2D beam selection procedure in optical wireless communication system

Abstract

An optical wireless communication device (100) comprising: a two-dimensional array of transmitters (110), each transmitter being arranged to transmit optical signals and having a separate coverage area; wherein the two-dimensional emitter array (110) is arranged to create a combined coverage area larger than the individual coverage areas, wherein each individual coverage area is uniformly distributed within the combined coverage area; a receiver (120) configured to receive feedback from remote devices in the combined coverage area; and a controller (101) configured to assign an address to each transmitter among the two-dimensional array of transmitters, each address comprising a pair of codes representing coordinates on the X-axis and the Y-axis, respectively, according to a Cartesian coordinate system to uniquely identify each transmitter in the Cartesian coordinate system; wherein each transmitter in the two-dimensional array of transmitters (110) is configured to transmit a beacon signal comprising its address for assisting the remote device in providing feedback, and wherein the plurality of transmitters are configured to transmit the beacon signals according to code division multiple access; and the controller (101) is configured to select a transmitter from among the two-dimensional array of transmitters (110) according to feedback received from the remote device for establishing an optical wireless data link with the remote device.

Description

Technical Field

[0001] The present invention relates to the field of optical wireless communications, such as Li-Fi communications. More particularly, various devices, systems, and methods related to secure optical wireless communications systems are disclosed herein. Background Art

[0002] To enable more and more electronic devices, such as laptops, tablets, and smartphones, to connect wirelessly to the Internet, wireless communications face unprecedented requirements for data rates and link quality, and these requirements keep growing year by year, given the emerging digital revolution associated with the Internet of Things (IoT). Radio frequency technologies, such as Wi-Fi, have limited spectrum capacity and are unable to meet this revolution. Meanwhile, light fidelity (Li-Fi) has attracted increasing attention due to its inherent security enhancements and ability to support higher data rates over available bandwidth in the visible, ultraviolet (UV), and infrared (IR) spectrums. In addition, compared to Wi-Fi, Li-Fi is directional and shielded by light-blocking materials, which makes it possible to deploy a larger number of access points in areas with dense user density by spatially reusing the same bandwidth. These key advantages over wireless RF communications make Li-Fi a promising and secure solution to relieve the pressure on the crowded radio spectrum for IoT applications as well as indoor wireless access. Other possible benefits of Li-Fi may include guaranteed bandwidth for specific users and the ability to operate safely in areas that are otherwise susceptible to electromagnetic interference. Therefore, Li-Fi is a very promising technology for enabling the next generation of immersive connectivity.

[0003] Achieving high data throughput and / or long range while maintaining wide-angle coverage in a point-to-point OWC system is a challenge not only because of the increased power requirements on the transmitter, but also because it is not always possible to increase the transmission power in the optical system above a certain level due to eye safety requirements.

[0004] To solve this problem, it is known to achieve overall coverage by using a set of small-angle beams, of which only one small-angle beam will be able to be used for actual data communication, thus reducing power consumption. Due to some overlap of the beams (which is necessary to achieve seamless switching between beams), the receiving device will detect several beams simultaneously and will select the best beam for communication. Summary of the invention

[0005] To assist in this beam selection process, a unique code may be used to identify each transmitted beam. When the beams are placed in a matrix to cover an area, the number of codes required grows rapidly, e.g., quadratically for a square matrix. In order to select the correct beam at the remote receiver device, the received signal needs to be cross-correlated with every possible CDMA code that the transmitter could have used, thereby generating a correlation peak whose magnitude corresponds to the received signal strength for each beam. Since cross-correlation is a computationally intensive operation, scaling becomes difficult as the number of beams increases, especially when using a low-power processor (e.g., a microcontroller) with limited CPU and memory capabilities to decode the signal.

[0006] By encoding each beam with a pair of codes representing its coordinates in the emitter matrix, the quadratic growth of required codes returns to linear growth. By using row and column attributes, each emitter in the beam array can be uniquely identified or addressed by these two parameters. As an example, an emitter in an N×N beam array can be identified by 2N codes instead of N. 2 In this way, the number of transmitted codes used to identify the beam is reduced, which saves memory usage and transmission power at the transmitter. Therefore, the complexity for detecting the beam at the receiver side is also reduced, for example, the calculation of the cross-correlation is simplified.

[0007] In view of the above, the present disclosure is directed to methods, apparatuses and systems for providing an efficient 2D beam selection process in an optical wireless communication system. More particularly, the object of the present invention is achieved by an optical wireless communication device as claimed in claim 1, an optical wireless communication system as claimed in claim 10, a beam selection method of an optical wireless communication device as claimed in claim 13, and a method of a remote optical receiver for assisting beam selection as claimed in claim 14.

[0008] According to a first aspect of the present invention, an optical wireless communication device is provided. An optical wireless communication device comprises: a two-dimensional array of transmitters, each transmitter being arranged to transmit an optical signal and having a separate coverage area; wherein the two-dimensional array of transmitters is arranged to create a combined coverage area larger than the separate coverage area, wherein each separate coverage area is evenly distributed within the combined coverage area; a receiver configured to receive feedback from a remote device in the combined coverage area; and a controller configured to assign an address to each transmitter in the two-dimensional array of transmitters, each address comprising a pair of codes, the pair of codes representing coordinates on an X-axis and a Y-axis respectively according to a Cartesian coordinate system, so as to uniquely identify each transmitter in the Cartesian coordinate system; wherein each transmitter in the two-dimensional array of transmitters is configured to send a beacon signal including its address, for assisting the remote device in providing feedback, wherein a plurality of transmitters are configured to send beacon signals according to code division multiple access; and the controller is configured to select a transmitter from the two-dimensional array of transmitters according to the feedback received from the remote device, for establishing an optical wireless data link with the remote device.

[0009] Optical wireless communication can be performed in the visible, ultraviolet (UV) and infrared (IR) spectra. Therefore, optical wireless communication can also be referred to as Li-Fi communication or visible light communication (VLC). Each transmitter includes at least one light source for optical data transmission. The light source can be one of a light emitting diode (LED), a laser diode, a vertical cavity surface emitting laser (VCSEL) or an edge emitting laser diode (EELD). Preferably, the light source includes at least one of an LED and a VCSEL.

[0010] It is known that in order to support high data rate optical wireless communication, it is effective to use narrow beam transmitters. However, for a single narrow beam transmitter, the coverage area may be very limited. Therefore, in a practical system, the overall coverage can be completed by deploying a small angle transmitter array on the transmitter side, and only the transmitter that is best aligned with the remote receiver will be able to communicate data. In this sense, the transmitter achieves high data rate and large coverage with relatively low power consumption.

[0011] A unique code sequence can be used to identify each emitter of an array of emitters. However, as the size of the matrix increases, the number of unique code sequences required grows rapidly. A reduction in the number of code sequences can be achieved by addressing each emitter by a pair of codes to identify the coordinates on the X and Y axes, respectively, according to a Cartesian coordinate system. In this way, the emitter is identified by the combination of codes. For example, an N×N beam matrix will typically require N 2 Different code sequences are needed, while transmitting the combination of row and column indices will only require 2N different code sequences. Clearly, the reduction factor grows with the increase of matrix size.

[0012] Since the pair of codes uniquely identifies a transmitter in the array, when each transmitter is configured to transmit a beacon signal including its address, and multiple transmitters are configured to transmit beacon signals simultaneously according to code division multiple access, the remote device will be able to distinguish the beacon signals from each other and provide feedback to the optical wireless communication device. The optical wireless communication device will then use the feedback to select a transmitter in the array for data communication.

[0013] Advantageously, the codes used to address the transmitters in a Cartesian coordinate system are orthogonal to each other.

[0014] The greater the code distance between any two codes used as coordinates in a Cartesian coordinate system, the easier it is for a remote device to distinguish an address from a beacon signal received from an optical wireless communication device. It is therefore preferred that all codes are orthogonal to one another.

[0015] In one example, the axes of the Cartesian coordinate system are aligned horizontally and vertically with the rows and columns of the two-dimensional array.

[0016] Two-dimensional arrays of emitters are typically deployed as a matrix with a uniform layout, so that the separation distance between any two emitters in the same row or column is the same, such as d. The axes of a Cartesian coordinate system are used as a reference for addressing the emitters in the array. These axes can be aligned with the rows and columns of the two-dimensional array, or have a different orientation compared to the rows and columns of the array.

[0017] When the axes are aligned with the rows and columns of the two-dimensional array, the separation distance between any two emitters sharing the same X-axis or Y-axis coordinate is the same as the physical separation distance between any two emitters in the same row or column, such as d.

[0018] In another example, the axes of the Cartesian coordinate system are rotated through an angle as compared to the rows and columns of the two-dimensional array to increase the minimum separation distance between any two emitters in the two-dimensional array that share the same X-axis or Y-axis coordinates.

[0019] To increase the separation distance between any two emitters sharing the same X-axis or Y-axis coordinate, it is beneficial to rotate the axes of the Cartesian coordinate system by an angle as compared to the rows and columns of a two-dimensional array. And then the minimum separation distance of two emitters sharing the same X-axis or Y-axis coordinate will be greater than d.

[0020] Advantageously, the axes of the Cartesian coordinate system are rotated by arctangent (0.5) degrees as compared to the rows and columns of the two-dimensional array.

[0021] For an NxN array, this can maximize the minimum separation distance between two emitters that share the same X or Y coordinate. For matrices of different sizes, another rotation angle may be even more beneficial.

[0022] In one option, the receiver is an RF receiver.

[0023] The feedback may be provided in a radio frequency channel according to a short range wireless communication protocol such as the Wi-Fi, BLE or Zigbee standards.

[0024] In another option, the receiver is an optical receiver.

[0025] Feedback may also be provided in a spectrum that is either the same as the optical wireless data communication or another frequency band.

[0026] Advantageously, the optical receiver is further configured to receive the optical data signal in a bidirectional optical wireless data link.

[0027] Advantageously, the two-dimensional array of emitters is arranged in a matrix in two orthogonal directions, or in a hexagonal structure in two directions.

[0028] Although the optical transmitters can be arranged in an orthogonal array / matrix, it may be beneficial to use a hexagonal structure instead of a square or rectangular structure. The hexagonal structure allows for reduced overlap of coverage areas of adjacent transmitters.

[0029] According to a second aspect of the present invention, an optical wireless communication system is provided. An optical wireless communication system comprises an optical wireless communication device according to the present invention; a remote optical receiver comprising at least one photodiode, which is configured to detect a plurality of beacon signals transmitted by the optical wireless communication device; a controller, which is configured to decode a first address included in a beacon signal having the highest received signal strength among the plurality of beacon signals; wherein the remote optical receiver is configured to provide feedback about the first address to the optical wireless communication device, and the optical wireless communication device is configured to select a corresponding transmitter according to the first address indicated in the feedback, so as to establish an optical wireless communication link with the remote optical receiver.

[0030] When detecting multiple beacon signals transmitted by an optical wireless communication device, the remote optical receiver needs to identify the beacon signal with the strongest received signal strength. The transmitter that transmits the beacon signal with the strongest received signal strength is the transmitter that is best aligned with the remote optical receiver. Since the address information is embedded in the beacon signal, by distinguishing the beacon signal, the remote optical receiver can also decode the address of the transmitter and provide feedback to the optical wireless communication device on the decoded address.

[0031] The remote optical receiver includes at least one photodiode. The photodiode may also be referred to as a photodetector, a photodetector, or a photoelectric sensor, which may be a PIN diode, an avalanche photodiode (APD), or a photomultiplier. The field of view of the remote optical receiver may cover only a subset of the multiple transmitters of the optical wireless communication device. And then, the remote optical receiver may detect only a subset of the beacon signals transmitted by the optical wireless communication device, and select the first address from the subset of the beacon signals received by the remote optical receiver.

[0032] Beneficially, the controller of the remote optical receiver is configured to calculate cross-correlation results between multiple beacon signals detected, wherein each code is used as a coordinate in a Cartesian coordinate system of the optical wireless communication device, and sum the cross-correlation results of each pair of codes representing coordinates on the X-axis and Y-axis of the Cartesian coordinate system to derive the relative signal strength of each beacon signal, and select the beacon signal with the highest received signal strength based on the relative signal strength.

[0033] The transmitter of the optical wireless communication device simultaneously transmits multiple beacon signals according to code division multiple access. The detection of the beacon signal is based on the cross-correlation between the local copy of the code sequence and the received overlapping beacon signals. Because the address of the individual transmitter of the optical wireless communication device includes a pair of codes, the cross-correlation is performed for each individual code representing the X-axis or Y-axis. The sum of the cross-correlation results of each pair of codes representing the address of the individual transmitter is used to estimate the relative signal strength of each beacon signal. Since the transmitters all transmit with the same output power, the higher the relative signal strength received by the remote optical receiver, the better the alignment between the transmitter and the remote optical receiver.

[0034] In one example, the remote optical receiver further includes an RF transmitter or an optical transmitter to send feedback on the first address to the optical wireless communication device.

[0035] Feedback to the optical wireless communication device may be provided in the radio frequency band or in the optical frequency band.

[0036] In a preferred arrangement, the remote optical receiver comprises an optical transmitter and a bidirectional optical data link can then be established.

[0037] According to a third aspect of the present invention, a beam selection method is provided. A beam selection method includes the following steps of an optical wireless communication device: each transmitter in a two-dimensional transmitter array of the optical wireless communication device transmits an optical signal and has a separate coverage area; a combined coverage area is created by the two-dimensional transmitter array, wherein the combined coverage area is larger than the separate coverage area of ​​the transmitter in the two-dimensional transmitter array, and each separate coverage area is evenly distributed within the combined coverage area; an address is assigned to each transmitter in the two-dimensional transmitter array, each address includes a pair of codes, and the pair of codes respectively represent the coordinates on the X-axis and the Y-axis according to the Cartesian coordinate system to uniquely identify each transmitter in the Cartesian coordinate system; each transmitter sends a beacon signal, the beacon signal includes its assigned address, and is used to assist a remote device in providing feedback; a plurality of transmitters send a beacon signal according to code division multiple access; feedback is received from a remote device in the combined coverage area; and a transmitter is selected from the two-dimensional transmitter array according to the feedback received from the remote device to establish an optical wireless data link.

[0038] According to another aspect of the present invention, a method of a remote optical receiver is provided. The method includes the following steps of the remote optical receiver: detecting a plurality of beacon signals transmitted by an optical wireless communication device; decoding a first address included in a beacon signal having the highest received signal strength among the plurality of beacon signals; and providing feedback about the first address to the optical wireless communication device.

[0039] Advantageously, the method of the remote optical receiver further includes the steps of: calculating cross-correlation results between a plurality of detected beacon signals, wherein each code is used as a coordinate in a Cartesian coordinate system of the optical wireless communication device; summing the cross-correlation results for each pair of codes representing coordinates on the X-axis and Y-axis of the Cartesian coordinate system to derive a relative signal strength for each beacon signal; and selecting the beacon signal having the highest received signal strength based on the relative signal strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In the drawings, similar reference numerals are used throughout the different Figure 1 Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

[0041] Figure 1 An example of addressing a two-dimensional emitter array according to the present invention is shown;

[0042] Figure 2 Another example of addressing a two-dimensional emitter array according to the present invention is shown;

[0043] Figure 3 A further example of addressing a two-dimensional emitter array according to the present invention is shown;

[0044] Figure 4 A block diagram of an optical wireless communication device is shown;

[0045] Figure 5 An implementation example of address generation in an optical wireless communication device is shown; and

[0046] Figure 6 An implementation example of a remote optical receiver is shown. DETAILED DESCRIPTION

[0047] The embodiments set forth below represent information that enables those skilled in the art to practice these embodiments. After reading the following description in light of the accompanying drawings, those skilled in the art will understand the concepts of the present disclosure and will recognize the applications of these concepts, which are not particularly set forth herein. It should be understood that these concepts and applications fall within the scope of the present disclosure.

[0048] In optical wireless systems for data communication (LiFi), overall coverage can be achieved by using a set of small-angle beams, of which only one will be able to be used for data communication, thus reducing power consumption. A unique code sequence can be used to identify each beam. However, when placing the beams in a matrix, the number of unique code sequences required grows rapidly.

[0049] By transmitting two codes per beam, a reduction in the number of code sequences can be achieved. In this way, beams or transmitters are identified by code combinations. For example, a 5×5 beam matrix would normally require 25 different code sequences, while transmitting its row and column index combinations would only require 10 different code sequences. Advantageously, the reduction factor grows as the matrix size increases.

[0050] For example, if each transmitter transmits a single orthogonal code sequence (such as a CDMA code), the remote receiver obtains the signal strength of each beam by correlating the received signal with each CDMA code used. When the correlator output shows a clear peak, there is a match between the CDMA code and the code sequence present in the received signal. The peak amplitude indicates the received signal strength of the corresponding beam.

[0051]

[0052] However, when each transmitter transmits a pair of codes (e.g., its row and column codes), the receiver needs to correlate with the corresponding two codes separately:

[0053]

[0054] Figure 1An example of addressing a two-dimensional array of transmitters is shown, where each solid dot represents an individual transmitter. For ease of illustration, this example provides a 4×4 beam array. It can be encoded using eight CDMA codes, as given by Figure 1 , as indicated by the solid and dashed lines in directions A and B. Directions A and B represent the X and Y axes of a Cartesian coordinate system for addressing multiple transmitters. Each row represents a different CDMA code. Therefore, a transmitter can be uniquely identified by a pair of codes representing coordinates on the X and Y axes, respectively.

[0055] By using only 8 CDMA codes, 4 codes to identify rows and 4 codes to identify columns, the code pairs assigned to the transmitters are not completely orthogonal to each other because each CDMA code is shared by 4 transmitters on the same row or column. For example, to detect beam 1, the correlation will look like:

[0056]

[0057] For example, when the receiving device is exactly in the center of beam 1, the correlation will detect the CDMA originating from beam 1. A1 and CDMA B1 In addition, in the case of overlapping beams, the CDMA signal transmitted by beam 5 A1 and CDMA transmitted by beam 2 B1 will add to the result and give a higher peak. Typically, the correlator will show a positive offset relative to the true signal strength of the beam. The amount of offset depends on the amount of overlap between the coverage areas of adjacent transmitters, and the actual location of the remote receiver.

[0058] The described effect can be counteracted by distributing the repeated CDMA codes so that their distance becomes larger and at least the code pairs of adjacent transmitters become completely orthogonal. Figure 1 The configuration of the Cartesian coordinate system is aligned horizontally and vertically with the rows and columns of the two-dimensional array. Therefore, the minimum repetitive code distance (RCD) is "d", which is the separation distance between two transmitters in the two-dimensional array. In order to obtain orthogonal addresses of adjacent transmitters, the minimum RCD should be increased to 2d.

[0059] Figure 2 Another example of addressing a two-dimensional array of emitters is shown. Here, the assignment of codes is shown only for direction A. Note that direction B is perpendicular to direction A and codes are assigned in the same manner as direction A. Figure 2In the example of , the axes of the Cartesian coordinate system are no longer aligned horizontally and vertically with the rows and columns of the two-dimensional array. Instead, the axes of the Cartesian coordinate system are rotated through an angle (α) as compared to the rows and columns of the two-dimensional array to increase the minimum separation distance between any two emitters in the two-dimensional array that share the same X-axis or Y-axis coordinates. Figure 2 A rotation angle (α) of 45 degrees is shown, which results in a minimum repetitive code distance (RCD) of “√2d”.

[0060] Similarly, Figure 3 Another example of addressing a two-dimensional array of emitters is shown. Figure 2 The example in is the same as in , except that the axes of the Cartesian coordinate system are also rotated through an angle (α) compared to the rows and columns of the two-dimensional array. Note that, as compared to the previous example, the repeated lines of code are separated into sections by line breaks. For Figure 3 The rotation angle (α) of arctangent(0.5) degrees in the line breaks results in a minimum repetitive code distance (RCD) of "2d" between line breaks, considering that the code distance along the line is even larger (√5d). Therefore, Figure 3 The example shown in is optimal for a 4×4 transmitter array, and the code sequences assigned to adjacent transmitters are completely orthogonal.

[0061] In summary, by encoding an array of N×N transmitters with 2N CDMA codes, the efficiency of the beam selection process can be improved. In order to maximize the orthogonality between code sequences assigned to adjacent transmitters, it is ideal to maximize the minimum repetitive code distance (RCD). The disclosed method can be applied to matrices of any size, such as N×M, where N≠M. The configuration when the RCD is maximized may depend on the actual size of the matrix. In other words, the optimal rotation angle (α) may need to be adjusted depending on the actual size of the two-dimensional array.

[0062] Figure 4A block diagram of an optical wireless communication device 100 is shown. The optical wireless communication device 100 includes at least a two-dimensional transmitter array 110, a receiver 120, and a controller 101. Each transmitter is arranged to transmit an optical signal and has a separate coverage area; wherein the two-dimensional transmitter array 110 is arranged to create a combined coverage area that is larger than the separate coverage area, wherein each separate coverage area is evenly distributed within the combined coverage area. The receiver 120 is configured to receive feedback from a remote device in the combined coverage area. The controller 101 is configured to assign an address to each transmitter in the two-dimensional transmitter array 110, wherein each address includes a pair of codes that represent coordinates on the X-axis and the Y-axis, respectively, according to a Cartesian coordinate system, so as to uniquely identify each transmitter in the Cartesian coordinate system. Each transmitter in the two-dimensional transmitter array 110 is configured to send a beacon signal including its address to assist the remote device in providing feedback, wherein multiple transmitters are configured to send beacon signals according to code division multiple access; and the controller 101 is configured to select a transmitter from the two-dimensional transmitter array 110 based on the feedback received from the remote device to establish an optical wireless data link with the remote device.

[0063] Figure 5 An implementation example of address generation in an optical wireless communication device is shown. For simplicity, Figure 5 The example in corresponds to Figure 1 The addressing method used in . The controller 101, which can be a microcontroller, generates 8 different CDMA codes on 8 different pins (4 per row and 4 per column). Each pin is connected to a fan-out buffer 102 to be able to sum each code for a particular row with each column code without interfering with each other. This summing is achieved by adding a resistor 103 to each line of the output buffer. This will generate a three-level signal for each beam 104, which will contain the sum of the row code and the column code.

[0064] The reduction in the number of required CDMA codes also results in a reduction in receiver complexity. As mentioned earlier, the signal strength detection for each beam is compared according to the following equation:

[0065]

[0066] For efficiency, it is preferable to split this calculation into two separate parts:

[0067]

[0068] A beam =a i +b j

[0069] The terms ai and b j Can be reused for multiple beams. Figure 6 A functional diagram of beam decoding in a remote optical receiver is shown. The signal is collected by an optical detector 201 and fed to an ADC 202 which may be external to or integrated in the controller of the optical receiver. The controller 203 will then perform correlation of the received signal with 8 possible correlators (4 correlators 205 per row and 4 correlators 204 per column). By correlating the correlator outputs (ai and b) of each row-column correlator pair j ) are summed, the combined correlator amplitude for each possible beam can be obtained. The beam with the strongest correlation result will then be selected as the best received beam. And the address indicated in the code pair will be provided to the optical transmitter as feedback.

[0070] The method according to the invention can be implemented on a computer as a computer-implemented method, or in dedicated hardware, or in a combination of both.

[0071] The executable code of the method according to the invention may be stored on a computer / machine readable storage device. Examples of computer / machine readable storage devices include non-volatile storage devices, optical storage media / devices, solid-state media, integrated circuits, servers, etc. Preferably, the computer program product comprises non-transitory program code means stored on a computer readable medium for performing the method according to the invention when the program product is executed on a computer.

[0072] Methods, systems, and computer-readable media (transitory and non-transitory) may also be provided to implement selected aspects of the above-described embodiments.

Claims

1. An optical wireless communication device (100), comprising: - a two-dimensional array of emitters (110), each emitter being arranged to emit an optical signal and having an individual coverage area; wherein the two-dimensional transmitter array (110) is arranged to create a combined coverage area that is larger than the individual coverage areas, wherein each individual coverage area is evenly distributed within the combined coverage area; - a receiver (120) configured to receive feedback from remote devices in the combined coverage area; and, - a controller (101) configured to assign an address to each emitter in the two-dimensional emitter array, each address comprising a pair of codes, the pair of codes representing coordinates on the X-axis and the Y-axis respectively according to a Cartesian coordinate system, so as to uniquely identify each emitter in the Cartesian coordinate system; wherein each transmitter in the two-dimensional array of transmitters (110) is configured to transmit a beacon signal including its address for assisting a remote device in providing feedback, wherein the plurality of transmitters are configured to transmit the beacon signal according to code division multiple access; And the controller (101) is configured to select a transmitter from the two-dimensional transmitter array (110) according to feedback received from the remote device, for establishing an optical wireless data link with the remote device.

2. The optical wireless communication device (100) of claim 1, wherein the codes used to address the transmitters in a Cartesian coordinate system are orthogonal to each other.

3. The optical wireless communication device (100) of claim 1 or 2, wherein the axes of the Cartesian coordinate system are aligned horizontally and vertically with the rows and columns of the two-dimensional array.

4. An optical wireless communication device (100) according to claim 1 or 2, wherein the axes of the Cartesian coordinate system are rotated through an angle (α) as compared to the rows and columns of the two-dimensional array to increase the minimum separation distance between any two transmitters sharing the same X-axis or Y-axis coordinates in the two-dimensional array.

5. The optical wireless communication device (100) of claim 4, wherein the angle (α) is arctangent (0.5) degrees.

6. The optical wireless communication device (100) according to any one of the preceding claims, wherein the receiver (120) is an RF receiver.

7. The optical wireless communication device (100) according to any of the preceding claims 1-5, wherein the receiver (120) is an optical receiver.

8. The optical wireless communication device (100) of claim 7, wherein the optical receiver is further configured to receive the optical data signal in a bidirectional optical wireless data link.

9. An optical wireless communication device (100) according to any of the preceding claims, wherein the two-dimensional array of transmitters (110) is arranged in a matrix along two orthogonal directions or in a hexagonal structure along two directions.

10. An optical wireless communication system, comprising: - An optical wireless communication device (100) according to any one of the preceding claims; - a remote optical receiver (200) comprising: - at least one photodiode (201) configured to detect a plurality of beacon signals transmitted by the optical wireless communication device (100); - a controller (203) configured to decode a first address included in a beacon signal having a highest received signal strength among a plurality of beacon signals; The remote optical receiver (200) is configured to provide feedback about the first address to the optical wireless communication device (100), and the optical wireless communication device (100) is configured to select a corresponding transmitter according to the first address indicated in the feedback to establish an optical wireless communication link with the remote optical receiver (200).

11. An optical wireless communication system according to claim 10, wherein the controller (203) of the remote optical receiver (200) is configured to calculate cross-correlation results between the detected multiple beacon signals, wherein each code is used as a coordinate in a Cartesian coordinate system of the optical wireless communication device (100), and the cross-correlation results of each pair of codes representing the coordinates on the X-axis and Y-axis of the Cartesian coordinate system are summed to derive the relative signal strength of each beacon signal, and the beacon signal with the highest received signal strength is selected based on the relative signal strength.

12. The optical wireless communication system according to claim 10 or 11, wherein the remote optical receiver (200) further comprises an RF transmitter or an optical transmitter for sending feedback about the first address to the optical wireless communication device (100).

13. A beam selection method, comprising the following steps of an optical wireless communication device (100): - each transmitter in a two-dimensional array of transmitters (110) of an optical wireless communication device (100) transmits an optical signal and has an individual coverage area; - creating a combined coverage area from the two-dimensional transmitter array (110), wherein the combined coverage area is larger than the individual coverage areas of the transmitters in the two-dimensional transmitter array (110), and each individual coverage area is evenly distributed within the combined coverage area; - assigning an address to each emitter in the two-dimensional emitter array (110), each address comprising a pair of codes, the pair of codes representing coordinates on the X-axis and the Y-axis respectively according to a Cartesian coordinate system, so as to uniquely identify each emitter in the Cartesian coordinate system; - a beacon signal is sent by each transmitter, the beacon signal including its assigned address to assist the remote device in providing feedback; - sending beacon signals by a plurality of transmitters (110) according to code division multiple access; - receiving feedback from remote devices in the combined coverage area; and - Selecting a transmitter from a two-dimensional array of transmitters (110) for establishing an optical wireless data link based on feedback received from a remote device.

14. A method for assisting the beam selection method according to claim 13, the method comprising the following steps of a remote optical receiver (200): - detecting a plurality of beacon signals transmitted by an optical wireless communication device (100); - decoding a first address included in a beacon signal having the highest received signal strength among a plurality of beacon signals; and - providing feedback to the optical wireless communication device (100) regarding the first address.

15. The method according to claim 14, further comprising the steps of: - calculating a cross-correlation result between the detected plurality of beacon signals, wherein each code is used as a coordinate in a Cartesian coordinate system of the optical wireless communication device (100); - summing the cross-correlation results for each pair of codes representing coordinates on the X-axis and Y-axis of a Cartesian coordinate system to derive the relative signal strength of each beacon signal; and -Select the beacon signal with the highest received signal strength based on relative signal strength.

Images