of the received signal input from each sensor node and / or the time delay used for signal transmission, The distance to the node is estimated (step 420). In this case, the distance can be estimated by using the distance value stored in the memory 29 with respect to the power intensity. It is also possible to estimate the distance using the time delay vs. distance value 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). In step 430, when a frequency is allocated to the sensor node 10, the same frequency band is allocated to the sensor nodes having the same distance or similar distance as shown in FIG. At this time, the central node 20 binds sensor nodes capable of transmitting and receiving signals in the same frequency band on the basis of the sensor node to the same area. And the same frequency band is assigned to the same area.

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

The sensor node 10 receives the ultrasound signals transmitted in the frequency band f0 allocated to the forward frequency band from the central node 20 and transmits the ultrasound signals to the center node 20 20) transmits the ultrasound signals by loading the underwater information in the frequency band allocated to itself in the reverse frequency band.

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

The reason why the same frequency is allocated to a plurality of sensor nodes is because there is a limit to the frequency band that can be used by the central node 20. For example, in order to acquire underwater information more accurately and diversely, it is necessary to increase the number of sensor nodes. In this case, the number of sensor nodes 10 installed in the entire frequency band available at the central node 20 may be greater than the number of reverse frequency bands divided. At this time, as shown in FIG. 4, the same frequency band is allocated to the sensor nodes existing in the same area to control underwater communication.

According to the embodiment of FIG. 10, the same frequency band is allocated to a plurality of sensor nodes 10 within a limited frequency band, and a plurality of sensor nodes are efficiently And performs underwater communication. Therefore, efficient underwater communication control is enabled for more sensor nodes than the number of divided frequency bands.

Next, as described above, a carrier signal is transmitted using a frequency allocated in an efficient underwater communication using a plurality of sensor nodes in a limited frequency band, and a demodulation reference signal is loaded to the carrier signal so as to improve reception performance Let's look at the transmission operation.

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

On the other hand, the underwater communication of the present invention uses a method of transmitting data to a plurality of carriers. For example, a certain number of subcarriers may be allocated and used for a predetermined period of time.

The present invention also applies an OFDM communication scheme to perform underwater communication. 11 shows a physical resource block used in the OFDM communication system. That is, a certain number of sub-carriers are allocated for a predetermined time in the OFDM communication, which is called a physical resource block, and has both a time dimension and a frequency dimension. In the OFDM communication, a special reference signal is embedded in the physical resource block. The reference signal is assigned to each cell in the OFDM communication and acts as a cell specific identifier. In this case, the reference signals may be allocated to each cell differently, or the same reference signal may be used until a predetermined number of cells are transmitted, and the reference signal may be used after a predetermined number of cells are transmitted. Therefore, a channel is estimated through a symbol carrying a reference signal commonly known to the transmitting and receiving end, and data restoration is performed using the estimated value. Hereinafter, the specific reference signal is referred to as a demodulation reference signal.

In this way, in the OFDM communication system, a symbol containing a demodulation reference signal commonly known to the transmitting and receiving end is inserted at a specific position and used. However, as mentioned above, since the underwater channel changes due to various factors in underwater communication, satisfactory channel estimation and data restoration by the symbol insertion (symbol insertion) including the standardized reference signal used in the existing land- This was difficult.

Therefore, in the present invention, when transmitting a reference signal for demodulation using a limited frequency in an underwater communication network, the demodulation reference signal is varied and transmitted according to the field conditions so as to efficiently communicate with a large number of sensor nodes . The meaning of changing the demodulation reference signal thereafter indicates not to change the demodulation reference signal itself but to transmit the predetermined demodulation reference signal in various ways such as the position at which the demodulation reference signal is inserted, .

This is because the underwater situation is highly variable due to various factors such as time, place, season, temperature, etc., and the demodulation reference signal is appropriately inserted according to such variable site conditions, This is because demodulation can be done safely.

In this way, when the demodulation reference signal is variably adjusted, for example, the demodulation reference signal can be inserted while adjusting the interval of the demodulation reference signal in the frequency dimension in the physical resource block. As another example, the demodulation reference signal can be inserted while adjusting the interval of the demodulation reference signal in the time dimension. As another example, the demodulation reference signal can be inserted while adjusting the interval of the demodulation reference signal in both the time dimension and the frequency dimension. As another example, one method may be selected and transmitted in the example in which various predetermined types of demodulation reference signals are inserted.

12 shows an example in which the intervals of the demodulation reference signals are variable in the frequency dimension. That is, a symbol carrying a demodulation reference signal of a time (M) dimension is fixed, and a position of a symbol carrying a demodulation reference signal of a frequency (N) dimension is variably controlled.

13 shows an example in which the interval of the demodulation reference signal is varied in the time dimension. That is, the demodulation reference signal shows an example in which the frequency dimension N is fixed and the interval in the time dimension M is variably controlled.

FIG. 14 shows an example in which the intervals of the demodulation reference signals are varied in both the time (M) and the frequency (N).

FIG. 15 shows an example in which an example in which a demodulation reference signal is inserted is determined variously, and one of the demodulation reference signals is selected and used.

On the other hand, if both the transmitting side and the receiving side know the information of the demodulation reference signal (the position information in which the demodulation reference signal is inserted in the resource block) inserted in various ways described in Figs. 12 to 15, . However, when the demodulation reference signal is variably inserted in the time dimension, the frequency dimension, or both the time dimension and the frequency dimension as in the present invention, the receiving side does not know the insertion position of the demodulation reference signal in the initial state. Therefore, there is a need to recognize the information according to the transmission method of the demodulation reference signal to the receiving side, and then transmit the demodulation reference signal using the determined reference signal transmission method.

FIG. 22 shows a process flow of controlling a demodulation reference signal in an underwater channel according to the present invention.

A node to be used as a transmitter and a node to be used as a receiver are determined between a central node and an arbitrary sensor node. Typically, the central node will act as the sender, and the sensor node will likely be used as the receiver. Of course, in the case of requesting signal transmission from the sensor node to the central node first, the sensor node may be operated as a transmitting side, and the central node may be operated as a receiving side. That is, the central node and the sensor node are configured to perform both transmission and reception. A small frequency band to be used in underwater communication is allocated between the central node and an arbitrary sensor node (operation 500).

In the initial process in which the central node and the sensor node transmit the demodulation reference signal for signal transmission and reception, the demodulation reference signal is transmitted using a predetermined demodulation reference signal transmission method known to both the transmitting side and the receiving side (operation 510) . In this case, it is not necessary to exchange information on the transmission method of the demodulation reference signal with each other. FIG. 16 shows a process of transmitting and receiving signals between a transmitting side and a receiving side according to a predetermined demodulation reference signal transmission method in the initial connection process. In general, in this process, it is preferable to select a method of inserting and transmitting a demodulation reference signal at a specific position already used in the OFDM communication system. The step 510 may be described as a process of first confirming whether or not a signal transmission / reception state is available, such as a channel check used between the transmitting side and the receiving side.

In addition to using the predetermined demodulation reference signal transmission scheme in step 510, the demodulation reference signal transmission scheme information for the initial process may be transmitted to the receiver through the broadcasting channel.

Next, the demodulation reference signal transmission method to be used is determined in a state in which signals can be transmitted and received between the transmitting side and the receiving side. That is, it is a process of selecting one transmission scheme to be used among the transmission schemes described in the various methods described in the procedure of FIG. 12 to FIG. Then, the determined demodulation reference signal transmission scheme information is transmitted to the peer (step 520).

FIG. 17 shows an example of transmitting demodulation reference signal transmission scheme information to a receiver on the transmission side, and then transmitting data including a demodulation reference signal after confirming the reception side sufficiently ).

It is generally preferable that the transmitting side transmit demodulation reference signal transmission scheme information to the receiving side. However, the underwater communication situation is very fluid and more imperfect than the ground. Therefore, it is preferable to select the demodulation-based signal transmission method information in which the signal transmission is appropriately performed after preferentially determining the current underwater communication situation at the reception side.

18 shows an example in which the information on the reference signal information system is notified to the transmitting side first on the receiving side. That is, the demodulation reference signal information system of the type capable of channel estimation and signal demodulation at the reception side is selected, and information corresponding to the demodulation reference signal information system is provided to the transmission side, whereby the transmission side performs transmission of the demodulation reference signal in a manner required by the reception side 530).

As shown in FIG. 18, in order to select the reference signal transmission scheme information on the reception side and notify the transmission side, the reception side must have various information according to the reference signal transmission scheme. One way is to store the reference signal transmission scheme information in a memory (not shown) on the reception side to satisfy such a part.

Or a channel check using a predetermined demodulation reference signal transmission scheme in step 510 and then providing the demodulation reference signal transmission scheme information from the transmitter to the receiver using a predetermined demodulation reference signal transmission scheme One way. In this case, it is preferable that the predetermined reference signal and data are transmitted through a predetermined reference signal transmission method, and the data corresponding to the demodulation reference signal transmission scheme information of the present invention is included in the data and transmitted.

Meanwhile, it is preferable that the information of the demodulation reference signal transmission scheme shown in FIGS. 17 and 18 is transmitted from the physical layer or the MAC layer. In the case of transmitting through the physical layer, it is preferable to transmit through a control channel or a data channel. The information of the demodulation reference signal transmission scheme can be independently defined and transmitted or combined with other information. For example, it may be transmitted in one form among Modulation and Coding Scheme (MCS) levels.

In transmitting the information of the demodulation reference signal transmission scheme shown in FIGS. 17 and 18, index information about a variable interval in the frequency dimension is transmitted, and information for adjusting the interval of the demodulation reference signal is transmitted in the frequency dimension. In this case, the index information of the subcarriers is variably adjusted, and the demodulation reference signal interval in the symbol becomes a predetermined value.

In transmitting the information of the demodulation-based signal transmission scheme, index information about a variable interval in the time dimension is transmitted, and information for adjusting the interval of the demodulation reference signal in the time dimension is transmitted. In this case, the index information of the symbol is variably adjusted, and the demodulation reference signal interval in the subcarrier is a predetermined value.

In transmitting the information of the demodulation reference signal transmission scheme, index information about a time dimension and an interval that varies in the frequency dimension is transmitted, and information for adjusting the interval of the demodulation reference signal is transmitted in both the time dimension and the frequency dimension. In this case, index information of a variable subcarrier and index information of a symbol are transmitted.

In transmitting the information of the demodulation-based signal transmission scheme, when one example is selected and used in a plurality of predetermined reference signal insertion examples as shown in FIG. 15, the index information of the time dimension or the frequency dimension index Information or time dimension and frequency dimension index information are transmitted. Or if the information related to the selected example is present on both the receiving side and the transmitting side, the number information corresponding to the selected 'one example' may be transmitted.

FIG. 15 shows an embodiment in which a demodulation reference signal is inserted in different numbers, types, and positions, and in addition to the illustrated embodiment, a demodulation reference signal may be inserted in another embodiment.

In the case of transmitting the information of the demodulation reference signal transmission scheme shown in FIGS. 17 and 18, the corresponding index information of the frequency dimension or the time dimension in the resource block that is variable-controlled in the demodulation reference signal is transmitted. However, the information of the demodulation reference signal transmission method is not limited to the index information. That is, various information that can be used as information of the demodulation reference signal transmission scheme other than the index information may be transmitted. That is, other information may be used if it is information capable of recognizing the position information on the demodulation reference signal to be transmitted.

FIG. 19 is a block diagram illustrating a configuration of a transmitting side for explaining a reference signal control apparatus in underwater communication according to the present invention. FIG. FIG.

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

As shown in Fig. 19, the demodulation reference signal is generated in the demodulation reference signal generator 610. [ The demodulation reference signal generator 610 generates a demodulation reference signal according to various methods as described above, and the generated demodulation reference signal is precoded by the precoder 620 according to the number of multiplexing channels. And time frequency mapper 630 functions to map the precoded demodulation reference signal in the resource block for transmission. The mapped signal is transmitted through a transmission antenna.

As shown in Fig. 20, the receiving side includes a time-frequency demapper. The time-frequency demapper 710 demaps the demodulation reference signal from the transmitted resource block, and then the channel estimation unit 720 estimates the effective channel, that is, the channel itself and the demodulation precoder 730 for demodulating the data by the data demodulation unit 730, Estimate the product with the matrix.

Meanwhile, the demodulation reference signal transmission method and the variable control of the demodulation reference signal to be used in the present invention are not uniform, but need to be variably controlled to suit the situation of the field. The situation at the site where underwater communication occurs changes very irregularly. Therefore, there is a need to apply the demodulation reference signal variable control value calculated by the experiment by applying various factors that can vary the underwater communication and apply it.

Particularly in the present invention, considering that the state of the underwater communication is remarkably worse than that of the terrestrial communication, it is necessary that the variably controlled demodulation reference signal includes a relatively larger number as compared with the terrestrial communication.

Fig. 21 shows a part of the configuration required when the demodulation reference signal is generated in the present invention.

The illustrated demodulation reference signal generator is adapted to apply various parameters (temperature, time, season, salinity, seawater temperature, various parameters affecting underwater communication including user input values) that may affect underwater communication And a memory 612 for storing a setting value for demodulating reference signal variable control set to an appropriate value accordingly. Various elements that may affect the underwater communication can be detected through the detection function of the sensor node.

And a demodulation reference signal generator 611 for obtaining a set value for variable demodulation reference signal variable control from the memory 612 and generating a demodulation reference signal corresponding thereto. And selects a setting value for the optimum demodulation reference signal variable control from the memory 612 or a setting value for the optimum demodulation reference signal variable control from the memory 612 from the user's requirements, And a control unit 613 for variably controlling and outputting the demodulation reference signal according to a predetermined algorithm. From this configuration, the demodulation reference signal generator 611 variably controls the demodulation reference signal to meet the current underwater situation.

As described above, in order to generate the demodulation reference signal with optimum and variable control, it is necessary to find a condition suitable for the current underwater situation. In generating and transmitting the demodulation reference signal, it is possible to generate the demodulation reference signal in accordance with a program autonomously set on the transmitting side or the receiving side. In this case, parameters for variable control of the demodulation reference signal can be applied to the underwater channel characteristics, signal-to-noise ratio (or interference ratio), bit error rate, packet error rate, and retransmission counts of the received signal in addition to the parameters described above.

The reference signal spacing adjustment on the frequency axis is closely related to the length of the underwater channel (multipath number), and the reference signal spacing on the time axis is closely related to how fast the underwater channel changes over time (Doppler frequency) do. Therefore, if the receiving side measures the underwater channel characteristics and delivers the measured underwater channel characteristics to the transmitting side, the transmitting side can select the variable set value of the demodulating reference signal based on the feedback information. Or a variable set value of the demodulation reference signal based on the underwater channel characteristics measured at the reception side, and can transmit the corresponding information to the transmission side.

That is, the demodulation-based signal transmission scheme is selected and determined based on the parameters used for this purpose, such as the underwater channel length, Doppler frequency, RSSI, RSRP, RSRQ, bit error rate, packet error rate, retransmission number , And may be changed depending on whether the subject determining the reference signal transmission scheme is the transmission side or the reception side.

As an example, when the length of the underwater channel becomes long, it is possible to perform control to reduce the reference signal interval on the frequency side. If the Doppler frequency increases, control can be performed to reduce the reference signal interval on the time axis. Also, when the size of the received signal (measured through RSSI, RSRP, RSRQ, etc.) decreases, or the bit error rate, packet error rate, retransmission count, etc. increase, the time base or frequency axis, It is possible to perform the control to reduce the interval of the time interval. Therefore, the demodulation reference signal variable control can be controlled through a predetermined algorithm. Or may be determined by applying predetermined set values obtained through testing to the various variable variable values mentioned above.

Although the OFDM communication method is described as an example in the description process of the present invention, it is obvious that the present invention can also be applied to an FMT, FBMC, SC-FDMA method using a method of sending data to a plurality of carriers.

In the process of the embodiment of FIGS. 11 to 15 described above, a form of variably inserting one type of demodulation reference signal has been described. Although only the variable insertion position for the demodulation reference signal is described in the above embodiment, this may include that the number of variable insertion symbols for the demodulation reference signal may be different. That is, since the insertion position of the demodulation reference signal is changed, the insertion number of the demodulation reference signal inserted can be changed.

In the present invention, the demodulation reference signal to be inserted is not limited to one type. For example, as shown in Figs. 23 to 27, it is also possible to use two kinds of demodulation reference signals.

FIG. 23 shows a basic example in which two demodulation reference signals are used, and FIG. 24 shows an example in which the intervals of the demodulation reference signals are variably controlled in the frequency dimension. That is, a symbol carrying a demodulation reference signal of a time (M) dimension is fixed, and a position of a symbol carrying a demodulation reference signal of a frequency (N) dimension is variably controlled. In the illustrated example, it is explained that the time dimensions M1 and M2 are fixed for the first demodulation reference signal and the second demodulation reference signal, and that the time dimensions M1 and M2 are all variable for the frequency dimensions N1 and N2.

However, it is also possible to adjust the frequency dimension to be variable for only one demodulation reference signal among the two demodulation reference signals. For example, only the frequency dimension for the first demodulation reference signal can be variably controlled and the value for the second demodulation reference signal can be fixed. Alternatively, the value for the first demodulation reference signal may be fixed and only the frequency dimension for the second demodulation reference signal may be variably controlled.

That is, when there are a plurality of types of demodulation reference signals to be inserted, the frequency dimension value is variably controlled with respect to the demodulation reference signal for each type or variable control is performed only with respect to the frequency dimension value of the demodulation reference signal for at least any one type It is possible.

Fig. 25 shows an example in which the intervals of the demodulation reference signals are varied in the time dimension when two types of demodulation reference signals are used. That is, the demodulation reference signal shows an example in which the frequency dimensions N1 and N2 are fixed and the intervals thereof are variably controlled in the time dimensions M1 and M2.

In this case as well, when a plurality of types of demodulation reference signals are inserted, the time dimension is variably controlled with respect to the demodulation reference signal for each type, or only the time dimension of the demodulation reference signal for at least one type is variably controlled It will be possible.

26 shows an example in which the intervals of the demodulation reference signals are varied in both the time periods M1 and M2 and the frequencies N1 and N2 for the two types of demodulation reference signals. Although not shown, variable control of the frequency (N1) dimension to the first demodulation reference signal and variable control of the time (M2) dimension to the second demodulation reference signal will be possible, and as another example, There may be a case in which variable control of the time dimension is performed for the signal and variable control of the frequency dimension is performed for the second demodulation reference signal. That is, Fig. 26 illustrates that variable control can be performed simultaneously with respect to frequency and time dimension.

FIG. 27 shows an example in which a plurality of demodulation reference signals are inserted in various ways, and one of them is selected and used.

Therefore, when transmitting the information of the demodulation reference signal transmission method, when one example is selected and used in a plurality of predetermined reference signal insertion examples as shown in FIG. 27, the index information of the time dimension or the frequency dimension index Information or time dimension and frequency dimension index information are transmitted.

Or if the information related to the selected example is present on both the receiving side and the transmitting side, the number information corresponding to the selected 'one example' may be transmitted. In this case, after a process of transmitting information related to a plurality of predetermined reference signal insertion examples is performed first, the number information for selecting 'one example' '. In addition, it is possible to implement an embodiment in which various methods and demodulation reference signals are inserted, and selectively use the embodiments.

It is also quite possible to use a larger number of demodulation reference signals. As described above, the present invention sets the demodulation reference signal in various forms including the position of the demodulation reference signal, the number of inserted demodulation reference signals, and the type of the demodulation reference signal in controlling insertion of the demodulation reference signal, It is suggested that it can be used by using. Therefore, the demodulation reference signal set in various forms is used to demodulate the data by preferentially providing related information so that both the transmitting side and the receiving side can use the demodulation reference signal through the transmission channel.

In a case where a plurality of types of demodulation reference signals are used as described above, in providing the demodulation reference signal transmission scheme information, instead of providing only the symbol information with respect to the insertion position of the demodulation reference signal, It is necessary to provide information in accordance with the type of the information. Therefore, the demodulation reference signal transmission information includes various information including the insertion position information and the type information for the demodulation reference signal.

Accordingly, the foregoing detailed description should not be construed in any way as limiting and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

10: sensor node 20: central node
21, 22, 40: transmission / reception units 23, 26, 36:
24, 25, 38: Data receiving unit 27: Frequency divider
28, 32: control unit 29, 34: memory
50: Underwater network 62: Ground network
64: management node 110: demodulation reference signal generation unit
111: demodulation reference signal generator 112: memory
113: Control section 120:
130: Time frequency mapper 210: Time frequency demapper
220: Channel estimator 230: Data demodulator

Claims (12)

In underwater communication using a central node that collects detection information from a plurality of sensor nodes that detect underwater information and transmits the same to a terrestrial network,
The entire frequency band that can be used by the central node is divided into small frequency bands, and the divided small frequency bands are allocated to the respective sensor nodes based on the distances between the central node and the plurality of sensor nodes, ,
When performing underwater communication between the central node and an arbitrary sensor node using the allocated small frequency bands, channel estimation to be carried on a carrier according to a predetermined algorithm and transmission of a demodulation reference signal to be used for data demodulation Wherein the reference signal control method comprises the steps of: In underwater communication using a central node that collects detection information from a plurality of sensor nodes that detect underwater information and transmits the same to a terrestrial network,
The entire frequency band that can be used by the central node is divided into small frequency bands, and the divided small frequency bands are allocated to the respective sensor nodes based on the distances between the central node and the plurality of sensor nodes, ,
When carrying out underwater communication between the central node and an arbitrary sensor node using the respective allocated small frequency bands, channel estimation and data to be transmitted on a carrier using data on the underwater characteristic obtained through a test signal, A method of controlling a reference signal of a submersible communication that variably adjusts transmission of a demodulation reference signal to be used for demodulation. 3. The method according to claim 1 or 2,
Wherein the demodulation reference signal variably adjusts the number of insertions, insertion intervals, and insertion types. 3. The method according to claim 1 or 2,
Wherein the demodulation reference signal is variably adjusted in a frequency dimension within a resource block. 3. The method according to claim 1 or 2,
Wherein the demodulation reference signal is variably adjusted in a time dimension within a resource block. In underwater communication using a central node that collects detection information from a plurality of sensor nodes that detect underwater information and transmits the same to a terrestrial network,
The entire frequency band that can be used by the central node is divided into small frequency bands, and the divided small frequency bands are allocated to the respective sensor nodes based on the distances between the central node and the plurality of sensor nodes, ,
When carrying out underwater communication between the central node and an arbitrary sensor node using the respective allocated small frequency bands, it is possible to variably adjust the insertion interval of the demodulation reference signal to be used for channel estimation and data demodulation, A reference signal control device for underwater communication. The method according to claim 6,
When performing underwater communication between the central node and an arbitrary sensor node, a node operating as a transmitting side transmits demodulation reference signal transmission scheme information to a receiving node, and a node operating on the receiving node transmits the demodulation reference signal transmission scheme information And the demodulation reference signal is transmitted between the transmitting side and the receiving side node. The method according to claim 6,
When performing underwater communication between the central node and an arbitrary sensor node, a node operating on the receiving side transmits the demodulation reference signal transmission scheme information to the transmitting node, and then the transmitting node transmits the demodulation reference signal transmission scheme information based on the received reference signal transmission scheme information And the demodulation reference signal is transmitted to the receiving node. 9. The method according to claim 7 or 8,
Wherein the reference signal transmission scheme information is transmitted with corresponding index information of a frequency dimension or a time dimension in a resource block that is variablely controlled in the demodulation reference signal. 10. The method of claim 9,
Wherein the reference signal transmission scheme information is transmitted from a physical layer or a MAC layer. 9. The method according to claim 7 or 8,
Wherein the reference signal transmission scheme information transmits information for selecting one of the examples in a state in which information related to a plurality of predetermined reference signal insertion examples can be confirmed by both the transmission side and the reception side. Reference signal control device. Setting and storing various methods for inserting a demodulation reference signal to be used for demodulating a received signal between a transmitting side and a receiving side for transmitting and receiving a signal in order to detect and collect underwater information;
Selecting one demodulation reference signal inserting method among the plurality of stored demodulation reference signal inserting methods;
Transmitting information on a predetermined demodulation reference signal and the selected demodulation reference signal insertion method in an initial connection procedure between the transmitting side and the receiving side;
Receiving the information, decoding it using a predetermined demodulation reference signal, and recognizing the selected demodulation reference signal inserting method on both the transmitting side and the receiving side; And
And transmitting the underwater information using the perceived demodulation reference signal inserting method.

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