KR102065888B1 - Communication method and apparatus in optical camera communication system - Google Patents

Abstract

Disclosed are a communication method of an optical camera communication system and an apparatus thereof. A transmission node of the communication system may include a processor, a memory in which one or more commands executed by the processor are stored, and a light emitting diode (LED) array including a plurality of LEDs blinking in accordance with the command executed by the processor. Accordingly, the performance of the communication system can be increased.

Description

TECHNICAL METHOD AND APPARATUS IN OPTICAL CAMERA COMMUNICATION SYSTEM}

The present invention relates to a communication method and apparatus of an optical camera communication system, and more particularly, to a communication method and apparatus of an optical camera communication system for modulating data using an orthogonal frequency division multiplexing modulation scheme.

With the development of information and communication technology, various wireless communication technologies are being developed. Visible light communication (VLC) may be performed using a light emitting diode (LED). Visible light communication technology has been standardized in Institute of Electrical and Electronics Engineers (IEEE) 802.15.7, and IEEE 802.15.7 defines technologies of the PHY (physical) layer and the medium access control (MAC) layer. In particular, IEEE 802.15.7 defines technologies for high-speed data transmission and reception in a line of sight (LoS) environment, and the technologies specified in IEEE 802.15.7 have a problem that is difficult to apply to an actual communication environment.

In accordance with the need for improvement of IEEE 802.15.7, standardization of IEEE 802.15.7m has proceeded. IEEE 802.15.7m defines Optical Wireless Communication (OWC) technology, which may include Light Fidelity (LiFi) technology, Optical Camera Communication (OCC) technology, and LED Identification (LED-ID) technology. .

A rolling shutter camera can be used as the camera of the optical camera communication system. The frame rate of such a rolling shutter camera is not a constant value but a variable value. As a result, when the pulse rate of the light emitting diode (LED) is constant, a change in the frame rate of the rolling shutter camera may cause data loss. For example, if the camera operates in a situation where a change in the frame rate is not expected, the camera may not capture an image. Therefore, data loss may occur.

An object of the present invention for solving the above problems is to provide a communication method and apparatus that can prevent the loss of transmitted data even if the frame rate of the rolling shutter camera in the optical camera communication system.

According to an embodiment of the present invention, a transmitting node includes a processor, a memory in which one or more instructions executed by the processor are stored, and a plurality of light emitting diodes (LEDs) blinking according to the instructions executed by the processor. And one or more instructions, wherein the one or more instructions modulate the data by orthogonal frequency division modulation to generate a data frame and based on the data frame. Is executed to transmit the data frame to a receiving node by blinking the LEDs included in the array, the data frame comprising a preset number of data subframes, each of the preset number of data subframes. Is the same sequence number and the same payload load).

Wherein the one or more commands may be further executed to receive a response message from the receiving node that includes information indicating that oversampling has occurred and to reduce the number of data subframes.

Here, the response message may further include information on a shooting period of the camera included in the receiving node, and the one or more commands may include the shooting period indicated by the response message as the transmission period of the data subframes. It may be further executed to set the number of the data subframes to a value greater than or equal to the divided value.

Wherein the one or more commands receive from the receiving node a response message containing information about the number of pixels per bit of any of the images taken by the camera included in the receiving node and the size of the LED array. And based on the number of pixels per bit, setting the size of the data subframe, wherein the data subframe size is less than or equal to the size of the LED array divided by the number of pixels indicated in the response message. Can be a value.

A receiving node according to another embodiment of the present invention is a processor. May include a memory that stores one or more instructions executed by the processor and images of flashing images of a LED array (Light Emitting Diode array) of a transmitting node according to a memory stored therein and instructions executed by the processor; Wherein the one or more instructions comprise a preset number of data subframes, each containing the same sequence number and the same payload, from the blinking images of the LED array. It is possible to obtain a plurality of data frames to compare the frame rate of the camera and the flashing speed of the LED array to determine whether oversampling occurs, and if the oversampling occurs, the data subframe Data subs containing different sequence numbers by comparing sequence numbers To obtain frame and and may be implemented to decode the data frame by merging sequence of the different sequence number of data sub-frame in the sequence number of the payload obtained, and the payload contained in the containing.

Here, the one or more commands may be further executed to transmit a response message including information indicating that the oversampling has occurred to the transmitting node when it is determined that the oversampling has occurred.

Here, the one or more commands, from the transmitting node receives a response message containing information indicating the size of the LED array included in the transmitting node, the pixel per bit of any of the images taken by the camera Detecting a number and setting the size of the data subframe based on the size of the LED array and the number of pixels per status bit, the size of the data subframe being the size of the LED array indicated in the response message. It may be less than or equal to a value divided by the number of pixels.

Here, the one or more instructions may be further executed to set the number of pixels proportional to the period of the reference clock of the processor and inversely proportional to the frame rate of the camera.

According to another embodiment of the present invention, a receiving node includes a processor, a memory in which one or more instructions executed by the processor are stored, and an LED array of the transmitting node according to the instructions executed by the processor. A camera for capturing images of a flashing state of a diode array, wherein the one or more instructions are from the images of the flashing state of the LED array, respectively, with the same sequence number and the same payload. Acquire a plurality of data frames including a preset number of data subframes, and compares the frame rate of the camera with the blinking speed of the LED array to determine whether under sampling occurs. And if the under sampling occurs, determine the sequence number of the data subframes. T by sending that includes detecting a missing data frame, and requested to retransmit the missing data frame information retransmission request message to the transmitting node, and can be implemented to decode the data frame obtained.

Here, the one or more instructions may be further executed to re-receive the missing data frame indicated in the retransmission request message from the transmitting node and to demodulate the data frame received from the transmitting node.

Here, the one or more instructions may be further executed to obtain data by merging a result of demodulating the obtained data frames with a result of demodulating the data frame re-received from the transmitting node.

Here, the one or more commands, from the transmitting node receives a response message containing information indicating the size of the LED array included in the transmitting node and the number of pixels per bit of any of the images taken by the camera And set the size of the data subframe based on the size of the LED array and the number of pixels per status bit, the size of the data subframe being the size of the LED array indicated in the response message. It may be less than or equal to a value divided by the number of pixels.

Here, the one or more instructions may be further executed to set the number of pixels proportional to the period of the reference clock of the processor and inversely proportional to the frame rate of the camera.

According to the present invention, since a data frame is composed of a plurality of data subframes having the same sequence number in a communication system, loss of data transmitted even if undersampling or oversampling occurs according to a change in the camera frame rate of a receiving node is achieved. Can be prevented.

1 is a conceptual diagram illustrating a first embodiment of a communication system.
2 is a block diagram showing a first embodiment of a communication node constituting a communication system.
3 is a block diagram illustrating a first embodiment of a transmission module included in a communication node in a communication system.
4 is a block diagram showing a first embodiment of a transmission processing unit included in a transmission module in a communication system.
5 is a conceptual diagram illustrating a first embodiment of a data frame in a communication system.
6 is a block diagram illustrating a first embodiment of a receiving module included in a receiving node in a communication system.
7 is a block diagram illustrating a first embodiment of a data obtaining unit included in a receiving module in a communication system.
8 is a flowchart illustrating a first embodiment of a method of transmitting and receiving data in a communication system.
9 is a conceptual diagram illustrating a first embodiment of decoding security in a communication system.
10 is a flowchart illustrating a second embodiment of a data transmission / reception method in a communication system.
11 is a conceptual diagram illustrating a first embodiment of a method of detecting a missing data frame in a communication system.

As the present invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

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

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. In the following description of the present invention, the same reference numerals are used for the same elements in the drawings and redundant descriptions of the same elements will be omitted.

A communication system to which embodiments according to the present invention are applied will be described. The communication system to which the embodiments according to the present invention are applied is not limited to the contents described below, and the embodiments according to the present invention may be applied to various communication systems. Here, the communication system may be used in the same sense as the communication network.

1 is a conceptual diagram illustrating a first embodiment of a communication system.

Referring to FIG. 1, a communication system may include a plurality of communication nodes 110 and 120. The plurality of communication nodes 110 and 120 may perform communication using communication schemes defined in Institute of Electrical and Electronics Engineers (IEEE) 802.15.7 (eg, IEEE 802.15.7m). For example, each of the plurality of communication nodes 110, 120 may include a light emitting diode (LED) and a camera, transmit signals by blinking the LED, and may be connected to a blinking state of the LED photographed by the camera. A signal can be obtained based on this. Each of the plurality of communication nodes 110 and 120 may be a sensor node, an Internet of Things (IoT) node, a smart phone, or the like. Each of the plurality of communication nodes 110 and 120 may have a structure as follows.

2 is a block diagram showing a first embodiment of a communication node constituting a communication system.

2, the communication node 200 may include a processor 210, a memory 220, a transmission module 230, and a reception module 240. In addition, the communication node 200 may further include a storage device 250 or the like. Each component included in the communication node 200 may be connected by a bus 260 to communicate with each other.

However, each component included in the communication node 200 may be connected through a separate interface or a separate bus around the processor 210 instead of the common bus 260. For example, the processor 210 may be connected to at least one of the memory 220, the transmission module 230, the reception module 240, and the storage device 250 through a dedicated interface.

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 250. The processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed. Each of the memory 220 and the storage device 250 may be configured as at least one of a volatile storage medium and a nonvolatile storage medium. For example, the memory 220 may be configured as at least one of a read only memory (ROM) and a random access memory (RAM).

The transmission module 230 may include an array of LEDs and may operate under the control of the processor 210. The receiving module 240 may include a camera and operate under the control of the processor 210. The transmission module 230 may be configured as follows.

3 is a block diagram illustrating a first embodiment of a transmission module included in a communication node in a communication system.

Referring to FIG. 3, the transmission module 300 may include a communication unit 310, a transmission processing unit 320, a dimming control unit 330, and an LED array 340. Herein, the transmission module 300 may be configured similarly or identically to the transmission module 230 of FIG. 2. The communication unit 310 may perform communication with the receiving module 600 (refer to FIG. 6). The communication unit 310 may transmit a response message (for example, a response message including information indicating the size of the LED array 340) to the receiving module 600, and the receiving module 600. A response message including specific information (for example, a response message including information on which oversampling has occurred in the receiving module 600) may be received. The transmission processor 320 may process an input signal by using orthogonal frequency division multiplexing (OFDM).

The transmission processor 320 may be configured as follows.

4 is a block diagram showing a first embodiment of a transmission processing unit included in a transmission module in a communication system.

Referring to FIG. 4, the transmission processor 400 may include a serial to parallel converter unit 410, a forward error correction encoder 420, an SN insertion unit 430, Quadrature Amplitude Modulation Unit (440), Mapping Unit (450), Inverse Fast Fourier Transform (IFFT) Unit 460, Cyclic Prefix Add Unit (470), and Parallel Series Converter (parallel series converter) unit, 480, and data frame generation unit 490. In embodiments, a unit may mean a means, an entity, an apparatus, or the like that performs a specific function.

The serial bit stream may be input to the serial / parallel conversion unit 410. The serial / parallel conversion unit 410 may convert the input serial bit streams into a parallel form. The serial / parallel conversion unit 410 may transmit the bit stream in parallel to the FEC encoder 420.

The FEC encoder 420 may receive a bit stream in parallel from the serial / parallel conversion unit 410. The FEC encoder 420 may add additional information for the FEC to each of the bit streams. Here, the "bit stream + additional information" may be a payload (for example, a data symbol). The FEC encoder 420 may send the payload to the SN insertion unit 430.

The SN insertion unit 430 may receive the payload from the FEC encoder 420. The SN insertion unit 430 may add a sequence number in front of the payload. Here, the "sequence number + payload" may be a data sub frame. The SN insertion unit 430 may transmit a data subframe to the QAM unit. The QAM unit 440 may receive a data subframe from the SN insertion unit 430. The QAM unit 440 may modulate the data subframe in a QAM manner. For example, the QAM unit 440 may modulate a data subframe in a 16-QAM or 64-QAM scheme. In the case of modulating a data subframe by the 16-QAM method, the payload may be quantized to 16 levels and mapped to 16 coordinates of the I / Q plot. When the data subframe is modulated by the 64-QAM method, the data subframe may be used. The frame can be quantized to 64 levels and mapped to 64 coordinates in the I / Q plot. The data subframe modulated by the QAM method may include a real part and an imaginary part according to the coordinates of the I / Q plot. The QAM unit 440 may transmit the data subframe modulated by the QAM method to the mapping unit 450.

The mapping unit 450 may receive a data subframe modulated in a QAM manner from the QAM unit 440. The mapping unit 440 may include, for example, a Hermitian matrix. Here, the Hertian matrix may be a matrix in which the main diagonal component is a real number, the remaining components are complex numbers, and components opposite to each other on a diagonal line are complex conjugated relations. When the mapping unit 450 includes the hermitian matrix, the mapping unit 460 may map to remove an imaginary part of the data subframe modulated by the QAM scheme. The mapping unit 450 may transmit the mapped data subframe to the IFFT unit 460.

The IFFT unit 460 may receive the mapped data subframe from the mapping unit 450. The IFFT unit 460 may convert a data subframe in the frequency domain into a data subframe in the time domain by using an inverse fast fourier transform (IFFT) method. In addition, the IFFT unit may convert a data subframe in the frequency domain into a data subframe in the time domain by using an inverse discrete fourier transform (IDFT) method. The IFFT unit 460 may transmit the data subframe of the time domain to the CP adding unit 470. The CP adding unit 470 may receive the data subframe in the time domain from the IFFT unit 460. The CP adding unit 470 may insert a cyclic prefix (CP) into a data subframe in the time domain. That is, the CP adding unit 470 may insert the CP in the data subframe of the time domain and transmit the CP to the parallel / serial conversion unit 480.

The parallel / serial conversion unit 480 may receive the data subframe in which the CP is inserted from the CP adding unit 470. The parallel / serial conversion unit 480 may convert data subframes in parallel form into data subframes in serial form. The parallel / serial conversion unit 480 may transmit the serial data subframe to the data frame generation unit 490. The data frame generation unit 490 may receive data subframes in serial form from the parallel / serial conversion unit 480. The data frame generation unit 490 merges the data subframes to generate a data frame. That is, the data frame generation unit 490 may generate a data frame by merging data subframes including the same sequence number and the same payload.

Meanwhile, the data frame generated by the transmission processor 400 may be as follows.

Referring to FIG. 5, a plurality of data frames may be generated at a communication node. The payloads (eg, data symbols DS) included in each of the plurality of data frames may be different from each other. One data frame may include a plurality of data subframes, and a plurality of data subframes belonging to one data frame may include the same payload (eg, a data symbol DS). In other words, in order to prevent transmission of data, the same payload may be repeatedly transmitted through the same data subframe. The data frame rate may be defined as the number of data frames including different payloads among data frames transmitted in a specific section. The data frame may be designed to support both an over sampling scheme and an under sampling scheme. The oversampling scheme may be a sampling scheme used when the frame rate of the camera (ie, the camera 610 shown in FIG. 6) is faster than the data frame rate. The under sampling method may be a sampling method used when the frame rate of the camera (ie, the camera 610 illustrated in FIG. 6) is slower than the data frame rate.

Referring back to FIG. 3, the dimming controller 330 may receive data frames from the transmission processor 320. The dimming controller 330 may blink the LED array 340 at a preset blinking speed based on the data frame. The dimming controller 330 may transmit a data frame to the receiving module 600 (see FIG. 6) by blinking the LED array 340.

Referring to FIG. 6, the receiving module 600 may include a camera 610, a comparator 620, a communicator 630, and a data acquirer 640. The receiving module 600 may be configured similarly or identically to the receiving module 240 of FIG. 2. The camera 610 may transmit information about the frame rate of the camera to the comparator 630. In addition, the camera 610 may capture images of the blinking state of the LED array 340 (see FIG. 3) included in the transmission module 300 (see FIG. 3). The camera 610 may transmit the photographed blinking images to the comparator 630 and the data acquirer 640.

The communication unit 620 may perform communication with the transmission module 300 (see FIG. 3). The communication unit 620 may transmit a response message (for example, a response message including information on which oversampling occurs to the transmission module 300) to the transmission module 300, and transmit the transmission module 300. Can receive a response message (eg, a response message including information indicating the size of the LED array 340 (see FIG. 3)) including specific information.

The comparator 630 may receive information about the frame rate of the camera 610 and images of the blinking state of the LED array 340 from the camera 610. The comparator 630 may obtain the blinking speed of the LED array 340 from the images of the blinking state of the LED array 340. The comparison unit 630 may compare the frame rate of the camera 610 with the flashing speed of the LED array 340 to determine whether oversampling or undersampling has occurred in the receiving module 600. When the comparator 630 determines that oversampling has occurred in the receiving module 600, the comparator 630 may transmit information indicating that oversampling has occurred to the data acquirer 640. In addition, the comparator 630 may generate a response message including information indicating that oversampling has occurred in the receiving module 600. The comparator 630 may transmit a response message including information indicating that oversampling has occurred to the transmitting module 300 through the communication unit 620. In addition, when the comparison unit 630 determines that under sampling has occurred in the receiving module 600, the comparison unit 630 may transmit information indicating that the under sampling has occurred to the data acquisition unit 640. The comparator 630 may generate a retransmission message for requesting retransmission of the missing data frame when the data frame is missing due to under sampling. The comparison unit 630 may transmit the retransmission message to the transmission module 300 through the communication unit 620.

The data acquirer 640 may receive images photographing a blinking state of the LED array 340 from the camera 610. The data acquirer 640 may acquire data by processing an image photographing a blinking state of the LED array 340. The data acquirer 640 may receive information indicating that oversampling or undersampling has occurred in the receiving module 600 from the comparator 630. In addition, when the data acquiring unit 640 receives the information that the undersampling has occurred, the data acquiring unit 640 may detect a missing data frame and transmit information about the missing data frame to the comparator 630.

The data acquisition unit 640 may be configured as follows.

7 is a block diagram illustrating a first embodiment of a data obtaining unit included in a receiving module in a communication system.

Referring to FIG. 7, the data acquisition unit 700 includes an image processing unit 710, a serial to parallel converter unit 720, a CP removing unit 730, and an FFT Fast Fourier Transform unit 740, demapping unit 750, Sequence Number extracting unit 760, error detection unit 770, parallel series converter unit 780 and decoding Unit 790 may be included.

The image processing unit 710 may receive images in a blinking state from the camera 610 (see FIG. 6). The image processing unit 710 may process the images received from the camera to obtain bit streams in serial form. The image processing unit 710 may transmit the bit streams in serial form to the serial / parallel conversion unit 720.

Serial / parallel conversion unit 720 may receive bit streams in serial form from image processing unit 710. The serial / parallel conversion unit 720 may convert the bit streams into bit streams in parallel.

The serial / parallel conversion unit 720 may transmit the bit streams in parallel to the CP removal unit 730. The CP removal unit 730 may receive the bit streams in parallel from the serial / parallel conversion unit 720. The CP removal unit 730 may remove the CP inserted in the respective bit streams. The CP removal unit 730 may transmit the bit streams from which the CP has been removed to the FFT unit 740. The FFT unit 740 may convert bit streams from which CP is removed from bit streams in the time domain to bit streams in the frequency domain by using a fast fourier transform (FFT) scheme. The FFT unit 740 may transmit the bit streams transformed into the frequency domain to the demapping unit 750. The demapping unit 750 can receive the bit streams transformed into the frequency domain from the FFT unit 740. The demapping unit 750 may perform a demapping operation on the bit streams converted into the frequency domain. The demapping unit 750 can send each destreamed bit stream to the SN extraction unit 760. SN extraction unit 760 may receive demapped bit streams from demapping unit 750. The SN extraction unit 760 may obtain sequence numbers included in the demapped bit streams. The SN extraction unit 760 may also compare the obtained sequence numbers. That is, when receiving information indicating that undersampling has occurred in the receiving module 600 (refer to FIG. 6) from the comparator 630, the SN extracting unit 760 compares the sequence numbers to detect which data frame is missing. Can be. The SN extraction unit 760 may send the bit streams to the error detection unit 770. Here, each of the bit streams may be bit streams from which a sequence number is extracted.

The error detection unit 770 may receive the bit streams from which the sequence number has been extracted from the SN extraction unit 760. The error detection unit 770 may detect whether an error has occurred in the bit streams. When an error occurs in the bit streams, the error detection unit 770 may transmit a message requesting retransmission of the data frames through the communication unit 620 (see FIG. 6). If no error occurs in the bit streams, the error detection unit 770 may send the bit streams to the parallel / serial conversion unit.

The parallel / serial conversion unit 780 can receive the bit streams from the error detection unit 770. The parallel / serial conversion unit 780 may convert the bit streams in parallel form into a serial form. The parallel / serial conversion unit 780 can send the serial bit streams to the decoding unit 790.

The decoding unit 790 can receive the bit streams in serial form from the parallel / serial conversion unit 780. When receiving information indicating that oversampling has occurred in the receiving module 600 from the decoding unit 790 comparator 630, comparing the sequence numbers obtained by the SN extraction unit 760 to include different sequence numbers. Bit streams may be obtained one by one. The decoding unit 790 can obtain the payload from each of the bit streams containing different sequence numbers. The decoding unit 790 may merge the obtained payloads and may decode the merged payloads to obtain first data.

When the decoding unit 790 receives the information that the undersampling has occurred in the receiving module 600 from the comparator 630, the decoding unit 790 may first demodulate the received bit streams to obtain data. The decoding unit 790 may detect the missing data frame by comparing the sequence numbers of the bitstreams extracted by the SN extraction unit 760. Thereafter, the decoding unit 790 may re-receive the bit stream included in the missing data frame from the transmitting module 300 (see FIG. 3). The decoding unit may obtain the payload from the re-received bit stream and decode the obtained payload to obtain second data. The decoding unit 790 may then merge the first data and the second data to obtain data.

Next, methods of transmitting and receiving data in a communication system will be described. Even when the method (for example, the transmission or reception of a signal) is performed among the communication nodes is described, the corresponding second communication node corresponds to the method (for example, the method performed in the first communication node). For example, the reception or transmission of a signal) may be performed. That is, when the operation of the terminal is described, the base station corresponding thereto may perform an operation corresponding to the operation of the terminal. In contrast, when the operation of the base station is described, the terminal corresponding thereto may perform an operation corresponding to the operation of the base station.

8 is a flowchart illustrating a first embodiment of a method of transmitting and receiving data in a communication system.

Referring to FIG. 8, a communication system may include a transmitting node and a receiving node. The transmitting node may be the transmitting node 110 of FIG. 1, and the receiving node may be the receiving node 120 of FIG. 1. Each of the transmitting node and the receiving node may be configured identically or similarly to the communication node 200 shown in FIG. 2. The transmitting module included in each of the transmitting node and the receiving node may be configured identically or similarly to the embodiments shown in FIGS. 3 and 4. The receiving module included in each of the transmitting node and the receiving node may be configured identically or similarly to the embodiments shown in FIGS. 6 and 7.

The transmitting node may generate data frames (S810). The data frames may be generated by the transmission processor (for example, the transmission processor 320 of FIG. 3), and may be configured identically or similarly to the data frame illustrated in FIG. 5. The transmitting node may transmit the generated data frames to the receiving node (S820). In this case, the LED array (for example, the LED array 340 shown in FIG. 3) blinks to transmit a data frame to the receiving node.

The receiving node may receive data frames from the transmitting node. That is, the receiving node may acquire images by capturing the blinking state of the LED array using a camera (for example, the camera 610 illustrated in FIG. 6), and may acquire data frames from the images. In addition, the comparator of the receiving node (for example, the comparator 620 of FIG. 6) may obtain the blinking speed of the LED array from the images and may obtain the data frame rate of the transmitting node through the blinking speed.

The receiving node may compare the data frame rate with the camera frame rate (S830). The comparator of the receiving node may compare the speed of the data frame with the speed of the camera frame, thereby determining whether oversampling has occurred in the receiving node. The comparing unit of the receiving node may determine that oversampling has occurred in the receiving node when the camera frame rate exceeds the data frame rate. The comparison unit of the receiving node may generate a response message including information indicating that oversampling has occurred, and indicates that oversampling has occurred in the transmitting node through a communication unit (for example, communication unit 620 of FIG. 6) of the receiving node. The response message including the information may be transmitted (S840). The response message may further include information about the frame rate of the camera included in the receiving node and information about the number of pixels per bit of any image among the images photographed by the camera.

The transmitting node may receive a response message from the receiving node. That is, the transmitting node may determine that any of the images taken by the camera, the information on the frame rate of the camera, and the images captured by the camera are oversampled through the communication unit of the transmitting node (for example, the communication unit 310 of FIG. 3). A response message including information about the number of pixels per bit may be received.

The transmitting node may obtain information indicating that oversampling has occurred in the receiving node through the received response message. The transmitting node may adjust the number and size of data subframes included in each data frame based on the information included in the response message (S850).

The transmitting node may set the number of data subframes based on the frame rate of the camera indicated by the response message and the transmission period of the data subframes. When oversampling occurs in the receiving node, the transmitting node may reduce the number of data subframes included in the data frames, respectively. Herein, the number of data subframes may be represented by Equation 1 below.

은 데이터 서브 프레임들의 개수일 수 있고,

는 카메라의 프레임 레이트일 수 있으며,

은 데이터 서브 프레임들의 전송 주기일 수 있다.From here

May be the number of data subframes,

May be the frame rate of the camera,

May be a transmission period of the data subframes.

The transmitting node may also set the size of the data subframes. Herein, the size of the data subframes may be represented by Equation 2 below.

는 데이터 서브 프레임들의 크기일 수 있고,

는 LED 어레이의 크기일 수 있으며,

는 이미지의 비트당 픽셀 수일 수 있다. 한편 이미지의 비트 당 픽셀 수는 다음의 수학식 3에 의할 수 있다.From here,

May be the size of the data subframes,

Can be the size of the LED array,

May be the number of pixels per bit of the image. On the other hand, the number of pixels per bit of the image can be expressed by the following equation (3).

는 이미지의 비트당 픽셀 수일 수 있고,

는 수신 노드의 클록 주기일 수 있고,

는 카메라의 촬영 주기일 수 있다. 송신 노드는 데이터 프레임들을 수신 노드에 전송할 수 있다(S860). 여기에서 데이터 프레임들은 개수와 크기가 조절된 데이터 서브 프레임들을 포함할 수 있다. 수신 노드는 송신 노드로부터 데이터 프레임들을 수신할 수 있다. 수신 노드는 송신 노드로부터 수신한 데이터 프레임들로부터 데이터를 추출할 수 있다(S870). 즉, 수신 노드의 데이터 추출부(예를 들어, 도 6의 데이터 추출부(640)는 데이터 서브 프레임들에 포함된 시퀀스 넘버를 비교하여 데이터를 복호할 수 있다. From here,

Can be the number of pixels per bit of the image,

May be the clock period of the receiving node,

May be a shooting cycle of the camera. The transmitting node may transmit data frames to the receiving node (S860). Herein, the data frames may include data subframes whose number and size are adjusted. The receiving node may receive data frames from the transmitting node. The receiving node may extract data from the data frames received from the transmitting node (S870). That is, the data extracting unit (eg, the data extracting unit 640 of FIG. 6) of the receiving node may decode the data by comparing the sequence numbers included in the data subframes.

When oversampling occurs in the receiving node, a method of acquiring data by the receiving node may be as follows.

9 is a conceptual diagram illustrating a first embodiment of a data acquisition method in a communication system.

Referring to FIG. 9, the communication system may include a plurality of data subframes 910, 920, 930, 940, and 950. In this case, the plurality of data subframes 910, 920, 930, 940, and 950 may be similar to or the same as the data subframe illustrated in FIG. 5. The plurality of data subframes 910, 920, 930, 940, and 950 may include sequence numbers 911, 921, 931, 941, and 951 and payloads 912, 922, 932, 942, and 952, respectively. have. Here, the first data subframe 910 and the second data subframe 920 may include the same sequence numbers 911 and 921 and the same payloads 912 and 922, and may include the same data frame (eg, Data frame i-1). The third data subframe 930 and the fourth data subframe 940 may include the same sequence number 931. 941 and the same payload 932, 942, and may include the same data frame (eg, a data frame). (i)).

The data extracting unit of the receiving node (for example, the data extracting unit 640 of FIG. 6) includes the sequence numbers 911, 921, and 931 included in the plurality of data subframes 910, 920, 930, 940, and 950. , 941, 951). The data extractor may acquire a payload included in any one of data subframes including the same sequence number. For example, the payload 912 included in the first data subframe 910 among the first data subframe 910 and the second data subframe 920 may be obtained, and the third data subframe ( 930 and the payload 912 included in the third data subframe 930 among the fourth data subframe 940 may be obtained, and the payload 952 included in the fifth data subframe 950. Can be obtained. The data extractor may merge the obtained payloads 912, 932, and 952 in order. The data extractor may acquire data by decoding the merged payload.

10 is a flowchart illustrating a second embodiment of a method of transmitting and receiving data in a communication system.

Referring to FIG. 10, a communication system may include a transmitting node and a receiving node. The transmitting node may be the transmitting node 110 of FIG. 1, and the receiving node may be the receiving node 120 of FIG. 1. Each of the transmitting node and the receiving node may be configured identically or similarly to the communication node 200 shown in FIG. 2. The transmitting module included in each of the transmitting node and the receiving node may be configured identically or similarly to the embodiments shown in FIGS. 3 and 4. The receiving module included in each of the transmitting node and the receiving node may be configured identically or similarly to the embodiments shown in FIGS. 6 and 7.

The transmitting node may generate data frames (S1010). The data frames may be generated by the transmission processor (for example, the transmission processor 320 of FIG. 3), and may be configured identically or similarly to the data frame illustrated in FIG. 5. The transmitting node may transmit the generated data frames to the receiving node (S1020). In this case, the LED array (for example, the LED array 340 shown in FIG. 3) is blinking so that the data frame can be transmitted to the receiving node.

The receiving node may receive data frames from the transmitting node. That is, the receiving node may acquire images by capturing the blinking state of the LED array using a camera (for example, the camera 610 illustrated in FIG. 6) and obtain data frames from the images. In addition, the comparator of the receiving node (for example, the comparator 620 of FIG. 6) may obtain the blinking speed of the LED array from the images and may obtain the data frame rate of the transmitting node through the blinking speed.

The receiving node may compare the data frame rate with the camera frame rate (S1030). The comparator of the receiving node may compare the speed of the data frame and the speed of the camera frame, thereby determining whether under sampling has occurred in the receiving node. The comparator of the receiving node may determine that undersampling has occurred in the receiving node when the camera frame rate is less than the data frame rate. The data acquirer of the receiving node (for example, the data acquirer 640 of FIG. 6) may detect the missing data frame due to undersampling.

11 is a conceptual diagram illustrating a first embodiment of a method of detecting a missing data frame in a communication system.

Referring to FIG. 11, the communication system may include a plurality of data frames 1110, 1120, and 1130. The plurality of data frames may be similar or identical to the data frame shown in FIG. 5. Each of the plurality of data frames 1110, 1120, and 1130 may include a plurality of data subframes 1111, 1112, 1121, 1122, 1131, and 1132, and each of the data subframes 1111, 1112, 1121. , 1122, 1131, and 1132 may include a plurality of sequence numbers and payloads. Here, the sequence number and payload of the data subframes included in the same data frame may be the same. For example, the data subframes 1111 and 1112 included in the first data frame 1110 may include the same sequence numbers 1111-1 and 1111-3 and the same payload 1111-2. 1111-4).

The data acquirer of the receiving node (for example, the data acquirer 640 of FIG. 6) may acquire a sequence number included in the data subframe, and detect the missing data frame by comparing the sequence numbers. . For example, when the data acquirer acquires the sequence numbers n-1 1111-1 and n + 1 1131-1, it may be determined that the second data frame 1120 having the sequence number n is missing. have.

Referring back to FIG. 10, the data acquisition unit of the receiving node may acquire first data by decoding the data frames obtained in operation S1020 (S1050).

In addition, the data acquisition unit of the receiving node may transmit a response message including information on the missing data frame to the transmitting node (S1060). The data acquisition unit of the receiving node may transmit a response message to the transmitting node through the communication unit 620 of the receiving node. The transmitting node may receive a response message including information on the missing data frame from the receiving node, and may retransmit the missing data frame indicated by the response message to the receiving node (S1070). That is, the transmitting node may transmit the missing data frame to the receiving node by blinking the LED array included in the transmitting node (for example, the LED array 340 of FIG. 3).

The receiving node may re-receive missing data frames from the transmitting node. The receiving node can capture the blinking state of the LED array with the camera and receive the missing data frame again. The receiving node may obtain second data by decoding the data frame obtained in step S1060.

The receiving node may acquire data by merging the first data and the second data.

example The methods according to the invention can be implemented in the form of program instructions that can be executed by various computer means and recorded on a computer readable medium. Computer-readable media may include, alone or in combination with the program instructions, data files, data structures, and the like. The program instructions recorded on the computer readable medium may be those specially designed and constructed for the present invention, or may be known and available to those skilled in computer software.

Examples of computer readable media include hardware devices that are specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code, such as produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

Although described with reference to the above embodiments, those skilled in the art will understand that various modifications and changes can be made without departing from the spirit and scope of the invention as set forth in the claims below. Could be.

Claims (13)

As the sending node of the communication system
A processor;
A memory in which one or more instructions executed by the processor are stored; And
An LED array including a plurality of light emitting diodes (LEDs) blinking according to a command executed by the processor,
The one or more instructions,
Data is modulated by orthogonal frequency division modulation to include a predetermined number of data subframes, each of the predetermined number of data subframes having the same sequence number. Generate a data frame comprising a payload equal to;
Transmit the data frame to a receiving node by blinking LEDs included in the LED array based on the data frame; And,
And when receiving a response message from the receiving node that includes information indicating that oversampling has occurred, the transmitting node executed to reduce the number of data subframes. delete The method according to claim 1,
The response message further includes information on a shooting cycle of the camera included in the receiving node,
The one or more instructions,
And setting the number of the data subframes to a value greater than or equal to a value obtained by dividing the photographing period indicated by the response message by the transmission period of the data subframes. The method according to claim 1,
The one or more instructions,
Receive a response message from the receiving node, the response message including information on the number of pixels per bit of any of the images photographed by the camera included in the receiving node; And
Further to set the size of the data subframe based on the size of the LED array and the number of pixels per bit,
And the size of the data subframe is less than or equal to the size of the LED array divided by the number of pixels per bit indicated in the response message. As a receiving node of an optical camera communication system,
A processor;
A memory in which one or more instructions executed by the processor are stored; And
A camera for capturing images of a blinking state of an LED array (Light Emitting Diode array) of a transmitting node in accordance with a command executed by the processor;
The one or more instructions,
A plurality of data frames including a preset number of data subframes each having the same sequence number and the same payload from the flashing images of the LED array; obtain frames);
Comparing the frame rate of the camera with the blinking rate of the LED array to determine whether oversampling has occurred;
When the oversampling occurs, comparing the sequence numbers of the data subframes to obtain data subframes having different sequence numbers;
Send a response message to the transmitting node containing information that the oversampling has occurred; And,
And receiving payloads included in data subframes including the different sequence numbers, merging the payloads in the order of the sequence numbers, and decoding the data frames. delete The method according to claim 5,
The one or more instructions,
Receive a response message from the transmitting node, the response message including information indicating the size of the LED array included in the transmitting node;
Detect the number of pixels per bit of any of the images taken by the camera; And,
Based on the size of the LED array and the number of pixels per bit, to set the size of the data subframe,
And the size of the data subframe is less than or equal to the size of the LED array indicated by the response message divided by the number of pixels per bit. The method according to claim 7,
The one or more instructions,
And further configured to set the pixel number proportional to the period of the reference clock of the processor and inversely proportional to the frame rate of the camera. As a receiving node of an optical camera communication system,
A processor;
A memory in which one or more instructions executed by the processor are stored; And
A camera for capturing images of a blinking state of an LED array (Light Emitting Diode array) of a transmitting node in accordance with a command executed by the processor;
The one or more instructions,
A plurality of data frames including a preset number of data subframes each having the same sequence number and the same payload from the flashing images of the LED array; obtain frames);
Receive a response message from the transmitting node, the response message including information indicating the size of the LED array included in the transmitting node;
Detect the number of pixels per bit of any of the images taken by the camera;
Set the size of the data subframe based on the size of the LED array and the number of pixels per bit;
Comparing the frame rate of the camera with the blinking rate of the LED array to determine whether under sampling occurs;
When the undersampling occurs, comparing the sequence numbers of the data subframes to detect missing data frames;
Send a retransmission request message containing information requesting to retransmit the missing data frame to the transmitting node;
Executed to decode the obtained data frames; And,
And the size of the data subframe is less than or equal to the size of the LED array indicated by the response message divided by the number of pixels per bit. delete delete delete The method according to claim 9,
The one or more instructions,
And further configured to set the pixel number proportional to the period of the reference clock of the processor and inversely proportional to the frame rate of the camera.

Images