WO2018129756A1 - 可见光通信系统及其同步检测方法 - Google Patents

可见光通信系统及其同步检测方法 Download PDF

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WO2018129756A1
WO2018129756A1 PCT/CN2017/071371 CN2017071371W WO2018129756A1 WO 2018129756 A1 WO2018129756 A1 WO 2018129756A1 CN 2017071371 W CN2017071371 W CN 2017071371W WO 2018129756 A1 WO2018129756 A1 WO 2018129756A1
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data
visible light
module
frame
receiving
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PCT/CN2017/071371
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English (en)
French (fr)
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吴球
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邦彦技术股份有限公司
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Publication of WO2018129756A1 publication Critical patent/WO2018129756A1/zh

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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
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2656—Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2662—Symbol synchronisation

Definitions

  • the present invention relates to the field of visible light communication, and in particular to a visible light communication system and a synchronous detection method thereof.
  • Visible Light Communication is an emerging wireless optical communication technology developed in white LED technology.
  • the LED uses the high-speed response characteristic of the LED device to modulate the signal onto the visible light of the LED for transmission.
  • the communication uses visible light as the information transmission carrier, has the influence of being immune to electromagnetic interference, is environmentally friendly, has a large transmission capacity, and can realize the combination of illumination and communication.
  • visible light communication uses visible light as the information transmission carrier, the carrier is susceptible to occlusion and multipath effects, especially in the mobile environment, because the visible light is occluded for a short time, and the multipath effect affects the reliability of visible light communication, using conventional communication.
  • the synchronous mode causes the visible light communication transceiver channel to frequently switch between synchronous and out-of-synchronization states, which lengthens the communication interruption recovery time and reduces the efficiency of visible light communication.
  • the main object of the present invention is to provide a visible light communication system, which can better maintain the synchronization of visible light communication to improve the efficiency of visible light communication.
  • the present invention provides a visible light communication system, including: a transmitting end and a receiving end;
  • the transmitting end includes a framing module, a sending module, and an analog sending front end, wherein the framing module is coupled to the sending module, and the sending module is coupled to the analog sending front end;
  • the framing module is configured to framing the received transmission data to form fixed frame length data, each frame including a frame synchronization code, a data frame control word, a valid data length, valid data, padding data, and frame check Code field
  • the sending module is configured to receive and send the fixed frame length data
  • the analog transmitting front end is configured to send the fixed frame length data in the form of a visible light signal
  • the receiving end includes an analog receiving front end, a receiving module, a synchronization detecting module and a deframing module;
  • the analog receiving front end is coupled to the receiving module, the receiving module is coupled to the synchronous detecting module, and the synchronous detecting module is coupled to the deframing module;
  • the analog receiving front end is configured to receive the visible light signal, and convert the visible light signal into the fixed frame length data
  • the receiving module is configured to receive and send the fixed frame length data
  • the synchronization detecting module is configured to perform data reception on the fixed frame length data by a byte stream, and scan a frame synchronization code
  • the demapping module is configured to parse each frame of the fixed frame length data, and output the parsed data.
  • the analog transmitting front end includes a first digital-to-analog converter and a visible light source; wherein the first digital-to-analog converter is coupled to the transmitting module, and the visible light source is coupled to the first digital-to-analog converter;
  • the first digital-to-analog converter is configured to convert the fixed frame length data into a first analog signal; the visible light source is configured to receive the first analog signal, and the first analog signal is in the form of a visible light signal Send out.
  • the analog receiving front end comprises a visible light receiving module and a second digital to analog converter;
  • the visible light receiving module is coupled to the second digital to analog converter, and the second digital to analog converter is coupled to the receiving module.
  • the visible light receiving module is configured to receive a visible light signal and convert the visible light signal into a second analog signal
  • the second digital to analog converter is configured to convert the second analog signal into the fixed frame length data.
  • the frame length of the fixed frame length data is 128 bytes long.
  • the frame synchronization code has a byte length of 1 byte
  • the data frame control word has a byte length of 2 bytes
  • the valid data length has a byte length of 1 byte.
  • the byte length of the valid data is n bytes
  • the byte length of the padding data is m bytes
  • the byte length of the frame check code field is 2 bytes
  • m 128-n -6.
  • the visible light source is an LED white light
  • the transmitting module is an OFDM transmitter
  • the receiving module is an OFDM receiver
  • the present invention also provides a visible light communication synchronization detecting method based on the above visible light communication system, the method comprising:
  • the synchronization detecting module at the receiving end is configured to perform data receiving on the fixed frame length data by a byte stream, and scan the frame synchronization code;
  • the start byte receiving counter counts the bytes of the fixed frame length data
  • the method further includes:
  • the synchronization detecting module at the receiving end continues to receive data according to the byte stream for the fixed frame length data, and scans the frame synchronization code;
  • the method further includes:
  • the deframing module of the receiving end parses each frame of the fixed frame length data, and outputs the parsed data.
  • the received transmission data is framing by the transmitting end to form fixed frame length data, so that the receiving end can correctly identify each frame of data, so as to realize the synchronization function of the transmitting and receiving data frames, thereby further It is good to maintain the synchronization of visible light communication to improve the efficiency of visible light communication.
  • FIG. 1 is a schematic diagram of functional modules of an embodiment of a visible light communication system according to the present invention.
  • FIG. 2 is a schematic diagram of functional modules of an embodiment of the analog transmitting front end of FIG. 1;
  • FIG. 3 is a schematic diagram of functional modules of an embodiment of the analog receiving front end of FIG. 1;
  • FIG. 4 is a schematic structural diagram of a frame used in a visible light communication system according to the present invention.
  • FIG. 5 is a schematic flow chart of an embodiment of a method for detecting visible light communication in a visible light communication system according to the present invention.
  • the present invention provides a visible light communication system.
  • FIG. 1 is a schematic diagram of functional modules of an embodiment of a visible light communication system according to the present invention.
  • FIG. 2 is a schematic diagram of functional modules of an embodiment of the analog transmitting front end 13 of FIG.
  • FIG. 3 is a schematic diagram of functional modules of an embodiment of the analog receiving front end 21 of FIG. 4 is a schematic structural diagram of a frame used in a visible light communication system according to the present invention.
  • the visible light communication system includes a transmitting end 1 and a receiving end 2.
  • the transmitting end 1 includes a framing module 11, a transmitting module 12, and an analog transmitting front end 13, wherein the framing module 11 is coupled to the transmitting module 12, and the transmitting module 12 is coupled to the analog transmitting front end 13.
  • the framing module 11 is configured to framing the received transmission data to form fixed frame length data.
  • the frame length of the fixed frame length data is 128 bytes.
  • Each frame contains a frame sync code, a data frame control word, a valid data length, a valid data, a padding data, and a frame check code field.
  • the frame synchronization code has a byte length of 1 byte
  • the data frame control word has a byte length of 2 bytes
  • the effective data length has a byte length of 1 byte
  • the valid data has a byte length of n words.
  • the length of the padding data is m bytes
  • the sending module 12 is configured to receive and transmit fixed frame length data.
  • the analog transmission front end 13 is for transmitting the fixed frame length data in the form of a visible light signal.
  • the analog transmitting front end 13 includes a first digital-to-analog converter 131 and a visible light source 132.
  • the first digital-to-analog converter 131 is coupled to the transmitting module 12, and the visible light source 132 is coupled to the first Digital to analog converter 131.
  • the visible light source 132 can be an LED white light, and the transmitting module 12 can be an OFDM transmitter.
  • the first digital-to-analog converter 131 is configured to convert the fixed frame length data into a first analog signal; the visible light source 132 is configured to receive the first analog signal and transmit the first analog signal as a visible light signal.
  • the receiving end 2 includes an analog receiving front end 21, a receiving module 22, a synchronization detecting module 23, and a demapping module 24.
  • the analog receiving front end 21 is coupled to the receiving module 22, the receiving module 22 is coupled to the synchronous detecting module 23, and the synchronous detecting module 23 is coupled.
  • the receiving module 22 can be an OFDM receiver.
  • the analog receiving front end 21 includes a visible light receiving module 22211 and a second digital to analog converter 212.
  • the visible light receiving module 22211 is coupled to the second digital to analog converter 212
  • the second digital analog converter 212 is coupled to the receiving module 22 .
  • the visible light receiving module 22211 is configured to receive a visible light signal and convert the visible light signal Switch to the second analog signal.
  • the second digital to analog converter 212 is configured to convert the second analog signal into fixed frame length data.
  • the analog receiving front end 21 is for receiving a visible light signal and converting the visible light signal into fixed frame length data.
  • the receiving module 22 is configured to receive and transmit fixed frame length data.
  • the synchronization detecting module 23 is configured to perform data reception on the fixed frame length data by a byte stream, and scan the frame synchronization code.
  • the demapping module 24 is configured to parse each frame of data of fixed frame length data and output the parsed data.
  • the transmission data is framing to form a fixed frame length data with a frame length of 128 bytes, and each frame includes a frame synchronization code and a data frame control.
  • the transmission data After the transmission data completes the framing operation, it is sent to the sending module 12, and the sending module 12 then
  • the fixed frame length data is transmitted to the analog transmitting front end 13, and the first digital-to-analog converter 131 of the analog transmitting front end 13 performs D/A data conversion on the transmitted data, and transmits the converted data to the visible light source 132, and then the visible light source 132.
  • the converted data is sent out in the form of a visible light signal.
  • the visible light receiving module 22 After receiving the visible light signal, the visible light receiving module 22 performs A/D conversion on the visible light signal via the second digital-to-analog converter 212, and then streams the converted fixed frame length by the synchronization detecting module 23 by byte stream.
  • the data is received by the data and the frame sync code is scanned.
  • the deframing module 24 parses each frame of the fixed frame length data and outputs the parsed data.
  • the received transmission data is framing by the transmitting end 1 to form fixed frame length data, so that the receiving end 2 can correctly identify each frame of data, so as to realize the synchronization function of the transceiving data frame, thereby further It is good to maintain the synchronization of visible light communication to improve the efficiency of visible light communication.
  • FIG. 5 is a schematic flow chart of an embodiment of a method for detecting visible light communication in a visible light communication system according to the present invention. Referring to FIG. 5, the process includes the following steps:
  • Step S10 The synchronization detecting module 23 of the receiving end 2 is configured to perform data receiving on the fixed frame length data by the byte stream, and scan the frame synchronization code.
  • Step S20 It is judged whether or not the first frame synchronization code is scanned. If yes, go to step S30; if no, go to step S90. (S90: It is judged that the receiving end 2 enters the out-of-synchronization state with respect to the transmitting end 1.)
  • Step S30 The start byte receiving counter counts the bytes of the fixed frame length data.
  • Step S40 When counting to reach the frame length of one data frame, continue to scan the next data frame;
  • Step S50 determining whether the second frame synchronization code is scanned, and if so, executing step S60; if not, executing step S90.
  • Step S60 When counting to reach the frame length of one data frame, continue to scan the next data frame.
  • Step S80 It is judged that the receiving end 2 enters the synchronization state with respect to the transmitting end 1.
  • the deframing module 24 of the receiving end 2 parses each frame of data of the fixed frame length data, and outputs the parsed data.
  • the detecting method of the present invention can conveniently determine the synchronization of the visible light communication of the visible light communication system.
  • step S100 may be performed.
  • Step S100 The synchronization detecting module 23 of the receiving end 2 continues to perform data reception on the fixed frame length data by the byte stream, and scans the frame synchronization code.
  • Step S110 It is judged whether the frame synchronization code is not detected 4 times in succession. If yes, go to step S80; if no, go to step S90.
  • the receiver determines that the receiver enters the out-of-synchronization state without detecting the synchronization code 4 times in order to improve the anti-interference ability of the transmission system and the quick recovery capability due to short-term interruption, because the optical transmission channel is blocked by instantaneous occlusion.
  • the short interruption or error caused by the interruption (4 frame synchronization code loss) does not affect the transmission system operation, allowing the transmission channel to enter the hold state, maintaining the current synchronization state, and continuing to parse and restore the channel data according to the original synchronization state.
  • the receiving synchronization is held for too long, such as 4 After the frame has not detected the synchronization code, the receiver enters the out-of-synchronization state.
  • the synchronization code that can be detected in the 4-frame data can continue to be in the synchronization state, which avoids the data transmission due to the short-term interference of the channel.
  • the synchronization method achieves a better transmission effect in practical applications.
  • the invention can also adjust the synchronization holding time of the receiving end 2 according to the characteristics of the actual environment, that is, the average interference duration of the visible light communication channel, and adjust the synchronization holding time of the receiving end 2 so that the holding time is longer than the average interference duration of the channel. Time to eliminate the effects of interference on the communication system.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optical Communication System (AREA)
  • Synchronisation In Digital Transmission Systems (AREA)

Abstract

本发明公开了一种可见光通信系统及其同步检测方法。本发明提供的可见光通信系统，包括：发送端和接收端；发送端包括组帧模块、发送模块和模拟发送前端，其中，所述组帧模块耦接所述发送模块，所述发送模块耦接所述模拟发送前端；所述组帧模块用于对所接收到的传输数据进行组帧以形成固定帧长数据，每个帧包含帧同步码、数据帧控制字、有效数据长度、有效数据、填充数据和帧校验码字段。在发明的可见光通信系统中，通过发送端将接收到的传输数据进行组帧以形成固定帧长数据，以便于接收端能正确识别出每帧数据，以实现收发数据帧的同步功能，从而更好保持可见光通信的同步性，以提高可见光通信的效率。

Description

可见光通信系统及其同步检测方法 技术领域
本发明涉及可见光通信领域，尤其涉及一种可见光通信系统及其同步检测方法。
背景技术
可见光通信(VLC)是一种在白光LED技术上发展起来的新兴的无线光通信技术。其利用LED器件的高速响应特性，将信号调制到LED可见光上进行传输，该通信采用可见光做为信息传输载体，具有不受电磁干扰影响、绿色环保、传输容量大、可实现照明与通信相结合等特点。由于可见光通信采用可见光做为信息传输载体，该载体容易受到遮挡、多径效应影响，特别是在移动环境中，因可见光短时被遮挡、多径效应影响可见光通信的可靠性，采用传统的通信同步方式导致可见光通信收发信道频繁在同步、失步状态间进行转换，加长了通信中断恢复的时间，降低了可见光通信的效率。
发明内容
本发明的主要目的在于提供一种可见光通信系统，可更好保持可见光通信的同步性，以提高可见光通信的效率。
为实现上述目的，本发明提供的可见光通信系统，包括：发送端和接收端；
发送端包括组帧模块、发送模块和模拟发送前端，其中，所述组帧模块耦接所述发送模块，所述发送模块耦接所述模拟发送前端；
所述组帧模块用于对所接收到的传输数据进行组帧以形成固定帧长数据，每个帧包含帧同步码、数据帧控制字、有效数据长度、有效数据、填充数据和帧校验码字段；
所述发送模块用于接收并发送所述固定帧长数据；
所述模拟发送前端用于将所述固定帧长数据以可见光信号的形式向外发送；
所述接收端包括模拟接收前端、接收模块、同步检测模块和解帧模块； 其中，所述模拟接收前端耦接所述接收模块，所述接收模块耦接所述同步检测模块，所述同步检测模块耦接所述解帧模块；
所述模拟接收前端用于接收所述可见光信号，并将所述可见光信号转换为所述固定帧长数据；
所述接收模块用于接收并发送所述固定帧长数据；
所述同步检测模块用于按字节流对所述固定帧长数据进行数据接收，并扫描帧同步码；
所述解帧模块用于解析所述固定帧长数据的每帧数据，并输出所述解析后的数据。
优选地，模拟发送前端包括第一数字模拟转换器和可见光光源；其中，所述第一数字模拟转换器耦接所述发送模块，所述可见光光源耦接所述第一数字模拟转换器；
所述第一数字模拟转换器用于将所述固定帧长数据转换为第一模拟信号；所述可见光光源用于接收所述第一模拟信号，并将所述第一模拟信号以可见光信号的形式向外发送。
优选地，模拟接收前端包括可见光接收模块和第二数字模拟转换器；
所述可见光接收模块耦接所述第二数字模拟转换器，所述第二数字模拟转换器耦接所述接收模块，
所述可见光接收模块用于接收可见光信号，并将所述可见光信号转换为第二模拟信号；
所述第二数字模拟转换器用于将所述第二模拟信号转换为所述固定帧长数据。
优选地，所述固定帧长数据的帧长采用128字节帧长。
优选地，所述帧同步码的字节长度为1个字节，所述数据帧控制字的字节长度为2个字节，所述有效数据长度的字节长度为1个字节，所述有效数据的字节长度为n个字节，所述填充数据的字节长度为m个字节，所述帧校验码字段的字节长度为2个字节，而m＝128-n-6。
优选地，所述可见光光源为LED白光灯，所述发送模块为OFDM发送器，所述接收模块为OFDM接收器。
本发明还提出一种基于上述的可见光通信系统的可见光通信同步检测方法，所述方法包括：
接收端的同步检测模块用于按字节流对固定帧长数据进行数据接收，并扫描帧同步码；
当扫描到第1个帧同步码时，启动字节接收计数器对所述固定帧长数据的字节进行计数；
当计数到达到一个数据帧的帧长时，继续扫描下一个数据帧；
当扫描到第2个帧同步码时，且当计数到达到一个数据帧的帧长时，继续扫描下一个数据帧；
当扫描到第3个帧同步码时，判断接收端相对于发送端进入同步状态。
优选地，所述当扫描到第3个帧同步码时，判断接收端相对于发送端进入同步状态的步骤之后还包括：
接收端的同步检测模块继续按字节流对固定帧长数据进行数据接收，并扫描帧同步码；
当连续4次没有检测到帧同步码时，判断接收端相对于发送端进入同步状态。
优选地，所述当扫描到第3个帧同步码时，判断接收端相对于发送端进入同步状态的步骤之后还包括：
所述接收端的所述解帧模块解析所述固定帧长数据的每帧数据，并将解析后的数据输出。
在发明的可见光通信系统中，通过发送端将接收到的传输数据进行组帧以形成固定帧长数据，以便于接收端能正确识别出每帧数据，以实现收发数据帧的同步功能，从而更好保持可见光通信的同步性，以提高可见光通信的效率。
附图说明
图1为本发明可见光通信系统一实施例的功能模块示意图；
图2为图1中模拟发送前端一实施例的功能模块示意图；
图3为图1中模拟接收前端一实施例的功能模块示意图；
图4为本发明可见光通信系统所采用帧的结构示意图；
图5为本发明可见光通信系统的可见光通信同步检测方法一实施例的流程示意图。
附图标号说明：
1发送端
11组帧模块
12发送模块
13模拟发送前端
131第一数字模拟转换器
132可见光光源
2接收端
21模拟接收前端
211可见光接收模块
212第二数字模拟转换器
22接收模块
23同步检测模块
24解帧模块
本发明目的的实现、功能特点及优点将结合实施例，参照附图做进一步说明。
具体实施方式
应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
本发明提供一种可见光通信系统。
图1为本发明可见光通信系统一实施例的功能模块示意图。图2为图1中模拟发送前端13一实施例的功能模块示意图。图3为图1中模拟接收前端21一实施例的功能模块示意图。图4为本发明可见光通信系统所采用帧的结构示意图。请结合参照图1至图4，在本实施例中，该可见光通信系统包括发送端1和接收端2。发送端1包括组帧模块11、发送模块12和模拟发送前端13，其中，组帧模块11耦接发送模块12，发送模块12耦接模拟发送前端13。
其中，组帧模块11用于对所接收到的传输数据进行组帧以形成固定帧长数据。具体请参照图4，在本实施例中，固定帧长数据的帧长采用128字节帧长。每个帧包含帧同步码、数据帧控制字、有效数据长度、有效数据、填充数据和帧校验码字段。帧同步码的字节长度为1个字节，数据帧控制字的字节长度为2个字节，有效数据长度的字节长度为1个字节，有效数据的字节长度为n个字节，填充数据的字节长度为m个字节，帧校验码字段的字节长度为2个字节，而m＝128-n-6。
发送模块12用于接收并发送固定帧长数据。
模拟发送前端13用于将固定帧长数据以可见光信号的形式向外发送。
请参照图2，在本实施例中，模拟发送前端13包括第一数字模拟转换器131和可见光光源132；其中，第一数字模拟转换器131耦接发送模块12，可见光光源132耦接第一数字模拟转换器131。其中，可见光光源132可为LED白光灯，发送模块12可为OFDM发送器。
第一数字模拟转换器131用于将固定帧长数据转换为第一模拟信号；可见光光源132用于接收第一模拟信号，并将第一模拟信号以可见光信号的形式向外发送。
接收端2包括模拟接收前端21、接收模块22、同步检测模块23和解帧模块24；其中，模拟接收前端21耦接接收模块22，接收模块22耦接同步检测模块23，同步检测模块23耦接解帧模块24。其中，接收模块22可为OFDM接收器。
请参照图3，在本实施例中，模拟接收前端21包括可见光接收模块22211和第二数字模拟转换器212。可见光接收模块22211耦接第二数字模拟转换器212，第二数字模拟转换器212耦接接收模块22。
其中，可见光接收模块22211用于接收可见光信号，并将可见光信号转 换为第二模拟信号。
第二数字模拟转换器212用于将第二模拟信号转换为固定帧长数据。
模拟接收前端21用于接收可见光信号，并将可见光信号转换为固定帧长数据。
接收模块22用于接收并发送固定帧长数据。
同步检测模块23用于按字节流对固定帧长数据进行数据接收，并扫描帧同步码。
解帧模块24用于解析固定帧长数据的每帧数据，并输出解析后的数据。
在本实施例中，组帧模块11接收到的传输数据之后，对该传输数据进行组帧以形成帧长为128字节帧长固定帧长数据，每个帧包含帧同步码、数据帧控制字、有效数据长度、有效数据、填充数据和帧校验码字段。其中数据帧控制字可根据具体应用进行定义，有效数据长度表示本数据帧有效数据字节数，填充数据在有效数据不能满帧下进行填充(固定填充字节0x55)，图4中有效数据长度为n个字节，填充数据长度m＝128-n-6，帧校验实现对整帧数据的校验，传输数据完成组帧运算后，再发往发送模块12，发送模块12再将该固定帧长数据传输给模拟发送前端13，模拟发送前端13的第一数字模拟转换器131对该传输数据进行D/A数据转换,将转换后的数据传输给可见光光源132，然后，可见光光源132将转换后的数据以可见光信号的形式向外发送。在接收端2，可见光接收模块22接收可见光信号后，经第二数字模拟转换器212对该可见光信号进行A/D转换，然后通过同步检测模块23按字节流对该转换后的固定帧长数据进行数据接收，并扫描帧同步码。接着，解帧模块24解析该固定帧长数据的每帧数据，并输出解析后的数据。
在本实施例中，通过发送端1将接收到的传输数据进行组帧以形成固定帧长数据，以便于接收端2能正确识别出每帧数据，以实现收发数据帧的同步功能，从而更好保持可见光通信的同步性，以提高可见光通信的效率。
本发明还提出了一种基于上述可见光通信系统的可见光通信同步检测方法。图5为本发明可见光通信系统的可见光通信同步检测方法一实施例的流程示意图。请参照图5，该流程包括以下步骤：
开始；
步骤S10：接收端2的同步检测模块23用于按字节流对固定帧长数据进行数据接收，并扫描帧同步码。
步骤S20：判断是否扫描到第1个帧同步码。若是，执行步骤S30；若否，执行步骤S90。(其中，S90：判断接收端2相对于发送端1进入失步状态。)
步骤S30：启动字节接收计数器对固定帧长数据的字节进行计数。
步骤S40：当计数到达到一个数据帧的帧长时，继续扫描下一个数据帧；
步骤S50：判断是否扫描到第2个帧同步码，若是，执行步骤S60；若否，执行步骤S90。
步骤S60：当计数到达到一个数据帧的帧长时，继续扫描下一个数据帧。步骤S70：判断是否扫描到第3个帧同步码，若是，执行步骤S80；若否，执行步骤S90。
步骤S80：判断接收端2相对于发送端1进入同步状态。
当判断接收端2相对于发送端1进入同步状态后，接收端2的解帧模块24解析固定帧长数据的每帧数据，并将解析后的数据输出。
在上述流程中，通过判断是否扫描到第1个帧同步码之后，接着，再判断是否扫描到第2个帧同步码，接着，再判断是否扫描到第3个帧同步码，直至连续3次扫描到帧同步码之后，进而，判断接收端2相对于发送端1进入同步状态，本发明的检测方法可很方便的判断出该可见光通信系统可见光通信的同步性。
请继续参照图5，在本实施例中，在判断接收端2相对于发送端1进入同步状态之后，可再执行步骤S100。
步骤S100：接收端2的同步检测模块23继续按字节流对固定帧长数据进行数据接收，并扫描帧同步码。
步骤S110：判断是否连续4次没有检测到帧同步码。若是，执行步骤S80；若否，执行步骤S90。
在本实施例中，采用4次没有检测到同步码而决定接收器进入失步状态是为提高传输系统的抗干扰能力和因短时中断而快速恢复能力，因为光传输通道上因瞬间遮挡而中断造成的短时的中断或误码(4个帧同步码丢失)不影响传输系统工作，可让传输通道进入保持状态，保持当前的同步状态，并继续按原同步状态解析、还原通道的数据。当接收同步保持时间过长，如4个 帧后仍未检测到同步码，则接收器进入失步状态，如在4帧数据内能检测的同步码，可继续保持在同步状态，这就避免了因信道短时间被干扰而对数据传输造成的影响。该同步方法在实际应用中获得较好的传输效果。本发明也可根据实际环境的特点，即可见光通信通道平均干扰持续时间，通过调整接收端2同步码连续丢失个数，调整接收端2的同步保持时间，使该保持时间大于通道的平均干扰持续时间，以消除干扰对通信系统的影响。
以上仅为本发明的优选实施例，并非因此限制本发明的专利范围，凡是利用本发明说明书及附图内容所作的等效结构或等效流程变换，或直接或间接运用在其他相关的技术领域，均同理包括在本发明的专利保护范围内。

Claims (9)

  1. 一种可见光通信系统，其特征在于，包括：发送端和接收端；
    发送端包括组帧模块、发送模块和模拟发送前端，其中，所述组帧模块耦接所述发送模块，所述发送模块耦接所述模拟发送前端；
    所述组帧模块用于对所接收到的传输数据进行组帧以形成固定帧长数据，每个帧包含帧同步码、数据帧控制字、有效数据长度、有效数据、填充数据和帧校验码字段；
    所述发送模块用于接收并发送所述固定帧长数据；
    所述模拟发送前端用于将所述固定帧长数据以可见光信号的形式向外发送；
    所述接收端包括模拟接收前端、接收模块、同步检测模块和解帧模块；其中，所述模拟接收前端耦接所述接收模块，所述接收模块耦接所述同步检测模块，所述同步检测模块耦接所述解帧模块；
    所述模拟接收前端用于接收所述可见光信号，并将所述可见光信号转换为所述固定帧长数据；
    所述接收模块用于接收并发送所述固定帧长数据；
    所述同步检测模块用于按字节流对所述固定帧长数据进行数据接收，并扫描帧同步码；
    所述解帧模块用于解析所述固定帧长数据的每帧数据，并输出所述解析后的数据。
  2. 如权利要求1所述的可见光通信系统，其特征在于，
    模拟发送前端包括第一数字模拟转换器和可见光光源；其中，所述第一数字模拟转换器耦接所述发送模块，所述可见光光源耦接所述第一数字模拟转换器；
    所述第一数字模拟转换器用于将所述固定帧长数据转换为第一模拟信号；所述可见光光源用于接收所述第一模拟信号，并将所述第一模拟信号以可见光信号的形式向外发送。
  3. 如权利要求1所述的可见光通信系统，其特征在于，
    模拟接收前端包括可见光接收模块和第二数字模拟转换器；
    所述可见光接收模块耦接所述第二数字模拟转换器，所述第二数字模拟转换器耦接所述接收模块，
    所述可见光接收模块用于接收可见光信号，并将所述可见光信号转换为第二模拟信号；
    所述第二数字模拟转换器用于将所述第二模拟信号转换为所述固定帧长数据。
  4. 如权利要求1所述的可见光通信系统，其特征在于，所述固定帧长数据的帧长采用128字节帧长。
  5. 如权利要求4所述的可见光通信系统，其特征在于，所述帧同步码的字节长度为1个字节，所述数据帧控制字的字节长度为2个字节，所述有效数据长度的字节长度为1个字节，所述有效数据的字节长度为n个字节，所述填充数据的字节长度为m个字节，所述帧校验码字段的字节长度为2个字节，而m＝128－n－6。
  6. 如权利要求1所述的可见光通信系统，其特征在于，所述可见光光源为LED白光灯，所述发送模块为OFDM发送器，所述接收模块为OFDM接收器。
  7. 一种基于如权利要求1－6任意一项所述的可见光通信系统的可见光通信同步检测方法，其特征在于，所述方法包括：
    接收端的同步检测模块用于按字节流对固定帧长数据进行数据接收，并扫描帧同步码；
    当扫描到第1个帧同步码时，启动字节接收计数器对所述固定帧长数据的字节进行计数；
    当计数到达到一个数据帧的帧长时，继续扫描下一个数据帧；
    当扫描到第2个帧同步码时，且当计数到达到一个数据帧的帧长时，继续扫描下一个数据帧；
    当扫描到第3个帧同步码时，判断接收端相对于发送端进入同步状态。
  8. 一种如权利要求7所述的可见光通信同步检测方法，其特征在于，所述当扫描到第3个帧同步码时，判断接收端相对于发送端进入同步状态的步骤之后还包括：
    接收端的同步检测模块继续按字节流对固定帧长数据进行数据接收，并扫描帧同步码；
    当连续4次没有检测到帧同步码时，判断接收端相对于发送端进入同步状态。
  9. 一种如权利要求7所述的可见光通信同步检测方法，其特征在于，所述当扫描到第3个帧同步码时，判断接收端相对于发送端进入同步状态的步骤之后还包括：
    所述接收端的所述解帧模块解析所述固定帧长数据的每帧数据，并将解析后的数据输出。
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