WO2022122550A2

WO2022122550A2 - Optical wireless communication interface utilizing usb

Info

Publication number: WO2022122550A2
Application number: PCT/EP2021/083987
Authority: WO
Inventors: Christian Jordan; Francisco David ROJAS CALVENTE; Michel Germe; Ivo Wilhelmus Johannes Marie RUTTEN
Original assignee: Signify Holding B.V.
Priority date: 2020-12-10
Filing date: 2021-12-02
Publication date: 2022-06-16
Also published as: WO2022122550A3

Abstract

:An optical wireless communication, OWC, device comprising: a USB 2.0 capable controller (602) with a USB bus; a combiner (603) connected to the USB bus, the combiner connected to an optical output path and an optical input path; the optical output path comprising an output amplifier (606) and a light source (608) for emitting modulated light, the optical input path comprising a photodetector (609) and an input amplifier (607). The OWC device further comprising a switching arrangement arranged to: in a first mode connect the differential USB data pair (D-, D+) from the USB 2.0 capable controller to the combiner (603) and in a second mode connect the differential USB data pair (D-, D+) from the USB 2.0 capable controller to the USB connector (605); the switch arrangement operable to switch between modes independence of: the incoming OWC signal or signals on the USB connector (605).

Description

Optical wireless communication interface utilizing USB

FIELD OF THE INVENTION

The invention relates to the field of optical wireless communication interfaces and more in particular a device and system for bi-directional data communication using both an Optical Wireless Communication (OWC) interface and a Universal Serial Bus version 2.0 interface, for use in various different applications for home, office, retail, hospitality and industry.

BACKGROUND OF THE INVENTION

OWC networks, such as Li-Fi networks (named like Wi-Fi networks), enable mobile user devices (called end points (EP) in the following) like laptops, tablets, smartphones or the like to connect wirelessly to the internet. Wi-Fi achieves this using radio frequencies, but Li-Fi achieves this using the light spectrum which can enable unprecedented data transfer speed and bandwidth. Furthermore, it can be used in areas susceptible to electromagnetic interference. It is important to consider that wireless data is required for more than just our traditional connected devices - today televisions, speakers, headphones, printer’s, virtual reality (VR) goggles and even refrigerators use wireless data to connect and perform essential communications. Radio frequency (RF) technology like Wi-Fi is running out of spectrum to support this digital revolution and Li-Fi can help power the next generation of immersive connectivity.

OWC communication networks may utilize visible light but may also utilize infrared light. When OWC is combined with the illumination lighting infrastructure, it may re-use the illumination light for illumination while at the same time conveying information superimposed on the illumination; in other words, the downlink makes use of visible light. Customary in illumination based OWC systems, the uplink makes use of infrared light as this renders the uplink signal less disturbing to the users.

Alternatively, OWC systems may transmit both downlink signal and uplink signals using infrared light or alternatively ultraviolet light. In such systems, the OWC infrastructure can be decoupled from the illumination light infrastructure and at the same time communication is possible even when the illumination light is switched off. OWC systems exist that focus on point-to-point communication, whereby a transmitter device and receiver device use a line-of-sight link to communicate with one another. US patent application US 2011/0231726 Al discloses a repeater and method for relaying a signal provided by means of a Universal Serial Bus version 2.0 (USB) link using an infrared light signal to another device that converts this received infrared light signal back into a USB version 2 signal.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a cost effective and/or small form factor, device for bi-directional data communication using both an Optical Wireless Communication (OWC) interface and a Universal Serial Bus version 2.0 interface, that provides for simplified operation for use in various different applications for home, office, retail, hospitality and industry.

In accordance with a first aspect, an optical wireless communication, OWC, device is provided, comprising a USB 2.0 capable controller having a USB bus; a USB connector on the OWC device exterior, a combiner connectable to the USB bus and connected to an optical output path and an optical input path; the optical output path comprising: an output amplifier arranged to receive an output signal from the combiner and generate an output signal for use in driving a light source; the light source arranged to receive the drive signal from the combiner and emit a modulated light signal; the optical input path comprising: a photodetector arranged to receive an OWC signal comprising data modulated therein and generate a corresponding electrical input signal; an input amplifier arranged to amplify the electrical input signal and output the amplified signal to the combiner, and a switching arrangement arranged to: in a first mode connect the differential USB data pair (D- , D+) from the USB 2.0 capable controller to the combiner and in a second mode connect the differential USB data pair (D-, D+) from the USB 2.0 capable controller to the USB connector; the switch arrangement operable to switch between modes independence of: the incoming OWC signal or signals on the USB connector.

Advantageously the first aspect facilitates a low-cost and user-friendly implementation whereby the ability of the USB 2.0 capable controller to modulate USB 2.0 data is reused for both the optical wireless communication and the wired communication in a seamless manner that allows automatic switching between communication. The output amplifier here may be construed as an output driver for the light source having embedded therein the output data received over the differential USB 2.0 pair (D+, D-). Preferably the USB 2.0 capable controller uses the differential USB 2.0 pair (D-, D+) in the first mode and in the second mode. Optionally, there may be further modes of operation for the USB 2.0 capable controller. The switching arrangement in turn at least switches the differential USB 2.0 pair (D-, D+).

Preferably the USB connector is a USB 2.0 connector. However, it is noted that USB 3.0 connectors also include a differential USB 2.0 pair (D+, D-) for transporting USB 2.0 signals.

In accordance with a first option of the first aspect the OWC device further comprises a DC power detector arranged to detect a DC component in the output of the photodetector and wherein the switching arrangement is arranged to operate in the first mode when a DC power level is detected above a DC threshold. More preferably this first option switches to the second mode otherwise. As a result, the OWC device will prioritize optical wireless data delivery and may operate by default in a “wired” USB mode, but upon the detection of presence of a sufficiently strong DC component in the optical input path will switch to the optical mode.

In accordance with a second option of the first aspect the OWC device further comprises a USB modulation detector arranged to detect a USB modulation signal in the output of the input amplifier and wherein the switching arrangement is arranged to operate in the first mode when a USB modulation signal is detected exceeding a predetermined threshold level by the USB modulation detector. More preferably this second option switches to the second mode otherwise. In this option too, the OWC device will prioritize optical wireless data delivery and the OWC device may operate by default in a “wired” USB mode, but instead of using the photodetector output, this option utilizes the input amplifier output to switch. As a result, the full photodetector signal may be passed on to the input amplifier, without addition of noise.

In accordance with a third option of the first aspect the OWC device further comprises a data input signal detector arranged to detect a USB modulation signal on the data lines of the USB connector and wherein the switching arrangement is arranged to operate in the second mode when a USB modulation signal is detected exceeding a predetermined threshold level by the data input signal detector. More preferably this third option switches to the first mode otherwise.

Contrary to the first and second option, the third option may default to the first mode and controls the switching arrangement to only select the wired USB in case data is detected on the USB bus. The advantage of doing so, is that when a USB charger is connected to the OWC device, any ongoing optical wireless communication may continue without disturbance.

In accordance with a fourth option of the first aspect the OWC device further comprises a DC input power detector arranged to detect a DC power on the USB power lines of the USB connector and wherein the switching arrangement is arranged to operate in the second mode when a USB input power signal is detected exceeding a predetermined threshold level by the DC input signal detector. More preferably this fourth option switches to the first mode otherwise.

Contrary to the first and second option, the fourth option may default to the first mode and controls the switching arrangement to only select the wired USB in case DC power is detected on the USB connector’s power lines. The advantage of doing so, is that when a USB charger is connected to the OWC device, any ongoing optical wireless communication may continue without disturbance.

In accordance with a fifth option of the first aspect the OWC device, which may be combined with any one of the preceding options, the input amplifier is a transimpedance amplifier, which is particularly well suited for light sensing; notably other solutions are possible, but usage of a transimpedance amplifier is preferred.

In accordance with a sixth option, of the first aspect of the OWC device, which may be combined with any one of the preceding options, the OWC device is a portable or handheld portable device. Such an OWC device may be directed by its user towards another device, which may equally be a portable or handheld portable device, or alternatively a stationary device. Advantageously, the light emission pattern of the OWC device has a narrow solid beam angle preferably less than 60 degrees, more preferably less than 45 degrees and yet more preferably less than 30 degrees. As a result, the angular selectivity allows the user to select the OWC communication partner with higher specificity.

In accordance with a seventh option, of the first aspect of the OWC device, which may be combined with any one of the preceding options, the light source is and infrared or ultraviolet light source, preferably selected from the set of an LED light source a laser diode, or a vertical cavity surface emitting laser, VCSEL, light source. By using a semiconductor light source as indicated, the cost and size of the OWC can be kept within bounds. As LEDs tend to have broad output angles, optical means such as collimators and/or lenses may be used to narrow the output beam angle. VCSELs on the other hand tend to have narrow beam angles, and here other optical means such as diffusers and/or lens may be used to shape the beam angle. In accordance with an eighth option, of the first aspect of the OWC device, which may be combined with any one of the preceding options, the photodetector is one of: a photodiode, a phototransistor, an avalanche photo diode and a silicon photon multiplier.

In accordance with a nineth eighth option, of the first aspect of the OWC device, which may be combined with any one of the preceding options, the OWC device further comprises a user input interface, wherein the user interface allows a user to overrule the default switch arrangement setting. In this manner the user may prevent unwanted switching by the switching arrangement and device behaviour may be rendered more predictable.

In accordance with a tenth option, of the first aspect of the OWC device, which may be combined with any one of the preceding options, the OWC device further comprises a battery wherein the OWC device is arranged to charge the battery power is available on the USB connector (605), regardless of the switch arrangement setting. By only switching the differential data pair, the OWC device may benefit from tethered operation, even when data communication is disabled.

In accordance with an eleventh option, of the first aspect of the OWC device, which may be combined with any one of the preceding options, the combiner further comprises an encoder and a decoder, wherein the encoder is arranged to map each of the J, K, SEO USB 2.0 bus states of the combiner input from the USB 2.0 capable controller onto one of three distinct optical output symbol for output by means of the optical output path and the decoder is arranged to map each one of three distinct optical output symbols of the combiner input from the optical input path onto one of the J, K, SEO USB 2.0 bus states for output by the combiner to the USB 2.0 capable controller and wherein the mapping by the encoder and the mapping by the decoder are one another’s inverse. In accordance with this option, it is possible to create a pass-through implementation whereby the combiner may be kept simple. Preferably, the SEI state is not encoded, so as to minimize overhead.

In accordance with a twelfth option, of the first aspect of the OWC device, which may be combined with any one of the preceding options, the combiner further comprises an encoder and a decoder, wherein the encoder is arranged to map each of the J, K, SEO USB 2.0 bus states of the combiner input from the USB 2.0 capable controller onto one of three distinct PAM-3 levels for output by means of the optical output path and the decoder is arranged to map each of three distinct PAM-3 levels of the combiner input from the optical input path onto one of the J, K, SEO USB 2.0 bus states for output by the combiner to the USB 2.0 capable controller and wherein the mapping by the encoder and the mapping by the decoder are one another’s inverse. Advantageously this option allows for a particularly efficient and simple implementation, whereby the combiner maps three USB states on a three-level PAM symbol, thereby enabling a simple pass-through implementation.

In accordance with a thirteenth option, of the first aspect of the OWC device, which may be combined with the first aspect or any one of the first to the nineth options, the combiner further comprises an encoder and a decoder, wherein the encoder is arranged to map each of the four USB 2.0 bus states of the combiner input from the USB 2.0 capable controller onto one of four distinct PAM-4 levels and the decoder is arranged to map each of four PAM-4 symbols of the combiner input from the optical input path onto one of the four USB 2.0 bus states for output by the combiner to the USB 2.0 capable controller and wherein the mapping by the encoder and the mapping by the decoder are one another’ s inverse. This implementation preserves the SEI state at the cost of having to discern between 4 levels in the output from the photodetector.

In accordance with a fourteenth option, of the first aspect of the OWC device, which may be combined with the first aspect or any one of the first to the nineth options the combiner further comprises an encoder and a decoder, wherein the encoder is arranged to map each of the four USB 2.0 bus states of the combiner input from the USB 2.0 capable controller onto combinations of two successive PAM-2 symbols, each PAM-2 symbol having half a period of a USB bus symbol and the decoder is arranged to map each combination of two successive PAM-2 symbols, each PAM-2 symbol having half a period of a USB bus symbol of the combiner input from the optical input path onto one of the four USB 2.0 bus states for output by the combiner to the USB 2.0 capable controller and wherein the mapping by the encoder and the mapping by the decoder are one another’s inverse. Instead of using a 4-level PAM symbol, it may be advantageous to use two successive 2-level symbols instead, as this is more noise resilient and allows a simpler slicer implementation. Notably, the format of the USB 2.0 messages further allows synchronization on account of the presence of the SEO signals.

In accordance with a second aspect an optical wireless communication, OWC, device is provided, comprising: a USB 2.0 capable controller having a USB 2.0 bus; a combiner connected to the USB 2.0 bus and connected to an optical output path and an optical input path; the optical output path comprising: an encoder arranged to receive a differential USB 2.0 input pair (Din-, Din+) from the combiner and map the three valid bus states J, K andSEO onto a respective level of a three-level PAM data signal; a light source for a emitting modulated light signal, arranged to be operated using a drive signal based on the three-level PAM data signal; the optical input path comprising: a photodetector arranged to receive light comprising data modulated as a three-level PAM data signal and generate a corresponding electrical signal; a decoder (105) arranged to generate two USB 2.0 compatible differential signal levels based on the generated electrical signal, and the combiner (103) arranged to: receive the differential USB 2.0 input pair (Din-, Din+) from the USB 2.0 capable controller and route them to the encoder and output a differential USB 2.0 output pair (Dout-, Dout+) to the USB2.0 capable controller based on the two USB 2.0 compatible differential signal levels from the decoder.

The implementation in accordance with the above first aspect facilitates an elegant, low-cost, low-latency implementation of a bi-directional USB2.0 to OWC function. The implementation thus provides an optical USB 2.0 connection that may be used to connect OWC devices, leveraging the signal output of existing USB 2.0 capable controllers.

Preferably, the optical output path further comprises: an amplifier for generating a drive current for operating the light source based on the output from the three- level PAM data signal. As a result, devices can be spaced apart further without loss of signal.

Preferably, the optical input path further comprises a transimpedance amplifier arranged to amplify the signal from the photodetector prior to generating USB 2.0 compatible differential signal levels. As a result, devices can be spaced apart further without loss of signal.

Preferably the OWC device is a portable or handheld portable device. These devices may particularly benefit as such devices customarily are equipped with USB 2.0 output ports.

Preferably the OWC device utilizes a light source that emits infrared light or ultraviolet light, as a result there is less visible light pollution when using such devices. More preferably such and IR or UV light source is selected from the set of Light Emitting Diode (LED) and Vertical Cavity Surface Emitting Laser (VCSEL) light sources.

Preferably the encoder is arranged to map the logical USB SEO state onto a first power output level and each of the J and K states to a respective one of: the first power output level + a first bias power output level and the first power output level - a second bias power output level and wherein the power output level of each of the states is above 0. By doing so, it will be possible to detect presence of another OWC device even when no data is exchanged between OWC devices.

More preferably the first bias and second bias have the same magnitude. Alternatively, the encoder is arranged to map SEO state onto a zero power output level and each of the J and K states to a respective one of: a second power output level and a third power output level different from the second power output level wherein the power output level of each of the states is above 0.

The advantage of doing so is that when no data is transmitted the output power level is zero, resulting in an automatic power saving. However, dummy data transmissions may be required to establish alignment between devices.

More preferably, the second power output level set the power level to a predetermined power level and the third power output level amounts to three times this predetermined power level.

Yet more alternatively the encoder is arranged to map K state onto a zeropower output level and each of the J and SEO states to a respective one of: a second power output level and a third power output level different from the second power output level wherein the power output level of each of the states is above 0.

Using this approach, a low-cost implementation may be realized by outputting a signal corresponding to the D- level and occasionally adding a special offset for the end-of packet state.

Advantageously, the OWC device further comprises: a USB 2.0 connector on the OWC device exterior, a DC input power sensor integrated in the OWC device arranged to sense input power from an external source on the USB 2.0 connector and switching means arranged to switch to connect the USB 2.0 capable controller to the USB connector when the DC input power sensor senses input power and connect the USB 2.0 capable controller to the combiner (603) when no input power is sensed.

In this manner the OWC output may be automatically disconnected from the USB 2.0 capable controller when a wired USB connection is made.

In accordance with a further aspect, a handheld optical wireless communication, OWC, device comprising an integrated optical wireless transceiver comprising: an optical output path comprising a light source arranged to emit a modulated light output signal comprising embedded data and a light source driver arranged to drive the light source using a drive signal comprising the embedded data; an optical input path comprising a photodetector and accompanying optics arranged to direct light impinging on the OWC device towards the photodetector and one or more integrated distance determination means arranged to determine a distance from the respective distance determination means to an object and wherein the optical output path is arranged to inhibit light output from the light source when the determined distance is below a threshold distance.

In accordance with this aspect a distance measurement is performed in order to enable and/or disable the light source or the entire optical output path.

Advantageously, the handheld OWC device comprises one of: a Time-of- Flight sensor (which may e.g. be IR-based or RF -based), such as a 3D face scanning sensor, arranged to determine a distance between an object and the time-of-flight sensor integrated in the OWC device; and an ultrasound time-of-flight transceiver, comprising a speaker arranged to transmit one of more ultrasound pulses at a frequency above 20 kHz and a microphone arranged to receive reflections of the ultrasound pulses, and measure the time difference between the transmitted and reflected ultrasound pulses. Both options allow a distance measurement based on a measured time-difference, the one based on ultrasound using the speed of sound, the one based on light and/or RF based on the speed of light.

In accordance with a final aspect a handheld optical wireless communication, OWC, device is provided comprising an integrated optical wireless transceiver comprising: an optical output path comprising a light source arranged to emit a modulated light output signal comprising embedded data and a light source driver arranged to drive the light source using a drive signal comprising the embedded data; an optical input path comprising a photodetector and accompanying optics arranged to direct light impinging on the OWC device towards the photodetector and a controller for controlling the optical output path and the optical input path to periodically, in between the data communication, preform a distance determination, by means of a distance determination based on a Time-of-Flight measurement using the combined optical output path and optical input path, wherein the light source is arranged to emit one or more light pulses and the photodetector is arranged to receive reflected one or mor light pulses and to determine a time difference by correlating the emitted one or more light pulses with the received reflected one or more light pulses and to determine a distance between the OWC device and the object based on the determined time difference and the light speed.

In accordance with this aspect the optical output path and optical input path are not only used for data communication, but also for the Time-of-Flight distance measurement.

Preferably, multiple modalities for distance measurements may be combined such that if either one of them reports the distance to be below the minimal eye safety distance (for the output power used) are below that minimum plus an addition predetermined margin, to immediately inhibit the light output.

Advantageously the OWC device is one of a mobile phone, a tablet or a personal digital assistant (PDA).

It is noted that the above apparatuses may be implemented based on discrete hardware circuitries with discrete hardware components, integrated chips, or arrangements of chip modules, or based on signal processing devices or chips controlled by software routines or programs stored in memories, written on a computer readable media, or downloaded from a network, such as the Internet.

It shall be understood that a preferred embodiment of the invention can also be a combination of the dependent claims or above embodiments with the respective independent claim.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following drawings:

Fig. 1 shows schematically a block diagram of a system comprising a number of bi-directional OWC devices;

Fig. 2 shows schematically a block diagram of the transmit and reception signal path of a bi-directional OWC device;

Fig. 3 shows a table showing the state mapping of the USB 2.0 bus;

Fig. 4 shows a first detailed block diagram of the of a first transmit and first reception signal path of a first bi-directional OWC device;

Fig. 5 shows an example of transmitted optical output power of the OWC device of Fig. 4;

Fig. 6 shows a second detailed block diagram of the of a second transmit and second reception signal path of a second bi-directional OWC device;

Fig. 7 shows an example of transmitted optical output power of the OWC device of Fig. 6;

Fig. 8 shows a third detailed block diagram of the of a third transmit and third reception signal path of a third bi-directional OWC device;

Fig. 9A shows an example of transmitted optical output power of the OWC device of Fig. 8; Fig. 9B shows an example of transmitted USB output signal of the OWC device of Fig. 8;

Fig. 10 shows a schematic example of a user interacting with a mobile device;

Fig. 11 shows a fourth block diagram of a fourth transmit and fourth reception signal path of a fourth bi-directional OWC device;

Fig. 12 shows a fifth block diagram of a fifth transmit and fifth reception signal path of a fifth bi-directional OWC device; and

Fig. 13 shows a sixth block diagram of a sixth transmit and sixth reception signal path of a sixth bi-directional OWC device.

Reference Signs

100 OWC device

102 USB 2.0 capable controller

103 Combiner

104 Encoder

105 Decoder

106 Amplifier

107 Trans Impedance amplifier

108 Light source

109 Photodetector

110 Bandgap reference level generator

202 USB 2.0 capable controller

208 Light source

209 Photodetector

210 Bandgap reference level generator

211 Bias Control

212 Op. Amp

213 Trans Impedance Amplifier

214 Low pass filter

215,216,217 Comparators

218 Attenuator

219 AND gate

220 Detection block

221 PAM-3 decoder 240 Sample and Hold

302 USB 2.0 capable controller

303, 304 Inverting amplifier

305 AND gate

306, 308 Amplifier

312 Trans Impedance Amplifier

313 Low pass filter

314 NPN transistor

315,316 Comparator

317, 318, 319, 320 Switches

500 User’s eye

501 Mobile device

602 USB 2.0 capable controller

603 Combiner

604a, 604b Switch

605 USB capable connector

606 Output Amplifier

607 Input Amplifier

608 Light source

609 Photodetector

610 DC input power detector

611 Device processor

612 DC power detector

613 Data input signal detector

DETAILED DESCRIPTION OF EMBODIMENTS

In order for OWC/LiFi to be adopted in the consumer market as an alternative to RF wireless communication solutions, OWC technology will need to be integrated in user devices such as laptops, tablets, and smartphones. The USB 2.0 peripheral can be used as a direct interface for the generation of OWC output signals in such devices, as it is widely available in smartphones and tablets. However, the signals in USB need to be adapted to be able to be transmitted through an optical wireless channel. This invention describes a system for mapping USB 2.0 data signals for direct transmission through an optical wireless channel Fig. 1 presents an overview of a OWC solution that makes use of OWC transceivers integrated in consumer devices. Depicted in Fig. l is a use-case scenario for a handheld OWC device 100 used in a point-to-point communication setting. Here the handheld OWC device 100 may communicate with another OWC device 200 when the solid cone of their respective OWC transmitters mutually overlap the reception cones of the OWC receivers. When the handheld device 100 is re-directed, so that it’s transmit cone/reception aperture with those of the television device 300 it may alternatively set up a point-to point communication link with the television. Here the handheld OWC device and the television are mere examples and do not preclude application of the inventive concept in other contexts.

Handheld OWC devices, such as mobile phones or tablets are generally compact devices which for esthetical reasons as well as practical reason tend to have a small form factor, which in turn means a housing with limited space. Further design constraints for handheld OWC devices include amongst others the need for a low power consumption, so as to maximize battery life.

Given these constraints it may be advantageous to reuse hardware present already in existing devices when it is not being used. One of such devices may be the onboard USB peripheral device. USB ports (in any of its variants) are widely available on smartphones for charging and data transfer. As a result, peripheral USB devices currently are already present in mobile devices to support the USB port and most support USB version 2.0. The inventors observed that when the USB port is not connected for charging and/or wired USB communication, The USB peripheral device may be re-used for other purposes, such as Optical Wireless Communication.

Universal Serial Bus (USB) is an industry standard that establishes specifications for cables and connectors and protocols for connection, communication, and power supply (interfacing) between computers, peripherals and other computers. USB version 2.0 data communication makes use of differential signalling scheme over a twisted pair data cable. The differential lines designated as D+ and D- in the USB 2.0 interface can be used then to operate an OWC transmitter and receiver in a point-to-point communication.

However, the D+ and D- signals in the USB 2.0 physical layer are not “true” differential, as they have three different possible states, as also shown in the table in Fig. 3. Essentially there are four states: K, J, SEO and SEI. Here K and J are the two complementary differential states, and SEO has both lines driven low, which is used to indicate the end of packet. The fourth state SEI is defined as an invalid state and therefore should not be used. When used for OWC these signal states need to be adapted to map them to a scheme that is suitable for data transmission over the wireless optical channel. To this end we need to adapt or map the three possible levels on the USB 2.0 data lines to certain current/voltage that can be used for transmitting through a wireless optical channel by modulating a light source (LED/Laser) and receiving them by a photodiode.

Fig. 2 depicts an OWC device 100 for use in communication which comprises a USB 2.0 capable controller. The USB 2.0 capable controller may be for example a backwards compatible USB 3.0 controller. The USB 2.0 capable controller may be a standalone device but may also be integrated as a peripheral unit in a larger system on chip, or CPU. However, what is relevant is that the device is USB 2.0 capable. The USB 2.0 controller may be dedicated to optical wireless communication, but advantageously, may be shared for either wired USB communication and/or OWC.

The USB 2.0 interface is a bi-directional half-duplex system, that makes use of differential signalling over a pair of complementary transmission lines. On account of the bidirectional nature, a combiner is used to combine the OWC signals from the transmission path and reception path, while at the same time separating the optical transmission path from the optical reception path so as not to create a feedback loop. The combiner is connected to the USB 2.0 capable controller on the one hand and on the other hand to both an optical output path and an optical input path. The combiner is arranged to forward incoming signals from the USB 2.0 controller to the output path and to output signals received on the optical input path towards the USB 2.0 controller. As the USB 2.0 bus is bidirectional, the combiner is arranged to keep these signals separate, so as not to create a feedback loop between the optical input path and the optical output path. On account of the USB bus being a half-duplex system, signals received on the optical input path may be suppressed from entering the optical output path. Such could be implemented in various ways, ranging from applying a filter that supresses the received data from entering the output path, decoupling the output path when data is received, decoupling the amplifier input when data is received, or by other means.

The optical output path in turn comprises: an encoder 104 arranged to map the three valid logical USB differential signal levels onto respective levels of a three-level PAM data signal; a light source 108 for emitting a modulated light signal, arranged to be operated using a drive signal based on the three-level PAM data signal. Given that we will be using only a three-level PAM data signal, the invalid state SEI is preferably mapped onto the same PAM level as the SEO state, although as it is an invalid bus state; such should not occur and thus is not a requirement. When SEI is mapped to the same level as SEO, the invalid state will not masquerade as a data bit but will appear as an end of packet. The light source may comprise one or more LEDs and/or VCSELs, possibly fitted with suitable optics, such as lenses and/or collimators to achieve an output signal with sufficient width so as to be able to establish a reliable point-to-point connection. This output cone may e.g., be a solid angle of in the range of 30-10 degrees.

The optical input path on the other hand comprises a photodetector 109 arranged to receive light comprising data modulated as a three-level PAM data signal and generate a corresponding electrical signal. This signal may be generated by another OWC device 200, 300. The optical input path comprises a decoder 105 arranged to generate two USB 2.0 compatible differential signal levels based on the generated electrical signal. The photodetector here may be a photodiode, such as an avalanche photodiode or another suitable photodetector.

The combiner 103 in turn is arranged to receive the two input differential data signals from the USB 2.0 capable controller and route them to the encoder 104 and output two output differential data signals to the USB2.0 capable control based on the two USB 2.0 compatible differential signal levels from the decoder 105.

Typically, the optical output path will also include an amplifier 106 for generating a drive current for operating the light source 108 based on the output from the three-level PAM data signal. Likewise, typically the optical input path decoder further comprises a transimpedance amplifier 107 arranged to amplify the signal from the photodetector 109 prior to generating USB 2.0 compatible differential signal levels.

As mentioned before, the OWC device, may be portable or handheld portable devices. Also, preferably the optical wireless transmitters are emitting either infrared light and/or ultraviolet light.

A preferred implementation is presented in Fig. 4 which is using a mapping of the USB 2.0 valid states as presented in Fig. 5. This implementation performs a “Direct USB 2.0 transmission” by mapping the three valid states of the differentially coded data signal D+ and D- onto a three level PAM-3 signal. As can be seen in Fig. 5, this means that when the optical output path is operational light will be emitted in each of these states. However, for power savings reason, a user may off course disable the optical output path when no OWC is foreseen, alternatively the device may go into a power saving mode in the absence of data arriving at the optical output path for a certain period. Fig. 4 depicts a circuit diagram in which the three valid bus states created by the (D+, D-) USB signals generated by a USB controller 102 are mapped to an optical channel with three levels. The transmitter is composed of two comparators 119, 120, one per differential line, with a reference 110 for the threshold level of the positive signal, which is then applied to a differential amplifier to drive the light source differentially (AC-coupled). This generates an optical signal in which the SEO USB state is transmitted as the bias level (produced by a bias controller 111), and the K-J states are sent as a level above or below this level, as it is shown in the diagram of transmitted optical power vs time. On the receiver side, the signals are picked up by the photo detector 109 and amplified by the Transimpedance Amplifier 113. By means of two comparators 116, 117 and low pass filters 114, 115 the signals are translated back to the required levels needed for the D+ and D- lines, here the low-pass filters are configured to filter signals corresponding with the USB data and pass the DC level. An attenuator is added 118 so that the signal levels are slightly below the bandgap reference levels 110, but still above the minimum necessary for the USB controller to detect them. This way we avoid that the received signal is retransmitted again, creating a loop. This receiver implementation forms a PAM-3 Decoder 119.

A further preferred implementation is presented in Fig. 6 which is using a mapping of the USB 2.0 valid states as presented in Fig. 7. This implementation again performs a “Direct USB 2.0 transmission” by mapping the three valid states of the differentially coded data signal D+ and D- onto a three level PAM-3 signal. As can be seen in Fig. 7, in the logical USB bus state SEO no light is emitted, as a result this implementation may be more power efficient than the circuit of Fig. 4.

The circuit in Fig. 6, thus provides a possible power reduction at the expense of receiver complexity. Starting with the optical output path, the logical USB SEO state is represented as a zero (light source fully off), the K state as a level above the bias, and the J state as the bias level. To achieve this, the transmitter schematic is similar to the previous implementation, with the addition of a detection block 220 that enables the bias when any of the D+/D- signals is above the reference level. For the optical input path, three comparators are needed 215, 216, 217, together with sample-and-hold 240 and low-pass filter circuitry 214 configured to filter signals corresponding with the USB data. This will create a low- frequency and a high-frequency path. The low-frequency path will measure the average value, which will act as a threshold for the comparators to detect when either logic USB J-K states or SEO state is being received. The high-frequency path will assign the values for the J- K states for each of the (D+, D-) lines. In addition to the added complexity, adjustments of levels, sample-and-hold, and filters can be more complex than for the previous solution.

Yet a further implementation is presented with reference to Fig. 8 and 9A and 9B. This implementation again performs a “Direct USB 2.0 transmission” by mapping the three valid states of the differentially coded data signal D+ and D- onto a three level PAM-3 signal. Figures 9 A and 9B show the mapping of the differential input pair D- and D+ onto the corresponding optical transmit power output profile.

The implementation shown in Fig. 8 represents a simpler design, in which the USB logical states K-J are mapped to optical amplitude values (0, a), while the SEO state is mapped onto an output value of 2a. The optical output path further comprises two different amplifiers or current sources 305, 306, one of them producing double the current, that together with two inverting amplifiers 303, 304 and an AND 305 will create the different optical outputs. For the optical input path, as with the previous approach, a low-pass filter 303 will measure the average value of the received signal, which will serve to set up different threshold values for the J-K states or the SEO states for the comparators 315, 316. The output of one of the comparators 315 will act as a trigger for different switches 317, 318, 319, 320 that will reconstruct the three states necessary for the D+, D- USB lines.

OWC devices as described herein may be (handheld) OWC devices that use dedicated USB 2.0 capable controllers for generating USB 2.0 data signals for optical wireless communication. However, when such USB 2.0 capable controller is not dedicated to the OWC function, but may be additionally used, in a time-multiplexed manner, for legacy wired USB 2.0 functions, it may be beneficial to provide for an automatic switching between these two modes of operation. By doing so the implementation presented herein below allows for dynamic switching, which precludes loss of the legacy wired USB 2.0 functionality.

Switching between both OWC operation and legacy USB data/charging operation makes sense as a user is less likely to use OWC when the device is plugged-in for charging or wired data communication to a computer. More optionally a user override function may be provided to overrule the automatic switching, so as to switch from IO device even when connected to a USB cable. Fig. 11 shows an OWC device, that implements automatic switching, the OWC device USB 2.0 shown comprises a USB 2.0 to optical wireless interface integrated therein. The optical output path of the OWC device here comprises an amplifier 606 and a light source (e.g. LED or VCSEL laser) 608. The optical input path shown comprises a photodetector 609 and a Trans Impedance Amplifier 107. The combiner 603 may be implemented similar to the earlier implementations discussed herein above, wherein the USB 2.0 differential signal levels are mapped onto a 3-level PAM signal or, may alternatively be implemented by means of a combiner 603, which is not limited to the 3-level PAM signal mapping, but may also employ other signal encoding schemes. For example the combiner may employ a 4-level PAM signal, thereby facilitating the level encoding, or may alternatively use a parallel to serial conversion step whereby a single USB 2.0 state is mapped onto two successive 2-level PAM pulses of half the duration of a USB 2.0 bus symbol.

In this implementation, by default, when the user is normally operating the handheld device (i.e., when the device is not plugged-in to a USB host or charging port), the switches 604a, 604b placed in the D+, D- lines are connected directly to the combiner 603. When a USB cable is plugged-in into the USB connector 605, a detector 610 sniffing the USB supply lines on the USB connector can be used to control the switches 604a and 604b and connect the differential USB port of the USB 2.0 capable controller 602, D+, D-, to the USB connector 605 instead of to the combiner603, therefore being able to use the device for charging and/or wired data transfer.

Different implementations of the combiner 603 are foreseen; in a first implementation the combiner 603 may be implemented as a USB device or “Media Converter”. When the switches are connected to such a Media Converter 603, the Media Converter 603 acts as a USB device towards the USB controller 602, which in turn acts as the USB host. In this manner, the Media Converter 603 performs all USB negotiation, including cable termination.

Alternatively, the combiner 603 may be implemented as a pass-through device, essentially implementing an optical wireless replacement for a USB cable, in which case it is referred to as an encoder/decoder 603, the encoder/decoder 603 will handle cable termination emulation and USB state level conversion, in a way that allows the USB Controller 602 to act as a USB host towards a remote end-point 200 or 300 acting as a USB Device.

Fig. 12 shows an OWC device that is arranged to switch the USB peripheral data line independence of the incoming OWC signal. Here the presence of the incoming OWC signal is used to configure the switching arrangement, such that when DC power detection 612 detects a DC signal, or in more advanced embodiments, detects an optically encoded USB signal, the switch arrangement connects the differential data bus D-, D+ of the USB 2.0 capable controller 602 with the combiner 603. In this manner it is possible to give priority to an optical wireless connection. In the implementation shown, the presence of a DC signal in the light impinging on the photodetector 609 is used. In the depicted implementation it is directly tapped from the photodetector 609 and routed to the input amplifier 607 (here a Trans Impedance Amplifier) and a DC power detection unit 612, which in turn controls the switches 204a, 204b of the switch arrangement. When the photodetector 209 detects impinging light from a remote OWC transmitter, the detection switches the switch arrangement to the position or state wherein the combiner 603 is connected to the USB 2.0 capable controller 602.

If on the other hand the DC power detection 612 does not register a DC component, then preferably the switch arrangement defaults to connect the differential data signal of the USB 2.0 capable controller 602 to the USB connector 605.

As only the USB differential data signals need switching, it is still possible to use the USB power lines, if power is present thereon, even when transmitting or receiving using the optical path. Instead of detecting the presence of a DC component in the optical signal, it may alternatively be possible to detect the presence of a modulation in the output of the input amplifier 607. The advantage of doing so is that it does not introduce noise in the photodetector output.

Fig. 13 shows an OWC device that is arranged to switch the USB peripheral data line independence of the USB data signal received over the USB connector 605. In the implementation depicted here, a data input signal detector 613 sniffs the differential USB data input pair D-, D+ coming from the USB connector 605.

In this implementation, the switches of the switch arrangement may by default be connect the USB 2.0 capable controller 602 with the combiner 603 for optical communication. If an external device is connected to the OWC device by means of the USB connector 605, the power line, when power is present, may be used for charging, but the switches of the data arrangement will only be connected to the USB connector 605 if data traffic is detected on the D-, D+ lines. A timeout period can be deployed, such that the signal detector 613 after a predetermined period without traffic over the USB data lines controls the switch arrangement to again revert to the default position whereby OWC is enabled.

Eye safety feature for a mobile optical wireless communication device.

In the process of working with mobile handheld OWC devices, the inventors observed that eye safety is an important topic, as the power of the light source used can be damaging to the human eye at short distances. In the process, methods and devices and were devised for implementing an eye safety feature for handheld and/or mobile Optical Wireless Communication (OWC) devices. The eye safety feature is particularly relevant for portable and/or portable handheld OWC devices 100 and 200 as shown in Fig. 1.

As a smartphone is a highly compact devices with limited space, it is further useful to reuse the sensors and peripherals that are commonly already present in such devices also for eye safety purposes. Due to the high-power light output of light sources used for communication OWC (e.g., LED and Lasers) it is important to prevent exposure to high power light output, the latter is particularly true when the output is outside of the visible spectrum, such as is the case for infrared and/or UV light. Here to ensure eye-safety a mechanism needs to be implemented to disable the light source when the user could be looking at it, in particular at a close distance as there the optical power level of the impinging light will be higher.

Different approaches are described herein below that aim to leverage hardware and processing capability present in some handheld devices in a novel manner. When the described hardware is not yet present in such mobile OWC devices, suitable hardware as described herein below may be added to the OWC device, be alternatively added to the device.

With reference to Fig. 10, an optical handheld device (e.g. mobile phone or tablet) is provided which comprises one or more of the following: i) a time-of-flight (ToF) module for 3D face scanning, ii) a microphone and speaker pair capable of emitting and sensing in the ultrasound frequency range for use in distance sensing and iii) an integrated OWC transceiver, comprising an optical output path and optical input path, wherein the optical output path comprises a light source arranged to emit a modulated light output signal comprising embedded data and a light source driver arranged to drive the light source using a drive signal comprising the embedded data. And wherein the optical input path comprises a input path including a photodetector and accompanying optics (which may e.g. included fixed or switchable lenses, and/or collimators) arranged to direct light impinging on the OWC device surface towards the photodetector. Preferably both the optical output path and the optical input path are fully comprised within the housing of the OWC device and the input and/or output are passed through respective (or combined) ingress/egress openings, or more preferably windows on the device housing allowing the relevant light to ingress/egress.

A user operating a mobile OWC device can be at risk of eye damage, for example when looking directly at the OWC device facing the OWC emitter (Fig. 10) and the distance between the OWC device 501 and the eyes of the user 500 is below the minimum allowable distance defined for the specific power and characteristic of the light source used in the OWC device. This can also occur when the user brings the phone close to its ear to make a phone call, and the rotation of the phone in the hand can direct the light output from the light source in such a manner that it impinges on the eyes of the user.

To avoid this problem, the presence of the head (and therefore implicitly the eyes) of the user may be detected. When the device is within range where it is deemed unsafe, the light source (or the entire optical output path of the OWC device) will be disabled until the distance is confirmed to be safe such that it can be enabled again.

Three distinct approaches may be used, alternatively or optionally in combination with one or more of the others. Using multiple independent modalities, a more robust system may be obtained. To this end the output of the respective modalities should be combined in such a way that the light source output is switched off whenever any one of the modalities signals a potential risk.

A first approach to determine whether a user is in close proximity to the mobile device and subsequently inhibit the light source output is to use a Time-of-Flight measurement using the OWC device’s integrated 3D face scan sensor. A Time-of-Flight sensor, such as used for unlocking smartphones, uses a Time-of-Flight sensor for facial recognition purposes. Here the face scan sensor determines a depth measurement which apart from the relative distance of facial features also provide distance information of the face scan sensor to the OWC device. When the thus determined distance to an object is below a minimal safe distance plus a safety margin, or alternatively, when it drops below the minimal safe distance, the light source is switched off.

A second approach is one wherein a Time-of-Flight measurement is performed using the OWC transceiver. An OWC transceiver integrated in the OWC device may be used to perform a Time-of-Flight measurement using a time-of-flight measurement by means of transmission of short burst pulses of light and subsequent measurement of the round-trip time using the on-board photodetector. The respective burst of light from the light source will when an object, such as the face of the user, comes into proximity of the OWC device, reflect on the object surface. The time deviation between the signal emitted by the light source and the subsequent reception thereof by the photodetector, is representative of twice the distance between the two. After removing the delay resulting from the response time of the light source and photodetector, which may be measured prior to operation during calibration, the response time may be used for a distance determination based on the speed of light. When the thus determined distance to an object is below a minimal safe distance plus a safety margin, or alternatively, when it drops below the minimal safe distance, the light source is switched off

A third approach is one wherein the integrated microphone and speaker of an OWC device may be used for ultrasound ranging. To accomplish this OWC device speaker and microphone need to be able to both emit and sense ultrasound signals above the 20 kHz range. The underlying principle here is similar to that of the second approach above. Here the speaker emits ultrasound pulses which in turn are picked up using the microphone. The time deviation between the signal emitted by the speaker and the subsequent reception thereof by the microphone, is representative of twice the distance between the two. After removing the delay resulting from the response time of the speaker and the microphone, the time difference may be used for a distance determination based on the speed of sound. When the thus determined distance to an object is below a minimal safe distance plus a safety margin, or alternatively, when it drops below the minimal safe distance, the light source is switched off.

All three approaches essentially determine the distance of objects to an OWC device using a round trip time to inhibit light source output.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The foregoing description details certain embodiments of the invention. It will be appreciated, however, that no matter how detailed the foregoing appears in the text, the invention may be practiced in many ways, and is therefore not limited to the embodiments disclosed. It should be noted that the use of particular terminology when describing certain features or aspects of the invention should not be taken to imply that the terminology is being re-defined herein to be restricted to include any specific characteristics of the features or aspects of the invention with which that terminology is associated.

A single unit or device may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Some of the described operations herein above, in particular the control operation, can be implemented partially as program code means of a computer program and/or as dedicated hardware of the OWC devices. The computer program in turn may be stored and/or distributed on a suitable medium, such as an optical storage medium or a solid- state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Claims

24 CLAIMS:

1. An optical wireless communication, OWC, device (100,200) comprising: a USB 2.0 capable controller (602) having a USB bus; a USB connector (605) on the OWC device exterior, a combiner (603) connectable to the USB bus and connected to an optical output path and an optical input path; the optical output path comprising: an output amplifier (606) arranged to receive an output signal from the combiner (603) and generate an output signal for use in driving a light source (608); the light source (608) arranged to receive the drive signal from the combiner and emit a modulated light signal; the optical input path comprising: a photodetector (609) arranged to receive an OWC signal comprising data modulated therein and generate a corresponding electrical input signal; an input amplifier (607) arranged to amplify the electrical input signal and output the amplified signal to the combiner, and a switching arrangement arranged to:

- in a first mode connect the differential USB data pair (D-, D+) from the USB 2.0 capable controller to the combiner (603) and

- in a second mode connect the differential USB data pair (D-, D+) from the USB 2.0 capable controller to the USB connector (605); the switch arrangement operable to switch between modes independence of: the incoming OWC signal or signals on the USB connector (605).

2. The OWC device (100,200) according to claim 1, further comprising a DC power detector (612) arranged to detect a DC component in the output of the photodetector (609) and wherein the switching arrangement is arranged to operate in the first mode when a DC power level is detected above a DC threshold.

3. The OWC device (100,200) according to claim 1, further comprising a USB modulation detector arranged to detect a USB modulation signal in the output of the input amplifier (607) and wherein the switching arrangement is arranged to operate in the first mode when a USB modulation signal is detected exceeding a predetermined threshold level by the USB modulation detector.

4. The OWC device (100,200) according to claim 1, further comprising a data input signal detector (613) arranged to detect a USB modulation signal on the data lines of the USB connector (605) and wherein the switching arrangement is arranged to operate in the second mode when a USB modulation signal is detected exceeding a predetermined threshold level by the data input signal detector (613).

5. The OWC device (100,200) according to claim 1, further comprising a DC input power detector (610) arranged to detect a DC power on the USB power lines of the USB connector (605) and wherein the switching arrangement is arranged to operate in the second mode when a USB input power signal is detected exceeding a predetermined threshold level by the DC input signal detector (610).

6. The OWC device (100,200) according to any preceding claim, wherein the input amplifier (607) is a transimpedance amplifier.

7. The OWC device (100,200) according to any preceding claim, wherein the OWC device is a portable or handheld portable device.

8. The OWC device (100,200) according to any preceding claim, wherein the light source (608) is and infrared or ultraviolet light source, preferably selected from the set of an LED light source, a laser diode, or a vertical cavity surface emitting laser, VCSEL, light source.

9. The OWC device (100,200) according to any preceding claim, wherein the photodetector is one of: a photodiode, a phototransistor, an avalanche photo diode and a silicon photon multiplier.

10. The OWC device (100,200) according to any preceding claim, further comprising a user input interface, wherein the user interface allows a user to overrule the default switch arrangement setting.

11. The OWC device (100,200) according to any preceding claim, further comprising a battery wherein the OWC device is arranged to charge the battery power is available on the USB connector (605), regardless of the switch arrangement setting.

12. The OWC device (100,200) according to any preceding claim, wherein the combiner (603) further comprises an encoder and a decoder, wherein the encoder is arranged to map each of the J, K, SEO USB 2.0 bus states of the combiner (603) input from the USB 2.0 capable controller (605) onto one of three distinct optical output symbol for output by means of the optical output path and the decoder is arranged to map each one of three distinct optical output symbols of the combiner (603) input from the optical input path onto one of the J, K, SEO USB 2.0 bus states for output by the combiner (603) to the USB 2.0 capable controller (605) and wherein the mapping by the encoder and the mapping by the decoder are one another’ s inverse.

13. The OWC device (100,200) according to any preceding claim, wherein the combiner (603) further comprises an encoder and a decoder, wherein the encoder is arranged to map each of the J, K, SEO USB 2.0 bus states of the combiner (603) input from the USB capable controller (605) onto one of three distinct PAM- 3 levels for output by means of the optical output path and the decoder is arranged to map each of three distinct PAM-3 levels of the combiner (603) input from the optical input path onto one of the J, K, SEO USB 2.0 bus states for output by the combiner (603) to the USB capable controller (605) and wherein the mapping by the encoder and the mapping by the decoder are one another’s inverse. 27

14. The OWC device (100,200) according to any preceding claim, wherein the combiner (603) further comprises an encoder and a decoder, wherein the encoder is arranged to map each of the four USB 2.0 bus states of the combiner (603) input from the USB 2.0 capable controller (605) onto one of four distinct PAM-4 levels and the decoder is arranged to map each of four PAM-4 symbols of the combiner (603) input from the optical input path onto one of the four USB 2.0 bus states for output by the combiner (603) to the USB 2.0 capable controller (605) and wherein the mapping by the encoder and the mapping by the decoder are one another’s inverse.

15. The OWC device (100,200) according to any preceding claim, wherein the combiner 603 further comprises an encoder and a decoder, wherein the encoder is arranged to map each of the four USB 2.0 bus states of the combiner (603) input from the USB 2.0 capable controller (605) onto combinations of two successive PAM-2 symbols, each PAM-2 symbol having half a period of a USB bus symbol and the decoder is arranged to map each combination of two successive PAM-2 symbols, each PAM-2 symbol having half a period of a USB bus symbol of the combiner (603) input from the optical input path onto one of the four USB 2.0 bus states for output by the combiner (603) to the USB 2.0 capable controller (605) and wherein the mapping by the encoder and the mapping by the decoder are one another’s inverse.