WO2023019538A1

WO2023019538A1 - Cross-cell reception method for visible light communication

Info

Publication number: WO2023019538A1
Application number: PCT/CN2021/113667
Authority: WO
Inventors: 薛婧姝; 张海勇; 王小景; 王贾予沣; 韩胜涛; 刘洛琨; 陈文民; 梁进山
Original assignee: 东莞信大融合创新研究院
Priority date: 2021-08-20
Filing date: 2021-08-20
Publication date: 2023-02-23

Abstract

Disclosed in the present invention is a cross-cell reception method for visible light communication. The method comprises: in a dense optical cell scenario, performing multi-angle reception by using a visible light receiving apparatus of a cubic structure; on the basis of an average power that has been received by the visible light receiving apparatus at each angle, and in combination with a geometric constraint of the visible light receiving apparatus, obtaining a channel matrix estimation value; and designing a signal recovery algorithm on the basis of the channel matrix estimation value, so as to realize signal recovery of a receiving end in two cases, i.e. inside an optical cell and in an overlapping area of two optical cells. By means of the present invention, on the basis of a multi-angle reception characteristic of a cubic visible light receiving apparatus, a boundary of an optical cell is blurred at a receiving end, and the handover-free active reception of a mobile user in a dense optical cell system is thus realized in a physical layer, so as to meet new requirements brought about by edge computing and high-speed low-latency communication in an industrial Internet of Things scenario.

Description

A cross-cell receiving method for visible light communication

technical field

The present invention relates to the technical field of cross-cell reception of visible light communication, in particular to a method for cross-cell reception of visible light communication.

Background technique

In the field of intelligent manufacturing, in order to meet the communication requirements of dense and diverse production elements, the traffic density supported by the communication system should reach tens of Mbps/m ² ; at the same time, since the communication in industrial manufacturing is directly oriented to production, the requirements for transmission delay More demanding than 5G communications for driverless applications. Therefore, communication systems for industrial manufacturing need to meet the requirements of high speed, high density, and low delay. Visible light has rich bandwidth resources and natural security features, and is a good choice for communication in industrial IoT scenarios.

In traditional multi-cell visible light communication, the design goal of the system is to ensure the continuity of communication access for mobile users. However, in the context of the Industrial Internet of Things, the characteristics of edge computing make data more immediacy and closely associated with location. Faced with a large number of users within its coverage area, the optical base station needs to transmit a large amount of status data in the area in real time by broadcasting. In order to improve the data throughput of the system, optical base stations are often densely arranged in the factory building, and the signal aliasing between optical cells will reduce the effective communication coverage of each base station, which may cause mobile users to not be able to receive signals near their destination in time. information and thus increase the time to respond. Therefore, a receiving method capable of adapting to optical cell aliasing is needed.

In wireless communication, "cellular technology" is often used to solve the problem of cross-cell communication. By using different communication carrier frequencies in adjacent cells to realize communication at overlapping positions of optical cells, however, the idea of frequency division multiplexing obviously doubles the loss of frequency utilization and reduces communication efficiency. At the same time, the process of cross-cell communication often needs to cooperate with the corresponding handshake protocol to complete the handover. The main idea is to sense channel deterioration and establish a new link. This process obviously makes the reception passive, and at the same time involves higher-level communication protocols and more complex The interaction process may increase the communication delay and the complexity of the system.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, and provide a cross-cell receiving method for visible light communication, which is based on the multi-angle receiving characteristics of a cube visible light receiving device, blurs the boundary of the optical cell at the receiving end, and then realizes the mobile user at the physical layer. Handover-free active reception under the dense optical cell system to meet the new requirements brought by edge computing and high-speed and low-latency communication in the industrial Internet of Things scenario.

Technical scheme of the present invention is as follows:

A cross-cell receiving method for visible light communication, comprising:

In the dense light cell scene, the visible light receiving device with a cubic structure is used for multi-angle reception;

Based on the average power received at each angle of the visible light receiving device, combined with the geometric constraints of the visible light receiving device, an estimated value of the channel matrix is obtained;

Based on the estimated value of the channel matrix, a signal recovery algorithm is designed to realize the signal recovery of the receiving end in the optical cell and in the overlapping area of two optical cells.

Further, the dense light cells include several light cells, and each light cell is produced by a light source at the transmitting end, and several light sources at the transmitting end are equidistantly distributed on the same straight line, so that two adjacent light cells form a overlapping area.

Further, the visible light receiving device of the cube structure is composed of a first photon detector, a second photon detector, a third photon detector, a fourth photon detector and a fifth photon detector array, wherein the first photon detector The detector, the third photon detector, the fourth photon detector, and the second photon detector face four directions, left, right, front and back, respectively, and the fifth photon detector faces vertically upward.

Further, the signal recovery of the receiving end inside the optical cell and in the overlapping area of two optical cells is based on the channel estimation model Y=HX+N, that is, X is restored by Y, where Y is the received signal matrix, H is the channel matrix, X is the transmitted signal matrix, and N is the zero-mean Gaussian noise matrix.

Further, in the case of overlapping regions of two optical cells, set

Where h ₁ and h ₂ are the attenuation factors of the corresponding channels, and d ₁ and d ₂ are the distances between the light source at the corresponding transmitting end and the center of the visible light receiving device.

Further, based on

have

in,

And B ₂ ＝P ₂ /(P ₀ D), B ₄ ＝P ₄ /(P ₀ D), B ₅ ＝P ₅ /(P ₀ H), D is the distance between two light sources at the transmitting end, and H is the transmitting The height of the end light source, P ₀ is the average power of the transmitted signal, P ₂ is the average power received by the second photon detector, P ₄ is the average power received by the fourth photon detector, P ₅ is the fifth photon detector The received average power, P ₂ , P ₄ , and P ₅ can be obtained by P _i =A _i /C _s , where C _s is the detection efficiency of the photon detector, and A _i is the average amplitude of the response of the visible light receiving device within the sampling time.

Further, all light source marking sequences are respectively compared with the signal received by the fifth photon detector

For correlation, select the two largest sequences, denoted as

and

For a light source label sequence of length L _m

and

Make the following mapping

Where l is the serial number of the light source mark, and the received signal sequence with a length of L _s is processed as follows

Afterwards respectively

and

do correlation, ie

remember

The maximum value of

then you can

Select a feasible solution from two groups of possible solutions of X ₁ and X ₂ for the condition.

Further, according to the Lambertian model can be obtained

Among them, m ₀ can be obtained from the half power angle ψ _h of the light source by m ₀ =-ln 2/lnψ _h , and then h ₁ =X ₁ d ₁ , h ₂ =X ₂ d ₂ can be obtained.

Further, the channel matrix estimate

in

Further, the signal recovery algorithm includes two signal recovery methods, the exhaustive minimum search algorithm and the least squares method.

Compared with the prior art, the beneficial effects of the present invention are:

1) The present invention focuses on solving the new demand for visible light communication in industrial Internet of Things scenarios, and aims to enable mobile users to spontaneously receive broadcast signals from one or more adjacent optical cells through the design of the receiving scheme. The target scenario The construction is more in line with the characteristics of close connection between data and location and dense communication users under the Industrial Internet of Things;

2) The present invention adopts a cube visible light receiving device, utilizes its unique multi-angle receiving feature and easy-to-calculate geometric relationship, and combines the basic principles of geometry and optics to establish a channel estimation algorithm,

This algorithm is mainly based on the average power of the received signal on each side of the visible light receiving device, which can adapt to more modulation methods and is relatively simple to implement. At the same time, it can adapt to two situations in the cell and at the overlap of cells, and its simplicity and versatility provide support for the realization of spontaneous reception at the physical layer;

3) The present invention proposes two kinds of signal recovery algorithms on the basis of channel estimation, wherein, the minimum exhaustive search algorithm has better signal recovery performance, but the complexity is higher, and although the performance of the least squares method is slightly worse than the minimum exhaustive search The algorithm has a lower complexity, and the above two algorithms can adapt to different scene requirements, which improves the practicability of the invention;

4) The present invention is different from the existing cross-cell communication of mobile users through the more complicated upper layer control feedback protocol. The present invention is carried out spontaneously at the physical layer, which can reduce the communication delay and complexity generated by the system control when crossing cells to a certain extent. Low cost, the performance of the present invention is obviously better than cellular technology, and has effectiveness and reliability.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the descriptions of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only of the present invention. For some embodiments, those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort.

FIG. 1 is a schematic diagram of a scene of a dense light cell according to the present invention;

2 is a schematic structural view of the visible light receiving device of the present invention;

Fig. 3 is a schematic diagram of scene division according to the present invention;

Fig. 4 is a schematic diagram of the frame structure of the present invention;

Fig. 5 is two kinds of model modeling schematic diagrams of A and B described in the present invention;

Fig. 6 is a schematic diagram of the simulation of the feasibility of the channel estimation algorithm under the double-lamp model under the single-lamp model according to the present invention;

FIG. 7 is a schematic diagram of a simulation of the average relative error of channel estimation under different signal sampling lengths according to the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The present invention aims to realize the active reception of mobile visible light communication with fuzzy optical cell boundaries at the physical layer in the scene of the industrial Internet of things. The main technical problems to be solved: one is to solve the signal interference problem at the overlapping position of the optical cell, and then blur the boundary of the optical cell; the other is that the receiving scheme should be applicable to the single-point reception of the mobile user in the optical cell under the condition of the upper layer control protocol And the multi-point reception at the junction of optical cells makes it feasible to realize it at the physical layer; the third is to avoid the problem of efficiency loss caused by anti-aliasing and anti-interference algorithms.

In order to illustrate the technical solutions described in the present invention, specific examples are used below to illustrate.

Example

This embodiment provides a cross-cell receiving method for visible light communication, including:

1) In the dense light cell scene, use a cube-shaped visible light receiving device for multi-angle reception;

As shown in Figure 1, the dense light cells include several light cells, each light cell is produced by a light source at the transmitting end, and several light sources at the transmitting end are equidistantly distributed on the same straight line, so that two adjacent light cells An overlapping area is formed between them.

2) Based on the average power received at each angle of the visible light receiving device, combined with the geometric constraints of the visible light receiving device, the estimated value of the channel matrix is obtained;

As shown in Figure 2, the visible light receiving device of described cube structure is made up of first photon detector 1, second photon detector 2, the 3rd photon detector 3, the 4th photon detector 4 and the 5th photon detector 5 arrays Composition, wherein the first photon detector 1, the third photon detector 3, the fourth photon detector 4, and the second photon detector 2 face four directions, left, right, front and back, respectively, and the fifth photon detector 5 faces vertically upward.

The scene can be divided into two sub-models, A and B, as shown in Figure 3:

A. Single lamp model: the receiving end is inside the optical cell, and only needs to receive the signal emitted by the corresponding light source in the cell;

B. Double lamp model: the receiving end is in the overlapping area of two optical cells, and at this time it is necessary to receive the signals emitted by the corresponding two light sources as much as possible.

3) Design a signal recovery algorithm on the basis of the estimated value of the channel matrix to realize the signal recovery of the receiving end in the optical cell interior and in the overlapping area of two optical cells;

Signal recovery is based on the channel estimation model Y=HX+N, where Y is the received signal matrix, H is the channel matrix, X is the transmitted signal matrix, and N is the zero-mean Gaussian noise matrix, that is, X is restored from Y.

On the above premise, a matching frame structure as shown in Figure 4 is designed, and the part between the two dotted lines in the figure is a frame. The head of each frame is a fixed sync header, and the receiving end realizes symbol synchronization and intra-frame data positioning through sliding correlation of the sync header. There are several subframes after the sync header, and each subframe consists of a light source label with a length of L _m and a load with a length of L _s . Among them, the light source labels are orthogonal to each other, and the length of L _s is determined by the sampling length of the channel estimation. When there is data transmission, the load is a modulated binary sequence; when there is no data transmission, the load is an alternating sequence of 0 and 1 to ensure that the average transmit power remains unchanged. After synchronizing the two signals, the receiving end performs sampling with the period of the subframe length L _m + L _s . At the end of each frame, there is a fixed sequence as an end-of-frame marker.

The modeling of the two models A and B is shown in Figure 5. Under the double-lamp model on the right, set

Among them, h ₁ and h ₂ are the attenuation factors of the corresponding channels, d ₁ and d ₂ are the distances between the light source at the corresponding transmitting end and the center of the visible light receiving device.

in,

And B ₂ ＝P ₂ /(P ₀ D), B ₄ ＝P ₄ /(P ₀ D), B ₅ ＝P ₅ /(P ₀ H), D is the distance between two light sources at the transmitting end, and H is the transmitting The height of the end light source, P ₀ is the average power of the transmitted signal, P ₂ is the average power received by the second photon detector, P ₄ is the average power received by the fourth photon detector, P ₅ is the fifth photon detector The received average power, P ₂ , P ₄ , P ₅ can be obtained by P _i =A _i /C _s , C _s is the detection efficiency of the photon detector (unit: A/W), A _i is the visible light received within the sampling time The average magnitude of the device's response. Combine all light source marking sequences with the signal received by the fifth photon detector

For correlation, select the two largest sequences, denoted as

and

For a light source label sequence of length L _m

and

Make the following mapping

Afterwards respectively

and

do correlation, ie

remember

The maximum value of

then you can

Select a feasible solution from two groups of possible solutions of X ₁ and X ₂ for the condition. At the same time, according to the Lambertian model, we can get

Among them, m ₀ can be obtained from the half power angle ψ _h of the light source by m ₀ =-ln 2/lnψ _h , and then h ₁ =X ₁ d ₁ , h ₂ =X ₂ d ₂ can be obtained. At the same time, the angle marked in the figure can be obtained

It can be seen from this that when the visible light receiving device is located in the position in the figure, the estimated value of the channel matrix

Similarly, if , it can be judged that the receiver is on the other side of the line connecting the two lights. At this time, the corresponding ground, and angle can be obtained in the same way. At this time, the estimated value of the channel matrix

The channel estimation under the single lamp model is discussed below, let P _a =max{P ₁ ,P ₃ }, P _b =max{P ₂ ,P ₄ }, that is, take the maximum value of the two numbers in the brackets, we have

Available

Therefore, the estimated value of the channel matrix

Among them, when P ₁ ≥ _{P 3}

otherwise

When P ₂ ≥ _{P 4}

otherwise

Under the single-lamp model, the double-lamp model is adopted. Ideally, one column of the channel matrix is all zeros, and the other column is the same as the solution obtained under the single-lamp model. As shown in Figure 6, the simulation verifies the feasibility of the channel estimation algorithm under the double lamp model under the single lamp model.

Under the condition of considering the interference of adjacent lights (the coordinates of the interference source are (-4, 0, 5) and (4, 0, 5) respectively), it is tested that when the visible light receiving device is at different positions on the light source line, the coordinates are (0 , 0, 5) The relative error of channel estimation for the main light sources. Among them, SM means estimation by single-lamp model, and DM means estimation by dual-lamp model, and at the same time control the half-power angle of the light source to adjust the degree of optical cell interference. It can be found that when DM is used, its channel estimation performance is slightly inferior to that of SM directly under the main light source. The signal is larger; and at a position farther away from the main light source, because DM takes into account the interference of adjacent lights, and the signal of the main light source received by the second photon detector 2 and the fourth photon detector 4 increases, the use of DM is better than that of SM has obvious advantages. This result verifies that the channel estimation algorithm under DM has universality and good performance in the interior of the cell and at the border of the cell.

Based on the estimated value H of the channel matrix, signal recovery and decision can be performed. Two signal recovery methods, Exhaustive Searching (ES) and Least Square (LS), are introduced below.

Algorithm 1: ES Algorithm

①Based on the constellation diagram, the set X={X _i } of the emission signals X of the two lamps is obtained;

②Substitute each element X _i in the set into the calculation Ψ _i =||Y-HX _i ||;

③ Take the information sequence corresponding to Xi _i that minimizes Ψ _i as the judgment result.

In order to avoid the high complexity brought by the ES algorithm, the LS algorithm is introduced below.

Algorithm 2: LS Algorithm

① Calculate X=(H ^Τ Η) ^-1 Η ^Τ Y to obtain the recovery value of the sent signal;

②According to the constellation diagram and mapping relationship of the transmitted signal, the judgment result is obtained according to the minimum Euclidean distance criterion. As shown in Figure 7, the average value of the relative error of channel estimation under different signal sampling lengths is shown. It can be obtained from the simulation results that with the gradual increase of the sampling length, the relative error of the channel estimation decreases gradually. It can be imagined that when the sampling length is long enough, the error of the average power can be eliminated, and the channel matrix obtained by solving the equation is the real value of the channel matrix.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention. Inside.

Claims

A cross-cell receiving method for visible light communication, characterized in that it includes:

In the dense light cell scene, the visible light receiving device with a cubic structure is used for multi-angle reception;

Based on the average power received at each angle of the visible light receiving device, combined with the geometric constraints of the visible light receiving device, an estimated value of the channel matrix is obtained;

Based on the estimated value of the channel matrix, a signal recovery algorithm is designed to realize the signal recovery of the receiving end in the optical cell and in the overlapping area of two optical cells.
A cross-cell receiving method for visible light communication according to claim 1, wherein the dense optical cell includes several optical cells, each optical cell is generated by a light source at the transmitting end, and several light sources at the transmitting end, etc. The spacing is distributed on the same straight line, so that an overlapping area is formed between two adjacent optical cells.
A cross-cell receiving method for visible light communication according to claim 2, characterized in that, the visible light receiving device with a cubic structure is composed of a first photon detector, a second photon detector, a third photon detector, a fourth photon detector, and a fourth photon detector. detector and a fifth photon detector array, wherein the first photon detector, the third photon detector, the fourth photon detector, and the second photon detector face four directions, left, right, front and back, respectively, and the fifth photon detector The detector is facing straight up.
A cross-cell receiving method for visible light communication according to claim 3, characterized in that the signal recovery of the receiving end in the optical cell and in the overlapping area of two optical cells is based on the channel estimation model Y= HX+N, that is, restore X from Y, where Y is the received signal matrix, H is the channel matrix, X is the transmitted signal matrix, and N is the zero-mean Gaussian noise matrix.
A cross-cell receiving method for visible light communication according to claim 4, characterized in that, in the case of overlapping areas of two optical cells, set
Where h 1 and h 2 are the attenuation factors of the corresponding channels, and d 1 and d 2 are the distances between the light source at the corresponding transmitting end and the center of the visible light receiving device.
A cross-cell receiving method for visible light communication according to claim 5, characterized in that, based on
have
in,
And B 2 ＝P 2 /(P 0 D), B 4 ＝P 4 /(P 0 D), B 5 ＝P 5 /(P 0 H), D is the distance between two light sources at the transmitting end, and H is the transmitting The height of the end light source, P 0 is the average power of the transmitted signal, P 2 is the average power received by the second photon detector, P 4 is the average power received by the fourth photon detector, P 5 is the fifth photon detector The received average power, P 2 , P 4 , and P 5 can be obtained by P i =A i /C s , where C s is the detection efficiency of the photon detector, and A i is the average amplitude of the response of the visible light receiving device within the sampling time.
A cross-cell receiving method for visible light communication according to claim 6, characterized in that all the light source marking sequences are respectively combined with the signal received by the fifth photon detector
For correlation, select the two largest sequences, denoted as
and
For a light source label sequence of length L m
and
Make the following mapping

in
is the serial number marked by the light source, and the received signal sequence of length L s is processed as follows

Afterwards respectively
and
and
do correlation, ie

remember
The maximum value of
then you can
Select a feasible solution from two groups of possible solutions of X 1 and X 2 for the condition.
A cross-cell receiving method for visible light communication according to claim 7, characterized in that, according to the Lambertian model can be obtained

Among them, m 0 can be obtained from the half power angle ψ h of the light source by m 0 =-ln 2/lnψ h , and then h 1 =X 1 d 1 , h 2 =X 2 d 2 can be obtained.
A cross-cell receiving method for visible light communication according to claim 8, characterized in that the estimated value of the channel matrix

in
The cross-cell receiving method for visible light communication according to claim 1, wherein the signal recovery algorithm includes two signal recovery methods: a minimum exhaustive search algorithm and a least squares method.