WO2022048845A1

WO2022048845A1 - A receiving system for high speed and large coverage optical wireless communication

Info

Publication number: WO2022048845A1
Application number: PCT/EP2021/071669
Authority: WO
Inventors: Johan-Paul Marie Gerard LINNARTZ
Original assignee: Signify Holding BV
Current assignee: Signify Holding BV
Priority date: 2020-09-03
Filing date: 2021-08-03
Publication date: 2022-03-10
Anticipated expiration: 2023-03-03

Abstract

This invention is related to a solution to an optical wireless communication system (100) with a non-ceiling-mounted access point or communication hub (200). The access point or communication hub (200) is configured to provide an end device (300) in the optical wireless communication system (100) with access to a further network (150). The access point or communication hub (200) comprises a first optical transceiver configured to directly transmit to and receive from the end device (300) by means of a Line-Of-Sight, LOS, optical wireless link with the end device (300); and a second optical transceiver (230) configured to indirectly transmit to and receive from the end-device by means of a Non-Line-Of-Sight, NLOS, optical wireless link with the end device (300) via a reflective surface (101).

Description

A receiving system for high speed and large coverage optical wireless communication

FIELD OF THE INVENTION

The invention relates to the field of optical wireless communication networks, such as Li-Fi networks. More particularly, various methods, apparatus, systems, and computer-readable media are disclosed herein related to a system with receiver diversity to support high speed and large coverage optical wireless communication.

BACKGROUND OF THE INVENTION

To enable more and more electronic devices like laptops, tablets, and smartphones to connect wirelessly to the Internet, wireless communication confronts unprecedented requirements on data rates and also link qualities, and such requirements keep on growing year over year, considering the emerging digital revolution related to Internet-of- Things (loT). Radio frequency technology like Wi-Fi has limited spectrum capacity to embrace this revolution. In the meanwhile, light fidelity (Li-Fi) is drawing more and more attention with its intrinsic security enhancement and capability to support higher data rates over the available bandwidth in visible light, Ultraviolet (UV), and Infrared (IR) spectra. Furthermore, Li-Fi is directional and shielded by light blocking materials, which provides it with the potential to deploy a larger number of access points, as compared to Wi-Fi, in a dense area of users by spatially reusing the same bandwidth. These key advantages over wireless radio frequency communication make Li-Fi a promising secure solution to mitigate the pressure on the crowded radio spectrum for loT applications and indoor wireless access. Other possible benefits of Li-Fi include guaranteed bandwidth for a certain user, and the ability to function safely in areas otherwise susceptible to electromagnetic interference. Therefore, Li-Fi is a very promising technology to enable the next generation of immersive connectivity.

There are several related terminologies in the area of lighting-based communication. Visible-light communication (VLC) transmits data by intensity modulating optical sources, such as light emitting diodes (LEDs) and laser diodes (LDs), faster than the persistence of the human eye. VLC is often used to embed a signal in the light emitted by an illumination source such as an everyday luminaire, e.g. room lighting or outdoor lighting, thus allowing use of the illumination from the luminaires as a carrier of information. The light may thus comprise both a visible illumination contribution for illuminating a target environment such as a room (typically the primary purpose of the light), and an embedded signal for providing information into the environment (typically considered a secondary function of the light). In such cases, the modulation may typically be performed at a high enough frequency to be beyond human perception, or at least such that any visible temporal light artefacts (e.g. flicker and/or strobe artefacts) are weak enough and at sufficiently high frequencies not to be noticeable or at least to be tolerable to humans. Thus, the embedded signal does not affect the primary illumination function, i.e., so the user only perceives the overall illumination and not the effect of the data being modulated into that illumination.

The IEEE 802.15.7 visible-light communication personal area network (VP AN) standard maps the intended applications to four topologies: peer-to-peer, star, broadcast and coordinated. Optical Wireless PAN (OWPAN) is a more generic term than VP AN also allowing invisible light, such as UV and IR, for communication. Thus, Li-Fi is generally accepted as a derivative of optical wireless communications (OWC) technology, which makes use of the light spectrum in a broad scope to support bi-directional data communication. Further standardization of Li-Fi includes the ITU g.9991 and IEEE 802.15.13 and IEEE 802.11bb. These initiatives aim not only to achieve high data rates, adequate coverage but also to search for technical reuse and commonalities with earlier defined radio communication standards/concepts, such as the modulation methods and data protocols.

In a Li-Fi system, the signal is embedded by modulating a property of the light, typically the intensity, according to any of a variety of suitable modulation techniques. For communication at high speed, often Infrared (IR) rather than visible light communication is used. Although the ultraviolet and infrared radiation is not visible to the human eye, the technology for utilizing these regions of the spectra is the same, although variations may occur as a result of wavelength dependencies, such as in the case of refractive indices or due to photonic differences in light emitters and detectors. In many instances there are advantages to using ultraviolet and/or infrared as these frequency ranges are not visible to the human eye, and more flexibility can be introduced in the system. Of course, ultraviolet quanta have higher energy levels compared to those of infrared and/or visible light, which in turn may render use of ultraviolet light undesirable in certain circumstances.

To guarantee a good coverage, Li-Fi access points are usually deployed on the ceiling. This is not attractive for installation in existing homes, offices, or buildings, because it may be quite cumbersome to place extra wires/cables on the ceiling for the access point to get Internet access, or to get access to a backbone network. On the other hand, to deploy an access point at another place, such as on the wall or on the table, rather than on the ceiling may result in performance degradation. For example, the link between the access point and an end device may be easily blocked by another piece of furniture or a moving object.

MARRACCINI PHILIP J ET AL “Smart multi-mode indoor optical wireless design and multimode light source smart energy-efficient links” is related to a smart multimode indoor optical wireless system.

SUMMARY OF THE INVENTION

To overcome the disadvantage in deploying a non-ceiling-mounted access point for optical wireless communication, a non-line-of-sight, NLOS, backup link is employed in addition to a primary line-of-sight link, LOS. The access point has two optical transceivers, with one dedicated to a LOS optical link and the other dedicated to a NLOS optical link via a reflective surface, e.g. a ceiling bounce. The NLOS link may be used to boost the data rate between the access point and an end device when the LOS link is also available. The NLOS link may also be used as a backup connection when the LOS is not available.

In view of the above, the present disclosure is directed to methods, apparatus, systems, computer program and computer-readable media for providing improved reliability or data rate between an apparatus and an end device in an optical wireless communication system. More particularly, the goal of this invention is achieved by an apparatus as claimed in claim 1, by an end device as claimed in claims 8 and 10, by a method of an apparatus as claimed in claim 11, by a method of an end device as claimed in claims 12 and 13, by an optical wireless communication system as claimed in claims 14 and 15, and by a computer program as claimed in claim 16.

In accordance with a first aspect of the invention an apparatus is provided. An apparatus for use in an optical wireless communication system configured to provide an end device in the optical wireless communication system with access to a further network, the apparatus comprising: a first communication unit configured to maintain a first bi-directional connection to the further network; a first optical transceiver configured to directly transmit to and receive from the end device by means of a Line-Of-Sight, LOS, optical wireless link with the end device; and a second optical transceiver configured to indirectly transmit to and receive from the end-device by means of a Non-Line-Of-Sight, NLOS, optical wireless link with the end device via a reflective surface; wherein the second optical transceiver has a larger field-of-view, FoV, than the first optical transceiver; and wherein the first optical transceiver and the second optical transceiver are connected to the first communication unit, and the first optical transceiver and the second optical transceiver are further configured to operate in parallel in a coordinated manner by either sending and receiving the same data when the LOS optical wireless link is not available to the end device or operating in a multiple-input and multiple-output, MIMO, setup when the LOS optical wireless link is also available to the end device.

Preferably, the FoV here indicates an effective FoV. The second optical transceiver emits toward the reflective surface, where the (mostly diffusely) scattered signal has a Lambertian re-radiation pattern that is wide in beam by nature. As an example, even if the transmitter of the second transceiver points its signal towards the ceiling, its scattered waves have effectively a wide FoV, seen from the area of reflection. Preferably, for reception, the receiver of the second transceiver also has a wide opening angle from which it is sensitive to surface-reflected signals.

The apparatus may be a hub, an access point, a repeater, an extender, or a wireless docking station. On one side, the apparatus has an optical wireless communication interface with the end device in the optical wireless communication system. On the other side, the apparatus has another interface to a further network. The further network may be a backbone network, or another network with connection to the Internet and/or the cloud.

An optical wireless link is typically of a limited coverage, such as depending on the field-of-view (FoV) of the optical transceiver. However, a large opening angle of the optical transceiver in the apparatus, or access point, may also lead to the situation that signals arrive at the user device or end device under a very slant angle, which may be easily blocked by an obstacle and do not deliver photons efficiently either. It is thus beneficial to provide a NLOS link via a reflective surface in addition to the primary LOS link. The second optical transceiver transmits and receives towards the reflective surface, with the intention to create a large coverage via the reflective surface. As compare to the first optical transceiver, the second optical transceiver has a larger FoV. For example, the second optical transceiver may have an opening angle of 30 degrees or more.

Preferably, the reflective surface may be a ceiling, which reflects the light projected to it. In one example, the apparatus illuminates the majority part of ceiling with data signals and uses the ceiling as a reflector to avoid slant angles of a direct link towards some user devices located at the edge of the optical coverage with a LOS link. The ceiling becomes one large distributed emitting surface and gives shadow-free reception for user devices.

Since the direct LOS optical wireless link delivers photons much more efficiently as compared to the indirect NLOS optical link, for at least the reason of a shorter distance, the direct LOS optical wireless link is configured to support a relatively higher data rate communication than the indirect NLOS optical wireless link. In another word, when a certain end device is within a FoV of the direct LOS link, it may enjoy higher data rate. When the end device moves out of the FoV of the direct LOS link, it may still keep the connection with the apparatus by switching to the indirect NLOS link with a lower data rate communication.

The first optical transceiver may be of a higher performance than the second optical transceiver, such as the first optical transceiver may support a larger bandwidth. The first and the second optical transceivers may comprise one or more light sources, which may be one of a light-emitting diode (LED), a LED array, a laser, a laser diode, a VCSEL (vertical -cavity surface-emitting laser), or a VCSEL array. In one example, the first optical transceiver comprises at least a VCSEL configured to emit high speed data towards the end device, while the second optical transceiver comprises at least a LED configured to illuminate the reflective surface with a large opening angle. Correspondingly, the first optical transceiver may comprise a first photo detector, or a first type of photo detector, suitable for reception of a high-speed optical signal, while the second optical transceiver may comprise a second photo detector, or a second type of photo detector, suitable for wide angle reception.

The first optical transceiver and the second optical transceiver operate in parallel, which may be used to serve the same end device or different end devices. In one example, the first optical transceiver may establish a LOS link with a first end device, while the second optical transceiver may establish a NLOS link with a second end device, in another example, the first end device may have both LOS and NLOS links via the first optical transceiver and the second optical transceiver respectively, while the second end device may have only a single link with the apparatus, which is either a LOS link or a NLOS link. In a further example, both the first end device and the second end device may both have the two links active, when the first end device and the second end device are located next to each other.

Optionally the axis through the NLOS optical transmit cone and axis through the LOS transmit optical cone is at an angle within the range of 60-120 degrees. Conversely the axis through the NLOS receiver cone and axis through the LOS receiver cone is at an angle within the range of 60-120 degrees. In this manner when the NLOS transmitter is directed at the ceiling, the LOS optical cone can be aimed directly at devices that are located elsewhere in the same indoor space, where preferably that the NLOS cone angle is larger than the LOS cone angle.

Preferably, the first bi-directional connection with the further network can be either a wireless connection or a wired connection.

The first bi-directional connection is used to establish the connection between the optical wireless communication system and the further network. The further network may comprise a data center or a central controller. It may also be that the further network provides the access to a backbone network, the Internet, or the cloud.

The first bi-directional connection may be either a wired connection or a wireless connection. The first communication unit may be one of: an Ethernet transceiver, a fiber optic transceiver, a transceiver suitable for power-line-communication, a transceiver suitable for power-over-fiber technology, an optical wireless transceiver, and a millimeter wave transceiver.

Advantageously, the apparatus is configured to operate as at least one of: a communication hub, an access point device, a repeater device, an extender device, and a wireless docking station.

In a preferred setup, the second optical transceiver of the apparatus comprises a photonic concentrator with a wavelength conversion to provide a large receiving aperture and a wide opening angle.

For optical wireless communication, the electrical bandwidth of an optical receiver is typically inversely proportional to the photodetector (PD) active area. Consequently, to construct a high-speed optical wireless link, the PD active area is often substantially reduced, and an optical concentrator is used to enhance the receiver collection area. However, to achieve high concentrating factor, the FOV needs to be narrow due to the etendue conservation in linear passive optical systems. Recent studies show that a Fluorescent Concentrator (FC) can break this etendue conservation. The light that enters the FC will be absorbed by a fluorophore. Some of the light will be re-emitted and retained within the concentrator by total internal reflection (TIR). In a well-designed FC, any light which avoids reabsorption eventually reaches a detector at one end of the FC. These processes therefore make it possible to collect light over a large area and FOV and concentrate it onto a smaller area to achieve high gain. Thus, it is very beneficial to employ this technique in the second optical transceiver of the apparatus to boost the data rate on the receiving path of the NLOS link.

Hence, it may well be that the receiver of the second optical transceiver has a physically wide FoV, such as via a FC, and the transmitter of the second optical transceiver may have an effectively wide FoV as the reflective surface may scatter the light anyhow.

In one embodiment, the first optical transceiver and the second optical transceiver are further configured: to transmit same first data obtained from the first communication unit; to receive same second data sent by the end device; and to provide the same second data to the first communication unit.

The first optical transceiver and the second optical transceiver are configured to operate in a coordinated manner. In one setup, the same first data are transmitted by the first optical transceiver and the second optical transceiver. An end device may then preferentially establish a connection to the apparatus either with the LOS link or the NLOS link. The main intention of this setup is for reliability enhancement. Firstly, since the second optical transceiver has a larger effective FoV, i.e., it effectively spreads its signal over a wider area, as compared to the first optical transceiver, a larger effective FoV promises better coverage and also a higher chance that the end device can establish a link with the apparatus. Secondly, as disclosed above the direct LOS link typically supports higher data rate or provides better signal quality than the indirect NLOS link, and thus it may be beneficial that the same first data or same information is sent on the LOS link and the NLOS link with different coding or modulation schemes of parameter settings, such as modulation bandwidth or modulation constellation (number of bits per symbol). In one example, on the LOS link, the same data is sent with a higher order coding and modulation scheme as compared to the NLOS link. Thus, a shorter packet length can be used for the same data over the LOS link, leading to higher energy efficiency of both the apparatus and the end device when using this link.

Similarly, for receiving from the end device, the first optical transceiver and the second optical transceiver may be used as backup for each other. For example, when the end device is roaming out of the FoV of the first optical transceiver during a session, it may seamlessly switch to the second optical transceiver to continue the session with the NLOS link. In another example, the end device may inform the access point about the failure of the LOS link via the NLOS and to request a retransmission of a data packet that was interrupted with the NLOS link. In another embodiment, the apparatus further comprising: a conversion unit configured to split first data received from the first communication unit into a first subset of the first data and a second subset of the first data, and to provide the first subset of the first data and the second subset of the first data to the first optical transceiver and the second optical transceiver respectively; to combine third data received from the first optical transceiver and fourth data received from the second optical transceiver to second data, and to provide the second data to the first communication unit. The first optical transceiver is further configured: to connect to the first communication unit via the conversion unit; to transmit the first subset of the first data obtained from the conversion unit, to receive the third data sent by the end device; and to provide the third data to the conversion unit. The second optical transceiver is further configured to connect to the first communication unit via the conversion unit; to transmit the second subset of the first data obtained from the conversion unit, to receive the fourth data sent by the end device; and to provide the fourth data to the conversion unit; and wherein the first optical transceiver and the second optical transceiver are configured to operate in a multiple-input and multiple-output, MEMO, setup.

In this setup, the first optical transceiver and the second optical transceiver are employed to boost data rate with a MIMO setup. Instead of sending and receiving the same data, a conversion unit is deployed in the apparatus to either split or combine information for the data to be transmitted or received by the first optical transceiver and the second optical transceiver. Thus, the conversion unit is placed between the first communication unit and the two optical communication branches to assist the MIMO communication. When an end device is in the coverage of both the direct LOS link and indirect NLOS link, such a setup may significantly increase the throughput between the apparatus and the end device. Such MIMO signal processing may not necessarily split the data strictly into two disjoint sets, in which every data symbol in one of the subgroups can be uniquely recognized as representing a user data symbol. In fact, coding may be applied, and redundancy may be adding among and across the two spatial streams.

Preferably, the apparatus comprised in one of: a desk lamp, a floor lamp; a power outlet socket; a controller; a monitor; a TV; and another display device.

To avoid the burden of wiring in/on the ceiling, it is preferable to deploy such a non-ceiling-mounted apparatus. The apparatus may be a standalone device operated as a communication hub, an access point device, a repeater device, an extender device, or a wireless docking station. The apparatus may also be comprised in an existing electronic device to carry out the function of a communication hub, an access point device, a repeater device, an extender device, or a wireless docking station. The existing electronic device may be an electronic appliance commonly deployed in a home or office environment, such as a desk lamp, a floor lamp, a mains power outlet socket, a wall mounted connected device (such as a thermostat), a controller, a monitor, a TV, another display device, or another user interface or control device.

In accordance with a second aspect of the invention an end device is provided. In a first setup, an end device in an optical wireless communication system for obtaining access to a further network via an apparatus in the optical wireless communication system, the end device comprising: a third optical transceiver configured to directly transmit to and receive from the apparatus by means of a Line-Of-Sight, LOS, optical wireless link with the apparatus; and a fourth optical transceiver configured to indirectly transmit to and receive from the apparatus by means of a Non-Line-Of-Sight, NLOS, optical wireless link with the apparatus via a reflective surface; wherein the fourth optical transceiver has a larger FoV than the third optical transceiver.

In a preferred example, the FoV here indicates an effective FoV, a larger FoV of the fourth transceiver may be achieved by anticipating diffuse scattering, against a reflective surface, for instance a wall or ceiling.

The end device may have a similar system setup as the apparatus, which has two optical transceivers dedicated for the LOS link and the NLOS link, respectively. Although the two optical transceivers in the apparatus are operating in parallel, it is not necessary for the end device to operate in the same manner, such as to enable both optical transceivers simultaneously. It may not be in favor of energy saving at the end device, considering that a mobile end device is typically powered by a battery. It may well be the case that the end device enables one optical transceiver out of the two, given an availability of either the LOS link or the NLOS link, an application requirement, a user preference, or another factor. The end device may enable both the first optical transceiver and the second optical transceiver only when a high data rate is needed, such as required by a high-resolution application. Then the data on the LOS link and on the NLOS link are aggregated, as in a MIMO setup.

Advantageously, the fourth optical transceiver of the end device comprises a photonic concentrator with a wavelength conversion to provide a large receiving aperture and a wide opening angle.

Similar to what is disclosed for the second optical transceiver of the apparatus according to the present invention, it may also be very beneficial to employ the Fluorescent Concentrator (FC) technique in the fourth optical transceiver of the end device to boost the data rate on the receiving path of the NLOS link.

Thus, it may well be that the receiver of the fourth optical transceiver has a physically wide FoV, such as via a FC, and the transmitter of the fourth optical transceiver may have an effectively wide FoV as the reflective surface may scatter the light anyhow.

In a second setup of the end device, the end device comprising: a fifth optical transceiver configured to either directly transmit to and receive from the apparatus by means of a Line-Of-Sight, LOS, optical wireless link with the apparatus or indirectly transmit to and receive from the apparatus by means of a Non-Line-Of-Sight, NLOS, optical wireless link with the apparatus via a reflective surface; wherein the end device is configured to select between the LOS optical wireless link and the NLOS optical wireless link according to at least one of: a link quality evaluation parameter; a power consumption requirement; a battery status; a data rate requirement; an application requirement; a user preference; and an availability of either one of the two links.

The end device may also have a different system setup as compared to the apparatus. In this setup, the end device has only a single optical transceiver. The end device is configured to use the single optical transceiver to set up either a LOS link or a NLOS link, depending on one or more factors to be considered, or the availability or link quality of either one of the two links. In one example, if the reflective surface is the ceiling, the fifth optical transceiver may be configured to transmit and receive either directly towards the apparatus for a LOS link or towards the ceiling for a NLOS link with the same apparatus.

For a NLOS link, the end device may be allowed and may also be required to emit more power for a decent link quality. When battery power gets low, the end device may be more critical on the power consumption aspect and opts for a more efficient transmission mode, such as the LOS link if it is available. Since typically a higher data rate is supported on the LOS link, certain applications requiring a high data rate may only be supported by the LOS link. For other applications with low to medium data rate requirements, the end device may select freely between the LOS link and NLOS link without considering data rate limitation. Furthermore, since the NLOS link has a larger field of view, a user with privacysensitive data may preferentially select the more dedicated LOS link instead of the NLOS link.

In accordance with a third aspect of the invention an optical wireless communication system is provided. The optical wireless communication system comprises an apparatus and an end device; wherein the apparatus is configured to provide the end device access to a further network, wherein the apparatus and the end device are in accordance to the present invention.

Advantageously, the reflective surface used in the NLOS link is a ceiling or a wall with a foil or coating to improve the reflection for optical signals.

The reflective surface can be a ceiling, a wall, a floor, or another surface on a piece of furniture or appliance in the environment. The reflective surface may also be part of the system. The communication efficiency on the NLOS link is greatly influenced by the reflectance of the surface. The reflectance is the fraction of incident light reflected from a surface, which is an intrinsic optical property of the surface. A special paint/coating or a covering layer/film may be applied on the surface to improve the reflectance, such as to keep the surface reflectance larger than 0.6. In one example, the reflective surface acts as a Lambertian radiator. As compared to the direct LOS link, only a few dB may be lost due to reflection and a longer propagation path in the NLOS link.

In accordance with a fourth aspect of the invention a method of an apparatus is provided, specifically a method of an apparatus in an optical wireless communication system for providing an end device in the optical wireless communication system with access to a further network, the method comprising the apparatus: maintaining a first bi-directional connection to the further network; directly transmitting to and receiving from the end device, by a first optical transceiver, by means of a Line-Of-Sight, LOS, optical wireless link with the end device; and indirectly transmitting to and receiving from the end device, by a second optical transceiver, by means of a Non-Line-Of-Sight, NLOS, optical wireless link with the end device via a reflective surface; wherein the second optical transceiver has a larger field- of-view, FoV, than the first optical transceiver; operating the first optical transceiver (220) and the second optical transceiver (230) in parallel in a coordinated manner by either sending and receiving the same data when the LOS optical wireless link is not available to the end device or operating in a multiple-input and multiple-output, MIMO, setup when the LOS optical wireless link is also available to the end device.

In accordance with a fifth aspect of the invention a method of an end device is provided, specifically a method of end device in an optical wireless communication system for obtaining access to a further network via an apparatus in the optical wireless communication system, the method comprising the end device: directly transmitting to and receiving from the apparatus, by a third optical transceiver, by means of a Line-Of-Sight, LOS, optical wireless link with the apparatus; and indirectly transmitting to and receiving from the apparatus, by a fourth optical transceiver, by means of a Non-Line-Of-Sight, NLOS, optical wireless link with the apparatus via a reflective surface; wherein the fourth optical transceiver has a larger FoV than the third optical transceiver.

In another option, the method comprising the end device: either directly transmitting to and receiving from the apparatus by means of a Line-Of-Sight, LOS, optical wireless link with the apparatus or indirectly transmitting to and receiving from the apparatus by means of a Non-Line-Of-Sight, NLOS, optical wireless link with the apparatus via a reflective surface; selecting between the LOS optical wireless link and the NLOS optical wireless link according to at least one of: a link quality evaluation parameter; a power consumption requirement; a battery status; a data rate requirement; an application requirement; a user preference; and an availability of either one of the two links.

The invention may further be embodied in a computing program comprising code means which, when the program is executed by an optical front-end subsystem comprising processing means, cause the processing means to perform the method of the optical front-end subsystem as disclosed in the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the same parts throughout the different figures. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

FIG. 1 illustrates an overview of the optical wireless communication system comprising at least an apparatus and one or more end devices;

FIG. 2 demonstrates an example of coverage areas of a LOS link and a NLOS link;

FIG. 3 schematically depicts basic components of the apparatus;

FIG. 4 schematically depicts basic components of the apparatus in another setup;

FIG. 5 schematically depicts basic components of the end device in a first setup;

FIG. 6 schematically depicts basic components of the end device in a second setup;

FIG. 7 shows a flow chart of a method of the apparatus;

FIG. 8 shows a flow chart of a method of the end device;

FIG. 9 shows a flow chart of another method of the end device. DETAILED DESCRIPTION OF EMBODIMENTS

Various embodiments of the present invention will now be described based on an optical communication system 100 as shown in FIG. 1. The optical communication system 100 comprises at least an apparatus 200 and one or more end devices 300, 300’. The apparatus 200 is configured to provide the end device 300, 300’ access to a further network 150. The apparatus 200 may be a communication hub, an access point device, a repeater device, an extender device, or a wireless docking station. To avoid the burden of wiring on the ceiling, it is desirable that the apparatus 200 is deploy as a non-ceiling-mounted apparatus. The apparatus may be a standalone device. The apparatus may also be comprised in an existing electronic device with another function in addition to carrying out the function of a communication hub, an access point device, a repeater device, an extender device, or a wireless docking station. The existing electronic device may be an electronic appliance commonly deployed in a home or office environment, such as a desk lamp, a floor lamp, a monitor, a TV, or another display device. The end device 300, 300’ may be a standalone device comprising at least an optical transceiver. The end device 300, 300’ may also be a smart phone, a laptop, a tablet, or another mobile electronic device, which has an optical transceiver partially or fully integrated. For the apparatus 200, on the one side, it has a stable high-speed connection, either a wired connection or a wireless connection, to the further network 150. On the other side, the apparatus 200 supports LOS and/or NLOS optical wireless links to the one or more end devices 300, 300’. In the example shown in FIG. 1, the apparatus 200 has both a direct LOS optical wireless link and an indirect NLOS optical wireless link with the first end device 300. With the second end device 300’, the apparatus has only an indirect NLOS optical wireless link. The NLOS links between the apparatus 200 and the end devices 300, 300’ are established via a reflective surface 101. The reflective surface 101 may be a ceiling, a wall, a floor, or another surface on a piece of furniture or appliance, which has a special paint/coating or a covering layer/film on the surface to improve the reflectance, such as to keep the surface reflectance larger than 0.6. In one example, the surface reflectance may be in the range of 0.6 to 0.8.

FIG. 2 demonstrates an example of coverage areas of a LOS link and a NLOS link. FIG. 2 is shown in a top view. The example here is merely for illustration purposes. The actual shape and size of a coverage area may differ because of a different optical component used in the apparatus 200. Via the reflective surface, the coverage of the NLOS link is typically much larger than the LOS link. In a preferred example, a ceiling is used as the reflective surface 101, light bouncing off from the ceiling may provide a good coverage and link performance. In this example, the apparatus 200 illuminates the majority part of ceiling 101 with data signals and uses the ceiling as a reflector to avoid slant angles of a direct link towards an end device located at the edge of the optical coverage with a LOS link. The ceiling becomes one large distributed emitting surface and provides shadow-free reception for end devices.

However, due to the longer propagation distance and the extra loss due to reflection on the reflective surface, the NLOS optical link is typically less efficient for delivering photons as compared to the LOS optical link, and thus only a reduced data rate can be supported by the NLOS link. In a preferred system configuration, the NLOS optical link of the disclosed system is optimized for coverage, while the LOS optical link is optimized for speed.

FIG. 3 schematically depicts basic components of the apparatus 200. The apparatus 200 comprises at least a first communication unit 210, a first optical transceiver 220, and a second optical transceiver 230. The first communication unit 210 provides the bidirectional interface to the further network 150. The first optical transceiver directly transmits to and receives from the end device 300 by means of a LOS optical wireless link with the end device 300. The second optical transceiver 230 does not have a direct LOS link with the end devices 300, 300’. The second optical transceiver 230 may be oriented towards the reflective surface 101, and indirectly transmits to and receives from one or more end devices 300, 300’ by means of a NLOS optical wireless link with one or more end devices 300, 300’ via the reflective surface 101. The second optical transceiver 230 has a larger FoV than the first optical transceiver. The first optical transceiver 220 has a relatively narrow FoV for highspeed optical wireless communication, while the second optical transceiver 230 has a much larger FoV with a low to medium data rate optical communication.

As one example of the apparatus 200, the first optical transceiver 220 may be configured to operate in a docking-style, which faces directly to the targeted end device 300 with a high-speed LOS link. To this end the high-speed LOS link may use a segmented frontend with the segments oriented in different directions, thereby allowing selection of a link in a suitable direction, or alternatively an optical front-end with a redirectable optical frontend, so that it can be manually or automatically re-directed. The second optical transceiver 230 may be configured to face the reflective surface 101, such as the ceiling. The transmitter of the second optical transceiver 230 may be configured to illuminate a wide area on the reflective surface 101 with a relatively high output power. When the apparatus 200 is properly placed with the second optical transceiver 230 facing the ceiling, a relatively high output power of the second optical transceiver 230 will not run the risk of potential damage to human eyes. The receiver of the second optical transceiver 230 may also have a larger opening angle than the first optical transceiver 220. Alternatively, a larger FoV is created virtually by emitting a moderately wide beam to a diffusely reflecting surface. From this reflection on, the signal is scattered in a wide angle. Preferably, the receiver of the second optical transceiver 230 is configured to oversee a majority part of the reflective surface 101, or the entire reflective surface 101, or at least a sufficiently large part of that surface such that reflections from the illuminated part of the surface can reach all relevant locations in the room. Accordingly, when the reflective surface 101 is the ceiling, the second optical transceiver may have a good coverage of the majority part of the room, or even the entire room.

In a preferred setup, the first optical transceiver 220 may be a high-speed narrow beam optical transceiver, such as with a VCSEL based light source and a small opening angle light sensor. The second optical transceiver 230 may be a medium to low speed wide beam optical transceiver, such as with a LED based light source and a wide opening angle light sensor.

The first optical transceiver 220 and the second optical transceiver 230 may be configured to operate in a coordinated manner. The LOS link and NLOS link, between the first optical transceiver 220 and the second optical transceiver 230 and the one or more end devices, are deployed in a duplicated manner adding redundancy for reliability enhancement. Since the second optical transceiver 230 has a relatively wide FoV, it is of a better chance that the end device can establish a link with the apparatus via the second optical transceiver 230. When the end device is within the FoV of the first optical transceiver 220, it may preferentially establish the LOS link with the apparatus. When the end device moves out of the FoV of the first optical transceiver 220, the first optical transceiver 220 and the second optical transceiver 230 may cooperate to achieve a seamless handover. Similarly, for receiving from the end device 300, 300’, when the end device 300, 300’ is roaming out of the FoV of the first optical transceiver 220 during an uplink session, it may seamlessly switch to the second optical transceiver 230 to continue the session with the NLOS link. And hence, the connection between the apparatus and the end device is maintained when the end device is roaming in the area.

Furthermore, as disclosed above the direct LOS link typically supports higher data rate or provides better signal quality than the indirect NLOS link, it may be beneficial that the same first data or same information is sent on the LOS link and the NLOS link using different coding or modulation schemes. In one example, the same data or information is sent on the LOS link with a higher order coding and modulation scheme and/or with a larger bandwidth as compared to the NLOS link. Thus, a shorter packet length is needed to deliver the same data or information over the LOS link, leading to higher energy efficiency of both the apparatus and the end device.

FIG. 4 schematically depicts basic components of the apparatus 200 in another setup. As compared to the setup in FIG. 3, here the apparatus 200 further comprises a conversion unit 240. The conversion unit 240 is deployed between the first communication unit 210 and the first and second optical transceivers. The conversion unit 240 splits first data received from the first communication unit 210 for transmission into two parts, such as a first subset and a second subset. This splitting can be mapping by means of coding where the one- to-one relation between user data symbols and data elements of the first or second subset is not directly distinguishable. For instance, either subset may carry redundancy bits for the other subset. Then, the conversion unit 240 provides the first subset to the first optical transceiver 220 and provides the second subset to the second optical transceiver 230. For receiving, the conversion unit 240 combines third data received from the first optical transceiver 220 and fourth data received from the second optical transceiver 230 to a single data stream and provides the single data stream to the first communication unit 210. Thus, the conversion unit 240 is used to assist the first optical transceiver 220 and the second optical transceiver 230 for a MIMO setup. In this setup, the LOS optical link and the NLOS optical link are aggregated for an increased data rate. This is very beneficial when the end device 300 is in the coverage of both links.

FIG. 5 schematically depicts basic components of the end device 300, 300’ in a first setup. The end device 300, 300’ comprises at least a third optical transceiver 320 for a direct LOS link with the apparatus 200, and a fourth optical transceiver 330 for an indirect NLOS link with the apparatus 200 via the reflective surface 101. The third optical transceiver 320 and the fourth optical transceiver 330 of the end device operate as a counterpart to the first optical transceiver 220 and the second optical transceiver 230 in the apparatus, respectively. Thus, the third optical transceiver 320 faces directly to the apparatus 200, while the fourth optical transceiver 330 faces to the reflective surface 101.

Optionally, the end device 300, 300’ may further comprise a controller 350 and a user interface 360. Given that the end device 300 may be a standalone optical wireless transceiver, a smart phone, a laptop, a tablet, or another mobile electronic device, a user interface 360 may provide extra convenience to the user in controlling the end device 300 and interacting to the system, such as to read out a link status regarding to either the LOS link or the NLOS link with the apparatus 200. The controller 350 may be used to do further assessment or processing on the data obtained via the third optical transceiver 320 and the fourth optical transceiver 330, such as to compare or to combine information.

FIG. 6 schematically depicts basic components of the end device 300 in a second setup. The end device 300 comprises a fifth optical transceiver 340 configured to either directly transmit to and receive from the apparatus 200 by means of a LOS optical wireless link or indirectly transmit to and receive from the apparatus 200 by means of a Non- NLOS optical wireless link via a reflective surface. The selection among the two options may be made according to at least one of: a link quality evaluation parameter; a power consumption requirement; a battery status; a data rate requirement; an application requirement; a user preference; and an availability of either one of the two links.

Similar to the first setup, the end device 300, 300’ in the second setup may also comprise a controller 350 and a user interface 360. The controller here may be used to make the assessment of the different factors as disclosed above in making the selection between the LOS and NLOS optical links.

FIG. 7 shows a flow chart of a method 500 of the apparatus 200 in an optical wireless communication system 100 for providing an end device 300 in the optical wireless communication system 100 with access to a further network 150. The method 500 comprises the apparatus 200 in step S501 maintaining a first bi-directional connection to the further network 150; and in step S502, directly transmitting to and receiving from the end device 300, by a first optical transceiver 220, by means of a Line-Of-Sight, LOS, optical wireless link with the end device 300; and in step S503, indirectly transmitting to and receiving from the end device, by a second optical transceiver 230, by means of a Non-Line-Of-Sight, NLOS, optical wireless link with the end device 300 via a reflective surface; wherein the second optical transceiver 230 has a larger field-of-view, FoV, than the first optical transceiver 220.

FIG. 8 shows a flow chart of a method 600 of the end device 300 for obtaining access to a further network 150 via an apparatus 200. The method 600 comprises the end device 300 carrying out the following steps: in step S601, the end device 300 directly transmits to and receives from the apparatus 200, by a third optical transceiver 320, by means of a LOS optical wireless link with the apparatus 200; and in step S602, indirectly transmits to and receives from the apparatus 200, by a fourth optical transceiver 330, by means of a NLOS optical wireless link with the apparatus 200 via a reflective surface; wherein the fourth optical transceiver 330 has a larger FoV than the third optical transceiver 320.

FIG. 9 shows a flow chart of another method 700 of the end device 300. The method 700 comprises the end device 300 carrying out the following steps: in step S701, the end device selects between a LOS optical wireless link and a NLOS optical wireless link according to at least one of a link quality evaluation parameter, a power consumption requirement, a battery status, a data rate requirement, an application requirement, a user preference, and an availability of either one of the two links. The end device 300 either carries out step S702 to directly transmit to and receive from the apparatus 200 by means of the LOS optical wireless link with the apparatus 200; or carries out step S703 to indirectly transmit to and receive from the apparatus 200 by means of a NLOS optical wireless link with the apparatus 200 via a reflective surface.

The methods according to the invention may be implemented on a computer as a computer implemented method, or in dedicated hardware, or in a combination of both.

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

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

The term “controller” is used herein generally to describe various apparatus relating to, among other functions, the operation of one or more network devices or coordinators. A controller can be implemented in numerous ways (e.g., such as with dedicated hardware) to perform various functions discussed herein. A “processor” is one example of a controller which employs one or more microprocessors that may be programmed using software (e.g., microcode) to perform various functions discussed herein. A controller may be implemented with or without employing a processor, and also may be implemented as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions. Examples of controller components that may be employed in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs).

In various implementations, a processor or controller may be associated with one or more storage media (generically referred to herein as “memory,” e.g., volatile and non-volatile computer memory such as RAM, PROM, EPROM, and EEPROM, compact disks, optical disks, etc.). In some implementations, the storage media may be encoded with one or more programs that, when executed on one or more processors and/or controllers, perform at least some of the functions discussed herein. Various storage media may be fixed within a processor or controller or may be transportable, such that the one or more programs stored thereon can be loaded into a processor or controller so as to implement various aspects of the present invention discussed herein. The terms “program” or “computer program” are used herein in a generic sense to refer to any type of computer code (e.g., software or microcode) that can be employed to program one or more processors or controllers.

The term “network” as used herein refers to any interconnection of two or more devices (including controllers or processors) that facilitates the transport of information (e.g. for device control, data storage, data exchange, etc.) between any two or more devices and/or among multiple devices coupled to the network.

Claims

CLAIMS:

1. An apparatus (200) for use in an optical wireless communication system configured to provide an end device (300) in the optical wireless communication system with access to a further network (150), the apparatus (200) comprising: a first communication unit (210) configured to maintain a first bi-directional connection to the further network (150); a first optical transceiver (220) configured to directly transmit to and receive from the end device (300) by means of a Line-Of-Sight, LOS, optical wireless link with the end device (300); and a second optical transceiver (230) configured to indirectly transmit to and receive from the end-device by means of a Non-Line-Of-Sight, NLOS, optical wireless link with the end device (300) via a reflective surface; wherein the second optical transceiver (230) has a larger field-of-view, FoV, than the first optical transceiver (220); and wherein the first optical transceiver (220) and the second optical transceiver (230) are connected to the first communication unit (210), and the first optical transceiver (220) and the second optical transceiver (230) are further configured to operate in a coordinated manner in parallel by either sending and receiving the same data when the LOS optical wireless link is not available to the end device or operating in a multiple-input and multiple-output, MEMO, setup when the LOS optical wireless link is also available to the end device.

2. The apparatus (200) according to claim 1, wherein the first bi-directional connection with the further network (150) can be either a wireless connection or a wired connection.

3. The apparatus (200) according to claim 1 or 2, the apparatus (200) configured to operate as at least one of: a communication hub, an access point device, a repeater device, an extender device, and a wireless docking station.

4. The apparatus (200) according to any one of the previous claims 1-3, wherein the second optical transceiver (230) comprises a photonic concentrator with a wavelength conversion to provide a large receiving aperture and a wide opening angle.

5. The apparatus (200) according to any one of the previous claims 1-4, wherein the first optical transceiver (220) and the second optical transceiver (230) are further configured:

- to transmit same first data obtained from the first communication unit (210);

- to receive same second data sent by the end device (300); and

- to provide the same second data to the first communication unit (210).

6. The apparatus (200) according to any one of the previous claims 2-4, the apparatus (200) further comprising: a conversion unit (240) configured: o to split first data received from the first communication unit (210) into a first subset of the first data and a second subset of the first data, and to provide the first subset of the first data and the second subset of the first data to the first optical transceiver (220) and the second optical transceiver (230) respectively; o to combine third data received from the first optical transceiver (220) and fourth data received from the second optical transceiver (230) to second data, and to provide the second data to the first communication unit (210); and wherein the first optical transceiver (220) is further configured:

- to connect to the first communication unit (210) via the conversion unit (240);

- to transmit the first subset of the first data obtained from the conversion unit

(240),

- to receive the third data sent by the end device (300); and

- to provide the third data to the conversion unit (240); and the second optical transceiver (230) is further configured: to connect to the first communication unit (210) via the conversion unit (240);

- to transmit the second subset of the first data obtained from the conversion unit (240),

- to receive the fourth data sent by the end device (300); and

- to provide the fourth data to the conversion unit (240); and wherein the first optical transceiver (220) and the second optical transceiver (230) are configured to operate in a multiple-input and multiple-output, MEMO, setup.

7. The apparatus (200) according to any one of the previous claims 1-6, the apparatus (200) comprised in one of a desk lamp; a floor lamp; a power outlet socket; a controller; a monitor; a TV; and another display device.

8. An end device (300) in an optical wireless communication system for obtaining access to a further network (150) via an apparatus (200) in the optical wireless communication system, the end device (300) comprising: a third optical transceiver (320) configured to directly transmit to and receive from the apparatus (200) by means of a Line-Of-Sight, LOS, optical wireless link with the apparatus (200); and a fourth optical transceiver (330) configured to indirectly transmit to and receive from the apparatus (200) by means of a Non-Line-Of-Sight, NLOS, optical wireless link with the apparatus (200) via a reflective surface (101); wherein the fourth optical transceiver (330) has a larger FoV than the third optical transceiver (320).

9. The end device (300) according to claim 8, wherein the fourth optical transceiver (330) comprises a photonic concentrator with a wavelength conversion to provide a large receiving aperture and a wide opening angle.

10. An end device (300) in an optical wireless communication system for obtaining access to a further network (150) via an apparatus (200) in the optical wireless communication system, the end device (300) comprising: a fifth optical transceiver (340) configured to either directly transmit to and receive from the apparatus (200) by means of a Line-Of-Sight, LOS, optical wireless link with the apparatus (200) or indirectly transmit to and receive from the apparatus (200) by means of a Non-Line-Of-Sight, NLOS, optical wireless link with the apparatus (200) via a reflective surface; wherein the end device (300) is configured to select between the LOS optical wireless link and the NLOS optical wireless link according to at least one of:

■ a link quality evaluation parameter;

■ a power consumption requirement;

■ a battery status;

■ a data rate requirement;

■ an application requirement;

■ a user preference; and

■ an availability of either one of the two links.

11. A method (500) of an apparatus (200) in an optical wireless communication system for providing an end device (300) in the optical wireless communication system with access to a further network (150), the method (500) comprising the apparatus (200): maintaining (S501) a first bi-directional connection to the further network (150); directly transmitting (S502) to and receiving from the end device (300), by a first optical transceiver (220), by means of a Line-Of-Sight, LOS, optical wireless link with the end device (300); and indirectly transmitting (S503) to and receiving from the end device (300), by a second optical transceiver (230), by means of a Non-Line-Of-Sight, NLOS, optical wireless link with the end device (300) via a reflective surface; wherein the second optical transceiver (230) has a larger field-of-view, FoV, than the first optical transceiver (220); operating the first optical transceiver (220) and the second optical transceiver (230) in parallel in a coordinated manner by either sending and receiving the same data when the LOS optical wireless link is not available to the end device or operating in a multiple-input and multiple-output, MIMO, setup when the LOS optical wireless link is also available to the end device.

12. A method (600) of end device (300) in an optical wireless communication system for obtaining access to a further network (150) via an apparatus (200) in the optical wireless communication system, the method (600) comprising the end device (300): directly transmitting (S601) to and receiving from the apparatus (200), by a third optical transceiver (320), by means of a Line-Of-Sight, LOS, optical wireless link with the apparatus (200); and indirectly transmitting (S602) to and receiving from the apparatus (200), by a fourth optical transceiver (330), by means of a Non-Line-Of-Sight, NLOS, optical wireless link with the apparatus (200) via a reflective surface; wherein the fourth optical transceiver (330) has a larger FoV than the third optical transceiver (320).

13. A method (700) of end device (300) in an optical wireless communication system for obtaining access to a further network (150) via an apparatus (200) in the optical wireless communication system, the method comprising the end device (300): either directly transmitting (S702) to and receiving from the apparatus (200) by means of a Line-Of-Sight, LOS, optical wireless link with the apparatus (200) or indirectly transmitting (S703) to and receiving from the apparatus (200) by means of a Non-Line-Of-Sight, NLOS, optical wireless link with the apparatus (200) via a reflective surface; selecting (S701) between the LOS optical wireless link and the NLOS optical wireless link according to at least one of:

■ a link quality evaluation parameter;

■ a power consumption requirement;

■ a battery status;

■ a data rate requirement;

■ an application requirement;

■ a user preference; and

■ an availability of either one of the two links.

14. An optical wireless communication system (100) comprising: an apparatus (200) according to claim 1; and an end device (300) according to claim 8; wherein the apparatus (200) is configured to provide the end device (300) access to a further network (150).

15. An optical wireless communication system (100) comprising: an apparatus (200) according to claim 1; and an end device (300) according to claim 10; wherein the apparatus (200) is configured to provide the end device (300) access to a further network (150). 16. A computing program comprising code means which, when the program is executed by an apparatus (200) comprising processing means, cause the processing means to perform the method of claim 11, or a computing program comprising code means which, when the program is executed by an end device (300) comprising processing means, cause the processing means to perform the method of claim 12 or 13.