Optical Wireless Communication System and Device

Abstract

According to one aspect disclosed herein, there is provided a client device for use in an optical wireless communications network, the client device including a transceiver configured to receive data over an optical wireless connection. The transceiver includes an upward-facing optical transducer configured to detect or transmit optical wireless transmissions, and a sensor configured to have a coverage area having at least two concentric segments. A portion of the sensor is configured to provide an outermost segment of the at least two concentric segments.

Description

Technical Field

[0001] The present disclosure relates to a transducer for optical wireless communication.

Background Art

[0002] Li-Fi (Light Fidelity) refers to a technology in which information is communicated in the form of signals embedded in visible light, infrared light, or ultraviolet light emitted by a light source. Such technology may also be referred to as coded light, visible light communication (VLC), or free-space optical communication (FSO). The signal is embedded by modulating the properties of the light, typically the intensity, according to any of various suitable modulation techniques. In the case of high-speed communication, infrared (IR) communication is often used instead of visible light communication. Although ultraviolet and infrared radiation are invisible to the human eye, technologies that utilize these regions of the spectrum are similar in that they may vary as a result of wavelength dependence, such as in the case of the refractive index. In many cases, using ultraviolet and / or infrared is advantageous because these frequency ranges are invisible to the human eye. However, ultraviolet frequencies can have high energy levels and in some cases pose health concerns.

[0003] Based on modulation, the information of Li-Fi coded light can be detected using any suitable optical sensor. For example, the optical sensor may be a photodiode. The optical sensor may be a dedicated photocell (point detector), in some cases an array of photocells with a lens, a reflector, a diffuser or a phosphor converter (for low speed), or an array of photocells (pixels) and a lens for forming an image on the array. For example, the optical sensor may be a dedicated photocell included in a dongle that plugs into a user device such as a smartphone, a tablet or a laptop, or the sensor may be integrated and / or may be dual-purpose such as an array of infrared detectors originally designed for 3D face recognition. In either case, this enables an application operating on the user device to receive data via light.

[0004] For example, a sequence of data symbols may be modulated onto light emitted by a light source such as a light emitting diode (LED) and a laser diode (LD) faster than the persistence of the human eye. In contrast to radio frequency (RF) communication, Li-Fi generally uses a line-of-sight connection between the transmitter and the receiver for best performance.

[0005] Li-Fi is often used to embed signals into the light emitted by everyday luminaires, such as indoor or outdoor lighting sources, thus enabling the lighting from the luminaires to be used as a carrier for information. In this way, the light can include both visible lighting contribution (typically the first purpose of the light) for illuminating the target environment, such as a room, and the embedded signals for providing information to the environment (typically considered the second function of the light). In such cases, modulation is typically performed at a frequency high enough to be beyond human perception, or at least weak enough so that any visible temporary light artifacts (such as flicker and / or stroboscopic artifacts) are not noticed by humans or are at least tolerable by humans. Thus, the embedded signals do not affect the main lighting function. That is, the user only perceives the overall lighting and does not perceive the effect of the data modulated in the lighting.

[0006] Wireless optical networks, such as Li-Fi networks, enable electronic devices such as laptops, tablets, and smartphones to connect wirelessly to the Internet. Wi-Fi uses radio frequencies to achieve this, while LiFi can achieve this using the optical spectrum, which can provide unprecedented data transfer speeds and bandwidths. Wi-Fi systems have been bandwidth-limited due to interference from neighboring systems and their omnidirectional radiation patterns. Wi-Fi signals can pass through walls, ceilings, doors, etc., but their bandwidth decreases with the density and number of units used. Li-Fi is becoming increasingly popular as LED lighting systems are being used in place of traditional lighting systems. In contrast to Wi-Fi, Li-Fi is directional and shielded by light-blocking materials, which provides the potential to support broadband communication in areas with a high density of users.

[0007] Furthermore, Li-Fi can be used even in areas that are susceptible to electromagnetic interference. It is important to consider that wireless data is now required not only for traditional connected devices but also for more. Today, televisions, speakers, headphones, printers, virtual reality (VR) goggles, and even refrigerators use wireless data to connect and perform essential communication.

[0008] Digital wireless communication networks (optical or radio frequency-based) typically consist of a number of access points (typically including transceivers, but at least including a transmitter for transmitting optical wireless data), and client devices (also typically including transceivers, but at least including a receiver for receiving optical wireless data). Each access point is located at the center of a coverage area (also called a cell). This arrangement, overall, for example, combines the access point transceiver hardware and the coverage area and may also be called an access point. A coverage area or cell is an area where transmissions from the access point transceiver can be picked up by the client transceiver device. When positioned adjacent to each other, these cells typically fit together to cover a larger area. Each access point or node may be connected to its respective modem. The modem processes the outgoing data signal into a waveform or modulated light suitable for transmission via a wireless or optical channel respectively. Correspondingly, the modem may process the incoming modulated light or waveform received wirelessly into data.

[0009] Embodiments of the present invention are described in the context of a Li-Fi system consisting of a Li-Fi infrastructure having a plurality of Li-Fi access points, as shown in FIG. 1. Each access point includes a modem connected to one or more transceivers (LiFi-TRX). A LiFi client device can be connected to one or more LiFi access points via an optical link, and the LiFi client device includes a modem connected to one or more client device transceivers (LiFi-TRX).

[0010] The function of the LiFi modem is to process PHY and MAC protocols for transmitting and receiving data. The LiFi transceiver (TRX) · LiFi-Transmitter (Tx): Converts the electrical signal of the transmitted data of the modem into an optical signal (to be emitted, for example, by an LED), and · LiFi-Receiver (Rx): Converts the optical signal into an electrical signal of the received data of the modem (for example, a photodiode), functions as follows.

[0011] FIG. 1 shows an environment 100 including a ceiling 102 having a Li-Fi infrastructure composed of a plurality of transceivers 104 and a floor having desks, and on one of the desks there is an example (laptop) of a LiFi client device 106. In FIG. 1, the LiFi device 106 includes a laptop computer having a dedicated dongle for receiving optical signals.

[0012] In the Li-Fi system of FIG. 1, it can be seen that the access point transceiver is positioned on the ceiling to provide the required coverage for the lower area.

[0013] Figure 2 shows the same environment 100 including a Li-Fi infrastructure having a plurality of Li-Fi transceivers 104. The transceivers 104 are located in a first planar area (first surface), e.g., the ceiling, and have a light coverage area for transmitting and receiving Li-Fi signals projected onto a second planar area (second surface), e.g., the floor or desk height level. Two projections 202a and 202b resulting from two respective access point transceivers 104a and 104b are shown to indicate the coverage area achieved by these transceivers on the second planar area (e.g., the surface where a client device is likely to be located). A LiFi client device located in the second planar area is shown. The light coverage area 204 of the client device 106 for transmitting and receiving Li-Fi signals is projected onto the first planar area (e.g., the ceiling). It should be understood that the first planar area and the second planar area are intended to be oriented parallel to each other.

[0014] Arrow 206 depicts a possible movement direction of the client device 106. As the client device 106 moves, the projected coverage area 204 in the first planar area also moves. Therefore, as the client device 106 moves within the environment 100, the client device 106 occupies positions where a plurality of access point transceivers (e.g., transceivers 104a and 104b) can be located within the coverage area 204, and thus it can be seen that a plurality of optical signals may be detected by the client device at any given time.

[0015] FIG. 3 is a plan view showing how the coverage area 202 of each access point transceiver 104 can be arranged to cover a wider area (e.g., arranged on a second plane at desk level from a transceiver at ceiling level). The dotted circle 302 illustrates the boundary of the coverage area 204 of the client device 106 that is directed upward and incident on a first planar area, e.g., at the ceiling level. As shown in FIG. 2, FIG. 3 also shows an arrow 206 to illustrate the possible direction of movement of the client device 106 within the environment 100. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0016] A problem associated with a typical system as described above is that when a client device receives multiple transmission signals from multiple infrastructure network nodes, interference may occur between the received signals. This interference can have an adverse effect on the data transfer rate achievable within a wireless optical communication system. Therefore, it is desirable to optimally design a client device transceiver (or receiver) to mitigate and reduce the potential for interference and increase the potential for high-speed optical data transfer. Further, while a LiFi access point infrastructure may provide complete coverage in terms of LiFi devices, LiFi devices also need to provide a sufficiently large coverage area in terms of LiFi access points.

[0017] When using a typical wireless optical communication system configured as described above, a plurality of problems may occur. These problems may include the following.

[0018] Coverage - A LiFi client device may not necessarily be able to see a LiFi access point, depending on its location, the positioning of the LiFi access point, and the size of the transducer / sensor coverage area of the LiFi client device.

[0019] Power consumption - A LiFi client device having a transceiver that covers a large area may consume a lot of power and generate a lot of heat.

[0020] Downlink interference - A LiFi client device in an overlapping coverage area of multiple optical downlinks is subject to interference when these LiFi access points transmit simultaneously.

[0021] Uplink interference - When a LiFi client device transmits a signal to a LiFi access point and another LiFi client device is transmitting to the same LiFi access point, uplink interference occurs at the LiFi access point.

[0022] Handover - A LiFi client device moving from the coverage area of one LiFi access point to an adjacent LiFi access point may experience a period during which the LiFi client device has no connection. For example, when there is not enough time to prepare and establish a link to the new LiFi access point before the link to the existing LiFi access point is disconnected.

[0023] The embodiments disclosed herein can address any one, multiple, or all of the above problems.

Means for Solving the Problems

[0024] According to a first aspect disclosed herein, there is provided a client device for use in an optical wireless communication network, the network including a plurality of infrastructure nodes arranged at intersections of a grid structure on a first plane and configured to provide access points of the network, the grid structure including a quadrilateral having an x-axis dimension equal to d1, a y-axis dimension equal to d2, and a diagonal dimension equal to d3, where d2 is greater than or equal to d1. The client device includes an upward facing optical transducer configured to detect an optical wireless transmission from the network or transmit an optical wireless transmission to the network, the transducer being configured to have a coverage area having at least two concentric segments, and a portion of the transducer configured to provide the outermost segment of the at least two concentrically arranged segments being dimensioned such that when the client device is positioned on a second plane parallel to the first plane and at a distance from the first plane, the coverage area of the segment has a maximum diameter (Ro) greater than 0.5*d3 on the first plane. The infrastructure nodes may be, for example, access points mounted on a ceiling or network devices of an optical wireless network providing similar functionality.

[0025] In certain embodiments, the distance (h) may have a value between d1 and 1.5*d1. In certain embodiments, the distance (h) may have a value between 1.5*d1 and 2.25*d1.

[0026] In one embodiment, the portion of the transducer configured to provide the outermost segment of at least two concentric segments is an angle in the transducer between the outer edge of the outermost segment and the normal to the surface of the transducer, wherein the surface of the coverage area is perpendicular to the normal and at a distance from the transducer, the angle being greater than 31°, optionally greater than 42°, or an angle in the transducer between the outer edge of the outermost segment and the normal to the surface of the transducer, wherein the surface of the coverage area is perpendicular to the normal and at a distance from the transducer, the angle being greater than 22°, optionally greater than 31°, and may be dimensioned accordingly.

[0027] In one embodiment, the surface of the coverage area is formed at a distance (h) from the transducer between 1.8 meters and 2.7 meters, and the dimension d1 may be equal to 1.8 meters. In an embodiment where d1 is 1.8 meters, the angle is preferably greater than 37°. In one embodiment, the surface of the coverage area is formed at a distance (h) from the transducer between 1.8 meters and 2.7 meters, and the dimension d1 may be equal to 1.2 meters. In an embodiment where d1 is 1.2 meters, the angle may preferably be greater than 26.6°.

[0028] In one embodiment, the portion of the transducer configured to provide the outermost segment of at least two concentric segments is the angle in the transducer between the outer edge of the outermost segment and the normal to the surface of the transducer, where the surface of the coverage area is perpendicular to the normal, and at a distance from the transducer, the angle is less than 45°, optionally less than 33.7°, or the angle in the pre-transducer between the outer edge of the outermost segment and the normal to the surface of the transducer, where the surface of the coverage area is perpendicular to the normal, and at a distance from the transducer, the angle may be dimensioned to be less than 33.7°, optionally less than 24°.

[0029] In one embodiment, the said surface of the coverage area is formed at a distance (h) from the transducer between 1.8 meters and 2.7 meters, and the dimension d1 may be equal to 1.8 meters. In the embodiment where d1 is 1.8 meters, the said angle may preferably be less than 38°.

[0030] In one embodiment, the said surface of the coverage area is formed at a distance from the transducer between 1.8 meters and 2.7 meters, and the dimension d1 may be equal to 1.2 meters. In the embodiment where d1 is 1.2 meters, the said angle may preferably be less than 27.6°.

[0031] In one embodiment, the portion of the transducer configured to provide the outermost segment of at least two concentric segments is such that the outermost segment of at least two concentrically arranged segments is divided circumferentially into further segments, each further segment being bounded by the maximum diameter (704) of the outermost concentric segment, the maximum diameter (706) of the innermost concentric segment, and two radial lines extending from the center of the coverage area to the maximum diameter of the outermost segment, the two radial lines being spaced at an angle (φ) less than 43.4°, optionally, the two radial lines may be dimensioned to be spaced at an angle (φ) less than 43°.

[0032] In one embodiment, the portion of the transducer configured to provide the outermost segment of at least two concentric segments is such that the outermost segment of at least two concentrically arranged segments is divided circumferentially into further segments, each further segment being bounded by the maximum diameter of the outermost concentric segment, the maximum diameter of the innermost concentric segment, and two radial lines extending from the center of the coverage area to the maximum diameter of the outermost segment, the two radial lines being dimensioned to be spaced at an angle (φ) less than 60°.

[0033] In one embodiment, the portion of the transducer configured to provide the outermost segment may be dimensioned such that the circumferential segment overlaps an adjacent circumferential segment at an angle (θ).

[0034] In one embodiment, the angle between the radial lines may remain the same, for example, to keep the segments small enough to meet the "small enough" requirement, but the number of segments may be increased to cover the outer segment and account for the overlap.

[0035] In one embodiment, the portion of the transducer configured to provide the innermost segment of at least two concentric segments has an angle (α) in the transducer between the outer edge of the innermost segment and the normal to the surface of the transducer, where the surface of the coverage area is perpendicular to the normal and at a distance from the transducer, and the angle is between 16.7° and 18.4°, or the angle (α) in the transducer between the outer edge of the innermost segment and the normal to the surface of the transducer, where the surface of the coverage area is perpendicular to the normal and at a distance from the transducer, and the angle may be dimensioned to be between 11.3° and 12.5°.

[0036] In one embodiment, the surface of the coverage area is formed at a distance (h) from the transducer between 1.8 meters and 2.7 meters, and the dimension d1 may be equal to 1.8 meters. In an embodiment where d1 is 1.8 meters, the angle is preferably between 16.7° and 18.4°. In one embodiment, the surface of the coverage area is formed at a distance (h) from the transducer between 1.8 meters and 2.7 meters, and the dimension d1 may be equal to 1.2 meters. In an embodiment where d1 is 1.2 meters, the angle may preferably be between 11.3° and 12.5°.

[0037] In one embodiment, the transducer may be configured to provide one or more intermediate concentrically arranged segments between the innermost and outermost concentrically arranged segments.

[0038] In one embodiment, one or more intermediate segments may be divided into further segments in the circumferential direction. These may or may not align with the circumferential segments of adjacent concentric segments.

[0039] According to a second aspect disclosed herein, a system configured to provide an optical wireless communication network, the system including a plurality of infrastructure nodes disposed at intersections of a grid structure on a first plane and configured to provide access points of the network, the grid structure including a quadrilateral (preferably equiangular) having an x-axis dimension equal to d1, a y-axis dimension equal to d2, and a diagonal dimension equal to d3, where d2 is greater than or equal to d1. The system further includes at least one client device, the client device including an upward-facing optical wireless transducer for receiving an optical wireless signal from the network or transmitting an optical wireless signal to the network, the transducer being configured to have a coverage area having at least two concentric segments, and the outermost segment of the at least two concentric segments being dimensioned such that when the client device is positioned on a second plane parallel to the first plane and at a distance from the first plane, the coverage area of the segment has a maximum diameter (Ro) greater than 0.5*d3 on the first plane.

[0040] That is, when the transducer is located within the front face of the client device and the client device is placed with its back on a surface in a horizontal plane, it is upward-facing in that the front face including the transducer face is in an upward-facing orientation over most of that surface. For example, if the grid structure is on the ceiling of a room and the client device is on a table in the room, the transducer is in a plane parallel to the ceiling and facing towards the ceiling.

[0041] As used herein, "upward" means facing towards the network of the node. Typically, these are located above the ceiling or the user, in which case "upward" also means in the direction opposite to gravity. The opposite meaning is given to "downward".

[0042] In one embodiment, d1 may be 1.8 meters, and h may have a value between d1 and 1.5*d1.

[0043] In one embodiment, d1 may be smaller (e.g., 1.2 m), and thus h may have a value between 1.5*d1 and 2.25*d1.

[0044] In one embodiment, the transducer is configured such that, when the outermost segment of at least two concentric segments is positioned such that the client device is parallel to a first plane and located on a second plane at a distance from the first plane, the coverage area of the segment has a maximum diameter (Ro) with a value smaller than d1 on the first plane.

[0045] In one embodiment, the distance (h) may have a value between d1 and 1.5*d1. In one embodiment, the distance (h) may have a value between 1.5*d1 and 2.25*d1.

[0046] In one embodiment, the transducer is configured such that, when the innermost segment of at least two concentrically arranged segments is positioned such that the client device is parallel to a first plane and located on a second plane at a distance from the first plane, the coverage area of the segment has a maximum diameter (Ri) with a value greater than 0.3*d1 on the first plane.

[0047] In one embodiment, h may have a value between d1 and 1.5*d1. In one embodiment, d1 may be smaller, and thus h may have a value between 1.5*d1 and 2.25*d1.

[0048] The symbol * is used to indicate scalar multiplication of a numerical value with the absolute magnitude of length d1. The value 0.3 may be a decimal value of one third rounded to one significant digit. In certain embodiments, it should be understood that the same value may be represented as the fraction 1 / 3. Similarly, the same value may be represented by a decimal value rounded to more significant digits, such as 0.33, 0.333, etc.

[0049] In certain embodiments, the transducer may be configured such that, when the innermost segment of at least two concentrically arranged segments has a coverage area on the first plane that has a maximum diameter (Ri) of a value less than half of the value of d1 when the client device is positioned on a second plane parallel to and at a distance from the first plane.

[0050] In certain embodiments, h may have a value between d1 and 1.5*d1. In certain embodiments, h may have a value between 1.5*d1 and 2.25*d1.

[0051] In certain embodiments, the transducer has the outermost segment of at least two concentrically arranged segments divided circumferentially into further segments, each further segment being defined by two radial lines extending from the center of the coverage area to the maximum diameter of the outermost concentric segment (Ro), the maximum diameter of the innermost concentric segment (Ri), and the maximum diameter of the outermost segment, and the chord formed between the intersections of the maximum diameter of the outermost segment and the radial lines having a length less than d1. (Chord) It may be configured to be bounded by two radial lines angularly spaced such that the chord has a length less than d1.

[0052] In certain embodiments, each of the circumferential segments may overlap with each adjacent circumferential segment, but may not overlap with any of the inner concentric segments.

[0053] In some embodiments, each of the circumferential segments may be separated from an adjacent circumferential segment by a wall perpendicular to the surface of the transducer.

[0054] In some embodiments, the wall may comprise a reflective material.

[0055] According to another aspect disclosed herein, there is provided an infrastructure node for use in an optical wireless communication network, the network comprising a plurality of infrastructure nodes arranged at intersections of a grid structure on a first surface and configured to provide access points of the network, and client devices on a second surface, the grid structure including a quadrilateral having an x-axis dimension equal to d1, a y-axis dimension equal to d2, and a diagonal dimension equal to d3, where d2 is greater than or equal to d1. The infrastructure node includes a downward facing optical wireless transducer, the transducer being configured to have a coverage area having at least two concentric segments, and the outermost segment of the at least two concentrically arranged segments being dimensioned such that when a client device is positioned on a second surface parallel to the first surface and at a distance, the coverage area of the segment has a maximum diameter (Ro) greater than 0.5*d3 on the second surface.

[0056] In some embodiments, the distance (h) may have a value between d1 and 1.5*d1. In some embodiments, the distance (h) may have a value between 1.5*d1 and 2.25*d1.

[0057] In any of the above or other aspects described herein, the transducer of the client device may include a receiver, in which case the optical wireless signal may include a downlink signal from the network to the client device. Alternatively or additionally, the transducer of the client device may include a transmitter, in which case the optical wireless signal may include an uplink signal from the client device to the network.

Brief Description of the Drawings

[0058] For the purpose of assisting in the understanding of the present disclosure and showing how embodiments may be implemented, by way of example, the accompanying drawings are referred to. [Figure 1] FIG. 1 shows an environment having a LiFi system including a LiFi client device and a LiFi infrastructure having a plurality of LiFi access points. [Figure 2] FIG. 2 shows an environment having a LiFi system including a LiFi client device and a LiFi infrastructure having a plurality of LiFi access points, where two access points and the client device each have a coverage area. [Figure 3] FIG. 3 shows a plan view showing the coverage areas of the individual access points of the infrastructure of FIGS. 1 and 2 and how they can be arranged to cover a larger area. [Figure 4A] FIG. 4A shows an example of downlink interference where a LiFi client device is in an overlapping coverage area of a plurality of optical downlinks and is subject to interference when these LiFi access points transmit simultaneously. [Figure 4B] FIG. 4B shows an example of uplink interference where uplink interference occurs at a LiFi access point when another LiFi client device is transmitting to the same LiFi access point while a LiFi client device is transmitting a signal to the LiFi access point. [Figure 5] Figure 5 shows a schematic diagram of an optical wireless communication system. [Figure 6] Figure 6 shows three examples of how a LiFi sensor can be configured to form optical segments in the coverage area of the sensor. [Figure 7] Figure 7 shows an example of a LiFi system including a LiFi device sensor coverage area with concentric segments and an access point infrastructure. [Figure 8] Figure 8 shows a side view of a LiFi system showing the distance h between the first and second faces of the exemplary system shown in Figure 7, the corresponding optical coverage angle α for a segment having a maximum diameter Ri, and the corresponding coverage angle β for a segment having a maximum diameter Ro. [Figure 9] Figure 13 shows an example of a LiFi system including a LiFi device sensor coverage area with concentric segments and circumferential segments and an access point infrastructure. [Figure 10A] Figure 10A shows an exemplary LiFi system including two LiFi access points each having a coverage area, and a client device having a sensor coverage area including a first segment, a second segment, and a boundary between the first segment and the second segment, wherein the LiFi access point coverage areas both overlap the boundary. [Figure 10B] Figure 10B shows the exemplary LiFi system of Figure 10A including a separation wall along the boundary. [Figure 11] Figure 11 shows a LiFi device sensor coverage area (the outermost concentric segment including circumferential segments) including six circumferential (or type B) segments and two concentric (or type A) segments.

DETAILED DESCRIPTION OF THE INVENTION

[0059] It is beneficial for a LiFi client device to transmit a modulated optical signal in a limited coverage area (optical beam). This saves power, improves the signal-to-noise ratio, enables better separation of communication links, and reduces interference.

[0060] The inventors have recognized that a LiFi client device can be designed to solve one or more of the other problems as described above for a typical wireless optical communication system by designing a sectorized LiFi client device (for example, having multiple LiFi transceivers) where each "sector" covers a different part of the total coverage area of the LiFi client device. For example, these can be as follows.

[0061] Coverage - The LiFi access point may provide complete coverage on a second surface. However, a LiFi client device on the second surface may not be able to establish a communication link to the LiFi access point if the client device on the first surface including the LiFi access point has a coverage area that is too small.

[0062] Power consumption - A LiFi client device having a transceiver that covers a large area may consume a lot of power and generate a lot of heat. This may not make it a useful device for the user as it may shorten the battery life too much and become uncomfortably hot during use.

[0063] Downlink interference - LiFi client devices in the overlapping coverage areas of multiple optical downlinks are interfered with when these LiFi access points transmit simultaneously. For example, referring to FIG. 4A, the first LiFi client device 106a establishes a communication link with the first access point 104a, and the second LiFi client device 106b establishes a communication link with the second access point 104b. Since the first device is also in the coverage area of the second access point 104b, this second access point 104b interferes with the downlink communication of the first access point 104a to the first device 106a. An object of an embodiment of the present invention is to mitigate or prevent this downlink interference in the device 106a.

[0064] Uplink interference - When a LiFi client device transmits a signal to a LiFi access point, uplink interference occurs because another LiFi client device is transmitting to the same LiFi access point. For example, referring to FIG. 4B, the first LiFi client device 106a establishes a communication link with the first access point 104a, and the second LiFi client device 106b establishes a communication link with the second access point 104b. Since the second access point 104b is also in the coverage area of the first device 106a, the first device 106a interferes with the uplink communication of the second device 106b to the second access point 104b. An object of an embodiment of the present invention is to mitigate or prevent this uplink interference in the second access point 104b.

[0065] Handover - A LiFi client device moving from the coverage area of one LiFi access point to an adjacent LiFi access point may experience a period during which the LiFi client device has no connection. For example, this can occur when there is not enough time available to prepare and establish a link to the new LiFi access point before the link to the existing LiFi access point is disconnected.

[0066] The LiFi client device moves within the plane of the second surface and, therefore, may change its position within the coverage area of the LiFi access point and may also change the position of its coverage area on the first surface. Also, the LiFi client device may have different vertical positions with respect to the second surface.

[0067] FIG. 5 shows a schematic diagram of an optical wireless communication system 500. The system includes one or more access points 502a, 502b located on a first surface. Each access point provides respective coverage areas 504, 508 on a second surface by emitting an optical beam to transmit data. Also, the system includes a LiFi client device 510 on the second surface. The LiFi client device 510 includes a sensor 513 configured to provide a coverage area 514 on the first surface. The access points 502a, 502b may be connected to one or more infrastructure modems (not shown). Also, each access point 502a, 502b may be connected to a network 512.

[0068] The LiFi modem (not shown) can be connected to a single LiFi access point of the infrastructure or to multiple LiFi access points of the infrastructure (for example, one or more access point transceivers can be connected to one or more LiFi modems). Thus, in some embodiments, a single LiFi access point may be connected to multiple LiFi modems. The modem may treat multiple transceiver signals for establishing a communication link as one coherent signal, or may treat them (at least partially) as separate incoherent signals. Therefore, the modem may transmit the same data signal from all the connected access points, or may transmit a part of the same data via different signals of different connected access points. Therefore, a single modem may be the only modem connected to multiple access points, or a single modem may be connected to multiple access points, and each of the multiple access points may be connected to multiple other modems.

[0069] The LiFi receiver device 510 can be any of the above-described devices capable of receiving data transmitted by the optical wireless transmission method. For example, it may be an electronic device such as a laptop, a tablet, a smartphone, etc. It should be understood that any LiFi device including a suitable optical sensor 513 can receive data via this system 500. That is, any suitable optical sensor 513 can convert the incident light beam into a data signal for processing. The optical sensor 513 may be a dedicated photocell (point detector), or may include an array of photocells (pixels) and a lens for forming an image on the array. The optical sensor 513 may be a dedicated photocell (point detector), or may be an array of photocells included in a dongle that plugs into a receiver device 510 such as a smartphone, a tablet, or a laptop. This enables the LiFi receiver device 510 to receive data via the light beam. Also, the receiver 510 may transmit data by emitting a light beam for transmitting the data.

[0070] The controller 516 may be operably coupled to at least two access points 502a and 502b and may be configured to provide control data to one or more access points and one or more modems. The controller 516 may be connected to a plurality of modems (either via separate lines or, for example, via an Ethernet (registered trademark) switch), and the modems may be connected to a plurality of transceivers / optical frontends. This means that the controller may directly control the modems or may control the transceivers via the modems.

[0071] Sensor 513 is oriented upward in system 500 as shown in FIG. 5. In system 500 illustrated in FIG. 5, optical wireless signals are transmitted by access points 502a and 502b positioned on the ceiling. Therefore, the transmitter is positioned in a downward facing direction, and thus the sensor is required to be positioned in an upward facing direction. That is, the sensor detects light hitting or incident on the sensor from above, for example, in the direction of gravity. Therefore, the sensor is said to be upward facing. In certain embodiments, the term "upward" may simply mean towards the light source, e.g., an infrastructure transmitter or access point (i.e., a node of the network), and may mean towards the direction in which light transmission can come from, regardless of what the direction is. For example, the term "facing" is used to mean that the relevant item (e.g., the area of the sensor used for light detection) is pointing towards the (plural) access points such that the transmitted light emitted from the access points is optimally detected.

[0072] FIG. 5 shows an example of a wireless optical data transmission system 500 including a plurality of access points 502a, 502b. Each access point is connected to a controller 516. The connection of each access point to the controller 516 may be realized by connecting the access points to each other, e.g., by being chained together or connected in series by each connection (in this case, only one of the access points is directly connected to the controller 516), or by connecting each access point to the controller 516 via individual separate connections as shown in FIG. 5, or by any combination of these two. In certain embodiments, the controller 516 may be distributed and partially located within each of the access points 502a, 502b of system 500.

[0073] The LiFi device may have a single LiFi device modem (not shown) for transmitting and receiving data. Further, the LiFi device may have one or more LiFi client device transmitters and one or more LiFi client device receivers (e.g., sensors) connected to the LiFi client device modem via a multiplexer. The receiver (e.g., sensor) and the transmitter form part of the transceiver of the client device.

[0074] For the purpose of discussing the shape of the coverage area of a LiFi device sensor, it is assumed that the sensor coverage area shape is mirrored by the sensor device providing it. However, it should be understood that the shape of the coverage area may be provided by any configuration of one or more sensors or sub-sensors of the LiFi device to provide one or more desired segments of the coverage area belonging to the LiFi client device sensor, and these themselves may be of different shapes or arrangements. A segment may be composed of a plurality of photodiodes (e.g., centered and around the center) and a single optical lens. A segment may be composed of at least two photodiodes each having a different lens, for example, having no particular spatial relationship, one for the innermost segment and one for the outermost segment. A segment may be made using a combination of these methods. For example, a plurality of photodiodes arranged centered and around the center may be used, but each may have a different lens, one for the innermost segment and one for the outermost segment. The sensors or sub-sensors may be physically separated, but there may be no gap between them (e.g., between sensors or sub-sensors providing one or more of different coverage area segments), or there may be a very small gap. The optical lens may direct each segment of the coverage area of the sub-sensor to a specific position. In some embodiments, the coverage area of the outermost concentric segment may have overlapping adjacent circumferential segments within the coverage area.

[0075] Figure 6 shows three examples of how one or more LiFi sensors can be configured to form optical segments in the coverage area of the sensor. For example, each segment may have its own coverage area on the first surface that is smaller than the total coverage area of the one or more LiFi device sensors on the first surface. This configuration can be used to reduce interference in the downlink communication of multiple LiFi access points when a LiFi client device is present in the overlapping coverage areas of multiple LiFi access points.

[0076] To prevent or at least reduce interference in the downlink communication of multiple LiFi access points, the segments can be configured such that at least one segment or a combination of segments is selected to have a coverage area in a first planar area where only a single LiFi access point appears. For example, referring back to FIG. 5, it can be seen that sensor 513 has a coverage area where both access points 502a and 502b appear. Thus, by segmenting the coverage area, different LiFi downlink signals from different access points can be received by sensors responsible for providing different segments of the sensor coverage area.

[0077] Similarly, one or more LiFi client device transmitters may be configured into optical segments, each having a small coverage area on a first face, to reduce interference in the uplink communication of multiple LiFi client devices when a LiFi access point exists in the overlapping area of the multiple LiFi client devices. This also enables the uplink power to be reduced because each uplink signal requires less power to cover a smaller coverage area. To resolve or at least reduce interference in the uplink communication of multiple LiFi devices, the segments can be sized and configured such that at least one of them can be selected as having a coverage area on a first face where only a single LiFi access point appears.

[0078] The total coverage area of the LiFi client devices on the first face is represented by circles in FIGS. 2-3, 5-7, 9, 10A, and 11. However, this is only an example of the coverage area shape and any other suitable polygon shape may be used.

[0079] In FIG. 6, an exemplary configuration of segments of the coverage area of the sensor is as follows.

[0080] Exemplary type "A" configuration of concentric segments, e.g., a central segment and one or more ring segments. That is, the boundary of each segment is determined by inner and outer concentric circles or polygons.

[0081] Exemplary type "B" configuration of angular segments or pie segments. That is, the boundary of each segment is determined by a central and an outer circle or polygon, with additional radial lines having a specific angle between them.

[0082] An exemplary combination of type A and type B configurations of angular segments and concentric segments forming an A+B type configuration. That is, the concentric segments are formed between concentric circles or polygonal boundaries, and one or more of the concentric segments are further divided into circumferential segments by a radial line or a part of a radial line. For example, the configuration denoted as A+B shown at the right end of FIG. 6.

[0083] In some embodiments, the segments may have some overlap. The overlap may assist in processes such as handover of data exchange between a client device and an infrastructure transceiver (network node) from one segment to another adjacent segment. The handover may be between segments of a client device or between similar segments of an infrastructure transceiver (or sensor).

[0084] Alternatively or additionally, the segments may have an underlap. That is, there may be a gap between one segment and another segment. The gap between segments may be provided by another segment that is inactive between active segments. The inactive segment may overlap with adjacent active segments, but the active segments may not overlap. There may be a gap between one segment and another segment while there may be an overlap between other segments.

[0085] Certain combinations of the above-described configurations may be used in a multi-segment coverage area sensor such that adjacent segments may be used to create segment clusters. That is, multiple segments may be combined together, for example, by overlapping them or activating segments that are already overlapping, while gaps may be left between different clusters of segments, for example, by designing a gap between a segment or segment cluster, or deactivating a particular intermediate segment. These types of configurations may be used to form various combinations of segments to provide minimal interference and optimal utilization of energy, for example, in a client device, by using fewer segments to detect only the visible portion of the transmission from an access point towards the client device.

[0086] FIG. 7 shows a LiFi system 500 including an access point infrastructure 502 and a LiFi device 513. The infrastructure includes LiFi infrastructure transceivers 502a, 502b, and 502c. The access points 502 are at the vertices of a rectangular grid 702, and each rectangle of the grid 702 has side dimensions d1 and d2, and a diagonal dimension d3. The short side of each rectangle has dimension d1, and the long side has dimension d2. In certain embodiments, d2 is greater than or equal to d1. FIG. 7 shows an exemplary infrastructure including nine access points 502 within a rectangular array. It should be understood that the access points 502 may be arranged in any regular pattern. Similarly, multiple access points may form the vertices of any type of polygon, such as, for example, a square, circle, hexagon, pentagon, octagon, triangle, etc. The regular pattern may be formed by tessellating together one or more types of polygons to cover a larger area, as illustrated in FIG. 7.

[0087] The LiFi device 513 represented by the striped circle in the upper right quadrant of the grid 702 has a total sensor coverage area 514. The outermost boundary of the coverage area 514 is indicated by a circle 704 having a radius Ro. Also, the exemplary coverage area 514 of FIG. 7 includes an inner concentric circle 706 having a radius Ri. The outermost circle 704 and the innermost circle 706 together define the boundary of the outermost type A concentric segment 708 of the coverage area 514. The area between the LiFi device 513 and the inner circle 706 defines the boundary of the innermost type A concentric segment 710 of the coverage area 514. The outermost type A segment 708 and the innermost type A segment 710 are arranged as two concentric segments.

[0088] It should be understood that the coverage area 514 may include two or more concentric segments having a plurality of concentric circles forming boundaries therebetween. The terms "outermost" and "innermost" relate to the concentric segments having the largest Ro and the smallest Ri radii, respectively.

[0089] The outermost type A concentric segment 708 may be further divided into type B segments or circumferential segments. One such circumferential segment 712 is shown in FIG. 7. The boundary of the circumferential segment 712 includes two lines 714a, 174b that extend radially outward from the client device 513 to the outermost circle 704, and the angle between the radial lines is φ. It should be understood that not only the outermost segment 708 but also any type A concentric segment may be divided into a plurality of circumferential segments.

[0090] In the exemplary circumferential segment 712 of FIG. 7, a circle 706 having a minimum diameter Ri forms the inner boundary of the segment 712. However, it should be understood that the inner boundary may be formed by the outer boundary or circle of a concentric segment other than the innermost concentric segment, i.e., the coverage area 514 may include three or more concentric segments.

[0091] As described above, by dividing the coverage area of the sensor into segments, it is possible to create a sensor area sized such that only LiFi data transmitted by one of the infrastructure transceivers is received within any one segment of the coverage area of the LiFi sensor at any given time. Thus, interference between data received from multiple transceivers is mitigated, if not completely eliminated. It is also possible to define alternative or additional constraints in the system to meet one or more relevant criteria for mitigating interference. These are discussed in turn below.

[0092] The provisions regarding the dimensions of the coverage area of the sensors of the client device 513 depend largely on the dimensions of the LiFi infrastructure. However, it is possible to determine the absolute values of these dimensions by assuming certain typical dimensions of the infrastructure. This is illustrated below in this specification.

[0093] The dimensions of the coverage area and its segments (concentric and circumferential) depend, for example, on the distances (d1, d2) between access points and the distance (h) from the client device to the access point. Shown below are examples of numerical constraints regarding the angle β formed at the sensor between the normal from the sensor plane to the plane of the coverage area and the line connecting the sensor to the maximum diameter of the coverage area (e.g., the edge of the outermost concentric circular segment), along with the infrastructure dimensions from which they are derived. In practice, these constraints apply equally to sensors on the client device or on the access point.

[0094] When h = 1.8 m, d1 = 1.8 m, and d2 = 2.7 m, β should be greater than 42°.

[0095] When h = 2.7 m, d1 = 1.8 m, and d2 = 2.7 m, β should be greater than 31°.

[0096] When h = 2 m, d1 = 1.8 m, and d2 = 2.4 m, β should be greater than 37°.

[0097] When h = 1.8 m, d1 = 1.2 m, and d2 = 1.8 m, β should be greater than 31°.

[0098] When h = 2.7 m, d1 = 1.2 m, and d2 = 1.8 m, β should be greater than 22°.

[0099] When h = 2 m, d1 = 1.8 m, and d2 = 1.6 m, β should be greater than 26.6°.

[0100] FIG. 8 shows a side view of a system 500 showing the distance h between a first surface 802 and a second surface 804, the corresponding optical coverage angle α for a segment having a maximum diameter Ri, and the corresponding coverage angle β for a segment having a maximum diameter Ro.

[0101] In the following examples used to illustrate embodiments of the present invention, it is assumed that for the LiFi infrastructure, each LiFi modem is connected to one LiFi access point (transceiver), and each LiFi access point is connected to one LiFi modem. Also, the LiFi access points are arranged at the vertices of a rectangular grid on the first surface, · The ratio of the sides of the rectangle is such that d1 ≤ d2 ≤ 1.5 * d1, · The distance from the device to the first planar area follows d1 ≤ h ≤ 1.5 * d1.

[0102] Numerical examples of these relationships are, for example, when d1 = 1.8 m, · 1.8 m ≤ d2 ≤ 2.7 m · 1.8 m ≤ h ≤ 2.7 m That is the case.

[0103] From FIGS. 7 and 8, it can be seen that by sizing the coverage area of the sensors of the LiFi client device in a specific way, e.g., with specific limitations, the number of detected LiFi access points can be controlled so as to mitigate or prevent interference.

[0104] At least one of the following constraints can be applied, and each constraint helps prevent system malfunctions in a specific way as follows.

[0105] First, in one embodiment, it is desirable for the coverage area of the LiFi sensor to always cover at least one LiFi access point. That is, no matter where the client device is located within system 500, the coverage area will overlap with at least one access point to provide LiFi data. In the exemplary system infrastructure of FIG. 7, it can be seen that the LiFi client device is farthest from all LiFi access points when it is at the center of any one of the rectangles of grid 702. Thus, using the LiFi device coverage area and the defined dimensions of grid 702, the coverage area should have a diameter larger than the diagonal dimension d3 of the rectangle to meet this specific requirement. Therefore, the diameter of the coverage area should be at least larger than 0.5 * d3. This can be correlated with the maximum dimension of the coverage area, i.e., the outermost segment 708. Therefore, the diameter Ro of the outermost segment (should be larger than 0.5 * d3) meets this specific requirement.

[0106] Considering this meaning at the lower limit of the range of h in the infrastructure of a typical example (shown in FIGS. 7 and 8 and corresponding to the maximum required value of β), the device is at the minimum distance from the first surface (including the access point), and it can be assumed that h = d1. In this case, according to the geometry of FIG. 8, β = arctan(Ro / h), or > arctan(0.5 * d3 / d1) results. d3 2 = d2 2 + d1 2 is known, and · When d2 = d1 (square grid), β > 35.3° · When d2 = 1.5 * d1 (rectangular grid), β > 42.0° is the case.

[0107] Second, in one embodiment, it is desirable that the coverage area of the LiFi sensor cover at most direct neighbors, i.e., LiFi access points, at any given time. That is, regardless of where the client device is located within the system 500, the coverage area should not overlap with three or more access points in any one dimension (e.g., horizontal or vertical) that provides LiFi data. In this way, only LiFi data from directly neighboring access points is detected, and it is guaranteed that data from multiple, non-adjacent access points is not detected. In the exemplary system infrastructure of FIG. 7, it can be seen that the minimum dimension of the rectangles of the exemplary grid is d1. Therefore, when a LiFi client device is positioned at a first LiFi access point, it is closest to a second LiFi access point along this d1 dimension direction. Therefore, to prevent three or more access points from being detected at least in this direction, using the LiFi device coverage area and the defined dimension of the grid 702, the coverage area should have a diameter smaller than the short side dimension d1 of the rectangle to meet this specific requirement. This can be correlated with the dimension of the overall coverage area, i.e., the outermost segment 708. Therefore, the diameter Ro of the outermost segment 708 should be smaller than d1.

[0108] (Considering this meaning at the upper limit of the range of h in the infrastructure of a typical example (shown in FIGS. 7 and 8 and corresponding to the maximum value of Ro), it can be assumed that the device is at the maximum distance from the first surface (including the access point) and h = 1.5 * d1. In this case, according to the geometry of FIG. 8, β = arctan(Ro / h), or < arctan(d1 / (1.5 * d1)) results. In this case, β < 33.7°.

[0109] Thirdly, in one embodiment, when the coverage area of the innermost segment 710 of the LiFi device is centered on one access point, it is desirable to sufficiently cover the LiFi access point so that it rarely disconnects and reconnects even when moving in a small area around the access point. The reason for this is that if the innermost concentric segment only needs to move a small amount of deviation because it is aligned with the access point before trying to disconnect or hand over to another access point, the LiFi client device may not experience a very reliable connection in a realistic use case. Thus, when the LiFi client device is positioned directly, or directly below, or parallel to the LiFi access point of the system 500, the coverage area of the innermost concentric segment should have some space within it before ceasing to cover the LiFi access point. The amount of space, and thus the minimum radius Ri of the innermost concentric segment determined accordingly, can be selected based on the expected local movement amount of the LiFi client device, or the comparative size of the device relative to the grid. For example, a mobile phone may move around on the surface of a desk. Therefore, movement within a range of 1 to 2 meters when optimally positioned relative to the access point should not trigger a disconnection.

[0110] In the exemplary system infrastructure of FIG. 7, when the LiFi client device is positioned at the central LiFi access point, the diameter of the innermost concentric segment may be selected to be greater than 0.3*d1 to provide an area around the LiFi access point within which the LiFi client device can move before a cut or handover occurs. Thus, using the LiFi device coverage area and the defined dimensions of grid 702, the innermost segment coverage area should have a diameter Ri greater than 0.3*d1. That is, the coverage area of the type-A concentric segment determined by the circle with diameter Ri should be greater than 30% of the shortest side of the rectangle, i.e., Ri>0.3*d1.

[0111] (Considering this meaning at the lower limit of the range of h in the infrastructure of a typical example (shown in FIGS. 7 and 8 and corresponding to the minimum value of Ri), the device can be assumed to be at the minimum distance from the first surface (including the access point), i.e., h=d1. In this case, according to the geometry of FIG. 8, α=arctan(Ri / h), or when restricting Ri to be greater than a value, >arctan(0.3*d1 / d1) results. In this case, α>16.7°.

[0112] The 30% selection is a selection according to the factors described above. The selected percentage of d1 can equally be 5%, 10%, 15%, etc., depending on, for example, the system configuration, infrastructure configuration, and type of LiFi client device used.

[0113] Fourthly, in one embodiment, it is desirable that the coverage area of the innermost segment 710 of the LiFi sensor covers only one LiFi access point at any given time. This is to prevent interference in this central segment that can be used as the main coverage area segment for data transfer.

[0114] Furthermore, it is desirable to have some gap before the innermost segment encounters another second LiFi access point. The reason for this is that if the innermost concentric segment only needs to move a small deviation since it is aligned with the access point at the center before encountering another access point, the LiFi client device may attempt to initiate a pre-emptive process for handover to this other LiFi access point or execute a handover. If the LiFi client device frequently moves to neighboring access points and then continues to move around and out of the coverage area, the handover process may cause confusion in the connection. For example, it may take a long time to execute the handover, move during the handover and be completely disconnected from the network, or the processing power may be unnecessarily occupied to execute these undesirable processes. Thus, when the LiFi client device is positioned directly, immediately below, or parallel to the LiFi access point of the system 500, the coverage area of the innermost concentric segment should have some space around it before covering the next nearest LiFi access point. The amount of space and the corresponding maximum diameter Ri of the innermost concentric segment can be selected based on the expected local movement amount of the LiFi client device or the relative size of the device to the grid. For example, a mobile phone may move around on the surface of a desk. Therefore, movement within a range of 1 to 2 meters when optimally positioned relative to the access point should not trigger a handover.

[0115] In the exemplary system infrastructure of FIG. 7, when a LiFi client device is positioned at the center on the d1 dimension of the grid between two LiFi access points, it can be seen that the innermost concentric segment should have a diameter smaller than d1 to prevent the innermost segment of the coverage area from covering two LiFi access points at once. Thus, using the LiFi device coverage area and the defined dimensions of grid 702, the innermost segment coverage area 710 should have a diameter Ri smaller than d1 / 2 or 0.5*d1 to meet this specific requirement.

[0116] Considering this meaning at the upper limit of the range of h in the infrastructure of a typical example (shown in FIGS. 7 and 8 and corresponding to the maximum value of Ri), it can be assumed that the device is at the maximum distance from the first surface (including the access point) and h = 1.5*d1. In this case, according to the geometry of FIG. 8, α = arctan(Ri / h), or when restricting Ri to a value smaller than, <arctan(0.5*d1 / 1.5*d1) it follows. In this case, α < 18.4°.

[0117] Fifthly, in one embodiment, it is desirable that the circumferential segments in the A + B type configuration of the LiFi sensor cover only one LiFi access point at any given time. By implementing the circumferential segments, the outermost concentric segment can be more advantageously dimensioned to cover only one LiFi access point at a time, rather than according to the above criterion of covering only directly neighboring LiFi access points. That is, regardless of where the client device is positioned within system 500, the coverage area of the circumferential segments will cover only one access point to provide LiFi data.

[0118] In the exemplary system infrastructure of FIG. 7, it can be seen that the LiFi client device is farthest from all LiFi access points when it is at the center of any one of the rectangles of the grid 702. However, this is also the position where the outermost concentric segment is most likely to cover multiple LiFi access points. By dividing the outermost concentric segment (and in embodiments having two or more concentric segments, other concentric segments) into circumferential segments, the coverage area can be reduced to cover only one LiFi access point. Thus, using the LiFi device coverage area and the defined dimensions of the grid 702, the radial lines defining the sides of the circumferential segments should connect an outer circle with a radius 0.5*d3 < Ro < d1 and an inner circle with a radius 0 < Ri < d1 / 2 and be separated by an angle φ.

[0119] Considering this meaning at the upper limit of the range of h in the infrastructure of a typical example (shown in FIGS. 7 and 8 and corresponding to the maximum value of φ), the device is at the maximum distance from the first surface (including the access point), and it can be assumed that h = 1.5*d1. In this case, according to the geometry of FIG. 8, assuming Ro = d1 (as the maximum value), φ = 2*arcsin(0.5*d1 / Ro), or when φ is smaller than the value, < 2*arcsin(0.5*d1 / Ro), it follows. In this case, φ < 60°.

[0120] Sixthly, in an embodiment, it may be desirable to have "x" evenly distributed circumferential segments. These circumferential segments may have an overlap over an angle θ with adjacent circumferential segments. The general formula is x ≧ (360 / (φ - θ), it follows.

[0121] Considering this meaning at the upper limit of the range of h in the infrastructure of a typical example (shown in FIGS. 7 and 8 and corresponding to the maximum value of φ), the device is at the maximum distance from the first surface (including the access point), and it can be assumed that h = 1.5 * d1. In this case, according to the geometry of FIG. 8, assuming Ro = d1 (as the maximum value), x ≥ (360 / (60 - θ)), and when rounded to the nearest angle, · When θ = 0°, x ≥ 6 · When 1° ≤ θ ≤ 8°, x ≥ 7 · When 9° ≤ θ ≤ 16°, x ≥ 8 and so on.

[0122] FIG. 9 shows an exemplary system similar to FIG. 7. However, the coverage area 514 of the LiFi device has the outermost concentric segment 708 divided into three overlapping circumferential segments 902a, 902b, and 902c.

[0123] It can be seen whether dividing a concentric segment of type A into a plurality of circumferential segments of type B can help isolate (isolate) the LiFi data signals received from different LiFi access points to only one segment when detected by the LiFi device. In FIG. 9, it can be seen that when the LiFi client device moves upward and to the left, segment 902a is likely to cover the LiFi access point 502b and its immediate neighbor 502d. This can be mitigated by simply increasing the number of circumferential segments, as shown in later examples of segment configurations.

[0124] Numerical values or ranges for a typical environment may be given, and the numerical values and ranges for the above criteria may be determined.

[0125] For example, when the ceiling height of a typical room is 2.9m and the height of a typical desk is 0.6m to 0.9m, the distance h between the plane of one or more LiFi access points (502) and the plane of, for example, a desk (thus, the LiFi client device 513) can be estimated to be between 2.3m and 2.0m. In certain embodiments, when d1 is equal to 1.8m, the value of h may be between 1.8m and 2.7m as shown below. Thus, using the above constraints on the dimensions of the system with respect to d1 and d2, an estimated value of d2 can also be calculated. The following provides the possible numerical ranges for various dimensions and angles of the system 500. For example, when h is between 1.8m and 2.7m, typically around 2.0m to 2.3m.

[0126] Dimensions · d1 < d2 < 1.5*d1 → 1.8m < d2 < 2.7m, typically 2.4m · d1 < h < 1.5*d1 → 1.8m < h < 2.7m, typically 2.0m to 2.3m · d1 = 1.8m

[0127] Coverage Using the criteria described above to create a coverage area segment with sufficient coverage · Ro of sufficient size > 0.5*d3 → At h = 1.0*d1 (1.8m), d2 = 1.5*d1 (2.7m), β > 42° At h = 1.5*d1 (2.7m), d2 = 1.5*d1 (2.7m), β > 31° Therefore, typically, when h = 2.0m, d2 = 2.4m, β > 37° · Ri of sufficient size > 0.3*d1 → At h = 1.0*d1, α > 16.7°

[0128] No Interference Using the criteria described above to create a coverage area segment with minimal interference · Ro not too large < d1 → At h = 1.5 * d1 (2.7 m), β < 33.7° At h = 1.0 * d1 (1.8 m), β < 45° Therefore, typically, at h = 2.3 m, β < 38° · φ not too large → At Ro = d1, φ < 60° - overlap At Ro = 1.5 * 0.5 * d3, φ < 43.4° - overlap This satisfies the case where β = 42° (Ro = 0.5 * d3) at h = 1.8 m and is derived by applying it at the maximum distance h = 2.7 m (= 1.5 * 1.8 m) → Ro = 1.5 * 0.5 * d3 · Ri not too large < 0.5 * d1 → At h = 1.5 * d1, α < 18.4°

[0129] Thus, the angle defining the boundary of the inner concentric segment should be α or less. Also, α may define the inner boundary of the outermost concentric segment

[0130] In another exemplary embodiment calculated below, the dimension d1 may be equal to 1.2 m and d2 may be in the range of 1.2 - 1.8 m. This may be relevant to some cases where an extra LiFi access point is positioned between two LiFi access points spaced 2.4 m apart. A typical ceiling height is assumed to be about 2.9 m

[0131] The advantage of a smaller d1 (1.2m instead of 1.8m) is that the coverage area of the sensors of the client device can be made smaller. With a smaller coverage area, the client device requires less power for transmission or can achieve a higher bit rate. Also, the client device itself can be made smaller, or the sensors can be made small enough to fit into a small device. This can also apply to the sensors of the access point or other infrastructure components.

[0132] Dimensions · d1 < d2 < 1.5 * d1 → 1.2m < d2 < 1.8m · 1.5 * d1 < h < 2.25 * d1 → 1.8m < h < 2.7m, typically 2.0 - 2.3m · d1 = 1.2m The multiplication of d1 to obtain the range of h is found by making the typical ceiling height the same.

[0133] Coverage · A sufficiently large Ro > 0.5 * d3 → At h = 1.5 * d1, d2 = 1.5 * d1, β > 31° At h = 2.25 * d1, d2 = 1.5 * d1, β > 22° Therefore, typically at h = 2.0m, d2 = 2.4m, β > 26.6° · A sufficiently large Ri > 0.3 * d1 → At h = 1.5 * d1, α > 11.3°

[0134] No interference Using the criteria described above to create a coverage area segment with minimal interference, · Ro not too large Ro < d1 → At h = 2.25 * d1, β < 24° At h = 1.5 * d1, β < 33.7° Therefore, typically at h = 2.3m, β < 27.6° · φ not too large → At Ro = d1, φ < 60° - overlap At Ro = 1.5 * 0.5 * d3, φ < 43.4° - overlap This satisfies the case where β = 42° (Ro = 0.5 * d3) at h = 1.8m, and is derived by applying it at the maximum distance h = 2.7m (= 1.5 * 1.8m) → Ro = 1.5 * 0.5 * d3. · Ri not too large < 0.5 * d1 → At h = 2.25 * d1, α < 12.5°

[0135] Thus, the angle defining the boundary of the inner concentric segment should be α or less. Also, α may define the inner boundary of the outermost concentric segment.

[0136] That is, generally in the case of an infrastructure having a rectangular grid with d1 = 1.8m, 1.8m < d2 < 2.7m. Typical values are such that the system 500 · By taking typical values of the first and second requirements, enables defining the range of β · If the second requirement cannot be satisfied, enables hardening the third requirement. For example, although Ro < d1, the LiFi device is centered on the LiFi access point, that is, when the LiFi access point does not enter the outermost concentric segment. · Enables defining the inner diameter of the outer ring. For example, Ri may be considered as the innermost boundary of the outermost concentric segment in a certain embodiment.

[0137] First requirement: The required angle β for the outer circle with diameter Ro should be large enough (Ro > 0.5 * d3) β > 42° (worst case) β > 37° (typical case)

[0138] Second requirement: The necessary angle β for the outer circle with diameter Ro should not be too large (Ro < d1). This ensures that there is only a direct neighbor LiFi access point in the outermost concentric segment coverage area, otherwise the interference processing will become complicated. This is particularly relevant for type A or concentric-only segments. When the outer ring is segmented into circumferential segments (type A + type B), the coverage area of each segment becomes angularly smaller, so the second requirement is less relevant. β < 33.7° (worst case) β < 38° for distance (typical case)

[0139] The first requirement and the second requirement may be combined.

[0140] In the worst case when the first requirement and the second requirement are combined, β > 42° and β < 33.7° must hold, which is contradictory. This can be solved by aiming for a typical case or by adding circumferential segments to the outer ring.

[0141] In a typical case, a small range can be defined: 37° < β < 38°

[0142] Third requirement: The angle φ of the circumferential (type B) segment should be small enough to prevent multiple LiFi access points from appearing within the coverage area of such a segment. a) When the second requirement is just met, φ < 60° b) When the second requirement is not met but the first requirement is met, φ < 43°

[0143] The value in b) satisfies the case of β = 42° (Ro = 0.5 * d3) at h = 1.8m and is derived by applying it at the maximum distance h = 2.7m (= 1.5 * 1.8m), Ro = 1.5 * 0.5 * d3.

[0144] The angle α required for the innermost segment, defined by a circle with radius Ri, has no conflicting worst - case requirements. The range can be 16.7° < α < 18.4°.

[0145] In summary, a dongle or other client device may create a segmented coverage area that forms segments. The segments should be small enough so that it is possible to select at least one segment that covers only a single LiFi access point. The dongle should be able to detect LiFi access points (and for example, a LiFi modem) and select one or more segments to provide an interference - free communication link to a single LiFi modem (e.g., via one or more segments or LiFi access points).

[0146] FIG. 10A shows two LiFi access points 502a, 502b having respective coverage areas 1002a, 1002b. At the boundary 1004 between the first segment 902a and the second segment 902b, it can be seen that the LiFi access point coverage areas 1002a and 1002b overlap the boundary. As a result, both segments 902a and 902b detect a portion of the LiFi data signals from both LiFi access points. This cross - detection of LiFi access points can cause interference between the two LiFi data signals received in any segment of a LiFi client device. One way to reduce this interference is shown in FIG. 10B.

[0147] Figure 10B shows an embodiment in which a low separating wall is disposed along the boundary 1004. The purpose of this boundary 1004 is to perform a kind of collimation of the received LiFi data signals from two different LiFi access points. For example, the wall between the two segments 902a and 902b may shadow off or block out the LiFi signal of the right hand access point 502b from reaching the left hand segment 902a. If the wall is made of a reflective material, the blocked light may be reflected from the wall. When correctly angled, the light may even be reflected downward towards the right hand segment 902b. The right hand segment 902b is where most of the LiFi signal of the right hand access point 502b will fall in any case, and thus this re - direction can serve to conserve energy by not wasting this reflected portion of the LiFi data signal. Such a collimator can increase the directional specificity along with the effectiveness of a single segment of such segmented sensors.

[0148] Figure 10B shows such a collimating structure 1006 from the perspective of the cut line A in Figure 10A. The structure shown is, in one embodiment, a wall 1006 disposed on a segment boundary 1004 that blocks LiFi data signal light from an adjacent segment (reducing interference in the adjacent segment). In a further embodiment, the LiFi light is reflected back to the associated sensor segment, increasing the efficiency there. The angle and reflectivity of the wall can be designed to achieve optimal optical performance. An exemplary implementation may include a wall at an angle of 10° with respect to the orthogonal direction of the LiFi data signal light. This is merely exemplary, and it should be understood that other angles may be selected to optimize the reflection angle of the LiFi data signal for optimal reception by the segment into which the LiFi data signal is reflected. It should also be understood that the degree of reflection may be selected according to the design of the sensors and systems used. The reflective material enables the scavenging of LiFi light that would otherwise be lost. Also, in this way, only the light within a certain incident angle is redirected to strike the surface of the sensor segment.

[0149] As described above, another way to reduce cross sector interference (e.g., other than the collimating wall described above) may be to have an area between segments that does not contribute to the signals received by any segment (e.g., blanked, blocked or screened off in some way). Using the same scenario as in FIG. 10A, the light from the right hand access point 502b falls into such a passive area around the boundary 1004 and thus does not cause any interference in the left hand segment 902a. This may be provided by the addition of an intermediate segment as described above to create a gap between the left and right segments. As a further result, in the scenario of FIG. 10A, less of the light from the left hand access point 502a will cause interference in the right hand segment 902b.

[0150] In one embodiment, the LiFi client device may include a number of circumferential segments (in addition to at least two concentric segments) each of which may provide a different communication exchange. That is, each LiFi segment may be a transceiver and may include a LiFi transmitter and a LiFi receiver having the same or similar coverage.

[0151] In one embodiment, the LiFi client device may include a number of circumferential segments (in addition to at least two concentric segments). In this case, since the coverage area of each segment will necessarily be small (e.g., to fit within 360°), interference can be addressed in many situations. That is, a number of circumferential segments are used to cover 360° such that each segment is a small part of the 360°. Thus, it becomes easier to select a single LiFi segment that covers only a single LiFi access point.

[0152] In one embodiment, the LiFi client device may be capable of combining two or more segments. For example, this may be the case when a LiFi access point is detected at the boundary between two segments. For example, when a LiFi device having six circumferential segments as shown in FIG. 11 is provided, any rotation of the device will not lead to an interference problem caused by the LiFi signal being detected in the same segment from different LiFi access points. That is, there will always be a segment having a coverage area where only a single LiFi access point appears. In a situation where the access point appears at the boundary between two segments, the LiFi client device may combine the two segments as if they were one large segment in order to receive more LiFi data signals transmitted by the access point.

[0153] It can be seen that it is advantageous to have a single central concentric segment of a sensor without circumferential segments. For example, if a sensor configuration with only circumferential type B segments as shown in FIG. 6 is positioned directly above the LiFi access point, the device will have to use one or a combination of type B segments to receive the LiFi data signal. Further, if the device moves around an area directly surrounding the LiFi access point, the LiFi access point will move between different type B segments, so it will continuously move into different segments of the coverage area. Of course, it would be possible to select all circumferential type B segments to avoid many of these changes, but this may result in using more power as all segments would have to be used at once. Thus, in the above-described embodiment where the device sensor includes at least two concentric type A segments and a plurality of circumferential type B segments, a good balance is achieved between the size and positioning of the individual segments, and these can be configured to be used together or separately for many different LiFi system configurations.

[0154] In one embodiment, different segments may be used to trigger a pre - established process for handover to the next LiFi access point. In FIG. 11, when the LiFi device 513 moves towards the upper - right LiFi access point 502b as shown by the arrow 1102, one of the circumferential segments, as shown by the left - most segment 1104, can take over the communication. The upper - right access point 502b enters the coverage area of the right - most segment 1106. As a result of the access point 502b entering the segment 1106, the device may start preparing for handover to this access point 502b by pre - establishing a communication link with this access point 502b via the right - most segment. If the LiFi device further moves and loses the communication link with the original LiFi access point 502a, it can quickly change to perform further communication via the new right - hand LiFi access point 502b.

[0155] In one embodiment, the LiFi device may include a plurality of concentric and circumferential segments, each covering a different portion of the coverage area of the LiFi device sensor for communication purposes, and all segments may have some overlap. In one embodiment, each segment is provided by a LiFi transceiver including a LiFi transmitter and a LiFi receiver having the same or similar coverage. The overlap of the segments enables the LiFi device to select a single transceiver or a combination thereof to provide a communication link with the LiFi access point. For example, the selection of the combination may be in response to the LiFi access point being near the boundary of the coverage areas of two segments. FIG. 11 shows a LiFi device sensor coverage area including six circumferential (or type B) segments and two concentric (or type A) segments (the outermost concentric segment including the circumferential segments), and all segments may additionally have some overlap between their coverage areas (not shown). In such a situation, the LiFi device may choose to communicate via either a single segment (concentric or circumferential) or a combination thereof.

[0156] It should be understood that the above embodiments are described by way of example only.

[0157] It should be understood that the embodiments have been illustrated from the perspective of specific ranges of h and d1, and what is more relevant is the relative ratio of these dimensions, and the absolute values are not limiting.

[0158] More generally, according to one aspect disclosed herein, a client device for use in an optical wireless communication network, the client device includes a transceiver configured to receive data via an optical wireless connection (and optionally transmit data via an electromagnetic wireless connection), and the transceiver includes an upward facing sensor configured to detect optical wireless transmissions, and the sensor is configured to have a coverage area having at least two concentric segments. A portion of the sensor configured to provide the outermost segment of the at least two concentric segments is dimensioned in certain embodiments such that any one or more of the following may apply.

[0159] a) An angle at the sensor between the outer edge of the outermost segment and the normal to the surface of the sensor, where the surface of the coverage area is perpendicular to the normal and at a distance from the sensor, the angle may be greater than 31°, optionally greater than 42°, or An angle at the sensor between the outer edge of the outermost segment and the normal to the surface of the sensor, where the surface of the coverage area is perpendicular to the normal and at a distance from the sensor, the angle may be greater than 22°, optionally greater than 31°.

[0160] b) A portion of the sensor configured to provide the outermost segment of the at least two concentric segments is An angle at the sensor between the outer edge of the outermost segment and the normal to the surface of the sensor, where the surface of the coverage area is perpendicular to the normal and at a distance from the sensor, the angle is less than 45°, optionally less than 33.7°, or An angle at the sensor between the outer edge of the outermost segment and the normal to the surface of the sensor, where the surface of the coverage area is perpendicular to the normal and at a distance from the sensor, the angle is less than 33.7°, optionally less than 24°. It may be dimensioned as follows.

[0161] c) The part of the sensor configured to provide the outermost segment of at least two concentric segments is such that the outermost segment of the at least two concentrically arranged segments is divided into further segments in the circumferential direction, and each further segment is bounded by the maximum diameter of the outermost concentric segment, the maximum diameter of the innermost concentric segment, and two radial lines extending from the center of the coverage area to the maximum diameter of the outermost segment, and the two radial lines are dimensioned to be spaced apart by an angle (φ) less than 43.4°, optionally, the two radial lines may be dimensioned to be spaced apart by an angle (φ) less than 43°.

[0162] d) The part of the sensor configured to provide the outermost segment of at least two concentric segments is such that the outermost segment of the at least two concentrically arranged segments is divided into further segments in the circumferential direction, and each further segment is bounded by the maximum diameter of the outermost concentric segment, the maximum diameter of the innermost concentric segment, and two radial lines extending from the center of the coverage area to the maximum diameter of the outermost segment, and the two radial lines are dimensioned to be spaced apart by an angle (φ) less than 60°.

[0163] e) The part of the sensor configured to provide the outermost segment may be dimensioned such that the circumferential segments overlap with an adjacent circumferential segment by an angle (θ).

[0164] f) The part of the sensor configured to provide the innermost segment of at least two concentric segments is an angle in the sensor between the outer edge of the innermost segment and the normal to the surface of the sensor, where the surface of the coverage area is perpendicular to the normal and at a certain distance from the sensor, and the angle is between 16.7° and 18.4°, or The angle in the sensor between the outer edge of the innermost segment and the normal to the surface of the sensor, where the surface of the coverage area is perpendicular to the normal and at a certain distance from the sensor, is 11.3° to 12.5°. It may be dimensioned as follows.

[0165] According to another aspect provided herein, a system configured to provide an optical wireless communication network, including a plurality of infrastructure nodes disposed at the intersections of a grid structure on a first surface and configured to provide access points of the network, the grid structure including a quadrilateral (preferably, an equiangular quadrilateral, i.e., a square or an oblong rectangle) having an x-axis dimension equal to d1, a y-axis dimension equal to d2, and a diagonal dimension equal to d3, where d2 is greater than or equal to d1, an infrastructure node, and at least one client device, the client device including an upward-facing optical wireless sensor, the sensor being configured to have a coverage area having at least two concentric segments. In certain embodiments, any one or more of the following may be applicable.

[0166] g) The outermost segment of the at least two concentric segments may be dimensioned such that when the client device is positioned on a second surface parallel to the first surface and at a certain distance from the first surface, the coverage area of the segment has a maximum diameter greater than 0.5*d3 on the first surface.

[0167] h) The sensor may be configured such that the outermost segment of the at least two concentric segments is dimensioned such that when the client device is positioned on a second surface parallel to the first surface and at a certain distance from the first surface, the coverage area of the segment has a maximum diameter (Ro) with a value smaller than d1 on the first surface.

[0168] i) The sensor may be configured such that when the innermost segment of at least two concentrically arranged segments has a coverage area dimensioned to have a maximum diameter greater than 0.3*d1 on the first plane when the client device is positioned on a second plane parallel to the first plane and at a distance from the first plane.

[0169] j) The sensor may be configured such that when the innermost segment of at least two concentrically arranged segments has a coverage area dimensioned to have a maximum diameter less than half of the value of d1 on the first plane when the client device is positioned on a second plane parallel to the first plane and at a distance from the first plane.

[0170] k) The sensor may be configured such that the outermost segment of at least two concentrically arranged segments is divided into further segments in the circumferential direction, and each further segment is bounded by two radial lines extending from the center of the coverage area to the maximum diameter of the outermost concentric segment, the maximum diameter of the outermost concentric segment (Ro), the maximum diameter of the innermost concentric segment (Ri), and having an angular separation such that the chord formed between the intersection of the maximum diameter of the outermost segment and the radial lines has a length less than d1.

[0171] The above embodiments have been described from the perspective of a sensor that detects signals from a cell on the downlink. However, any of the described configurations may equally well be used in connection with a segmented transmitter of a user device configured to transmit to a cell on the uplink. Therefore, in any reference herein, the description of a sensor may more generally be replaced with a description of a transducer that may include either or both of a downlink sensor, an uplink transmitter. The use of spatial division to conserve power, reduce interference, and / or improve the link budget can be achieved on the uplink as well as on the downlink.

[0172] In some embodiments, the client device may have optical capabilities for both the uplink and the downlink. The transmitter and the receiver of the client device may each have their own lens and may be physically separated. The uplink and the downlink may use slightly different wavelengths (where similar refraction occurs by the optical system), and / or the same wavelength may be used if the uplink and the downlink are not active simultaneously. In some embodiments, the uplink and the downlink may have the same or similar total coverage area.

[0173] For example, a LiFi device may have a single LiFi device modem for transmitting and receiving data. Further, the LiFi device may have m LiFi device transmitters (LiFi-device-Tx) and n LiFi device receivers (LiFi-device-Rx) connected to the LiFi device modem via a multiplexer. According to the embodiments disclosed herein, the n LiFi device receivers are optically configured into segments, each having a small coverage area in a first planar area, in order to reduce interference of downlink communications of a plurality of LiFi-APs when a device exists in an overlapping area of the plurality of LiFi-APs. To resolve or at least reduce interference of downlink communications of a plurality of LiFi-APs, the segments can be configured such that at least one of them can be selected to have a coverage area on a first planar area where only a single LiFi-AP appears. The m LiFi device transmitters may be optically configured into segments, each having a small coverage area in a first planar area, in order to reduce interference of uplink communications of a plurality of LiFi devices when a LiFi-AP exists in an overlapping area of the plurality of LiFi devices. Also, this enables reduction of power for the uplink. To resolve or at least reduce interference of uplink communications of a plurality of LiFi devices, the segments can be configured such that at least one of them can be selected to have a coverage area in a first planar area where only a single LiFi-AP appears. The values of n and m may be different. For having similar behavior for uplink and downlink, n and m may be equal, and each of the segments of n==m may have the same or similar coverage area.

[0174] In an alternative embodiment, the client device may have only uplink optical performance, or only downlink optical performance. For example, in some cases, the client device may have only optical downlink performance, either without an uplink or with an RF uplink.

[0175] Throughout the description and claims, reference is made to transducers, and in accordance with the invention of the claims, these transducers are configured to be used within an optical wireless communication network. Accordingly, a transducer as provided herein may correspond to a (segmented) sensor such as a photodiode and / or a phototransistor for receiving an optical wireless communication signal. To correspond to the coverage area shown for reception, such a sensor may comprise an optical system, for example in the form of a lens. As contemplated by the invention of the claims, such a sensor may be configured to receive visible light or, alternatively, infrared light.

[0176] As described above, the transducer may alternatively correspond to a transmitter for use in an optical communication network, such as a light emitting diode (LED) or a laser diode. Similar to the sensor described above, such a transmitter may also be provided with an optical system, for example in the form of a lens, which can be selected to correspond to the coverage area required for transmission. As will be understood by those skilled in the art of optical wireless network design, preferably, the device according to the invention includes both a sensor and a transmitter that enable two-way communication.

[0177] Upon consideration of the drawings, the present disclosure, and the appended claims, other variations to the disclosed embodiments can be understood by those skilled in the art and can be practiced when implementing the claimed invention.

[0178] In a claim, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may perform the functions of several items recited in a claim. The mere fact that certain means are recited in mutually different dependent claims does not indicate that a combination of these means cannot be used advantageously. A computer program may be stored / distributed in a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with other hardware or as part of other hardware, but may also be distributed in other forms via the Internet or other wired or wireless electrical communication systems. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A client device for use in an optical wireless communication network, the network including a plurality of infrastructure nodes arranged at intersections of a grid structure on a first plane and configured to provide access points of the network, the grid structure including a quadrilateral having an x-axis dimension equal to d1, a y-axis dimension equal to d2, and a diagonal dimension equal to d3, d2 being greater than or equal to d1, the client device including an upward-facing optical transducer configured to detect an optical wireless transmission from the network or transmit an optical wireless transmission to the network, the transducer being configured to have a coverage area having at least two concentric segments, the portion of the transducer configured to provide the outermost segment of the at least two concentric segments being dimensioned such that when the client device is positioned on a second plane parallel to the first plane and at a distance from the first plane, the coverage area of the segment has a maximum diameter greater than 0.5*d3 on the first plane A client device dimensioned as such.

2. The portion of the transducer configured to provide the outermost segment of the at least two concentric segments is an angle between a line connecting the outer edge of the outermost segment and the center of the transducer and a normal to the plane of the transducer passing through the center of the transducer, the plane of the coverage area being perpendicular to the normal, the angle being at a distance from the transducer and greater than 31°, optionally greater than 42°, or is an angle between a line connecting the outer edge of the outermost segment and the center of the transducer and a normal to the plane of the transducer passing through the center of the transducer, the plane of the coverage area being perpendicular to the normal, the angle being at a distance from the transducer and greater than 22°, optionally greater than 31°, The client device according to claim 1, dimensioned as such.

3. The portion of the transducer configured to provide the outermost segment of the at least two concentric segments The angle between a line connecting the outer edge of the outermost segment and the center of the transducer and a normal to the plane of the transducer passing through the center of the transducer, wherein the plane of the coverage area is perpendicular to the normal and at a certain distance from the transducer, is less than 45°, optionally less than 33.7°, or The angle between a line connecting the outer edge of the outermost segment and the center of the transducer and a normal to the plane of the transducer passing through the center of the transducer, wherein the plane of the coverage area is perpendicular to the normal and at a certain distance from the transducer, is less than 33.7°, optionally less than 24°, The client device according to claim 1 or 2, dimensioned as such. **Claim 4** The portion of the transducer configured to provide the outermost segment of the at least two concentric segments is such that the outermost segment of the at least two concentrically arranged segments is divided into further segments in the circumferential direction, and each further segment is bounded by the outer edge of the outermost concentric segment, the outer edge of the innermost concentric segment, and two radial lines extending from the center of the coverage area to the outer edge of the outermost segment, and the two radial lines are dimensioned such that they are separated by an angle less than 43.4°, optionally, the two radial lines are separated by an angle less than 43°. The client device according to claim 1. **Claim 5** The portion of the transducer configured to provide the outermost segment of the at least two concentric segments is such that the outermost segment of the at least two concentrically arranged segments is divided into further segments in the circumferential direction, and each further segment is bounded by the outer edge of the outermost concentric segment, the outer edge of the innermost concentric segment, and two radial lines extending from the center of the coverage area to the outer edge of the outermost segment, and the two radial lines are dimensioned such that they are separated by an angle less than 60°. The client device according to claim 3. **Claim 6** The portion of the transducer configured to provide the outermost segment is dimensioned such that the circumferential segments overlap at an angle with an adjacent circumferential segment, the client device according to any one of claims 1 to 5.

7. The portion of the transducer configured to provide the innermost segment of the at least two concentric segments is an angle between a line connecting the outer edge of the innermost segment and the center of the transducer and a normal to the plane of the transducer passing through the center of the transducer, wherein the plane of the coverage area is perpendicular to the normal and at a distance from the transducer, the angle being between 16.7° and 18.4°, or an angle between a line connecting the outer edge of the innermost segment and the center of the transducer and a normal to the plane of the transducer passing through the center of the transducer, wherein the plane of the coverage area is perpendicular to the normal and at a distance from the transducer, the angle being between 11.3° and 12.5°, dimensioned as such, the client device according to any one of claims 1 to 6.

8. A system configured to provide an optical wireless communication network, a plurality of infrastructure nodes arranged at intersections of a grid structure on a first surface and configured to provide access points of the network, wherein the grid structure includes a quadrilateral having an x-axis dimension equal to d1, a y-axis dimension equal to d2, and a diagonal dimension equal to d3, and d2 is greater than or equal to d1, the infrastructure nodes, at least one client device, comprising, the client device includes an upward-facing optical wireless transducer for receiving an optical wireless signal from the network or transmitting an optical wireless signal to the network, the transducer being configured to have a coverage area with at least two concentric segments, The outermost segment of the at least two concentric segments is dimensioned such that when the client device is positioned on a second plane parallel to the first plane and at a distance from the first plane, the coverage area of the segment has a maximum diameter greater than 0.5*d3 on the first plane. System.

9. The outermost segment of the at least two concentric segments is configured such that when the client device is positioned on a second plane parallel to the first plane and at a distance from the first plane, the coverage area of the segment has a maximum diameter of a value less than d1 on the first plane. The system according to claim 8.

10. The innermost segment of the at least two concentrically arranged segments is configured such that when the client device is positioned on a second plane parallel to the first plane and at a distance from the first plane, the coverage area of the segment has a maximum diameter of a value greater than 0.3*d1 on the first plane. The system according to claim 8 or 9.

11. The innermost segment of the at least two concentrically arranged segments is configured such that when the client device is positioned on a second plane parallel to the first plane and at a distance from the first plane, the coverage area of the segment has a maximum diameter of a value less than half of the value of d1 on the first plane. The system according to any one of claims 8 to 10.

12. The outermost segment of the at least two concentrically arranged segments is divided into further segments in the circumferential direction, and each further segment is bounded by two radial lines extending from the outer edge of the outermost concentric segment, the outer edge of the innermost concentric segment, and the center of the coverage area to the outer edge of the outermost segment, and the chord formed between the intersection of the outer edge of the outermost segment and the radial line has an angular separation with a length less than d1. The system according to any one of claims 8 to 11.

13. The system according to claim 12, wherein each of the circumferential segments overlaps with each adjacent circumferential segment but does not overlap with any inner concentric segment.

14. The system according to claim 12, wherein each of the circumferential segments is separated from an adjacent circumferential segment by a wall perpendicular to the surface of the transducer.

15. The system according to claim 14, wherein the wall comprises a reflective material.

16. An infrastructure node for use in an optical wireless communication network, the network including a plurality of infrastructure nodes arranged at intersections of a grid structure on a first surface and configured to provide access points of the network, and client devices on a second surface, the grid structure including a quadrilateral having an x-axis dimension equal to d1, a y-axis dimension equal to d2, and a diagonal dimension equal to d3, d2 being greater than or equal to d1, the infrastructure node comprising a downward optical wireless transducer configured to have a coverage area having at least two concentric segments, an infrastructure node, wherein the outermost segment of at least two concentrically arranged segments is dimensioned such that when the client device is positioned on a second surface parallel to the first surface and at a distance, the coverage area of the segment has a maximum diameter greater than 0.5*d3 on the second surface.

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