Wireless optical communication system and method based on subarray and dynamic DC bias

Abstract

The present application discloses a wireless optical communication system and method based on subarrays and dynamic DC bias, which relates to the field of wireless communication technology. The wireless optical communication system based on subarrays and dynamic DC bias includes: a message splitting module splits a list of messages to be transmitted to obtain a public message list and a private message list; a message merging module merges public messages to obtain a merged public message; an encoder encodes the merged public message and the private message in the private message list respectively to obtain a public data stream and several private data streams; a signal sending module generates optical signals corresponding to the public data stream and each private data stream based on an LED subarray. Since the rate division multiple access scheme is combined with the optical communication system, and the subarray architecture and dynamically changing DC bias are adopted, the precoding energy efficiency when generating optical signals is improved.

Description

Technical Field

[0001] The present application relates to the field of wireless communication technology, and in particular to a wireless optical communication system and method based on subarrays and dynamic DC bias. Background Art

[0002] As an emerging communication technology, optical wireless communication (OWC) can combine the functions of lighting and communication, and has the advantages of wide spectrum, high speed and environmental protection. It is one of the main supporting technologies of 6G. OWC has a wide range of application scenarios, including ocean, land and air. In the marine environment, underwater wireless optical communication (UWOC) technology can use laser diodes (LD) or light emitting diodes (LED) for submarine data transmission and communication, and realize functions such as marine observation and geological exploration; in indoor and office places, visible light communication technology can use visible light for data transmission, and realize indoor positioning, data transmission and other functions; in air communication above the atmosphere, free space optical communication technology can use laser or infrared light for high-speed data transmission, which is used for drone communication, satellite communication and other applications; in space, deep space optical communication technology can use laser for high-speed data transmission between satellites and between satellites and ground stations, which is used in earth observation, satellite communication and other fields.

[0003] Since the modulation bandwidth of the single-light-source OWC communication system is limited and the service range of lighting communication is limited, it is difficult to provide high-speed, multi-access services. Therefore, multi-input multi-output (MIMO) technology is often used in wireless optical communication to achieve spatial diversity and spatial multiplexing, thereby improving the efficiency of the optical communication system. OWC-MIMO systems usually use LD or LED as light sources. The large divergence angle of LED light sources helps to expand the communication coverage, alleviate link alignment problems, and is easy to integrate into compact OWC-MIMO systems. At the same time, LED light sources have the advantage of realizing the integration of lighting and communication. Therefore, traditional OWC-MIMO systems usually use LED as light sources and adopt low-cost, low-complexity intensity modulation / direct detection (IM / DD) technology. However, the power overhead of OWC-MIMO systems using IM / DD technology is large and is often used in power-constrained scenarios. It is urgent to propose a low-power OWC-MIMO communication system design solution. Summary of the invention

[0004] The main purpose of this application is to provide a wireless optical communication system and method based on subarrays and dynamic DC bias, aiming to solve the technical problem that the OWC-MIMO system using IM / DD technology has a large power overhead and is often used in power consumption-constrained scenarios.

[0005] To achieve the above-mentioned object, the present application proposes a wireless optical communication system based on a subarray and a dynamic DC bias, wherein the wireless optical communication system based on a subarray and a dynamic DC bias comprises at least: a signal transmitting end;

[0006] The signal sending end includes: a message splitting module, a message merging module, an encoder and a signal sending module;

[0007] The message splitting module is connected to the message merging module and the encoder respectively, the message merging module is also connected to the encoder, the encoder is also connected to the signal sending module, and the signal sending module includes an LED subarray;

[0008] The message splitting module is used to split the message list to be transmitted to obtain a public message list and a private message list;

[0009] The message merging module is used to merge the public messages in the public message list to obtain a merged public message;

[0010] The encoder is used to encode the merged public message and the private messages in the private message list respectively to obtain a public data stream and a plurality of private data streams;

[0011] The signal sending module is used to generate optical signals corresponding to the public data stream and each of the private data streams based on the LED sub-array.

[0012] In one embodiment, the signal transmission module includes: a baseband precoder, a baseband chain, a DC bias controller and an LED subarray;

[0013] Wherein, the encoder is connected to the baseband precoder;

[0014] The baseband precoder is also connected to a plurality of baseband chains, each of which is connected to a corresponding LED sub-array;

[0015] The DC bias controller is connected to each of the LED sub-arrays;

[0016] The baseband precoder is used to independently encode and linearly superpose the public data stream and each of the private data streams based on a baseband precoding matrix to obtain a precoded mixed data stream;

[0017] The DC bias controller is used to generate a DC bias vector;

[0018] The LED sub-array is used to generate an optical signal based on the precoded mixed data stream and the DC bias vector.

[0019] In one embodiment, the DC bias controller is also connected to the encoder;

[0020] The DC bias controller is further used to determine a dynamic DC bias based on a data stream and a DC control matrix; the data stream is the public data stream and the private data stream;

[0021] The DC bias controller is further used to obtain a static DC bias, and generate a DC bias vector based on the dynamic DC bias and the static DC bias.

[0022] In one embodiment, the wireless optical communication system is further used to determine a private data rate corresponding to the private data flow;

[0023] The wireless optical communication system is further used to determine a public data rate corresponding to a public data stream;

[0024] The wireless optical communication system is also used to determine the receiving end combined rate based on the public data rate and the private data rate.

[0025] In one embodiment, the system further comprises: a signal receiving end;

[0026] The signal receiving end is used to receive the optical signal sent by the signal sending end;

[0027] The signal receiving end is further used to convert the optical signal into an electrical signal and filter out the DC bias vector in the electrical signal to obtain a received signal;

[0028] The signal receiving end is further used to parse the public signal part in the received signal to determine the public data stream;

[0029] The signal receiving end is further used to filter out the public signal part in the received signal and then parse it again to determine the private data stream;

[0030] The wireless optical communication system is further used to parse the public signal part in the received signal to determine the initial public data rate corresponding to the public data flow;

[0031] The wireless optical communication system is also used to obtain actual rate constraints of the public data flow;

[0032] The wireless optical communication system is further used to determine an actual public data rate based on the actual rate constraint condition and the initial public data rate.

[0033] In one embodiment, the wireless optical communication system based on subarrays and dynamic DC bias is further used to use system transmit power consumption as a constraint model of the system;

[0034] The subarray- and dynamic DC bias-based wireless optical communication system is also used to solve the constraint model through a continuous convex approximation method to obtain a baseband precoding matrix and a DC control matrix.

[0035] In addition, to achieve the above-mentioned purpose, the present application also proposes a wireless optical communication method based on a subarray and a dynamic DC bias, the method being applied to the wireless optical communication system based on a subarray and a dynamic DC bias as described above, the wireless optical communication method based on a subarray and a dynamic DC bias comprising:

[0036] The message splitting module splits the message list to be transmitted to obtain a public message list and a private message list;

[0037] The message merging module merges the public messages in the public message list to obtain a merged public message;

[0038] The encoder encodes the merged public message and the private messages in the private message list respectively to obtain a public data stream and a plurality of private data streams;

[0039] The signal sending module generates optical signals corresponding to the public data stream and each of the private data streams based on the LED sub-array.

[0040] In one embodiment, the step of the signal sending module generating the optical signals corresponding to the public data stream and each of the private data streams based on the LED sub-array includes:

[0041] The baseband precoder independently encodes and linearly superimposes the public data stream and each of the private data streams based on a baseband precoding matrix to obtain a precoded mixed data stream;

[0042] The DC bias controller generates a DC bias vector;

[0043] The LED sub-array generates an optical signal based on the precoded mixed data stream and the DC bias vector.

[0044] In one embodiment, the step of generating a DC bias vector by the DC bias controller comprises:

[0045] The DC bias controller determines a dynamic DC bias based on a data stream and a DC control matrix; the data stream is the public data stream and the private data stream;

[0046] The DC bias controller obtains a static DC bias, and generates a DC bias vector based on the dynamic DC bias and the static DC bias.

[0047] In one embodiment, the method further comprises:

[0048] The signal receiving end receives the optical signal sent by the signal sending end;

[0049] The signal receiving end converts the optical signal into an electrical signal, and filters out a DC bias vector in the electrical signal to obtain a received signal;

[0050] The signal receiving end analyzes the public signal part in the received signal to determine the public data stream;

[0051] The signal receiving end filters out the public signal part in the received signal and then performs analysis again to determine the private data stream;

[0052] The wireless optical communication system determines a private data rate corresponding to the private data stream;

[0053] The wireless optical communication system determines a public data rate corresponding to a public data flow;

[0054] The wireless optical communication system determines a receiving end combined rate based on the public data rate and the private data rate.

[0055] One or more technical solutions proposed in this application have at least the following technical effects:

[0056] The wireless optical communication system based on subarray and dynamic DC bias of the present application at least includes: a signal transmitting end; the signal transmitting end includes: a message splitting module, a message merging module, an encoder and a signal transmitting module; wherein the message splitting module is respectively connected to the message merging module and the encoder, the message merging module is also connected to the encoder, the encoder is also connected to the signal transmitting module, and the signal transmitting module includes an LED subarray; the message splitting module splits the message list to be transmitted to obtain a public message list and a private message list; the message merging module merges the public messages in the public message list to obtain a merged public message; the encoder encodes the merged public message and the private message in the private message list respectively to obtain a public data stream and several private data streams; the signal transmitting module generates optical signals corresponding to the public data stream and each private data stream based on the LED subarray. Since the rate division multiple access scheme is combined with the optical communication system, and the subarray architecture and the dynamically changing DC bias are adopted, the precoding energy efficiency when generating the optical signal is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0058] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0059] Figure 1 A schematic diagram of the overall structure of the first embodiment of the wireless optical communication system based on subarrays and dynamic DC bias of the present application;

[0060] Figure 2-1 This is a comparison chart of transmit power consumption under different receiver SNR conditions;

[0061] Figure 2-2 for Figure 2-1 Enlarged comparison picture of part A in the middle;

[0062] Figure 3-1 This is a comparison chart of energy efficiency under different receiving end SNR conditions;

[0063] Figure 3-2 for Figure 3-1 Enlarged comparison picture of part B;

[0064] Figure 4-1 The figure is a comparison of energy efficiency between non-subarray architecture and subarray architecture;

[0065] Figure 4-2for Figure 4-1 Enlarged comparison picture of part C in the middle;

[0066] Figure 5 It is a graph showing the objective function changing with the number of iterations;

[0067] Figure 6 A schematic flow chart of an embodiment of a wireless optical communication method based on subarrays and dynamic DC bias is provided for the present application.

[0068] The purpose, features and advantages of this application will be further described in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0069] It should be understood that the specific embodiments described herein are only used to explain the technical solutions of the present application and are not used to limit the present application.

[0070] In order to better understand the technical solution of the present application, a detailed description will be given below in conjunction with the accompanying drawings and specific implementation methods.

[0071] The embodiment of the present application proposes a low-power OWC-MIMO subarray architecture with adjustable direct current bias (DC-Bias), introduces a rate-splitting multiple access (RSMA) scheme into the subarray architecture, and designs a high-energy-efficiency OWC-MIMO subarray precoding scheme with adjustable DC bias, which effectively reduces energy consumption and improves the energy efficiency (EE) of the system.

[0072] In the OWC-MIMO system using IM / DD technology, the transmitted signal must satisfy the positive real number characteristic, and can only modulate the amplitude of the optical signal, but not the phase. For example, amplitude modulation techniques such as pulse amplitude modulation (PAM) can be used. Therefore, under the same modulation order and symbol interval, the average symbol power of the IM / DD system may be larger than the average symbol power of the coherent communication system, resulting in greater transmit power consumption. At the same time, for the OWC-MIMO system, although MIMO can use the spatial domain to implement coding to increase the communication rate, the introduction of MIMO will also introduce a large hardware overhead. Each light source in the MIMO system must be equipped with a baseband link, on which digital-to-analog converters (DACs), power amplifiers (PAs) and other devices are integrated, which will undoubtedly introduce a large hardware power consumption for densely deployed multi-light source systems. In addition, in optical communication scenarios such as underwater wireless optical communication and optical sensor networks (OSN), due to special environmental constraints, the optical communication system only relies on batteries for power supply. Therefore, the power consumption of the system is the key to determining whether the system can work efficiently.

[0073] The present application provides a solution. In the OWC-MIMO subarray system architecture with adjustable DC bias, each baseband link connects the same number of LED subarrays and provides communication services for multiple receiving ends at the same time. A DC bias control link is introduced at the baseband to provide a dynamic DC level that changes adaptively with the input signal for the input of the LED subarray. Compared with the solution of the prior art that uses a fixed amplification factor, the solution of the present application does not require regulation of the power amplifier. At the same time, the present application proposes a more energy-efficient precoding solution by combining the rate-splitting multiple access (RSMA) solution with a subarray architecture with adjustable DC bias.

[0074] Based on this, the embodiment of the present application provides a wireless optical communication system based on a subarray and a dynamic DC bias (hereinafter referred to as the present system), referring to Figure 1 , Figure 1 A schematic diagram of the overall structure of Embodiment 1 of the wireless optical communication system based on subarrays and dynamic DC bias is provided for the present application.

[0075] In the wireless optical communication system based on subarrays and dynamic DC bias of the present application, a signal transmitting end and a signal receiving end of an optical signal may be included. The above-mentioned signal transmitting end adopts the OWC-MIMO subarray system architecture with adjustable DC bias proposed in the present application, thereby achieving the purpose of reducing system power consumption and improving system energy efficiency. At the same time, the present application also designs a highly energy-efficient OWC-MIMO subarray precoding scheme, which achieves more energy-efficient precoding by combining the Rate-Splitting Multiple Access (RSMA) scheme with a subarray architecture with adjustable DC bias.

[0076] Specifically, the signal sending end includes: a message splitting module, a message merging module, an encoder and a signal sending module;

[0077] The message splitting module is connected to the message merging module and the encoder respectively, the message merging module is also connected to the encoder, the encoder is also connected to the signal sending module, and the signal sending module includes an LED subarray;

[0078] The message splitting module is used to split the message list to be transmitted to obtain a public message list and a private message list;

[0079] The message merging module is used to merge the public messages in the public message list to obtain a merged public message;

[0080] The encoder is used to encode the merged public message and the private messages in the private message list respectively to obtain a public data stream and a plurality of private data streams;

[0081] The signal sending module is used to use the public data stream and each of the private data streams as inputs of the LED sub-array to obtain a light signal.

[0082] It can be understood that rate division multiple access is a wireless multiple access technology that divides information into a public information part and a private information part, where the public part is encoded and broadcast to all receiving ends, and the private information is encoded and transmitted separately for each receiving end. Nt An LED light source equipped with an LED sub-array, U A signal receiving end equipped with a single photodiode (PD). At the same time, the transceiver can meet the conditions Nt Much greater than U .

[0083] In one implementation of the embodiment of the present application, the light source equipped at the signal transmitting end may also be a xenon lamp, an argon ion laser, an incandescent bulb, a fluorescent tube, etc. other than an LED light source, and the embodiment of the present application does not limit this. At the same time, in the present application, a certain divergence angle is required between the light source at the signal transmitting end and the optical receiver at the signal receiving end in order to realize MIMO space division multiplexing.

[0084] In the embodiment of the present application, it can be set Nt The list of messages to be transmitted by the LED light sources at the same time includes U Messages , and set the message For the u The message splitting module can be used to treat the messages in the transmission message list as Split to obtain a public message list and a private message list, where the public message list includes public messages , the private message list includes private messages .

[0085] Furthermore, the public message can be merged into a message merger module. Perform a merge and generate a merge public message The encoder can be used to merge public messages Encode and generate a public data stream. At the same time, private messages Can be independently encoded by the encoder U Private data stream . Through the signal sending module, based on the LED sub-array generation U +1 optical signal corresponding to the data stream.

[0086] In one implementation of the embodiment of the present application, in order to achieve signal regulation, the signal sending module includes: a baseband precoder, a baseband chain, a DC bias controller and an LED subarray;

[0087] Wherein, the encoder is connected to the baseband precoder;

[0088] The baseband precoder is also connected to a plurality of baseband chains, each of which is connected to a corresponding LED sub-array;

[0089] The DC bias controller is connected to each of the LED sub-arrays;

[0090] The baseband precoder is used to independently encode and linearly superpose the public data stream and each of the private data streams based on a baseband precoding matrix to obtain a precoded mixed data stream;

[0091] The DC bias controller is used to generate a DC bias vector;

[0092] The LED sub-array is used to generate an optical signal based on the precoded mixed data stream and the DC bias vector.

[0093] It can be understood that the above-mentioned baseband link, that is, the baseband link in the MIMO system, can connect the baseband processing unit and the optical communication transceiver front end to achieve signal transmission.

[0094] It should be understood that the above baseband precoder is a component that can precode input data. The baseband precoding matrix of the baseband precoder can independently encode and linearly superimpose the public data stream and each private data stream to obtain a precoded mixed data stream. Nc The baseband chain is delivered to the corresponding LED sub-array.

[0095] In the embodiment of the present application, the number of enabled baseband chains and LED sub-arrays can be set to Nc , each LED sub-array is connected to only one baseband chain, and the number of LEDs controlled by each LED sub-array can be By connecting a DC bias control link between the baseband chain and the LED sub-array, the LED sub-array provides a regulated DC bias. For the sake of generality, in the embodiments of the present application, it can be assumed that the signal transmitting end knows perfect channel state information (CSI).

[0096] It should be noted that the baseband can apply the corresponding DC level to different LED sub-arrays through the DC bias control link. Based on this, the signal sent by the LED sub-array for:

[0097] ;

[0098] in, is a precoding matrix with block diagonalization property, is the DC bias vector, It is the sending data stream (including public data stream and private data stream). The transmission symbols in the data stream are assumed to be random variables following a certain distribution, which are normalized to the interval [-1,1], with a mean of zero and a variance of .

[0099] It can be understood that by introducing an adaptively adjusted DC bias vector, the problem that the transmitted optical signal may suffer from amplitude distortion and thus cause degradation of signal quality can be improved.

[0100] In one implementation of the embodiment of the present application, the DC bias controller is also connected to the encoder;

[0101] The DC bias controller is further used to determine a dynamic DC bias based on a data stream and a DC control matrix; the data stream is the public data stream and the private data stream;

[0102] The DC bias controller is further used to obtain a static DC bias, and generate a DC bias vector based on the dynamic DC bias and the static DC bias.

[0103] It should be noted that, in the embodiment of the present application, the DC bias controller is connected to the encoder and the LED sub-array respectively. In this embodiment, the DC bias vector d generated by the DC bias controller can be divided into a dynamic control part (i.e., a dynamic DC bias): ( Figure 1 The shown ones include d1, d2, ...d M , d M（Nc-1）+1 ,d M（Nc-1）+2 ,…,d MNc ) and the constant part (i.e. static DC bias) Among them, the dynamic DC bias is related to the transmission data flow x Related, can be determined by the DC control matrix at baseband Regulation can be specifically expressed as ; The static DC bias has nothing to do with the transmitted data stream and is used to ensure the light transmission requirements of the LED sub-array. Therefore, for the generated DC bias vector d The following conditions must be met:

[0104] .

[0105] It should be noted that, according to the architecture mode of the subarray, the precoding matrix Expressed as ,in is the baseband precoding matrix, It is the connection matrix between the baseband chain and the LED sub-array, which can be shown as follows:

[0106]

[0107] It is understandable that the resulting optical signal s It can be expressed as:

[0108] .

[0109] The wireless optical communication system based on subarray and dynamic DC bias in the embodiment of the present application at least includes: a signal transmitting end; the signal transmitting end includes: a message splitting module, a message merging module, an encoder and a signal transmitting module; wherein the message splitting module is respectively connected to the message merging module and the encoder, the message merging module is also connected to the encoder, the encoder is also connected to the signal transmitting module, and the signal transmitting module includes an LED subarray; the message splitting module splits the message list to be transmitted to obtain a public message list and a private message list; the message merging module merges the public messages in the public message list to obtain a merged public message; the encoder encodes the merged public message and the private message in the private message list respectively to obtain a public data stream and several private data streams; the signal transmitting module generates optical signals corresponding to the public data stream and each private data stream based on the LED subarray. Since the rate division multiple access scheme is combined with the optical communication system, the subarray architecture and the dynamically changing DC bias are adopted at the same time, which improves the precoding energy efficiency when generating optical signals.

[0110] Based on the first embodiment of the present application, in the second embodiment of the present application, the same or similar contents as those in the above-mentioned embodiment 1 can be referred to the above introduction, and will not be described in detail later. On this basis, the channel model in the present application can be represented based on the following description.

[0111] The channel matrix from the signal transmitter to the signal receiver can be set as ,in It is U The channel gain vector at the receiving end.

[0112] It is worth noting that the channel characteristics of the wireless optical communication system based on subarrays and dynamic DC bias are significantly different from the radio channel model. The traditional radio transmission channel model usually adopts a multipath propagation model. The signal from the transmitter to the receiver will experience reflection, refraction and diffraction of multiple paths, resulting in diversity in the time and phase of the signal arriving at the receiver. Therefore, the radio channel can be modeled as a complex signal transmission path containing the main path and multipath. The traditional radio channel model can be expressed as:

[0113] ;

[0114] in, For path i The complex attenuation coefficient of N is the number of paths, It is a delay The impulse function at is the phase term, is the carrier frequency.

[0115] It should be noted that compared with radio transmission, the multipath effect in wireless optical communication is relatively small, and the main propagation path is line-of-sight. Since the non-negative real signal characteristics of optical signals are reflected in IM / DD systems, the optical channel only has amplitude attenuation but no phase fading. In addition, the channel characteristics are closely related to the distribution characteristics of the light source and optical receiver as well as the characteristics of the optical device.

[0116] In the embodiment of the present application, the wireless optical communication system is further used to determine the public data rate corresponding to the public data flow;

[0117] The wireless optical communication system is further used to determine a private data rate corresponding to the private data stream;

[0118] The wireless optical communication system is also used to determine a receiving end combined rate based on the public data rate and the private data rate.

[0119] It should be noted that the signal receiving end can convert the received optical signal into an electrical signal and filter out the constant DC bias therein. When filtered out, the received optical signal can be expressed as: ; where n is the power The additive Gaussian white noise vector is , and H is the channel matrix. U The received signal at the receiving end It can be expressed as the superposition of public signal, private signal, interference signal and noise. Specifically:

[0120] ;

[0121] in, Indicates the public signal part, Represents the private signal part, represents the interference signal part, Represents the noise part.

[0122] Furthermore, the receiving end When the public signal part is decoded, the public signal part can be decoded and then received by The private signal part is decoded by subtracting the interference caused by the public signal part from the private signal part. Therefore, the wireless optical communication system can determine the U The signal-to-interference-plus-noise ratio (SINR) of the public signal at the signal receiving end is:

[0123] ;

[0124] Accordingly, the wireless optical communication system can determine the signal receiving end U Public data streams atx0 The public data rates are:

[0125] ;

[0126] It should be noted that due to the public data flow x0 Received by all signal receiving ends and must be guaranteed to be decoded by all signal receiving ends, so the public data stream x0 The actual public data rate needs to meet the following actual rate constraints:

[0127] ;

[0128] ;

[0129] in, Indicates U The signal receiving end is assigned a common message rate that satisfies The above two constraints can be combined to obtain the following constraints:

[0130] .

[0131] It can be understood that after the signal receiving end successfully decodes and subtracts the public signal, the private signal, the interference signal and the noise part remain in the received signal. The wireless optical communication system can further determine the signal-to-noise ratio of the private signal as:

[0132] .

[0133] Accordingly, the signal receiving end U The private data rate at can be expressed as:

[0134] .

[0135] It can be understood that the signal receiving end can be determined based on the public data rate and the private data rate. U The total achievable combined rate (i.e., the combined rate at the receiving end) is:

[0136] .

[0137] In the embodiment of the present application, the system also includes: a signal receiving end; the signal receiving end receives the optical signal sent by the signal sending end; the signal receiving end converts the optical signal into an electrical signal, and filters out the DC bias vector in the electrical signal to obtain a received signal; the signal receiving end analyzes the public signal part in the received signal to determine the public data stream; the signal receiving end filters out the public signal part in the received signal and analyzes it again to determine the private data stream; the wireless optical communication system determines the public data rate corresponding to the public data stream and the private data rate corresponding to the private data stream; the wireless optical communication system determines the combined rate of the receiving end based on the public data rate and the private data rate. Since the public data rate of the signal receiving end is constrained, all receiving ends can receive the public signal.

[0138] Based on the first embodiment and / or the second embodiment of the present application, in the third embodiment of the present application, the same or similar contents as those in the first embodiment and / or the second embodiment can be referred to the above description, and will not be described in detail later. On this basis, in the embodiment of the present application, the wireless optical communication system based on subarrays and dynamic DC bias is also used to use the system transmission power consumption as a constraint model of the system;

[0139] The subarray- and dynamic DC bias-based wireless optical communication system is also used to solve the constraint model through a continuous convex approximation method to obtain a baseband precoding matrix and a DC control matrix.

[0140] Based on the above embodiments, it can be seen that the precoding matrix in this application is determined based on the baseband precoding matrix and the data stream. Therefore, in order to meet the user rate requirements and LED constraints, it is necessary to design an efficient baseband precoding matrix W and a DC bias d, so as to minimize the system's transmit power consumption, thereby improving the system's energy efficiency. In the embodiment of the present application, a constraint model is constructed by taking the system's transmit power consumption as the system's optimization target, and the model is solved using convex optimization knowledge.

[0141] Specifically, the objective function optimized in this application is the system's transmit power consumption The current from driving the LED sub-array can be expressed as:

[0142]

[0143] Among them, r is the current of the AC circuit. From the above, we can see that Under the premise of constant, the transmission power consumption is only related.

[0144] It should be noted that in order to alleviate U The interference between the receiving ends, the embodiment of the present application sets the baseband precoder W so that UThe power of the interference signal received by the receiving end is reduced to 0, that is, the following conditions are met:

[0145] ;

[0146] Furthermore, in order to ensure the quality of service requirements of the signal receiving end, the minimum achievable rate of the receiving end can be set to , that is, satisfying:

[0147] ;

[0148] At this time, in order to ensure that the amplitude range of the emitted light signal s is within the dynamic range of the LED sub-array [ Imin , Imax ], the following conditions must be met: ;

[0149] Furthermore, the above formula can be derived as:

[0150] .

[0151] In addition, since the DC bias vector d of the wireless optical communication system is limited by the relevant control devices, its amplitude needs to be controlled in [0, I 0], the following conditions must be met: ; It can be further deduced as: .

[0152] Finally, combined with the actual rate constraints and , the constraint model can be expressed as:

[0153]

[0154] It is understandable that the optimization problem of the above constraint model is a complex non-convex optimization problem with multiple non-convex constraints and the optimization variables are entangled with each other. The present invention adopts a continuous convex approximation solution method to solve this non-convex problem, and the solution is to reconstruct the original problem into a typical convex optimization problem.

[0155] Specifically, a new optimization variable is introduced , and define the parameter matrix , , ; Among them, the parameter matrix The nth element in is 1, is an N×N identity matrix. Then the original optimization variables W and X can be expressed as , ; The original optimization model can be re-expressed as:

[0156]

[0157] Furthermore, in order to simplify the above expression, the parameter matrix can be defined as , , , Based on this, the above optimization problem can be further expressed as:

[0158]

[0159] Furthermore, in the above constraint model, except for the second and third constraints, the remaining constraints and objective functions are convex functions. In order to solve the problem smoothly, representative variables can be introduced. and Two sets of slack variables and Therefore, the second and third constraints above can be equivalent to:

[0160]

[0161]

[0162] Furthermore, considering that the above constraints contain logarithmic functions and fractional forms, slack variables can be introduced , and , the above constraints can be further transformed into:

[0163]

[0164]

[0165] It should be noted that, among the above constraints, in addition to the constraint and Except for , the rest are convex functions.

[0166] In order to solve these two non-convex constraints, this application adopts a linear approximation method to transform the non-convex constraints into convex constraints, and uses an iterative method to obtain the asymptotic optimal solution to the problem. Specifically, Can be local is approximated to first order by:

[0167]

[0168] Among them, the superscript ( i ) indicates the i The value of the variable at iteration .

[0169] Can be local The first-order approximation is:

[0170]

[0171] Based on the above, the original optimization problem and the corresponding constraint model can be reformulated as i The approximate problem at iterations is:

[0172]

[0173]

[0174] It can be seen that the approximation problem is a convex problem. i The CVX toolbox can be used to solve the problem in the iteration, and the asymptotic optimal solution of the original problem can be obtained through iterative approximation. x and . Correspondingly, the baseband precoding matrix can be obtained as , the DC control matrix is .

[0175] It can be understood that the CVX toolbox is a toolbox designed to solve convex optimization problems. It converts convex optimization problems into standard forms and then solves them through built-in optimization algorithms.

[0176] It should be noted that when determining the baseband precoding matrix and DC bias, the transmission power consumption and energy efficiency of the system can be determined to verify the effectiveness of the solution. Specifically, for a wireless optical communication system based on a subarray and dynamic DC bias, its performance evaluation indicators may include: the system's transmission power (determined based on the above), the total power consumption to the signal transmission point, , which can be expressed as .in, is the AC current power, is the DC current power. The DC current power includes the lighting power for the LED sub-array , the power consumed by the digital-to-analog converter DAC and the power amplifier PA , , and control the dynamic DC bias The power used by other components . It can be specifically expressed as:

[0177] ;

[0178] in, It can be expressed as:

[0179] ;

[0180] is the forward voltage of the LED sub-array, AC power The current from driving the LED sub-array is equal to the system's transmit power consumption , which can be expressed as:

[0181] ;

[0182] definition is the equivalent resistance, and the total power consumption of the final system is expressed as:

[0183] ;

[0184] It should be noted that the energy efficiency of the system , which can be defined as the total spectral efficiency of the system The ratio to the total power consumption of the system can be expressed as:

[0185] (bps / Hz / W);

[0186] Among them, the total spectrum efficiency It can be expressed as:

[0187]

[0188] The embodiment of the present application establishes a system constraint model based on the system transmission power consumption, and iterates based on the system constraint model to determine the baseband precoding matrix and the DC control matrix for controlling the dynamic DC bias, thereby realizing the design of the baseband precoder. The baseband precoder in the present application precodes the public data stream and the private data stream to be sent, and determines the dynamic DC bias through the DC control matrix, thereby improving the system energy efficiency.

[0189] In the embodiment of the present application, Figure 2-1 , Figure 2-2 , Figure 3-1 , Figure 3-2 , Figure 4-1 and Figure 4-2 The present invention demonstrates the changing trends of transmission power consumption and energy efficiency under different receiving-end signal-to-noise ratio (SNR) conditions in a subarray architecture with adjustable DC bias and a non-subarray (fully connected) architecture, compared with a spatial division multiple access (SDMA) precoding scheme and a serial interference cancellation (SIC) precoding scheme.

[0190] Reference Figure 2-1 and Figure 2-2 , Figure 2-1 This is a comparison chart of the transmit power consumption under different receiving end SNR conditions. Figure 2-2 for Figure 2-1 Enlarged comparison image of part A. Figure 2-1 and Figure 2-2 The horizontal axis represents SNR in dB; the vertical axis represents the transmit power consumption , unit is W. Figure 2-2 The precoding schemes represented by the various types of legends are Figure 2-1 The precoding schemes represented by the various types of legends are the same (the yellow solid line of transmit power consumption changes represent the transmit power consumption changes corresponding to the SDMA precoding scheme adopted by the sub-array architecture, where the diamonds represent the sampling points corresponding to different horizontal coordinates; the blue solid line of transmit power consumption changes represent the transmit power consumption changes corresponding to the SIC precoding scheme adopted by the sub-array architecture, where the triangles represent the sampling points corresponding to different horizontal coordinates; the red solid line of transmit power consumption changes represent the transmit power consumption changes corresponding to the RSMA precoding scheme adopted by the sub-array architecture, where the circles represent the sampling points corresponding to different horizontal coordinates), as shown in Figure 2-1 and Figure 2-2 As shown, under the same receiving end SNR conditions, compared with the SDMA precoding scheme and the SIC precoding scheme under the array architecture, the transmission power of the present application is always kept at the lowest level, with significant energy-saving characteristics. As the SNR increases, the energy-saving advantage of the present application will gradually expand.

[0191] Reference Figure 3-1 and Figure 3-2 , Figure 3-1 This is a comparison chart of energy efficiency under different receiving end SNR conditions. Figure 3-2 for Figure 3-1 Enlarged comparison picture of part B; Figure 3-1 and Figure 3-2 In the figure, the horizontal axis represents SNR in dB, and the vertical axis represents system energy efficiency EE in bps / Hz / W. Figure 3-2 The precoding schemes represented by the various types of legends are Figure 3-1 The precoding schemes represented by the various types of legends are the same (the energy efficiency change of the yellow solid line represents the change in transmit power consumption corresponding to the SDMA precoding scheme adopted by the sub-array architecture, where the diamonds represent the sampling points corresponding to different horizontal coordinates; the energy efficiency change of the blue solid line represents the change in transmit power consumption corresponding to the SIC precoding scheme adopted by the sub-array architecture, where the triangles represent the sampling points corresponding to different horizontal coordinates; the energy efficiency change of the red solid line represents the change in transmit power consumption corresponding to the RSMA precoding scheme adopted by the sub-array architecture, where the circles represent the sampling points corresponding to different horizontal coordinates). Figure 3-1 and Figure 3-2 As shown in the figure, under the same receiving end SNR conditions, the energy efficiency of the present application is always better than the SDMA precoding scheme and the SIC precoding scheme under the subarray architecture. As the SNR increases, the energy efficiency of all schemes shows a trend of first increasing and then decreasing, and the present scheme reaches the peak energy efficiency when the SNR is about 25dB.

[0192] Reference Figure 4-1 and Figure 4-2 , Figure 4-1 This is a comparison chart of energy efficiency between non-subarray architecture and subarray architecture. Figure 4-2 for Figure 4-1 Enlarged comparison picture of part C in the middle; Figure 4-1 and Figure 4-2 The horizontal axis represents SNR in dB, and the vertical axis represents system energy efficiency EE in bps / Hz / W. Figure 4-2 The architecture types and precoding schemes represented by the various types of legends in Figure 4-1 The legends of each type are the same (the energy efficiency change of the yellow solid line represents the change in transmit power consumption corresponding to the SDMA precoding scheme adopted by the sub-array architecture, where the diamonds represent the sampling points corresponding to different horizontal coordinates; the energy efficiency change of the blue solid line represents the change in transmit power consumption corresponding to the SIC precoding scheme adopted by the sub-array architecture, where the triangles represent the sampling points corresponding to different horizontal coordinates; the energy efficiency change of the red solid line represents the change in transmit power consumption corresponding to the RSMA precoding scheme adopted by the sub-array architecture, where the circles represent the sampling points corresponding to different horizontal coordinates; the energy efficiency change of the yellow dotted line represents the change in transmit power consumption corresponding to the SDMA precoding scheme adopted by the fully connected architecture, where the diamonds represent the sampling points corresponding to different horizontal coordinates; the energy efficiency change of the blue dotted line represents the change in transmit power consumption corresponding to the SIC precoding scheme adopted by the fully connected structure, where the triangles represent the sampling points corresponding to different horizontal coordinates; the energy efficiency change of the red dotted line represents the change in transmit power consumption corresponding to the RSMA precoding scheme adopted by the fully connected architecture, where the circles represent the sampling points corresponding to different horizontal coordinates). Figure 4-1 and Figure 4-2 As shown in the figure, when the signal-to-noise ratio at the receiving end is lower than 40dB, the energy efficiency of the subarray architecture of the present application is significantly higher than that of the precoding scheme of the non-subarray architecture (i.e., the fully connected architecture), because the hardware power consumption of the subarray architecture is smaller and more energy-efficient. Under these two architectures, the energy efficiency of the present application is better than the other two precoding schemes. However, when the signal-to-noise ratio at the receiving end is greater than 40dB, Figure 4-2 The curve in the small window shows that the energy efficiency of the non-subarray architecture gradually exceeds that of the subarray architecture. This is because the adjustable DC bias in the subarray architecture is restricted by the control device and its amplitude is limited, resulting in some performance loss.

[0193] Reference Figure 5 , Figure 5 It is a graph showing the objective function changing with the number of iterations, where the horizontal axis represents the number of iterations and the vertical axis represents the value of the objective function. Figure 5As shown, after about 5 iterations, the value of the objective function of the solution provided by the present application tends to be stable, showing convergence characteristics. This shows that the solution proposed by the present application not only has excellent performance, but also presents a high level of solution efficiency.

[0194] The present application also provides a wireless optical communication method based on subarray and dynamic DC bias, please refer to Figure 6 , Figure 6 A flow chart of an embodiment of a wireless optical communication method based on a subarray and dynamic DC bias is provided for this application. The wireless optical communication method comprises:

[0195] Step S10, the message splitting module splits the message list to be transmitted to obtain a public message list and a private message list;

[0196] Step S20, the message merging module merges the public messages in the public message list to obtain a merged public message;

[0197] Step S30, the encoder encodes the merged public message and the private messages in the private message list respectively to obtain a public data stream and a plurality of private data streams;

[0198] Step S40: the signal sending module generates optical signals corresponding to the public data stream and each of the private data streams based on the LED sub-array.

[0199] In an implementation of the embodiment of the present application, the step of the signal sending module generating the optical signals corresponding to the public data stream and each of the private data streams based on the LED sub-array includes:

[0200] The baseband precoder independently encodes and linearly superimposes the public data stream and each of the private data streams based on a baseband precoding matrix to obtain a precoded mixed data stream;

[0201] The DC bias controller generates a DC bias vector;

[0202] The LED sub-array generates an optical signal based on the precoded mixed data stream and the DC bias vector.

[0203] In an implementation of the embodiment of the present application, the step of generating a DC bias vector by the DC bias controller includes:

[0204] The DC bias controller determines a dynamic DC bias based on a data stream and a DC control matrix; the data stream is the public data stream and the private data stream;

[0205] The DC bias controller obtains a static DC bias, and generates a DC bias vector based on the dynamic DC bias and the static DC bias.

[0206] In one implementation of the embodiment of the present application, the method further includes:

[0207] The signal receiving end receives the optical signal sent by the signal sending end;

[0208] The signal receiving end converts the optical signal into an electrical signal, and filters out a DC bias vector in the electrical signal to obtain a received signal;

[0209] The signal receiving end analyzes the public signal part in the received signal to determine the public data stream;

[0210] The signal receiving end filters out the public signal part in the received signal and then performs analysis again to determine the private data stream;

[0211] The wireless optical communication system determines a corresponding public data rate based on a public data stream;

[0212] The wireless optical communication system determines a corresponding private data rate based on a private data stream; and the wireless optical communication system determines a receiving end combined rate based on the public data rate and the private data rate.

[0213] In an implementation of the embodiment of the present application, the wireless optical communication system analyzes the public signal part in the received signal to determine the public data rate corresponding to the public data flow, including:

[0214] The wireless optical communication system analyzes the public signal part in the received signal to determine an initial public data rate corresponding to the public data stream;

[0215] The wireless optical communication system obtains actual rate constraint conditions of the public data flow;

[0216] The wireless optical communication system determines an actual public data rate based on the actual rate constraint condition and the initial public data rate.

[0217] In one implementation of the embodiment of the present application, before the method, the method further includes:

[0218] Taking the system transmission power consumption as the system constraint model;

[0219] The constraint model is solved by a continuous convex approximation method to obtain a baseband precoding matrix and a direct current control matrix.

[0220] The wireless optical communication method based on subarray and dynamic DC bias provided in the present application is applied to the wireless optical communication system based on subarray and dynamic DC bias in the above-mentioned embodiment, and can solve the technical problem that the OWC-MIMO system using IM / DD technology has a large power overhead and is often used in power consumption-constrained scenarios. Compared with the prior art, the beneficial effects of the wireless optical communication method based on subarray and dynamic DC bias provided in the present application are the same as the beneficial effects of the wireless optical communication system based on subarray and dynamic DC bias provided in the above-mentioned embodiment, and the other technical features of the wireless optical communication method based on subarray and dynamic DC bias are the same as the features disclosed in the above-mentioned embodiment system, which will not be repeated here.

[0221] The above descriptions are only some embodiments of the present application, and are not intended to limit the patent scope of the present application. All equivalent structural changes made using the contents of the present application specification and drawings under the technical concept of the present application, or direct / indirect applications in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A wireless optical communication system based on subarray and dynamic DC bias, characterized in that: The system at least comprises: a signal transmitting end; The signal sending end includes: a message splitting module, a message merging module, an encoder and a signal sending module; The message splitting module is connected to the message merging module and the encoder respectively, the message merging module is also connected to the encoder, the encoder is also connected to the signal sending module, and the signal sending module includes: a baseband precoder, a baseband chain, a DC bias controller and an LED subarray; The encoder is connected to the baseband precoder; the baseband precoder is also connected to a plurality of baseband chains, each of which is connected to a corresponding LED sub-array; the DC bias controller is connected to each of the LED sub-arrays; The message splitting module is used to split the message list to be transmitted to obtain a public message list and a private message list; The message merging module is used to merge the public messages in the public message list to obtain a merged public message; The encoder is used to encode the merged public message and the private messages in the private message list respectively to obtain a public data stream and a plurality of private data streams; The signal sending module is used to generate optical signals corresponding to the public data stream and each of the private data streams based on the LED sub-array; The baseband precoder is used to independently encode and linearly superpose the public data stream and each of the private data streams based on a baseband precoding matrix to obtain a precoded mixed data stream; The DC bias controller is used to generate a DC bias vector; The LED sub-array is used to generate an optical signal based on the pre-coded mixed data stream and the DC bias vector; The DC bias controller is also connected to the encoder; The DC bias controller is further used to determine a dynamic DC bias based on a data stream and a DC control matrix; the data stream is the public data stream and the private data stream; The DC bias controller is further used to obtain a static DC bias, and generate a DC bias vector based on the dynamic DC bias and the static DC bias.

2. The wireless optical communication system based on subarray and dynamic DC bias according to claim 1, characterized in that: The system further comprises: a signal receiving end; The signal receiving end is used to receive the optical signal sent by the signal sending end; The signal receiving end is further used to convert the optical signal into an electrical signal and filter out the DC bias vector in the electrical signal to obtain a received signal; The signal receiving end is further used to parse the public signal part in the received signal to determine the public data stream; The signal receiving end is further used to filter out the public signal part in the received signal and then parse it again to determine the private data stream; The wireless optical communication system is further used to determine a private data rate corresponding to the private data stream; The wireless optical communication system is further used to determine a public data rate corresponding to a public data flow; The wireless optical communication system is also used to determine the receiving end combined rate based on the public data rate and the private data rate.

3. The wireless optical communication system based on subarray and dynamic DC bias according to claim 2, characterized in that: The wireless optical communication system is further used to parse the public signal part in the received signal to determine the initial public data rate corresponding to the public data flow; The wireless optical communication system is also used to obtain actual rate constraints of the public data flow; The wireless optical communication system is further used to determine an actual public data rate based on the actual rate constraint condition and the initial public data rate.

4. The wireless optical communication system based on subarray and dynamic DC bias according to claim 1, characterized in that: The wireless optical communication system is further used to use the system transmission power consumption as a constraint model of the system; The wireless optical communication system is also used to solve the constraint model through a continuous convex approximation method to obtain a baseband precoding matrix and a direct current control matrix.

5. A wireless optical communication method based on subarray and dynamic DC bias, characterized in that: The method is applied to the wireless optical communication system based on subarray and dynamic DC bias as claimed in any one of claims 1 to 4, and the method comprises: The message splitting module splits the message list to be transmitted to obtain a public message list and a private message list; The message merging module merges the public messages in the public message list to obtain a merged public message; The encoder encodes the merged public message and the private messages in the private message list respectively to obtain a public data stream and a plurality of private data streams; The signal sending module generates optical signals corresponding to the public data stream and each of the private data streams based on the LED sub-array; The step of the signal sending module generating the optical signals corresponding to the public data stream and each of the private data streams based on the LED sub-array includes: The baseband precoder independently encodes and linearly superimposes the public data stream and each of the private data streams based on a baseband precoding matrix to obtain a precoded mixed data stream; The DC bias controller generates a DC bias vector; The LED sub-array generates an optical signal based on the precoded mixed data stream and the DC bias vector; The step of generating a DC bias vector by the DC bias controller comprises: The DC bias controller determines a dynamic DC bias based on a data stream and a DC control matrix; the data stream is the public data stream and the private data stream; The DC bias controller obtains a static DC bias, and generates a DC bias vector based on the dynamic DC bias and the static DC bias.

6. The wireless optical communication method based on subarray and dynamic DC bias according to claim 5, characterized in that: The method further comprises: The signal receiving end receives the optical signal sent by the signal sending end; The signal receiving end converts the optical signal into an electrical signal, and filters out a DC bias vector in the electrical signal to obtain a received signal; The signal receiving end analyzes the public signal part in the received signal to determine the public data stream; The signal receiving end filters out the public signal part in the received signal and then performs analysis again to determine the private data stream; The wireless optical communication system determines a private data rate corresponding to the private data stream; The wireless optical communication system determines a public data rate corresponding to a public data flow; The wireless optical communication system determines a receiving end combined rate based on the public data rate and the private data rate.

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