WIRELESS OPTICAL COMMUNICATION DEVICE

Description

[0001] The invention relates to the field of wireless optical communication. BACKGROUND OF THE INVENTION

[0002] Today we are witnessing a significant deployment of optical wireless communication (OWC) technology. Optical Wireless Communication ) .

[0003] An example of a bidirectional application implementing this technology is as follows.

[0004] LiFi is a subset of OWC technology that allows access to a wireless network (e.g., the Internet) using light. A LiFi access point (for Light Fidelity ) is positioned on the ceiling of a room. The LiFi access point is connected by optical fiber or by an electrical cable to a local or public network such as the Internet. The electrical cable is for example an Ethernet cable. The LiFi access point is possibly powered via the Ethernet cable (this is called PoE, for Power over Ethernet ).

[0005] A computer (or other compatible equipment: smartphone, tablet, etc.) is located in the room. A dongle LiFi is connected to the computer (the term dongle is sometimes replaced in French by the term "sentinel"). The computer and the dongle LiFi are positioned within the coverage area of ​​the LiFi access point, so that communication is established between the LiFi access point and the dongle LiFi. The computer is thus connected to a network via the dongle LiFi and LiFi access point.

[0006] Computer networking using wireless optical communication technology has many advantages over traditional radio frequency communications. These include high throughput and low latency, bandwidth availability, reduced risks from electromagnetic waves, reduced risks of hacking, etc.

[0007] To improve the range and quality of wireless optical communication, it is envisaged to increase the light intensity (e.g. infrared) produced by the Li-Fi access point and by the dongle Li-Fi.

[0008] Increasing light intensity, however, raises two problems.

[0009] A first problem concerns the electrical consumption of the dongle Li-Fi, which must remain as low as possible. It is advisable to respect at least the power supply capacities of the connection standard used, for example USB2.0. If the current drawn or the voltage required are too high, the dongle Li-Fi cannot be connected to the computer. It is also desirable to reduce as much as possible the consumption by the dongle LiFi from the energy stored in the computer battery. It is also preferable to limit the heating of the dongle LiFi.

[0010] A second issue concerns the eye safety of users. It is essential, despite the increase in light intensity, that the user's eyes are protected even if they bring their face close to the Li-Fi access point or the dongle LiFi. State-of-the-art document WO 2018 / 086842 describes a Li-Fi access point with a switch to enable the measurement of a diode voltage at regular intervals. SUBJECT OF THE INVENTION

[0011] The object of the invention is to limit the electrical consumption of a wireless optical communication device and to ensure eye protection for users. SUMMARY OF THE INVENTION

[0012] To achieve this goal, an access point is provided comprising a wireless optical communication device comprising: a processing component arranged to produce emitted digital signals during emission periods; a digital-to-analog converter arranged to produce emitted analog signals from the emitted digital signals; a light source arranged to produce emitted light signals from the emitted analog signals; a cut-off circuit arranged to selectively activate or deactivate the light source; the processing component comprising a binary output and being arranged to produce and apply to the binary output a binary control signal which is in a first state during the emission periods and in a second state outside the emission periods, the cut-off circuit being arranged to acquire the binary control signal, and to activate the light source when the binary control signal is in the first state and to deactivate the light source when the binary control signal is in the second state.The processing component is further arranged to emit, during search cycles, transmitted digital signals containing search frames for devices likely to be connected to the access point, and in that each search cycle comprises at least one transmission period and at least one silence period, a sum of the silence periods being at least 10 times longer than a sum of the transmission periods, such that during a search cycle, the binary control signal is in the first state for a first duration at least 10 times shorter than a second duration during which the binary control signal is in the second state.

[0013] The cut-off circuit, controlled by the binary control signal, makes it possible to deactivate the light source (i.e. to turn it off) outside of transmission periods, so that it only consumes electrical energy when the wireless optical communication device according to the invention must transmit transmitted digital signals. This significantly reduces the power consumption of the wireless optical communication device.

[0014] When an obstacle, for example a user's face, is near the wireless optical communication device, this obstacle cuts off the communication which, classically, in the case of a dongle, prevents it from emitting transmitted digital signals and, in the case of an access point, prevents it from emitting transmitted digital signals except for device search frames which include short, spaced pulses. In both cases, the user's eye safety is not threatened.

[0015] Further provided is a communication device such as that just described, in which the processing component is a baseband modem.

[0016] A communication device such as that just described is also proposed, in which the baseband modem is an integrated circuit designed to comply with the standard G.hn (ITU G.9960 / ITU G.9961 / ITU G.9963 / ITU G.9964).

[0017] We further propose a communication device such as that just described, in which the binary output is a GPO type output ( General Purpose Output ).

[0018] We further propose a communication device such as that which has just been described, in which the cut-off circuit comprises a transistor forming a switch controlled by the binary control signal, and in which the light source comprises a terminal connected to a source of a bias voltage and a terminal connected to an electrical ground via the transistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Reference will be made to the attached drawings, including: [ Fig. 1 ] there figure 1 represents a LiFi access point and a dongle LiFi which each integrate a wireless optical communication device according to the invention; [ Fig. 2 ] there figure 2 represents the architecture of the Li-Fi access point; [ Fig. 3 ] there figure 3 is a perspective and bottom view of the Li-Fi access point; [ Fig. 4 ] there figure 4 represents the architecture of the dongle LiFi; [ Fig. 5 ] there figure 5 is a perspective and top view of the dongle Li-Fi connected to a computer; [ Fig. 6 ] there figure 6 represents a binary control signal associated with the transmission of data frames; [ Fig. 7 ] there figure 7 represents a cut-off circuit of the wireless optical communication device according to the invention; [ Fig. 8 ] there figure 8 represents a binary control signal associated with the transmission of device search frames. DETAILED DESCRIPTION OF THE INVENTION

[0020] In reference to the figure 1 , a LiFi access point 1, integrating a wireless optical communication device according to the invention, and a dongle LiFi 2, also integrating a wireless optical communication device according to the invention, are located in a room of a dwelling in a building.

[0021] The LiFi 1 access point is fixed to the ceiling of the room by a mechanism similar to a smoke detector mounting mechanism, or directly by flush mounting. The LiFi 1 access point is connected to a PoE 3 network (for Power over Ethernet ) of the building via an RJ45 cable 4. The PoE 3 network also powers a telephone fitted in the home.

[0022] THE dongle LiFi 2 is connected to a computer 5 via USB (A or C). Computer 5 and the dongle LiFi 2 are positioned under the emission cone 6 of the LiFi access point 1, so that communication is established between the LiFi access point 1 and the dongle LiFi 2. Computer 5 is thus connected to a network via the dongle LiFi 2 and LiFi 1 access point.

[0023] In reference to the figures 2 And 3 , the LiFi access point 1 comprises a housing 8 in which the first components are integrated.

[0024] The first components include first of all a female RJ45 connector 9 allowing the connection of the LiFi access point 1 to the RJ45 cable 4.

[0025] The first components further comprise a PoE 10 splitter. The PoE 10 splitter acquires incoming signals containing incoming digital signals, which are Ethernet signals, combined with a primary DC supply voltage (here equal to 5V), and separates the incoming digital signals and the primary DC supply voltage.

[0026] The first components also include a DC-DC converter 11. The primary DC supply voltage is transformed by the DC-DC converter 11 into a secondary DC supply voltage used to power the first components of the LiFi access point 1.

[0027] Note that the female RJ45 connector 9, the PoE splitter 10 and the DC-DC converter 11 form a single data and power interface allowing the LiFi access point 1 to be connected in " Plug and Play » on the PoE 3 network.

[0028] The first components further comprise an Ethernet transceiver 12 and a processing component, which in this case is a baseband modem 14.

[0029] The Ethernet transceiver 12 acquires incoming digital signals and formats them to make them compatible with a format accepted by the baseband modem 14. Similarly, the Ethernet transceiver 12 acquires outgoing digital signals produced by the baseband modem 14 and transforms them to make them compatible with the Ethernet protocol.

[0030] The 14 baseband modem here is an off-the-shelf (COTS) integrated circuit. Component Off-The-Shelf ) and originally designed to comply with the G.hn telecommunications standard (ITU G.9960 / ITU G.9961 / ITU G.9963 / ITU G.9964). The baseband modem 14 integrates a digital-to-analog converter 15 and an analog-to-digital converter 16.

[0031] The baseband modem 14 generates transmitted digital signals which are applied to the input of the digital-to-analog converter 15, which converts them into transmitted analog signals applied to an output of the baseband modem 14. Similarly, the baseband modem 14 receives received analog signals which are applied to an input of the analog-to-digital converter 16. The analog-to-digital converter 16 converts the received analog signals into received digital signals.

[0032] The first components also include a memory flash 17 to store and load the various software programmed into the baseband modem 14.

[0033] The first components further comprise a transmission path 20 and a reception path 21.

[0034] The transmission path 20 comprises a first amplification stage 22, a second amplification stage 23, a light source 24 and a cut-off circuit 25.

[0035] The first amplification stage 22 has an adaptive gain, which is adjusted according to the light source 24.

[0036] The second amplification stage 23 comprises an amplifier for increasing the power of the transmitted analog signals. The amplifier is, for example, a class A amplifier, or a driver line. The second amplification stage 23 further comprises a pre-equalization module comprising for example an RC or RLC network.

[0037] The light source 24 here comprises an infrared light-emitting diode (IR LED 24).

[0038] The reception path 21 comprises a photoreceiver 27, a concentrator 28, a voltage adjustment module 29, a first amplification stage 30 and a second amplification stage 31.

[0039] The photoreceiver 27 here comprises a PIN photodiode 27 which performs an optoelectronic conversion. The PIN photodiode 27 is biased by the voltage adjustment module 29 to increase the bandwidth.

[0040] The concentrator 28 is mounted on the PIN photodiode 27 and makes it possible to increase the collected optical flow and the reception coverage of the LiFi access point 1.

[0041] The first amplification stage 30 comprises a pre-amplification module comprising a peak amplifier to increase the bandwidth.

[0042] It is noted here that, in the case where one would use not one but several PIN photodiodes connected in parallel, one could plan to use a single pre-amplification module connected to the PIN photodiodes. One could also plan to use a pre-amplification module per PIN photodiode, then to sum the resulting received analog signals, which makes it possible to increase the sensitive surface.

[0043] The second amplification stage 31 has a variable gain depending on the channel state. The variable gain is controlled by the baseband modem 14.

[0044] The first amplification stage 22 of the transmission channel 20 and the second amplification stage 31 of the reception channel 21 are integrated in the same component 33 which is an analog front-end circuit. The component 33 is here an off-the-shelf component.

[0045] In reference to the figures 4 And 5 , the architecture of the dongle LiFi 2 is very close to that of LiFi 1 access point.

[0046] THE dongle LiFi 2 comprises a housing 108 in which second components are integrated.

[0047] The second components thus comprise a DC-DC converter 111, an Ethernet transceiver 112, a baseband modem 114 comprising a digital-to-analog converter 115 and an analog-to-digital converter 116, and a first memory flash 117.

[0048] The second components further comprise a transmission path 120 and a reception path 121.

[0049] The transmission path 120 comprises a first amplification stage 122, a second amplification stage 123, an IR LED 124 and a cut-off circuit 125.

[0050] The reception channel 121 comprises a PIN photodiode 127, a concentrator 128, a voltage adjustment module 129, a first amplification stage 130 and a second amplification stage 131. The first amplification stage 122 of the transmission channel 120 and the second amplification stage 131 of the reception channel 121 are integrated in the same component 133 which is an off-the-shelf component.

[0051] The second components of the dongle The LiFi 2 components just mentioned are similar to the first equivalent components of the LiFi 1 access point, and operate in much the same way.

[0052] THE dongle LiFi 2 differs mainly from LiFi 1 access point in hardware (hardware) in that it comprises, instead of the female RJ45 connector 9 and the PoE splitter 10, a USB port 109, in this case a female USB-C port, a LAN component 110 (for Local Area Network ) and a second memory flash 113.

[0053] THE dongle LiFi 2 receives a 5V DC supply voltage and incoming digital signals from the computer 5 via the USB port 109, and outputs outgoing digital signals.

[0054] The second flash memory 113 is powered by the DC-DC converter 111 and is connected to the LAN component 110 and to the Ethernet transceiver 112.

[0055] The USB port 109 and the LAN component 110 allow you to connect the dongle LiFi 2 in « Plug and Play » on a device with a USB A or C port, such as the computer 5.

[0056] The role of the cut-off circuit 25 in the LiFi access point 1 is now described in more detail. The role of the cut-off circuit 125 in the dongle Li-Fi 2 is not described because it is identical.

[0057] The baseband modem 14 produces transmitted digital signals containing signal frames (including data frames) that the LiFi access point 1 sends to the dongle LiFi 2.

[0058] The digital-to-analog converter 15 of the baseband modem 14 produces transmitted analog signals from the transmitted digital signals.

[0059] The transmitted analog signals are shaped by the first amplification stage 22 and by the second amplification stage 23 of the transmission path 20, then are transmitted to the IR LED 24 which produces transmitted light signals comprising the signal frames.

[0060] The 14 baseband modem has a GPO_A output (GPO for General Purpose Output ) 40 which is a binary output (just like the baseband modem 114 which has a GPO_A output 140).

[0061] In reference to the figure 6 , the baseband modem 14 produces and applies to the output GPO_A 40 a binary control signal Sbc which is in a first state during the transmission periods Pe by the baseband modem 14 of digital signals transmitted, and in a second state outside the transmission periods of the digital signals transmitted.

[0062] Here, the first state is a high state and the second state is a low state.

[0063] The GPO_A 40 output makes it possible to simply distinguish between the emission periods during which the IR LED 24 is supposed to emit emitted light signals containing the signal frames, and the periods during which the IR LED 24 is not supposed to emit such emitted light signals.

[0064] Note that this configuration of the GPO_A 40 output is programmed "as standard", by default, in the baseband modem 14 which, remember, is a component taken off the shelf.

[0065] In reference to the figure 7 , the detection circuit 25 is connected to the IR LED 24.

[0066] The detection circuit 25 comprises an inductor 50, a capacitor 51, an N-type MOSFET transistor 52, a first resistor 53 and a second resistor 54.

[0067] The inductor 50 is connected between a source of a bias voltage V_LED of the IR LED 24 and an anode of the IR LED 24. The capacitor 51 has a terminal connected to the anode of the IR LED 24. The emitted analog signals Sae are applied to the terminal of the capacitor 51 which is not connected to the anode of the IR LED 24. The cathode of the IR LED 24 is connected to the electrical ground 56 via the transistor 52. More precisely, the cathode of the IR LED 24 is connected to the drain D of the transistor 52 and the electrical ground 56 to the source S of the transistor 52.

[0068] Inductance 50 prevents the emitted analog signals Sae from going back to the source of the bias voltage V_LED.

[0069] The first resistor 53 is a gate resistor of the transistor 52, and has one terminal connected to the gate G of the transistor 52. The binary control signal Sbc is applied to the other terminal of the first resistor 53. The second resistor 54 has one terminal connected to the gate G of the transistor 52 and one terminal connected to the electrical ground 56. The second resistor 54 ... pull-down which makes it possible to avoid intermediate voltage states on the gate G of transistor 52.

[0070] The cut-off circuit 25 makes it possible to activate (i.e., to turn on) the IR LED 24 during transmission periods, and to deactivate (i.e., to turn off) the IR LED 24 outside of transmission periods.

[0071] It is first assumed that the GPO_A output 40 of the baseband modem 14 is not used and that the lower part of the cut-off circuit 25 is not mounted: the cathode of the IR LED 24 is then connected directly to the electrical ground 56. In this case, if an emitted analog signal Sae is applied to the capacitor 51, this is added to the bias voltage V_LED of the IR LED 24. The IR LED 24 therefore transmits emitted light signals corresponding to this sum of electrical signals. In the case where no emitted analog signal Sae is applied to the capacitor 51, the IR LED 24 nevertheless emits a constant emitted light signal, not containing signal frames, corresponding to the bias voltage V_LED of the IR LED 24. The IR LED 24 is therefore constantly powered and thus consumes energy continuously.

[0072] When the cut-off circuit 25 is used, on the contrary, the IR LED 24 is activated during the emission periods and cut off outside the emission periods thanks to the binary control signal Sbc which controls the transistor 52 which behaves like a switch.

[0073] When the binary control signal Sbc is in the first state, that is to say in the high state, this high state is applied to the gate G of the transistor 52 which then operates in saturated mode, which allows the creation of a conduction channel between the drain D and the source S of the transistor 52. The cathode of the IR LED 24 is then connected to the electrical ground 56, which allows it to be powered by the sum of the DC bias voltage V_LED and the emitted analog signals Sae.

[0074] On the contrary, when the binary control signal Sbc is in the second state, that is to say in the low state (outside of emission periods), this low state is applied to the gate G of the transistor 52 which is in a blocked mode. The cathode of the IR LED 24 is not connected to the electrical ground 56, so that the IR LED 24 is not powered by any signal.

[0075] The IR LED 24 therefore consumes electrical energy only when it emits transmitted light signals containing signal frames, i.e. when the LiFi access point 1 transmits the signal frames.

[0076] The cut-off circuit 25 and the cut-off circuit 125 therefore make it possible to significantly reduce the power consumption of the LiFi access point 1 and the dongle LiFi 2.

[0077] The cut-off circuit also helps ensure user eye safety. The cut-off circuit protects a user's eyes when they bring their face close to the LiFi 1 access point or the dongle LiFi 2.

[0078] Generally, if an obstacle appears between the LiFi 1 access point and the dongle LiFi 2, then the communication is broken. The reestablishment of the communication can only be done at the initiative of the LiFi access point 1, via the emission during search cycles, by the baseband modem 14, of transmitted digital signals containing search frames for devices likely to be connected to the LiFi access point 1. The transmitted digital signals comprising the search frames for devices are transformed into transmitted analog signals and then into transmitted light signals.

[0079] If these emitted light signals are received by a device, for example by the LiFi 2 dongle, then it emits return light signals which contain a connection data frame validating its presence. Otherwise, the search cycle is repeated.

[0080] Each search cycle comprises at least one transmission period and at least one silence period, the sum of the silence periods being at least 10 times longer than the sum of the transmission periods, such that during a search cycle, the binary control signal takes the first value for a first duration at least 10 times shorter than a second duration during which the binary control signal takes the second value.

[0081] We see on the figure 8 an example of a binary control signal Sbc associated with a peripheral search frame. The duration of the search cycle Cr is equal to 40ms. The binary control signal Sbc comprises two short pulses comprising a first pulse 60 (corresponding to a first transmission period) having a duration equal to 510µs and a second pulse 61 (corresponding to a second transmission period) having a duration equal to 120µs, the first pulse 60 and the second pulse 61 being spaced apart by a duration equal to 150µs.

[0082] Following the communication cut, the dongle LiFi 2, due to its configuration firmware, will send out emitted light signals again only if communication is reestablished at the initiative of the LiFi access point 1 via the emission of emitted light signals including device search frames. As long as these emitted light signals are not received and decoded by the dongle LiFi 2, this one remains “silent”.

[0083] So, from the moment the communication is broken, the IR LED 124 of the dongle LiFi 2 is disabled. If the obstacle that breaks the communication is a user looking closely at the LiFi 2 dongle, this user is not at risk of eye damage since the IR LED 124 of the LiFi 2 dongle is switched off and remains switched off as long as the user is positioned near the LiFi 2 dongle.

[0084] If communication is cut off due to the presence of a user's face, the LiFi access point 1, for its part, will continue to search for the presence of devices by emitting transmitted light signals containing the device search frames. However, even if the user's face is in the vicinity of the LiFi access point 1, despite the emission of these transmitted light signals, the user's eye safety is ensured because, in each search cycle Cr, the first pulse 60 and the second pulse 61 have a very short duration and are followed by a long period of "silence".

[0085] It should be noted here that the massive deployment of wireless communication technology relies heavily on the miniaturization of the electronic components used to implement it. For example, the WiFi function can be achieved with two main components designed to take up little space and consume little power. In the case of LiFi, these miniaturized components do not yet exist. Therefore, discrete off-the-shelf electronic components are used, which were not initially designed for such a use case. The assembly of these components certainly makes it possible to achieve the desired functions, but for a larger size, a higher price, and a higher power consumption than what can be achieved with miniaturized components. The invention at least solves the problem of consumption.

[0086] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0087] The implemented wireless optical communication is not necessarily a communication according to the LiFi protocol.

[0088] It has been indicated here that the light source comprises an LED. The light source could be different and for example comprise a resonant cavity LED or a VCSEL (for vertical-cavity surface-emitting-laser, i.e. vertical cavity surface emitting laser diode). The light source may comprise several similar components, for example several LEDs, or several different components, for example one or more LEDs and one or more VCSELs.

[0089] In the case where the light source includes several LEDs, these can be connected in series or in parallel. In this case, the cut-off circuit of the figure 7 is the same, the IR 24 LED being replaced by the LEDs connected in series or in parallel.

[0090] Similarly, the photoreceptor could be different and include one or more PIN photodiodes, one or more avalanche photodiodes or a single-photon avalanche diode or an array of single-photon avalanche diodes.

[0091] Here we have described the use of a baseband modem, but it is possible to use a different processing component: processor, microcontroller, FPGA, etc. The analog-to-digital converter and the digital-to-analog converter are not necessarily integrated into the processing component.

[0092] It has been described here that the wireless optical communication device is integrated into an access point positioned on the ceiling of a room. The architecture of the access point may be different from that presented here.

[0093] The baseband modem and the amplification stages could, for example, be "centralized" and located in the same central equipment connected to a plurality of photonic antennas (comprising LEDs and photodiodes) positioned on the ceiling of the same room or different rooms. The photonic antennas are connected to the central equipment by one or more cables comprising, for example, a coaxial cable, a power cable, a telephone cable, a plastic fiber, etc. In this architecture, the wireless optical communication device according to the invention is therefore integrated into several pieces of equipment.

[0094] The peripheral equipment that communicates with the access point and in which the wireless optical communication device is integrated is not necessarily a dongle but could be any equipment suitable for communicating via wireless optical communication: computer, tablet, smartphone, smart watch, smart speaker, etc.

[0095] In the case where the wireless optical communication device is integrated into a dongle, this is not necessarily connected to a computer but can be connected to other equipment: tablet, smartphone, smartwatch, smart speaker, etc.

[0096] It is noted that the invention can be implemented in any type of application: home network, industrial network, robotics, inside a car, a train, an airplane, etc.

Claims

1. An access point (1) comprising an optical wireless communication device including: - a processing component (14; 114) arranged to produce transmitted digital signals during transmission periods (Pe) ; - a digital-to-analog converter (15; 115) arranged to produce transmitted analog signals from the transmitted digital signals; - a light source (24; 124) arranged to produce transmitted light signals from the transmitted analog signals; - a shutdown circuit (25; 125) arranged to selectively activate or deactivate the light source; characterized in that the processing component comprises a binary output (40; 140) and is arranged to generate and apply to the binary output a binary control signal (Sbc) which is in a first state during the transmission periods and in a second state outside the transmission periods, the shutdown circuit being arranged to receive the binary control signal, and to activate the light source when the binary control signal is in the first state and to deactivate the light source when the binary control signal is in the second state, in that the processing component (14) is arranged to transmit, during search cycles, transmitted digital signals containing search frames for searching peripherals that may be connected to the access point, and in that each search cycle comprises at least one transmission period and at least one silence period, a sum of the silence periods being at least 10 times longer than a sum of the transmitting periods, so that during a search cycle, the binary control signal is in the first state for a first duration at least 10 times shorter than a second duration during which the binary control signal is in the second state.

2. The access point (1) as claimed in claim 1, wherein the processing component is a baseband modem (14; 114) .

3. The access point (1) as claimed in claim 2, wherein the baseband modem is an off-the-shelf integrated circuit originally designed to meet a telecommunications standard.

4. The access point (1) as claimed in any one of claims 1 to 3, wherein the binary output is a GPO output, for "General Purpose Output".

5. The access point (1) as claimed in any one of claims 1 to 4, wherein the shutdown circuit comprises a transistor (52) forming a switch controlled by the binary control signal, and wherein the light source comprises a terminal connected to a source of a bias voltage (V_LED) and a terminal connected to an electrical ground (56) via the transistor (52).