Optical wireless communication system, method for optical wireless communication, transmitter device and receiver device

Abstract

An optical wireless communication system including: a transmitter device having an array of Vertical-Cavity Surface-Emitting Lasers (VCSELs), wherein each VCSEL in the array is configured to emit a light beam in a different direction; and a receiver device having an array of Single Photon Avalanche Diodes (SPADs), wherein each SPAD in the array is configured to detect light from a different direction; a selective activation mechanism configured to activate a specific VCSEL and a specific SPAD based on their alignment to establish a communication link, without requiring physical alignment of the devices.

Description

[0001] OPTICAL WIRELESS COMMUNICATION SYSTEM, METHOD FOR OPTICAL WIRELESS COMMUNICATION, TRANSMITTER DEVICE AND RECEIVER DEVICE

[0002] TECHNICAL FIELD

[0003] The present disclosure generally pertains to an optical wireless communication system, a method for optical wireless communication, a transmitter device for optical wireless communication and a receiver device for optical wireless communication.

[0004] TECHNICAL BACKGROUND

[0005] Optical wireless communication (OWC), also named free space communication, is a method for transmitting data using light as a medium. It involves the use of lasers or light emitting diodes (LEDs) to transmit information through air or space, without the need for physical cables or wires. It can be used for short range communication within a room or building, as well as for long range communication between buildings or even across open space.

[0006] Due to the nature of light waves, OWC requires a clear line of sight between the transmitter and receiver. Obstacles such as buildings, trees, or atmospheric conditions can affect the signal quality and range.

[0007] OWC can achieve high data transfer rates, in the range of several gigabits per second (Gbps) or even higher. This makes it suitable for applications that require fast and reliable data transmission, such as high-definition video streaming, virtual reality (VR), and augmented reality (AR).

[0008] However, the physical alignment between transmitter and receiver may be cumbersome and may require manual or mechanical alignment of the devices.

[0009] Although there exist techniques for optical wireless communication, it is generally desirable to improve the existing techniques.

[0010] SUMMARY

[0011] According to a first aspect, the disclosure provides an optical wireless communication system comprising: a transmitter device having an array of Vertical-Cavity Surface-Emitting Lasers (VCSELs), wherein each VCSEL in the array is configured to emit a light beam in a different direction; and a receiver device having an array of Single Photon Avalanche Diodes (SPADs), wherein each SPAD in the array is configured to detect light from a different direction; a selective activation mechanism configured to activate a specific VCSEL and a specific SPAD based on their alignment to establish a communication link, without requiring physical alignment of the devices.

[0012] According to a second aspect, the disclosure provides a method for optical wireless communication comprising: emitting light from a specific VCSEL in an array of VCSELs, each configured to emit in a different direction; detecting the emitted light using a specific SPAD in an array of SPADs, each configured to detect light from a different direction; selectively activating the VCSEL and SPAD based on their alignment to establish a communication link without physical alignment.

[0013] According to a third aspect, the disclosure provides a transmitter device for optical wireless communication comprising: an array of VCSELs, each configured to emit a light beam in a different direction; a selective activation mechanism configured to activate a specific VCSEL based on its alignment with a receiver device to establish a communication link.

[0014] According to a fourth aspect, the disclosure provides a receiver device for optical wireless communication comprising: an array of SPADs, each configured to detect light from a different direction; a selective activation mechanism configured to activate a specific SPAD based on its alignment with a transmitter device to establish a communication link.

[0015] Further aspects are set forth in the dependent claims, the drawings and the following description.

[0016] BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Embodiments are explained by way of example with respect to the accompanying drawings, in which:

[0018] Fig. 1 schematically illustrates two embodiments of an optical wireless communication system illustrating a transmitter side;

[0019] Fig. 2 schematically illustrates two embodiments of an optical wireless communication system illustrating a receiver side;

[0020] Fig. 3 schematically illustrates an embodiment of a transmitter; Fig. 4 schematically illustrates an embodiment of a transmitter with selective activation;

[0021] Fig. 5 schematically illustrates an embodiment of a modulation scheme;

[0022] Fig. 6 schematically illustrates an embodiment of a receiver;

[0023] Fig. 7 schematically illustrates an embodiment of a receiver with selective activation;

[0024] Fig. 8 schematically illustrates an embodiment of an optical wireless communication system;

[0025] Fig. 9 schematically illustrates an embodiment of a transmitter device;

[0026] Fig. 10 schematically illustrates an embodiment of a receiver device;

[0027] Fig. 11 schematically illustrates an embodiment of an optical wireless communication system;

[0028] Fig. 12 schematically illustrates an embodiment of an optical wireless communication system; and

[0029] Fig. 13 schematically illustrates an embodiment of selective gating in a receiver device.

[0030] DETAILED DESCRIPTION OF EMBODIMENTS

[0031] Before a detailed description of the embodiments under reference of Fig. 3 is given, general explanations are made.

[0032] As mentioned in the outset, OWC is known and can achieve high data transfer rates.

[0033] There are various applications for OWC, among them:

[0034] 1) Indoor wireless networks: e.g. inside buildings, offices, shopping malls, where it could serve as alternative to WiFi or wired networks with increased security and privacy.

[0035] 2) Satellite Communication: OWC can be used for inter-satellite links, earth-space, and even intra-satellite communication.

[0036] 3) Defense and Aerospace: in these industries secure, high-bandwidth communication is required, where OWC could be a good fit.

[0037] Optical wireless communication offers several advantages over radio frequency (RF) communication. Here are the main advantages of optical wireless communication:

[0038] 4) High data transfer rates.

[0039] 5) High bandwidth - the light spectrum can utilize larger portion of the electromagnetic spectrum compared to RF communication. 6) Enhanced Security: OWC offers improved security compared to RF communication, since light waves do not penetrate walls or other obstacles, so it is difficult for unauthorized users to intercept or eavesdrop on the transmitted data.

[0040] 7) Immunity to Interference: OWC is less susceptible to interference from other electronic devices or electromagnetic signals compared to RF communication.

[0041] 8) Unlicensed Spectrum: OWC can operate in unlicensed spectrum bands, which means there are no regulatory restrictions or licensing requirements for its deployment. This allows for more flexibility and ease of implementation, especially in scenarios where obtaining RF spectrum licenses may be challenging or costly.

[0042] 9) Low Latency: OWC offers lower latency, as speed of light is the limiting factor.

[0043] On the contrary, OWC has some limitations, such as the requirement for a clear line-of-sight (LOS), susceptibility to atmospheric conditions and sensitivity to sun radiance which all may limit the range of OWC compared to RF communication.

[0044] Looking at the current RF communication technologies, there is a clear trend and motivation to continuously increase the achievable throughputs and network capacities in order to support the future applications, such as AR and VR. The ITU organization, throughout the IMT-2030 set it in his requirements from the next cellular technology - 6G. in parallel, the industry and academy is working on technologies utilizing higher frequency bands (e.g. THz communication). OWC could be a good fit (as a complementary solution) for the next generation wireless communication.

[0045] OWC primarily utilizes two different parts of the electromagnetic spectrum: the infrared (IR) spectrum and the visible light spectrum.

[0046] 1. In Infrared spectrum, OWC can operate in range between 800 nm (nanometers) to 1600 nm, where the longer wavelengths (1500-1600 nm) typically used for longer range, due to better immunity to atmospheric conditions.

[0047] 2. Visible Light Spectrum: from approximately 400 nm (violet) to 700 nm (red). OWC utilizing visible light is often referred to as Visible Light Communication (VLC) or Li-Fi (Light Fidelity).

[0048] As light source, OWC mainly utilize two type of sources:

[0049] 1. Light emitting diodes (LEDs): VLC communication usually uses this type of source. LEDs are semiconductor devices that emit light when an electric current passes through them. Modulation is performed by rapidly varying the intensity of the LED light, data can be encoded and transmitted wirelessly. This modulation can be achieved by directly controlling the current supplied to the LED. With this method, simple modulations (OOK, PAM) or even more complex ones (such as OFDM) can be generated

[0050] 2. Vertical-Cavity Surface-Emitting Lasers (VCSELs): VCSELs are a type of semiconductor laser diode that emits light vertically from the surface of the device. VCSELs have several advantages: a. They can operate at high speeds, enabling fast data transmission rates. b. They are power efficient solutions (compared to other laser diodes). c. Beam Characteristics: VCSELs emit a circular, symmetric beam with a narrow divergence angle. This makes them easier to couple with optical fibers or other optical components, simplifying the design and alignment of OWC systems. Moreover, the narrow beams allow to achieve very good link budget, much better than RF communication technologies. d. Scalability: VCSELs can be fabricated in arrays, allowing for parallel data transmission and increased capacity. e. In some embodiments, VCSELs are used as light source.

[0051] Photodiodes are the primary receiver elements used in OWC. They convert the received optical signal into an electrical signal that can be processed and decoded.

[0052] There are different types of photodiodes that can be used. Among them are:

[0053] 1. Avalanche Photodiodes (APDs): APDs are specialized photodiodes that provide higher sensitivity and gain compared to standard photodiodes. They operate in the avalanche breakdown region, which allows for internal amplification of the photocurrent.

[0054] 2. Single photon avalanche Diodes (SPADs) - SPADs have higher sensitivity compared to APDs for detecting individual photons. The principle of SPAD is based on avalanche breakdown in reverse-biased p-n junctions. When a photon is incident on the SPAD, it can generate an electron-hole pair within the depletion region of the diode. This triggers an avalanche multiplication effect, resulting in a detectable electrical current pulse. The electrical current pulse is usually sampled and if necessary, is counted. By detecting individual photons, SPADs can provide precise timing information and enable applications such as time-of-ffight measurements, fluorescence lifetime imaging, or quantum key distribution.

[0055] In some embodiments, SPADs are used as receiver elements. In terms of modulation, it can be distinguished between coherent modulation and non-coherent modulation.

[0056] 1. Coherent modulation in OWC involves the use of coherent detection, where the received optical signal is mixed with local oscillator to recover the transmitted data. This requires accurate carrier frequency and low phase noise receiver (and transmitter). The advantage of coherent modulation is high sensitivity and betterer immunity to interference compared to non-coherent modulation.

[0057] 2. Non-coherent modulation in OWC uses a photodetector to detect the energy of the signal, and loses the phase information. Examples for non-coherent modulation are: a. OOK (On off keying) - where the transmitter transmits a pulse (of photons) to represent ‘1’ and nothing to represent ‘0’ . b. PPM (Pulse position modulation) - where the position of the pulse in time represents the data to be transmitted (e.g. 4 different time positions represent 2 bits).

[0058] In some embodiments, OOK modulation is used.

[0059] As mentioned above, one of the main advantages of OWC is the ability to generate a very narrow optical beam. By having such a narrow beam, the link budget can be improved dramatically, as (large amount) of the energy is being received by the optical lens of the receiver. For the same form factor, a much better (narrower) beam compared to a beam generated by a regular RF -based antenna can be obtained.

[0060] That is simply due to physics - the optical wavelength is in order of nanometers, while in RF it is in order of millimeters or even worse.

[0061] Optical communication requires line-of-sight, meaning that the photons transmitted from the TX (transmitter device) will ‘hit’ the lens of the receiver. So, it is needed that that beam transmitted will ‘cover’ the RX (receiver device) lens.

[0062] This can be achieved this in two ways, as schematically illustrated in Fig. 1 which illustrates a transmission side of two embodiments of an optical wireless communication system:

[0063] 1. Having wide beam (using wide FoV (field-of-view) optics), as described in option 1. The optical wireless communication system la has a transmitter 2a (corresponding to or including a transmitter device TX) and a receiver 3a (corresponding to or including a receiver device RX). In this case, only small portion of the TX energy is collected by the RX lens which is translated to poor link budget. In other words, the main advantage of optics is lost as described above. 2. Having narrow beam (using narrow FoV optics or directly using the VCSEL as narrow laser source), as described in option 2. The optical wireless communication system lb has a transmitter 2b (corresponding to or including a transmitter device TX) and a receiver 3b (corresponding to or including a receiver device RX). In this case, large amount of energy is received by the RX, thus maintaining good link budget. However, a big challenge occurs - it is needed to manually / mechanically stir the TX so that the beam will cover the RX lens.

[0064] On RX side, similar concerns arise. The RX lens is needed to be able to collect light received from the TX.

[0065] This can be achieved in two ways, as schematically illustrated in Fig. 2 which illustrates a receiver side of the two embodiments of an optical wireless communication system la and lb of Fig. 1 :

[0066] 1. Having wide FoV RX lens. In this case, on top of collecting light from the TX, also light from the surroundings is collected, thus increasing level of interference (e.g. increase ambient light such as sun irradiance) and reducing the SNR.

[0067] 2. Having narrow FoV RX lens. This overcomes the high ambient light, but again, requires rotation or alignment of the lens so that they will cover the light source (VCSEL).

[0068] The alignment between the TX and RX may be cumbersome. It may require manual or mechanical alignment of the devices.

[0069] It has been recognized, as a basic idea of some embodiments, that an array of SPADs and array of VCSELs can be utilized, together with capability of selective activation of SPADs and VCSELs to allow efficient communication between the TX and RX devices, without the need for physical alignment (e.g. rotation) of the devices. That is, if the two devices are in the FoV of each other, then a communication between them could be established without the need to physically point them to each other and utilizing narrow beams in TX and RX.

[0070] Hence, some embodiments pertain to an optical wireless communication system including: a transmitter device having an array of transmitter elements, wherein each transmitter element in the array is configured to emit a light beam in a different direction; and a receiver device having an array of receiver elements, wherein each receiver element in the array is configured to detect light; a selective activation mechanism configured to activate one or more specific transmitter elements and one or more specific receiver elements based on their alignment to establish a communication link. Generally, for transmission, a transmitter element needs to cover one or more receiver elements, however, for beam management purposes, also adjacent transmitter elements may be activated (in addition to the selected one). Thus, in a case of movement of the transmitter device (e.g., rotation of the camera), there may be minimal interruption in the communication.

[0071] Accordingly, one or more transmitter elements may be selected to be activated, however, typically in some embodiments only one transmitter element may be activated.

[0072] On the transmitter side, usually only one transmitter element (e.g., VCSEL) is activated, because the transmitted cone usually covers the whole lens of the receiver device (if the transmitter device and the receiver device are far enough away). But, as explained before, also adjacent transmitter elements may be activated as to keep the link active also if the transmitter device and / or the receiver device are moving.

[0073] For reception, typically, in some embodiments, more than one receiver element (e g., macro pixel) may be activated to increase the dynamic range such that for every transmitted symbol, more than one count (one zero or one) is obtained.

[0074] Depending on the optical system of the receiver device, the emitted light beam of the one activated transmitter element is imaged onto one or more receiver elements.

[0075] For example, when the array of receiver elements is in the focus, then one specific receiver element may detect the emitted light beam from the selected one transmitter element.

[0076] So, an optical system in the receiver device directs the received photons from the transmitter element, which may be far away, to only one receiver element (e.g., SPAD) of the receiver device. That is, the transmitter element is seen as an infinite dot on the receiver side (assuming perfect optics on the receiver side).

[0077] However, it may be good for the dynamic range to activate more than one receiver element such that the receiver optics may be configured sub-optimal to increase the circle of confusion or to take the array of receiver elements out of focus. Thus, the wave arriving from the transmitter side will not be mapped to only one receiver element (e g., SPAD) but to a group of receiver elements which are adjacent receiver elements. So, from the receiver side each receiver element sees a slightly different direction, but there may be a larger overlap between them (actually each pixel (receiver element) does not see exactly one angle, but a ‘cone’ in space).

[0078] Accordingly, one or more receiver elements may be activated depending on the current configuration or the desired configuration. Generally, one or more receiver elements are associated with one transmitter element such that only these (one or more receiver elements) detect light emitted from the associated one transmitter element.

[0079] In some embodiments, the transmitter elements are Vertical Cavity Surface Emitting lasers (VCSELs).

[0080] In some embodiments, the receiver elements are Single Photon Avalanche Diodes (SPADs).

[0081] In some embodiments, the transmitter device and the receiver device are in the field-of-view of each other such that no further physical alignment of the transmitter device and / or receiver device is required, wherein the physical alignment includes manual or mechanical alignment.

[0082] In some embodiments, the transmitter device is further configured to modulate each light beam emitted by the one or more selected transmitter elements using On-Off Keying (OOK) modulation or Pulse Position Modulation (PPM).

[0083] In some embodiments, the receiver device further comprises a demodulation unit and a forward error correction unit, wherein each receiver element is configured to convert detected photons into events, wherein the demodulation unit is configured to convert events into encoded bits or soft bits(e.g., log likelihood ratios) and the forward error correction unit is configured to convert the encoded bits or soft bits into data bits (decoded bits).

[0084] As mentioned above, the transmitter device may be configured to modulate each light beam emitted by the one or more selected transmitter elements using OOK or PPM modulation, for example, and, thus, in some embodiments, the transmitter device further comprises a modulation unit configured to generate data symbols for transmission, and a beam selection unit configured to control which one or more transmitter elements in the array are activated based on the alignment with the receiver device.

[0085] In some embodiments, the receiver device further comprises a beam selection unit configured to control which one or more receiver elements in the array are activated based on the direction of the incoming light beam from the transmitter device.

[0086] In some embodiments, the transmitter device is configured to selectively activate the one or more transmitter elements based on data from an external sensor.

[0087] In some embodiments, the external sensor is an image sensor or an Inertial Measurement Unit.

[0088] In some embodiments, the receiver device is configured to selectively activate the one or more receiver elements based on the detected photon events corresponding to the transmitted light beam received by the receiver device. In some embodiments, the communication link is a non line-of-sight communication link such that each emitted light beam from the transmitter device is reflected at an object before the emitted light beam is received by the receiver device to establish the communication link.

[0089] In some embodiments, the selective activation mechanism is configured to activate one or more second specific transmitter elements and one or more second specific receiver elements based on their alignment to establish a second communication link.

[0090] Generally, the selective activation mechanism may further be configured to activate one or more third, fourth, fifth, etc. specific transmitter elements and one or more second, third, fourth, fifth, etc. specific receiver elements based on their alignment to establish a third, fourth, fifth, etc. communication link, respectively.

[0091] In some embodiments, the second communication link is a non line-of-sight communication link such that each emitted light beam from the transmitter device is reflected at an object before the emitted light beam is received by the receiver device to establish the second communication link.

[0092] In some embodiments, the transmitter device is configured to activate one or more second specific transmitter elements to perform a time-of-flight measurement.

[0093] In some embodiments, the receiver device is configured to activate one or more second specific receiver elements to perform a time-of-flight measurement.

[0094] In some embodiments, the receiver device is configured to activate one or more second specific receiver elements to perform image capturing.

[0095] In some embodiments, the time-of-flight measurement or the image capturing is performed in serial or parallel to communication via the established communication link, wherein the time-of- flight measurement is a direct time-of-flight measurement or an indirect time-of-flight measurement.

[0096] In embodiments in which the time-of-flight measurement is a direct time-of-flight measurement, the receiver elements may be SPADs. In embodiments in which the time-of-flight measurement is an indirect time-of-flight measurement, the receiver elements may be current-assisted photonic demodulators (CAPDs). In embodiments in which the time-of-flight measurement is an indirect time-of-flight measurement, the data is carried as phase. The phase encoding may also be implemented by (a sort of PPM), where the pulse position corresponds to a different phase that can be resolved by the CAPD pixel(s).

[0097] In some embodiments, the system further includes a second receiver device having an array of receiver elements, wherein each receiver element in the array is configured to detect light from a different direction, and wherein the selective activation mechanism is configured to activate one or more second specific transmitter elements in the transmitter device and one or more second specific receiver elements in the second receiver device based on their alignment to establish a second communication link.

[0098] In some embodiments, at least one communication link (the communication link or the second communication link or both) is a non line-of-sight communication link such that each emitted light beam from the transmitter device is reflected at an object before the emitted light beam is received by the respective receiver device to establish the respective communication link.

[0099] In some embodiments, the receiver elements of the second receiver device are Single Photon Avalanche Diodes (SPADs).

[0100] In some embodiments, the system includes: a first communication device including a first transmitter device and a first receiver device, the first transmitter device including a first array of transmitter elements, each configured to emit a light beam in a different direction, the first receiver device including a first array of receiver elements, each configured to detect light; a second communication device including a second transmitter device and a second receiver device, the second transmitter device including a second array of transmitter elements, each configured to emit a light beam in a different direction, the second receiver device including a second array of receiver elements, each configured to detect light; a third communication device including a third transmitter device and a third receiver device, the third transmitter device including a third array of transmitter elements, each configured to emit a light beam in a different direction, the third receiver device including a third array of receiver elements, each configured to detect light; wherein the selective activation mechanism is configured to: activate one or more first specific transmitter elements in the first transmitter device and one or more first specific receiver elements in the second receiver device based on their alignment to establish a first communication link; activate one or more second specific transmitter elements in the first transmitter device and one or more second specific receiver elements in the third receiver device based on their alignment to establish a second communication link; activate one or more third specific transmitter elements in the second transmitter device and one or more third specific receiver elements in the first receiver device based on their alignment to establish a third communication link; activate one or more fourth specific transmitter elements in the second transmitter device and one or more fourth specific receiver elements in the third receiver device based on their alignment to establish a fourth communication link; activate one or more fifth specific transmitter elements in the third transmitter device and one or more fifth specific receiver elements in the first receiver device based on their alignment to establish a fifth communication link; and activate one or more sixth specific transmitter elements in the third transmitter device and one or more sixth specific receiver elements in the second receiver device based on their alignment to establish a sixth communication link.

[0101] The communication device may be, for example, a mobile electronic device such as a smartphone.

[0102] In some embodiments, the transmitter device is configured to modulate each light beam emitted by the one or more selected transmitter elements to transmit data symbols with a preset symbol rate, each data symbol has a preset symbol duration, and wherein the receiver device is configured to selectively activate at least two groups of receiver elements in the array based on the alignment with the transmitter device and to activate the at least two groups of receiver elements in accordance with a gating mechanism, wherein the gating mechanism includes repeatedly activating each group of the at least two groups at a different time, wherein each group is activated for a preset time corresponding to the symbol duration, and wherein only one group is activated at a time.

[0103] In some embodiments, each light beam is modulated using On-Off Keying (OOK) modulation.

[0104] In some embodiments, the receiver elements are Single Photon Avalanche Diodes (SPADs), and wherein the symbol duration time is shorter than the deadtime of the SPADs in the array.

[0105] Some embodiments pertain to a transmitter device for optical wireless communication including: an array of transmitter elements, each configured to emit a light beam in a different direction; a selective activation mechanism configured to activate one or more specific transmitter elements based on its alignment with a receiver device to establish a communication link.

[0106] In some embodiments, the transmitter device includes a modulation unit configured to modulate each light beam emitted by the one or more selected transmitter elements using On-Off Keying (OOK) modulation or Pulse Position Modulation (PPM).

[0107] Some embodiments pertain to a receiver device for optical wireless communication including: an array of receiver elements, each configured to detect light; a selective activation mechanism configured to activate one or more specific receiver elements based on its alignment with a transmitter device to establish a communication link.

[0108] In some embodiments, the receiver device further includes a demodulation unit and a forward error correction unit, wherein each receiver element is configured to convert detected photons into events, wherein the demodulation unit is configured to convert events into encoded bits and the forward error correction unit is configured to convert the encoded bits into data bits (decoded bits).

[0109] In some embodiments, the selective activation mechanism is configured to control which one or more receiver elements in the array is activated based on the direction of the incoming light beam from the transmitter device.

[0110] Returning to Fig. 3, on TX side:

[0111] Fig. 3 schematically illustrates an embodiment of a transmitter 20 (corresponding to or including a transmitter device TX) which includes an array of VCSELs 21.

[0112] The array of VCSELs 21 is used. This array of VCSELs 21, creates a scenario in which each VCSEL is directing to different point in space. This is already being used in solid-state LIDAR systems today.

[0113] Fig. 4 schematically illustrates the embodiment of the transmitter 20 of Fig. 3 which includes the array of VCSELs 21 with selective activation.

[0114] Selective activation - Out of all the VCSELs in the array 21, it is needed to activate only one VCSEL - the VCSEL which is pointing to the direction which covers the RX lens of the receiver 30 (corresponding to or including a receiver device RX).

[0115] Fig. 5 schematically illustrates an embodiment of a modulation scheme.

[0116] Modulation - a simple modulation scheme such as OOK can be used That is, to transmit ‘ 1’, a pulse with certain width (e.g. for 100MHz, the pulse width will be 10 nsec (nanoseconds)) is transmitted, and to transmit ‘O’, nothing is transmitted.

[0117] On RX side:

[0118] Fig. 6 schematically illustrates an embodiment of a receiver (corresponding to or including a receiver device RX) which includes an array of SPADs 31.

[0119] The array of SPADs 31 is used. Each SPAD (or group of SPADs - Macro pixel) is ‘looking’ to a different point in space. This is due to basic optics, as depicted in Fig. 6. Note - the use of group of SPADs (e.g. a Macro pixel or more) or single SPAD depends on the optics design and system requirements.

[0120] Fig. 7 schematically illustrates an embodiment of a receiver 30 (corresponding to or including a receiver device RX) which includes the array of SPADs 31 with selective activation.

[0121] Selective activation - in regular SPAD array (for imaging), or in ToF system, a group of SPADs (full array, line-by-line, ... ) is being activated. That is, data is being received from many SPADs which do not collect light from the light source. That is very inefficient. With selective activation of SPADs (or small group of SPADs), it is ensured that photons will be received from the light source position by the selected (activated) SPADs, and all rest of SPADs pointing to different directions could be deactivated, thus saving power and processing resources on RX side.

[0122] Demodulation - the demodulation of bits can be performed similar to operation of a dToF (direct time-of-flight) system. Once a photon is being detected, the SPAD sensor generates an event.

[0123] The events can be sampled at the baud rate of the communication system, and converted easily to bits - if photon is detected within the symbol time - an event is generated which represent the bit ‘ I’, otherwise, if no photon is detected, no event is generated and bit ‘0’ is assumed for that symbol time. A more advanced scheme will involve a group of SPADs in some embodiments. During symbol time, multiple events are captured (by several SPADs). A counter is used to count how many events have been received in this symbol time. The count value is compared against a threshold (if number of events > threshold, then the bit is ‘ 1’, otherwise ‘0’).

[0124] In the above we described simplex operation - where one device only transmits, and the other device is in RX. In practice, both devices have TX and RX elements, thus allowing to generate duplex communication, as schematically illustrated in Fig. 8.

[0125] Fig. 9 schematically illustrates an embodiment of a transmitter device 40.

[0126] TX system:

[0127] The block diagram of Fig. 9 shows one example for TX flow.

[0128] Data bits are generated by the host and fed into the modem.

[0129] The data path operation is similar to other modems implementation in RF communications:

[0130] MAC protocol layer, and

[0131] PHY layer - adding preamble, pilots, CRC (cyclic redundancy check), FEC (Forward Error Correction block), adding CRC, Modulation (generating symbols for OOK, PPM). These symbols are being transmitted to the LDD (Laser Diode Driver), which modulates them using electrical signal which later are being fed into VCSEL which transmits the light pulses carrying photons.

[0132] In addition, it is needed to select the desired VCSEL to transmit the modulated signal. This is done by the beam selection mechanism, which can use information from the RX SPAD sensor or another sensor (to be described later).

[0133] Note that other implementations may also hold.

[0134] Fig. 10 schematically illustrates an embodiment of a receiver device 50.

[0135] RX system:

[0136] RX part is described in the block diagram of Fig. 10.

[0137] It is assumed that out of the SPAD array, only a group of SPADs in being active. Selection of the SPADs is done by algorithm in the SPADs / MPs selection (RX beam selection), to be described later.

[0138] The output of the SPADs is a stream of events. They are fed into demodulator, which converts them into a stream of symbols. In case of OOK, this could be stream of bits. In case a more advanced demodulator is used, these events are converted into soft symbols or LLRs (loglikelihood ratios).

[0139] Later it is feed them into FEC, which decodes the data.

[0140] Last, we have the MAC block which decodes and strips the MAC headers, checks also CRC and generates packets.

[0141] Synchronization block is responsible for recovering (and adjusting) the clock frequency, symbol and frame timing etc. It can use the preamble / pilots transmitted by the TX side or use also data- driven algorithms.

[0142] Rx / Tx Beam selection and tracking in the transmitter device 40 of Fig. 9 and the receiver device 50 of Fig. 10:

[0143] Rx / Tx beam selection is the block responsible for selecting the relevant SPADs and VCSELs (respectively) that will be used for communication. This block is used during acquisition phase, when the link is being established, and also during active time, to continuously monitor and track the beams and change if needed.

[0144] The block can use as an input one of the following (or both): Events received from SPADs. For instance, at acquisition time, events are collected from all SPADs of the array. Once a stream of events corresponding to a synchronization signal is being detected in a (group) of SPADs, only them are used for communication and all the rest is deactivated. Other option is using photon counting (PC) statistics to estimate which of the SPADs (and VCSELs) should be activated.

[0145] Data received from another external image sensor - in mobile phone there are multiple cameras. Another camera can be utilized to detect the other device (using any of vision sensing techniques) and following that command the beam selection algorithm which SPADs and which VCSELs on TX side should be activated.

[0146] Moreover, transmitter and receiver may use an acceleration sensor, e.g. an IMU (Inertial Measurement Unit), to detect and track the movement and pose of the transmitter device and the receiver device, respectively, and the selection of VCSELs and SPADs can be adapted based on the detected and tracked movement and pose of the respective device.

[0147] For mobile systems, there is also a need to continuously track the other device position, and if needed change the beam (= select a different VCSEL / SPAD). This could again be based on sensing events received in adjacent SPADs to the active ones, or using external sensor or both.

[0148] Additional comments regarding modem operation:

[0149] 1. To address impairments in SPAD operation (such as jitter, dead time, after pulse), and mitigate ambient light interference (sun radiance), one may utilize a more advanced receiver which utilizes group of SPADs to demodulate the incoming events.

[0150] 2. In case of PPM (pulse position modulation), the demodulator will utilize timing information of events. Such data can be generated by similar block to TDC (time to digital conversion) in dToF system.

[0151] Fig. 11 schematically illustrates an embodiment of an optical wireless communication system.

[0152] Mesh communication:

[0153] As very small narrow beams are created in free space, one can generate multiple links from same device. Consider the following examples, where there are multiple devices in the same room. As can be seen in the Fig. 11, each link activates one VCSEL in the TX device and a (group of) SPADs / MP (Macro pixel) in the receiver. Since the array of the Tx / Rx has many more VCSELs and SPADs (pointing to different directions), many links can be generated like this. Same goes for Hub / GW communication. One GW (e.g. installed on the ceiling) can be used, which can generate multiple links to multiple devices, without creating any interference between them. In such case, very high capacity can be achieved.

[0154] Returning to the general explanations:

[0155] Integration with dToF / Camera sensor:

[0156] In a device which already holds VCSEL and / or SPAD array sensor (e.g. as part dToF system), one can integrate the OWC concept into this system. The advantage is cost and size reduction, as full utilization of existing components (including lens, etc.) can be achieved.

[0157] Consider dToF system, for example, dToF systems like this are already integrated in some mobile devices. Every dToF system includes VCSEL array and SPAD array.

[0158] On TX side, the VCSEL array which is used for transmitting light pulses for measuring distance, can be used also for communication. One of the VCSELs which is directed to the RX device will be used for communication (and can also be used for distance measurement), while all other VCSELs will be used for distance measurement.

[0159] On RX side, the relevant (group) of SPADs will be used for OWC, while all the rest will be used for distance measurement as part of dToF system operation.

[0160] The operation can be done in parallel or serially, achieving simultaneous sensing and communicating using the same system.

[0161] Moreover, in case of SPAD sensor used for imaging / sensing, OWC can be combined together with regular SPAD image sensor. That is, the sensor could utilize the specific SPAD(s) for OWC, while using all the rest for image capturing (again, in parallel or serial operation).

[0162] Returning to Fig. 12, there is schematically illustrated an embodiment of an optical wireless communication system.

[0163] Non line-of-sight operation:

[0164] Above LOS operation between devices has been discussed, however, the same concept will hold also for non line-of-sight (NLOS). That is, a modulated light beam directed to an object in the scene will be reflected back (with characteristics related to object material and orientation) and will be received by a (group) of SPADs on the receiver side.

[0165] Moreover, with NLOS communication, it is easy to generate multiple links between the same two devices, as can be seen in the Fig. 12. This method shows an easy way to increase the throughput between the two devices. A spatial separation between the links is used to pass different stream of data on each one of them.

[0166] Returning to the general explanations:

[0167] Broadcast communication:

[0168] Broadcast of data from one device to multiple devices can be performed. That can be done by activating multiple (or all) VCSELs at the transmitter side, each one of them carrying same information. On the receiver side, to mitigate interference noise, the receiver will activate only the relevant SPAD(s) which receive light from the receiver. While this is non power efficient method for the transmitter side, it allows him to transmit data to all its peers without knowing where they are.

[0169] Applications:

[0170] While above examples were demonstrating communication between mobile phones, OWC based on this concept can be used in various applications including gaming, AR / VR, loT, Space, automotive, Retail, data center (communication between servers) and smart cities.

[0171] Returning to Fig. 13, there is schematically illustrated an embodiment of selective gating in a receiver device.

[0172] It has been recognized that the data rate or symbol rate is limited due to the deadtime of the SPADs during which the respective SPAD cannot be triggered by a photon to generate an event. Thus, the respective SPAD is blind in this time and any faster modulations of the transmitted signal cannot be resolved.

[0173] However, it has been recognized that the selected SPADs can be summarized into different groups, wherein a group includes one or more SPADs. Each group of SPADs is activated at a different time (“gating”) and only one group is activated at a time, i.e. when one group is not active anymore, a different group is then getting active.

[0174] In this way, the deadtime of one group does not influence the measurement of the subsequently activated group. Once a group has recovered from the deadtime, it can be activated again. Thereby, the data rate or symbol rate of the transmitted signal can be increased, since a faster modulation, which occurs during the deadtime of a first group of SPADs, is detected by a second group activated subsequent of the first group. Then, the first group is activated again and so on.

[0175] In other words, the transmitter device is configured to modulate the light beam emitted by the selected VCSEL to transmit data symbols with a preset symbol rate, each data symbol has a preset symbol duration. The receiver device is configured to selectively activate at least two groups of SPADs in the array based on the alignment with the transmitter device and to activate the at least two groups of SPADs in accordance with a gating mechanism. The gating mechanism includes repeatedly activating each group of the at least two groups at a different time, wherein each group is activated for a preset time corresponding to the symbol duration, and wherein only one group is activated at a time, in particular, wherein the symbol duration is shorter than the deadtime of the SPADs in the array, and, in particular, wherein the light beam is modulated using On-Off Keying (OOK) modulation.

[0176] The Fig. 13 depicts a SPAD array in a receive device in which four groups of SPADs are selected for activation based on the alignment with the transmitter device.

[0177] As shown in the upper right part of Fig. 13, the TX profile (transmission signal) utilizes OOK modulation with a symbol duration time (equal to the bit rate / data rate in OOK modulation) of one nanosecond.

[0178] The deadtime of a SPAD is three nanoseconds such that the symbol rate could not be resolved when all groups of SPADs are activated at the same time.

[0179] Hence, each group is activated at a different time for a duration (preset time) corresponding to the symbol duration.

[0180] As depicted in Fig. 13, according to the RX gating profile (gating mechanism), the first group of SPADs is activated to detect the first symbol (data symbol), then the second group of SPADs is activated to detect the second symbol, then the third group of SPADs is activated to detect the third symbol, and then the fourth group of SPADs is activated to detect the fourth symbol. This process is repeated continuously. Hence, after activating the fourth group of SPADs, the first group of SPADs is activated again to detect the fifth symbol and so on.

[0181] Thereby, the symbol rate (or data transfer rate) can be increased, since the deadtime effect can be overcome and the symbol duration can be shorter than the deadtime.

[0182] It should be recognized that the embodiments describe methods with an exemplary ordering of method steps. The specific ordering of method steps is however given for illustrative purposes only and should not be construed as binding.

[0183] All units and entities described in this specification and claimed in the appended claims can, if not stated otherwise, be implemented as integrated circuit logic, for example on a chip, and functionality provided by such units and entities can, if not stated otherwise, be implemented by software. In so far as the embodiments of the disclosure described above are implemented, at least in part, using software-controlled data processing apparatus, it will be appreciated that a computer program providing such software control and a transmission, storage or other medium by which such a computer program is provided are envisaged as aspects of the present disclosure.

[0184] Note that the present technology can also be configured as described below.

[0185] (1) An optical wireless communication system including: a transmitter device having an array of transmitter elements, wherein each transmitter element in the array is configured to emit a light beam in a different direction; and a receiver device having an array of receiver elements, wherein each receiver element in the array is configured to detect light; a selective activation mechanism configured to activate one or more specific transmitter elements and one or more specific receiver elements based on their alignment to establish a communication link.

[0186] (2) The system of (1), wherein the transmitter elements are Vertical Cavity Surface Emitting lasers (VCSELs).

[0187] (3) The system of (1) or (2), wherein the receiver elements are Single Photon Avalanche Diodes (SPADs).

[0188] (4) The system of any one of (1) to (3), wherein the transmitter device and the receiver device are in the field-of-view of each other such that no further physical alignment of the transmitter device and / or receiver device is required, wherein the physical alignment includes manual or mechanical alignment.

[0189] (5) The system of any one of (1) to (4), wherein the transmitter device is further configured to modulate each light beam emitted by the one or more selected transmitter elements using On- Off Keying (OOK) modulation or Pulse Position Modulation (PPM).

[0190] (6) The system of any one of (1) to (5), wherein the receiver device further comprises a demodulation unit and a forward error correction unit, wherein each receiver element is configured to convert detected photons into events, wherein the demodulation unit is configured to convert events into encoded bits or soft bits (e.g., log likelihood ratios) and the forward error correction unit is configured to convert the encoded bits or soft bits into data bits (decoded bits).

[0191] (7) The system of any one of (1) to (6), wherein the transmitter device further comprises a modulation unit configured to generate data symbols for transmission, and a beam selection unit configured to control which one or more transmitter elements in the array are activated based on the alignment with the receiver device.

[0192] (8) The system of any one of (1) to (7), wherein the receiver device further comprises a beam selection unit configured to control which one or more receiver elements in the array are activated based on the direction of the incoming light beam from the transmitter device.

[0193] (9) The system of any one of (1) to (8), wherein the transmitter device is configured to selectively activate the one or more transmitter elements based on data from an external sensor.

[0194] (10) The system of (9), wherein the external sensor is an image sensor or an Inertial Measurement Unit.

[0195] (11) The system of any one of (1) to (10), wherein the receiver device is configured to selectively activate the one or more receiver elements based on the detected photon events corresponding to the transmitted light beam received by the receiver device.

[0196] (12) The system of any one of (1) to (11), wherein the communication link is a non line-of- sight communication link such that each emitted light beam from the transmitter device is reflected at an object before the emitted light beam is received by the receiver device to establish the communication link.

[0197] (13) The system of any one of (1) to (12), wherein the selective activation mechanism is configured to activate one or more second specific transmitter elements and one or more second specific receiver elements based on their alignment to establish a second communication link.

[0198] (14) The system of (13), wherein the second communication link is a non line-of-sight communication link such that each emitted light beam from the transmitter device is reflected at an object before the emitted light beam is received by the receiver device to establish the second communication link.

[0199] (15) The system of any one of (1) to (14), wherein the transmitter device is configured to activate one or more second specific transmitter elements to perform a time-of-flight measurement.

[0200] (16) The system of any one of (1) to (15), wherein the receiver device is configured to activate one or more second specific receiver elements to perform a time-of-flight measurement.

[0201] (17) The system of any one of (1) to (16), wherein the receiver device is configured to activate one or more second specific receiver elements to perform image capturing. (18) The system of any one of (15) to (17), wherein the time-of-flight measurement or the image capturing is performed in serial or parallel to communication via the established communication link, wherein the time-of-flight measurement is a direct time-of-flight measurement or an indirect time-of-flight measurement.

[0202] (19) The system of any one of (1) to (18), wherein the system further includes a second receiver device having an array of receiver elements, wherein each receiver element in the array is configured to detect light from a different direction, and wherein the selective activation mechanism is configured to activate one or more second specific transmitter elements in the transmitter device and one or more second specific receiver elements in the second receiver device based on their alignment to establish a second communication link.

[0203] (20) The system of (19), wherein at least one communication link is a non line-of-sight communication link such that each emitted light beam from the transmitter device is reflected at an object before the emitted light beam is received by the respective receiver device to establish the respective communication link.

[0204] (21) The system of (19) or (20), wherein the receiver elements of the second receiver device are Single Photon Avalanche Diodes (SPADs).

[0205] (22) The system of any one of (1) to (21), wherein the transmitter device is configured to modulate each light beam emitted by the one or more selected transmitter elements to transmit data symbols with a preset symbol rate, each data symbol has a preset symbol duration, and wherein the receiver device is configured to selectively activate at least two groups of receiver elements in the array based on the alignment with the transmitter device and to activate the at least two groups of receiver elements in accordance with a gating mechanism, wherein the gating mechanism includes repeatedly activating each group of the at least two groups at a different time, wherein each group is activated for a preset time corresponding to the symbol duration, and wherein only one group is activated at a time.

[0206] (23) The system of (22), wherein each light beam is modulated using On-Off Keying (OOK) modulation.

[0207] (24) The system of (22) or (23), wherein the receiver elements are Single Photon Avalanche Diodes (SPADs), and wherein the symbol duration time is shorter than the deadtime of the SPADs in the array.

[0208] (25) A method for optical wireless communication including: emitting light from one or more specific transmitter elements in an array of transmitter elements, each configured to emit a light beam in a different direction; detecting the emitted light using one or more specific receiver elements in an array of receiver elements, each configured to detect light; selectively activating the one or more transmitter elements and the one or more receiver elements based on their alignment to establish a communication link.

[0209] (26) The method of (25), wherein the transmitter elements are Vertical Cavity Surface Emitting lasers (VCSELs).

[0210] (27) The method of (25) or (26), wherein the receiver elements are Single Photon Avalanche Diodes (SPADs).

[0211] (28) The method of any one of (25) to (27), wherein the array of transmitter elements and the array of receiver elements are in the field-of-view of each other such that no further physical alignment of the array of transmitter elements and / or the array of receiver elements is required, wherein the physical alignment includes manual or mechanical alignment.

[0212] (29) The method of any one of (25) to (28), further including modulating the emitted light using On-Off Keying (OOK) modulation or Pulse Position Modulation (PPM) to represent data bits.

[0213] (30). The method of any one of (25) to (29), further including demodulating the detected photons into events, converting the events into encoded bits or soft bits (e.g., log likelihood ratios) and converting the encoded bits or soft bits into data bits (decoded bits) at a receiver device including the array of receiver elements

[0214] (31) The method of any one of (25) to (30), further including the steps of: generating data symbols at a transmitter device including the array of transmitter elements; controlling which one or more transmitter elements in the array are activated based on alignment with the receiver device.

[0215] (32) The method of any one of (25) to (31), further including the steps of: controlling which one or more receiver elements in the array are activated based on the direction of the incoming light beam from the transmitter device.

[0216] (33) The method of any one of (25) to (32), further including selectively activating the one or more transmitter elements based on data from an external sensor. (34) The method of (33), wherein the external sensor is an image sensor or an Inertial Measurement Unit.

[0217] (35) The method of any one of (25) to (34), further including selectively activating the one or more receiver elements based on detected photon events corresponding to the transmitted light beam received by the receiver device.

[0218] (36) The method of any one of (25) to (35), wherein the communication link is a non line-of- sight communication link such that each emitted light beam from the transmitter device is reflected at an object before the emitted light beam is received by the receiver device to establish the communication link.

[0219] (37) The method of any one of (25) to (36), wherein the method further includes activating one or more second specific transmitter elements and one or more second specific receiver elements based on their alignment to establish a second communication link.

[0220] (38) The method of (37), wherein the second communication link is a non line-of-sight communication link such that each emitted light beam from the transmitter device is reflected at an object before the emitted light beam is received by the receiver device to establish the second communication link.

[0221] (39) The method of any one of (25) to (38), wherein the method further includes activating one or more second specific transmitter elements to perform a time-of-flight measurement.

[0222] (40) The method of any one of (25) to (39), wherein the method further includes activating one or more second specific receiver elements to perform a time-of-flight measurement.

[0223] (41) The method of any one of (25) to (40), wherein the method further includes activating one or more second specific receiver elements to perform image capturing.

[0224] (42) The method of any one of (39) to (41), wherein the time-of-flight measurement or the image capturing is performed in serial or parallel to communication via the established communication link, wherein the time-of-flight measurement is a direct time-of-flight measurement or an indirect time-of-flight measurement.

[0225] (42) The method of any one of (25) to (41), wherein the method further includes selectively activating one or more second specific transmitter elements in the array of transmitter elements and one or more second specific receiver elements in a second array of receiver elements different from the array of receiver elements based on their alignment to establish a second communication link. (43) The method of (42), wherein at least one communication link is a non line-of-sight communication link such that each emitted light beam from the transmitter device is reflected at an object before the emitted light beam is received by the respective array of receiver elements to establish the respective communication link.

[0226] (44) The method of (42) or (43), wherein the receiver elements of the second array of receiver elements are Single Photon Avalanche Diodes (SPADs).

[0227] (45) The method of any one of (25) to (44), wherein the method further includes modulating each light beam emitted by the one or more selected transmitter elements to transmit data symbols with a preset symbol rate, each data symbol has a preset symbol duration, and selectively activating at least two groups of receiver elements in the array of receiver elements based on the alignment with the array of transmitter elements and activating the at least two groups of receiver elements in accordance with a gating mechanism, wherein the gating mechanism includes repeatedly activating each group of the at least two groups at a different time, wherein each group is activated for a preset time corresponding to the symbol duration, and wherein only one group is activated at a time.

[0228] (46) The method of (45), wherein each light beam is modulated using On-Off Keying (OOK) modulation.

[0229] (47) The method of (45) or (46), wherein receiver elements are Single Photon Avalanche Diodes (SPADs), and wherein the symbol duration is shorter than the deadtime of the SPADs in the array.

[0230] (48) A transmitter device for optical wireless communication including: an array of transmitter elements, each configured to emit a light beam in a different direction; a selective activation mechanism configured to activate one or more specific transmitter elements based on its alignment with a receiver device to establish a communication link.

[0231] (49) The transmitter device of (48), further including a modulation unit configured to modulate each light beam emitted by the one or more selected transmitter elements using On-Off Keying (OOK) modulation or Pulse Position Modulation (PPM).

[0232] (50) A receiver device for optical wireless communication including: an array of receiver elements, each configured to detect light; a selective activation mechanism configured to activate one or more specific receiver elements based on its alignment with a transmitter device to establish a communication link. (51) The receiver device of (50), further including a demodulation unit and a forward error correction unit, wherein each receiver element is configured to convert detected photons into events, wherein the demodulation unit is configured to convert events into encoded bits and the forward error correction unit is configured to convert the encoded bits into data bits (decoded bits).

[0233] (52) The receiver device of (50) or (51), wherein the selective activation mechanism is configured to control which one or more receiver elements in the array is activated based on the direction of the incoming light beam from the transmitter device.

Claims

CLAIMS1. An optical wireless communication system comprising: a transmitter device having an array of Vertical-Cavity Surface-Emitting Lasers (VCSELs), wherein each VCSEL in the array is configured to emit a light beam in a different direction; and a receiver device having an array of Single Photon Avalanche Diodes (SPADs), wherein each SPAD in the array is configured to detect light from a different direction; a selective activation mechanism configured to activate a specific VCSEL and a specific SPAD based on their alignment to establish a communication link, without requiring physical alignment of the devices.

2. The system of claim 1, wherein the selective activation mechanism is further configured to modulate the light beam emitted by the selected VCSEL using On-Off Keying (OOK) modulation.

3. The system of claim 1, wherein the receiver device further comprises a demodulation unit configured to convert detected photons into electrical signals representing data bits.

4. The system of claim 1, wherein the transmitter device further comprises a modulation unit configured to generate data symbols for transmission, and a beam selection unit configured to control which VCSEL in the array is activated based on the alignment with the receiver device.

5. The system of claim 1, wherein the receiver device further comprises a beam selection unit configured to control which SPAD in the array is activated based on the direction of the incoming light beam from the transmitter device.

6. The system of claim 1, wherein the transmitter device is configured to selectively activate the VCSELs based on feedback from the receiver device.

7. The system of claim 1, wherein the receiver device is configured to selectively activate the SPADs based on the detected photon events corresponding to the transmitted light beam.

8. A method for optical wireless communication comprising: emitting light from a specific VCSEL in an array of VCSELs, each configured to emit in a different direction; detecting the emitted light using a specific SPAD in an array of SPADs, each configured to detect light from a different direction;selectively activating the VCSEL and SPAD based on their alignment to establish a communication link without physical alignment.

9. The method of claim 8, further comprising modulating the emitted light using On-Off Keying (OOK) modulation to represent data bits.

10. The method of claim 8, further comprising demodulating the detected photons into electrical signals representing data bits at the receiver device.

11. The method of claim 8, further comprising the steps of: generating data symbols at the transmitter device; controlling which VCSEL in the array is activated based on alignment with the receiver device.

12. The method of claim 8, further comprising the steps of: controlling which SPAD in the array is activated based on the direction of the incoming light beam from the transmitter device.

13. The method of claim 8, further comprising selectively activating the VCSELs based on feedback from the receiver device.

14. The method of claim 8, further comprising selectively activating the SPADs based on detected photon events corresponding to the transmitted light beam.

15. A transmitter device for optical wireless communication comprising: an array of VCSELs, each configured to emit a light beam in a different direction; a selective activation mechanism configured to activate a specific VCSEL based on its alignment with a receiver device to establish a communication link.

16. The transmitter device of claim 15, further comprising a modulation unit configured to modulate the light beam emitted by the selected VCSEL using On-Off Keying (OOK) modulation.

17. A receiver device for optical wireless communication comprising: an array of SPADs, each configured to detect light from a different direction; a selective activation mechanism configured to activate a specific SPAD based on its alignment with a transmitter device to establish a communication link.

18. The receiver device of claim 17, further comprising a demodulation unit configured to convert detected photons into electrical signals representing data bits.

19. The receiver device of claim 17, wherein the selective activation mechanism is configured to control which SPAD in the array is activated based on the direction of the incoming light beam from the transmitter device.

20. The receiver device of claim 17, wherein the receiver device is configured to provide feedback to the transmitter device for selective activation of the VCSELs.

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