CN108900249B - Dimming device in visible light communication system and dimming control method thereof - Google Patents

Dimming device in visible light communication system and dimming control method thereof Download PDF

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CN108900249B
CN108900249B CN201811064352.8A CN201811064352A CN108900249B CN 108900249 B CN108900249 B CN 108900249B CN 201811064352 A CN201811064352 A CN 201811064352A CN 108900249 B CN108900249 B CN 108900249B
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dimming
block
check
crc
coding
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CN108900249A (en
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邓克岩
万毅
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Northwest Minzu University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
    • H04B10/114—Indoor or close-range type systems
    • H04B10/116—Visible light communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0041—Arrangements at the transmitter end
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0045—Arrangements at the receiver end
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0056—Systems characterized by the type of code used
    • H04L1/0061—Error detection codes

Abstract

A dimming device in a visible light communication system is composed of a transmitter and a receiver, wherein the transmitter comprises: the system comprises an FEC encoder, a CRC encoder, a dimming encoder, an OOK modulator and a light emitting diode LED; the receiver includes: a photoelectric detector, an OOK demodulator, a dimming decoder, a CRC detector and an FEC decoder. In the process of realizing dimming, each check block is firstly divided into a plurality of check blocks with the length ofMThen each length is set to be the dimming valueMThe check sub-block is light-adjusting coded to have the length ofNThe dimming sub-block of (1), wherein,Nmust satisfy
Figure 100004_DEST_PATH_IMAGE002
. The invention combines FEC channel coding and dimming control, so that the VLC system can realize reliable communication on one hand, and can realize dimming control of the LED on the other hand, thereby meeting the use requirement of actual illumination.

Description

Dimming device in visible light communication system and dimming control method thereof
Technical Field
The invention relates to a dimming device in a visible light communication system and a dimming control method thereof, belonging to the related technical fields of the visible light communication system, dimming control, data coding and decoding and the like.
Background
With the rapid development of wireless communication technology and the continuous upgrading and upgrading of mobile communication networks, radio spectrum is becoming an increasingly scarce resource. In this background, Optical Wireless Communication (OWC) has emerged as an important means for solving the problem. With the rapid advancement and widespread use of LED technology in recent years, a Visible Light Communication (VLC) system that realizes Communication by means of LEDs has become a main implementation means of optical wireless Communication. Because the VLC system adopts visible light as a carrier wave for information transmission, the VLC system has the advantages that other communication modes do not have, such as huge bandwidth, low cost, low power consumption, high safety, no electromagnetic interference, no use permission of frequency spectrum and the like.
In VLC systems, LEDs are required to implement not only lighting functions but also communication functions. Therefore, in the VLC system, on the premise of realizing reliable communication, a function of controlling the illumination brightness of the LED, that is, dimming control is also realized. In general, FEC coding techniques are used to improve the reliability of information transmission, but the ratio of "1" code to "0" code in the information data may vary to cause the bright and dark flicker phenomenon. Therefore, dimming control technology must be adopted to make the brightness of the LED meet the actual lighting requirement, i.e. meet the set lighting brightness and dimming value. Dimming control in VLC systems is a challenging technique.
Dimming control is usually implemented by changing the ratio of "1" code and "0" code in the information data by inserting Compensation Symbol (CS) (all "1" code or all "0" code). However, since a large number of compensation symbols need to be inserted to achieve the set dimming value (especially, the dimming value is large or small), the dimming control method causes a great reduction in the transmission efficiency of the VLC system. Therefore, how to implement a dimming control scheme for effective dimming is very important on the premise of implementing reliable communication.
Disclosure of Invention
The invention provides a dimming device in a visible light communication system and a dimming control method thereof, which greatly reduce the average number of additional compensation symbols inserted due to dimming control and improve the efficiency of information data transmission in a VLC system.
The technical scheme adopted by the invention is as follows:
a dimming device in a visible light communication system, the dimming device comprising a transmitter and a receiver, wherein:
the transmitter includes: the system comprises an FEC encoder, a CRC encoder, a dimming encoder, an OOK modulator and a light emitting diode LED;
the receiver includes: a photoelectric detector, an OOK demodulator, a dimming decoder, a CRC detector and an FEC decoder.
The specific functions of each part are as follows:
and the FEC encoder: channel coding of information data is realized;
the CRC encoder: CRC coding of the FEC coding block is realized, so that a receiving end can judge whether the received FEC coding block is correct or not;
dimming encoder: dimming coding is carried out on the CRC check block, so that the ratio of the code 1 and the code 0 in the information sent to the LED accords with a set dimming value, and the phenomenon of bright and dark flicker is avoided;
OOK modulator: the modulation of the information after dimming is realized;
a Light Emitting Diode (LED): converting the electrical signal into an optical signal suitable for transmission over an optical wireless channel;
a photoelectric detector: converting an optical signal received from an optical wireless channel into an electrical signal;
OOK demodulator: the demodulation of the received electric signal is realized;
dimming decoder: removing the dimming code of the sending end, and recovering to obtain a CRC (cyclic redundancy check) block;
and a CRC decoder: performing CRC on the received check block, and detecting whether the received check block is correct;
an FEC decoder: and decoding the FEC coding block which is received correctly, and recovering to obtain data information.
A dimming control method of a dimming device in a visible light communication system realizes dimming control in the visible light communication system through dimming codes of a check block to be sent; the method comprises the following specific steps:
the method comprises the following steps: a transmitter of the visible light communication system carries out block processing on information data to be transmitted, wherein the information data to be transmitted is processed by less than one block; sending each data block to a FEC (Forward Error correction) encoder one by one;
step two: for each data block, an FEC encoder encodes according to the adopted channel coding scheme to generate a coding block; sending each code block to a CRC (cyclic Redundancy check) encoder one by one;
step three: performing CRC encoding on each encoding block to generate a check block; sending each check block to a dimming encoder one by one;
step four: for each check block, the dimming encoder blocks according to a certain length; thereby dividing each check block into a plurality of check sub-blocks; for each check sub-block, dimming coding is carried out, the dimming sub-blocks meeting the dimming requirement are obtained through coding, and finally the dimming blocks meeting the dimming requirement are formed;
step five: modulating a dimming block output by a dimming encoder in an On-off (OOK) mode, and sending a modulated electric signal to an LED;
step six: the LED performs photoelectric conversion, converts the electric signal into an optical signal and sends the optical signal into a wireless optical channel for transmission;
step seven: after a receiver of the visible light communication system receives an optical signal, a Photoelectric Detector (PD) converts the received optical signal into an OOK modulated electrical signal;
step eight: the OOK modulated electric signal obtained by conversion is sent to an OOK demodulator for demodulation, and a dimming block is obtained;
step nine: the dimming block is sent to a dimming decoder for decoding to obtain a check block; sending the check block to a CRC detector;
step ten: the CRC detector performs CRC detection on each check block and judges whether the received check block is correct or not; the incorrect check block is deleted, and only the coding block in the check block detected by the CRC is sent to the FEC decoder;
step eleven: and the FEC decoder decodes according to the decoding rule to recover the data block.
In the fourth step, each check block is divided into a plurality of check blocks with the length ofMThe syndrome block of (1); to obtain a dimming value, each length is set toMThe check sub-block is light-adjusting coded to have the length ofNThe dimming sub-block of (1), wherein,Nmust satisfy
Figure DEST_PATH_IMAGE001
。
Compared with the prior art, the invention has the following beneficial effects:
compared with the scheme of inserting the compensation symbol to realize dimming control, the dimming control scheme in the VLC system provided by the patent is a new dimming control scheme. Because the dimming scheme combines FEC channel coding and dimming control at the same time, reliable communication can be realized on one hand, and dimming control of LEDs can be realized on the other hand, so that the use requirement of actual illumination is met, and meanwhile, due to the adoption of the dimming coding, the average number of additional compensation symbols inserted for dimming is greatly reduced, so that the transmission efficiency of information data in the VLC system is greatly improved.
Drawings
FIG. 1 is a block diagram of the VLC system of the present invention;
FIG. 2 illustrates a conventional dimming control method;
FIG. 3 is a schematic diagram illustrating the principle of dimming control of the dimming encoder of the present invention;
FIG. 4 is a schematic diagram of a dimming encoding of the dimming encoder of the present invention;
fig. 5 is a performance simulation diagram of a conventional dimming control method and a dimming control method according to the present invention.
Detailed description of the invention
In order that the content of the invention will be clearly understood, the invention will now be described in further detail with reference to specific examples, which are given in conjunction with the accompanying drawings.
In a visible Light communication system, Light-emitting Diodes (LEDs) are used to implement an illumination function on one hand and a communication function on the other hand. In a visible light communication system, dimming is to change the brightness of the LED so that the brightness of the LED conforms to the actually set brightness value. However, after the information data is subjected to channel coding, the duty ratio of the "1" code and the "0" code changes, so that the light and shade flicker phenomenon of the LED occurs. Dimming control is therefore required.
A dimming device in a visible light communication system is composed of a transmitter and a receiver, as shown in figure 1. Wherein:
the transmitter includes: the system comprises an FEC encoder, a CRC encoder, a dimming encoder, an OOK modulator and a light emitting diode LED;
the receiver includes: a photoelectric detector, an OOK demodulator, a dimming decoder, a CRC detector and an FEC decoder.
The specific functions of each part are as follows:
and the FEC encoder: channel coding of information data can be realized by adopting FEC coding modes such as LT codes;
the CRC encoder: CRC coding of the FEC coding block is realized, so that a receiving end can judge whether the received FEC coding block is correct or not;
dimming encoder: dimming coding is carried out on the CRC check block, so that the ratio of the code 1 and the code 0 in the information sent to the LED accords with a set dimming value, and the phenomenon of bright and dark flicker is avoided;
OOK modulator: the modulation of the information after dimming is realized;
LED: converting the electrical signal into an optical signal suitable for transmission over an optical wireless channel;
a photoelectric detector: converting an optical signal received from an optical wireless channel into an electrical signal;
OOK demodulator: the demodulation of the received electric signal is realized;
dimming decoder: removing the dimming code of the sending end, and recovering to obtain a CRC (cyclic redundancy check) block;
and a CRC decoder: performing CRC on the received check block, and detecting whether the received FEC coding block is correctly received;
an FEC decoder: and decoding the FEC coding block which is received correctly, and recovering to obtain data information.
Based on a dimming device in a visible light communication system, the dimming control method of the dimming device in the visible light communication system provided by the invention realizes dimming control in the visible light communication system through dimming codes of a check block to be sent; the method comprises the following specific steps:
the method comprises the following steps: a transmitter of the visible light communication system carries out block processing on information data to be transmitted, wherein the information data to be transmitted is processed by less than one block; sending each data block to a FEC (Forward Error correction) encoder one by one;
step two: for each data block, an FEC encoder encodes according to the adopted channel coding scheme to generate a coding block; sending each code block to a CRC (cyclic Redundancy check) encoder one by one;
step three: performing CRC encoding on each encoding block to generate a check block; sending each check block to a dimming encoder one by one;
step four: for each check block, the dimming encoder blocks according to a certain length; thereby dividing each check block into a plurality of check sub-blocks; for each check sub-block, dimming coding is carried out, the dimming sub-blocks meeting the dimming requirement are obtained through coding, and finally the dimming blocks meeting the dimming requirement are formed;
step five: modulating a dimming block output by a dimming encoder in an On-off (OOK) mode, and sending a modulated electric signal to an LED;
step six: the LED performs photoelectric conversion, converts the electric signal into an optical signal and sends the optical signal into a wireless optical channel for transmission;
step seven: after a receiver of the visible light communication system receives an optical signal, a Photoelectric Detector (PD) converts the received optical signal into an OOK modulated electrical signal;
step eight: the OOK modulated electric signal obtained by conversion is sent to an OOK demodulator for demodulation, and a dimming block is obtained;
step nine: the dimming block is sent to a dimming decoder for decoding to obtain a check block; sending the check block to a CRC detector;
step ten: the CRC detector performs CRC detection on each check block and judges whether the received check block is correct or not; the incorrect check block is deleted, and only the coding block in the check block detected by the CRC is sent to the FEC decoder;
step eleven: and the FEC decoder decodes according to the decoding rule to recover the data block.
The dimming control principle of the dimming encoder is shown in fig. 3 and 4. In FIG. 3, each parity block is divided into a number of parity blocks of lengthMThe syndrome block of (1); in fig. 4, to obtain the dimming values, each length is set to beMThe check sub-block is light-adjusting coded to have the length ofNThe dimming sub-block of (1), wherein,Nmust satisfy
Figure RE-371075DEST_PATH_IMAGE002
. After the dimming coding, the ratio of the 1 code and the 0 code in the dimming block accords with the set dimming value, and the aim of dimming control is fulfilled.
For example, if the check block length is 408, takeMCondition of = 8:
(1) number of inserted compensation symbols
The conventional dimming control scheme (as shown in fig. 2) and the dimming control scheme proposed by the present invention require the number of inserted compensation symbols under different dimming values as shown in fig. 5.
(2) Average number of inserted compensation symbols
For the dimming value interval, the average number of compensation symbols inserted by the conventional dimming control scheme is 1489.888, and the average number of compensation symbols inserted by the dimming control scheme provided by the present invention is 622.722.
It can be seen from the above experimental data that the dimming control scheme provided by the present invention can reduce the average number of compensation symbols inserted due to dimming control to a great extent, thereby greatly improving and improving the transmission efficiency of the VLC system and reducing the transmission delay of the VLC system.

Claims (2)

1. A dimming device in a visible light communication system, comprising: the dimming device consists of a transmitter and a receiver, wherein:
the transmitter includes: the system comprises an FEC encoder, a CRC encoder, a dimming encoder, an OOK modulator and a light emitting diode LED;
the receiver includes: the system comprises a photoelectric detector, an OOK demodulator, a dimming decoder, a CRC detector and an FEC decoder;
the specific functions of each part are as follows:
and the FEC encoder: channel coding of information data is realized;
the CRC encoder: CRC coding of the FEC coding block is realized, so that a receiving end can judge whether the received FEC coding block is correct or not;
dimming encoder: dimming and coding CRC check blocks, and dividing each check block into a plurality of check blocksCheck sub-blocks of length M; in order to obtain a dimming value, dimming coding is carried out on each check sub-block with the length of M into a dimming sub-block with the length of N, wherein the value of N must satisfy the requirement
Figure DEST_PATH_IMAGE002
(ii) a The ratio of the code 1 and the code 0 in the information sent to the LED accords with the set dimming value, and the phenomenon of light and shade flicker can not occur;
OOK modulator: the modulation of the information after dimming is realized;
a Light Emitting Diode (LED): converting the electrical signal into an optical signal suitable for transmission over an optical wireless channel;
a photoelectric detector: converting an optical signal received from an optical wireless channel into an electrical signal;
OOK demodulator: the demodulation of the received electric signal is realized;
dimming decoder: removing the dimming code of the sending end, and recovering to obtain a CRC (cyclic redundancy check) block;
and a CRC decoder: performing CRC on the received check block, and detecting whether the received check block is correct;
an FEC decoder: and decoding the FEC coding block which is received correctly, and recovering to obtain data information.
2. A dimming control method of a dimming device in a visible light communication system is characterized in that: dimming control in the visible light communication system is realized through the dimming codes of the check blocks to be sent; the method comprises the following specific steps:
the method comprises the following steps: a transmitter of the visible light communication system carries out block processing on information data to be transmitted, wherein the information data to be transmitted is processed by less than one block; sending each data block to an FEC encoder one by one;
step two: for each data block, an FEC encoder encodes according to the adopted channel coding scheme to generate a coding block; sending each coding block to a CRC coder one by one;
step three: performing CRC encoding on each encoding block to generate a check block; sending each check block to a dimming encoder one by one;
step four: for each check block, the dimming encoder blocks according to a certain length; thereby dividing each check block into a plurality of check sub-blocks; for each check sub-block, dimming coding is carried out, the dimming sub-blocks meeting the dimming requirement are obtained through coding, and finally the dimming blocks meeting the dimming requirement are formed; dividing each check block into a plurality of check sub-blocks with the length of M; in order to obtain a dimming value, dimming coding is carried out on each check sub-block with the length of M into a dimming sub-block with the length of N, wherein the value of N must satisfy the requirement
Figure DEST_PATH_IMAGE003
；
Step five: modulating a dimming block output by a dimming encoder in an OOK mode, and sending a modulated electric signal to an LED;
step six: the LED performs photoelectric conversion, converts the electric signal into an optical signal and sends the optical signal into a wireless optical channel for transmission;
step seven: after a receiver of the visible light communication system receives an optical signal, a photoelectric detector converts the received optical signal into an OOK modulated electrical signal;
step eight: the OOK modulated electric signal obtained by conversion is sent to an OOK demodulator for demodulation, and a dimming block is obtained;
step nine: the dimming block is sent to a dimming decoder for decoding to obtain a check block; sending the check block to a CRC detector;
step ten: the CRC detector performs CRC detection on each check block and judges whether the received check block is correct or not; the incorrect check block is deleted, and only the coding block in the check block detected by the CRC is sent to the FEC decoder;
step eleven: and the FEC decoder decodes according to the decoding rule to recover the data block.
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