KR101968834B1 - A Rendezvous Point Replacement Scheme for Efficient Drone-based Data Collection in Construction Sites - Google Patents

Abstract

The present invention relates to a rendezvous point replacement method for efficient drone-based data collection at a construction site. A rendezvous point replacement method for collecting drone-based data, which is an aspect of the present invention, includes: a first step of broadcasting the first message around the drones; A second step of measuring a remaining energy amount and RSSI (Received Signal Strength Indication) of the first message corresponding to the first message by a plurality of sensors collecting information related to surroundings; A third step of the plurality of sensors transmitting a second message including the energy remaining amount and the RSSI value to the drones; A fourth step of the drones designating one rendezvous point of the plurality of sensors using the energy remaining amount and the RSSI value; A fifth step of transmitting a third message informing the fact that the drones are designated as the rendezvous points to the designated rendezvous point; A sixth step of the rendezvous point collecting information sensed by a sensor other than the rendezvous point among the plurality of sensors; And a seventh step of transmitting information collected by the rendezvous point to the drones.

Description

A Rendezvous Point Replacement Scheme for Efficient Drone-Based Data Collection in a Construction Site [

The present invention relates to a rendezvous point replacement method for efficient drone-based data collection at a construction site. More particularly, the present invention relates to a method and system for efficiently collecting data through a drone while changing the rendezvous point according to the energy remaining amount of the sensor and the relative distance with the drone.

Unmanned Aerial Vehicle (UAV) is a type of aircraft that can not be directly operated by a person, such as reconnaissance, bombardment, cargo transportation, forest fire monitoring, radiation monitoring, etc., It means a plane carrying dangerous missions.

It is important to safely land the drone at the desired point after completion of the mission. It is necessary to control the landing precisely so that the pilot does not fly when landing on the ground or the landing gear because he or she is not on board.

The landing related navigation system of the unmanned airplane is implemented variously according to the type of the unmanned airplane. Generally, GPS and inertial guidance devices are mainly used for navigation or landing of unmanned airplanes. GPS is preferred because it is cheap and small in size. For example, in the case of a UAV, such as a Predator, which is a type of UAV, a manual control landing is implemented using a precision approach radar and a video camera.

A typical unmanned airplane is a multi-copter.

A multicopter or multirotor means a flying body that gains floating capacity by using two or more rotors in contrast to a fixed-wing flight, and the movement of the flying body is achieved by adjusting the relative rotation speed of each rotor.

In recent years, multi-copter has been attracting new attention in various fields as unmanned aircraft which was mainly used as a military weapon.

For example, it is recognized as a next-generation logistics delivery method, and it is recognized as being infinite possibilities in various fields such as agriculture, disaster relief, broadcasting, and leisure.

Such a multi-copter may be called a 4-, 6-, or 8-rotor helicopter depending on the number of rotors.

On the other hand, Rendezvous points are used to select representative nodes for efficient data collection in drone operation in a wide range of construction sites.

At this time, the rendezvous point may increase the data transmission to the selected node and the neighboring nodes, and energy consumption may be concentrated, which may shorten the network life.

Therefore, there is a growing need for a method that can effectively maintain the rendezvous point for a long period of time by considering a long construction period.

Patent No. KR 10-1586188

In order to solve the above-described problems, the present invention provides a rendezvous point replacement method and system for efficient drone-based data collection at a construction site.

More specifically, the present invention provides a method and system for efficiently collecting data through a drone while changing the rendezvous point according to the energy remaining amount of the sensor and the relative distance to the drone.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are not intended to limit the invention to the precise form disclosed. It can be understood.

According to another aspect of the present invention, there is provided a method for replacing a rendezvous point for collecting drones based data, the method comprising: a first step of broadcasting the first message to the surroundings, the first message informing the location of the drones; A second step of measuring a remaining energy amount and RSSI (Received Signal Strength Indication) of the first message corresponding to the first message by a plurality of sensors collecting information related to surroundings; A third step of the plurality of sensors transmitting a second message including the energy remaining amount and the RSSI value to the drones; A fourth step of the drones designating one rendezvous point of the plurality of sensors using the energy remaining amount and the RSSI value; A fifth step of transmitting a third message informing the fact that the drones are designated as the rendezvous points to the designated rendezvous point; A sixth step of the rendezvous point collecting information sensed by a sensor other than the rendezvous point among the plurality of sensors; And a seventh step of transmitting information collected by the rendezvous point to the drones.

In addition, before the first step, the dron may enter a construction site area. The plurality of sensors may collect information related to the construction site.

In the third step, the plurality of sensors determine whether the energy value and the node value calculated using the RSSI are equal to or greater than preset reference values. And a third step of the first sensor transmitting the second message to the drones, wherein the first sensor has the node value equal to or greater than the reference value.

Also, the calculated node value may be proportional to the energy remaining amount and the RSSI value.

Further, the drones may designate the rendezvous point among the first sensors using the energy remaining amount and the RSSI value.

In addition, in the fourth step, the dron can designate the sensor having the highest node value calculated using the energy level and the RSSI value as the rendezvous point.

In addition, when the rendezvous point is not designated in the fourth step, between the fourth step and the fifth step, the drones are provided between the fourth sensor and the fourth sensor, Step;

If a plurality of rendezvous points are designated in the fourth step, the fourth step is performed again from the first step to the fourth step before proceeding to the fifth step in the fourth step ; ≪ / RTI >

Also, the step 4-2 may be repeatedly performed until the rendezvous point is designated as one rendezvous point.

The method may further include the step of returning to the base station a dron that received the collected information after the seventh step, wherein the drones, the plurality of sensors and the base station use at least one of short- Communication can be performed.

The local area communication includes Bluetooth, Radio Frequency Identification (RFID), infrared data association (IrDA), Ultra-Wideband (UWB), ZigBee and Wi-Fi (Wireless Fidelity) Long distance communications include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), and single carrier frequency division multiple access can do.

According to another aspect of the present invention, there is provided a drones for replacing a rendezvous point, comprising: a plurality of sensors for broadcasting a first message informing a location of the drones around the rendezvous point, Receives a second message including the energy remaining amount and the RSSI value from the plurality of sensors when measuring an energy remaining amount and RSSI (Received Signal Strength Indication) for the first message corresponding to the first message A third rendezvous point indicating a rendezvous point pointing to the rendezvous point is transmitted to the designated rendezvous point using the energy remaining amount and the RSSI value, When a sensor other than the rendezvous point among the plurality of sensors collects information sensed, You can receive information collected by Debu Point.

Further, the drones enter a construction site area, and the plurality of sensors collect information related to the construction site.

Further, the drones may designate the sensor having the highest node value calculated using the energy remaining amount and the RSSI value as the rendezvous point.

In addition, when the rendezvous point is not designated, the drone can designate a predetermined sensor among the plurality of sensors as the rendezvous point.

Also, when a plurality of rendezvous points are designated, the drone may repeat the operation for specifying the rendezvous points.

Also, the drones may repeat the operation for designating the rendezvous point until the rendezvous point is designated as one rendezvous point.

Also, the drones receiving the collected information return to the base station, and the drones, the plurality of sensors, and the base station can communicate using at least one of short-distance communication and long-distance communication.

The local area communication includes Bluetooth, Radio Frequency Identification (RFID), infrared data association (IrDA), Ultra-Wideband (UWB), ZigBee and Wi-Fi (Wireless Fidelity) Long distance communications include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), and single carrier frequency division multiple access can do.

According to another aspect of the present invention, there is provided a plurality of sensors for collecting information related to a periphery for rendezvous point replacement, wherein the drones broadcast a first message indicating its location The plurality of sensors measure the energy remaining amount and the RSSI (Received Signal Strength Indication) for the first message corresponding to the first message, and the plurality of sensors measure the energy remaining amount and the RSSI value A second message to the drones, the drones specifying a rendezvous point of one of the plurality of sensors using the energy remaining amount and the RSSI value, and a third message informing the fact that the rendezvous point is designated, When a rendezvous point is received, the rendezvous point may include the rendezvous point out of the plurality of sensors Collecting information that the sensor is sensing, and may transmit the information gathered by the drone.

The plurality of sensors may be configured to determine whether the energy level and the node value calculated using the RSSI are equal to or greater than a preset reference value, And send the second message to the drones.

Also, the calculated node value may be proportional to the energy remaining amount and the RSSI value.

According to another aspect of the present invention, there is provided a rendezvous point replacement system for data collection including a plurality of sensors for collecting information relating to a drone and its surroundings, Wherein the plurality of sensors measure RSSI (Received Signal Strength Indication) of the energy remaining amount and the first message corresponding to the first message, And transmits a second message including the remaining amount and the RSSI value to the drones, the drones designating one rendezvous point of the plurality of sensors using the energy remaining amount and the RSSI value, To the designated rendezvous point, and the rendezvous point is transmitted to the designated rendezvous point, Group a plurality of information collection by the sensors, except for the rendezvous point of the sensing sensor, and may be the rendezvous point is to transmit the information gathered by the drone.

In order to solve the above-described problems, the present invention can provide a rendezvous point replacement method and system for efficient drone-based data collection at a construction site.

More specifically, the present invention can provide a method and system for efficiently collecting data through a drone while changing the rendezvous point according to the energy remaining amount of the sensor and the relative distance to the drone.

Also, according to the present invention, since the energy remaining amount of the sensor is considered, the lifetime of the network can be increased and the flying distance of the drone can be reduced as compared with the conventional techniques.

In addition, according to the present invention, since the relative distance with respect to the drone is considered, the moving distance of the drone can be reduced by selecting a rendezvous point that is geographically close to the drone point.

It should be understood, however, that the effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned may be clearly understood by those skilled in the art to which the present invention belongs It will be possible.

FIG. 1 shows an example of a general plan view of a quadruple copter, which is a type of unmanned airplane.
FIG. 2 is a diagram illustrating an operation principle of a general quadruplector related to the present invention.
3 is a block diagram of a rendezvous point replacement system for efficient drone-based data collection in a construction site proposed by the present invention.
FIG. 4 shows an example of a block diagram of a base station, a drone or a sensor node applied to the system proposed by the present invention.
5 is a view for explaining a process of collecting construction site data through a drone in connection with the present invention.
FIG. 6 is a flowchart illustrating a process of collecting construction site data through a conventional drone, in accordance with the present invention.
7 is a flowchart illustrating a process of collecting construction site data through the drone proposed by the present invention.
FIG. 8 is a table summarizing what each term means in the formula applied to the present invention, and FIG. 9 is a table summarizing the meaning of the setting parameters.
FIG. 10 shows a graph comparing the lifetime of a network when a conventional technology and a system according to the present invention are applied.
FIG. 11 is a graph comparing average flight times of drones when a conventional technique and a system according to the present invention are applied.

An unmanned aerial vehicle (UAV) or simply a drone is a flight craft designed to carry out a designated mission without boarding the pilot.

It is also called a drone because it is buzzing in a different name of an unmanned aircraft.

It is sometimes referred to as the abbreviation of Uninhabited Aerial (Air) Vehicle, emphasizing that there is no pilot on the ground.

Unmanned aircrafts operate in conjunction with independent systems or with space and ground systems.

It is equipped with a variety of equipment (optical, infrared, radar sensor, etc.) to monitor, reconnaissance, induce precise attack weapons, perform telecommunication / information relay, EA / EP and Decoy, The weapon itself has been developed and put into practical use, and it has attracted attention as a major military force in the future.

A typical unmanned airplane is a multi-copter.

A multicopter or multirotor means a flying body that gains floating capacity by using two or more rotors in contrast to a fixed-wing flight, and the movement of the flying body is achieved by adjusting the relative rotation speed of each rotor.

Hereinafter, for convenience of explanation, it is assumed that the type of the unmanned airplane to which the present invention is applied is a quad-copter.

However, the contents of the present invention are not limited to the quad-copter, and it is obvious that the present invention can be applied to other kinds of unmanned aerial vehicles.

FIG. 1 shows an example of a general plan view of a quadruple copter, which is a type of unmanned airplane.

1, the quad-copter 100 includes a body 10, four arms 20 fixed radially from the body 10, and a motor 40 provided on each arm 20 And four propellers 30 that are rotationally driven.

The quadcopter 100 thus configured controls the rotational speed of each propeller 30 to perform thrust and attitude control necessary for the flight.

FIG. 2 is a diagram illustrating an operation principle of a general quadruplector related to the present invention.

In Fig. 2, arrows of the respective propellers indicate the magnitude of the rotational direction and speed.

2, the first propeller 31 and the third propeller 33 disposed opposite to each other and the second propeller 32 and the fourth propeller 34 are rotated at the same rotational speed in the opposite directions (A), the quadcopter is height-adjusted or hovered in a parallel posture according to the magnitude of the rotational speed.

In addition, yawing, rolling and pitching can be performed by varying the rotational speed of a particular propeller among the four propellers.

For example, by controlling the rotational speeds of the first propeller 31 and the third propeller 33, the second propeller 32 and the fourth propeller 34 to be different from each other, yaw control of the air vehicle can be performed b), the pitching control of the airplane can be controlled by controlling the rotational speed of only a specific propeller among the four propellers.

The quad-copter that operates in this way is controlled through pitch control when it wants to move in a specific direction, which is the basic operation principle in multi-copter regardless of the number of propellers.

On the other hand, geotechnical engineering, which is a field of civil engineering, is a discipline that treats the ground in situ such as tunnels, bridge foundations, and slopes.

Most of the civil engineering works include engineering related to geotechnical engineering. The samples collected in the field are tested indoors or directly tested in the field to understand the engineering characteristics of the ground materials. Based on these characteristics, the civil engineering structures are designed And construction.

However, it is practically impossible to grasp the heterogeneous and anisotropic properties of the soil, ie, soil and rock. Therefore, the stability of the structure is secured by monitoring the state and performance of the structure during construction or public use with various sensors .

Here, the collection of the monitoring data is generally performed by a manpower, and data is collected through a communication network.

Recently, a method of collecting data using the above-described quad-copter 100, that is, a drone, has been proposed.

As described above, in the case of construction site, it is not necessary to collect the measurement data in real time, and there is a work type in which the evaluation of the site condition can be sufficiently performed even after several hours of collection.

In other words, if a storage module is installed in a battery-powered measurement sensor to store data, and a drone, a data collecting device, periodically accesses the measurement sensor and downloads the measurement data through short- It can be a suitable technology suitable for

Considering years of civil engineering work in general, energy saving is an issue when using battery powered sensors.

The method in which the drone 100 accesses all of the sensors one by one and the data is downloaded from the sensor through the near field communication may not be preferable from the viewpoint of energy saving in both the drones and the sensors.

In addition, it is not safe for drone (100) to actively fly the construction site in consideration of the circumstances of the variable and rough construction site.

Therefore, if one of the sensors installed at the construction site is designated as a rendezvous point with the drones 100, and the other sensors transmit data to the designated sensor, the drones access only the sensor set as the rendezvous point, You can get it.

This method is safe and can be efficient in terms of energy savings in sensors and drones.

However, if the rendezvous point is fixed to only one sensor, the battery of the sensor is continuously consumed, and the function is lost early, so it is necessary to effectively replace the rendezvous point.

Therefore, in order to solve the above problem, the present invention provides a rendezvous point replacement method and system for efficient drone-based data collection at a construction site.

More specifically, the present invention provides a method and system for efficiently collecting data through a drone while changing the rendezvous point according to the energy remaining amount of the sensor and the relative distance to the drone.

Prior to the detailed description of the present invention, a configuration of a rendezvous point replacement system for efficient drone-based data collection in a construction site proposed by the present invention will be described with reference to the drawings.

3 is a block diagram of a rendezvous point replacement system for efficient drone-based data collection in a construction site proposed by the present invention.

Referring to FIG. 3, a rendezvous point replacement system for efficient drone-based data collection in a construction site proposed by the present invention may include the drones 100, the base stations 200, and the sensor nodes 400 described above.

Here, it is possible to provide a function of controlling the operation of the drones 100 by communicating with the base station 200.

In addition, the sensor 400 senses a state related to the construction site such as the open / close state of the system, the location, the presence or absence of contact, the orientation, the acceleration / deceleration, etc. and generates a sensing signal for controlling the operation of the system.

The sensor 400 may include a proximity sensor 1141.

The sensor 400 according to the present invention may be arranged in a plurality of construction sites, and at least one of the plurality of sensors 400 may be designated as a rendezvous point 300.

That is, one of the sensors 400 installed on the construction site is designated as a rendezvous point 300 communicating with the drone 100, and the other sensors 400 transmit the collected information to the rendezvous point 300, The drone 100 can access the sensor set to the rendezvous point 300 and receive data.

Meanwhile, a short distance communication or a long distance communication method may be applied between the drone 100, the base station 200 and the sensor node 400.

The local area communication may include Bluetooth, Radio Frequency Identification (RFID), infrared data association (IrDA), Ultra Wideband (UWB), ZigBee, and Wi-Fi (Wireless Fidelity).

Further, the long-distance communication may be performed by using a code division multiple access (CDMA), a frequency division multiple access (FDMA), a time division multiple access (TDMA), an orthogonal frequency division multiple access (OFDMA), a single carrier frequency division multiple access . ≪ / RTI >

Meanwhile, FIG. 4 shows an example of a block diagram of a base station, a drone or a sensor node applied to the system proposed by the present invention.

At least some of the techniques described in FIG. 4 may be components of a base station, a drone, or a sensor node.

4, a base station, a drones or a sensor node 1100 (hereinafter referred to as a device) according to the present invention includes a wireless communication unit 1110, an A / V input unit 1120, a user input unit 1130, A sensing unit 1140, an output unit 1150, a memory 1160, an interface unit 1170, a control unit 1180, a power supply unit 1190, and the like.

The components shown in Fig. 4 are not essential, and a device having more or fewer components may be implemented.

Hereinafter, the components will be described in order.

The wireless communication unit 1110 may include one or more modules that enable wireless communication between the device 1100 and the wireless communication system or between the device 1100 and the network in which the device 1100 is located. For example, the wireless communication unit 1110 may include a broadcast receiving module 111, a mobile communication module 1112, a wireless Internet module 1113, a short range communication module 1114, a location information module 1115, .

The broadcast receiving module 1111 receives broadcast signals and / or broadcast-related information from an external broadcast management server through a broadcast channel.

The broadcast channel may include a satellite channel and a terrestrial channel. The broadcast management server may be a server for generating and transmitting broadcast signals and / or broadcast-related information, or a server for receiving broadcast signals and / or broadcast-related information generated by the server and transmitting the broadcast signals and / or broadcast- related information to the device 1100. The broadcast signal may include a TV broadcast signal, a radio broadcast signal, a data broadcast signal, and a broadcast signal in which a data broadcast signal is combined with a TV broadcast signal or a radio broadcast signal.

The broadcast-related information may refer to a broadcast channel, a broadcast program, or information related to a broadcast service provider. The broadcast-related information may also be provided through a mobile communication network. In this case, it may be received by the mobile communication module 1112.

The broadcast-related information may exist in various forms. For example, an EPG (Electronic Program Guide) of DMB (Digital Multimedia Broadcasting) or an ESG (Electronic Service Guide) of Digital Video Broadcast-Handheld (DVB-H).

For example, the broadcast receiving module 1111 may be a Digital Multimedia Broadcasting-Terrestrial (DMB-T), a Digital Multimedia Broadcasting-Satellite (DMB-S), a Media Forward Link Only A digital broadcasting system such as DVB-CB, OMA-BCAST, or Integrated Services Digital Broadcast-Terrestrial (ISDB-T). Of course, the broadcast receiving module 1111 may be adapted to other broadcasting systems as well as the digital broadcasting system described above.

The broadcast signal and / or broadcast related information received through the broadcast receiving module 1111 may be stored in the memory 1160.

The mobile communication module 1112 transmits and receives radio signals to at least one of a base station, an external device 1100, and a server on a mobile communication network. The wireless signal may include various types of data according to a voice signal, an image signal, or a text / multimedia message transmission / reception.

The wireless Internet module 1113 refers to a module for wireless Internet access, and may be embedded in the device 1100 or externally.

WLAN (Wi-Fi), Wibro (Wireless broadband), Wimax (World Interoperability for Microwave Access), HSDPA (High Speed Downlink Packet Access) and the like can be used as the technology of the wireless Internet.

The short-range communication module 1114 refers to a module for short-range communication. Bluetooth, Radio Frequency Identification (RFID), Infrared Data Association (IrDA), Ultra Wideband (UWB), ZigBee, and the like can be used as the short range communication technology.

The location information module 1115 is a module for obtaining the location of the device 1100, and a representative example thereof is a Global Position System (GPS) module. According to the current technology, the GPS module 1115 calculates distance information and accurate time information from three or more satellites, and then applies a trigonometric method to the calculated information to generate a three-dimensional string of latitude, longitude, The location information can be accurately calculated. At present, a method of calculating position and time information using three satellites and correcting an error of the calculated position and time information using another satellite is widely used. In addition, the GPS module 1115 can calculate speed information by continuously calculating the current position in real time.

Referring to FIG. 4, an A / V (Audio / Video) input unit 1120 is for inputting an audio signal or a video signal, and may include a camera 1121 and a microphone 1122. The camera 1121 processes an image frame such as a still image or a moving image obtained by the image sensor in the video communication mode or the photographing mode. The processed image frame can be displayed on the display portion 1151. [

The image frame processed by the camera 1121 can be stored in the memory 1160 or transmitted to the outside through the wireless communication unit 1110. [

At this time, two or more cameras 1121 may be provided depending on the use environment.

For example, the camera 1121 may include first and second cameras 1121a and 1121b for shooting 3D images on the opposite side of the display unit 1151 of the device 100, A third camera 1121c for self-photographing of the user may be provided in a part of the surface of the display unit 1151 on which the display unit 1151 is provided.

In this case, the first camera 1121a is for capturing a left eye image, which is a source image of a 3D image, and the second camera 1121b may be for capturing a right eye image.

The microphone 1122 receives an external sound signal by a microphone in a communication mode, a recording mode, a voice recognition mode, or the like, and processes it as electrical voice data. The processed voice data can be converted into a form that can be transmitted to the mobile communication base station through the mobile communication module 112 when the voice data is in the call mode, and output. The microphone 1122 may be implemented with various noise reduction algorithms for eliminating noise generated in the process of receiving an external sound signal.

The user input unit 1130 generates input data for controlling the operation of the device 1100 by the user.

The user input unit 1130 may receive from the user a signal designating two or more contents among the displayed contents according to the present invention. A signal for designating two or more contents may be received via the touch input, or may be received via the hard key and soft key input.

The user input unit 1130 may receive an input from the user to select the one or more contents. It may also receive input from a user to create icons associated with functions that the device 1100 can perform.

The user input unit 1130 may include a direction key, a key pad, a dome switch, a touch pad (static / static), a jog wheel, a jog switch, and the like.

The sensing unit 140 senses the current state of the device 1100 such as the open / closed state of the device 1100, the position of the device 1100, the presence of the user, the orientation of the device, And generates a sensing signal for controlling the operation of the sensor. It is also possible to sense whether the battery 1190 is powered on, whether the interface unit 1170 is connected to an external device, and the like. Meanwhile, the sensing unit 1140 may include a proximity sensor 1141. The proximity sensor 141 will be described later in relation to the touch screen.

The output unit 1150 is for generating output related to visual, auditory or tactile sense and includes a display unit 1151, an acoustic output module 1152, an alarm unit 1153, a haptic module 154 and a projector module 1155, and the like.

The display unit 1151 displays (outputs) the information processed by the device 100. [ For example, when the device is in the call mode, a UI (User Interface) or GUI (Graphic User Interface) associated with the call is displayed. When the device 100 is in the video communication mode or the photographing mode, it displays the photographed and / or received image or the UI and the GUI.

In addition, the display unit 1151 according to the present invention supports 2D and 3D display modes.

That is, the display unit 1151 according to the present invention may have a configuration in which a switch liquid crystal 1151b is combined with a general display device 1151a as shown in FIG. 4 below. Then, the optical parallax barrier 50 is operated by using the switch liquid crystal 1151b to control the traveling direction of the light, so that different lights can be separated from the left and right eyes. Therefore, when a combined image of the right eye image and the left eye image is displayed on the display device 1151a, the user can see the image corresponding to each eye and feel as if the image is displayed as a three-dimensional object.

That is, under the control of the control unit 1180, the display unit 1151 drives only the display device 1151a without driving the switch liquid crystal 1151b and the optical parallax barrier 50 in the 2D display mode Performs normal 2D display operation.

The display unit 1151 drives the switch liquid crystal 1151b and the optical parallax barrier 50 and the display device 1151a under the control of the control unit 1180 in the 3D display mode, 1151a to perform a 3D display operation.

The display unit 151 may be a liquid crystal display (LCD), a thin film transistor-liquid crystal display (TFT LCD), an organic light-emitting diode (OLED) A flexible display, and a three-dimensional display (3D display).

Some of these displays may be transparent or light transmissive so that they can be seen through. This can be referred to as a transparent display, and a typical example of the transparent display is TOLED (Transparent OLED) and the like. The rear structure of the display portion 1151 may also be of a light transmission type. With this structure, the user can see an object located behind the body of the device 1100 through the area occupied by the display portion 1151 of the device 1100 body.

There may be two or more display portions 1151 depending on the implementation of the device 1100. [ For example, in the device 100, a plurality of display portions may be spaced apart from one another or integrally disposed, and may be disposed on different surfaces, respectively.

(Hereinafter, referred to as a 'touch screen') in which a display unit 1151 and a sensor (hereinafter, referred to as 'touch sensor') that detects a touch operation form a mutual layer structure, It can also be used as an input device. The touch sensor may have the form of, for example, a touch film, a touch sheet, a touch pad, or the like.

The touch sensor may be configured to convert a change in a pressure applied to a specific portion of the display portion 1151 or a capacitance generated in a specific portion of the display portion 1151 into an electrical input signal. The touch sensor can be configured to detect not only the position and area to be touched but also the pressure at the time of touch.

If there is a touch input to the touch sensor, the corresponding signal (s) is sent to the touch controller (not shown). The touch controller processes the signal (s) and transmits corresponding data to controller 1180. Thus, the control unit 1180 can know which area of the display unit 1151 is touched or the like.

The proximity sensor 1141 may be disposed within an interior area of the device to be wrapped by the touch screen or in the vicinity of the touch screen. The proximity sensor refers to a sensor that detects the presence or absence of an object approaching a predetermined detection surface or a nearby object without mechanical contact using the force of an electromagnetic field or infrared rays. The proximity sensor has a longer life span than the contact sensor and its utilization is also high.

Examples of the proximity sensor include a transmission type photoelectric sensor, a direct reflection type photoelectric sensor, a mirror reflection type photoelectric sensor, a high frequency oscillation type proximity sensor, a capacitive proximity sensor, a magnetic proximity sensor, and an infrared proximity sensor. And to detect the proximity of the pointer by the change of the electric field along the proximity of the pointer when the touch screen is electrostatic. In this case, the touch screen (touch sensor) may be classified as a proximity sensor.

Hereinafter, for convenience of explanation, the act of recognizing that the pointer is positioned on the touch screen while the pointer is not in contact with the touch screen is referred to as " proximity touch & The act of actually touching the pointer on the screen is called " contact touch. &Quot; The position where the pointer is proximately touched on the touch screen means a position where the pointer is vertically corresponding to the touch screen when the pointer is touched.

The proximity sensor detects a proximity touch and a proximity touch pattern (e.g., a proximity touch distance, a proximity touch direction, a proximity touch speed, a proximity touch time, a proximity touch position, a proximity touch movement state, and the like). Information corresponding to the detected proximity touch operation and the proximity touch pattern may be output on the touch screen.

The audio output module 1152 can output audio data received from the wireless communication unit 1110 or stored in the memory 1160 in a call signal reception mode, a call mode or a recording mode, a voice recognition mode, a broadcast reception mode, The sound output module 1152 also outputs sound signals associated with functions performed by the device 1100 (e.g., call signal reception tones, message reception tones, etc.). The sound output module 1152 may include a receiver, a speaker, a buzzer, and the like.

The memory 1160 may store a program for processing and controlling the controller 1180, and may perform functions for temporarily storing input / output data. The frequency of use of each of the data may also be stored in the memory 1160. In addition, the memory unit 1160 may store data related to vibration and sound of various patterns that are output upon touch input on the touch screen.

In addition, the memory 1160 stores a web browser displaying a 3D or 2D web page, in accordance with the present invention.

The memory 1160 may be a flash memory type, a hard disk type, a multimedia card micro type, a card type memory (for example, SD or XD memory, etc.) ), A random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a programmable read- A magnetic disk, an optical disk, a memory, a magnetic disk, or an optical disk. The device 1100 may operate in association with a web storage that performs the storage function of the memory 1160 on the Internet.

The interface unit 1170 serves as a path for communication with all external devices connected to the device 1100. The interface unit 1170 receives data from an external device or supplies power to each component in the device 1100 or allows data in the device 1100 to be transmitted to an external device. For example, a wired / wireless headset port, an external charger port, a wired / wireless data port, a memory card port, a port for connecting a device having an identification module, an audio I / O port, A video input / output (I / O) port, an earphone port, and the like may be included in the interface unit 170.

The identification module is a chip for storing various information for authenticating the use right of the device 1100. The identification module includes a user identification module (UIM), a subscriber identity module (SIM), a universal user authentication module A Subscriber Identity Module (USIM), and the like. Devices with identification modules (hereinafter referred to as "identification devices") can be manufactured in a smart card format. Thus, the identification device can be connected to the device 1100 via the port.

The interface unit may be a path through which power from the cradle is supplied to the device 1100 when the device 1100 is connected to an external cradle or various command signals input by the user to the cradle may be transmitted to the device . The various command signals input from the cradle or the power source may be operated as a signal for recognizing that the device is correctly mounted on the cradle.

A controller 1180 typically controls the overall operation of the device. For example, voice communication, data communication, video communication, and the like. The control unit 1180 may include a multimedia module 1181 for multimedia playback. The multimedia module 1181 may be implemented in the control unit 1180 or may be implemented separately from the control unit 1180.

The control unit 1180 may perform a pattern recognition process for recognizing handwriting input or drawing input performed on the touch screen as characters and images, respectively.

When the display unit 1151 is formed of an organic light-emitting diode (OLED) or a TOLED (Transparent OLED), the controller 1180 controls the display unit 1151, When the preview image is pulled up on the screen of the organic light-emitting diode (OLED) or the TOLED (Transparent OLED) and the size of the preview image is adjusted according to the user's operation, The power consumption of the power source supplied from the power supply unit 1190 to the display unit 151 can be reduced by turning off the driving of the pixels in the second area except for the first area where the preview image with the adjusted preview image is displayed.

The power supply unit 1190 receives external power and internal power under the control of the controller 1180 and supplies power required for operation of the respective components.

The various embodiments described herein may be embodied in a recording medium readable by a computer or similar device using, for example, software, hardware, or a combination thereof.

According to a hardware implementation, the embodiments described herein may be implemented as application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays May be implemented using at least one of a processor, controllers, micro-controllers, microprocessors, and other electronic units for performing other functions. In some cases, The embodiments described may be implemented by the controller 1180 itself.

According to a software implementation, embodiments such as the procedures and functions described herein may be implemented in separate software modules. Each of the software modules may perform one or more of the functions and operations described herein. Software code can be implemented in a software application written in a suitable programming language. The software code is stored in the memory 1160 and can be executed by the control unit 1180. [

On the other hand, since the sensor nodes 400 distributed on the construction site are difficult to replace batteries, an efficient data transmission method is important in order to operate with a limited energy.

In addition, determining the path of the drone 100 when collecting data has a significant effect on overall network lifetime and data merge cost.

A number of studies have been proposed to determine the proper path for efficient data collection and an optimal path search algorithm such as TSP (Traveling Salesman Problem) and Minimum Spanning Tree has been introduced for optimal data collection of mobile sinks.

Konstantopoulos proposed a method of collecting data by constructing a tree in the network topology and allocating a mobile agent to each tree.

The tree-based data collection method proposed here has a problem in that the energy consumption of the node closer to the root node is large, which leads to uneven energy consumption.

In order to consume energy evenly in the wireless sensor network, a number of hierarchical clustering routing techniques have been studied.

LEACH is a representative cluster-based hierarchical routing protocol.

In LEACH, sensor nodes are grouped into clusters at certain intervals and head nodes are selected for each cluster. The surrounding nodes

And transmits the sensed data to the head node and finally to the sink node.

However, since the cluster head has a higher energy burden than the ordinary node, it is important to keep the energy consumption evenly distributed among the ordinary nodes for a certain period of time.

Each round is composed of a setup phase and a stable state phase. In the setup phase, a head node is selected and clustering is performed around the head node. In the stable state phase, data collected by the sensor nodes is transmitted to the head node, Nodes are transmitted to the sink node in an efficient manner, such as merge.

The L-LEACH algorithm improves the LEACH algorithm by considering the energy consumption of the sensor node. In the selection process of the head node, the selection threshold of the node with low energy level is lowered and the probability of selecting the node with smaller battery is lowered.

That is, a simple application method proportional to the initial energy to energy ratio can reduce the number of cluster head nodes when energy is low.

However, there is a problem that this method causes an unbalance of energy consumption and shortens the network life.

In order to solve this problem, according to the present invention, the rendezvous point 300 is exchanged according to the energy remaining amount of the sensor 400 and the distance between the drones 100 and the sensor nodes 400, And the like.

In the rendezvous point 300 replacement technique, it is an important technical feature to balance the battery consumption of the sensors 400 considering the energy remaining amount.

In addition, the present invention may reduce the travel distance of the drones 100 by selecting a rendezvous point 300 that is geographically close to the drones 100 by reflecting the relative distance with the drones 100.

Before describing specific technical features of the present invention, a process of collecting conventional construction site data will be described.

FIG. 5 is a diagram illustrating a process of collecting construction site data through a drone in accordance with the present invention. FIG. 6 is a flowchart illustrating a process of collecting construction site data through a conventional drone to be.

5, when the drone 100 collects data while visiting a construction site through an arbitrary path, it is not possible to collect data by directly communicating with scattered sensors 400 attached to parts of a construction site and equipment Do.

As shown in FIG. 5, one rendezvous point 300 for collecting the entire construction site data is selected.

The rendezvous point 300 collects and merges data from various sensors 400 in the construction site and transmits the merged data to the drone 100 when the drone 100 enters within its communication radius.

6, a conventional method includes the steps of designating a rendezvous point among a plurality of sensors 400, collecting and merging data from a plurality of sensors 400 having different rendezvous points 300 (S11 , When the drones 100 are within the communication radius of the rendezvous point 300, the rendezvous point 300 transmits the merged data to the drones 100 (S12) and the drones 100 (Step S13).

In step S10, the rendezvous point 300 selects a rendezvous point 300 randomly according to a probability, such as LEACH, in data collection using the drones 100, A method of selecting the rendezvous point 300 on the selected flight path can be used.

However, in the conventional data collection using the drone, the rendezvous point 300 selection methods do not take into account the energy remaining amount of the sensor nodes 400 operating on the basis of the battery, which causes excessive energy consumption of the rendezvous point 300 Thereby causing a problem of shortening the lifetime of the entire wireless sensor network.

In order to solve such a problem, according to the present invention, by selecting a node having a large energy amount and a short distance from the drones 100 as the rendezvous point 300, the lifetime of the wireless sensor network and the distance of flight of the drones 100 are increased It is possible to efficiently collect construction site data without additional battery replacement of the installed sensor nodes 400.

7 is a flowchart illustrating a process of collecting construction site data through the drone proposed by the present invention.

Referring to FIG. 7, the first step S100 of the drones 100 entering the construction site zone 1 proceeds.

Thereafter, a step S200 of broadcasting the message indicating the location of the drones 100 to the surroundings is performed.

In addition, the plurality of sensors 400 collecting data related to the construction site performs the step S300 of measuring the energy amount of the sensor 400 and the RSSI for the message.

The plurality of sensors 400 determine whether the node value calculated using the energy remaining amount of the sensor 400 and the RSSI is equal to or greater than a preset reference value (S400). If the node value among the plurality of sensors 400 is equal to or greater than the reference value At least one sensor transmits its node value to the drones (S500).

As mentioned above, in order to extend the life of the wireless sensor network, it is important to maintain the energy consumption of each sensor node 400 equally.

Since the rendezvous point 300 consumes energy more than the general sensor nodes 400, it is necessary to replace the rendezvous point 300 every data collection period of the drone.

)보다 작을 때만 새로운 랑데부 포인트(300)의 후보가 될 수 있다.In order to select the rendezvous point 300, in step S300 to step S500 according to the present invention, each sensor node 400 calculates a threshold value and a random value between 0 and 1 And the random number is a threshold value (

), It can be a candidate for a new rendezvous point 300 only.

8 is a table summarizing what each term means in Equation 1 and other equations applied to the present invention.

The threshold value in Equation (1) can be roughly divided into a portion that reflects the energy level of the sensor node and the distance from the drones.

Here, the portion that reflects the energy remaining amount compares the remaining remaining amount of the node with the energy remaining amount average of all the nodes.

In addition, when the energy level of the corresponding node is higher than the overall average, the possibility of being selected as the rendezvous node 300 increases, and in the opposite case, the possibility of selection becomes lower.

The portion that reflects the distance between the sensor node 400 and the drones 100 is determined through Received Signal Strength Indication (RSSI) measurement.

)를 측정한다. That is, when a dron enters a drone, the RSSI

).

)와 가까워져 랑데부 노드(300)로 선정될 가능성이 높아지고, 거리가 멀수록 최소 RSSI(

)와 가까워져 랑데부 노드(300)로 선정될 가능성이 낮아진다.The RSSI measured here is the maximum RSSI

) To be selected as the rendezvous node 300, and as the distance increases, the minimum RSSI

And is less likely to be selected as the rendezvous node 300.

After step S500, the drone 100 can select the rendezvous point 300 as the first sensor having the highest node value among the received node values (S600).

Since the rendezvous point 300 in the step S600 is based on probability, the present invention may not select a rendezvous point or may select two or more rendezvous points at the same time.

In order to solve this problem, when the rendezvous point 300 is not selected, the rendezvous point 300 does not change, and the existing rendezvous point 300 sequentially performs data collection and data transfer to the drone 100 .

In addition, when two or more rendezvous points 300 are selected, a tie-breaking function can be utilized as shown in Equation (2) below.

As described above, the nodes selected by the rendezvous point 300 transmit their current energy levels and the RSSI used in the calculation of the threshold value of Equation (1) when transmitting a broadcasting message informing whether they are selected or not .

을 계산하고, 값이 0.5 이상이면 i 노드를, 0.5 미만이면 j 노드를 랑데부 포인트(300)로 선정하게 된다.At this time, when each node receives a message from two rendezvous points,

If the value is greater than or equal to 0.5, an i-th node is selected. If the value is less than 0.5, a j-th node is selected as the rendezvous point 300.

In Equation (1) and other equations applied to FIG. 8, each term is applied to Equation (2).

If the drones 100 are within the communication radius of the rendezvous point 300, the rendezvous point 300 collects and merges data from the plurality of other sensors 400 (S700) The point 300 transmits the merged data to the drones 100 and proceeds to the step S900 in which the drones 100 acquiring the merged data communicate with the base stations 200 and the like and return.

That is, when the drone 100 moves to the corresponding site for data collection and transmits its arrival to the neighboring node 400, the sensor node 400 determines the distance to the dron 100, Measure the RSSI value.

Also, a rendezvous point 300 replacement operation is performed immediately before the drones 100 stay for data collection at the site.

), 측정된 RSSI(

)를 포함한 메시지를 알리고, 주변 노드들(400)로부터 데이터를 수집한다. To this end, each node of the site calculates a threshold value according to Equation (1), and a newly selected rendezvous point 300 informs neighboring nodes 400 of their address, current energy level

), Measured RSSI (

), And collects data from neighboring nodes (400).

If a new rendezvous point 300 is not selected until the drone 100 collects data, if the existing rendezvous points are successively subjected to data collection and two or more rendezvous points 300 are selected, The tie breaking function is iteratively performed to determine one rendezvous point 300.

The drone 100 returns to the BS 200 after completing the transmission of the data of the site from the rendezvous point 300.

The inventor of the present invention has demonstrated through simulation the effect of the present invention described above.

That is, the inventors of the present invention compared the proposed technique with LEACH and L-LEACH.

FIG. 9 is a table summarizing the meaning of the setting parameters, showing the set values used in the simulation, and the simulation was performed in SIDnet-SWANS.

FIG. 10 shows a graph comparing the lifetime of a network when a conventional technology and a system according to the present invention are applied.

Referring to FIG. 10, a comparison result of the number of surviving nodes 400 according to each technique-specific round is shown.

Since the rendezvous point 300 is generated at an arbitrary position in the case of LEACH, the selection of the rendezvous point 300 is concentrated in some areas, resulting in an increase in energy consumption.

In the case of the L-LEACH, since the rendezvous point 300 is selected in consideration of the energy remaining amount and the distance, the problem such as LEACH is reduced, but the rendezvous point 300 is located at the center of the field It causes concentrated problems.

In the proposed scheme, since the rendezvous point 300 is selected by taking into consideration not only the amount of energy but also the location of the dynamic drones, the rendezvous points 300 are uniformly distributed in other techniques and the network lifetime is increased.

11 is a graph showing a comparison of average flight times of drones when the conventional technique and the system according to the present invention are applied.

Referring to FIG. 11, the result of comparing the average flying distance of the drones for 180 rounds in which the wireless sensor network is maintained (more than 40% of nodes survive) is shown.

First, since LEACH does not reflect the position of the drones 100, the distance of the drone's flying distance is significant and the average flying distance is longest every round.

Next, in the case of L-LEACH, the variation width per round is not large because the number of times the drone 100 visits the center portion of the field is large.

In the proposed scheme, since the dynamic entry position change of the drone 100 is considered, the sensor node closest to the drone 100 is selected as the rendezvous point 300, which is the shortest distance in the average.

Currently, studies are underway to install various sensors and collect data using a drone (100) remotely for accurate and efficient data collection in a wide range of civil engineering sites.

When the drone 100 collects data by collaborating with a wireless sensor network on the ground, it is impossible for the drone to directly communicate with all of the sensor nodes. Therefore, a rendezvous point that collects the data of the sensor nodes and transmits them to the drone The rendezvous point 300 needs energy more than other nodes 400, so it is necessary to periodically replace the rendezvous point 300. The energy remaining amount of the node and the dynamic distance between the rendezvous point 300 and the drones Rendezvous node replacement method considering change is proposed.

Simulation results show that the proposed scheme can extend the lifetime of the network and reduce the flying distance of the drones compared to the existing techniques.

The above-described embodiments of the present invention can be implemented by various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof. In the case of hardware implementation, the method according to embodiments of the present invention may be implemented in one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs) , FPGAs (Field Programmable Gate Arrays), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of an implementation by firmware or software, the method according to embodiments of the present invention may be implemented in the form of a module, a procedure or a function for performing the functions or operations described above. The software code can be stored in a memory unit and driven by the processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various well-known means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The foregoing description of the preferred embodiments of the invention disclosed herein has been presented to enable any person skilled in the art to make and use the present invention. While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. For example, those skilled in the art can utilize each of the configurations described in the above-described embodiments in a manner of mutually combining them. Accordingly, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above description should not be construed in a limiting sense in all respects 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. The present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. In addition, claims that do not have an explicit citation in the claims may be combined to form an embodiment or be included in a new claim by amendment after the filing.

Claims (23)

A rendezvous point replacement method for drones based data collection,
A first step of broadcasting the first message to the surroundings, the first message informing the location of the drones;
A second step of measuring a remaining energy amount and RSSI (Received Signal Strength Indication) of the first message corresponding to the first message by a plurality of sensors collecting information related to surroundings;
A third step of the plurality of sensors transmitting a second message including the energy remaining amount and the RSSI value to the drones;
A fourth step of the drones designating one rendezvous point of the plurality of sensors using the energy remaining amount and the RSSI value;
A fifth step of transmitting a third message informing the fact that the drones are designated as the rendezvous points to the designated rendezvous point;
A sixth step of the rendezvous point collecting information sensed by a sensor other than the rendezvous point among the plurality of sensors; And
And a seventh step in which the rendezvous point transmits information collected by the drones,

In the third step,
A third step of the plurality of sensors determining whether the energy value and the node value calculated using the RSSI are equal to or greater than preset reference values; And
And a third step of the first sensor transmitting the second message to the drones, the node having a node value greater than or equal to the reference value among the plurality of sensors,
Wherein the calculated node value is proportional to the energy remaining amount and the RSSI value,

In the fourth step,
The drones designate the sensor having the highest calculated node value among the first sensors as the rendezvous point using the energy remaining amount and the RSSI value,

If the rendezvous point is not designated in the fourth step,
Between the fourth step and the fifth step,
And a fourth step of the drones designating a predetermined sensor among the plurality of sensors as the rendezvous point.
The method according to claim 1,
Prior to the first step,
Further comprising the step of entering the drone into a construction site area,
The plurality of sensors collect information related to the construction site,

If a plurality of rendezvous points are designated in the fourth step,
Before proceeding to the fifth step in the fourth step,
Further comprising a step 4-2 of repeating the first step to the fourth step. The rendezvous point replacement method for drones based data collection according to claim 1,
delete delete delete delete delete delete 3. The method of claim 2,
In the step 4-2,
Wherein the rendezvous point is repeatedly performed until the rendezvous point is designated as one rendezvous point.
The method according to claim 1,
After the seventh step,
And returning to the base station the dron that has received the collected information,
Wherein the drones, the plurality of sensors, and the base station communicate using at least one of near field communication and long distance communication. 11. The method of claim 10,
The local area communication includes Bluetooth, Radio Frequency Identification (RFID), infrared data association (IrDA), ultra-wideband (UWB), ZigBee, and Wi-Fi (Wireless Fidelity)
The long-distance communication may be performed by using code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), or single carrier frequency division multiple access Wherein the rendezvous point replacement method comprises the steps of: In the drones for replacing rendezvous points,
Broadcasts a first message announcing its location,
When a plurality of sensors collecting information related to the environment measure the energy remaining amount and RSSI (Received Signal Strength Indication) for the first message corresponding to the first message,
Receiving a second message including the energy remaining amount and the RSSI value from the plurality of sensors,
Designating one rendezvous point of the plurality of sensors using the energy remaining amount and the RSSI value,
A third message informing the fact that the rendezvous point is designated is transmitted to the designated rendezvous point,
When the rendezvous point collects information sensed by a sensor other than the rendezvous point among the plurality of sensors,
Receiving the collected information from the rendezvous point,
The drones designate the sensor having the highest node value calculated using the energy remaining amount and the RSSI value as the rendezvous point,
If the rendezvous point is not specified,
The drones,
Designating a predetermined sensor among the plurality of sensors as the rendezvous point,
When a plurality of rendezvous points are designated,
The drones,
Wherein the step of repeating the operation for designating the rendezvous point is performed.
13. The method of claim 12,
The dron enters the construction site area,
Wherein the plurality of sensors collect information related to the construction site. delete delete delete 13. The method of claim 12,
The drones,
And repeating the operation for designating the rendezvous point until the rendezvous point is designated as one rendezvous point.
13. The method of claim 12,
Upon receiving the collected information, the drones return to the base station,
Wherein the drones, the plurality of sensors, and the base station communicate using at least one of local and remote communication. 19. The method of claim 18,
The local area communication includes Bluetooth, Radio Frequency Identification (RFID), infrared data association (IrDA), ultra-wideband (UWB), ZigBee, and Wi-Fi (Wireless Fidelity)
The long-distance communication may be performed by using code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), or single carrier frequency division multiple access Characterized in that the dendrite for rendezvous point replacement. delete delete delete delete

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