阅读说明：本技术 基于occ的车对车通信系统发射机和接收机 (OCC-based vehicle-to-vehicle communication system transmitter and receiver ) 是由 石文孝 邵馨蕊 王静怡 刘维 王春悦 孙继凤 王卓 于 2020-04-28 设计创作，主要内容包括：本发明涉及一种基于OCC的车对车通信系统发射机和接收机；其中发射机对汽车行驶安全信息进行编码处理及OFDM调制后,通过驱动电路驱动指定波长的尾灯LED阵列进行传输。接收机采用窄带滤波相机捕获前方车辆尾灯LED阵列传输的光信号,通过边缘检测算法检测出尾灯LED阵列位置,采用光斑检测等图像处理技术,获得尾灯LED阵列中各个LED携带的信息,并对LED携带信息进行解调解码处理,得到前车行驶安全信息。本发明的车对车通信系统采用光信号完成车辆间信息的交互,无射频干扰且绿色环保；同时结合OFDM技术及图像处理技术,能够实现高效可靠的汽车行驶安全信息实时传递,实现对后车的安全预警,有助于减少交通事故。(The invention relates to a vehicle-to-vehicle communication system transmitter and receiver based on OCC; after the transmitter carries out coding processing and OFDM modulation on the automobile driving safety information, the tail lamp LED array with the specified wavelength is driven by the driving circuit to be transmitted. The receiver adopts a narrow-band filtering camera to capture optical signals transmitted by a tail lamp LED array of a front vehicle, detects the position of the tail lamp LED array through an edge detection algorithm, adopts image processing technologies such as light spot detection and the like to obtain information carried by each LED in the tail lamp LED array, and demodulates and decodes the information carried by the LED to obtain driving safety information of the front vehicle. The vehicle-to-vehicle communication system adopts optical signals to complete information interaction between vehicles, has no radio frequency interference and is green and environment-friendly; meanwhile, the OFDM technology and the image processing technology are combined, so that the high-efficiency and reliable real-time transmission of the automobile driving safety information can be realized, the safety early warning of a rear automobile is realized, and the traffic accidents are reduced.)

1. A vehicle-to-vehicle communication system transmitter based on OCC is characterized by comprising a vehicle driving safety information acquisition module, a coding module, a modulation module, a driving circuit and a tail lamp LED array; the tail lamp LED array comprises a signaling LED array and a positioning LED;

the automobile driving safety information acquisition module acquires automobile driving safety information data, converts the data into a binary data code stream and sends the binary data code stream to the coding module;

the coding module adopts low-density parity check codes to code an input binary data code stream, the code length is u, and the coded data is sent to the modulation module;

the modulation module performs ACO-OFDM modulation and spatial modulation on the coded data to obtain a spatially modulated OFDM signal, and the modulation method comprises the following steps:

(1) performing serial-to-parallel conversion on the coded data, performing M-QAM mapping to obtain a plurality of complex numbers, and expressing the complex numbers as a complex vector X_QAM＝[X₀，X₁，...，X_N-1]；

(2) For complex phasor X_QAMCarrying out odd carrier allocation and conjugate symmetry operation processing to obtain a transformed frequency domain signal X ═ X₀，X₁，X₂，...，X_4N-2，X_4N-1]；

(3) IFFT conversion is carried out on the frequency domain signal X to obtain a time domain signal X ═ X₀，x₁，x₂，...，x_4N-2，x_4N-1]；

(4) Carrying out zero-value amplitude limiting operation on the time domain signal x to obtain a non-negative amplitude limiting signal x':

(5) performing parallel-to-serial conversion on the obtained x ', and then adding a cyclic prefix in front of the non-negative amplitude limiting time domain signal x' to obtain an OFDM signal;

(6) the OFDM signal amplitude is coded and converted into 2^tThe level amplitude range, the amplitude level of each OFDM signal is respectively represented by the on-off states of t signaling LEDs, and the OFDM signals after spatial modulation are obtained and transmitted into a driving circuit;

the driving circuit is used for driving the signaling LED array and sending the driving safety information of the vehicle to the rear vehicle.

2. The OCC-based vehicle-to-vehicle communication system transmitter of claim 1, wherein the peripheral LEDs of the tail light LED array serve as positioning LEDs, and the k x k LED array in the middle portion serves as a signaling LED array; and the lighting format of the positioning LEDs is different from the signaling LED array.

3. The OCC-based vehicle-to-vehicle communication system transmitter of claim 1 wherein said vehicle driving safety information comprises vehicle steering, speed, acceleration, engine speed and braking information.

4. The OCC-based vehicle-to-vehicle communication system transmitter of claim 1, wherein the non-negatively-limited time domain signal x' is added with a cyclic prefix to obtain an OFDM signal, and a symbol period of the OFDM signal is extended from T before the cyclic prefix is added to T + T_g，T_gTake a value of

5. The OCC-based vehicle-to-vehicle communication system transmitter of claim 2, wherein said signaling LED array emits light having a wavelength of 808 nm.

6. A vehicle-to-vehicle communication system receiver based on OCC is characterized by comprising a narrow-band filtering camera, an image processing module, a demodulation module and a decoding module;

the narrow-band filtering camera eliminates stray light projected on the CMOS image sensor by configuring an optical filter with 808nm in front of a camera lens, and sends a shot image to the image processing module;

the image processing module processes the shot image to obtain signaling LED array on-off state information, and the processing method comprises the following steps:

(1) converting an RGB image obtained by a narrow-band filtering camera into a gray value image, and then processing the gray value image through a self-adaptive threshold algorithm to obtain a binary image;

(2) detecting the position of a tail lamp LED array in the binary image by using an edge detection algorithm, and segmenting the tail lamp LED array region from the binary image;

(3) detecting the positions of all LED light spots in the LED array area of the tail lamp; judging the on-off state of each signaling LED, and sending a data stream representing the on-off state information of each signaling LED into a demodulation module;

the demodulation module demodulates the input data stream, and the method comprises the following steps:

(1) converting a data stream representing the on-off state information of each signaling LED into an OFDM signal;

(2) carrying out series-parallel conversion on the OFDM signal obtained in the step (1) to obtain a time domain signal y;

(3) performing FFT operation on the time domain signal Y to obtain a frequency domain signal Y, and respectively representing the information of the frequency domain signal Y on the odd carrier and the even carrier as Y_oddAnd Y_evenAnd then:

(4) extracting information Y on frequency domain signal Y odd carrier_oddObtaining the original complex signal Y_QAM：

Y_QAM＝2Y_odd(2k+1)，k＝0，...，N-1 (8)

(5) For original complex signal Y_QAMPerforming M-QAM inverse mapping to recover the data coded by the coding module, and sending the recovered coded data into a decoding module after parallel-to-serial conversion;

and the decoding module performs forward error correction on the demodulated data and decodes the demodulated data to obtain the driving safety information of the front vehicle.

7. The OCC-based vehicle-to-vehicle communication system receiver of claim 6, wherein the image processing module is configured to segment the area of the taillight LED array from the binary image after detecting the taillight LED array, and determine the start position of the signaling LED array by locating the LEDs.

8. The OCC-based vehicle-to-vehicle communication system receiver of claim 7, wherein the image processing module, the method for detecting the position of the light spot in the LED array area of the tail light is as follows: removing detected lightTaking the average value S of the remaining spot areas_avg(ii) a Let the light spot area of the mth light spot be S_mTraversing all the light spots according to a formula (4), and judging whether each light spot is an LED:

wherein, the error area P represents the set allowable calculation_LED，m1 means that the mth light spot is a tail light LED, and conversely, the mth light spot is a noise light spot;

let the spot coordinates of the upper left corner, the upper right corner and the lower left corner in the spots of the positioning LEDs at the outermost side of the tail lamp LED array be respectively expressed as (x)_ulc,y_ulc)、(x_urc,y_urc)、(x_llc,y_ullc) Calculating the average value d of the interval between the signaling LED light spots according to the coordinate information of the three positioning LED light spots_avg：

Wherein k is the number of rows (columns) of the signaling LED array;

let i denote the row number of the signaling LED, j denote the column number of the signaling LED, and i is more than or equal to 1, j is less than or equal to k, and k is the row number and the column number of the signaling LED array; according to the positions of the LED light spots and the average value d of the intervals between the LED light spots_avgThe center position (x) of each signaling LED light spot is estimated_i，y_j)。

9. The OCC-based vehicle-to-vehicle communication system receiver of claim 8, wherein the image processing module determines the on/off status of each signaling LED according to equation (6):

wherein (x)₁，y₁) The estimated center point of the 1 st row and 1 st column signaling LED is obtained;for the set error unit allowed for calculation, S_LED，ijIf the signal is 1, the state of the LED (i, j) is on, which represents "1", otherwise, the signal is off, which represents "0", therefore, the information of "0" and "1" carried by each signaling LED in the signaling LED array can be obtained, and the signaling LED array state matrix can be obtained.

Technical Field

The invention relates to the technical field of visible light communication and intelligent traffic, in particular to a vehicle-to-vehicle communication system transmitter and receiver based on OCC.

Background

Ensuring the driving safety of automobiles is one of the important research subjects for the development of the automobile field. The communication system is used as the core of information interaction between vehicles, and can realize safety early warning by transmitting vehicle running safety information such as steering, speed, acceleration, engine speed, brake and the like in the running process of the vehicle, thereby effectively improving the running safety and reliability of the vehicle. However, the wireless radio frequency communication mode is susceptible to radio frequency interference, and cannot meet the requirement of real-time interaction of driving safety information between vehicles under the condition of serious radio frequency interference, so that a communication technology with low time delay and strong anti-interference capability is urgently needed, and multiple guarantees are provided for the driving safety of the vehicles.

The visible Camera Communication (OCC) is a wireless Optical Communication technology that transmits Optical signals using Light Emitting Diodes (LEDs) and receives the Optical signals through an image sensor array, and can simultaneously identify a plurality of transmitting Light sources and realize parallel reception of the signals. The OCC technology takes light as a carrier, has the advantages of no radio frequency interference, no need of spectrum authentication, no electromagnetic radiation, environmental protection and the like, and can effectively make up for the defects of wireless radio frequency communication. With the wide application of LEDs and vehicle-mounted cameras in the automotive field, the OCC technology has become a key technology for realizing vehicle-to-vehicle communication and preventing traffic accidents, and has received wide attention from academia.

Orthogonal Frequency Division Multiplexing (OFDM) technology can effectively improve the performance of a communication system, improve the information transmission rate and the anti-interference capability, and become an important modulation mode for realizing high-speed and reliable visible light communication. The result of the OFDM modulation output is a bipolar complex signal, which cannot be directly used for a visible light communication system adopting an intensity modulation/direct detection method, so that the OFDM modulation technology is introduced into optical communication and needs to process the OFDM signal. Currently, three types of OFDM technologies capable of achieving the signal positive real-valued requirement mainly include a DC-biased orthogonal frequency division multiplexing (DCO-OFDM), an asymmetric clipping orthogonal frequency division multiplexing (ACO-OFDM), and a single-polarity orthogonal frequency division multiplexing (unipolar OFDM, U-OFDM). LED-based visible light communication dimming technologies are classified into three categories: analog dimming techniques, digital dimming techniques, and spatial dimming techniques. The analog dimming technology performs dimming by changing the amplitude of an LED driving signal, the digital dimming technology performs dimming by changing the duty ratio of the LED driving signal, and the spatial modulation technology adjusts the light power by activating a part of LEDs in a light source to work.

In the existing research of the OCC, each LED included in the LED array is mostly used to transmit the same information, and there is still a large research space for implementing parallel transmission of information by using the LED array. At present, a visible light communication system based on an OFDM modulation technology mostly uses a Photodiode (PD) as a receiving end, is mostly used for indoor communication, has a small distance variation range of a transmitting end and a receiving end, and can distinguish a signal with a large OFDM amplitude range by the PD. When the camera is used as the receiving end of the OFDM optical signal, since the gray value range of the camera is limited and the dynamic range of the transmission distance between the vehicle-to-vehicle communication systems is large, how the camera accurately receives the OFDM optical signal still needs to be further researched.

Disclosure of Invention

The invention provides an OCC-based vehicle-to-vehicle communication system transmitter and a receiver, wherein the transmitter adopts an automobile tail lamp LED array to transmit optical signals, the receiver adopts an image sensor to receive the optical signals and adopts OFDM and image processing technologies to complete modulation and demodulation of automobile driving safety information, the automobile driving safety information can be transmitted in real time, safety early warning is realized, and traffic accidents are reduced.

In order to solve the technical problem, the OCC-based vehicle-to-vehicle communication system transmitter comprises an automobile driving safety information acquisition module, a coding module, a modulation module, a driving circuit and a tail lamp LED array; the tail lamp LED array comprises a signaling LED array and a positioning LED;

the automobile driving safety information acquisition module acquires automobile driving safety information data, converts the data into a binary data code stream and sends the binary data code stream to the coding module;

the coding module adopts low-density parity check codes to code an input binary data code stream, the code length is u, and the coded data is sent to the modulation module;

the modulation module performs ACO-OFDM modulation and spatial modulation on the coded data to obtain a spatially modulated OFDM signal, and the modulation method comprises the following steps:

(1) performing serial-to-parallel conversion on the coded data, performing M-QAM mapping to obtain a plurality of complex numbers, and expressing the complex numbers as a complex vector X_QAM＝[X₀，X₁，...，X_N-1]；

(2) For complex phasor X_QAMCarrying out odd carrier allocation and conjugate symmetry operation processing to obtain a transformed frequency domain signal X ═ X₀，X₁，X₂，...，X_4N-2，X_4N-1]；

(3) IFFT conversion is carried out on the frequency domain signal X to obtain a time domain signal X ═ X₀，x₁，x₂，...，x_4N-2，x_4N-1]；

(4) Carrying out zero-value amplitude limiting operation on the time domain signal x to obtain a non-negative amplitude limiting signal x':

(5) performing parallel-to-serial conversion on the obtained x ', and then adding a cyclic prefix in front of the non-negative amplitude limiting time domain signal x' to obtain an OFDM signal;

(6) the OFDM signal amplitude is coded and converted into 2^tThe level amplitude range, the amplitude level of each OFDM signal is respectively represented by the on-off states of t signaling LEDs, and the OFDM signals after spatial modulation are obtained;

the driving circuit is used for driving the signaling LED array and sending the driving safety information of the vehicle to the rear vehicle.

The peripheral LEDs at the edge of the tail lamp LED array are used as positioning LEDs, and the k multiplied by k LED array at the middle part is used as a signaling LED array; and the lighting format of the positioning LEDs is different from the signaling LED array.

The automobile driving safety information comprises automobile steering, speed, acceleration, engine rotating speed and brake information.

The non-negative amplitude limiting time domain signal x' is added with a cyclic prefix to obtain an OFDM signal, and the symbol period of the OFDM signal is expanded from T before the cyclic prefix is added to T + T_g，T_gTake a value of

The wavelength of light waves emitted by the signaling LED array is 808 nm.

The OCC-based vehicle-to-vehicle communication system receiver comprises a narrow-band filtering camera, an image processing module, a demodulation module and a decoding module;

the narrow-band filtering camera eliminates stray light projected on the CMOS image sensor by configuring an optical filter with 808nm in front of a camera lens, and sends a shot image to the image processing module;

the image processing module processes the shot image to obtain signaling LED array on-off state information, and the processing method comprises the following steps:

(1) converting an RGB image obtained by a narrow-band filtering camera into a gray value image, and then processing the gray value image through a self-adaptive threshold algorithm to obtain a binary image;

(2) detecting the position of a tail lamp LED array in the binary image by using an edge detection algorithm, and segmenting the tail lamp LED array region from the binary image;

(3) detecting the position of a light spot in the LED array area of the tail lamp; judging the on-off state of each signaling LED, and sending a data stream representing the on-off state information of each signaling LED into a demodulation module;

the demodulation module demodulates the input data stream, and the method comprises the following steps:

(1) converting a data stream representing the on-off state information of each signaling LED into an OFDM signal;

(2) carrying out series-parallel conversion on the OFDM signal obtained in the step (1) to obtain a time domain signal y;

(3) performing FFT operation on the time domain signal Y to obtain a frequency domain signal Y, and respectively representing the information of the frequency domain signal Y on the odd carrier and the even carrier as Y_oddAnd Y_evenAnd then:

(4) extracting information Y on frequency domain signal Y odd carrier_oddObtaining the original complex signal Y_QAM：

Y_QAM＝2Y_odd(2k+1)，k＝0，...，N-1 (8)

(5) For original complex signal Y_QAMPerforming M-QAM inverse mapping to recover the data coded by the coding module, and sending the recovered coded data into a decoding module after parallel-to-serial conversion;

and the decoding module performs forward error correction on the demodulated data and decodes the demodulated data to obtain the driving safety information of the front vehicle.

After the image processing module detects the tail lamp LED array, the tail lamp LED array area is divided from the binary image, and the initial position of the signaling LED array is determined by the positioning LED.

The image processing module and the method for detecting the position of the light spot in the LED array area of the tail light are as follows: removing three maximum areas and three minimum areas in the detected light spots, and taking the average value S of the remaining light spot areas_avg(ii) a Let the light spot area of the mth light spot be S_mTraversing all the light spots according to a formula (4), and judging whether each light spot is an LED:

wherein, the error area P represents the set allowable calculation_LED，m1 denotes the firstThe m light spots are tail lamp LEDs, and conversely are noise light spots;

let the spot coordinates of the upper left corner, the upper right corner and the lower left corner in the spots of the positioning LEDs at the outermost side of the tail lamp LED array be respectively expressed as (x)_ulc,y_ulc)、(x_urc,y_urc)、(x_llc,y_ullc) Calculating the average value d of the interval between the signaling LED light spots according to the coordinate information of the three positioning LED light spots_avg：

Wherein k is the number of rows (columns) of the signaling LED array;

let i denote the row number of the signaling LED, j denote the column number of the signaling LED, and i is more than or equal to 1, j is less than or equal to k, and k is the row number and the column number of the signaling LED array; according to the positions of the LED light spots and the average value d of the intervals between the LED light spots_avgThe center position (x) of each signaling LED light spot is estimated_i，y_j)。

The image processing module judges the on-off state of each signaling LED according to the formula (6):

wherein (x)₁，y₁) The estimated center point of the 1 st row and 1 st column signaling LED is obtained; for the set error unit allowed for calculation, S_LED，ijIf the signal is 1, the state of the LED (i, j) is on, which represents "1", otherwise, the signal is off, which represents "0", therefore, the information of "0" and "1" carried by each signaling LED in the signaling LED array can be obtained, and the signaling LED array state matrix can be obtained.

The transmitter of the invention carries out coding processing and OFDM modulation on automobile driving safety information such as steering, speed, acceleration, engine rotating speed, brake and the like, and maps the modulated data to the LED array with specified wavelength for transmission. The receiver adopts a narrow-band filtering camera to capture optical signals, detects the position of the LED array through an edge detection algorithm, adopts image processing technologies such as light spot detection and the like to obtain information carried by each LED lamp in the LED array, and demodulates and decodes the information carried by the LED to obtain the driving safety information of the front vehicle. The vehicle-to-vehicle communication system provided by the invention adopts optical signals to complete information interaction between vehicles, has no radio frequency interference and is green and environment-friendly. Meanwhile, the OFDM technology and the image processing technology are combined, so that efficient and reliable information real-time transmission can be realized, and traffic accidents can be reduced.

Drawings

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

Fig. 1 is a general structural block diagram of the present invention.

FIG. 2 is a flow chart of an ACO-OFDM modulation module in the vehicle-to-vehicle communication system.

FIG. 3 is a flow chart of an ACO-OFDM demodulation module in the vehicle-to-vehicle communication system.

Fig. 4 is an image processing flowchart.

Detailed Description

The invention provides an OCC-based vehicle-to-vehicle communication system transmitter and receiver, which adopt an automobile tail lamp LED array to transmit optical signals and a CMOS image sensor as a photoelectric detection device to receive the optical signals to realize the communication between vehicles, can transmit the driving safety information of the vehicles in real time, realize the safety early warning of the following vehicles and reduce the occurrence of traffic accidents.

As shown in fig. 1, the OCC-based vehicle-to-vehicle communication system of the present invention includes a transmitter and a receiver, and completes modulation and demodulation of vehicle driving safety information by using OFDM and image processing technologies, thereby realizing real-time information transmission between front and rear vehicles.

The transmitter comprises an automobile driving safety information acquisition module, a coding module, a modulation module, a driving circuit and a tail lamp LED array; the peripheral LEDs at the edge of the tail lamp LED array are used as positioning LEDs, and the kXkLED array at the middle part is used as a signaling LED array; positioning the LEDs to light in a particular format to determine a starting position of the signaling LED array; the modulation module modulates the data after the automobile driving safety information is coded by adopting an ACO-OFDM modulation technology and sends out the data in parallel through a signaling LED array with the specification of k multiplied by k. The LED array adopts 808nm light wave band. The transmitter performs the following steps:

step 1) the automobile driving safety information acquisition module acquires automobile driving safety information data needing to be transmitted, such as automobile steering, speed, acceleration, engine rotating speed, brake and the like, converts the automobile driving safety information data into a binary data code stream in a specified data frame format and sends the binary data code stream to the coding module.

And step 2) the coding module adopts (u, rho, gamma) Low-density Parity-check code (Low-density Parity-check, LDPC) to code the input binary data code stream, wherein u is the code length of the code, rho and gamma are respectively the column weight and the row weight of the check matrix, and the code rate of the LDPC code isAnd sending the coded data to a modulation module.

Step 3) as shown in fig. 2, the modulation module performs ACO-OFDM modulation on the encoded data, and the modulation process is as follows:

(1) performing serial-to-parallel conversion on the encoded data, then performing M-QAM (multiple-quadrature amplitude modulation) mapping to obtain a plurality of complex numbers, and expressing the complex numbers as a complex vector X_QAM＝[X₀，X₁，...，X_N-1](ii) a N is the code length of the mapped QAM symbol, and

(2) for complex phasor X_QAMProcessing is performed so that it satisfies the Hermitian symmetric transformation. Since the ACO-OFDM only transmits information on odd carriers, and data on even carriers is 0, X is required_QAMPerforming odd carrier allocation and conjugate symmetry operation, and representing the transformed frequency domain signal as X ═ 0, X₀，0，X₁，...，0，X_N-1，0，X^* _N-1，0，X^* _N-2，...，0，X^* ₀]Denotes a complex conjugate, i.e. X ═ X₀，X₁，X₂，...，X_4N-2，X_4N-1]；

(3) IFFT-varying frequency domain signal XAnd obtaining a time domain signal x with the length of 4N ═ x₀，x₁，x₂，...，x_4N-2，x_4N-1]；

(4) Carrying out zero-value amplitude limiting operation on the time domain signal x to obtain a non-negative amplitude limiting signal x':

since the frequency domain signal X satisfies the conjugate symmetry, i.e.:

X_k＝X^* _4N-k0＜k＜2N (2)

the time domain signal x is known to be real and to satisfy the antisymmetric property, as follows;

the positive part and the negative part of the time domain signal x have antisymmetry, so that the zero value amplitude limiting process cannot cause information loss or cause odd carrier signal distortion, and only reduces the odd carrier amplitude to be half of the original amplitude;

(5) performing parallel-to-serial conversion on the obtained non-negative amplitude limiting time domain signal x ', adding a cyclic prefix in front of the non-negative amplitude limiting time domain signal x' to obtain an OFDM signal, wherein the OFDM symbol period is expanded from T before the cyclic prefix is added to T + T_g，T_gGenerally takes on a value of

(6) The OFDM signal amplitude is coded and converted into 2^tStep amplitude range, each of which is represented by the amplitude level of the OFDM signal of the on-off state table of t signaling LEDs respectively to obtain the OFDM signal after space modulation, and the signaling LED array of k × k can transmit the OFDM signal each time

One OFDM signal, k is the number of rows (columns) of the signaling LED array.

And 4) transmitting the modulated OFDM signals into a driving circuit, driving a signaling LED array with the wavelength of 808nm by the driving circuit, and transmitting the driving safety information of the vehicle to a rear vehicle.

The receiver comprises a narrow-band filtering camera, an image processing module, a demodulation module and a decoding module, demodulates and decodes the received optical signals to obtain original data information, and then sends the original data information to the automobile CPU for the automobile high-level driving auxiliary system to process and analyze. A808 nm optical filter is arranged in front of a camera lens to form a narrow-band filtering camera, so that stray light projected onto the CMOS image sensor is eliminated. The receiver performs the following steps:

step 1) sending the picture shot by the narrow-band filtering camera to an image processing module.

Step 2) as shown in fig. 4, the image processing module processes the shot image to obtain the on-off state information of the LED array, and the steps are as follows:

(1) converting an RGB (red, green and blue) picture obtained by a narrow-band filtering camera into a gray value image, and then processing the gray value image through a self-adaptive threshold algorithm to obtain a binary image;

(2) detecting the LED array in the binary image by using an edge detection algorithm; because the narrow-band filtering camera only receives light of a fixed wave band, only light spots and light spots exist in the binary image, the edge of the LED array cannot be judged, and the initial position of the signaling LED array can be determined by lighting and positioning the LEDs in a specific format; after the tail lamp LED array is detected, the tail lamp LED array area is divided from the binary image for processing;

(3) detecting all light spots in the LED array area of the tail lamp in the step (2); adopting a DOH (dominant of Hessian) light spot detection algorithm, quickly detecting the light spot by searching the maximum value in a Hessian determinant matrix of the image, and obtaining the area and position information of the light spot;

after all light spots in the LED array area of the tail lamp are detected, non-LED light spots are required to be removed, noise interference is reduced, and the area of the detected light spots is required to be processed due to the fact that the pixel area occupied by a single LED is different along with the distance change between vehicles; removing three maximum areas and three minimum areas in the detected light spots, and taking the average value S of the remaining light spot areas_avg(ii) a Let m lightThe spot area of the spot is S_mTraversing all the light spots according to a formula (4), and judging whether each light spot is a tail lamp LED:

wherein, the error area P represents the set allowable calculation_LED，m1 means that the mth light spot is a tail light LED, and conversely, the mth light spot is a noise light spot;

in the outermost positioning LED light spots of the tail lamp LED array, the coordinates of the light spots at the upper left corner, the upper right corner and the lower left corner are respectively expressed as (x)_ulc,y_ulc)、(x_urc,y_urc)、(x_llc,y_ullc) Calculating the average value d of the interval between the signaling LED light spots according to the coordinate information of the three positioning LED light spots_avg：

Wherein k is the number of rows (columns) of the signaling LED array;

let i denote the row number of the signaling LED, j denote the column number of the signaling LED, and 1 is equal to or more than i, j is equal to or more than k, and k is the row (column) number of the signaling LED array; according to the positions of the LED light spots and the average value d of the intervals between the LED light spots_avgThe center position (x) of each signaling LED is estimated_i，y_j) And judging the on-off state of each signaling LED according to the formula (6):

wherein (x)₁，y₁) The estimated center point of the 1 st row and 1 st column signaling LED is obtained; for the set error unit allowed for calculation, S_LED，ijIf the signal is 1, the state of the LED (i, j) is on, which represents "1", otherwise, the signal is off, which represents "0", so that the information of "0" and "1" carried by each signaling LED in the signaling LED array can be obtained, and a signaling LED array state matrix is obtained and converted into a data stream to be sent to the demodulation module.

Step 3) as shown in fig. 3, the demodulation module demodulates the input data stream, and the steps are as follows:

(1) converting a data stream representing the on-off state of the signaling LED array into an OFDM signal;

(2) carrying out series-parallel conversion on the OFDM signals obtained in the step (1), and then removing cyclic prefixes to obtain time domain signals y;

(3) performing FFT operation on the time domain signal Y to obtain a frequency domain signal Y, and respectively representing the information of the frequency domain signal Y on the odd carrier and the even carrier as Y_oddAnd Y_evenAnd then:

(4) extracting information Y on frequency domain signal Y odd carrier_oddObtaining the original complex signal Y_QAM：

Y_QAM＝2Y_odd(2k+1)，k＝0，...，N-1 (8)

(5) For original complex signal Y_QAMPerforming M-QAM inverse mapping to recover the data coded by the coding module, and sending the recovered coded data into a decoding module after parallel-to-serial conversion;

and 4) carrying out forward error correction on the demodulated data by a decoding module, decoding to obtain the driving safety information of the front vehicle, and sending the obtained driving safety information to a vehicle CPU (Central processing Unit) for processing and analysis by a vehicle high-level driving auxiliary system.