Visible light communication system and method based on DCO-OFDM modulation

Abstract

The invention relates to the technical field of visible light communication, in particular to a DCO-OFDM modulation-based visible light communication system and method, and the system comprises a first upper computer module, a transmitter module, a receiver module and a second upper computer module. Digital modulation and demodulation of DCO-OFDM are achieved through GNU Radio software, the illumination integrated visible light communication system is achieved, the DCO-OFDM digital modulation and demodulation technology is adopted, the system frequency spectrum utilization rate and the anti-multipath capacity are greatly improved, the system effectiveness and reliability are improved, and the system can be applied to informatization complex traffic scenes in the future, and has wide application prospects. The visible light communication system has practical significance and practical application value, so that the problem of low reliability of the traditional visible light communication system is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of visible light communication, and in particular to a visible light communication system and method based on DCO-OFDM modulation. Background Art

[0002] Nowadays, wireless communication is developing rapidly, and various emerging services such as mobile Internet and streaming media have penetrated into every corner of people's lives and work, bringing great convenience to people. However, at the same time, traditional wireless radio frequency (RF) communication technology has gradually revealed many problems and shortcomings.

[0003] Traditional radio frequency communication will cause huge safety risks in electromagnetic sensitive environments such as aviation, hospitals, gas stations, and military chemical sites. Visible light communication takes into account both lighting and communication, and can provide a green and safe information exchange channel for communication in electromagnetic sensitive environments. In addition, in the complex electromagnetic environment of informatization, wireless communication based on traditional radio frequency is not only prone to mutual interference with other radio equipment in the same frequency band, but also the transmitted information is easily eavesdropped or intercepted, causing information leakage, crosstalk and other security issues. Summary of the invention

[0004] The object of the present invention is to provide a visible light communication system and method based on DCO-OFDM modulation, aiming to solve the problem of low reliability of traditional visible light communication systems.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a visible light communication system based on DCO-OFDM modulation.

[0006] It includes a host computer module 1, a transmitter module, a receiver module and a host computer module 2; the host computer module 1, the transmitter module, the receiver module and the host computer module 2 are connected in sequence;

[0007] The host computer module 1 is used to process the digital signal 1;

[0008] The transmitter module is used to convert the processed digital signal into a differential analog electrical signal and send it to the receiver module;

[0009] The receiver module is used to receive the differential analog electrical signal and convert it into a digital signal;

[0010] The host computer module 2 is used to process the digital signal 2.

[0011] Wherein, the transmitter module comprises an Ethernet card unit 1, an FPGA control unit 1 and a DAC conversion unit, and the Ethernet card unit 1, the FPGA control unit 1 and the DAC conversion unit are connected in sequence;

[0012] The Ethernet card unit 1 is used to send the processed digital signal to the FPGA control unit 1;

[0013] The FPGA control unit 1 is used to package the processed digital signal;

[0014] The DAC conversion unit is used to convert the digital signal after the packaging process into a differential analog electrical signal and send it to the receiver module.

[0015] Wherein, the receiver module includes an Ethernet card unit 2, a FPGA control unit 2 and an ADC conversion unit, and the Ethernet card unit 2, the FPGA control unit 2 and the ADC conversion unit are connected in sequence;

[0016] The Ethernet card unit 2 is used to send the differential analog electrical signal to the FPGA control unit 2;

[0017] The second FPGA control unit is used to remove DC from the differential analog electrical signal;

[0018] The ADC conversion unit is used to pre-process the differential analog electrical signal after the DC removal process to obtain a digital signal 2 and transmit it to the host computer module 2.

[0019] Among them, in "the ADC conversion unit is used to pre-process the differential analog electrical signal after DC removal processing, obtain digital signal two and transmit it to the host computer module two", the pre-processing includes signal conversion processing, shaping processing, filtering processing and amplification processing.

[0020] In a second aspect, a visible light communication method based on DCO-OFDM modulation is used in the visible light communication system based on DCO-OFDM modulation according to the first aspect, comprising the following steps:

[0021] The transmitting end performs DCO-OFDM modulation and optical signal transmission;

[0022] The receiving end receives the optical signal and performs DCO-OFDM demodulation.

[0023] Among them, in “DCO-OFDM modulation and optical signal transmission at the transmitting end”, the following steps are included:

[0024] Packing the digital signal to obtain a data frame;

[0025] Performing constellation mapping and signal merging on the data frame to obtain a frame of data;

[0026] Transform a frame of data to obtain a time domain signal;

[0027] The time domain signal is converted into an optical signal and sent to the receiving end.

[0028] Among them, in “receiving optical signals and demodulating DCO-OFDM at the receiving end”, the following steps are included:

[0029] Receive optical signals and convert them into electrical signals;

[0030] Convert the electrical signal to obtain a digital signal;

[0031] Perform frame header and data demodulation on the digital signal to obtain the header part and data part of a frame of data;

[0032] Process the header part and the data part of a frame of data in sequence;

[0033] The header part and the data part of a frame of processed data are channel-decoded to obtain a video file, and the data is stored.

[0034] A visible light communication system based on DCO-OFDM modulation of the present invention comprises a host computer module 1, a transmitter module, a receiver module and a host computer module 2; the host computer module 1, the transmitter module, the receiver module and the host computer module 2 are connected in sequence; the host computer module 1 is used to process a digital signal 1; the transmitter module is used to convert the processed digital signal into a differential analog electrical signal and send it to the receiver module; the receiver module is used to receive the differential analog electrical signal and convert it into a digital signal 2; the host computer module 2 is used to process the digital signal 2. The present invention realizes a visible light communication system with integrated illumination by using GNURadio software to realize digital modulation and demodulation of DCO-OFDM, and adopts DCO-OFDM digital modulation and demodulation technology to greatly increase the system spectrum utilization and anti-multipath capability, improve the system effectiveness and reliability, and can be applied to complex information traffic scenes in the future, which has practical significance and practical application value, thereby solving the problem of low reliability of traditional visible light communication systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 Schematic diagram of digital signal processing at the transmitter.

[0037] Figure 2 This is a schematic diagram of digital signal processing at the receiving end.

[0038] Figure 3 Time domain waveform of the digital signal at the sending end.

[0039] Figure 4 Frequency domain waveform of the digital signal at the sending end.

[0040] Figure 5 Time domain waveform of the digital signal at the receiving end.

[0041] Figure 6 Frequency domain waveform of the digital signal at the receiving end.

[0042] Figure 7 The video information playback screen received by the receiving end.

[0043] Figure 8 It is a flow chart of a visible light communication method based on DCO-OFDM modulation provided by the present invention.

[0044] Fig. 9 It is a flow chart of DCO-OFDM modulation and optical signal transmission at the transmitting end.

[0045] Fig.10 It is a flow chart of optical signal reception and DCO-OFDM demodulation at the receiving end.

[0046] Fig.11 It is a schematic diagram of a visible light communication system based on DCO-OFDM modulation provided by the present invention.

[0047] Fig.12 is a schematic diagram of the transmitter module.

[0048] Fig.13 is a schematic diagram of the receiver module.

[0049] In the figure: 1-host computer module 1, 2-transmitter module, 3-receiver module, 4-host computer module 2, 21-Ethernet card unit 1, 22-FPGA control unit 1, 23-DAC conversion unit, 31-Ethernet card unit 2, 32-FPGA control unit 2, 33-ADC conversion unit. DETAILED DESCRIPTION

[0050] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0051] See also Figures 11 to 13 In a first aspect, the present invention provides a visible light communication system based on DCO-OFDM modulation.

[0052] It includes a host computer module 1, a transmitter module 2, a receiver module 3 and a host computer module 2 4; the host computer module 1, the transmitter module 2, the receiver module 3 and the host computer module 2 4 are connected in sequence;

[0053] The host computer module 1 is used to process the digital signal 1;

[0054] The transmitter module 2 is used to convert the processed digital signal into a differential analog electrical signal and send it to the receiver module 3;

[0055] The receiver module 3 is used to receive the differential analog electrical signal and convert it into a digital signal 2;

[0056] The host computer module 2 4 is used to process the digital signal 2.

[0057] In this embodiment, the host computer module 1 is used to process digital signal 1; the transmitter module 2 is used to convert the processed digital signal into a differential analog electrical signal and send it to the receiver module 3; the receiver module 3 is used to receive the differential analog electrical signal and convert it into digital signal 2; the host computer module 2 4 is used to process the digital signal 2. The present invention realizes a visible light communication system with integrated illumination by using GNU Radio software through DCO-OFDM digital modulation and demodulation. The use of DCO-OFDM digital modulation and demodulation technology greatly increases the system spectrum utilization and anti-multipath capability, improves the system effectiveness and reliability, and can be applied to complex information traffic scenes in the future. It has practical significance and practical application value, thereby solving the problem of low reliability of traditional visible light communication systems.

[0058] Further, the transmitter module 2 includes an Ethernet card unit 21, an FPGA control unit 22 and a DAC conversion unit 23, and the Ethernet card unit 21, the FPGA control unit 22 and the DAC conversion unit 23 are connected in sequence;

[0059] The Ethernet card unit 1 21 is used to send the processed digital signal to the FPGA control unit 1 22;

[0060] The FPGA control unit 22 is used to package the processed digital signal;

[0061] The DAC conversion unit 23 is used to convert the digital signal after the packaging process into a differential analog electrical signal and send it to the receiver module 3.

[0062] In this embodiment, the Ethernet card unit 21 is used to send the processed digital signal to the FPGA control unit 22; the FPGA control unit 22 is used to package the processed digital signal; the DAC conversion unit 23 is used to convert the packaged digital signal into a differential analog electrical signal and send it to the receiver module 3.

[0063] Further, the receiver module 3 includes an Ethernet card unit 2 31, a FPGA control unit 2 32 and an ADC conversion unit 33, and the Ethernet card unit 2 31, the FPGA control unit 2 32 and the ADC conversion unit 33 are connected in sequence;

[0064] The second Ethernet card unit 31 is used to send the differential analog electrical signal to the second FPGA control unit 32;

[0065] The FPGA control unit 2 32 is used to remove DC from the differential analog electrical signal;

[0066] The ADC conversion unit 33 is used to pre-process the differential analog electrical signal after the DC removal process to obtain a digital signal 2 and transmit it to the host computer module 2 4.

[0067] The preprocessing includes signal conversion processing, shaping processing, filtering processing and amplification processing.

[0068] In this embodiment, the Ethernet card unit 2 31 sends the differential analog electrical signal to the FPGA control unit 2 32; the FPGA control unit 2 32 removes DC from the differential analog electrical signal; the ADC conversion unit 33 sequentially performs signal conversion processing, shaping processing, filtering processing and amplification processing on the differential analog electrical signal after the DC removal processing to obtain a digital signal 2 and transmit it to the host computer module 2 4.

[0069] The host computer is a computer equipped with a LINUX operating system, and the open source GNU Radio software is used to implement the digital signal processing of the baseband. The GNU Radio software was developed by Eric Blossom. GNU Radio uses C++ language and Python scripting language for mixed programming. The efficient C++ language develops complex signal processing modules (called blocks) to ensure real-time performance, and Python is used to implement advanced organization, strategy, graphical interface and other functions that do not require high computing performance. The present invention uses GNU Radio software to realize the sending and receiving of information through two computers, that is, the baseband digital signal processing at the transmitting end and the baseband digital signal processing at the receiving end. The transmitter and the receiver are composed of Ethernet card, FPGA control module, ADC / DAC and other modules. The system sends the digital signal processed by the host computer to the FPGA control module through the Ethernet card, and then converts it into an analog signal through DAC and inputs it into the transmitter circuit after being processed by the Butterworth filter. The transmitter transmits the modulated signal to the receiver through the atmospheric channel. The receiver converts the received optical signal into a differential analog electrical signal. After filtering by a Butterworth filter, the ADC module at the receiving end samples the analog electrical signal into a digital signal. Finally, the FPGA control module sends the digital signal to the host computer for digital signal processing.

[0070] See also Figures 1 to 10 In a second aspect, a visible light communication method based on DCO-OFDM modulation is used in the visible light communication system based on DCO-OFDM modulation according to the first aspect, comprising the following steps:

[0071] The S1 transmitter performs DCO-OFDM modulation and optical signal transmission;

[0072] S11 performs data packaging on the digital signal to obtain a data frame;

[0073] Specifically, at the transmitting end, GNU Radio (open source software radio) software is used to implement DCO-OFDM (direct current biased optical orthogonal frequency division multiplexing) modulation of the signal. First, the File Source (file source) module is used to select the video file as the source, and the FEC Extended Encoder (forward error correction extended encoder) module is used to implement (2, 1, 7) convolution coding. The data stream Payload (payload, i.e., original data) is packaged using the Stream to tagged Stream (data stream is converted to a tagged data stream) module to form a frame data stream with a data frame length of 192 bytes, and a 4-byte CRC (cyclic redundancy check) check code is formed for each frame of data and attached to the end of each frame of data, so the length of a frame of data is 196 bytes, and a frame header is created for each frame of data, and the length of the frame header is 6 bytes.

[0074] S12 performs constellation mapping and signal merging of the data frame to obtain a frame of data;

[0075] Specifically, constellation mapping is performed on the frame header and valid data parts respectively, the frame header is mapped with BPSK (binary phase shift keying), and the valid data is mapped with QAM16 (16-order quadrature amplitude modulation) to realize the conversion of data block to symbol stream, and then the frame header and data signals are merged into one frame of data through the Tagged Stream Mux (frame header data merger) module.

[0076] S13 transforms a frame of data to obtain a time domain signal;

[0077] Specifically, the data is transformed with Hermitian symmetry, and the frequency domain signal after Hermitian symmetry is transformed with IFFT (Inverse Fourier Transform) and a cyclic prefix is ​​added to obtain the time domain signal (see the attached figure). Figure 4 As shown), the signal is finally sent to the transmitter using the UHD:USRP SINK (data sending) module.

[0078] S14 converts the time domain signal to obtain an optical signal and sends it to the receiving end.

[0079] Specifically, the signal can be converted into an analog signal through a DAC (digital analog converter) in the transmitter, and then a DC bias is added to the signal to achieve the conversion from a bipolar signal to a unipolar signal to obtain a baseband signal. The baseband signal is driven by a driving circuit to emit light, thereby realizing the conversion of an electrical signal to an optical signal, and the optical carrier reaches the receiving end through the channel. The modulation bandwidth itself is very small, and fast data communication cannot be performed; the modulation bandwidth can be significantly improved through hardware equalization technology to solve the above problem.

[0080] The S2 receiving end performs optical signal reception and DCO-OFDM (DC-biased optical orthogonal frequency division multiplexing) demodulation.

[0081] S21 receives the optical signal and converts it into an electrical signal;

[0082] Specifically, at the receiving end, a photodetector is used to convert the optical signal into an electrical signal.

[0083] S22 converts the electrical signal to obtain a digital signal;

[0084] Specifically, the signal is sent to the receiver after DC removal, and the received analog electrical signal is converted into a digital signal through an ADC (analog-to-digital converter) and sent to the receiving host after being shaped, filtered, amplified, and other processes.

[0085] S23 performs frame header and data demodulation on the digital signal to obtain a header portion and a data portion of a frame of data;

[0086] Specifically, first use the UHD:USRP Source (data reception) module to obtain the received signal. The data output by the UHD:USRPSource (data reception) module is divided into two paths. One path of data enters the multiplication module after synchronization (Schmidl&Cox OFDMsynch (orthogonal frequency division multiplexing synchronization of time and frequency based on a training sequence of two orthogonal frequency division multiplexing symbols) module) and frequency modulation (FrequencyMod module); the other path of data enters the multiplication module after a delay of one DCO-OFDM (DC bias optical orthogonal frequency division multiplexing) symbol period. After the two signals enter the multiplication module, the header part and the data part of a frame of data are separated by the header load separator module (Header / Payload Demux).

[0087] S24 processes the header part and the data part of a frame of data in sequence;

[0088] Specifically, the frame header first enters the FFT (Fourier transform) module for Fourier transform, and then enters the OFDM Channel Estimation (Orthogonal Frequency Division Multiplexing Channel Estimation) module. After passing through this module, two parameters, integer frequency offset and system frequency domain response, are obtained. Then the data stream enters the OFDM Frame Equalizer (Orthogonal Frequency Division Multiplexing Frame Equalizer) module with these two parameters to correct the integer frequency offset and equalize the signal. Then, the OFDM Serializer (Orthogonal Frequency Division Multiplexing Parallel to Serial Conversion) module is used to realize the conversion from parallel data to serial data, and the information after BPSK (Binary Phase Shift Keying) demapping is returned to the frame header and data separation module as a label. After receiving the decoded frame header information, the frame header and data separation module processes the data information. The data part first enters the FFT (Fourier transform) module for Fourier transform, and then enters the OFDM Frame Equalizer (orthogonal frequency division multiplexing frame equalizer) module and OFDMSerializer (orthogonal frequency division multiplexing parallel-to-serial conversion) module to realize frame equalization and parallel-to-serial conversion processing, and then the data information is QAM16 (16-order quadrature amplitude modulation) demapping.

[0089] S25 performs channel decoding on the header part and the data part of the processed frame of data to obtain a video file, and stores the data thereof;

[0090] Specifically, after checking and removing the CRC (cyclic redundancy check) check word, the FEC Extended (forward error correction extended decoder) module is used to perform channel decoding, and the decoded data flows into the File Sink (file storage) module and a storage path is selected to store the received video file.

[0091] S26 plays videos and broadcasts live based on video files.

[0092] Specifically, by using VLC mediaplayer (open source multimedia player) software to play the received video file, the effect of real-time live broadcast can be achieved.

[0093] Beneficial effects:

[0094] 1. The present invention realizes a visible light communication system with integrated illumination by using GNU Radio software and DCO-OFDM digital modulation and demodulation technology.

[0095] 2. The use of DCO-OFDM digital modulation and demodulation technology greatly increases the system spectrum utilization and anti-multipath capability, and improves the system effectiveness and reliability.

[0096] The above disclosure is only a preferred embodiment of a visible light communication system and method based on DCO-OFDM modulation of the present invention. Of course, this cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A visible light communication system based on DCO-OFDM modulation, characterized in that: It includes a host computer module 1, a transmitter module, a receiver module and a host computer module 2; the host computer module 1, the transmitter module, the receiver module and the host computer module 2 are connected in sequence; The host computer module 1 is used to process the digital signal 1; The transmitter module is used to convert the processed digital signal into a differential analog electrical signal and send it to the receiver module; The receiver module is used to receive the differential analog electrical signal and convert it into a digital signal; The host computer module 2 is used to process the digital signal 2.

2. The visible light communication system based on DCO-OFDM modulation as claimed in claim 1, characterized in that: The transmitter module comprises an Ethernet card unit 1, an FPGA control unit 1 and a DAC conversion unit, wherein the Ethernet card unit 1, the FPGA control unit 1 and the DAC conversion unit are connected in sequence; The Ethernet card unit 1 is used to send the processed digital signal to the FPGA control unit 1; The FPGA control unit 1 is used to package the processed digital signal; The DAC conversion unit is used to convert the digital signal after the packaging process into a differential analog electrical signal and send it to the receiver module.

3. The visible light communication system based on DCO-OFDM modulation as claimed in claim 2, characterized in that: The receiver module includes an Ethernet card unit 2, a FPGA control unit 2 and an ADC conversion unit, wherein the Ethernet card unit 2, the FPGA control unit 2 and the ADC conversion unit are connected in sequence; The Ethernet card unit 2 is used to send the differential analog electrical signal to the FPGA control unit 2; The second FPGA control unit is used to remove DC from the differential analog electrical signal; The ADC conversion unit is used to pre-process the differential analog electrical signal after the DC processing to obtain the digital signal 2 and transmit it to the host computer module 2.

4. The visible light communication system based on DCO-OFDM modulation as claimed in claim 3, characterized in that: In "the ADC conversion unit is used to pre-process the differential analog electrical signal after DC removal to obtain digital signal 2 and transmit it to the host computer module 2", the pre-processing includes signal conversion processing, shaping processing, filtering processing and amplification processing.

5. A visible light communication method based on DCO-OFDM modulation, used in the visible light communication system based on DCO-OFDM modulation according to any one of claims 1 to 4, characterized in that: The following steps are involved: The transmitting end performs DCO-OFDM modulation and optical signal transmission; The receiving end receives the optical signal and performs DCO-OFDM demodulation.

6. The visible light communication method based on DCO-OFDM modulation according to claim 5, characterized in that: In "DCO-OFDM modulation and optical signal transmission at the transmitting end", the following steps are included: Packing the digital signal to obtain a data frame; Performing constellation mapping and signal merging on the data frame to obtain a frame of data; Transform a frame of data to obtain a time domain signal; The time domain signal is converted into an optical signal and sent to the receiving end.

7. The visible light communication method based on DCO-OFDM modulation according to claim 5, characterized in that: In "receiving optical signals and demodulating DCO-OFDM at the receiving end", the following steps are included: Receive optical signals and convert them into electrical signals; Convert the electrical signal to obtain a digital signal; Perform frame header and data demodulation on the digital signal to obtain the header part and data part of a frame of data; Process the header part and the data part of a frame of data in sequence; The header part and the data part of a frame of processed data are channel-decoded to obtain a video file, and the data is stored.

Images