Orthogonal frequency division multiplexing (OFDM)-based visible light communication, position sensing and energy collection integrated method

Abstract

The invention provides a visible light communication, position awareness and energy collection integrated method based on OFDM, and relates to the technical field of visible light communication. The method comprises the following steps: at a sending end, performing OFDM modulation on user information to be sent to generate an OFDM signal, and sending the OFDM signal to a receiving end through a plurality of LEDs; at a receiving end, adopting a silicon photocell as a photoelectric detector to receive the OFDM signals sent by the plurality of LEDs to obtain received signals; at a receiving end, separating a direct-current component and an alternating-current component in a received signal by adopting an alternating-current and direct-current separation circuit, and performing energy collection on the separated direct-current component; at a receiving end, processing the separated AC component, extracting a positioning subcarrier and a communication subcarrier, performing OFDM demodulation on the communication subcarrier, recovering user information, and determining the position information of the user according to the light intensity information contained in the positioning subcarrier and the position information of the LED; in this way, communication, location awareness and energy harvesting functions can be provided for users at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of visible light communication, in particular to a visible light communication, position sensing and energy collection integrated method based on OFDM. BACKGROUND

[0002] With the rapid development of mobile Internet and Internet of Things technology, the traditional radio frequency communication has been unable to meet the growing demand for communication capacity, and the next generation of mobile communication is facing the great challenge of spectrum resource shortage, high energy consumption and serious interference. Visible light communication technology as a new type of wireless communication technology relies on the existing indoor lighting equipment LED to replace the radio frequency base station to send signals, and uses a photodetector to collect optical signals, thereby realizing wireless information transmission. Since the LED light source can simultaneously load user communication data and light intensity information for realizing position sensing, a visible light communication and position sensing integrated system emerges as the times require, which has many advantages such as no spectrum authorization, high position sensing accuracy, low carbon and environmental protection. In particular, due to its unique advantage of strong electromagnetic compatibility, it can be specifically applied to electromagnetic sensitive and high security fields such as nuclear power plants, hospitals and military manufacturing industries, thereby avoiding the problems of electromagnetic interference and electromagnetic leakage caused by traditional wireless radio frequency signals. At the same time, when a silicon photovoltaic cell is used as a photodetector of the visible light system receiving end, the system can collect light energy from the LED light source and the environment while realizing signal collection, thereby having the energy collection function of no additional device and high energy conversion efficiency, making it possible to realize energy self-sustainability, which cannot be realized by the prior art. In order to realize the integration of communication, position sensing and energy collection functions, it is necessary to consider how to realize the multiplexing and separation of communication, position sensing information and energy signals, and multiple access technology has become an effective technical means to solve the above problems.

[0003] At present, some researches apply time division multiple access (TDMA) access technology, code division multiple access (CDMA) technology and orthogonal frequency division multiple access (OFDMA) technology to the visible light communication and position sensing integrated system, but there are few researches on adding energy collection function to the system. SUMMARY

[0004] In order to solve the technical problem that the prior art cannot simultaneously provide users with communication, position sensing and energy collection functions, the embodiments of the present application provide a visible light communication, position sensing and energy collection integrated method based on OFDM. The technical solution is as follows: On the one hand, a visible light communication, position sensing and energy collection integrated method based on OFDM is provided, comprising: At the sending end, the user information to be sent is OFDM modulated to generate an OFDM signal, and the OFDM signal is sent to the receiving end through a plurality of LEDs. At the receiving end, a silicon photocell is used as a photodetector to receive the OFDM signals sent by the plurality of LEDs to obtain a received signal; At the receiving end, an AC / DC separation circuit is used to separate the DC component and the AC component in the received signal, and the separated DC component is collected for energy; At the receiving end, the separated AC component is processed to extract the positioning subcarriers and the communication subcarriers, the communication subcarriers are OFDM demodulated to recover the user information, and the user's position information is determined according to the light intensity information contained in the positioning subcarriers and the position information of the LEDs.

[0005] Further, the OFDM signal generated by OFDM modulation of the user information to be sent is sent to the receiving end by the plurality of LEDs at the sending end, including: At the sending end, the plurality of LEDs are evenly distributed on the roof, and the plurality of LEDs are grouped, with at least three LEDs in each group; The user information to be sent is sequentially QAM modulated, serial / parallel converted, Hermite symmetrized, IFFTed, cyclic prefix added, and DAC converted to obtain an analog domain OFDM signal; wherein QAM modulation, serial / parallel conversion, Hermite symmetry, IFFT, and cyclic prefix addition are implemented by the FPGA of the sending end; The analog domain OFDM signal and the training sequence are sent to the receiving end by any one group of LEDs.

[0006] Further, the imaginary part of the signal after Hermite symmetry processing is 0, so that the LED only transmits real part information, and after removing the DC component at the receiving end, the number of available subcarriers is 31, of which 3 are used for positioning and the remaining 28 are used for communication.

[0007] Further, each group of LEDs modulates the same communication data for the communication subcarriers in terms of communication function to ensure the consistency of the communication signal among the plurality of LEDs; At the same time, each group of LEDs respectively assigns and modulates different positioning subcarriers for different LEDs in terms of positioning function, so that the receiving end can distinguish the LEDs through the differentiation of the positioning subcarriers, thereby completing the extraction of the positioning information.

[0008] Further, the received signal is an AC / DC mixed signal containing energy signals and information required for communication and position sensing; The received signal is represented as

[0009] wherein, represents the user The received signal, Represents the response of the photodetector. For users and the Visible light channel gain between LEDs Indicates the number of LEDs. Indicates the visible light channel response. To meet the condition that the mean is 0 and the variance is Gaussian white noise signal, Indicates the first The signal is sent to each LED.

[0010] Furthermore, the collected energy is expressed as:

[0011] in, This represents the energy collected. Indicates the fill factor. Represents the DC component. This represents the open-loop circuit voltage. Indicates thermal voltage; This represents dark saturation current.

[0012] Further, the separated AC components are processed to extract the positioning subcarrier and the communication subcarrier. The communication subcarrier is demodulated using OFDM to recover the user information. Based on the light intensity information contained in the positioning subcarrier and the LED position information, the user's position information is determined, including: The separated AC component is sampled by an ADC and converted into an OFDM signal in the digital domain, which is then sent to the FPGA at the receiving end. The FPGA at the receiving end performs group detection and symbol synchronization on the OFDM signal in the digital domain based on the training sequence sent by the transmitting end. The synchronized OFDM signal is then subjected to FFT transformation to separate the positioning subcarrier and the communication subcarrier. The light intensity information contained in the positioning subcarrier is used to characterize the attenuation characteristics of the optical channel. The communication subcarriers are demodulated using OFDM to recover user information; Based on the positioning subcarrier, the user's location information is determined using a multi-source visible light trilateration position sensing algorithm based on the received signal strength.

[0013] Furthermore, the step of determining the user's location information using a multi-source visible light trilateration position sensing algorithm based on received signal strength, according to the positioning subcarrier, includes: The user is determined from the location subcarrier. iThe light intensity information received by each LED is used to determine the distance between the user and each LED. , , And the corresponding LED's ID information; Obtain the coordinate information of the corresponding LED by using the LED's ID information; According to distance , , And the coordinate information of the corresponding LED, the user's location information is determined using a trilateration algorithm. , , ).

[0014] Furthermore, the user's location information ( , , The formula for calculating ) is:

[0015] in,( , , (), , , (), , , ( ) represents the coordinates of the three LEDs.

[0016] On the other hand, a computer-readable storage medium is provided, wherein at least one instruction is stored therein, the at least one instruction being loaded and executed by a processor to implement any of the above-described integrated method for OFDM-based visible light communication, location sensing and energy harvesting.

[0017] The beneficial effects of the technical solutions provided by the embodiments of the present invention include at least the following: 1) It can provide users with communication, location awareness and energy harvesting functions at the same time, meet the needs of multiple users, and has the characteristics of large user capacity, strong practicality, high degree of integration and low complexity.

[0018] 2) By using the above modulation scheme to modulate and demodulate the signal, it is possible to ensure that the signals between users do not interfere with each other, while realizing the multiplexing and separation of communication, location sensing information and energy signals.

[0019] 3) It can measure the distance between the user and the light source using the positioning subcarrier without affecting the communication performance, thereby realizing the integration of communication and positioning. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart of an integrated method for visible light communication, location sensing, and energy harvesting based on OFDM provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the workflow of the OFDM-based visible light communication, location sensing and energy harvesting integrated system provided in the embodiments of the present invention; Figure 3 This is a schematic diagram of the OFDM modulation and demodulation process provided in an embodiment of the present invention. Detailed Implementation

[0022] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0023] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0024] In the embodiments of this invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning. Similarly, the terms "of," "corresponding (relevant)," and "corresponding" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning.

[0025] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0026] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0027] like Figure 1 As shown, this embodiment of the invention provides an integrated method for visible light communication, location sensing, and energy harvesting based on OFDM, consisting of... Figure 2The system implementation shown can include the following steps in its processing flow: S1, at the transmitting end, the user information to be transmitted is modulated using OFDM to generate an OFDM signal, and the OFDM signal is transmitted to the receiving end through multiple LEDs; specifically, this may include the following steps: S11, at the transmitting end, multiple (e.g., 4) LEDs are evenly distributed on the roof, and the multiple LEDs are grouped together, with at least three LEDs grouped together; In this embodiment, LEDs are used to support users in simultaneously communicating, location sensing, and energy harvesting.

[0028] S12, as Figure 3 As shown, the user information to be sent is sequentially subjected to QAM modulation, serial-to-parallel conversion, Hermitian symmetry, IFFT, addition of cyclic prefix, and DAC conversion to obtain an OFDM signal in the analog domain; In this embodiment, at the transmitting end, the FPGA sequentially performs QAM modulation, serial-to-parallel conversion, Hermitian symmetric modulation, IFFT, and cyclic prefix addition operations; specifically: The user information to be sent is mapped using QAM mapping, which maps the input bit stream onto complex constellation points according to the 16QAM mapping method to obtain a set of complex frequency domain symbols, which are then converted from serial to parallel. After serial-to-parallel conversion, the signal is Hermitian symmetric, which means that the modulated symbol in the first half is copied to the second half of the frequency domain in a complex conjugate symmetric manner. After Hermitian symmetry processing, the imaginary part of the signal is 0, and the LED only transmits the real part information. A 64-point IFFT is applied to the Hermitian-symmetric data, and the imaginary part of the output data is all 0. After the IFFT operation, a cyclic prefix is ​​added to eliminate the effect of multipath propagation.

[0029] In this embodiment, the 64-point IFFT contains 64 subcarriers. After Hermitian symmetry, the last 32 subcarriers are the conjugate symmetry of the first 32 subcarriers, so only the first 32 are usable. After removing the DC component, there are 31 usable subcarriers.

[0030] In this embodiment, compared with TDMA and CDMA technologies, OFDM technology can achieve multiplexing and separation of different signals in the frequency domain by allocating different subcarriers. It has advantages such as low implementation complexity, high security, and strong anti-interference ability. At the same time, it can flexibly select communication subcarriers and positioning subcarriers, making it a relatively more effective implementation scheme.

[0031] In this embodiment, the OFDM signal after IFFT is a discrete digital signal. After being converted by DAC, it is transmitted in the form of an analog signal. After being DC biased, it drives any group of LEDs to send signals.

[0032] S13, transmit the OFDM signal and training sequence in the analog domain to the receiver via any set of LEDs.

[0033] In this embodiment, the training sequence is a set of known data used for receiver synchronization; according to the above analysis, there are 31 available subcarriers, 3 of which are selected for positioning, and the remaining 28 subcarriers are used for communication.

[0034] In this embodiment, each group of LEDs modulates the same communication data for the communication subcarrier in terms of communication function, so as to ensure the consistency of communication signals among multiple LEDs; Meanwhile, in terms of positioning, each group of LEDs is assigned and modulated with different positioning subcarriers, enabling the receiver to identify each LED light source by distinguishing the positioning subcarriers, thereby completing the extraction of positioning information.

[0035] S2, at the receiving end, a silicon photovoltaic cell is used as a photodetector to receive the OFDM signals sent by the multiple LEDs and obtain the received signal; In this embodiment, silicon photovoltaic cells are used as photodetectors to ensure the system has superior energy harvesting capabilities.

[0036] In this embodiment, the user can simultaneously receive OFDM signals from all LEDs in each group of LEDs, obtaining a received signal; the received signal is represented as...

[0037] in, express Time users The received signal, Represents the response of the photodetector. For users and the Visible light channel gain between LEDs Indicates the number of LEDs. Indicates the visible light channel response. To meet the condition that the mean is 0 and the variance is Gaussian white noise signal, Indicates the first The signal is sent to each LED.

[0038] In this embodiment, the received signal is a hybrid AC / DC signal, which includes energy signals and information required for communication and location sensing.

[0039] S3, at the receiving end, an AC / DC separation circuit is used to separate the DC and AC components in the received signal, and energy is harvested from the separated DC component; wherein, the harvested energy is expressed as:

[0040] in, This represents the energy collected. Indicates the fill factor. Represents the DC component. This represents the open-loop circuit voltage. Indicates thermal voltage; This represents dark saturation current.

[0041] S4, at the receiving end, the separated AC components are processed to extract the positioning subcarrier and the communication subcarrier. The communication subcarrier is demodulated using OFDM to recover the user information. Based on the light intensity information contained in the positioning subcarrier and the position information of the LED, the user's position information is determined. Specifically, this may include the following steps: S41, the OFDM signal received by the receiving end is an analog signal. After the separated AC component is sampled by ADC, it is converted into a digital domain OFDM signal and sent to the FPGA of the receiving end. S42, the FPGA at the receiving end performs group detection and symbol synchronization on the OFDM signal in the digital domain based on the training sequence sent by the transmitting end, and performs FFT transformation on the synchronized OFDM signal to separate the positioning subcarrier and the communication subcarrier. In this embodiment, by separating different subcarriers, on the one hand, the communication subcarrier carrying communication data is extracted to achieve high-speed data transmission, and on the other hand, the positioning subcarrier carrying positioning information is extracted to achieve position estimation, thereby realizing integrated communication and positioning functions in the same optical signal. Due to the orthogonality between subcarriers, interference from other users, channel noise, and position-aware information can be eliminated to a certain extent.

[0042] S43, OFDM demodulation of the communication subcarrier to recover user information; like Figure 3 As shown, the user information is recovered by sequentially performing ADC conversion, cyclic prefix subtraction, N-point FFT (e.g., 64-point FFT), parallel-to-serial conversion, and QAM demodulation on the communication subcarrier.

[0043] S44, Based on the positioning subcarrier, the user's location information is determined using a multi-source visible light trilateration position sensing algorithm based on received signal strength, which may specifically include the following steps: S441, determine the user's location from the first subcarrier based on the positioning subcarrier. iThe light intensity information received by each LED is used to determine the distance between the user and each LED. , , And the corresponding LED's ID information; For location sensing, it is necessary to calculate the distance between the LED light source and the user based on the received signal strength and the corresponding LED information.

[0044] In this embodiment, the light intensity information contained in the positioning subcarrier is used to characterize the attenuation characteristics of the optical channel. The receiver determines the user's location from the first... i The system receives light intensity information from three LEDs and then matches this information with a preset light propagation model to calculate the distance between the user and each LED. Through this method, this embodiment can measure the distance between the user and the light source using a positioning subcarrier without affecting the normal transmission of the communication subcarrier, thus achieving integrated communication and positioning.

[0045] In this embodiment, the ID information of the light source corresponding to different light intensities is determined by comparing the light intensity information from three LEDs.

[0046] S442, obtain the coordinate information of the corresponding LED through the LED's ID information; In this embodiment, the coordinates of the LEDs are known. The coordinate information of the corresponding LEDs is obtained through the LED ID information, which are as follows: , , (), , , (), , , ).

[0047] S443, based on distance , , And the coordinate information of the corresponding LED, the user's location information is determined using a trilateration algorithm. , , ); among which, the user's location information ( , , The formula for calculating ) is:

[0048] in,( , , (), , , (), , , ( ) represents the coordinates of the three LEDs.

[0049] In summary, the OFDM-based integrated method for visible light communication, location sensing, and energy harvesting provided by this invention has at least the following beneficial effects: 1) It can provide users with communication, location awareness and energy harvesting functions at the same time, meet the needs of multiple users, and has the characteristics of large user capacity, strong practicality, high degree of integration and low complexity.

[0050] 2) By using the above modulation scheme to modulate and demodulate the signal, it is possible to ensure that the signals between users do not interfere with each other, while realizing the multiplexing and separation of communication, location sensing information and energy signals.

[0051] 3) It can measure the distance between the user and the light source using the positioning subcarrier without affecting the communication performance, thereby realizing the integration of communication and positioning.

[0052] The above embodiments can be implemented, in whole or in part, by software, hardware (such as circuits), firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, all or part of the processes or functions described in the embodiments of the present invention are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more sets of available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium. A semiconductor medium can be a solid-state drive.

[0053] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0054] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0055] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0056] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0057] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the devices, apparatuses, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0058] In the several embodiments provided by this invention, it should be understood that the disclosed devices, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0059] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0060] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0061] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0062] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for integrating visible light communication, location sensing, and energy harvesting based on OFDM, characterized in that, The method includes: At the transmitting end, the user information to be transmitted is modulated with OFDM to generate an OFDM signal, and the OFDM signal is transmitted to the receiving end through multiple LEDs. At the receiving end, a silicon photovoltaic cell is used as a photodetector to receive the OFDM signals sent by the multiple LEDs and obtain the received signal. At the receiving end, an AC / DC separation circuit is used to separate the DC and AC components in the received signal, and energy is harvested from the separated DC component. At the receiving end, the separated AC components are processed to extract the positioning subcarrier and the communication subcarrier. The communication subcarrier is demodulated using OFDM to recover the user information. Based on the light intensity information contained in the positioning subcarrier and the position information of the LED, the user's position information is determined.

2. The integrated method for visible light communication, location sensing, and energy harvesting based on OFDM according to claim 1, characterized in that, At the transmitting end, the user information to be transmitted is modulated with OFDM to generate an OFDM signal, and the OFDM signal is transmitted to the receiving end through multiple LEDs, including: At the transmitting end, multiple LEDs are evenly distributed on the roof, and the multiple LEDs are grouped together, with at least three LEDs grouped together. The user information to be transmitted is sequentially subjected to QAM modulation, serial-to-parallel conversion, Hermitian symmetry, IFFT, addition of a cyclic prefix, and DAC conversion to obtain an OFDM signal in the analog domain; among which, QAM modulation, serial-to-parallel conversion, Hermitian symmetry, IFFT, and addition of a cyclic prefix are implemented by the FPGA at the transmitting end; The OFDM signal and training sequence in the analog domain are sent to the receiving end via any set of LEDs.

3. The integrated method for visible light communication, location sensing, and energy harvesting based on OFDM according to claim 2, characterized in that, After Hermitian symmetry processing, the imaginary part of the signal is 0, so that the LED only transmits the real part information. After removing the DC component at the receiving end, there are 31 subcarriers available. Among them, 3 subcarriers are used for positioning, and the remaining 28 subcarriers are used for communication.

4. The integrated method for visible light communication, location sensing, and energy harvesting based on OFDM according to claim 2, characterized in that, Each group of LEDs modulates the same communication data for the communication subcarrier to ensure the consistency of the communication signal among multiple LEDs; Meanwhile, in terms of positioning, each group of LEDs is assigned and modulated with different positioning subcarriers, enabling the receiver to identify each LED light source by distinguishing the positioning subcarriers, thereby completing the extraction of positioning information.

5. The integrated method for visible light communication, location sensing, and energy harvesting based on OFDM according to claim 1, characterized in that, The received signal is a hybrid AC / DC signal, containing energy signals as well as information required for communication and location sensing; The received signal is represented as in, express Time users The received signal, Represents the response of the photodetector. For users and the Visible light channel gain between LEDs Indicates the number of LEDs. Indicates the visible light channel response. To satisfy the condition that the mean is 0 and the variance is Gaussian white noise signal, Indicates the first The signal is sent to each LED.

6. The integrated method for visible light communication, location sensing, and energy harvesting based on OFDM according to claim 1, characterized in that, The collected energy is represented as: in, This represents the energy collected. Indicates the fill factor. Represents the DC component. This represents the open-loop circuit voltage. Indicates thermal voltage; This represents dark saturation current.

7. The integrated method for visible light communication, location sensing, and energy harvesting based on OFDM according to claim 1, characterized in that, The process of separating the AC components involves extracting the positioning subcarrier and the communication subcarrier, demodulating the communication subcarrier using OFDM to recover the user information, and determining the user's location information based on the light intensity information contained in the positioning subcarrier and the LED position information. The separated AC component is sampled by an ADC and converted into an OFDM signal in the digital domain, which is then sent to the FPGA at the receiving end. The FPGA at the receiving end performs group detection and symbol synchronization on the OFDM signal in the digital domain based on the training sequence sent by the transmitting end. The synchronized OFDM signal is then subjected to FFT transformation to separate the positioning subcarrier and the communication subcarrier. The light intensity information contained in the positioning subcarrier is used to characterize the attenuation characteristics of the optical channel. The communication subcarriers are demodulated using OFDM to recover user information; Based on the positioning subcarrier, the user's location information is determined using a multi-source visible light trilateration position sensing algorithm based on the received signal strength.

8. The integrated method for visible light communication, location sensing, and energy harvesting based on OFDM according to claim 7, characterized in that, The step of determining the user's location information using a multi-source visible light trilateration position sensing algorithm based on received signal strength, according to the positioning subcarrier, includes: The user is determined from the location subcarrier. i The light intensity information received by each LED is used to determine the distance between the user and each LED. , , And the corresponding LED's ID information; Obtain the coordinate information of the corresponding LED by using the LED's ID information; According to distance , , And the coordinate information of the corresponding LED, the user's location information is determined using a trilateration algorithm. , , ).

9. The integrated method for visible light communication, location sensing, and energy harvesting based on OFDM according to claim 8, characterized in that, User location information ( , , The formula for calculating ) is: in,( , , (), , , (), , , ( ) represents the coordinates of the three LEDs.

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