Multi-user retro-reflection light sensing integration method and system

Abstract

The invention relates to the technical field of wireless optical communication, particularly discloses a multi-user retro-reflection light sensing integration method and system, and aims to solve the problem that retro-reflection light sensing integration in a multi-user scene is not realized yet, a transceiver is utilized to modulate a multi-user input bit to generate a fusion signal, and a light source is driven to emit a light signal; when the user receiver demodulates and recovers the communication bit, the optical signal is retroreflected and recovered to the transmitter; and the transceiver detects the superposed retroreflection signal, performs joint sensing with the transmitted signal, and estimates the distance from each user to the transceiver by adopting a cross-correlation calculation and interference elimination technology. According to the method and the system, a multi-user scene-oriented retroreflection light sensing integrated function is realized, communication and sensing services are simultaneously provided for a plurality of users by utilizing wireless light transmission, and the method and the system have a wide application prospect in the field of wireless light communication.

Description

Technical Field

[0001] This invention relates to the field of wireless optical communication technology, and in particular to a multi-user retroreflective optical sensing integrated method and system. Background Technology

[0002] Synchrotron-sensing integration is a research hotspot in 6G mobile communication technology, aiming to build a communication and sensing network using a single infrastructure to achieve deep reuse of communication and sensing services. Radar systems and communication systems share many similarities in hardware architecture and signal processing, making their integration possible. Simultaneously, given the limited wireless spectrum resources, synchrotron-sensing integration can achieve spectrum sharing between sensing and communication, improving spectrum utilization. Compared to traditional RF synchrotron-sensing systems, wireless optical synchrotron-sensing systems have inherent advantages such as large communication capacity and high sensing accuracy, making them a current research hotspot in the field of wireless optical communication. In retroreflective optical synchrotron-sensing integration, researchers have proposed a system scheme based on Orthogonal Frequency Division Multiplexing-Maximum Length Sequence (OFDM-MLS) waveforms. This system designs a flexible synchrotron-sensing fusion waveform that embeds the time-domain OFDM signal into the MLS signal. By dynamically adjusting the power distribution ratio between the MLS and OFDM signals, a flexible trade-off in synchrotron performance can be achieved. In addition, the researchers proposed a bidirectional transmission retroreflective optical sensing integrated system based on time-division duplex and wavelength-division duplex. This system can use time-division duplex or wavelength-division duplex transmission to eliminate the mutual interference between the uplink optical signal and the downlink retroreflective optical signal, thereby effectively realizing bidirectional transmission.

[0003] However, current research and reports on retroreflective optical sensing systems only consider the communication and sensing needs of single users, and in-depth research on retroreflective optical sensing systems in multi-user scenarios has not yet been conducted. Compared with single-user retroreflective optical sensing systems, multi-user retroreflective optical sensing systems not only need to consider user multiple access from a communication perspective, but also multi-user joint sensing from a sensing perspective. Therefore, it is necessary to design novel sensing fusion waveform schemes to effectively support the multiple access and joint sensing requirements of multi-user scenarios. Summary of the Invention

[0004] This invention provides a multi-user retroreflective optical sensing integrated method and system, which solves the technical problem of how to provide communication and sensing services to multiple users simultaneously using wireless optical transmission.

[0005] To address the above technical problems, this invention provides a multi-user retroreflective optical sensing integrated method, comprising:

[0006] A multi-user retroreflective optical transceiver modulates the input bits of K users to obtain a transmission signal and converts it into an analog signal; after adding a DC bias to the analog signal, it drives a light source to emit a corresponding optical signal.

[0007] At each user receiver, the optical signal is detected and converted into a corresponding digital signal. After time synchronization, demodulation is performed to recover the output bits of each user.

[0008] Each user receiver will reflect the arriving optical signal back along the original path to the multi-user retroreflective optical sensing integrated transceiver;

[0009] The multi-user retroreflective optical sensing integrated transceiver detects the superimposed retroreflective optical signals of K user receivers, and obtains the received signal after analog-to-digital conversion; the received signal and the transmitted signal are jointly sensed to obtain the distance from the K user receivers to the multi-user retroreflective optical sensing integrated transceiver.

[0010] Furthermore, the transmitted signal is obtained by modulating the input bits of K users, specifically as follows:

[0011] Perform bit allocation on the input bits of K users and generate two bit streams;

[0012] OFDM modulation is applied to one bitstream to generate an OFDM signal; for the other bitstream, one polynomial coefficient is selected from multiple candidate primitive polynomial coefficients to generate an MLS signal, where MLS stands for Maximum Length Sequence.

[0013] The peak-to-peak voltages of the OFDM signal and the MLS signal are allocated;

[0014] The transmitted signal is obtained by superimposing the amplitudes of the OFDM signal and the MLS signal, which have been assigned peak-to-peak voltages.

[0015] Furthermore, for another bit stream, a polynomial coefficient is selected from multiple candidate primitive polynomial coefficients to generate an MLS signal. Specifically, an index bit is used to select one of the 2N primitive polynomial coefficients corresponding to the Nth order MLS signal, and a linear feedback shift register is used to generate the corresponding MLS signal.

[0016] Furthermore, the peak-to-peak voltages of the OFDM signal and the MLS signal are allocated, specifically: given a total peak-to-peak voltage V, the peak-to-peak voltage V of the OFDM signal is allocated as follows: OFDM Peak-to-peak voltage V of MLS signal MLS Satisfy V OFDM +V MLS=V and peak-to-peak voltage distribution coefficient α= V MLS / (V OFDM +V MLS The peak-to-peak voltage distribution between OFDM and MLS signals is achieved by adjusting the peak-to-peak voltage distribution coefficient α.

[0017] Furthermore, demodulation is performed to recover the output bits of each user, specifically as follows:

[0018] The time-synchronized digital signal is subjected to CIM demodulation to recover the CIM bits. At the same time, the OFDM signal is extracted from the time-synchronized digital signal based on the MLS signal corresponding to the CIM bits for subsequent OFDM demodulation to obtain the OFDM bits. CIM demodulation is accomplished by cross-correlating the time-synchronized digital signal with multiple candidate MLS signals and finding the maximum value.

[0019] Based on the generated CIM bits and OFDM bits, the corresponding output bits are obtained by bit extraction using a bit allocation scheme corresponding to the modulation.

[0020] Furthermore, by jointly sensing the received signal and the transmitted signal, the distances from the K user receivers to the multi-user retroreflective optical sensing integrated transceiver are obtained, specifically:

[0021] The transmitted signal is upsampled so that the sampling frequency of the signal is consistent with the received signal. For the user receiver with the closest distance and the best channel conditions, cross-correlation is calculated using the upsampled transmitted and received signals, and the flight time between the multi-user retroreflective optical transceiver and the user receiver is calculated based on the position of the maximum cross-correlation value. The distance between the user transceiver and the multi-user retroreflective optical transceiver is estimated based on the flight time t1.

[0022] The received signal is subjected to interference cancellation processing for each other user, and the user distance is estimated by calculating the cross-correlation between the interference-cancelled received signal and the upsampled transmitted signal.

[0023] This invention also provides a multi-user retroreflective optical sensing integrated system, applied to the aforementioned multi-user retroreflective optical sensing integrated method. The key feature is that it includes a multi-user retroreflective optical sensing integrated transceiver and K user receivers, where K≥2. The multi-user retroreflective optical sensing integrated transceiver includes a modulation module, a transceiver digital-to-analog conversion module, a light source module, a transceiver photodetector, a transceiver analog-to-digital conversion module, and a joint sensing module. Each user receiver includes a receiver photodetector, a receiver analog-to-digital conversion module, a synchronization module, a demodulation module, and a corner cube reflector.

[0024] The modulation module is used to modulate the input bits of K users to obtain the transmitted signal; the transceiver digital-to-analog conversion module is used to convert the transmitted signal into an analog signal; the light source module is used to add a DC bias to the analog signal and drive the light source to emit the corresponding light signal.

[0025] In each user receiver, the receiver photodetector is used to detect the optical signal emitted by the light source module; the receiver analog-to-digital conversion module is used to convert the optical signal detected by the receiver photodetector into a corresponding digital signal; the synchronization module is used to synchronize the digital signal in time to obtain a synchronization signal; the demodulation module is used to demodulate the synchronization signal to obtain the corresponding output bits; the corner cube transmitter reflects the arriving optical signal back to the multi-user retroreflective optical sensing integrated transceiver along the original path.

[0026] The transceiver photodetector is used to detect the retroreflected light signals of the K user receivers after superposition; the transceiver analog-to-digital conversion module is used to perform analog-to-digital conversion on the retroreflected light signals of the K user receivers after superposition to obtain the corresponding received signals; the joint sensing module is used to perform joint sensing on the received signals and the transmitted signals to obtain the distance from the K user receivers to the multi-user retroreflected optical sensing integrated transceiver.

[0027] Preferably, the modulation module includes a bit allocation submodule, an OFDM modulation submodule, a polynomial coefficient selection submodule, an MLS generation submodule, a peak-to-peak voltage allocation submodule, and an amplitude superposition submodule. The bit allocation submodule is used to allocate input bits from K users and generate two bit streams. The OFDM modulation submodule is used to perform OFDM modulation on one bit stream to generate an OFDM signal. The polynomial coefficient selection submodule is used to select a polynomial coefficient from multiple candidate primitive polynomial coefficients for the other bit stream. The MLS generation submodule is used to generate an MLS signal from the selected polynomial coefficient in the other bit stream. The peak-to-peak voltage allocation submodule is used to allocate the peak-to-peak voltages of the OFDM signal and the MLS signal. The amplitude superposition submodule is used to superimpose the amplitudes of the OFDM signal and the MLS signal with allocated peak-to-peak voltages to obtain an OFDM-MLS-CIM transmit signal.

[0028] Preferably, the demodulation module includes a CIM demodulation submodule, an OFDM signal extraction submodule, an OFDM demodulation submodule, and a bit extraction submodule; the CIM demodulation submodule is used to perform CIM demodulation on the received signal to obtain CIM bits; the OFDM signal extraction submodule is used to extract the OFDM signal from the received signal according to the MLS signal corresponding to the CIM bits; the OFDM demodulation submodule is used to perform OFDM demodulation on the OFDM signal extracted by the OFDM signal extraction submodule to obtain OFDM bits; the bit extraction submodule is used to extract the corresponding output bits according to the generated CIM bits and OFDM bits through a bit allocation scheme corresponding to the modulation module.

[0029] Preferably, the joint sensing module includes an upsampling submodule, an interference cancellation submodule, and a cross-correlation calculation submodule. The upsampling submodule is used to upsample the transmitted signal generated by the modulation module so that the sampling frequency of the signal is consistent with the received signal. The cross-correlation calculation submodule is used to perform cross-correlation calculation on the transmitted and received signals after direct upsampling for the user receiver with the closest distance and the best channel conditions, and calculate the flight time between the multi-user retroreflective optical sensing transceiver and the user receiver based on the position of the maximum cross-correlation value. Finally, the distance between the user transceiver and the multi-user retroreflective optical sensing transceiver is estimated based on the flight time. The interference cancellation submodule is used to perform interference cancellation processing on the received signal for each other user, and then use the cross-correlation calculation between the interference-cancelled received signal and the upsampled transmitted signal to estimate the user distance.

[0030] This invention provides a multi-user retroreflective optical sensing integrated method and system. It utilizes a transceiver to modulate multi-user input bits to generate a fused signal, driving a light source to emit an optical signal. Simultaneously, the user receiver demodulates and recovers the communication bits, retroreflecting the optical signal back to the transceiver. The transceiver detects the superimposed retroreflected signal and performs joint sensing with the transmitted signal, employing cross-correlation calculation and interference cancellation techniques to estimate the distance from each user to the transceiver. Its beneficial effects are:

[0031] 1) Improved communication rate: The OFDM-MLS-CIM modulation scheme can transmit additional index bits, thereby effectively improving the communication rate of the multi-user retroreflective optical sensing integrated system.

[0032] 2) Flexible rate allocation: The multiple access scheme based on OFDM-MLS-CIM modulation can flexibly allocate OFDM bits and CIM bits to improve the performance of multi-user access.

[0033] 3) Effective joint sensing: The multi-user joint sensing scheme based on OFDM-MLS-CIM modulation can effectively support multiple users to complete the sensing process simultaneously through interference cancellation.

[0034] This invention, through the above-described method and system, realizes the integrated function of retroreflective optical sensing for multi-user scenarios, and provides communication and sensing services to multiple users simultaneously using wireless optical transmission, which has broad application prospects in the field of wireless optical communication. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a multi-user retroreflective optical sensing integrated method and system provided in an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of OFDM-MLS-CIM modulation provided in an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of OFDM-MLS-CIM demodulation provided in an embodiment of the present invention;

[0038] Figure 4 This is a schematic diagram of the multi-user joint sensing principle provided in an embodiment of the present invention;

[0039] Figure 5 This is an example diagram of CIM demodulation based on cross-correlation calculation provided in an embodiment of the present invention;

[0040] Figure 6 This is an example diagram illustrating the cross-correlation performance of OFDM-MLS-CIM signals provided in an embodiment of the present invention;

[0041] Figure 7 This is an example diagram of the cross-correlation results of joint perception between two users provided in an embodiment of the present invention. Detailed Implementation

[0042] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0043] This invention first provides a multi-user retroreflective optical sensing integrated method, which proposes an orthogonal frequency division multiplexing-maximum length sequence-codeword indexing (OFDM-MLS-CIM) modulation and demodulation technique, such as... Figure 1 As shown in the schematic diagram, the method includes:

[0044] A multi-user retroreflective optical transceiver modulates the input bits of K users with OFDM-MLS-CIM to obtain OFDM-MLS-CIM transmit signals, and performs digital-to-analog conversion (D / A) to convert them into OFDM-MLS-CIM analog signals; after adding DC bias to the OFDM-MLS-CIM analog signals, it drives a light source (such as an LED or laser) to emit corresponding optical signals;

[0045] At each user receiver, the optical signal is detected by a photodetector and a corresponding digital signal is generated by analog-to-digital conversion (A / D). After time synchronization using a synchronous training sequence, OFDM-MLS-CIM demodulation is performed to recover the output bits of each user.

[0046] Each user receiver is also equipped with a corner cube transmitter that reflects the arriving optical signal back to the multi-user retroreflective optical sensing transceiver along the original path.

[0047] The multi-user retroreflective optical sensing transceiver uses a photodetector to detect the retroreflected optical signals from K user receivers after superposition. After analog-to-digital conversion (A / D), the OFDM-MLS-CIM received signal is obtained. The OFDM-MLS-CIM received signal and the OFDM-MLS-CIM transmitted signal are jointly sensed to obtain the distance from the K user receivers to the multi-user retroreflective optical sensing transceiver.

[0048] Signal transmission occurs frame by frame with a periodic pattern, while the signals received by the user receiver are random in time. It is necessary to perform cross-correlation calculations on the user receiver using the transmission time synchronization sequence to find the peak value and achieve time synchronization of the received signal. That is, to find the start and end of each frame of signal and then effectively demodulate each frame of signal.

[0049] The modulation principle of the OFDM-MLS-CIM scheme is as follows: Figure 2 As shown. In the OFDM-MLS-CIM modulation process, the input bits of K users are first allocated to generate two bit streams. One bit stream is then OFDM modulated to generate an OFDM signal, while the other bit stream is selected from multiple candidate primitive polynomial coefficients (PPCs) to generate the subsequent MLS signal. The peak-to-peak voltages (Vpp) of the generated OFDM and MLS signals are then allocated, and the amplitudes of the two allocated signals are superimposed to obtain the OFDM-MLS-CIM transmit signal.

[0050] Bit allocation for the input bits of K users means dividing one serial bit stream into two parallel bit streams, with the rates of the two bit streams determined by the OFDM modulation rate and the CIM modulation rate, respectively.

[0051] Selecting one primitive polynomial coefficient (PPC) from multiple candidate primitives (PPCs) for the subsequent MLS signal generation from another bitstream refers to using an index bit to select one from the 2N primitive polynomial coefficients corresponding to an Nth-order MLS signal, and then using a linear feedback shift register to generate the corresponding MLS signal. Taking an 8th-order MLS signal as an example, there are 16 primitive polynomial coefficients that can generate MLS signals of the same length. Therefore, four binary 0-1 sequences can be used as index bits to select one from the 16 primitive polynomial coefficients and then using a linear feedback shift register to generate the corresponding MLS signal.

[0052] Allocating the peak-to-peak voltage (Vpp) of OFDM and MLS signals refers to, given a total peak-to-peak voltage V, the peak-to-peak voltage V of the OFDM signal... OFDM Peak-to-peak voltage V of MLS signal MLS Satisfy V OFDM +V MLS =V and peak-to-peak voltage distribution coefficient α= V MLS / (V OFDM +V MLS By adjusting the peak-to-peak voltage distribution coefficient α, flexible peak-to-peak voltage distribution between OFDM and MLS signals can be achieved.

[0053] The demodulation principle of the OFDM-MLS-CIM solution is as follows: Figure 3 As shown. In the OFDM-MLS-CIM demodulation process of each user receiver, the OFDM-MLS-CIM received signal is first CIM demodulated to recover the CIM bits. Simultaneously, the OFDM signal is extracted from the OFDM-MLS-CIM received signal based on the MLS signal corresponding to the CIM bits for subsequent OFDM demodulation, obtaining OFDM bits. Because of the correspondence between CIM bits and MLS signals, the MLS signal in the superimposed signal can be recovered. Then, based on the peak-to-peak voltage coefficient, the MLS signal in the superimposed signal can be eliminated, leaving only the OFDM signal. CIM demodulation is accomplished by cross-correlating the OFDM-MLS-CIM received signal with multiple candidate MLS signals and finding the maximum value. Different primitive polynomial coefficients produce different MLS signals. The received signal only generates the maximum cross-correlation peak with the corresponding MLS signal, thus completing CIM demodulation. Based on the generated CIM bits and OFDM bits, the corresponding output bits are obtained by bit extraction using a bit allocation scheme corresponding to OFDM-MLS-CIM modulation.

[0054] The multi-user joint sensing principle based on OFDM-MLS-CIM modulation proposed in this invention is as follows: Figure 4As shown, the OFDM-MLS-CIM transmitted signal first needs to be upsampled to ensure that the sampling frequency matches the OFDM-MLS-CIM received signal, thus facilitating subsequent cross-correlation calculations. For the user receiver with the closest distance and best channel conditions (the user receiver and the integrated transceiver can communicate with each other; the distance can be determined based on channel estimation; in this embodiment, user 1 is assumed to be the closest), cross-correlation calculations are directly performed using the upsampled OFDM-MLS-CIM transmitted and received signals. The flight time t1 (the time difference between the received and transmitted signals) between the multi-user retroreflective optical sensing integrated transceiver and the user receiver is calculated based on the position of the maximum cross-correlation value. Finally, the distance d1 = ct1 / 2 between the user transceiver and the multi-user retroreflective optical sensing integrated transceiver is estimated, where c is the speed of light in free space. For each of the other users, interference cancellation processing is first performed on the OFDM-MLS-CIM received signal. Then, the user distance is estimated by calculating the cross-correlation between the interference-cancelled OFDM-MLS-CIM received signal and the upsampled OFDM-MLS-CIM transmitted signal. Taking the k-th user as an example, interference cancellation is achieved by subtracting the signal components from user 1 to user k-1 from the OFDM-MLS-CIM received signal to obtain a signal that can be used for cross-correlation calculation and distance estimation for user k.

[0055] To achieve the aforementioned multi-user retroreflective optical sensing integration method, this invention also provides a multi-user retroreflective optical sensing integration system, as described above. Figure 1 The schematic diagram shows that the system includes a multi-user retroreflective optical sensing integrated transceiver (MU-RO-ISAC) and K user receivers, where K ≥ 2. The MU-RO-ISAC includes a modulation module, a transceiver digital-to-analog converter module, a light source module, a transceiver photodetector, a transceiver analog-to-digital converter module, and a joint sensing module. Each user receiver includes a receiver photodetector, a receiver analog-to-digital converter module, a synchronization module, a demodulation module, and a corner cube reflector.

[0056] The modulation module is used to perform OFDM-MLS-CIM modulation on the input bits of K users to obtain the OFDM-MLS-CIM transmit signal; the transceiver digital-to-analog conversion module is used to perform digital-to-analog conversion (D / A) on the OFDM-MLS-CIM transmit signal to convert it into an OFDM-MLS-CIM analog signal; the light source module is used to add DC bias to the OFDM-MLS-CIM analog signal to drive a light source (such as an LED or laser) to emit the corresponding light signal;

[0057] In each user receiver, a receiver photodetector is used to detect the optical signal emitted by the light source module; the receiver analog-to-digital converter module is used to convert the optical signal detected by the receiver photodetector into an analog-to-digital (A / D) signal to generate a corresponding digital signal; the synchronization module is used to synchronize the digital signal in time to obtain a synchronization signal; the demodulation module is used to demodulate the synchronization signal using OFDM-MLS-CIM to obtain the corresponding output bits; and the corner cube transmitter reflects the arriving optical signal back to the multi-user retroreflective optical sensing integrated transceiver along the original path.

[0058] The transceiver photodetector is used to detect the retroreflected light signals from the K user receivers after superposition; the transceiver analog-to-digital conversion module is used to perform analog-to-digital conversion on the retroreflected light signals from the K user receivers after superposition to obtain the corresponding OFDM-MLS-CIM received signals; the joint sensing module is used to perform joint sensing on the OFDM-MLS-CIM received signals and OFDM-MLS-CIM transmitted signals to obtain the distance from the K user receivers to the multi-user retroreflected optical sensing integrated transceiver.

[0059] refer to Figure 2 The modulation principle diagram shown includes a bit allocation submodule, an OFDM modulation submodule, a polynomial coefficient selection submodule, an MLS generation submodule, a peak-to-peak voltage (Vpp) allocation submodule, and an amplitude superposition submodule. The bit allocation submodule allocates the input bits of K users and generates two bit streams; the OFDM modulation submodule modulates one bit stream using OFDM to generate an OFDM signal; the polynomial coefficient selection submodule selects a polynomial coefficient from multiple candidate primitive polynomial coefficients (PPCs) for the other bit stream; the MLS generation submodule generates an MLS signal from the selected polynomial coefficient; the peak-to-peak voltage (Vpp) allocation submodule allocates the peak-to-peak voltage (Vpp) of the OFDM and MLS signals; and the amplitude superposition submodule superimposes the amplitudes of the allocated peak-to-peak voltage OFDM and MLS signals to obtain the OFDM-MLS-CIM transmit signal.

[0060] refer to Figure 3The demodulation principle diagram shown includes a CIM demodulation submodule, an OFDM signal extraction submodule, an OFDM demodulation submodule, and a bit extraction submodule. The CIM demodulation submodule performs CIM demodulation on the OFDM-MLS-CIM received signal to obtain CIM bits. The OFDM signal extraction submodule extracts the OFDM signal from the OFDM-MLS-CIM received signal based on the MLS signal corresponding to the CIM bits. The OFDM demodulation submodule performs OFDM demodulation on the OFDM signal extracted by the OFDM signal extraction submodule to obtain OFDM bits. The bit extraction submodule extracts the corresponding output bits based on the generated CIM bits and OFDM bits, using a bit allocation scheme corresponding to the modulation module.

[0061] refer to Figure 4 The diagram shown illustrates the principle of multi-user joint sensing. The joint sensing module includes an upsampling submodule, an interference cancellation submodule, and a cross-correlation calculation submodule. The upsampling submodule upsamples the OFDM-MLS-CIM transmitted signal generated by the modulation module, ensuring that the sampling frequency matches the OFDM-MLS-CIM received signal. The cross-correlation calculation submodule performs cross-correlation calculations directly on the upsampled OFDM-MLS-CIM transmitted and received signals for the nearest user receiver (assuming it is user 1) with the best channel conditions. Based on the location of the maximum cross-correlation value, it calculates the flight time t1 between the multi-user retroreflective optical sensing transceiver and the user receiver. Finally, it estimates the distance d1 = ct1 / 2 between the user transceiver and the multi-user retroreflective optical sensing transceiver, where c is the speed of light in free space. The interference cancellation submodule is used to perform interference cancellation processing on the OFDM-MLS-CIM received signal for each other user, and then use the cross-correlation between the interference-cancelled OFDM-MLS-CIM received signal and the upsampled OFDM-MLS-CIM transmitted signal to estimate the user distance.

[0062] Figure 5 A schematic diagram of CIM demodulation based on cross-correlation calculation is shown. It can be seen that for the three code indices 3, 7, and 11, when the selected code index matches the code index used in the OFDM-MLS-CIM signal, a cross-correlation coefficient peak of approximately 3.5 can be observed for each code index. In contrast, when the selected code index does not match the code index used in the OFDM-MLS-CIM signal, the cross-correlation coefficient stabilizes at around 1.6.

[0063] Figure 6The cross-correlation performance of OFDM-MLS-CIM signals is demonstrated. It can be seen that when the Vpp allocation coefficient α is 0 (i.e., a pure OFDM signal), the peak value of the cross-correlation curve of the OFDM-MLS-CIM signal is approximately 105; while when the Vpp allocation coefficient increases to 0.1 and 0.3, the peak value increases to 146 and 275, respectively. Since a higher peak value indicates better cross-correlation performance, in a two-user retroreflective optical sensing integrated system, the OFDM-MLS-CIM signal with a larger Vpp allocation coefficient is more advantageous for sensing. However, as the Vpp allocation coefficient in OFDM-MLS-CIM increases, the Vpp allocated to OFDM decreases, leading to a decline in communication performance. Therefore, a flexible trade-off in sensing performance can be achieved by adjusting the Vpp allocation coefficient.

[0064] Figure 7 The cross-correlation performance of joint sensing for two users is demonstrated. It can be observed that without interference cancellation (IC), the cross-correlation curve has only one peak, which can be used to estimate the flight time of user 1 (i.e., the near user); however, due to strong interference from user 1 (whose channel conditions are far superior to user 2's), the peak corresponding to user 2 (i.e., the far user) is not visible in the cross-correlation curve. Therefore, interference cancellation is needed here to achieve successful joint sensing for multiple users. Figure 7 As shown, after interference cancellation, the original peak corresponding to user 1 in the cross-correlation curve was removed, and a new peak appeared, which can be used to estimate the flight time of user 2. Figure 7 The feasibility of using interference cancellation to efficiently achieve multi-user joint sensing in an integrated retroreflective optical sensing system was verified.

[0065] It should be noted that the various processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved. This embodiment does not impose any limitations on these steps.

[0066] The embodiments described in this invention can be implemented in computing systems that include backend components (e.g., as a data server), or computing systems that include middleware components (e.g., an application server), or computing systems that include frontend components (e.g., a user computer with a graphical user interface or web browser through which a user can interact with the implementations of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., a communication network). Examples of communication networks include local area networks (LANs), wide area networks (WANs), blockchain networks, and the Internet.

[0067] Computer programs for implementing the methods and systems of the present invention may be written in any combination of one or more programming languages ​​and stored in a computer-readable storage medium. These computer programs may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus, such that when executed by the processor, the computer programs cause the functions / operations specified in the flowcharts and / or block diagrams to be performed. The computer programs may be executed entirely on a machine, partially on a machine, or as a standalone software package, partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0068] Computer-readable storage media can be tangible media that may contain or store computer programs for use by or in conjunction with an instruction execution system, apparatus, or device. Computer-readable storage media can be, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. Alternatively, computer-readable storage media can be machine-readable signal media. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, optical disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0069] In summary, this invention proposes a multi-user retroreflective optical sensing integrated method and system. It proposes a novel sensing fusion waveform (OFDM-MLS-CIM) to complete the design of a multiple access and joint sensing scheme in multi-user scenarios. The transceiver modulates the input bits of multiple users to generate a fused signal, driving the light source to emit an optical signal. The user receiver demodulates and recovers the communication bits while retroreflecting the optical signal back to the transceiver. The transceiver detects the superimposed retroreflected signal and performs joint sensing with the transmitted signal, employing cross-correlation calculation and interference cancellation techniques to estimate the distance from each user to the transceiver. Its beneficial effects are:

[0070] 1) Improved communication rate: The OFDM-MLS-CIM modulation scheme can transmit additional index bits, thereby effectively improving the communication rate of the multi-user retroreflective optical sensing integrated system.

[0071] 2) Flexible rate allocation: The multiple access scheme based on OFDM-MLS-CIM modulation can flexibly allocate OFDM bits and CIM bits to improve the performance of multi-user access.

[0072] 3) Effective joint sensing: The multi-user joint sensing scheme based on OFDM-MLS-CIM modulation can effectively support multiple users to complete the sensing process simultaneously through interference cancellation.

[0073] This invention, through the above-described method and system, realizes the integrated function of retroreflective optical sensing for multi-user scenarios, and provides communication and sensing services to multiple users simultaneously using wireless optical transmission, which has broad application prospects in the field of wireless optical communication.

[0074] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A multi-user retroreflective optical sensing integrated method, characterized in that, include: A multi-user retroreflective optical transceiver modulates the input bits of K users to obtain a transmission signal and converts it into an analog signal; after adding a DC bias to the analog signal, it drives a light source to emit a corresponding optical signal. At each user receiver, the optical signal is detected and converted into a corresponding digital signal. After time synchronization, demodulation is performed to recover the output bits of each user. Each user receiver will reflect the arriving optical signal back along the original path to the multi-user retroreflective optical sensing integrated transceiver; The multi-user retroreflective optical sensing integrated transceiver detects the superimposed retroreflective optical signals of K user receivers, and obtains the received signal after analog-to-digital conversion; the received signal and the transmitted signal are jointly sensed to obtain the distance from the K user receivers to the multi-user retroreflective optical sensing integrated transceiver.

2. The multi-user retroreflective optical sensing integrated method according to claim 1, characterized in that, The transmitted signal is obtained by modulating the input bits of K users, specifically as follows: Perform bit allocation on the input bits of K users and generate two bit streams; OFDM modulation is applied to one bitstream to generate an OFDM signal; for the other bitstream, one polynomial coefficient is selected from multiple candidate primitive polynomial coefficients to generate an MLS signal, where MLS stands for Maximum Length Sequence. The peak-to-peak voltages of the OFDM signal and the MLS signal are allocated; The transmitted signal is obtained by superimposing the amplitudes of the OFDM signal and the MLS signal, which have been assigned peak-to-peak voltages.

3. The multi-user retroreflective optical sensing integrated method according to claim 2, characterized in that, For another bit stream, a polynomial coefficient is selected from multiple candidate primitive polynomial coefficients to generate an MLS signal. Specifically, an index bit is used to select one of the 2N primitive polynomial coefficients corresponding to the Nth order MLS signal, and a linear feedback shift register is used to generate the corresponding MLS signal.

4. The multi-user retroreflective optical sensing integrated method according to claim 2, characterized in that, The peak-to-peak voltages of the OFDM signal and the MLS signal are allocated as follows: given a total peak-to-peak voltage V, the peak-to-peak voltage V of the OFDM signal is... OFDM Peak-to-peak voltage V of MLS signal MLS Satisfy V OFDM +V MLS =V and peak-to-peak voltage distribution coefficient α= V MLS / (V OFDM +V MLS The peak-to-peak voltage distribution between OFDM and MLS signals is achieved by adjusting the peak-to-peak voltage distribution coefficient α.

5. The multi-user retroreflective optical sensing integrated method according to claim 4, characterized in that, Demodulation is performed to recover the output bits of each user, specifically as follows: The time-synchronized digital signal is subjected to CIM demodulation to recover the CIM bits. At the same time, the OFDM signal is extracted from the time-synchronized digital signal based on the MLS signal corresponding to the CIM bits for subsequent OFDM demodulation to obtain the OFDM bits. CIM demodulation is accomplished by cross-correlating the time-synchronized digital signal with multiple candidate MLS signals and finding the maximum value. Based on the generated CIM bits and OFDM bits, the corresponding output bits are obtained by bit extraction using a bit allocation scheme corresponding to the modulation.

6. The multi-user retroreflective optical sensing integrated method according to claim 2, characterized in that, By jointly sensing the received signal and the transmitted signal, the distances from the K user receivers to the multi-user retroreflective optical sensing integrated transceiver are obtained, specifically: The transmitted signal is upsampled so that the sampling frequency of the signal is consistent with that of the received signal. For the user receiver with the closest distance and the best channel conditions, cross-correlation calculation is performed using the upsampled transmitted and received signals, and the flight time between the multi-user retroreflective optical transceiver and the user receiver is calculated based on the position of the maximum cross-correlation value. Based on the flight time t1, the distance between the user transceiver and the multi-user retroreflective optical sensor transceiver was estimated. The received signal is subjected to interference cancellation processing for each other user, and the user distance is estimated by calculating the cross-correlation between the interference-cancelled received signal and the upsampled transmitted signal.

7. A multi-user retroreflective optical sensing integrated system, applied to the multi-user retroreflective optical sensing integrated method according to any one of claims 1 to 6, characterized in that, It includes a multi-user retroreflective optical sensing integrated transceiver and K user receivers, where K≥2. The multi-user retroreflective optical sensing integrated transceiver includes a modulation module, a transceiver digital-to-analog converter module, a light source module, a transceiver photodetector, a transceiver analog-to-digital converter module, and a joint sensing module. Each user receiver includes a receiver photodetector, a receiver analog-to-digital converter module, a synchronization module, a demodulation module, and a corner cube reflector. The modulation module is used to modulate the input bits of K users to obtain the transmitted signal; the transceiver digital-to-analog conversion module is used to convert the transmitted signal into an analog signal; the light source module is used to add a DC bias to the analog signal and drive the light source to emit the corresponding light signal. In each user receiver, the receiver photodetector is used to detect the optical signal emitted by the light source module; the receiver analog-to-digital conversion module is used to convert the optical signal detected by the receiver photodetector into a corresponding digital signal; the synchronization module is used to synchronize the digital signal in time to obtain a synchronization signal; the demodulation module is used to demodulate the synchronization signal to obtain the corresponding output bits; the corner cube transmitter reflects the arriving optical signal back to the multi-user retroreflective optical sensing integrated transceiver along the original path. The transceiver photodetector is used to detect the retroreflected light signals of the K user receivers after superposition; the transceiver analog-to-digital conversion module is used to perform analog-to-digital conversion on the retroreflected light signals of the K user receivers after superposition to obtain the corresponding received signals; the joint sensing module is used to perform joint sensing on the received signals and the transmitted signals to obtain the distance from the K user receivers to the multi-user retroreflected optical sensing integrated transceiver.

8. A multi-user retroreflective optical sensing integrated system according to claim 7, characterized in that: The modulation module includes a bit allocation submodule, an OFDM modulation submodule, a polynomial coefficient selection submodule, an MLS generation submodule, a peak-to-peak voltage allocation submodule, and an amplitude superposition submodule; the bit allocation submodule is used to allocate the input bits of K users and generate two bit streams. The OFDM modulation submodule is used to perform OFDM modulation on one bitstream to generate an OFDM signal; the polynomial coefficient selection submodule is used to select one polynomial coefficient from multiple candidate primitive polynomial coefficients for another bitstream; the MLS generation submodule is used to generate an MLS signal from the other bitstream with the selected polynomial coefficient; the peak-to-peak voltage allocation submodule is used to allocate the peak-to-peak voltages of the OFDM signal and the MLS signal; the amplitude superposition submodule is used to superimpose the amplitudes of the OFDM signal and the MLS signal with allocated peak-to-peak voltages to obtain the OFDM-MLS-CIM transmit signal.

9. A multi-user retroreflective optical sensing integrated system according to claim 7, characterized in that: The demodulation module includes a CIM demodulation submodule, an OFDM signal extraction submodule, an OFDM demodulation submodule, and a bit extraction submodule; the CIM demodulation submodule is used to perform CIM demodulation on the received signal to obtain CIM bits; the OFDM signal extraction submodule is used to extract the OFDM signal from the received signal based on the MLS signal corresponding to the CIM bits; The OFDM demodulation submodule is used to perform OFDM demodulation on the OFDM signal extracted by the OFDM signal extraction submodule to obtain OFDM bits; the bit extraction submodule is used to extract the corresponding output bits according to the generated CIM bits and OFDM bits through a bit allocation scheme corresponding to the modulation module.

10. A multi-user retroreflective optical sensing integrated system according to claim 9, characterized in that: The joint sensing module includes an upsampling submodule, an interference cancellation submodule, and a cross-correlation calculation submodule; the upsampling submodule is used to upsample the transmitted signal generated by the modulation module so that the sampling frequency of the signal is consistent with the received signal; The cross-correlation calculation submodule is used to perform cross-correlation calculation on the directly upsampled transmit and receive signals of the user receiver with the closest distance and the best channel conditions. Based on the location of the maximum cross-correlation value, it calculates the flight time between the multi-user retroreflective optical transceiver and the user receiver. Finally, based on the flight time, it estimates the distance between the user transceiver and the multi-user retroreflective optical transceiver. The interference cancellation submodule is used to perform interference cancellation processing on the received signal for each other user. Then, it uses the cross-correlation calculation between the interference-cancelled received signal and the upsampled transmit signal to estimate the user distance.

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