A spatial modulation method for visible light communication based on reflecting surface

Abstract

The embodiment of the present application provides a visible light communication spatial modulation method based on a reflecting surface, which can solve the technical problem of poor spatial modulation capability of visible light communication. The method includes: determining the activated reflection group of the reflecting surface according to the channel gain of the first optical signal emitted by the transmitter; the transmitter sends the first optical signal to the activated reflection group; the activated reflection group receives the first optical signal and sends the first optical signal carrying the first data to the receiver; the light reflected by each reflective array element can reach at most one receiving unit. According to the channel gain of the first optical signal emitted by the transmitter, the activated reflection group is determined in the reflection groups with different activation probabilities to adapt to the changing channel conditions. By setting a direct-line link obstruction, the problem of the transmission signal (first optical signal) being blocked by obstacles is overcome, and the bit error rate is reduced. In this way, the overall rate performance and the overall energy efficiency of the system are improved at the same time, thereby improving the spatial modulation capability of visible light communication.

Description

Technical Field

[0001] The present application relates to the field of communication technology, and in particular to a visible light communication spatial modulation method based on a reflecting surface. Background Art

[0002] Visible light communication (VLC) is a technology that uses visible light to transmit data. Compared with traditional radio frequency communication, VLC offers significant advantages such as high bandwidth, strong security, environmental friendliness, and non-interference.

[0003] Currently, visible light wireless communication systems consist of a transmitter and a receiver. The transmitter converts electrical signals into invisible, high-frequency, flickering light signals. The receiver receives the light signals from the transmitter and converts them back into electrical signals.

[0004] However, visible light wireless communication systems consisting solely of a transmitter and receiver cannot meet the rate requirements of certain communication scenarios. As communication environments increasingly demand more stable and efficient data transmission, this cannot meet these demands. Therefore, improving the modulation flexibility of visible light wireless communication systems has become an urgent issue. Summary of the Invention

[0005] The embodiments of the present application provide a visible light communication spatial modulation method based on a reflecting surface, which can solve the technical problem of poor spatial modulation capability of visible light communication.

[0006] To achieve the above objectives, the embodiments of the present application adopt the following technical solutions:

[0007] In a first aspect, an embodiment of the present application provides a visible light communication spatial modulation method based on a reflecting surface, which includes: determining an activated reflection group of the reflecting surface according to a channel gain of a first optical signal emitted by a transmitter; the reflecting surface includes multiple reflection groups; each reflection group includes multiple reflection array elements; the multiple reflection array elements are distributed in an N*N array, where N is a positive integer; the activated reflection group is one of the multiple reflection groups; at least two reflection groups have different activation probabilities; the transmitter sends a first optical signal to the activated reflection group; the activated reflection group receives the first optical signal and sends the first optical signal carrying first data to a receiver; the receiver includes multiple receiving units arranged in an array; the first data includes an index of the activated reflection group; the light reflected by each reflection array element can reach at most one receiving unit; wherein a direct-line link obstruction is provided between the transmitter and the receiver, so that the first optical signal emitted by the transmitter cannot be directly received by the receiver; the transmitter, the direct-line link obstruction and the receiver are located on a first axis; the reflecting surface is provided outside the first axis, and the reflecting surface is located between the transmitter and the receiver.

[0008] Based on the above description of the visible light communication spatial modulation method based on the reflecting surface provided in the embodiment of the present application, it can be known that the visible light communication spatial modulation method based on the reflecting surface includes determining the activated reflection group in the reflection groups with different activation probabilities according to the channel gain of the first light signal emitted by the transmitter to adapt to the changing channel conditions. By setting a direct-line link obstruction, the problem of the transmission signal (first light signal) being blocked by obstacles due to line of sight obstacles and device direction is overcome, and the bit error rate is reduced. By controlling the spatial modulation mode of the activated reflection group, the data rate of the activated reflection group is changed, and the data rate of the transmitter and the activated reflection group are transmitted in parallel. In this way, the overall rate performance and the overall energy efficiency of the system are improved at the same time, thereby improving the spatial modulation capability of visible light communication.

[0009] In a feasible implementation of the first aspect, when executing the step of determining the activated reflection group of the reflection surface based on the channel gain of the first optical signal emitted by the transmitter, the visible light communication spatial modulation method based on the reflection surface also includes: generating a Huffman code according to the number of reflection groups as information transmitted by the reflection surface node; based on the Huffman code, confirming the activation probability of each reflection group; the longer the codeword in the Huffman code, the smaller the activation probability.

[0010] In this way, by introducing Huffman code encoding, the rates of the transmitter and receiver are made different. When the total rate is consistent, the channel with higher channel gain is selected to enable the transmitter to transmit higher-order information.

[0011] As well, it improves the bit error rate performance and increases the channel capacity, with a gain of about 5.5dB and a BER of 1e -5 , capable of providing higher data rates.

[0012] In a feasible implementation of the first aspect, when executing the step of determining the activated reflection group of the reflection surface based on the channel gain of the first optical signal emitted by the transmitter, the visible light communication spatial modulation method based on the reflection surface also includes: confirming the activation probability of the reflection group based on the channel gain; the higher the value of the channel gain, the higher the activation probability.

[0013] In a feasible implementation manner of the first aspect, the evaluation parameter of the channel gain includes a signal-to-noise ratio; a higher value of the signal-to-noise ratio indicates a higher activation probability.

[0014] In a feasible implementation manner of the first aspect, the number of reflective array elements in the activated reflective group is an integer multiple of the number of receiving units, so that each receiving unit receives a signal.

[0015] In a feasible implementation of the first aspect, the multiple reflection groups include a first reflection group, a second reflection group, a third reflection group and a fourth reflection group; the index of the first reflection group is 0, and the activation probability is 0.5; the index of the second reflection group is 10, and the activation probability is 0.25; the index of the third reflection group is 110, and the activation probability is 0.125; the index of the fourth reflection group is 111, and the activation probability is 0.125.

[0016] In a feasible implementation of the first aspect, before the transmitter sends the first optical signal to the activated reflection group, the visible light communication spatial modulation method based on the reflection surface further includes: preprocessing the first optical signal through pulse amplitude modulation.

[0017] In a possible implementation of the first aspect, the emitter is a light emitting diode.

[0018] In a feasible implementation of the first aspect, the receiving unit is a photodetector.

[0019] In a second aspect, an embodiment of the present application provides a visible light communication spatial modulation system based on a reflecting surface, which includes: a transmitter, a reflecting surface, a direct-line link obstruction and a receiver; the transmitter sends a first optical signal to an activated reflection group; the reflecting surface includes multiple reflection groups; each reflection group includes multiple reflection array elements; the multiple reflection array elements are distributed in an N*N array, where N is a positive integer; the activated reflection group is one of the multiple reflection groups; the activated reflection group is determined by the reflecting surface according to the channel gain of the first optical signal; the activation probabilities of at least two reflection groups are different; the activated reflection group is used to receive the first optical signal and send the first optical signal carrying first data to the receiver; the receiver includes multiple receiving units arranged in an array; the first data includes the index of the activated reflection group; the light reflected by each reflection array element can reach at most one receiving unit; a direct-line link obstruction is provided between the transmitter and the receiver, so that the first optical signal emitted by the transmitter cannot be directly received by the receiver; the transmitter, the direct-line link obstruction and the receiver are located on a first axis; the reflecting surface is provided outside the first axis, and the reflecting surface is located between the transmitter and the receiver.

[0020] The visible light communication spatial modulation system based on the reflecting surface performs the method provided in the first aspect, and determines the activated reflection group in the reflection groups with different activation probabilities according to the channel gain of the first light signal emitted by the transmitter to adapt to the changing channel conditions. By setting a direct-line link obstruction, the problem of the transmission signal (first light signal) being blocked by obstacles due to line of sight obstructions and device orientation is overcome, thereby reducing the bit error rate. In this way, the overall rate performance and overall energy efficiency of the system are improved at the same time, thereby improving the visible light communication spatial modulation capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1A schematic structural diagram of a visible light communication spatial modulation system based on a reflective surface provided in an embodiment of the present application;

[0022] Figure 2 A schematic diagram of a flow chart of a visible light communication spatial modulation method based on a reflective surface provided in an embodiment of the present application;

[0023] Figure 3 A schematic structural diagram of a reflective surface in a visible light communication spatial modulation method based on a reflective surface provided in an embodiment of the present application;

[0024] Figure 4 A schematic diagram of a feasible implementation of Huffman code in a reflecting surface-based visible light communication spatial modulation method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be described below in conjunction with the accompanying drawings in the embodiments of the present invention. In the description of the embodiments of the present invention, unless otherwise specified, "multiple" refers to two or more than two. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural 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 single or multiple.

[0026] In addition, in order to facilitate the clear description of the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, words such as "first" and "second" are used to distinguish between identical or similar items with substantially the same functions and effects. Those skilled in the art will understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit differences. At the same time, in the embodiments of the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design scheme described as "exemplary" or "for example" in the embodiments of the present invention should not be interpreted as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a concrete way for easy understanding.

[0027] The principles and features of the present application are described below. The examples given are only used to explain the present application and are not used to limit the scope of the present application.

[0028] The embodiment of the present application provides a visible light communication spatial modulation method based on a reflecting surface, which is applicable to various visible light communication scenarios. According to the channel gain of the first optical signal emitted by the transmitter, the activated reflection group is determined in the reflection groups with different activation probabilities to adapt to the changing channel conditions. By setting a direct-line link obstruction, the problem of the transmission signal (first optical signal) being blocked by obstacles due to line of sight obstructions and device direction is overcome, and the bit error rate is reduced. In this way, the overall rate performance and overall energy efficiency of the system are improved at the same time, thereby improving the spatial modulation capability of visible light communication.

[0029] The embodiment of the present application provides a visible light communication spatial modulation system based on a reflecting surface, which can execute the visible light communication spatial modulation method based on a reflecting surface provided in the embodiment of the present application. Figure 1 This is a schematic diagram of the structure of a visible light communication spatial modulation system based on a reflective surface provided in an embodiment of the present application. Figure 1 As shown, in some embodiments, the reflective surface-based visible light communication spatial modulation system includes: a transmitter, a reflective surface, a direct-view link obstruction, and a receiver.

[0030] The transmitter is configured to determine an activated reflection group of a reflection surface based on a channel gain, and transmit a first optical signal to the activated reflection group. The reflection surface includes multiple reflection groups. Each reflection group includes multiple reflection array elements. The multiple reflection array elements are arranged in an N*N array, where N is a positive integer. The activated reflection group is one of the multiple reflection groups. At least two reflection groups have different activation probabilities.

[0031] The activated reflective group is configured to receive a first optical signal and transmit the first optical signal carrying first data to a receiver. The receiver includes a plurality of receiving elements arranged in an array. The first data includes an index of the activated reflective group. Light reflected by each reflective element can reach at most one receiving element.

[0032] A direct-line link obstruction is provided between the transmitter and the receiver, so that the first optical signal transmitted by the transmitter cannot be directly received by the receiver.

[0033] The transmitter, the direct-view link obstruction, and the receiver are located on a first axis. The reflective surface is arranged outside the first axis, and the reflective surface is located between the transmitter and the receiver.

[0034] Figure 2 This is a flow chart of a method for spatial modulation of visible light communication based on a reflective surface provided in an embodiment of the present application. Figure 2 As shown, in some embodiments, the visible light communication spatial modulation method based on a reflecting surface includes the following steps:

[0035] S1. Determine an activated reflection group of a reflection surface according to a channel gain of a first optical signal transmitted by a transmitter.

[0036] The transmitter converts the electrical signal into an invisible high-frequency flashing light signal. In some embodiments, the transmitter is a light-emitting diode (LED). The first light signal is a high-frequency flashing light signal.

[0037] A reflective surface, also known as a reconfigurable intelligent surface (RIS), is a passive device, meaning it only adjusts the reflection direction of the incident light without changing its amplitude. By introducing programmable reflective surfaces in wireless communication environments, signal propagation characteristics can be improved. Reflective surfaces can enhance signals and are environmentally adaptable. By adjusting the reflection characteristics in real time, reflective surfaces can adapt to different environmental conditions, optimize signal transmission quality, and enable flexible and energy-efficient deployment. Introducing reflective surface technology in visible light communication can significantly improve signal quality and stability. Communication performance can be enhanced by introducing non-line-of-sight paths and actively reshaping the optical wireless propagation environment. By adjusting parameter indices such as the refractive index and reflection angle, the reflective surface can precisely change the transmission characteristics of the reflected light signal.

[0038] In some embodiments, as Figure 1 As shown, the RIS includes multiple reflection groups. Each reflection group includes multiple reflection array elements. The multiple reflection array elements are distributed in an N*N array, where N is a positive integer.

[0039] In some embodiments, the number of reflection elements is represented by N e , which are divided equally into N g groups, each group has N e / N g Array elements, which are arranged into The secondary array of N e / N g and are integers. RIS and W RIS Indicates the length and width of the RIS node. Figure 1 and Figure 3 In one implementation, the reflective surface includes four reflective groups. Each reflective group includes 16 reflective array elements. The 16 reflective array elements are distributed in a 4*4 array.

[0040] The activated reflection group is one of the multiple reflection groups, wherein at least two reflection groups have different activation probabilities. The determination of the activation probability is described in detail below.

[0041] In some embodiments, when executing step S1, the visible light communication spatial modulation method based on a reflecting surface further includes:

[0042] S111: Generate a Huffman code according to the number of reflection groups.

[0043] In one implementation, the multiple reflection groups include a first reflection group, a second reflection group, a third reflection group, and a fourth reflection group, for a total of four reflection groups.

[0044] S112: Based on the Huffman code, confirm the activation probability of each reflection group.

[0045] Among them, the longer the codeword in the Huffman code, the smaller the activation probability.

[0046] like Figure 4 As shown, in one implementation, the multiple reflection groups include a first reflection group, a second reflection group, a third reflection group, and a fourth reflection group. The Huffman code of the first reflection group is 0, and the activation probability is 0.5. The Huffman code of the second reflection group is 10, and the activation probability is 0.25. The Huffman code of the third reflection group is 110, and the activation probability is 0.125. The Huffman code of the fourth reflection group is 111, and the activation probability is 0.125.

[0047] In another implementation, the multiple reflection groups include a first reflection group, a second reflection group, a third reflection group, a fourth reflection group, a fifth reflection group, and a sixth reflection group. The Huffman code of the first reflection group is 0, and the activation probability is 0.5. The Huffman code of the second reflection group is 10, and the activation probability is 0.25. The Huffman code of the third reflection group is 110, and the activation probability is 0.125. The Huffman code of the fourth reflection group is 1110, and the activation probability is 0.125. The Huffman code of the fifth reflection group is 11110, and the activation probability is 0.0625. The Huffman code of the sixth reflection group is 11111, and the activation probability is 0.03125.

[0048] It is understood that the above implementations are merely exemplary examples of four and six reflection groups, and do not limit the number of reflection groups. A greater number of reflection groups corresponds to an encoding method with a greater number of bits.

[0049] In this way, by introducing Huffman code encoding, the rates of the transmitter and receiver are made different. When the total rate is consistent, the channel with higher channel gain is selected to enable the transmitter to transmit higher-order information.

[0050] As well, it improves the bit error rate performance and increases the channel capacity, with a gain of about 5.5dB and a BER of 1e -5 , capable of providing higher data rates.

[0051] The following describes how to determine the activated reflection group.

[0052] In some embodiments, when executing step S1, the visible light communication spatial modulation method based on a reflecting surface further includes:

[0053] S121: Determine the reflection group activation probability according to the channel gain.

[0054] In some embodiments, the higher the value of the channel gain, the higher the activation probability.

[0055] In one implementation, the evaluation parameter of the channel gain includes a signal-to-noise ratio. The higher the signal-to-noise ratio, the higher the activation probability.

[0056] It should be understood that this application does not activate the first reflection group while the second reflection group is inactive. Instead, all reflection groups (e.g., the first, second, third, and fourth reflection groups) are activated, but with different activation probabilities. In other words, when the first optical signal reaches the reflection surface, data is transmitted along a link in a certain reflection group to the receiver with a certain probability.

[0057] For example, the channel signal-to-noise ratio of the first reflection group is 30dB, the channel signal-to-noise ratio of the second reflection group is 15dB, the channel signal-to-noise ratio of the third reflection group is 0dB, and the channel signal-to-noise ratio of the fourth reflection group is 0dB. Then, according to the channel signal-to-noise ratio, arranged from large to small, the first reflection group is assigned an activation probability of 0.5, the second reflection group is assigned an activation probability of 0.25, the third reflection group is assigned an activation probability of 0.125, and the fourth reflection group is assigned an activation probability of 0.125. At this time, the first data carried by the reflection surface, that is, the spatial modulation signal carried by the first reflection group is 0, the spatial modulation signal carried by the second reflection group is 10, the spatial modulation signal carried by the third reflection group is 110, and the spatial modulation signal carried by the fourth reflection group is 111, thereby completing the spatial modulation technology with a reflection surface.

[0058] S2, the transmitter sends a first optical signal to the activated reflection group.

[0059] A line-of-sight obstruction is provided between the transmitter and the receiver to prevent the first optical signal transmitted by the transmitter from being directly received by the receiver. The transmitter, the line-of-sight obstruction, and the receiver are located on a first axis. A reflective surface is provided outside the first axis and between the transmitter and the receiver. In this manner, the transmitter transmits the first optical signal to the activated reflective group.

[0060] In some embodiments, before performing step S2, the visible light communication spatial modulation method based on a reflecting surface further includes:

[0061] S21 , preprocessing the first optical signal through pulse amplitude modulation.

[0062] Exemplarily, the LED uses pulse amplitude modulation (M-PAM) to transmit log2(m) bits in each transmission process.

[0063] S3, activating the reflective group to receive the first optical signal, and sending the first optical signal carrying the first data to the receiver.

[0064] All array elements in the activated reflective group can reflect light to the receiver. Array elements in all other reflective groups except the activated reflective group are turned off and cannot reflect light. In some embodiments, the reflection direction of the first optical signal can be adjusted.

[0065] The first data indicates data to be transmitted by the activated reflection group. In one implementation, the first data includes an index of the activated reflection group.

[0066] In some embodiments, spatial modulation is used on the reflective surface. In this way, the active reflective group modulates its own data (i.e., first data) onto the first optical signal using spatial modulation technology, which means that the active reflective group can use the light of the transmitter to send its own data to the receiver.

[0067] Among them, spatial modulation (SM), a multi-input, multi-output (MIMO) digital modulation method, has attracted significant attention for improving the spectral efficiency of visible light wireless communications. In a multi-transmitter visible light wireless communication system, spatial modulation activates only one transmitter at a time, using its index as the carrier information. This innovation introduces the spatial domain as an additional modulation dimension, thereby improving the system's spectral efficiency. Research has demonstrated that spatial modulation outperforms other MIMO strategies while also offering lower computational complexity for visible light wireless communication systems.

[0068] In one implementation, the index of the active reflection group can be a Huffman code. Figure 4 As shown, in one implementation, the multiple reflection groups include a first reflection group, a second reflection group, a third reflection group, and a fourth reflection group. The Huffman code of the first reflection group is 0. The Huffman code of the second reflection group is 10. The Huffman code of the third reflection group is 110. The Huffman code of the fourth reflection group is 111. The second reflection group is an activated reflection group, and its index is "10".

[0069] The light reflected by each reflective array element can reach at most one receiving unit.

[0070] By arranging a plurality of different array elements in the activated reflection group, light is reflected to different receiving units.

[0071] S4. The receiver receives a first optical signal carrying first data.

[0072] The receiver receives the light signal emitted by the light source transmitter (such as LED) and converts it back into an electrical signal. The receiver includes multiple receiving units arranged in an array.

[0073] In some embodiments, the receiving unit is a photodetector, which is also known as a photodiode (PD).

[0074] The first optical signal carrying the first data is called a reflected signal.

[0075] In some embodiments, the number of reflective elements in the activated reflective group is an integer multiple of the number of receiving units, so that each receiving unit receives a signal.

[0076] Combined Figure 1 and Figure 3 In one implementation, each reflective group has 16 elements. Four PDs receive the optical signal. During each transmission, each of the four activated elements in the reflective group reflects the incident light (the first optical signal and the first data) from the LED to one of the four PDs. In this way, the 16 elements can simultaneously transmit light to the four PDs, meaning that each PD receives the incident light.

[0077] Thus, the receiver receives the reflected signal.

[0078] The reflected signal contains data from the LED and the reflective surface. At the receiver side, the PD array receives the combined data from the LED and the reflective surface, which can be expressed as follows:

[0079]

[0080] Where n is the mean of 0 and the variance of σ 2 The real-valued additive white Gaussian noise is r, which is the photoelectric conversion coefficient; s includes the LED signal s LED and RIS signals RIS The union of is the equivalent channel gain, which can be expressed as:

[0081]

[0082] in, represents the Hadamard product, H is the gain of the non-line-of-sight channel from the LED to the PD, expressed as:

[0083]

[0084] where h ij (i=1,2,...,N r, j = 1, 2, ..., N e ) includes the product of the gain from the p-th LED to the j-th reflector and the gain from the j-th reflector to the i-th PD, expressed as

[0085] and They are the gain from the emitter to the array element of the jth reflector and the gain from the array element of the jth reflector to the i-th detector, respectively. The calculation formula for one case is given as:

[0086]

[0087] Where ξ and ∈ are correction coefficients, c is the extinction coefficient based on the atmospheric environment, and D R and D P are the aperture diameters of the reflective surface and the detector, respectively, and They represent the distance from the LED to the jth reflector array element and the distance from the jth reflector array element to the i-th detector, and are the corresponding longitudinal distances respectively. The reflection matrix F and the grouping matrix G are expressed as:

[0088]

[0089] Among them, f ij ∈{0, 1}, when f ij =1, it means that the jth reflector array element can reflect light to the i-th PD. ij =0, the opposite is true; g jk ∈{0, 1}, when g jk = 1, indicating that the jth reflector array element is divided into the kth group. Because each array element can only reflect the signal to one PD and belongs to only one group, the following constraints exist for the reflection matrix F and the grouping matrix G, and they remain unchanged after the system is determined.

[0090]

[0091] The visible light communication spatial modulation method based on the reflecting surface provided in the embodiment of the present application includes determining an activated reflection group in the reflection groups with different activation probabilities according to the channel gain of the first light signal emitted by the transmitter to adapt to the changing channel conditions. By setting a direct-line link obstruction, the problem of the transmission signal (first light signal) being blocked by obstacles due to line of sight obstacles and device direction is overcome, and the bit error rate is reduced. By controlling the spatial modulation mode of the activated reflection group, the data rate of the activated reflection group is changed, and the data rate of the transmitter and the activated reflection group are transmitted in parallel. In this way, the overall rate performance and the overall energy efficiency of the system are improved at the same time, thereby improving the spatial modulation capability of visible light communication.

[0092] The reflective surface-based visible light communication spatial modulation method provided in the embodiments of the present application can increase the modulation speed of the light source and reduce the impact of ambient light interference on the signal.

[0093] The reflective surface-based visible light communication spatial modulation method provided in the embodiments of the present application can combine spatial modulation technology with reconfigurable smart surfaces in visible light communication to achieve more efficient data transmission.

[0094] The reflective surface-based visible light communication spatial modulation method provided in this application optimizes spatial modulation performance by dynamically adjusting the characteristics of the reflected signal by setting the reflective surface. This method not only reduces the reliance on power amplifiers for signal generation but also increases system flexibility, making it particularly advantageous in situations where power is limited or a large number of devices are required to transmit data.

[0095] The reflective surface-based visible light communication spatial modulation method provided in the embodiments of this application combines visible light wireless communication, reconfigurable smart surfaces, and spatial modulation technology, providing new ideas and solutions for future wireless communication systems. This innovative combination not only improves data transmission rates but also effectively copes with environmental interference, improving the security and reliability of communications. With the deepening of research and the continuous development of technology, this field is expected to be widely used in application scenarios such as smart cities and smart homes, promoting the further development of wireless communication technology.

[0096] The reflective surface-based visible light communication spatial modulation method provided in the embodiments of the present application considers the transmitting LED and the reflective surface separately, providing an independent reflective surface spatial modulation scheme that is independent of the LED's modulation order and modulation mode. This eliminates the need for an RIS controller, eliminating deployment challenges in practical applications. The reflective surface's independence from the LED does not limit the data rate. Furthermore, it is independent of the power amplifier's configuration, making it suitable for power-constrained applications or for large numbers of devices transmitting data.

[0097] The reflector-based spatial modulation method for visible light communication provided in this application's embodiments incorporates Huffman coding into reflector selection, resulting in varying probabilities for reflector selection and adapting to dynamic communication scenarios with fluctuating channel conditions. This technology improves system flexibility and data rates, adapts to dynamically changing channel conditions, overcomes line-of-sight obstructions and device orientation issues, and optimizes the rate at which information is transmitted across the reflector, thereby enabling a more efficient and reliable visible light communication system.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

[0099] Furthermore, it is clear that the word "comprising" does not exclude other units or steps, and the singular does not exclude the plural. Multiple units or devices recited in a device claim may also be implemented by a single unit or device through software or hardware. Terms such as "first" and "second" are used to indicate names and do not imply any particular order.

Claims

1. A visible light communication spatial modulation method based on a reflecting surface, characterized in that: include: determining an activated reflection group of the reflection surface according to a channel gain of the first optical signal transmitted by the transmitter; The reflective surface includes a plurality of reflective groups; each of the reflective groups includes a plurality of reflective array elements; the plurality of reflective array elements are distributed in an N*N array, where N is a positive integer; the activated reflective group is one of the plurality of reflective groups; and at least two of the reflective groups have different activation probabilities; The transmitter sends the first optical signal to the activated reflection group; The activated reflective group receives the first optical signal and sends the first optical signal carrying first data to a receiver; the receiver includes a plurality of receiving units arranged in an array; the first data includes an index of the activated reflective group; light reflected by each reflective array element can reach at most one receiving unit; A line-of-sight link obstruction is provided between the transmitter and the receiver, so that the first optical signal transmitted by the transmitter cannot be directly received by the receiver; the transmitter, the line-of-sight link obstruction, and the receiver are located on a first axis; the reflective surface is provided outside the first axis and is located between the transmitter and the receiver; The receiver receives the reflected signal; the reflected signal is the first optical signal carrying the first data, including data from the light-emitting diode and from the reflecting surface. At the same time, on the receiver side, the photodetector array receives the combined data of the light-emitting diode and the reflecting surface, which can be expressed by the following formula: Where n is the mean of 0 and the variance of σ 2 The real value of the additive Gaussian white noise; r is the photoelectric conversion coefficient; s includes the light emitting diode signal s LED and RIS signals RIS The union of is the equivalent channel gain, which can be expressed as: in, represents the Hadamard product, H is the gain of the non-line-of-sight channel from the light-emitting diode to the photodetector, expressed as: where h ij (i=1,2,...,N r , j = 1, 2, ..., N e ) includes the product of the gain from the p-th light-emitting diode to the j-th reflective surface and the gain from the j-th reflective surface to the i-th photodetector, expressed as and They are the gain from the emitter to the array element of the jth reflector and the gain from the array element of the jth reflector to the i-th detector, respectively. The calculation formula for one case is given as: Where ξ and ∈ are correction coefficients, c is the extinction coefficient based on the atmospheric environment, and D R and D P are the aperture diameters of the reflective surface and the detector, respectively, and They represent the distance from the light emitting diode to the jth reflector array element and the distance from the jth reflector array element to the i-th detector, and are the corresponding longitudinal distances respectively; the reflection matrix F and the grouping matrix G are expressed as: Among them, f ij ∈{0, 1}, when f ij =1, it means that the jth reflective surface element can reflect light to the i-th photodetector. ij =0, the opposite is true; g jk ∈{0, 1}, when g jk =1, indicating that the jth reflector array element is divided into the kth group; because each array element can only reflect the signal to one photodetector and belongs to only one group, the following constraints exist for the reflection matrix F and the grouping matrix G, and they remain unchanged after the system is determined; 2. The visible light communication spatial modulation method based on a reflecting surface according to claim 1, characterized in that: When performing the step of determining the activated reflective group of the reflective surface according to the channel gain of the first optical signal transmitted by the transmitter, the visible light communication spatial modulation method based on the reflective surface further includes: Generate a Huffman code according to the number of the reflection groups as information transmitted by the reflection surface node; Based on the Huffman code, the activation probability of each of the reflection groups is determined; the longer the codeword in the Huffman code, the smaller the activation probability.

3. The visible light communication spatial modulation method based on a reflecting surface according to claim 2, characterized in that: When performing the step of determining the activated reflective group of the reflective surface according to the channel gain of the first optical signal transmitted by the transmitter, the visible light communication spatial modulation method based on the reflective surface further includes: The activation probability of the reflection group is determined according to the channel gain; the higher the value of the channel gain, the higher the activation probability.

4. The visible light communication spatial modulation method based on a reflecting surface according to claim 3, characterized in that: The evaluation parameter of the channel gain includes a signal-to-noise ratio; the higher the value of the signal-to-noise ratio, the higher the activation probability.

5. The visible light communication spatial modulation method based on a reflecting surface according to any one of claims 1 to 4, characterized in that: The number of the reflective array elements in the activated reflective group is an integer multiple of the number of the receiving units, so that each of the receiving units receives a signal.

6. The visible light communication spatial modulation method based on a reflecting surface according to any one of claims 1 to 4, characterized in that: The plurality of reflection groups include a first reflection group, a second reflection group, a third reflection group and a fourth reflection group; The index of the first reflection group is 0, and the activation probability is 0.5; the index of the second reflection group is 10, and the activation probability is 0.25; the index of the third reflection group is 110, and the activation probability is 0.125; the index of the fourth reflection group is 111, and the activation probability is 0.

125.

7. The visible light communication spatial modulation method based on a reflecting surface according to any one of claims 1 to 4, characterized in that: Before the transmitter sends the first optical signal to the activated reflective group, the visible light communication spatial modulation method based on the reflective surface further includes: The first optical signal is preprocessed by pulse amplitude modulation.

8. The visible light communication spatial modulation method based on a reflecting surface according to any one of claims 1 to 4, characterized in that: The emitter is a light emitting diode.

9. The visible light communication spatial modulation method based on a reflecting surface according to any one of claims 1 to 4, characterized in that: The receiving unit is a photoelectric detector.

10. A visible light communication spatial modulation system based on a reflecting surface, characterized in that: include: Transmitter, reflective surface, line-of-sight link obstruction, and receiver; The transmitter sends a first optical signal to the activated reflective group; The reflective surface includes a plurality of reflective groups; each reflective group includes a plurality of reflective array elements; the plurality of reflective array elements are distributed in an N*N array, where N is a positive integer; the activated reflective group is one of the plurality of reflective groups; the activated reflective group is determined by the reflective surface according to the channel gain of the first optical signal; and at least two of the reflective groups have different activation probabilities; The activated reflective group is configured to receive the first optical signal and transmit the first optical signal carrying the first data to a receiver; the receiver comprises a plurality of receiving units arranged in an array; the first data comprises an index of the activated reflective group; and light reflected by each reflective array element can reach at most one receiving unit; A line-of-sight link obstruction is provided between the transmitter and the receiver, so that the first optical signal transmitted by the transmitter cannot be directly received by the receiver; The transmitter, the line-of-sight link obstructor, and the receiver are located on a first axis; The reflecting surface is arranged outside the first axis, and the reflecting surface is located between the transmitter and the receiver; The receiver receives the reflected signal; the reflected signal is the first optical signal carrying the first data, including data from the light-emitting diode and from the reflecting surface. At the same time, on the receiver side, the photodetector array receives the combined data of the light-emitting diode and the reflecting surface, which can be expressed by the following formula: Where n is the mean of 0 and the variance of σ 2 The real value of the additive Gaussian white noise; r is the photoelectric conversion coefficient; s includes the light emitting diode signal s LED and RIS signals RIS The union of is the equivalent channel gain, which can be expressed as: in, represents the Hadamard product, H is the gain of the non-line-of-sight channel from the light-emitting diode to the photodetector, expressed as: where h ij (i=1,2,...,N r ,j=1,2,...,N e ) includes the product of the gain from the p-th light-emitting diode to the j-th reflective surface and the gain from the j-th reflective surface to the i-th photodetector, expressed as and They are the gain from the emitter to the array element of the jth reflector and the gain from the array element of the jth reflector to the i-th detector, respectively. The calculation formula for one case is given as: Where ξ and ∈ are correction coefficients, c is the extinction coefficient based on the atmospheric environment, and D R and D P are the aperture diameters of the reflective surface and the detector, respectively, and They represent the distance from the light emitting diode to the jth reflector array element and the distance from the jth reflector array element to the i-th detector, and are the corresponding longitudinal distances respectively; the reflection matrix F and the grouping matrix G are expressed as: Among them, f ij ∈{0, 1}, when f ij =1, it means that the jth reflective surface element can reflect light to the i-th photodetector. ij =0, the opposite is true; g jk ∈{0, 1}, when g jk =1, indicating that the jth reflector array element is divided into the kth group; because each array element can only reflect the signal to one photodetector and belongs to only one group, the following constraints exist for the reflection matrix F and the grouping matrix G, and they remain unchanged after the system is determined;

Images