Visible light-based multi-user MIMO-OFDMA communication resource allocation method and storage medium

Abstract

The invention discloses a visible light-based multi-user MIMO-OFDMA (Multiple Input Multiple Output-Orthogonal Frequency Division Multiple Access) communication resource allocation method and a storage medium, an MIMO technology improves the capacity of a system in a spatial domain on the basis of not occupying more frequency domain resources, in an MIMO-VLC (Visible Light Communication) system, user dimensions are further introduced, an OFDMA technology is used, and each user transmits information on different frequency bands. On the basis, an LED low-pass model is introduced, dimension reduction is carried out on a visible light-based multi-user MIMO-OFDMA three-dimensional algorithm, and then the system is solved by using a Lagrange algorithm according to the low-pass response of each user in different frequency bands of an LED low-pass channel. According to the method, the optimal value of the power of each user can be adaptively solved in the frequency domain according to the measured channel response of each user, and finally, the optimal solution of the rate of using the OFDMA technology can be obtained, so that the performance of the system is further improved.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to a method for allocating multi-user MIMO-OFDMA communication resources based on visible light and a storage medium. Background Art

[0002] The growing demand for large traffic and dense connections in future 6G communications has resulted in the current radio frequency (RF) band being insufficient to meet higher-speed services, while visible light communication (VLC) using visible light provides a rich spectrum source for data transmission. In addition, VLC has the dual functions of lighting and information transmission, and has the advantages of indoor security and license-free. VLC is considered to be one of the key technologies in 6G communications, solving the problem of RF congestion by utilizing unregulated spectrum.

[0003] However, LED has the disadvantage of being band-limited. In order to improve the spectral efficiency of the limited bandwidth of the LED-based VLC system, Orthogonal Frequency Division Multiple Access (OFDMA) and Multiple Input Multiple Output (MIMO) technologies are used. OFDMA allows adaptive power and bit load in each frequency domain, while MIMO technology can use distributed light sources on the ceiling to manage line-of-sight (LOS) blocking of directional paths, thereby achieving reliable connections and significant transmission rate increments. Therefore, in VLC systems, the natural combination of OFDMA and MIMO becomes a key technology to improve communication rate and reliability. In actual application scenarios, there may be multiple users within the coverage area of ​​the system. Based on the low-frequency channel response of LED, MIMO-OFDMA technology is combined, and the Lagrangian algorithm is used to allocate resources among multiple users, so as to use as much bandwidth as possible and further improve the throughput of the system. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a method for allocating multi-user MIMO-OFDMA communication resources based on visible light and a storage medium. In VLC, MIMO is combined with OFDMA, and multiple users and LED low-communication channel models are considered. Since the channels brought by different spatial positions are different, the SVD decomposition technology is used to reduce the three-dimensional system into a one-dimensional frequency domain system. The Lagrangian algorithm is used to adaptively allocate power according to the LED channel status, which can not only further utilize the bandwidth of the LED but also further improve the capacity of the system.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for allocating multi-user MIMO-OFDMA communication resources based on visible light, comprising the following steps:

[0006] 1. Assume that there are M users, and each user generates N data streams;

[0007] 2. Map the data information stream into QAM symbols;

[0008] 3. Convert the generated N-channel QAM symbols from serial data streams into parallel data streams, then modulate the parallel data into OFDM signals through IFFT in Hermitian symmetry, add cyclic prefixes to the modulated symbols, and convert them into serial data;

[0009] 4. Perform multi-channel processing according to the pre-measured LED low-pass channel response, and pre-process the generated OFDM signal using the decomposed pre-processing matrix;

[0010] 5. After the signal is received through the channel, it is corrected using the decomposed post-processing matrix. Finally, each user gets an N*N channel.

[0011] 6. Reduce the target rate problem in three dimensions, namely, spatial domain, user domain and frequency domain, to a one-dimensional signal in the frequency domain;

[0012] 7. Under certain power constraints, according to the power bit allocation algorithm, power is adaptively allocated to different users in different frequency bands. After obtaining an optimal value allocation principle, the rate expression under the OFDMA modulation method is calculated.

[0013] Preferably, in step 4, the LED low-pass channel is a special low-pass channel based on visible blue LED, which is described as:

[0014]

[0015] Preferably, in step four, the channel processing includes channel preprocessing, postprocessing and channel decomposition, and the generated OFDM signal is preprocessed with the preprocessing matrix after decomposition, and the two are multiplied to obtain the matrix expression after preprocessing.

[0016] Preferably, in step five, the correction is performed by multiplying the decomposed matrix by the post-processing matrix.

[0017] Preferably, in step four and step six, the frequency domain and the special channel characteristics of the visible blue light LED are first combined, and then the decomposition technology is used to reduce the MIMO channel of the multi-user MIMO-OFDMA to a separate SISO channel; since each user uses a different frequency band, the decomposition technology is used to reduce the three dimensions of the spatial domain, frequency domain and user domain to a one-dimensional frequency domain.

[0018] Preferably, in step seven, the optimal value allocation principle is used to adaptively allocate power to each frequency domain of the multi-user MIMO-OFDMA according to the channel conditions, and the process is described as follows:

[0019] a. According to the optimal value allocation, the multi-user MIMO-OFDMA model of the visible light is established as:

[0020]

[0021] Where M is the number of users, N is the number of spatial subchannels, and λ m,nn and P mn (f) are the singular values ​​and the power allocated to the mth channel of the nth user, respectively. N0 and Γ are the power spectral density of the noise and the signal-to-noise ratio gap, respectively. T is the total power, f m is the bandwidth range of the mth user, f c is the 3-dB cutoff frequency, B is the total signal bandwidth;

[0022] b. Reduce the system dimension into a separate sub-channel for each user to perform power allocation only in the frequency domain;

[0023] c. To find the optimal solution for the above model according to the Lagrangian algorithm, we only need to calculate the optimal solution of the power and model the relevant solution as follows:

[0024]

[0025] d. Obtain the optimal solution according to the above formula, and then adaptively allocate power to each frequency domain of multi-user MIMO-OFDMA according to the channel conditions.

[0026] On the other hand, to achieve the above-mentioned purpose, the present invention also provides the following technical solution: a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the method for allocating multi-user MIMO-OFDMA communication resources based on visible light is implemented.

[0027] The beneficial effect of the present invention is that the MIMO-OFDMA technology is combined with the low-communication channel of the LED, and the multi-user scenarios that may appear in practical applications are also considered. Under this model, it is necessary to consider the optimization algorithms in the three-dimensional domains of space, frequency, and user domains, and the three-dimensional domain is converted into an optimization algorithm in the one-dimensional frequency domain through the SVD technology and OFDMA technology. Finally, the Lagrangian algorithm is used to optimize the power and obtain the optimal solution in terms of throughput. Not only that, it also takes into account that different spatial positions of LEDs can obtain different power channel responses. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of a flow chart of a method for allocating multi-user MIMO-OFDMA communication resources based on visible light in an embodiment of the present invention;

[0029] Figure 2A schematic diagram of the distribution of multi-user MIMO-OFDMA in an embodiment of the present invention;

[0030] Figure 3 Schematic diagram of each channel state of multi-user MIMO-OFDMA in an embodiment of the present invention;

[0031] Figure 4 It is a schematic diagram of multi-user MIMO-OFDMA simulation results in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] See also Figure 1-Figure 4 The present invention provides the following technical solution: a method for allocating multi-user MIMO-OFDMA communication resources based on visible light, comprising the following steps:

[0034] 1. Each user generates N data streams, and there are M users in total;

[0035] 2. Map the data information stream into QAM symbols;

[0036] 3. Convert the generated N-channel QAM symbols from serial data streams into parallel data streams, then modulate the parallel data into OFDM signals through IFFT in Hermitian symmetry, add cyclic prefixes to the modulated symbols, and convert them into serial data;

[0037] 4. Perform multi-channel processing according to the pre-measured LED low-pass channel response, and use the decomposed preprocessing matrix to preprocess the generated OFDM signal; the channel processing includes channel preprocessing, post-processing and channel decomposition, and use the decomposed preprocessing matrix to preprocess the generated OFDM signal, and multiply the two to obtain the preprocessed matrix expression;

[0038] 5. After the signal is received through the channel, it is corrected using the decomposed post-processing matrix. Finally, each user gets an N*N channel.

[0039] 6. According to the above method, the target rate problem in the three dimensions of space domain, user domain and frequency domain is solved and reduced to a one-dimensional signal in the frequency domain;

[0040] 7. Under certain power constraints, according to the power bit allocation algorithm, power is adaptively allocated to different users in different frequency bands. After obtaining an optimal value allocation principle, the rate expression under OFDMA modulation is calculated.

[0041] Further, in step 4, the LED low-pass channel is considered in the three-dimensional system of multi-user MIMO-OFDMA. The LED low-pass channel is a special low-pass channel based on visible blue LED, which is described as:

[0042]

[0043] Furthermore, in step six, the frequency domain is first combined with the special channel characteristics of the visible blue LED, and then the SVD decomposition technique is used to reduce the spatial dimension of the multi-user MIMO-OFDMA into a separate SISO channel. Since each user uses a different frequency domain, this process reduces the three dimensions of the spatial domain, frequency domain and user domain to a one-dimensional frequency domain.

[0044] Furthermore, in step 7, the Lagrangian algorithm is used to adaptively allocate power to each frequency domain of the multi-user MIMO-OFDMA according to the channel conditions. The process is described as follows:

[0045] a. According to the above process, the multi-user MIMO-OFDMA model of the visible light is established as:

[0046]

[0047] Where M is the number of users, N is the number of spatial subchannels, and λ m,nn and P mn (f) are the singular values ​​and the power allocated to the mth channel of the nth user, respectively. N0 and Γ are the power spectral density of the noise and the signal-to-noise ratio gap, respectively. T is the total power; f m is the bandwidth range of the mth user, f c is the 3-dB cutoff frequency, B is the total signal bandwidth;

[0048] b. According to step 6, the system is reduced into a separate sub-channel for each user to perform power allocation only in the frequency domain;

[0049] c. According to the Lagrangian algorithm, the optimal solution of the above model can be obtained. With this model, we only need to calculate the optimal solution of the power and model the relevant solution as follows:

[0050]

[0051] d. Obtain the optimal solution based on the above model, and then adaptively allocate power to each frequency domain of multi-user MIMO-OFDMA according to the channel conditions.

[0052] A method for allocating multi-user MIMO-OFDMA communication resources based on visible light, the method realizes the allocation of multi-user MIMO-OFDMA communication resources based on visible light. The invention is based on Lagrangian technology and SVD decomposition technology, and realizes the allocation of the entire multi-user MIMO-OFDMA communication resources according to the system model of LED.

[0053] System Model

[0054] In this MIMO-OFDMA VLC system model, Figure 2 As shown in the figure, assuming that there are M users, each user has an N×N channel matrix, and using the SVD technology, the channel status of each user is divided into multiple independent sub-channels to obtain the channel state information about MIMO-OFDMA VLC. For a multi-user MIMO-OFDMA VLC system, assuming that the transmitted signal of the mth user is x(f)=[x1(f),x2(f),...,x N (f)] T , the received signal y m (f)=[y1(f),y2(f),...,y N (f)] T It can be expressed as:

[0055] y m (f) = H m (f)x(f)+n m (f) (4)

[0056] H m (f) represents the N×N MIMO matrix, n m (f)=[n1(f),n2(f),...,n N (f)] T is a Gaussian noise vector. Considering the same LED and PD in this experimental link, the above formula H m (f) can be expressed as: f c represents the 3dB bandwidth of the LED, and H(0) represents the DC gain of the MIMO channel, which can be expressed as:

[0057]

[0058] Where m = -ln2 / ln(cos(Ψ)) represents the Lambertian emission order, Ψ represents the half angle of the LED at half power, and d k,jiis the distance between the jth PD and the ith LED of the mth user. ρ and A represent the responsiveness and active area of ​​the PD, respectively. and θ k,ji are the exit angle and the incident angle j, G f and G l are the gains of the filter and the optical lens respectively.

[0059] Using SVD decomposition, H(0) is decomposed into multiple independent channels. The SVD decomposition diagram is as follows Figure 1 and Figure 3 As shown, the output expression can be obtained as follows:

[0060]

[0061] in U m , V m represents a unitary matrix.

[0062] Derivation of Throughput

[0063] According to the basic model of MIMO-OFDMA VLC and the basic theory of the above formula, the process is modeled:

[0064]

[0065] According to this model, the Lagrangian algorithm is used to find the extreme value, and the above model is established as:

[0066]

[0067] Because P T is a constant value. The above formula is reduced in dimension according to the theory, mainly converted into P mn (f) To find the extreme value, it can be expressed as:

[0068]

[0069] The above formula is Taking partial derivative, we can get P mn The expression of (f) is:

[0070]

[0071] in

[0072] Finally, the calculated rate is:

[0073]

[0074] Simulation and Results

[0075] The Lagrangian algorithm is used to adaptively allocate power to each frequency domain of multi-user MIMO-OFDMA according to the channel conditions. The process is described as follows:

[0076] 1. According to the above process, the system model is established as:

[0077]

[0078] Where M is the number of users, N is the number of spatial subchannels, and λ m,nn and P mn (f) are the singular values ​​and the power allocated to the mth channel of the nth user, respectively. N0 and Γ are the power spectral density of the noise and the signal-to-noise ratio gap, respectively. T is the total power; f m is the bandwidth range of the mth user, f c is the 3-dB cutoff frequency, and B is the total signal bandwidth.

[0079] 2. According to step 6, the system is reduced into a separate sub-channel for each user to perform power allocation only in the frequency domain;

[0080] 3. According to the Lagrangian algorithm, the optimal solution of the above model can be obtained. With this model, we only need to calculate the optimal solution of the power and model the relevant solution as follows:

[0081]

[0082] It can be seen from the above formula that the bandwidth range of each user is different. The final water injection line is determined according to the bandwidth range and channel status of each user. The water injection line of each user is not the same. The optimal power allocation for each channel is performed according to the power value calculated by the Lagrangian algorithm.

[0083] The key parameters of the transmitted multi-user MIMO-OFDMA signal are shown in Table 1.

[0084] Table 1 Key parameters of multi-user MIMO-OFDMA

[0085]

[0086]

[0087] According to the above results, we can get Figure 4 From the simulation result diagram, we can see that when the number of users increases, the rate of the entire system decreases. This is because we consider the low-pass characteristics of LEDs, and the state response of the channel at each frequency point is different.

[0088] According to formula (11), each user has the same bandwidth, but occupies a different bandwidth range. When there is only one user, one user enjoys the entire bandwidth range, but when there are multiple users, the position of each user is different, which leads to a poor channel state measured by the user in the corner. When this happens, the channel condition when two users share the bandwidth is not as good as the effect when one user enjoys the entire bandwidth alone. That is, when there are two users, the measured channel condition is discontinuous, so the rate obtained by the two users is not as high as the rate of one user.

[0089] Based on the same inventive concept as the above method embodiment, the embodiment of the present application also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the method for allocating multi-user MIMO-OFDMA communication resources based on visible light is implemented.

[0090] In several embodiments provided in the embodiments of the present invention, it should be understood that the disclosed apparatus and method can also be implemented in other ways. The apparatus and method embodiments described above are merely schematic. For example, the flowcharts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the apparatus, method and computer program product according to multiple embodiments of the present invention. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, program segment or a part of the code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, and the combination of boxes in the block diagram and / or flowchart can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0091] In addition, the functional modules in the various embodiments of the present invention may be integrated together to form an independent part, or each module may exist independently, or two or more modules may be integrated to form an independent part.

[0092] If the function is implemented in the form of a software function module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art or the part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions to enable a computer device (which can be a personal computer, an electronic device, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, RandomAccess Memory), a disk or an optical disk. It should be noted that, in this article, the term "include", "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements inherent to such a process, method, article or device. Without more constraints, an element defined by the phrase "comprising a..." does not exclude the existence of other identical elements in the process, method, article or apparatus comprising the element.

[0093] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0094] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0095] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0096] The "first\second" mentioned in the embodiments is only to distinguish similar objects, and does not represent a specific order for the objects. It is understandable that the "first\second" can be interchanged with the specific order or sequence where permitted. It should be understood that the objects distinguished by "first\second" can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than those illustrated or described herein.

[0097] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for allocating multi-user MIMO-OFDMA communication resources based on visible light, characterized in that: The steps include:

1. Assume that there are M users, and each user generates N data streams; 2. Map the data information stream into QAM symbols; 3. Convert the generated N-channel QAM symbols from serial data streams into parallel data streams, then modulate the parallel data into OFDM signals through IFFT in Hermitian symmetry, add cyclic prefixes to the modulated symbols, and convert them into serial data; 4. Perform multi-channel processing according to the pre-measured LED low-pass channel response, and pre-process the generated OFDM signal using the decomposed pre-processing matrix; 5. After the signal is received through the channel, it is corrected using the decomposed post-processing matrix. Finally, each user gets an N*N channel.

6. Reduce the target rate problem in three dimensions, namely, spatial domain, user domain and frequency domain, to a one-dimensional signal in the frequency domain; 7. Under certain power constraints, according to the power bit allocation algorithm, power is adaptively allocated to different users in different frequency bands. After obtaining an optimal value allocation principle, the rate expression under the OFDMA modulation method is calculated.

2. The method for allocating multi-user MIMO-OFDMA communication resources based on visible light according to claim 1, characterized in that: In step 4, the LED low-pass channel is a special low-pass channel based on visible blue LED, which is described as:

3. The method for allocating multi-user MIMO-OFDMA communication resources based on visible light according to claim 1, characterized in that: In step 4, the channel processing includes channel preprocessing, postprocessing and channel decomposition, and the generated OFDM signal is preprocessed with the preprocessing matrix after decomposition, and the preprocessed matrix expression is obtained by multiplying the two.

4. The method for allocating multi-user MIMO-OFDMA communication resources based on visible light according to claim 1, characterized in that: In step five, the correction is performed by multiplying the decomposed matrix by the post-processing matrix.

5. The method for allocating multi-user MIMO-OFDMA communication resources based on visible light according to claim 1, characterized in that: In steps 4 and 6, the frequency domain is first combined with the special channel characteristics of visible blue LEDs, and then the decomposition technology is used to reduce the MIMO channel of multi-user MIMO-OFDMA to a separate SISO channel; since each user uses a different frequency band, the decomposition technology is used to reduce the three dimensions of the spatial domain, frequency domain, and user domain to a one-dimensional frequency domain.

6. The method for allocating multi-user MIMO-OFDMA communication resources based on visible light according to claim 1, characterized in that: In step 7, the optimal value allocation principle is used to adaptively allocate power to each frequency domain of the multi-user MIMO-OFDMA according to the channel conditions. The process is described as follows: a. According to the optimal value allocation, the multi-user MIMO-OFDMA model of the visible light is established as: Where M is the number of users, N is the number of spatial subchannels, and λ m,nn and P mn (f) are the singular values ​​and the power allocated to the mth channel of the nth user, respectively. N0 and Γ are the power spectral density of the noise and the signal-to-noise ratio gap, respectively. T is the total power, f m is the bandwidth range of the mth user, f c is the 3-dB cutoff frequency, B is the total signal bandwidth; b. Reduce the system dimension into a separate sub-channel for each user to perform power allocation only in the frequency domain; c. To find the optimal solution for the above model according to the Lagrangian algorithm, we only need to calculate the optimal solution of the power and model the relevant solution as follows: d. Obtain the optimal solution according to the above formula, and then adaptively allocate power to each frequency domain of multi-user MIMO-OFDMA according to the channel conditions.

7. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed by a processor, the method for allocating multi-user MIMO-OFDMA communication resources based on visible light as described in any one of claims 1 to 6 is implemented.

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