WO2018100406A1 - Systems and methods for duplex visible light communication without external power source based on backscattering of modulated light - Google Patents

Systems and methods for duplex visible light communication without external power source based on backscattering of modulated light Download PDF

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Publication number
WO2018100406A1
WO2018100406A1 PCT/IB2016/001929 IB2016001929W WO2018100406A1 WO 2018100406 A1 WO2018100406 A1 WO 2018100406A1 IB 2016001929 W IB2016001929 W IB 2016001929W WO 2018100406 A1 WO2018100406 A1 WO 2018100406A1
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Prior art keywords
electronic device
optical signal
light
optical
source
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PCT/IB2016/001929
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French (fr)
Inventor
Byung-Jun Jang
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Kookmin University Industry Academy Cooperation Foundation
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Priority to PCT/IB2016/001929 priority Critical patent/WO2018100406A1/en
Priority to KR1020197010482A priority patent/KR102125357B1/en
Publication of WO2018100406A1 publication Critical patent/WO2018100406A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
    • H04B10/114—Indoor or close-range type systems
    • H04B10/116—Visible light communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/40—Transceivers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/501—Structural aspects
    • H04B10/502—LED transmitters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Communication System (AREA)

Abstract

A method for optical communication includes, at a first electronic device with a light source and an optical sensor, receiving data communication from a second electronic device that is separate and distinct from the first electronic device. The method also includes transmitting from the light source, over time, a first optical signal representing a carrier wave having one or more characteristic time parameters; and, in conjunction with transmitting from the light source, over time, the first optical signal representing the carrier wave having the one or more characteristic time parameters, receiving from the second electronic device, over time, a second optical signal that is distinct from the first optical signal. The method further includes obtaining a processed signal from the second optical signal by demodulating the second optical signal using the carrier wave having the one or more characteristic time parameters; and transmitting the processed signal for further processing.

Description

Systems and Methods for Duplex Visible Light Communication without External Power Source Based on Backscattering of
Modulated Light
TECHNICAL FIELD
[0001] This application relates generally to electronic devices and circuits for optical communications. More particularly, the disclosed embodiments relate to electronic devices and circuits for optical communications that operate without an external power source.
BACKGROUND
[0002] Recent advancements in the Internet of Things (IoT) technologies are expected to facilitate integration of traditionally non-networked devices with computer networks, which will lead to improved efficiency and provide capabilities that were not available before.
[0003] Communications for an IoT device typically require a separate power source
(e.g., a battery), which has limited the adoption of the IoT technologies. For example, the separate power source may stop operation (e.g., the battery may get drained), and thus, requires periodic inspection and maintenance, which is not suitable when the IoT technologies are to be used with a large number of devices.
[0004] Although battery-less communication techniques have been explored, such techniques have other limitations. For example, battery-less near field communication (NFC) techniques require a reader to be placed in close proximity to a tag (e.g., typically within 1 cm or less), and thus, longer range communications have not been possible with such communication techniques.
SUMMARY
[0005] Thus, there is a need for communication methods and devices that allow a mid or long range communication without requiring a separate power source.
[0006] A number of embodiments (e.g., of electronic devices or circuits, and methods of operating such devices or circuits) that overcome the limitations and disadvantages described above are presented in more detail below. These embodiments provide devices, circuits, and methods for using and operating devices, for optical communications. [0007] As described in more detail below, some embodiments involve a method for an optical communication, which includes, at a first electronic device with a light source and an optical sensor, receiving data communication from a second electronic device that is separate and distinct from the first electronic device. The method also includes transmitting from the light source, over time, a first optical signal representing a carrier wave having one or more characteristic time parameters; and, in conjunction with transmitting from the light source, over time, the first optical signal representing the carrier wave having the one or more characteristic time parameters, receiving from the second electronic device, over time, a second optical signal that is distinct from the first optical signal. The method further includes obtaining a processed signal from the second optical signal by demodulating the second optical signal using the carrier wave having the one or more characteristic time parameters; and transmitting the processed signal for further processing.
[0008] In accordance with some embodiments, an electronic device for optical communication includes a light source, an optical sensor, and one or more processors coupled with the light source and the optical sensor and configured to receive data communication from a second electronic device that is separate and distinct from the electronic device. The one or more processors are also configured to initiate transmission from the light source, over time, a first optical signal representing a carrier wave having one or more characteristic time parameters; and, in conjunction with transmission from the light source, over time, of the first optical signal representing the carrier wave having the one or more characteristic time parameters, receive from the second electronic device, over time, a second optical signal that is distinct from the first optical signal. The one or more processors are further configured to obtain a processed signal from the second optical signal by demodulating the second optical signal using the carrier wave having the one or more characteristic time parameters; and initiate transmitting the processed signal for further processing.
[0009] In accordance with some embodiments, a computer readable storage medium stores one or more programs for execution by one or more processors of an electronic device with a light source and an optical sensor. The one or more programs include instructions for receiving data communication from a second electronic device that is separate and distinct from the electronic device. The one or more programs include instructions for initiating transmission from the light source, over time, a first optical signal representing a carrier wave having one or more characteristic time parameters; and, in conjunction with transmission from the light source, over time, of the first optical signal representing the carrier wave having the one or more characteristic time parameters, receiving from the second electronic device, over time, a second optical signal that is distinct from the first optical signal. The one or more programs further include instructions for obtaining a processed signal from the second optical signal by demodulating the second optical signal using the carrier wave having the one or more characteristic time parameters; and initiating transmitting the processed signal for further processing.
[0010] In accordance with some embodiments, a method for optical communication includes, at an electronic device with a photovoltaic device and an electro-optic reflector, receiving light from a source electronic device; generating an electric power from the light received from the source electronic device; and utilizing the electric power generated from the light received from the source electronic device to activate and deactivate, over time, the electro-optic reflector in accordance with transmission data to selectively return the light from the source electronic device.
[0011] In accordance with some embodiments, an electronic device for optical communication includes a photovoltaic device, an electro-optic reflector, and one or more processors coupled with the photovoltaic device and the electro-optic reflector and configured to utilize an electric power generated from light received from a source electronic device to activate and deactivate, over time, the electro-optic reflector in accordance with transmission data to selectively return the light from the source electronic device.
[0012] In accordance with some embodiments, a computer readable storage medium stores one or more programs for execution by one or more processors of an electronic device with a polar panel and an electro-optic reflector. The one or more programs include instructions for utilizing an electric power generated from light received from a source electronic device to activate and deactivate, over time, the electro-optic reflector in accordance with transmission data to selectively return the light from the source electronic device.
[0013] In accordance with some embodiments, a method for optical communication includes, at an electronic device with an optical sensor and a light source, receiving a first optical signal from a source electronic device. The first optical signal includes a component representing a carrier wave having one or more characteristic time parameters. The method also includes constructing the carrier wave based on the optical signal from the source electronic device; and outputting a second optical signal using the light source in accordance with the constructed carrier wave and transmission data.
[0014] In accordance with some embodiments, an electronic device for optical communication includes an optical sensor, a light source, and one or more processors coupled with the optical sensor and the light source and configured to receive a first optical signal from a source electronic device. The first optical signal includes a component representing a carrier wave having one or more characteristic time parameters. The one or more processors are also configured to construct the carrier wave based on the optical signal from the source electronic device; and output a second optical signal using the light source in accordance with the constructed carrier wave and transmission data.
[0015] In accordance with some embodiments, a computer readable storage medium stores one or more programs for execution by one or more processors of an electronic device with an optical sensor and a light source. The one or more programs include instructions for receiving a first optical signal from a source electronic device. The first optical signal includes a component representing a carrier wave having one or more characteristic time parameters. The one or more programs also include instructions for constructing the carrier wave based on the optical signal from the source electronic device; and outputting a second optical signal using the light source in accordance with the constructed carrier wave and transmission data.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] For a better understanding of the aforementioned aspects as well as additional aspects and embodiments thereof, reference should be made to the Description of Embodiments below, in conjunction with the following drawings.
[0017] Figure 1 is a schematic diagram illustrating a communication system in accordance with some embodiments.
[0018] Figure 2A is a schematic diagram illustrating a communication system in accordance with some embodiments.
[0019] Figure 2B is a schematic diagram illustrating a communication system in accordance with some embodiments. [0020] Figure 2C is a schematic diagram illustrating an electronic device in accordance with some embodiments.
[0021] Figure 3 is a schematic diagram illustrating a transmission control protocol in accordance with some embodiments.
[0022] Figure 4 illustrates examples of communication signals.
[0023] Figure 5A illustrates an example of communication signals from a tag device in accordance with some embodiments.
[0024] Figure 5B illustrates an example of communication signals from a tag device in accordance with some embodiments.
[0025] Figure 6 is a block diagram illustrating a reader device in accordance with some embodiments.
[0026] Figure 7 is a block diagram illustrating a tag device in accordance with some embodiments.
[0027] Figure 8 is a flow diagram illustrating a method performed by a reader device in accordance with some embodiments.
[0028] Figure 9 is a flow diagram illustrating a method performed by a tag device in accordance with some embodiments.
[0029] Figure 10 is a flow diagram illustrating a method performed by a tag device in accordance with some embodiments.
[0030] Like reference numerals refer to corresponding parts throughout the figures.
DESCRIPTION OF EMBODIMENTS
[0031] As explained above, traditional communication methods and devices require a separate power source (e.g., a battery) and have a short communication distance, which have limited applications in the IoT devices.
[0032] Devices, circuits, and methods that address the above problems are described herein. By using visible light for communications, a visible light source (e.g., a light bulb, such as a light-emitting-diode (LED) light bulb) can be used to transmit information (e.g., from a reader device to a tag device). For receiving information back (e.g., from the tag device to the reader device), the tag device utilizes an electric power generated by converting light received from the reader device, thereby eliminating a need for a separate power source (e.g., a battery). In addition, synchronous demodulation is used to reduce the influence of a noise in the ambient light, thereby facilitating accurate communications and extending a communication range.
[0033] Reference will be made to certain embodiments, examples of which are illustrated in the accompanying drawings. While the underlying principles will be described in conjunction with the embodiments, it will be understood that it is not intended to limit the scope of claims to these particular embodiments alone. On the contrary, the claims are intended to cover alternatives, modifications and equivalents that are within the scope of the claims.
[0034] Moreover, in the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these particular details. In other instances, methods, procedures, components, and networks that are well- known to those of ordinary skill in the art are not described in detail to avoid obscuring aspects of the underlying principles.
[0035] It will also be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first electronic device could be termed a second electronic device, and, similarly, a second electronic device could be termed a first electronic device, without departing from the scope of the claims. The first electronic device and the second electronic device are both electronic devices, but they are not the same electronic devices.
[0036] The terminology used in the description of the embodiments herein is for the purpose of describing particular embodiments only and is not intended to limiting of the scope of claims. As used in the description and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
[0037] Figure 1 is a schematic diagram illustrating communication system 100 in accordance with some embodiments.
[0038] In Figure 1, communication system 100 includes reader device 110 and tag device 120. In some embodiments, communication system 100 includes one reader device 110 and a plurality of tag devices 120. In some embodiments, communication system 100 includes a plurality of reader devices 110 and one tag device 120. In some embodiments, communication system 100 includes a plurality of reader devices 110 and a plurality of tag devices 120.
[0039] Reader device 110 includes light source 112 for generating light. In some embodiments, light source 112 is configured to generate light for transmission of optical signals (e.g., optical signals that include data for transmission). In some embodiments, light source 112 is configured to provide energy by transmission of light (e.g., for subsequent conversion into an electric power by a photovoltaic device, such as a solar panel, coupled with a tag device). In some embodiments, reader device 110 is coupled with light source 112, but does not include light source 112 as part of reader device 110 (e.g., light source 112 is separate from reader device 110). In some embodiments, light source 112 is integrated with an ambient light source (e.g., a room light). This allows tag device 120 positioned at a location illuminated by the light from the ambient light source (e.g., in a room illuminated by the room light) to receive optical signals included in the light from the ambient light source.
[0040] Reader device 110 also includes optical sensor 114 (e.g., a photodiode) for receiving light. In some embodiments, optical sensor 114 is configured to receive light from another electronic device, such as tag device 120.
[0041] In some embodiments, tag device 120 includes an electro-optic reflector (e.g., a combination of reflector 124 and electro-optic shutter 126, such as a liquid crystal shutter). In some embodiments, electro-optic shutter 126 includes a linear polarizer and a liquid crystal cell with nematic liquid crystals. The liquid crystal cell includes electrodes. When no voltage is applied, the nematic liquid crystals rotate a polarization of an incoming light by 90 degrees. When a sufficient voltage is applied, the nematic liquid crystals are reoriented and the polarization of the incoming light is maintained. In some embodiments, the incoming light is linearly polarized (e.g., light source 112 generates linearly polarized light or generates randomly polarized light, which is transmitted through a linear polarizer). The linear polarizer of the electro-optic reflector is configured to either transmit the polarization-rotated light and block the polarization-maintained light, or transmit the polarization-maintained light and block the polarization-rotated light. Thus, by changing the voltage applied to the electro-optic shutter, the electro-optic shutter will change between a transmission state (e.g., a state in which the electro-optic shutter transmits light) and a blocking state (e.g., a state in which the electro-optic shutter blocks light). This, in turn, allows the electro-optic reflector to conditionally reflect light (e.g., when the electro-optic shutter is in a transmission state, the electro-optic reflector reflects light and when the electro-optic shutter is in a blocking state, the electro-optic reflector foregoes reflection of light). By adjusting the timing of reflection, tag device 120 can send optical signal back to reader device 110, thereby enabling duplex communications.
[0042] In some embodiments, tag device 120 includes photovoltaic device 122 (e.g., a solar panel) configured to convert light into an electric power. For example, light transmitted from reader device 110 can be converted into an electric power by photovoltaic device 122 of tag device 120, and the electric power, in turn, can be used to power the operations of tag device 120. Thus, tag device 120 does not require an external power source (e.g., a battery or a power adapter). This extends the lifetime of tag device 120, as the lifetime of tag device 120 is not limited by a lifetime of the external power source (e.g., a battery). In addition, the use of tag device 120 in locations where periodic inspection and services are difficult (e.g., in locations where a wall power is not available or where batteries cannot be readily exchanged).
[0043] Figure 2A is a schematic diagram illustrating a communication system in accordance with some embodiments.
[0044] In Figure 2 A, reader device 110 includes waveform generator 212 configured to generate a periodic waveform, such as a pulse train or a continuous wave (e.g., a sinusoidal wave). Reader device 110 also includes demodulator 222 configured to demodulate a received signal using the periodic waveform from waveform generator 212, thereby allowing synchronous demodulation. In some embodiments, demodulator 222 is an I/Q demodulator. The synchronous demodulation improves the fidelity of the received signal, and reduces the interference caused by ambient light and other sources (e.g., noises caused by scattering, moving objects in the proximity, etc.). [0045] In some embodiments, reader device 110 also includes light source driver 214 configured to cause light source 112 to generate light (e.g., by amplifying a voltage or a current of the electric signal provided to light source 112).
[0046] In some embodiments, reader device 110 includes optical element 216 (e.g., a lens or an optical concentrator) configured to focus light (e.g., light received from tag device 120) onto optical sensor 114. In some embodiments, reader device 110 includes optical filter 218. In some embodiments, optical filter 218 is configured to transmit light of a particular wavelength range (e.g., a wavelength range of light generated by light source 112) and block or attenuate other wavelengths, thereby reducing interference by ambient light (e.g., having a different wavelength). In some embodiments, reader device 110 includes one or more apertures and one or more baffles to block or attenuate light from a source other than tag device 120.
[0047] In some embodiments, reader device includes bandpass filter 220. Bandpass filter 220 is configured to transmit a particular frequency range of electric signals and block or attenuate signals of other frequencies, thereby reducing interference by ambient light (e.g., having a different frequency component or movement of objects in the proximity).
[0048] In some embodiments, reader device includes signal processor 224 (also called herein a decoder) configured to further process the demodulated signals. In some
embodiments, signal processor 224 transmits the processed signals (or the demodulated signals) for further processing (e.g., communications to other circuits or devices, comparison with a predefined pattern for identifying tag device 120, retrieving one or more values from the processed signals, etc.).
[0049] In Figure 2 A, tag device 120 includes photovoltaic device 122 for generating an electric power. In some embodiments, tag device 120 also includes energy storage device 232 (e.g., a capacitor) to hold the electric power, which reduces the fluctuation of the electric power. Tag device 120 includes control circuit 230 for electro-optic shutter 126. In Figure 2A, reflector 124 (Figure 1) is not illustrated for brevity. Control circuit 230 utilizes the electric power generated by photovoltaic device 122 for conditionally activating and deactivating electro-optic shutter 126. For example, control circuit 230 activates electro-optic shutter 126 at a first time (e.g., allowing reflection of light from reader device 110) and deactivate electro-optic shutter 126 at a second time that is different from the first time (e.g., preventing or reducing reflection of the light from reader device 110). In some embodiments, control circuit 230 switches electro-optic shutter 126 between an activated state and a deactivated state in accordance with transmission data (e.g., data stored in tag device 120, such as a unique identifier of tag device 120, and/or data generated or measured by tag device 120, such as a temperature around tag device 120 or a number of times tag device 120 has provided information to one or more reader devices 110).
[0050] Figure 2B is a schematic diagram illustrating a communication system in accordance with some embodiments.
[0051] In Figure 2B, reader device 110 is identical to reader device 110 illustrated in
Figure 2A. Thus, the description of reader device 110 is not repeated herein for brevity.
[0052] Figure 2B illustrates tag device 130, which includes optical sensor 242 and phase locked loop module 246. Optical sensor 242 is configured to receive an optical signal from reader device 110 (and converts the optical signal to an electric signal), where the optical signal includes a carrier wave component (e.g., a continuous wave or a pulse train). Phase locked loop module 246 constructs a carrier wave based on the carrier wave component in the received optical signal.
[0053] In some embodiments, tag device 130 also includes receiver 244 configured to preprocess signals from optical sensor 242 (e.g., filtering noises in the electrical signal).
[0054] Tag device 130 includes transmitter 248 and/or control circuit 230 for electro- optic shutter 126. Transmitter 248, when included in tag device 130, is coupled with light source 250 to generate light that includes an optical signal for transmission to reader device 110. Control circuit 230, when included in tag device 130, is coupled with electro-optic shutter 126 to conditionally transmit and block light for generating or modulating an optical signal for transmission to reader device 110 (e.g., light source 250 is activated to generate light and electro-optic shutter 126 is sequentially activated and deactivated to generate an optical signal). In some embodiments, both transmitter 248 and control circuit 230 are used to transmit an optical signal from tag device 130 to reader 110. In some embodiments, the optical signal transmitted from tag device 130 is based on transmission data (e.g., data stored in tag device 120, such as a unique identifier of tag device 120, and/or data generated or measured by tag device 120).
[0055] Figure 2C is a schematic diagram illustrating an electronic device (e.g., a reader device) in accordance with some embodiments. [0056] The electronic device shown in Figure 2C is similar to reader device 110 illustrated in Figure 2A, except that the electronic device shown in Figure 2C includes lowpass filter 252.
[0057] As an example of an operation of the electronic device, waveform generator
212 generates a pulse train with 1 MHz frequency. Light from a tag device would also have the same carrier wave component (e.g., a pulse train with 1 MHz frequency). In some embodiments, bandpass filter 220 is configured to have 4% bandwidth of a center frequency (e.g., for 1 MHz center frequency, the bandpass filter 220 transmits a signal between 0.996 MHz and 1.004 MHz). In some embodiments, lowpass filter 252 is configured to have 2% bandwidth of the center frequency of the bandpass filter (e.g., lowpass filter 252 has 2 KHz bandwidth).
[0058] In some embodiments, decoder 254 in Figure 2C corresponds to signal processor 224 illustrated in Figure 2A.
[0059] Although Figure 2C illustrates an example using a pulse train as a carrier wave, a continuous wave can be used as a carrier wave instead of a pulse train. In some
embodiments, the light from a tag device is amplitude modulated. In some embodiments, the light from a tag device is frequency modulated. In some embodiments, the light from a tag device is phase modulated.
[0060] Figure 3 is a schematic diagram illustrating a transmission control protocol in accordance with some embodiments. The transmission control protocol illustrated in Figure 3 is for a half-duplex communication.
[0061] In Figure 3, a reader device sends a request for data communication (e.g., the reader device transmits an optical signal that represents a request for data communication).
[0062] The tag device, in response to receiving the request for data communication, sends data to the reader device (e.g., the tag device transmits an optical signal, or modulates back-reflected light, that represents transmission data).
[0063] Optionally, the reader device, in response to receiving the data from the tag device, transmits an acknowledgement signal (also called herein "ACK") to the tag device.
[0064] In some embodiments, the reader device repeats sending a request for data communication for receiving additional data from the tag device. [0065] Figure 3 also illustrates examples of signals (e.g., signals transmitted from the reader device to the tag device, clock signals (or carrier waves) transmitted from the reader device to the tag device, and signals transmitted from the tag device to the reader device).
[0066] In some embodiments, the request for data communication is encoded using a
Manchester code. In a Manchester code, each data bit is represented by a combination of a low signal and a high signal of equal time (e.g., 1 is represented by a low signal followed by a high signal and 0 is represented by a high signal followed by a low signal). This allows the reader to transmit light having a stable average power, which is advantageous for the operation of the tag device (when a portion of the light is used for generating an electric power). In addition, this reduces flickering of the light, which is better suited for use in ambient lighting.
[0067] Figure 4 illustrates examples of communication signals. In Figure 4, the reader device transmits data to the tag device. In Figure 4, while the reader device transmits data to the tag device, the tag device does not transmit data to the reader device. In some
embodiments, the reader device optionally transmits a request for data communication to the tag device. Figure 4 also illustrates that subsequent to transmission of data from the reader device to the tag device, the reader device transmits clock signals to the tag device. While the clock signals are transmitted from the reader device to the tag device, the tag device transmits optical signals to the reader device (e.g., by modulating back-reflection or back-scattering of light from the reader device as shown in Figure 2A, or transmitting modulated light as shown in Figure 2B).
[0068] Figure 5A illustrates an example of communication signals from a tag device
(e.g., tag device 120 in Figure 2 A) in accordance with some embodiments.
[0069] The signals from the tag device (e.g., tag device 120) include a carrier wave component (e.g., 1 MHz pulses). In Figure 5A, when the tag device reflects light (so that the carrier wave component is received by a reader device), the reflected light represents data bit 1, and when the tag device foregoes reflection of light (so that the carrier wave component is not received by the reader device), the absence of the reflected light represents data bit 0. Alternatively, the reflected light can represent data bit 0, and the absence of the reflected light can represent data bit 1. In Figure 5 A, the data can be transmitted at a rate of approximately 200 KHz. [0070] Figure 5B illustrates an example of communication signals from a tag device
(e.g., tag device 130 in Figure 2B) in accordance with some embodiments.
[0071] The signals from the tag device (e.g., tag device 130) include a carrier wave component (e.g., 1 MHz pulses). In Figure 5B, the phase of the carrier wave is modulated. When the phase of the carrier wave is modulated, a data bit represented by the signals is reversed. For example, an initial data bit representing "1" is followed by a phase change, the phase change indicates that a subsequent data bit is not "1" (in other words, the subsequent data bit is "0"). Similarly, when the phase changes while the current data bit is "0," a subsequent data bit is not "0" (in other words, the subsequent data bit is "1").
[0072] Figure 6 is a block diagram illustrating reader device 110 in accordance with some embodiments.
[0073] Reader device 110 typically includes one or more processors 602 (e.g., a microprocessor, such as a central processing unit), memory 606, and one or more
communication buses 608 for interconnecting these components. In some embodiments, the communication buses 608 include circuitry (sometimes called a chipset) that interconnects and controls communications between system components. In some embodiments, reader device 110 also includes one or more communication interfaces 604 for transmitting data and/or receiving data to other devices and/or circuits.
[0074] Memory 606 includes high-speed random access memory, such as DRAM,
SRAM, DDR RAM or other random access solid state memory devices; and may include non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. Memory 606 may optionally include one or more storage devices remotely located from one or more processors 602. Memory 606, or alternately the non-volatile memory device(s) within memory 606, comprises a computer readable storage medium. In some embodiments, memory 606, or the non-volatile memory device(s) within memory 606, comprises a non- transitory computer readable storage medium. In some embodiments, memory 606 or the computer readable storage medium of memory 606 stores the following programs, modules and data structures, or a subset thereof:
• Operating System 610 that includes procedures for handling various basic system services and for performing hardware dependent tasks; • Network Communication Module (or instructions) 612 that is used for connecting reader device 110 to other computers (e.g., a remote server system) via the one or more network interfaces 604 and one or more communications networks, such as the Internet, other wide area networks, local area networks, metropolitan area networks, and so on;
• Waveform Generator Module 614 that is used for generating a predefined waveform (e.g., in conjunction with a digital-to-analog converter);
• Light Source Driver Module 616 that is used for activating light source 112 or its driver 642;
• Filter Modules 618, which optionally include bandpass filter module 620 and/or lowpass filter module 622 for processing signals;
• Demodulator Module 624 that is used for extracting data from a modulated carrier wave signal; and
• Data Transmission Module 628 that is used for transmitting data extracted from the modulated carrier wave signal to other devices or circuits.
[0075] In some embodiments, reader device 110 includes peripherals controller 652, which is configured for controlling other circuits and/or hardware components.
[0076] In some embodiments, peripherals controller 652 controls light source 112, or driver 642 coupled with light source 112 (if driver 642 is included), to cause light source 112 to generate light. In some embodiments, peripherals controller 652 controls light source 112, or driver 642 coupled with light source 112, in conjunction with light source driver module 616 to generate an optical signal.
[0077] In some embodiments, peripherals controller 652 transmits signals from optical sensor 114 or receiver 644 coupled with optical sensor 114 (if receiver 644 is included). For example, peripherals controller 652 transmits signals from optical sensor 114 or receiver 644 for processing by one or more processors 602.
[0078] Figure 7 is a block diagram illustrating a tag device (e.g., tag device 120 in
Figure 2A or tag device 130 in Figure 2B) in accordance with some embodiments.
[0079] A tag device (e.g., tag device 120 or tag device 130) typically includes one or more processors 702 (e.g., a microprocessor, such as a central processing unit), memory 706, and one or more communication buses 708 for interconnecting these components. In some embodiments, the communication buses 708 include circuitry (sometimes called a chipset) that interconnects and controls communications between system components.
[0080] Memory 706 includes high-speed random access memory, such as DRAM,
SRAM, DDR RAM or other random access solid state memory devices; and may include non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. Memory 706 may optionally include one or more storage devices remotely located from one or more processors 702. Memory 706, or alternately the non-volatile memory device(s) within memory 706, comprises a computer readable storage medium. In some embodiments, memory 706, or the non-volatile memory device(s) within memory 706, comprises a non- transitory computer readable storage medium. In some embodiments, memory 706 or the computer readable storage medium of memory 706 stores the following programs, modules and data structures, or a subset thereof:
• Operating System 710 that includes procedures for handling various basic system services and for performing hardware dependent tasks;
• Phase Locked Loop Module 712 that is used for (re)constructing a carrier wave;
• Light Source Driver Module 714 that is used for activating light source 742 or its driver 752;
• Shutter Control Modules 716 that is used for activating and deactivating shutter 746 (e.g., an electro-optic shutter or a mechanical shutter); and
• Transmission Data 718 that represents data to be transmitted to a reader device and optionally includes a unique identifier for the tag device.
[0081] In some embodiments, the tag device includes peripherals controller 750, which is configured for controlling other circuits and/or hardware components.
[0082] In some embodiments, peripherals controller 750 controls light source 742, or driver 752 coupled with light source 742 (if driver 752 is included), to cause light source 742 to generate light. In some embodiments, peripherals controller 750 controls light source 742, or driver 752 coupled with light source 742, in conjunction with light source driver module 714 to generate an optical signal (e.g., an optical signal encoding transmission data 718). [0083] In some embodiments, peripherals controller 750 transmits signals from optical sensor 744 or receiver 754 coupled with optical sensor 744 (if receiver 754 is included). For example, peripherals controller 750 transmits signals from optical sensor 744 or receiver 754 for processing by one or more processors 702.
[0084] In some embodiments, peripherals controller 750 controls shutter 746, or shutter controller 756 coupled with shutter 746 (if shutter controller 756 is included), to modulate light (e.g., back-reflected or back- scattered light or light generated by light source 742). In some embodiments, peripherals controller 750 controls shutter 746 or shutter controller 756 coupled with shutter 746, in conjunction with shutter control module 716 to generate an optical signal (e.g., an optical signal encoding transmission data 718).
[0085] Figure 7 also illustrate optional photovoltaic device 122 that is used to convert light into an electric power, which is used for operating several components of the tag device, such as one or more processors 702, shutter 746, shutter controller 756, etc. Not all power lines from photovoltaic device 122 are illustrated in Figure 7 so as not to obscure other aspects of the tag device.
[0086] Figure 8 is a flow diagram illustrating method 800 performed by a reader device (e.g., reader device 110 in Figure 2A) in accordance with some embodiments. The reader device includes a light source (e.g., light source 112 in Figure 1) and an optical sensor (e.g., optical sensor 114 in Figure 1). With respect to Figure 8, the reader device is also called a first electronic device and a tag device is also called a second electronic device.
[0087] In some embodiments, prior to receiving data communication from the second electronic device, the first electronic device transmits (802), over time, an optical signal that includes data for transmission from the first electronic device to the second electronic device (e.g., in Figure 4, the reader device transmits data to the tag device before receiving data from the tag device). As shown in Figure 4, the optical signal typically includes data bits (e.g., represented by a high signal and a low signal or combinations of them) that are sequentially transmitted over time.
[0088] In some embodiments, prior to receiving data communication from the second electronic device, the first electronic device transmits (804), over time, an optical signal that represents a request for data communication (e.g., in Figure 3, the reader device transmits a request for data communication before receiving data from the tag device). In some embodiments, the first electronic device transmits, over time, an optical signal that represents the request for data communication after transmitting, over time, the optical signal that includes data for transmission from the first electronic device to the second electronic device.
[0089] The first electronic device receives (806) data communication from a second electronic device that is separate and distinct from the first electronic device. For example, in Figure 1, tag device 120 is separate and distinct from reader device 110.
[0090] The first electronic device transmits (808) from the light source, over time, a first optical signal representing a carrier wave having one or more characteristic time parameters (e.g., in Figure 2C, the reader device transmits an optical signal representing a pulse wave).
[0091] In some embodiments, the carrier wave is a pulse wave. The one or more characteristic time parameters include a pulse duration of the pulse wave, a period of the pulse wave, and/or a duty cycle of the pulse wave.
[0092] In some embodiments, the carrier wave is a continuous wave. The one or more characteristic time parameters include a frequency of the continuous wave.
[0093] The first electronic device, in conjunction with transmitting from the light source, over time, the first optical signal representing the carrier wave having the one or more characteristic time parameters, receives (810) from the second electronic device, over time, a second optical signal that is distinct from the first optical signal. For example, as shown in Figure 4, while the first electronic device (e.g., the reader device) transmits the first optical signal representing the carrier wave, the first electronic device receives from the second electronic device (e.g., the tag device) a second optical signal that is distinct from the first optical signal (e.g., the second optical signal is a modulated optical signal based on the first optical signal).
[0094] In some embodiments, the first optical signal and the second optical signal are in a visible wavelength. For example, the first optical signal is included in visible light output by the light source, which is also used for providing general illumination (e.g., ambient lighting of a room).
[0095] In some embodiments, the second optical signal includes a signal component that has the one or more characteristic time parameters (e.g., in Figure 5A, the optical signal from the tag device includes a portion of the carrier wave component). [0096] The first electronic device obtains (812) a processed signal from the second optical signal by demodulating the second optical signal using the carrier wave having the one or more characteristic time parameters. For example, the carrier wave is used for synchronous demodulation (e.g., the carrier wave is phase-shifted and mixed with the second optical signal). In some embodiments, a phase locked loop is used to extract a carrier wave from the second optical signal, and the extracted carrier wave is phased-shifted and mixed with the second optical signal for synchronous demodulation. In some embodiments, a high gain amplifier is used to remove modulation in the second optical signal, thereby obtaining the carrier wave, which is in turn phase-shifted and mixed with the second optical signal for synchronous demodulation. Although this paragraph describes obtaining the processed signal from the second optical signal by demodulating the second optical signal using the carrier wave, the processed signal may be obtained from an electrical signal that corresponds to the second optical signal by demodulating the electrical signal using the carrier wave.
[0097] In some embodiments, the first electronic device converts (814) the second optical signal into a first electric signal. Demodulating the second optical signal includes: passing the first electrical signal through a bandpass filter to obtain a second electric signal; passing the second electric signal through a demodulator to obtain a third electric signal; and passing the third electric signal through a lowpass filter to obtain a fourth electric signal (e.g., Figure 2C).
[0098] The first electronic device transmits (816) the processed signal for further processing (e.g., the data transmitted from the tag device may be used for identifying the tag device, or operating one or more devices based on the data transmitted from the tag device).
[0099] In some embodiments, subsequent to receiving the data communication from the second electronic device, the first electronic device transmits (818), over time, an optical signal that includes second data for transmission from the first electronic device to the second electronic device (e.g., in Figure 4, the reader device transmits data after receiving data from the tag device).
[00100] Figure 9 is a flow diagram illustrating method 900 performed by a tag device
(e.g., tag device 120 in Figure 2A) in accordance with some embodiments. The tag device includes a photovoltaic device (e.g., photovoltaic device 122 in Figure 2A, such as a solar panel) and an electro-optic reflector (e.g., an electro-optic reflector that includes electro-optic shutter 126 in Figure 2A). With respect to Figure 9, the tag device is also called an electronic device and a reader device is also called a source electronic device.
[00101] In some embodiments, the electronic device does not include a power source other than an optical power generator (e.g., the electronic device does not include a battery or a power adaptor).
[00102] In some embodiments, the electro-optic reflector includes an electro-optic shutter and a reflective surface (e.g., electro-optic shutter 126 and reflector 124 in Figure 1).
[00103] The electronic device receives (902) light from a source electronic device (e.g., tag device 120 receives light from reader device 110 in Figure 2 A).
[00104] The electronic device generates (904) an electric power from the light received from the source electronic device (e.g., the electronic device generates the electric power with photovoltaic device 122 in Figure 2 A).
[00105] The electronic device utilizes (906) the electric power generated from the light received from the source electronic device to activate (908) and deactivate, over time, the electro-optic reflector in accordance with transmission data to selectively return the light from the source electronic device. For example, tag device 120 in Figure 2 A sequentially activates and deactivates the electro-optic reflector (e.g., electro-optic shutter 126 of the electro-optic reflector) to cause back-reflection or back-scattering of light from reader device 110, as represented by the signal shown in Figure 5 A.
[00106] In some embodiments, the electronic device utilizes the electric power generated from the light received from the source electronic device to obtain (910) the transmission data. For example, the tag device also utilizes the electric power generated from the light received from the source electronic device to retrieve data stored in memory (e.g., transmission data 718 in memory 706 in Figure 7) and/or access data from one or more sensors.
[00107] Figure 10 is a flow diagram illustrating method 1000 performed by a tag device in accordance with some embodiments. The tag device includes an optical sensor (e.g., optical sensor 242 in Figure 2B) and a light source (e.g., light source 250 in Figure 2B). With respect to Figure 10, the tag device is also called an electronic device and a reader device is also called a source electronic device. [00108] The electronic device receives (1002) a first optical signal from a source electronic device. The first optical signal includes a component representing a carrier wave having one or more characteristic time parameters (e.g., a pulse wave having one or more characteristic time parameters).
[00109] The electronic device constructs (1004) the carrier wave based on the optical signal from the source electronic device (e.g., using phase locked loop 246 in Figure 2B and/or phase locked loop module 712 in Figure 7).
[00110] In some embodiments, a phase of the constructed carrier wave corresponds (1006) to a phase of the carrier wave represented by the component in the first optical signal.
[00111] The electronic device outputs (1008) a second optical signal using the light source in accordance with the constructed carrier wave and transmission data. For example, as shown in Figure 5B, the phase of the carrier wave is modulated based on the transmission data.
[00112] In some embodiments, the electronic device includes a photovoltaic device (e.g., a solar panel).
[00113] In some embodiments, the electronic device receives (1010) light from the source electronic device, the light including the first optical signal; generates an electric power from the light received from the source electronic device; and utilizes the electric power generated from the light received from the source electronic device to output the second optical signal (e.g., the electric power generated from the light received from the source electronic device is used to power light source 250 and/or transmitter 248).
[00114] In some embodiments, the electronic device utilizes (1012) the electric power generated from the light received from the source electronic device to construct the carrier wave based on the optical signal from the source electronic device (e.g., the electric power generated from the light received from the source electronic device is used to power phase locked loop 246 in Figure 2B).
[00115] In some embodiments, the electronic device includes an electro-optic shutter. The electronic device utilizes (1014) the electric power generated from the light received from the source electronic device to: generate light from the light source in accordance with the constructed carrier wave; and activate and deactivate, over time, the electro-optic shutter in accordance with transmission data (e.g., the light source generates light that corresponds to the carrier wave and the electro-optic shutter is used to modulate the light).
[00116] In some embodiments, the electronic device includes an electro-optic shutter. The electronic device utilizes the electric power generated from the light received from the source electronic device to: generate light from the light source in accordance with transmission data; and activate and deactivate, over time, the electro-optic shutter in accordance with the constructed carrier wave (e.g., the light source generates light that encodes the transmission data and the electro-optic shutter adds the carrier wave).
[00117] The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.

Claims

What is claimed is:
1. A method for optical communication, comprising:
at a first electronic device with a light source and an optical sensor:
receiving data communication from a second electronic device that is separate and distinct from the first electronic device, including:
transmitting from the light source, over time, a first optical signal representing a carrier wave having one or more characteristic time parameters; and,
in conjunction with transmitting from the light source, over time, the first optical signal representing the carrier wave having the one or more characteristic time parameters, receiving from the second electronic device, over time, a second optical signal that is distinct from the first optical signal;
obtaining a processed signal from the second optical signal by demodulating the second optical signal using the carrier wave having the one or more characteristic time parameters; and
transmitting the processed signal for further processing.
2. The method of claim 1, wherein:
the carrier wave is a pulse wave; and
the one or more characteristic time parameters include a pulse duration of the pulse wave, a period of the pulse wave, and/or a duty cycle of the pulse wave.
3. The method of claim 1, wherein:
the carrier wave is a continuous wave; and
the one or more characteristic time parameters include a frequency of the continuous wave.
4. The method of claim 1, wherein:
the first optical signal and the second optical signal are in a visible wavelength.
5. The method of claim 1, wherein:
the second optical signal includes a signal component that has the one or more characteristic time parameters.
6. The method of claim 1, wherein: the method includes converting the second optical signal into a first electric signal; and
demodulating the second optical signal includes:
passing the first electrical signal through a bandpass filter to obtain a second electric signal;
passing the second electric signal through a demodulator to obtain a third electric signal; and
passing the third electric signal through a lowpass filter to obtain a fourth electric signal.
7. The method of claim 1, including:
prior to receiving the data communication from the second electronic device, transmitting, over time, an optical signal that represents a request for data communication.
8. The method of claim 1, including:
prior to receiving the data communication from the second electronic device, transmitting, over time, an optical signal that includes data for transmission from the first electronic device to the second electronic device.
9. The method of claim 1, including:
subsequent to receiving the data communication from the second electronic device, transmitting, over time, an optical signal that includes second data for transmission from the first electronic device to the second electronic device.
10. An electronic device for optical communication, comprising:
a light source;
an optical sensor; and
one or more processors coupled with the light source and the optical sensor and configured to perform any method of claims 1-9.
11. A computer readable storage medium storing one or more programs, the one or more programs including instructions, which, when executed by one or more processors of an electronic device with a light source and an optical sensor, cause the electronic device to perform any method of claims 1-9.
A method for optical communication, compri at an electronic device with a photovoltaic device and an electro-optic reflector: receiving light from a source electronic device;
generating an electric power from the light received from the source electronic device; and
utilizing the electric power generated from the light received from the source electronic device to:
activate and deactivate, over time, the electro-optic reflector in accordance with transmission data to selectively return the light from the source electronic device.
13. The method of claim 12, wherein:
the electronic device does not include a power source other than an optical power generator.
14. The method of claim 12, wherein:
the electro-optic reflector includes an electro-optic shutter and a reflective surface.
15. The method of claim 12, including:
utilizing the electric power generated from the light received from the source electronic device to:
obtain the transmission data.
16. An electronic device for optical communication, comprising:
a photovoltaic device;
an electro-optic reflector; and
one or more processors coupled with the photovoltaic device and the electro-optic reflector and configured to perform any method of claims 12-15.
17. A computer readable storage medium storing one or more programs, the one or more programs including instructions, which, when executed by one or more processors of an electronic device with a photovoltaic device and an electro-optic reflector, cause the electronic device to perform any method of claims 12-15.
18. A method for optical communication, comprising:
at an electronic device with an optical sensor and a light source: receiving a first optical signal from a source electronic device, wherein the first optical signal includes a component representing a carrier wave having one or more characteristic time parameters;
constructing the carrier wave based on the optical signal from the source electronic device; and
outputting a second optical signal using the light source in accordance with the constructed carrier wave and transmission data.
19. The method of claim 18, wherein:
the electronic device includes a photovoltaic device; and
the method includes:
receiving light from the source electronic device, the light including the first optical signal;
generating an electric power from the light received from the source electronic device; and
utilizing the electric power generated from the light received from the source electronic device to:
output the second optical signal.
20. The method of claim 19, including:
utilizing the electric power generated from the light received from the source electronic device to:
construct the carrier wave based on the optical signal from the source electronic device.
21. The method of claim 19, wherein:
the electronic device includes an electro-optic shutter; and
the method includes utilizing the electric power generated from the light received from the source electronic device to:
generate light from the light source in accordance with the constructed carrier wave; and
activate and deactivate, over time, the electro-optic shutter in accordance with transmission data.
22. The method of claim 18, wherein: a phase of the constructed carrier wave corresponds to a phase of the carrier wave represented by the component in the first optical signal.
23. An electronic device for optical communication, comprising:
an optical sensor;
a light source; and
one or more processors coupled with the optical sensor and the light source and configured to perform any method of claims 18-22.
24. A computer readable storage medium storing one or more programs, the one or more programs including instructions, which, when executed by one or more processors of an electronic device with an optical sensor and a light source, cause the electronic device to perform any method of claims 18-22.
PCT/IB2016/001929 2016-11-29 2016-11-29 Systems and methods for duplex visible light communication without external power source based on backscattering of modulated light WO2018100406A1 (en)

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