Visible light communication transmission method of hybrid vook and restructured hierarchical ofdm

Abstract

The application discloses a visible light communication transmission method of mixed VOOK and restructured hierarchical OFDM, which comprises the following steps: generating a time domain signal of VOOK according to a code word of VOOK; generating a time domain signal of hierarchical OFDM by layering subcarrier numbers; generating a reconstruction signal according to the time domain signal of VOOK; superimposing the time domain signal of VOOK, a frequency domain signal of hierarchical OFDM and the reconstruction signal to generate a VLC transmission signal; inputting the VLC transmission signal into an LED after digital-to-analog conversion for illumination and communication transmission; converting the received communication transmission signal into an electrical signal through a photoelectric detection device at a receiving end; and performing signal detection of VOOK and hierarchical OFDM in parallel after IFFT operation and frequency domain equalization. The application effectively improves the spectral efficiency of transmission, realizes the dual functions of efficient spectral transmission and dimming control, avoids the dependence of signal detection of hierarchical OFDM on the dimming level of VOOK, has higher spectral efficiency, and effectively reduces the receiving complexity and processing time delay.

Description

Technical Field

[0001] This invention relates to a visible light communication transmission method that combines hybrid VOOK and reconstructed layered OFDM, belonging to the field of visible light communication technology. Background Technology

[0002] Light-emitting diodes (LEDs), with their advantages of high luminous efficiency and long lifespan, have gradually replaced traditional light sources such as incandescent lamps, becoming the mainstream choice for lighting today. Given the current shortage of radio frequency (RF) communication spectrum resources, visible light communication (VLC), which uses the light emitted by LEDs as a medium for information transmission, has opened up new spectrum for wireless communication and is currently a research hotspot.

[0003] Currently, the spectral efficiency of the VOOK modulation method recommended by the IEEE 802.15.7 standard for VLC is limited to 1 bit / s / Hz, which cannot meet the requirements of high-speed transmission. OFDM modulation technology is the mainstream choice for realizing high-speed VLC. Although there are currently spectrally efficient and power-efficient layered OFDM methods in VLC, they suffer from high reception complexity and processing delay. In addition, most tunable methods based on traditional layered OFDM can only achieve dimming control in their dimming signals and cannot carry information transmission. Traditional layered OFDM is not directly compatible with tunable VOOK methods. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a visible light communication transmission method that combines hybrid VOOK and reconstructed layered OFDM. This method effectively improves the spectral efficiency of the transmission, realizes the dual functions of high-efficiency spectral transmission and dimming control, avoids the dependence of layered OFDM signal detection on the dimming level of VOOK, has higher spectral efficiency, and effectively reduces the complexity of reception and processing delay.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention provides a visible light communication transmission method that combines hybrid VOOK and reconstructed layered OFDM, comprising:

[0007] Generate a hierarchical OFDM symbol-time VOOK codeword based on the VOOK codeword;

[0008] Generate the time-domain signal of VOOK based on the codeword of VOOK in a layered OFDM symbol time;

[0009] The subcarrier sequence numbers are hierarchically divided, and the hierarchically divided subcarrier sequence numbers are divided into a set of subcarriers carrying information and a set of subcarriers not carrying information.

[0010] The transmitted information is loaded onto the set of subcarriers carrying the information, while the set of subcarriers without information is set to zero, thereby generating a frequency domain signal of layered OFDM;

[0011] Perform an inverse Fourier transform operation on the frequency domain signal of the layered OFDM to generate the time domain signal of the layered OFDM.

[0012] Reconstruction control symbols are generated based on the time-domain signal of VOOK, and reconstruction signals are generated based on the reconstruction control symbols;

[0013] The VLC transmission signal is generated by superimposing the VOOK time domain signal, the frequency domain signal of the layered OFDM, and the reconstructed signal. After the VLC transmission signal is converted from digital to analog, it is input to the LED for lighting and communication transmission.

[0014] The receiving end converts the received optical signal into an electrical signal through a photoelectric detection device. After performing IFFT operation and frequency domain equalization, it performs VOOK and layered OFDM signal detection in parallel.

[0015] Furthermore, generating a hierarchical OFDM symbol-time VOOK codeword based on the VOOK codeword includes the following steps:

[0016] The codeword for VOOK is represented as:

[0017]

[0018] Where c is the codeword for VOOK. For the first Each bit of information sent. This is the dimming control symbol. The length occupied by information bits The length occupied by the dimming control symbol, when the dimming level is lower than hour, The value is 0 when the dimming level is higher than 0. hour, The value is 1;

[0019] Set the number of subcarriers in the hierarchical OFDM to The number of layers in a layered OFDM is set to The length of the VOOK codeword is then expressed as:

[0020]

[0021] in, The length of the VOOK codeword;

[0022] The codeword representation of a layered OFDM symbol-time VOOK is as follows:

[0023]

[0024] in, The codeword for a layered OFDM symbol-time VOOK.

[0025] Furthermore, the calculation formula for generating the time-domain signal of VOOK based on the codeword of VOOK in a layered OFDM symbol time is as follows:

[0026]

[0027] in, For the first The time-domain signal of VOOK at each sampling time. The maximum signal allowed for the LED. The minimum signal allowed for an LED. for The Each element.

[0028] Furthermore, the step of hierarchically dividing the subcarrier indices and then dividing the hierarchically divided subcarrier indices into a set of subcarriers carrying information and a set of subcarriers not carrying information includes the following steps:

[0029]

[0030] in, The subcarrier number in the hierarchical OFDM. This refers to the stratification number of the stratified OFDM. ;

[0031] The set of subcarriers carrying information is represented as:

[0032]

[0033] in, A set of subcarriers that carry information;

[0034] The set of subcarriers that do not carry information is represented as:

[0035]

[0036] in, This is the set of subcarriers that do not carry information.

[0037] Furthermore, the calculation formula for generating the frequency domain signal of the layered OFDM is as follows:

[0038]

[0039] in, For the frequency domain signal of layered OFDM, , Indicates the first Quadrature amplitude modulation symbols for each subcarrier.

[0040] Furthermore, the time-domain signal of the layered OFDM is denoted as... .

[0041] Furthermore, the step of generating reconstruction control symbols based on the time-domain signal of VOOK and generating reconstruction signals based on the reconstruction control symbols includes the following steps:

[0042]

[0043] in, To reconstruct control symbols.

[0044] The reconstructed signal is represented as:

[0045]

[0046] in, To reconstruct the signal, This indicates the operation of finding the minimum value. express about Modulo operation.

[0047] Furthermore, the calculation formula for superimposing the VOOK time-domain signal, the layered OFDM time-domain signal, and the reconstructed signal to generate the VLC transmission signal is as follows:

[0048]

[0049] in, Transmit signals for VLC.

[0050] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0051] 1. Compared with the simple VOOK method, this method applies OFDM modulation technology, which enables layered OFDM and VOOK signals to carry data transmission together. The spectral efficiency is no longer limited to 1 bit / s / Hz, effectively improving the spectral efficiency of transmission. This efficiency increases with the number of layers of layered OFDM. At the same time, it maintains the advantages of VOOK linear dimming control, realizing the dual functions of efficient spectral transmission and dimming control.

[0052] 2. Compared with other existing dimmable methods, the time-domain signal of VOOK falls on the set of subcarriers that do not carry information, which will not interfere with the information transmission of the reconstructed layered OFDM, thus avoiding the dependence of the signal detection of layered OFDM on the dimming level of VOOK.

[0053] 3. Compared with traditional layered OFDM, this method generates a reconstructed signal based on the time-domain signal of VOOK, which does not interfere with the information transmission of the reconstructed layered OFDM. It can ensure that the hybrid modulation signal operates within the linear range of the LED and is compatible with the VOOK dimming control method recommended by the VLC standard IEEE 802.15.7. At the same time, it has better bit error rate (BER) performance in the nonlinear range of the LED. More importantly, in this method, VOOK and reconstructed layered OFDM can complete signal detection in parallel, and the receiver does not need to use the serial interference cancellation method of traditional layered OFDM, effectively reducing the receiving complexity and processing delay. Attached Figure Description

[0054] Figure 1 This is a block diagram of the transmitting end structure of a visible light communication transmission method that combines hybrid VOOK and reconstructed layered OFDM, provided in an embodiment of the present invention.

[0055] Figure 2 This is a block diagram of the receiver structure of a visible light communication transmission method that combines hybrid VOOK and reconstructed layered OFDM, provided in an embodiment of the present invention.

[0056] Figure 3 This invention provides the dimming performance of a visible light communication transmission method that combines hybrid VOOK and reconstructed layered OFDM, as described in an embodiment of the present invention.

[0057] Figure 4 Under the finite linear dynamic range of LEDs, the BER performance of a hybrid VOOK and reconstructed hierarchical OFDM visible light communication transmission method varies with scaling factor. The changing trend.

[0058] Figure 5 This refers to the spectral efficiency of a visible light communication transmission method that combines hybrid VOOK and reconstructed layered OFDM, as provided in an embodiment of the present invention. Detailed Implementation

[0059] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0060] Example 1:

[0061] Please see Figure 1-2This embodiment discloses a visible light communication transmission method that combines hybrid VOOK and reconstructed layered OFDM. The invention will be further described in detail below through specific implementation schemes:

[0062] S1: Generate a layered OFDM symbol-time VOOK codeword based on the VOOK codeword;

[0063] The codeword for VOOK is generated by inputting information bits and dimming control symbols. The codeword for VOOK is then represented as follows:

[0064]

[0065] Where c is the codeword for VOOK. For the first Each bit of information sent. This is the dimming control symbol. The length occupied by information bits The length occupied by the dimming control symbol, when the dimming level is lower than hour, The value is 0 when the dimming level is higher than 0. hour, The value is 1;

[0066] Set the number of subcarriers in the hierarchical OFDM to The number of layers in a layered OFDM is set to The length of the VOOK codeword is then expressed as:

[0067]

[0068] in, The length of the VOOK codeword;

[0069] The codeword representation of a layered OFDM symbol-time VOOK is as follows:

[0070]

[0071] in, The codeword for a layered OFDM symbol-time VOOK.

[0072] S2: Generate a time-domain signal superimposed on the VOOK of the layered OFDM based on the codeword of the VOOK of a layered OFDM symbol time;

[0073] The specific calculation formula is as follows:

[0074]

[0075] in, For the first The time-domain signal of VOOK at each sampling time. The maximum signal allowed for the LED. The minimum signal allowed for an LED. for The Each element.

[0076] S3: Hierarchically divide the subcarrier indices into a set of subcarriers carrying information and a set of subcarriers not carrying information, including the following steps:

[0077] S31: Layering is performed based on subcarrier sequence numbers, and the specific calculation formula is as follows:

[0078]

[0079] in, The subcarrier number in the hierarchical OFDM. If the stratification number is the stratification number of the stratified OFDM, then... The layer contains the first Subcarriers, ;

[0080] S32: The layered subcarrier sequence numbers are divided into a set of subcarriers carrying information and a set of subcarriers not carrying information, as follows:

[0081] The set of subcarriers carrying information is represented as:

[0082]

[0083] in, A set of subcarriers that carry information;

[0084] The set of subcarriers that do not carry information is represented as:

[0085]

[0086] in, This is the set of subcarriers that do not carry information.

[0087] The time-domain signal of VOOK falls on the set of subcarriers that do not carry information, which will not interfere with the information transmission of the reconstructed layered OFDM, thus avoiding the dependence of the signal detection of layered OFDM on the dimming level of VOOK.

[0088] It can be proven that the first Time-domain signal of VOOK at each sampling time Falling into On a set of subcarriers that do not carry information, interference with the transmission of layered OFDM signals is avoided.

[0089] The proof is as follows:

[0090] The frequency domain representation of VOOK is as follows:

[0091]

[0092] in, This is the frequency domain signal for VOOK.

[0093] according to The time-domain symmetry of VOOK, the frequency-domain signal This can be further expressed as:

[0094]

[0095] Due to the existence of the following relationship:

[0096]

[0097] therefore, It can be represented as

[0098]

[0099] Therefore, the first Time-domain signal of VOOK at each sampling time Falling into On a set of subcarriers that do not carry information.

[0100] S4: Load the transmitted information onto the set of subcarriers carrying the information, and set the value of the set of subcarriers not carrying information to zero, thereby generating a layered OFDM frequency domain signal. The specific calculation formula for generating the layered OFDM frequency domain signal is as follows:

[0101]

[0102] in, For the frequency domain signal of layered OFDM, , Indicates the first Orthogonal amplitude modulation symbols of each subcarrier, It is generated by quadrature amplitude modulation of the input bits input to the layered OFDM.

[0103] S5: Perform frequency domain operation on layered OFDM signals. The pointwise inverse fast Fourier transform (IFFT) operation generates the time-domain signal of the layered OFDM, which is denoted as... .

[0104] S6: Generate reconstruction control symbols based on the time-domain signal of VOOK, and generate reconstruction signals based on the reconstruction control symbols, including the following steps:

[0105] S61: According to the The time-domain signal of VOOK at each sampling time is used to generate and reconstruct control symbols;

[0106]

[0107] in, To reconstruct control symbols.

[0108] S62: The specific calculation formula for generating the reconstructed signal based on the reconstructed control symbols is as follows:

[0109]

[0110] in, To reconstruct the signal, This indicates the operation of finding the minimum value. express about Modulo operation.

[0111] The reconstructed signal is generated based on the time-domain signal of VOOK, which will not interfere with the information transmission of the reconstructed layered OFDM. It can ensure that the hybrid modulation signal operates within the linear range of the LED and is compatible with the VOOK dimming control method recommended by the VLC standard IEEE802.15.7. At the same time, it has better bit error rate (BER) performance in the nonlinear range of the LED.

[0112] It can be proven that the reconstructed signal The frequency domain structure has the following form:

[0113]

[0114] in, Indicates the first The reconstructed signal on each subcarrier will not interfere with the information symbols of the layered OFDM. The principle of the proof is the same as the proof above. Time-domain signal of VOOK at each sampling time Falling into The principle is the same for a set of subcarriers that do not carry information.

[0115] S7: The VLC transmission signal is generated by superimposing the time-domain signal of VOOK, the time-domain signal of layered OFDM, and the reconstructed signal. This signal is then converted from parallel to serial, and after digital-to-analog conversion, it is input to the LED for lighting and communication transmission. The specific formula for superimposing the VLC transmission signal of VOOK, the frequency-domain signal of layered OFDM, and the reconstructed signal is as follows:

[0116]

[0117] in, Transmit signals for VLC.

[0118] S8: The receiving end converts the received optical signal into an electrical signal through a photoelectric detection device, further performs serial-to-parallel conversion on the electrical signal, and executes... Point FFT operation and frequency domain equalization are performed because the transmitted information of layered OFDM is not affected by VOOK and reconstructed signals, allowing direct symbol decision for orthogonal amplitude modulation of layered OFDM. Simultaneously, the frequency-equalized signal can be used... Pointed IFFT transform generates a time-domain signal, and bit decision of VOOK is performed, thereby realizing the parallel detection of VOOK and layered OFDM signals.

[0119] Compared to simply using the VOOK method, this method applies OFDM modulation technology, allowing layered OFDM and VOOK signals to jointly carry data transmission. The spectral efficiency is no longer limited to 1 bit / s / Hz, effectively improving the transmission spectral efficiency, which increases with the number of layers in the layered OFDM. At the same time, it maintains the advantages of VOOK linear dimming control, achieving the dual functions of efficient spectral transmission and dimming control. More importantly, in this method, VOOK and reconstructed layered OFDM can complete signal detection in parallel, eliminating the need for the serial interference cancellation method of traditional layered OFDM at the receiver, effectively reducing reception complexity and processing delay.

[0120] Example 2:

[0121] Please see Figure 3 This invention discloses the dimming performance of a visible light communication transmission method that combines hybrid VOOK and reconstructed layered OFDM. Figure 3 The horizontal axis represents the data duty cycle of VOOK, and the vertical axis represents the dimming level, with different scaling factors in the reconstruction of layered OFDM. As can be seen, in the range of dimming levels less than and greater than 50%, the dimming level of the method of the present invention changes linearly with the data duty cycle, thus maintaining the advantage of VOOK linear dimming control.

[0122] Please see Figure 4 This invention discloses a visible light communication transmission method that combines hybrid VOOK and reconstructed hierarchical OFDM, and its BER performance as a scaling factor within the finite linear dynamic range of LEDs. The changing trend. According to... Figure 4 The performance of reconstructed hierarchical OFDM as a function of scaling factor is obtained. As the scaling factor increases, BER performance initially improves, then gradually deteriorates. This is because... In the range of smaller values, nonlinear distortion is the main factor affecting transmission performance, while as the scaling factor increases... As the scaling factor increases, the degree of nonlinear distortion gradually decreases, thus improving transmission performance. However, as the scaling factor increases... As the number of cells increases further, the effective transmission power of the time-domain signal in layered OFDM gradually decreases, thus the BER performance gradually deteriorates. The BER of VOOK decreases with... The increase gradually decreases. Furthermore, with the same number of layers, the method of this invention exhibits superior BER performance compared to conventional HLACO-OFDM.

[0123] Please see Figure 5 This invention discloses the spectral efficiency of a visible light communication transmission method that combines hybrid VOOK and reconstructed layered OFDM. According to... Figure 5 The results show that this method has higher spectral efficiency than traditional reverse polarity OFDM (RPO-OFDM) and HLACO-OFDM, thus verifying the spectral efficiency of this method.

[0124] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0125] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0126] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0127] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0128] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A visible light communication transmission method combining hybrid VOOK and reconstructed layered OFDM, characterized in that, include: Generate a hierarchical OFDM symbol-time VOOK codeword based on the VOOK codeword; Generate the time-domain signal of VOOK based on the codeword of VOOK in a layered OFDM symbol time; The subcarrier sequence numbers are hierarchically divided, and the hierarchically divided subcarrier sequence numbers are divided into a set of subcarriers carrying information and a set of subcarriers not carrying information. The transmitted information is loaded onto the set of subcarriers carrying the information, while the set of subcarriers without information is set to zero, thereby generating a frequency domain signal of layered OFDM; Perform an inverse Fourier transform operation on the frequency domain signal of the layered OFDM to generate the time domain signal of the layered OFDM. Reconstruction control symbols are generated based on the time-domain signal of VOOK, and reconstruction signals are generated based on the reconstruction control symbols; The VLC transmission signal is generated by superimposing the time domain signal of VOOK, the frequency domain signal of layered OFDM, and the reconstructed signal. After digital-to-analog conversion, the VLC transmission signal is input to the LED for lighting and communication transmission. The receiving end converts the received optical signal into an electrical signal through a photoelectric detection device. After performing IFFT operation and frequency domain equalization, it performs VOOK and layered OFDM signal detection in parallel. The time-domain signal of layered OFDM is denoted as , The number of subcarriers in a hierarchical OFDM; The process of generating reconstruction control symbols based on the time-domain signal of VOOK and generating reconstruction signals based on the reconstruction control symbols includes the following steps: ； in, To reconstruct control symbols, for The One element, For a layered OFDM symbol-time VOOK codeword; The reconstructed signal is represented as: ； in, To reconstruct the signal, This indicates the operation of finding the minimum value. express about Modulo operation.

2. The visible light communication transmission method based on hybrid VOOK and reconstructed layered OFDM according to claim 1, characterized in that, The process of generating a layered OFDM symbol-time VOOK codeword based on the VOOK codeword includes the following steps: The codeword for VOOK is represented as: ； Where c is the codeword for VOOK. For the first Each bit of information sent. This is the dimming control symbol. The length occupied by information bits The length occupied by the dimming control symbol, when the dimming level is lower than hour, The value is 0 when the dimming level is higher than 0. hour, The value is 1; Set the number of subcarriers in the hierarchical OFDM to The number of layers in a layered OFDM is set to The length of the VOOK codeword is then expressed as: ； in, The length of the VOOK codeword; The codeword representation of a layered OFDM symbol-time VOOK is as follows: ； in, The codeword for a layered OFDM symbol-time VOOK.

3. The visible light communication transmission method based on hybrid VOOK and reconstructed layered OFDM according to claim 2, characterized in that, The formula for generating the time-domain signal of VOOK based on the codeword of VOOK in a layered OFDM symbol time is as follows: ； in, For the first The time-domain signal of VOOK at each sampling time. The maximum signal allowed for the LED. The minimum signal allowed for an LED. for The Each element.

4. The visible light communication transmission method based on hybrid VOOK and reconstructed layered OFDM according to claim 3, characterized in that, The step of hierarchically dividing the subcarrier sequence numbers and then dividing the hierarchically divided subcarrier sequence numbers into a set of subcarriers carrying information and a set of subcarriers not carrying information includes the following steps: ； in, The subcarrier number in the hierarchical OFDM. This refers to the stratification number of the stratified OFDM. ; The set of subcarriers carrying information is represented as: ； in, A set of subcarriers that carry information; The set of subcarriers that do not carry information is represented as: ； in, This is the set of subcarriers that do not carry information.

5. The visible light communication transmission method based on hybrid VOOK and reconstructed layered OFDM according to claim 4, characterized in that, The formula for calculating the frequency domain signal of the layered OFDM is as follows: ； in, For the frequency domain signal of layered OFDM, , Indicates the first Quadrature amplitude modulation symbols for each subcarrier.

6. The visible light communication transmission method based on hybrid VOOK and reconstructed layered OFDM according to claim 5, characterized in that, The calculation formula for superimposing the time-domain signal of VOOK, the time-domain signal of layered OFDM, and the reconstructed signal to generate the VLC transmission signal is as follows: ； in, Transmit signals for VLC.

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