Optical wireless communication system and method of operating same

Abstract

An optical wireless communication system includes a first device including a transceiver device and a plurality of other devices including respective other transceiver devices, where the first device is configured to communicate with the plurality of other devices via an optical channel, and the transceiver arrangement of the first device comprises: a receiver comprising at least one photodetector for receiving light representative of optical wireless communication signals transmitted by other devices; a receiver-side processing circuit for processing the optical wireless communication signal to extract data represented by the optical wireless communication signal; a transmitter for transmitting other light representing the optical wireless communication signal; a transmitter-side processing circuit for generating an optical wireless communication signal; a multiplexer device; and a controller. The controller controls the transceiver apparatus to retransmit at least a portion of the optical wireless communication signal received by the receiver from one other device to indicate to the other device that the optical channel of the receiver is busy.

Description

[0001] This application is a divisional application of the invention patent application with application date of October 11, 2019, application number 201980081666.5, and title “Signal Retransmission and Method”. Technical Field

[0002] The present invention relates to wireless communication systems and methods, for example, optical wireless communication systems and methods. Background Art

[0003] It is known to provide wireless data communications by using light rather than radio frequency to wirelessly send and receive data between devices. Data can be transmitted using light by modulating at least one characteristic of the light, such as the intensity of the light. Methods of wirelessly transmitting data using light may be referred to as optical wireless communications (OWC) or optical communications (LC). LiFi is a form of optical wireless communications.

[0004] In an optical wireless communication system (such as a LiFi system), typically, many access points (APs) communicate with many stations (STAs). Both the access points and the stations can be full-duplex devices, capable of sending and receiving at the same time.

[0005] Due to the characteristics of optical channels, optical wireless communications (OWC) or optical communications (LC) can provide advantages over conventional RF wireless communications (such as Wi-Fi TM ). Unlike RF signals, optical signals generally do not penetrate walls, for example, which can improve security. In addition, optical transmissions can be particularly directional in nature.

[0006] In some cases, it may be desirable to adopt Wi-Fi protocols in OWC, such as packet-based protocols such as IEEE TM 802.11 TM This could help integrate technologies such as LiFi and Wi-Fi. However, this is not easy because the properties of the LiFi channel are different compared to Wi-Fi.

[0007] For example, channel sensing and collision avoidance may present different problems for LC (e.g., LiFi) compared to WiFi or other RF communication systems.

[0008] Channel sensing (sometimes referred to as carrier sensing in RF wireless communications) is a method of determining whether a shared medium (e.g., a channel) is in use. Before transmitting, a given node listens to the shared medium (e.g., one or more wireless channels) to determine if one or more other devices are transmitting traffic.

[0009] To reduce the possibility of collisions, various handshake procedures have been developed in RF communications, such as 2-way or 4-way handshake procedures, channel sensing procedures, and the use of backoff times. One example of a system that can provide collision avoidance in RF communications is the IEEE 802.11 RTS / CTS exchange.

[0010] Collision avoidance in relation to channel sensing may refer to avoiding data packets from interfering with other packets at the intended receiver on a single channel network. These collisions may occur if two or more nodes transmit packets at the same time or within the same time period, which may be referred to as a collision period (CP). The use of collision avoidance protocols is well known where there may be hidden nodes (discussed below) or long data packets. For example, a node / STA may send a request to send (RTS) packet to a receiver, such as an AP. If the AP receives the RTS correctly, it responds with a clear to send (CTS). The STA sends a data packet only after successfully receiving the CTS. Receiver-initiated collision avoidance protocols have also been proposed, in which the receiver initiates a handshake as opposed to a transmitter-initiated handshake.

[0011] The hidden node problem may be the result of the lack of effective channel sensing. The hidden node problem is considered a critical issue in OWC as well as some RF-based technologies due to the directional characteristics of optical transmitters (e.g., LEDs) and receivers (e.g., photodetectors). A hidden node is a node in the network whose transmission is not detected by all other nodes (e.g., two mobile stations (STAs)). The hidden node problem may cause conflicts due to concurrent transmissions, resulting in performance degradation of communications in the network.

[0012] Figure 1 is a schematic diagram of a simple LiFi network with an access point (AP) 2 that is able to communicate with two different stations 4, 6 via optical wireless communications. In this example, stations 4, 6 use infrared light for uplink transmissions to AP 2. Because the wavelengths used for uplink and downlink are different, because uplink transmissions in the infrared band are very directional, and because such transmissions are directed toward the AP and not toward other stations, neither station 4, 6 can determine whether the other station 4, 6 is transmitting. Therefore, stations 4, 6 cannot directly use channel sensing techniques to avoid collisions. As a result, station 4 is a hidden node relative to station 6, and vice versa. This is in contrast to RF or Wi-Fi communications, where transmissions may be omnidirectional, so the hidden node problem may not occur or may only occur in specific circumstances.

[0013] As described in WO 2017 / 037437, the contents of which are incorporated herein by reference, it has been suggested to use busy signals to help avoid collisions.

[0014] Although using a medium busy signal can be advantageous, in some cases there may be a long latency between a station starting to send a packet and the AP sending the medium busy signal. If it is desired to encode the packet duration in the medium busy signal, the latency may be even longer because the AP must decode the header of the uplink packet before it can send the busy signal. In some cases, this may increase the likelihood of a collision. Additionally, due to the high latency, downlink efficiency can be reduced in some cases because the AP must first send the busy signal and then send some downlink data (if needed).

[0015] It is an object of the present invention to provide an improved or at least alternative OWC communication system and method. Summary of the invention

[0016] In a first independent aspect, there is provided an optical wireless communication system comprising:

[0017] A first device comprising a transceiver apparatus; and

[0018] A plurality of other devices, each other device comprising a respective other transceiver arrangement.

[0019] The first device is configured to communicate with a plurality of other devices via at least one optical channel. The transceiver means of the first device may include:

[0020] a receiver for receiving light (optionally at a first wavelength or wavelength range) representing an optical wireless communication signal transmitted, for example, by another device. The receiver includes at least one photodetector;

[0021] The transceiver arrangement of the first device may comprise a receiver-side processing circuit for processing the optical wireless communication signal received by the receiver to extract data represented by the received optical wireless communication signal.

[0022] The transceiver means of the first device may comprise a transmitter for transmitting further light (optionally at a second wavelength or wavelength range) representing the optical wireless communication signal.

[0023] The transceiver arrangement of the first device may include a transmitter-side processing circuit for generating an optical wireless communication signal for transmission by the transmitter.

[0024] The transceiver means of the first device may comprise multiplexer means arranged to receive optical wireless communication signals from a plurality of signal paths and pass the signals to the transmitter for transmission.

[0025] The transceiver device of the first apparatus may comprise a controller for controlling the operation of the transceiver device of the first apparatus.

[0026] The first signal path to the multiplexer device may be from the transmitter side processing circuit;

[0027] The second signal path to the multiplexer device may come from the receiver side.

[0028] The controller may control operation of the transceiver arrangement to retransmit at least a portion of an optical wireless communication signal received by the receiver from one other device via the multiplexer arrangement to the transmitter, for example, to indicate to further other devices of the plurality of other devices that the optical channel of the receiver is busy.

[0029] The optical wireless communication signals may be in the form of or represented by electrical signals.The received light and the transmitted light may include light modulated to carry or represent the respective optical wireless communication signals.

[0030] The first device may include an access point (AP), and the other devices may include stations (STA).

[0031] The multiplexer device may include a single multiplexer. The multiplexer device may include a single device or multiple separate devices. The multiplexer device may include one or more switches, for example controlled by a controller. Each switch may be connected to a corresponding signal path leading to the multiplexer device. The switch may connect the signal path to one or more common outputs.

[0032] The transceiver of the first device may include at least one wavelength conversion component, which is, for example, arranged to cause at least a portion of the received optical wireless signal retransmitted by the transmitter to be retransmitted at a wavelength or wavelength range different from the wavelength or wavelength range of the optical wireless signal received by the receiver.

[0033] The wavelength conversion component can be configured to convert from infrared to visible wavelengths and vice versa.

[0034] Passing at least a portion of a received optical wireless communication signal to a transmitter for retransmitting may include processing the at least a portion of the received optical wireless communication signal to produce a processed signal and / or a representation of at least a portion of the received optical wireless communication signal, and retransmitting may include sending the processed signal and / or representation by the transmitter.

[0035] The processed signal and / or representation may comprise a noise signal and / or an encoded or scrambled representation of the at least part of the received optical wireless communication signal.

[0036] The system may further comprise at least one of an encryption system, a scrambler or a noise generating device arranged to process said at least a portion of the received optical wireless communication signal.

[0037] The transceiver of the first device may be configured to process the received optical wireless communication signal such that the at least a portion of the received optical wireless signal is to be retransmitted on a channel different from the channel on which the receiver of the first device received it.

[0038] The receiver side processing circuit may include a series of receiver side processing components that perform a series of operations on the received optical wireless communication signal, and the second signal path to the multiplexer device comes from a branch point on the receiver side before at least one subsequent receiver side component.

[0039] The receiver side processing circuit can be configured to separate the received optical wireless communication signals at the branch point so that the received optical wireless communication signals are all sent to the multiplexer device along the second signal path and to at least one of the subsequent receiver side components.

[0040] The branch point may include a splitter and / or a switching device. The controller may be configured to control the operation of the branch point, such as the splitter and / or the switching device, to determine whether to send the optical wireless communication signal to one of the second signal paths to the multiplexer device, both, neither, or not to at least one of the subsequent receiver-side components.

[0041] The branching point may be arranged such that at least a portion of the optical wireless communication signal is at least partially decoded or otherwise processed, optionally by receiver-side processing circuitry, and optionally simultaneously retransmitted by a transmitter of the first device.

[0042] The controller may be configured to control at least one operation of the multiplexer arrangement, the splitting of the received optical wireless communication signal at the branching point and / or in the transmitter of the first device.

[0043] Said controlling may be dependent on the result of said decoding or other processing of the received optical wireless communication signal.

[0044] The decoding or other processing of the received optical wireless communication signal may include determining an identifier that identifies the device or group of devices from which the optical wireless signal is received. Control of at least one of the multiplexers, separation of the received optical wireless communication signal at a branch point and / or control of the transmitter is performed based on the identifier.

[0045] The identifier may include a pseudo-noise (PN) sequence, and / or decoding or other processing may be performed without or before decoding a frame associated with the identifier.

[0046] The system may be configured to perform said resending in response to the determined identifier matching or associating with a stored identifier.

[0047] The system may be configured to transmit the processed signal and / or representation by the transmitter in response to the determined identifier matching the stored identifier.

[0048] The controller may be configured to perform at least one action in response to a result of decoding or otherwise processing at least part of the received optical wireless communication signal, the at least one action comprising at least one of the following:

[0049] a) continuing to resend the received optical wireless communication signal by the transmitter of the first device;

[0050] b) stopping the retransmission of the received optical wireless communication signal by the transmitter of the first device;

[0051] c) The optical wireless communication signal of the first device is sent by the transmitter of the first device, and the optical wireless communication signal is sent from the transmitter-side processing circuit to the multiplexer device via the first signal path.

[0052] The controller may be configured to control the operation of the transceiver device to control at least one of the following:

[0053] d) if the at least partial decoding or other processing of the received optical wireless communication signal indicates that the optical wireless communication signal is intended for the first device, performing at least one of the following: continuing the decoding or other processing of the signal; ceasing to retransmit the received optical wireless communication signal by the transmitter of the first device; starting to transmit the optical wireless communication signal by the transmitter of the first device;

[0054] e) continuing to retransmit the signal by the transmitter if the at least partial decoding or other processing of the optical wireless communication signal received from another device of the plurality of other devices indicates that the optical wireless communication signal is intended for another other device or an alternative other device;

[0055] f) ceasing said at least partial decoding or other processing of the received optical wireless communication signal, and ceasing retransmission of the received optical wireless communication signal by a transmitter of a transceiver of the first device.

[0056] The controller can be configured to control the operation of the transceiver device of the first device so that if the at least partial decoding or other processing of the received optical wireless communication signal indicates that the optical wireless communication signal is for the first device, the retransmission of the received optical wireless communication signal by the transmitter of the first device is stopped, the optical wireless communication signal of the first device is retransmitted by the transmitter of the first device, and if the duration of the optical wireless communication signal of the first device is less than the duration of the received optical wireless communication signal, the retransmission of the received optical wireless communication signal is resumed after the transmission of the optical wireless communication signal of the first device is completed.

[0057] The received optical wireless communication signal may be an uplink signal, and at least one of the optical wireless communication signals generated by the transmitter-side processing circuitry includes a downlink signal transmitted in response to the uplink signal.

[0058] The uplink signals and the downlink signals may comprise or form part of a signal exchange between a first device and another device among a plurality of other devices, for example the first device establishing or forming part of a channel busy period during which an optical wireless communication channel from the first device is reserved for the other devices and is excluded for use by further other devices.

[0059] The uplink signal and the downlink signal may include or form part of a handshake procedure.

[0060] The system may further include an envelope detector arranged to receive the optical wireless communication signal from the transmitter side processing circuit. The operation of the multiplexer device and / or the transmitter may depend on the output of the envelope detector. The multiplexer device and / or the transmitter may be configured to switch between retransmitting the received optical wireless communication signal and transmitting the optical wireless communication signal from the transmitter side processing circuit according to the output of the envelope detector.

[0061] The envelope detector may be located on said first signal path leading to the multiplexer means, or may be on another signal path leading to the multiplexer means.

[0062] The second signal path to the multiplexer arrangement may be arranged such that the optical wireless communication signal received by the receiver of the first device is passed to the multiplexer arrangement in analogue form and / or without analogue to digital conversion.

[0063] The second signal path may be arranged such that, in operation, received optical wireless communication signals are passed both to the receiver side processing circuitry and to the multiplexer arrangement.

[0064] The second signal path may comprise at least one optical component arranged to direct light representing the optical wireless communication signal from the receiver side along the signal path.

[0065] The system may further comprise a further receiver on said second signal path, configured to convert said directed light into a corresponding electrical signal, optionally for provision to a multiplexer arrangement.

[0066] The system may also include at least one optical component configured to reflect or otherwise direct at least a portion of the received light representative of the optical wireless communication signal in a desired direction.

[0067] At least one optical component is configured to reflect or otherwise direct at least some of the received light toward at least one, and optionally each, of the other devices.

[0068] The at least one optical component comprises a mirror, optionally a convex mirror.

[0069] The transceiver arrangement of the first device may be configured to retransmit the received optical wireless communication signal in whole or in part only if the transmitter is not busy transmitting the optical wireless communication signal from the transmitter-side processing circuitry.

[0070] The optical wireless communication signal received at the receiver may include or represent at least one packet.

[0071] The transceiver of the first device may be configured to retransmit the received optical wireless signal substantially in whole or in part using the transmitter without substantially modifying the content of the at least one packet.

[0072] The or each packet may comprise or represent at least one header comprising an address or identifier of another device or other device from which the optical wireless packet is transmitted. The transceiver may be configured to retransmit the at least one header comprising the address or identifier using the transmitter.

[0073] The group or at least one of the groupings comprises at least a first part and a second part, wherein at least one of g), h), i), j), k):

[0074] g) the first part has a lower bit rate and the second part has a higher bit rate;

[0075] h) the first part has a higher bit rate and the second part has a lower bit rate;

[0076] i) the first portion includes a preamble and / or a packet header, and the second portion includes at least a portion of a packet payload;

[0077] j) The first part includes information for identifying the intended recipient, optionally a MAC header;

[0078] k) the first part includes information for identifying the intended recipient, optionally a MAC header;

[0079] The or each packet may have a packet structure in accordance with an OWC communication protocol, optionally a LiFi protocol.

[0080] The controller may be configured to control the operation of the transceiver device of the first apparatus such that at least one of l) or m):

[0081] l) the transmitter of the first device retransmits a selected portion of the received wireless communication signal from the second signal path, and in response to the retransmission of the selected portion being completed, the transmitter of the first device transmits or makes available for transmission of the signal from the first signal path;

[0082] m) The transmitter of the first device retransmits a selected portion of the received wireless communication signal from the second signal path for a period of time, and in response to completion of the period of time, the transmitter of the first device transmits or makes available for transmission of the signal from the first signal path.

[0083] The time period may be less than or equal to 40 milliseconds, optionally less than or equal to 20 milliseconds, optionally between 0.01 milliseconds and 40 milliseconds, optionally between 0.01 milliseconds and 40 milliseconds.

[0084] The other devices may be configured such that the other devices sending the optical wireless transmission signal retransmitted by the transmitter of the first device disable at least one component of their receiver or receiver-side processing circuitry, for example, to prevent receiving their own packets, during at least a portion of the time period in which the first device retransmits the optical wireless transmission signal.

[0085] The other device enables its receiver or at least one component of the receiver-side processing circuit to receive the optical wireless communication signal of the first device.

[0086] The plurality of other devices may be configured to disable at least one component of their transmitter or transmitter-side processing circuitry, or defer transmission, during at least a portion of a time period in which the channel is busy with transmissions between the first device and another device among the plurality of other devices, whose optical wireless communication signals are received by the first device.

[0087] Each of the plurality of other devices may be configured to determine whether to disable the at least one component or defer transmission based on processing of at least a portion of the optical wireless communication signal received from the first device from the retransmission process.

[0088] The processing may include an energy detection process and / or noise detection, detection of a scrambled signal or at least partial decryption of an encrypted signal.

[0089] Each of the plurality of other devices may determine the duration of the channel busy period based on decoding of the retransmitted optical wireless communication signal of the first device and / or at least a portion (optionally a header) of the transmitted optical wireless communication signal.

[0090] The decoding by another of the plurality of other devices may include determining a length or type of a packet.

[0091] Each of the plurality of other devices may be configured to receive and decode at least a portion of the retransmitted optical wireless communication signal and selectively enable or disable at least one component of its transmitter or transmitter-side processing circuitry, or postpone or initiate transmission, or continue or stop decoding or other processing, depending on the retransmitted optical wireless communication signal.

[0092] The at least a portion of the retransmitted optical wireless communication signal may include at least one of a preamble, a header, and a lower bit rate portion.

[0093] The first device may be configured to transmit a polling signal in a contention-free period to poll a plurality of other devices. Upon receiving a received optical wireless communication signal from one of the other devices during the transmission of the polling signal during the contention-free period, the transceiver device of the first device may be configured to complete the transmission of the polling signal and then, if the duration of the optical wireless communication signal is longer than the polling signal, retransmit the remaining portion of the optical wireless communication signal.

[0094] One of the other devices sending the retransmitted optical wireless communication signal may be configured to keep its receiver in an enabled state during reception of the polling signal and to disable at least one component of its receiver or receiver-side processing circuitry during retransmission of the remainder of the optical wireless communication signal.

[0095] An interframe spacing used for transmission by the first device may be shorter than an interframe spacing used for transmission by a plurality of other devices.

[0096] The transceiver means of the first device may comprise further circuitry between the multiplexer means and the transmitter, the further circuitry optionally being configured to perform at least one process to prepare the optical wireless communication signal for transmission by the transmitter.

[0097] The system may include at least one amplifier in the second signal path.

[0098] The optical wireless communication system may include a full-duplex communication system or a half-duplex communication system.

[0099] The optical wireless communication system may operate according to an OWC communication protocol (optionally a LiFi communication protocol).

[0100] The first wavelength or wavelength range may be different from the second wavelength or wavelength range.

[0101] The first wavelength or wavelength range includes one of infrared, visible or ultraviolet wavelengths, and the second wavelength or wavelength range includes one of infrared, visible or ultraviolet wavelengths.

[0102] The first device may be fixed at a fixed position. The first device may be portable. At least one (optionally, each) other device may be portable. At least one (optionally, each) other device may be fixed at a fixed position. The first device and the other device may be STAs. The first device and at least one (optionally, each) other device may be APs.

[0103] In another aspect that may be provided independently, there is provided a transceiver device of a first device, configured to communicate with a plurality of other devices via at least one optical channel, the transceiver device comprising:

[0104] a receiver for receiving light (optionally at a first wavelength or range of wavelengths) representing optical wireless communication signals transmitted by a plurality of other devices, the receiver comprising at least one photodetector;

[0105] a receiver-side processing circuit for processing the optical wireless communication signal received by the receiver to extract data represented by the received optical wireless communication signal;

[0106] a transmitter for transmitting light (optionally at a second wavelength or wavelength range) representing the optical wireless communication signal;

[0107] A transmitter-side processing circuit for generating an optical wireless communication signal for transmission by the transmitter;

[0108] a multiplexer device arranged to receive optical wireless communication signals from a plurality of signal paths and pass the signals to a transmitter for transmission; and

[0109] A controller for controlling the operation of the AP transceiver device, wherein

[0110] A first signal path to the multiplexer device is from a transmitter side processing circuit;

[0111] The second signal path to the multiplexer device is from the receiver side; and

[0112] The controller controls operation of the transceiver arrangement to retransmit at least a portion of an optical wireless communication signal received by the receiver from one of the plurality of other devices via the multiplexer arrangement to the transmitter to indicate to other of the plurality of other devices that the receiver's optical channel is busy.

[0113] In another aspect that may be provided independently, a transceiver device of a further device is provided, the transceiver device being configured to communicate with a first device or at least one further device via at least one optical channel, the transceiver device of the further device comprising:

[0114] a receiver for receiving light (optionally having a first wavelength or range of wavelengths) representing an optical wireless communication signal, the receiver comprising at least one photodetector;

[0115] a receiver-side processing circuit for processing the optical wireless communication signal received by the receiver to extract data represented by the received optical wireless communication signal;

[0116] a transmitter for transmitting light (optionally at a second wavelength or wavelength range) representing an optical wireless communication signal;

[0117] a transmitter-side processing circuit for generating an optical wireless communication signal for transmission by the transmitter; and

[0118] A controller for controlling the operation of the transceiver device, wherein

[0119] The controller is configured to partially decode the received optical wireless communication signal and determine whether to stop or continue decoding the optical wireless communication signal and / or send or postpone sending other optical wireless communication signals according to the result of the partial decoding.

[0120] In another aspect that may be provided independently, there is provided a method of operating an optical wireless communication system, the system comprising:

[0121] A first device comprising a transceiver apparatus; and

[0122] a plurality of other devices, each of which comprises a respective other transceiver device, wherein

[0123] The first device is configured to communicate with a plurality of other devices via at least one optical channel, the transceiver device of the first device comprising:

[0124] a receiver for receiving light (optionally at a first wavelength or range of wavelengths) representing an optical wireless communication signal transmitted by another device, the receiver comprising at least one photodetector;

[0125] a receiver-side processing circuit for processing the optical wireless communication signal received by the receiver to extract data represented by the received optical wireless communication signal;

[0126] a transmitter for transmitting light at a second wavelength or range of wavelengths and representing an optical wireless communication signal; and

[0127] The transmitter side processing circuit is used to generate an optical wireless communication signal for the transmitter to send,

[0128] The method further includes:

[0129] An optical wireless communication signal is received by a receiver of the first device, and a determination is made whether all or part of the optical wireless communication signal is to be retransmitted by a transmitter of the first device, or whether other optical wireless communication signals are to be transmitted by the transmitter of the first device, depending on data encoded by at least a portion of the optical wireless communication signal.

[0130] The method may include retransmitting, by a transmitter of the first device, a portion of the optical wireless communication signal, wherein the determining includes determining whether to retransmit other portions of the received optical wireless communication signal based on the encoded data.

[0131] In another aspect of the present invention, which may be provided independently, there is provided an optical wireless communication system, comprising:

[0132] A first device comprising a transceiver apparatus; and

[0133] a plurality of other devices, each of which comprises a respective other transceiver device, wherein

[0134] The first device is configured to communicate with a plurality of other devices via at least one optical channel, the transceiver device of the first device comprising:

[0135] a receiver for receiving light (optionally at a first wavelength or range of wavelengths) representing an optical wireless communication signal transmitted by another device, the receiver comprising at least one photodetector;

[0136] a receiver-side processing circuit for processing the optical wireless communication signal received by the receiver to extract data represented by the received optical wireless communication signal;

[0137] a transmitter for transmitting light (optionally at a second wavelength or wavelength range) representing the optical wireless communication signal;

[0138] A transmitter-side processing circuit for generating an optical wireless communication signal for transmission by the transmitter;

[0139] at least one optical component for reflecting or directing at least some light received from at least one other device toward at least one, or optionally each, other device;

[0140] A controller is used to control the operation of the transceiver device of the first device.

[0141] Reflection or other directing of light by the at least one optical component may be such as to indicate to the at least one other device (and further optionally each other device) that the receiver's optical channel is busy.

[0142] The controller may be configured to monitor whether light representing an optical wireless communication signal is received, and to control operation of the transceiver arrangement of the first device such that the transmitter transmits the further light in dependence on the monitoring, for example so as to transmit the further light in response to no light representing an optical wireless communication signal being received.

[0143] The controller of the other device may be configured to determine whether to send or defer sending the further optical wireless communication signal depending on whether light representing the optical wireless communication signal is received from the at least one optical element of the first device (eg by reflection).

[0144] In another aspect of the present invention which may be provided independently, there is provided a transceiver device of a first device, the transceiver device being configured to communicate with a plurality of other devices via at least one optical channel, the transceiver device comprising:

[0145] a receiver for receiving light (optionally at a first wavelength or range of wavelengths) representing an optical wireless communication signal transmitted by another device, the receiver comprising at least one photodetector;

[0146] a receiver-side processing circuit for processing the optical wireless communication signal received by the receiver to extract data represented by the received optical wireless communication signal;

[0147] a transmitter for transmitting further light (optionally at a second wavelength or wavelength range) representing the optical wireless communication signal;

[0148] A transmitter-side processing circuit, used to generate an optical wireless communication signal for transmission by the transmitter;

[0149] at least one optical component for reflecting or directing at least some light received from at least one other device toward at least one of the other devices, and optionally each of the other devices;

[0150] A controller is used to control the operation of the transceiver device of the first device.

[0151] In another aspect that may be provided independently, there is provided a method of operating an optical wireless communication system, the system comprising:

[0152] A first device comprising a transceiver apparatus; and

[0153] The method further comprises:

[0154] receiving, by the transceiver means of the first device, light representing the optical wireless communication signal,

[0155] reflecting or otherwise directing at least some of the received light to at least one, and optionally each, of the other devices,

[0156] monitoring reception of said light representing an optical wireless communication signal,

[0157] Based on said monitoring, operation of the transceiver means of said first device is controlled to transmit further light representing further optical wireless communication signals.

[0158] Reflection or other directing of light by the at least one optical component may be such as to indicate to the at least one other device (and further optionally each other device) that the receiver's optical channel is busy.

[0159] Depending on the monitoring, the further transmitting may include transmitting the further light in response to light received by the transceiver ceasing or not occurring.

[0160] Features in one aspect may be provided as features in any other aspect in any appropriate combination. For example, any one of the system, apparatus, method, or computer program product features may include any other of the system, apparatus, method, or computer program product features. BRIEF DESCRIPTION OF THE DRAWINGS

[0161] Various aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0162] Figure 1 is a schematic diagram of a simple LiFi network with an access point (AP) 2 capable of communicating with two different stations 4, 6 via optical wireless communication;

[0163] Figure 2 is a block diagram showing the principle of optical wireless communication (OWC) according to an embodiment;

[0164] Figure 3 is a schematic diagram of a transceiver device of an AP according to one embodiment;

[0165] Figure 4 is a schematic diagram of a portion of a receiver-side processing chain of a transceiver device of an AP according to one embodiment;

[0166] Figure 5 is a schematic diagram of the grouping used in the embodiment;

[0167] Figure 6 is a schematic diagram of a transceiver device of an AP according to another embodiment;

[0168] Figure 7 is a timing diagram schematically showing the Figure 3 An optical wireless communication method performed by an embodiment of the present invention;

[0169] Figure 8 is a timing diagram schematically showing the contention-free period. Figure 3 An optical wireless communication method performed by an embodiment of the present invention;

[0170] Fig. 9 is a flow chart showing that, for example, during a contention period Figure 3 An overview of the processes performed by the system; and

[0171] Fig.10 is a schematic diagram of a transceiver device of an AP according to another embodiment. DETAILED DESCRIPTION

[0172] The term "light" herein may be used, for example, to refer to electromagnetic waves having wavelengths in the range of 1 nm to 2500 nm, which include ultraviolet, visible, and near infrared wavelengths. Light may be used to refer to visible and non-visible light of any suitable wavelength.

[0173] The embodiments described below relate to a LiFi system, but alternative embodiments may be applicable to implementations of any suitable OWC system or protocol.

[0174] Figure 2 is a block diagram illustrating the principle of optical wireless communication (OWC) according to an embodiment. Figure 2 An AP 10 including a transmitter / receiver device is shown, and also includes stations (STAs) 14a-14c of the transmitter / receiver devices. The transmitter device of the AP 10 is configured to send wireless information to the receiver devices of the STAs 14a-14c via optical communication channels 12a, 12b, wherein the information is encoded via the optical communication channels 12a, 12b. The optical communication channels 12a, 12b may be free space communication channels. The optical communication channels 12a, 12b have characteristic optical wavelengths.

[0175] exist Figure 2 A bidirectional communication from the AP to one of the STAs 14a is schematically shown in FIG. In the described embodiments and in many OWC protocols, such as the LiFi protocol, simultaneous bidirectional communication, also referred to as full-duplex communication, is possible. Figure 2 In the embodiment of the present invention, the AP 10 uses optical channels of different wavelengths for transmission and reception.

[0176] A free space communication channel involves the transmission of optical signals through air, space, a vacuum, a liquid (eg, water), or the like.

[0177] The transmitter and / or receiver can be provided on different devices, including Figure 2 Access points and stations are shown. An access point can provide access to another network (e.g., the Internet). Stations can be portable or fixed. Examples of stations include, but are not limited to, personal computers, desktops, portable computers, and smart devices, including mobile devices (e.g., mobile phones, tablets, or digital book readers). Portable stations can be powered by their own battery resources.

[0178] Access points can provide access to and / or from a wired network or WiFi TM Or data transmission of other wireless networks and / or other optical wireless communication networks (optionally LiFi networks).

[0179] The transmitter device of the AP 10 and the STA 14a-14c includes a light emitting diode (LED), a laser or other suitable light source, and an associated driving circuit to drive the LED or laser to generate an optical signal. The associated driving circuit includes a digital-to-analog converter configured to provide a modulated signal with a frequency characteristic of the optical communication signal. Another processor provided as part of the transmitter device or associated with the transmitter device modulates the data onto a driving current, and the driving circuit provides the driving current to the LED or laser. The LED or laser then generates a modulated light having a modulation, which represents an output optical wireless communication signal carrying the data.

[0180] The receiver devices of the AP 10 and STAs 14a-14c include photodiodes or other suitable light detectors with associated circuitry to condition any received signals. The photodiodes convert the received light into electronic signals, which are then conditioned by conditioning circuitry. Conditioning may include one or more filtering steps; amplification of weak electrical signals; equalization of received signals, and conversion of analog signals to digital signals using analog-to-digital converters. The digital signals may then be provided to other processors, provided as part of or associated with the receiver device, to extract the communication data.

[0181] Any suitable modulation scheme may be used. For example, in some embodiments an orthogonal frequency division multiplexing (OFDM) modulation scheme is used, and the demodulation is from the OFDM modulation scheme. In other embodiments, but not limited to, other modulation schemes may be used, such as on-off keying (OOK), phase shift keying (PSK), M-ary pulse amplitude modulation (M-PAM), M-ary quadrature amplitude modulation (M-QAM), discrete Hartley transform, wavelet packet division multiplexing (WPDM), Hadamard coded modulation (HCM), pulse position modulation (PPM), color shift keying (CSK), carrier-less amplitude and phase (CAP), or discrete multi-tone (DMT). The light may be modulated at a modulation rate between 1 kHz and 1 PHz, for example, at a modulation rate between 1 MHz and 100 GHz.

[0182] The modulation scheme may form part of the OWC communication protocol, such that the optical signal is generated in accordance with the OWC communication protocol.The OWC communication protocol may be packet-based.

[0183] Figure 3 2 is a schematic diagram of a transceiver device 20 of the AP 10 according to an embodiment. For the sake of brevity, the transceiver device 20 may also be referred to as a transceiver 20.

[0184] The AP transceiver device 20 includes an AP receiver 22 in the form of a photodetector and any suitable one or more light emitting devices, such as an AP transmitter 24 in the form of one or more LEDs or lasers. As described above, according to an embodiment, the photodetector may include a photodiode or any other suitable light detector, and the AP transmitter may include a light emitting diode (LED), a laser or any other suitable light source. The photodetector may be, for example, any of a PIN diode, an avalanche photodiode (APD), a silicon photomultiplier (SiPM), or a similar device. Although referred to as a photodetector, the photodetector may be a single photodetector or a plurality of photodetectors. In some embodiments, a plurality of photodetectors are arranged in an array or matrix.

[0185] The AP transceiver device 20 includes AP receiver-side processing circuitry for processing optical wireless communication signals received by the AP receiver 22 to extract data represented by the received optical wireless communication signals.

[0186] The receiver-side processing circuit includes a series of receiver-side processing components that perform a series of operations on the received optical wireless communication signals.

[0187] In this embodiment, the chain of receiver-side processing components includes an amplifier stage 26 connected to the output of the photodetector 22. The combination of the amplifier stage 26 and the photodetector 22 may be referred to as an optical front end 23.

[0188] The amplifier stage 26 is connected to the other physical layer, namely stage 28. In the present embodiment, the other stage 28 provides baseband processing resources configured to receive the amplified optical wireless communication signal from the amplifier stage 26 and extract data from the signal.

[0189] exist Figure 3 In the embodiment of FIG. 5 , the other stages 28 include a high speed analog-to-digital converter (ADC) 32 and a demodulator 34 . Figure 4 An ADC 32 and a demodulator 34 are shown, which is a more detailed schematic diagram of a portion of the receiver side processing chain.

[0190] exist Figure 4 In the system of FIG. 2 , the amplifier stage 26 includes a transimpedance amplifier (not shown), also known as a TIA, and a variable gain amplifier (not shown), also known as a VGA. The TIA is configured to convert the current signal from the photodetector 22 into a voltage signal. The TIA can be combined or integrated into the photodetector 26 itself. The VGA is configured to adjust the voltage signal from the TIA so that the voltage signal input to the ADC 32 is as close as possible to the maximum input range of the ADC 32. The VGA prevents clipping and minimizes the quantization noise introduced. In other embodiments, any suitable amplifier or combination of amplifiers can be used in the amplifier stage 26.

[0191] ADC 32 converts the input analog voltage into a digital signal. The digital signal includes digital samples with a fixed or variable sampling rate and a fixed or variable resolution. ADC 32 is used to convert signals that may include both low-speed portions and high-speed portions (e.g., a given packet may include both low-speed portions and high-speed portions). Therefore, ADC 32 is selected to have a sufficiently high speed to accommodate the highest expected data rate. Figure 4 In the example of , ADC 32 has a frequency between 500 MHz and 2 GHz. The sampling rate of ADC 32 is between 500 and 2,000 MSPS (mega samples per second). In alternative embodiments, any other suitable ADC or combination of ADCs may be used. The higher speed portion may be a portion of the packet having a higher bit rate, e.g., a bits / second (bps) value, than other portions of the packet (which may be referred to as a low speed portion). The higher speed packets or portions may include packets or portions representing an amount of data in a shorter duration, whereas the same amount of data would be represented by a lower speed packet or portion.

[0192] exist Figure 4 In the example shown, the ADC 32 has a 12-bit resolution.

[0193] The samples output by the ADC 32 are processed by the baseband demodulator 34 to demodulate and / or decode the signal to extract the data. For example, the data may include a plurality of data packets, each data packet including a respective preamble, header, and payload.

[0194] Any suitable signal format may be used, subject to the appropriate OWC protocol. Figure 3 In an embodiment of the present invention, the OWC communication signal represents a packet and Figure 5 The schematic diagram shows Figure 3 An example of the structure of packet 50 used in the embodiments.

[0195] Packet 50 includes a preamble 52 , a header 54 , and a payload 56 .

[0196] exist Figure 3 In an embodiment of the present invention, the preamble 52 includes a pseudo-noise (PN) sequence that can be decoded at a receiver to determine, for example, whether each of the subsequent header and payload includes higher speed (e.g., higher data rate) or lower speed (e.g., lower data rate) data, which can then be used by subsequent components in the receiver chain. In this embodiment, different packets or different parts of the same packet (e.g., preamble, header, payload) can be encoded at different data rates.

[0197] The header 54 may contain all the information necessary to demodulate the subsequent payload. Figure 3 In the embodiment of the present invention, the header is encoded using DCO-OFDM with 1 / 2FEC rate BPSK modulation, but any other suitable encoding scheme may be used. The header 54 may include, for example, address information indicating the device to which the packet is intended, such as one or more of the AP 10 or STAs 14a-14c.

[0198] The payload 56 is transmitted at whatever data rate the system may support.

[0199] It should be understood that although Figure 3 and Figure 4 Components of the receiver-side processing circuitry are schematically shown in FIG. 1 , but any other suitable components or combinations of components may be provided in alternative embodiments.

[0200] Turning to the transmitter side, Figure 3 The AP transceiver device 20 includes an AP transmitter-side processing circuit 30 for generating an optical wireless communication signal for transmission by the AP transmitter 24 .

[0201] The AP transmitter side processing circuit 30 includes circuitry that controls a light source to generate light that is modulated to represent a desired optical wireless communication signal. The circuitry may include a digital-to-analog converter (not shown) configured to provide a modulated signal over a frequency range characteristic of the optical wireless communication signal. Processing resources provided as part of or associated with the transmitter side processing circuit 30, such as a suitably programmed processor, provide an optical wireless communication signal representing data that is used to modulate a drive current provided to the light source of the transmitter 24. The light source then generates an output light signal carrying the optical wireless communication signal. The light source may include various power supply circuits that power the operation of the light source of the transmitter 24. Modulation of the drive current to represent the desired optical wireless communication signal may be performed using any known OWC technique.

[0202] In an embodiment, any suitable AP transmitter-side processing circuitry 30 may be used, such as any transmitter-side processing circuitry 30 for providing a suitably modulated signal according to the Li-Fi protocol or other OWC communication protocol.

[0203] Figure 3 The embodiment of the present invention is characterized in that a multiplexer 36 is provided between the AP transmitter side processing circuit 30 and the AP transmitter 24 in the form of an LED or other light source. Multiple signal paths lead to the multiplexer 36, a first signal path goes from the AP transmitter side processing circuit 30 to the multiplexer 36, and a second signal path goes from a branch point 40 on the receiver side to the multiplexer 36, such as Figure 3 In some embodiments, one or more amplifiers 39 are provided on the second signal path between the branch point 40 and the multiplexer 36.

[0204] In alternative embodiments, any suitable multiplexer means may be provided, and may for example be in the form of a single device or a plurality of devices.In some embodiments, the multiplexer arrangement may comprise a switch or a plurality of switches.

[0205] The AP transceiver device also includes a controller 38, which Figure 3 38 is shown in the form of a suitably programmed CPU. In other embodiments, the controller 38 may have any other suitable form, such as software, hardware, or a combination of software and hardware. In various embodiments, the controller 38 may be implemented as a single component, or as multiple components in a single location, or as multiple components distributed in multiple locations (e.g., included in a transmitter and / or receiver).

[0206] Figure 3The controller 38 in the embodiment of the embodiment is operable to control whether the signal from the first signal path (e.g., the AP optical wireless communication signal from the transmitter-side processing circuit) and / or the signal from the second signal path (e.g., the optical wireless communication signal received at the AP receiver 22) is sent to the transmitter 24 for transmission or retransmission by the AP. In some cases, the controller 38 can also prevent the signals from the first and second signal paths from being sent to the transmitter.

[0207] In various embodiments, the controller 38 is configured to directly control the operation of the multiplexer and / or control the operation of any other components of the AP transceiver device 20 to control which signals are sent to the transmitter 24 for transmission or retransmission.

[0208] In some embodiments, the controller 38 is also operable to control whether the optical wireless communication signals are sent to other components of the AP transceiver, and to control the encoding, decoding or other processing of the optical wireless communication signals, in whole or in part, on the receiver or transmitter side, and optionally, the timing of such processing.

[0209] exist Figure 3 In the embodiment of the present invention, the branch point 40 is shown as a simple split in the signal path between the amplifier stage 26 and the other stages 28, which provides baseband signal processing resources for performing analog-to-digital conversion and data extraction. In some embodiments, the branch point does provide such a simple split, so that all received optical wireless communication signals are sent to the other stages 28 and the multiplexer 36 of the receiver side processing chain. However, in some embodiments, the branch point 40 includes or is associated with a splitter and / or switching device that is operable under the control of the controller 38 to determine whether the received optical wireless communication signal is sent to one or both of the multiplexer 36 and the other stages 28 of the receiver side processing chain. For clarity, in Figure 3 Controller 38 is schematically shown as being linked only to multiplexer 36, but it should be understood that, depending on the embodiment, controller 38 may be directly or indirectly linked or otherwise communicate with and / or control any component of the AP.

[0210] A feature of the embodiment is that, by providing a signal path from the receiver side to the transmitter 24, an optical wireless communication signal received by the receiver 22 from one of the STAs 14a can be retransmitted by the transmitter of the AP 10 to another STA 14b, 14c, thereby providing a fast and efficient technique to indicate to the other STAs 14b, 14c that the optical channel of the STA receiver is busy communicating with the STA 14a, or providing a fast and efficient technique to relay the received signal to the other STAs.

[0211] exist Figure 3 In the embodiment of the present invention, the branching point is before the ADC 32 in the processing chain on the receiver side, so when the received optical wireless communication signal is passed to the transmitter 24 via the multiplexer 36, it is still in analog form. Passing the received optical wireless communication signal to the transmitter 24 in analog form for retransmission without A to D conversion can make it possible to use the received optical wireless communication signal as a busy signal particularly quickly and efficiently, or to relay the optical wireless communication signal particularly quickly and efficiently with minimal latency.

[0212] In an alternative embodiment, the branching point is after the ADC 32 and the received optical wireless communication signal is in digital form when it is passed to the transmitter side for processing and passed to the transmitter for retransmission. In such an embodiment, the digital-to-analog conversion and any other processes that produce the modulation of the transmitter current are then performed on the transmitter side. Examples of such embodiments are shown in FIG. Figure 6 It is schematically shown in FIG.

[0213] Depending on the OWC communication protocol used, the AP receiver 22 is typically sensitive to light having a wavelength different from the wavelength of light sent by the transmitter 24, especially if the system provides full-duplex communication. Figure 3 In an embodiment, the photodetector of AP receiver 22 is sensitive to infrared light, and transmitter 24 transmits visible light. In alternative embodiments, any suitable wavelength of light may be used for the uplink or downlink, for example, in some embodiments, different wavelengths of infrared light may be used for the uplink and downlink.

[0214] The photodetector of the AP receiver 22 outputs a signal that represents the amplitude of light at the operating wavelength or wavelength range of the photodetector (in this case, one or more infrared wavelengths). Constant amplitude infrared light will produce a DC electrical signal at the photodetector. Figure 3In an embodiment, the received IR signal is amplitude modulated with the optical wireless communication signal, so that the electrical signal output by the photodetector is actually the optical wireless communication signal without any other down-conversion of the electrical signal output by the photodetector. Similarly, when the optical wireless communication signal is passed via the branch point and multiplexer 36 to modulate the drive current of the light source of the transmitter 24, no up-conversion of the optical wireless communication signal is required. Therefore, the configuration and characteristics of the light source and the photodetector are such that the optical wireless communication signal received at a first wavelength or wavelength range (e.g., one or more infrared wavelengths) is retransmitted at a second different wavelength or wavelength range (e.g., a visible wavelength). Effectively, the light source and the photodetector and associated circuitry act as a wavelength conversion component so that at least a portion of the received optical wireless signal retransmitted by the transmitter will be retransmitted at a wavelength or wavelength range different from the wavelength or wavelength range received by the receiver. In other embodiments, additional wavelength conversion components may be provided.

[0215] Discuss Now Figure 3 In various operating modes of embodiments of the present invention, the AP 10 uses retransmission of optical wireless communication signals received from one of the STAs 14a to provide an indication to the other STAs 14b, 14c that the optical channel of the STA receiver is busy.

[0216] Figure 7 is a timing diagram schematically showing the Figure 2 and 3 An optical wireless communication method is performed by an embodiment of the present invention.

[0217] Figure 7 The horizontal axis represents time. Figure 7 The vertical axis of is divided into three parts, which respectively represent the signals sent and received by the access point AP 10, the first STA 14a (referred to as STA1) and the second STA 14b (referred to as STA1) from top to bottom.

[0218] The signal is represented in the form of packets by shaded or transparent boxes, which are located on the horizontal axis according to time and the vertical axis according to the device from the transmitting to the receiving device. The shaded box represents a packet or a portion of a packet originating from one of the STAs 14a, 14b, and the blank box represents a packet or a portion of a packet originating from the AP 10.

[0219] For each of the three sections, the box below the horizontal axis of the section represents the signal received at the receiver of the device of the section (e.g., the receiver of the AP, STA1, or STA2), and the box above the horizontal axis of the section represents the signal transmitted by the transmitter of the device of the section (e.g., the transmitter of the AP, STA1, or STA2). Figure 7In the , the letters ND, PD, and FD are used to indicate whether a packet is undecoded, partially decoded, or fully decoded.

[0220] The sending / receiving of three different signals (packet 1, packet 2, and packet 3) is as follows: Figure 7 shown.

[0221] For group 1, group 2 and group 3, Figure 7 The timing diagram representation method is also shown in Fig. 9 , which generally represents the processing performed by each of the AP 10, STA1 14a and STA2 14b, for example, during a contention period.

[0222] about Figure 7 The process shown in FIG. 1 shows that the uplink packet 60 (packet 1) sent by STA1 14a has a duration (Δt 1) longer than the downlink packet 62 sent by AP 10 in response. 1 )Short duration situations.

[0223] STA 1 sends uplink packet 60 (packet 1) ( Fig. 9 92 of the embodiment of the present invention). The AP did not transmit, therefore, the uplink packet 60 (packet 1) is retransmitted by the AP after receipt (stage 94). STA 1 has disabled its own receiver (stage 96) until the predicted time of the downlink packet 62 because it does not want to receive its own packet 60 or packet fragments. AP 10 decodes the header portion 60a of the uplink packet 60 (packet 1), optionally the low-speed portion of the packet, and discovers that it is the recipient (stage 102). Therefore, it continues to decode packet 1 and also starts to send downlink packets 62 to STA 1 (stage 106). STA 2 also receives the first part 60a of packet 60 (packet 1) and knows after decoding the low-speed portion (stage 116) that the channel is busy and / or is busy for at least the duration of the uplink packet 60 (packet 1) (stage 112). In the described embodiment, the header includes information indicating the amount of data (e.g., number of bytes) in the packet and / or in different parts of the packet (e.g., header, payload) and the modulation and coding scheme (MCS) used in the packet. This information can be used to determine the duration of the packet or payload.

[0224] In this case, after uplink packet 60 (packet 1) ends, downlink packet 62 continues. STA 214b detects that the channel is still busy and will not attempt to send any packets until downlink packet 62 to STA 1 has completed and the subsequent interframe time has passed.

[0225] Turn to Figure 7Considering Packet 2 in the timing diagram of , this indicates that the AP packet (e.g., downlink packet 68) has a shorter duration (Δt ) than the duration of the uplink packet 66 (Packet 2) sent from the station (STA1 14a). 2 ) situation.

[0226] Packet 66 (packet 2) is another uplink packet sent by STA1 14a (stage 92) and is intended for AP10. In this case, a downlink packet 68 (stage 94) from AP 10, sent in response to AP 10 decoding header 66a of packet 66, is shorter than uplink packet 66. After AP 10 completes transmission of downlink packet 68, multiplexer 36 switches back to its default position so that the AP resumes resending uplink packets from STA 1 (stage 114). Thus, in this case, the AP resends both parts 66a, 66c of uplink packet 66, and in the time period between resending the two parts 66a, 66c of the uplink packet, it sends (stage 106) a downlink packet 68 intended for STA1 14a. STA2 is able to determine that the channel is busy based on receipt and decoding of header 66a of the resent uplink packet 66 (stages 116, 122). In this example, as Figure 7 As shown, STA2 is able to determine the minimum duration that the channel is busy by decoding the header 66a of the retransmitted uplink packet 66, and in this case, STA2 14b does not decode subsequent received data (eg, 68 and 66c) during this period (stage 122).

[0227] exist Figure 7 Considering packet 3 in the timing diagram of FIG. 1 , this represents a situation where an uplink packet 70 (packet 3) from STA1 14a is intended for STA2 14b, and by retransmitting packet 70, the AP 10 effectively acts as a repeater.

[0228] In more detail, Figure 7 As schematically indicated in , the AP 10 discovers (stage 102) after decoding the low-speed portion (header) that it is not the intended recipient of the packet 70, and in response, it does not generate and send a downlink signal. Instead, the AP 10 retransmits (stages 104, 108) the packet 70 (packet 3) and thus forwards it to STA 2 14b. Thus, in this case, the communication is actually half-duplex, not full-duplex. The STAs 14a, 14b use the same uplink channel and downlink channel cascade. The forwarding of the packet 70 without A to D conversion by the AP provides a particularly quick and efficient way for STA1 14a and STA2 14b to communicate with each other, even if they are not within line of sight of each other.

[0229] exist Figure 7 In the time period Δt 1 and Δt 2 , multiplexer 36 directs input from the AP transmitter processing circuit to the AP light fixture or other AP transmitter. At other times, multiplexer 36 is switched to retransmit input from the AP receiver. Between packets or frames, AP 10 and stations STA1, STA2 observe the frame interval time.

[0230] Figure 8 So with Figure 7 The same format as the timing diagram, which schematically shows the Figure 3 An optical wireless communication method is performed by an embodiment and used during a contention-free period.

[0231] Figure 8 It shows that in the contention-free period (CFP) Figure 3 , which means that the AP 10 polls the STAs 14a, 14b (downlink packets 80, 84).

[0232] for Figure 8 In the first packet transmission process shown, STA1 14a transmits an uplink packet 85 in response to a downlink packet 80 from the AP 10 that is shorter than the downlink packet 80. STA2 14b decodes only the header 80a of the downlink packet 80, determines that the packet is not intended for STA2 14b, and then does not decode the remainder of the downlink packet 80b. STA1 decodes the header 80a of the downlink packet 80, determines that the packet is intended for STA1 14a, transmits an uplink packet 85 in response, and continues to decode the remainder of the downlink packet 80b.

[0233] for Figure 8 In the second packet transmission process shown, the uplink packet 86 is longer than the downlink packet 84. By retransmitting at least a portion 86a of the uplink packet, the downlink channel from the AP is kept busy to prevent any unnecessary transition from CFP to CP. STA2 14b decodes the header of the downlink packet, determines that the packet 84 is for STA2, and decodes the remainder 84b of the downlink packet 84. STA2 14b transmits the uplink packet 86, which is received by AP2 and partially retransmitted (86a). STA1 decodes only the header 84a of the downlink packet 84 and determines that the packet 84 is not for STA114a. STA1 14a does not decode the remainder of the downlink packet 84 or the retransmitted portion of the uplink packet (86a).

[0234] The AP 10 is allowed to use a shorter interframe space (IFS) than the STAs 14a, 14b. This means that the STAs 14a, 14b have to detect an idle channel for a longer time before they are allowed to transmit. In this way, the AP 10 has priority and can always stop the contention period (CP) if, for example, some urgent packets must be sent. However, if the downlink packets stop early, the STAs 14a, 14b will consider the channel idle without a retransmission mechanism.

[0235] Although some of the above embodiments relate to AP transceiver devices, in alternative embodiments, the transceiver devices are integrated into or associated with optical wireless communication devices other than APs, and are capable of sending and receiving optical wireless communication signals to many other optical wireless communication devices that may or may not be stations. In some embodiments, the optical wireless communication transceiver device may be enabled for half-duplex communication, which is capable of sending and receiving optical wireless communication signals along the same wavelength or wavelength range. In various embodiments, the optical wireless communication transceiver device may be associated with an optical wireless communication device, which may be mobile or fixed and is capable of receiving optical wireless communication signals to and from a similar optical wireless communication device (e.g., another mobile device or AP). For example, the system may include two or more APs to perform AP-to-AP optical wireless communication, or two or more mobile devices to perform device-to-device optical wireless communication.

[0236] In some cases, the full signal retransmission of the received OWC signal by the OWC transceiver device may cause security issues. Therefore, in some embodiments, the received OWC signal is converted into a noise or coded signal before retransmission.

[0237] In some such embodiments, the transceiver device may be on the second signal path, for example Figure 3 Between the branch point 40 in the circuit and the multiplexer 36, an analog scrambler, a noise generator or a digital encryption system may be included. The digital encryption may be performed by a processing circuit, for example, Figure 3 between the branch point 40 in the multiplexer 36 or between Figure 6 OWC signal scrambling, noise generation and / or encryption may be selectively activated by controller 38 to allow the signal to be transmitted as a scrambled signal, noise, an encoded signal or a direct retransmitted signal depending on system requirements.

[0238] Fig.10 Another alternative embodiment is shown. Fig.10 An embodiment similar to Figure 3 1 and 2. The same reference numerals refer to the same components. Fig.10An embodiment of includes an envelope detector 130 having an input connected to the transmitter-side processing circuit 30 and an output connected to the multiplexer 36 .

[0239] Fig.10 The transceiver device of includes a second branch point 132 on a first signal path. The first signal path is a signal path along which the OWC transceiver device sends an OWC signal from the OWC transmitter side processing circuit 30 to the multiplexer 36. The envelope detector is located on a third signal path 134 from the transmitter side processing circuit of the transceiver device leaving the branch point 132 to the multiplexer 36. The third signal path 134 can be arranged so that in operation, the optical wireless communication signal from the transmitter side processing circuit 30 is passed both directly to the multiplexer 36 via the envelope detector 130 and to the multiplexer 36. The envelope detector can perform processing on the optical wireless communication signal to be transmitted, thereby providing an envelope signal of the modulated optical wireless communication signal as an output, for example as a voltage output. The controller can be configured to control the multiplexer 36 according to the output envelope signal, for example if the output envelope detector signal is above or below a threshold voltage. The switching device can switch the multiplexer 36 based on whether the output envelope detector signal is above or below a given voltage threshold to send the modulated optical wireless communication signal from the transmitter side processing circuit 30 to the transmitter 24. The controller can be configured to control the switching device to switch the multiplexer 36 to send the signal from the first signal path or the signal from the second signal path (e.g., from the branch point 40 and / or from the receiver side circuit) from the OWC transmitter side processing circuit 30 to the transmitter 24. In some embodiments, this processing and control can be performed in the electrical domain without any modification to the packet format or further processing by the receiver circuit, such as decoding the packet.

[0240] In current examples of commercially available baseband wireless communication devices, such as commercially available RF baseband wireless communication devices, there is no signal indicating that the baseband wireless communication device is transmitting. A configuration incorporating an envelope detector as described would provide such a signal.

[0241] According to an embodiment, one or more other transceiver devices, such as a station (STA) transceiver device, may include a controller or other component configured to process a received signal in at least one of the following ways:

[0242] 1) At least partially decode the received optical wireless communication signal

[0243] 2) Performing energy detection. The controller may include an energy detection circuit for detecting an energy level within a predetermined frequency or frequency range, optionally wherein the frequency range corresponds to a predetermined number of subcarriers according to the OWC communication protocol used.

[0244] 3) Detect noise, scrambled signals or digitally encrypted signals as described above.

[0245] Based on the result of processing the received signal in at least one of the above-mentioned ways, the controller may determine whether to stop or continue decoding the optical wireless communication signal and / or to send or postpone sending other optical wireless communication signals.

[0246] In certain embodiments, the controller may be configured to control operation of the OWC transceiver device 20 based on partial decoding of a signal including an OWC transceiver identifier signal associated with a given another OWC transceiver device, such as a pseudo noise sequence (PN sequence).

[0247] A respective PN sequence may be associated with each OWC transceiver device. The PN sequence associated with a given OWC transceiver device may be unique within a given OWC transceiver device service set. The PN sequences may be selected such that the PN sequences have very low cross-correlation with each other.

[0248] For example, a PN sequence associated with an AP may be used in downlink transmissions of the AP.

[0249] When a STA receives a frame from an AP, it can use the PN sequence to identify the AP from which the frame was sent. The STA may include a correlator configured to identify the PN sequence by correlating the PN sequence with an expected PN sequence, which is a PN sequence associated with the AP associated with the STA.

[0250] The PN sequence can be detected by correlation without decoding the frame including the PN sequence.

[0251] In certain embodiments, if the PN sequence received in a frame of a downlink OWC signal frame does not match the PN sequence of the AP or other OWC transceiver device (with which the STA is associated or communicating), the STA transceiver device may only retransmit or forward on the received OWC signal, scrambled signal, encrypted signal, or noise.

[0252] In some embodiments, the AP transceiver device may only retransmit or forward on a received OWC signal, scrambled signal, encrypted signal, or noise if the PN sequence in the frame of the uplink OWC signal frame does not match the PN sequence of the AP or other OWC transceiver device associated or communicating with the AP.

[0253] This can help prevent loops or multiple signal paths, such as a first path AP2 to STA and a second path AP2 to STA to AP1 to STA. Although decoding and comparing PN sequences may introduce latency in some cases, it may also improve security.

[0254] exist Figure 6 In some embodiments, the received optical wireless communication signal is in the form of an electrical signal (e.g., the output from the photodetector 22) along a second signal path (the signal path from the receiver side) through the receiver side to the multiplexer 36. In some alternative embodiments, the received optical wireless communication signal is at least partially passed from the receiver side to the transmitter side in the form of a received optical signal and converted to an electrical signal that occurs at a later stage, or converted to an electrical signal using other components, such as another photodetector, which may be on the transmitter side or between the transmitter and receiver sides. In some such embodiments, at least some of the received light is converted to an electrical signal by the photodetector 22, and the resulting electrical signal is passed to the receiver side processing circuit 28, and at least some of the received light is at least partially directed from the receiver side to the transmitter side using at least one electronic component.

[0255] For example, in some embodiments, the transceiver device may include at least one optical element arranged to direct light representing the optical wireless communication signal from the receiver side along at least a portion of the signal path from the receiver side. In some such embodiments, the at least one optical element may be configured to reflect and scatter the received optical wireless communication signal in the form of an optical signal received by the transceiver 20. The optical element may, for example, be at least one convex mirror.

[0256] In some such embodiments, the multiplexer can switch between electrical signals or electrical and optical signals (e.g., selecting to send the optical wireless communication signal from the transmitter-side processing circuit 30 to the transmitter 24 in the form of an electrical signal, or to send the optical wireless communication signal received from the receiver side in the form of an electrical signal or an optical signal). If the received optical wireless communication signal is in the form of an optical signal, a photodetector can be provided at any suitable location to convert the optical signal into an electrical signal before providing it to the transmitter.

[0257] exist Figure 6 and Fig.10In other alternative embodiments or variations of the embodiments, a multiplexer device (e.g., multiplexer 36) is not provided, but at least one optical element is arranged to directly reflect and / or direct at least a portion of the received optical wireless signal to other devices (e.g., stations) in the form of an optical signal without converting the received optical signal to an electrical signal. In some such embodiments, at least some of the received light is converted into an electrical signal by the photodetector 22, and the resulting electrical signal is passed to the receiver-side processing circuit 28. Then, in some embodiments, the controller determines whether an optical wireless communication signal is being received and in response to determining that the optical wireless communication signal is not being received (and therefore in some embodiments, the optical element also does not reflect or direct the optical wireless communication signal to other devices), controls the transmitter-side processing circuit and / or the transmitter to send the optical wireless communication signal.

[0258] In certain situations where half-duplex communications are provided, such as where a transmitter and receiver between AP to AP or device to device transmit and receive signals on the same wavelength or range of wavelengths, embodiments using optical components may be preferred.

[0259] The skilled person will appreciate that variations of the described embodiments are possible without departing from the present invention. Therefore, the above description of specific embodiments is provided by way of example only, and not for the purpose of limitation. It will be clear to the skilled person that the embodiments may be modified without departing from the scope of the present invention.

Claims

1. An optical wireless communication system, comprising: A first device comprising a first transceiver apparatus; as well as a plurality of second devices, each second device comprising a respective second transceiver arrangement; wherein the first device is configured to communicate with the plurality of second devices via an optical channel; as well as The first transceiver device of the first device comprises: a first receiver for receiving first light representing a first optical wireless communication signal transmitted by the second device, the first receiver comprising a photodetector; a receiver-side processing circuit for processing a first optical wireless communication signal received by the receiver to extract data represented by the received first optical wireless communication signal; a transmitter for transmitting a second light representing a second optical wireless communication signal; a transmitter-side processing circuit, configured to generate an optical wireless communication signal for transmission by the transmitter; and At least one optical element for reflecting and / or directing at least some of the light received from at least one of the second devices to at least another of the second devices.

2. An optical wireless communication system according to claim 1, wherein the reflection and / or the guiding of the at least some light by the at least one optical element indicates to at least one of the second devices or each of the second devices that the optical channel of the first receiver is busy.

3. The optical wireless communication system of claim 1, wherein the at least one optical element comprises a mirror.

4. The optical wireless communication system according to claim 1, wherein the first transceiver device comprises a controller for controlling the operation of the first transceiver device of the first device.

5. The optical wireless communication system according to claim 4, comprising at least one of the following: The controller is configured to monitor the first light representative of the first optical wireless communication signal received by the first receiver; the controller being configured to control operation of the first transceiver arrangement of the first device to transmit the second light representing a second optical wireless communication signal in accordance with the monitoring; The transmitter transmits the second light in response to the first light representing the first optical wireless communication signal ceasing or not being received.

6. The optical wireless communication system according to claim 1, wherein: The second devices each include a controller configured to determine whether to transmit or defer transmission of the second optical wireless communication signal based on whether the first light representing the first optical wireless communication signal is received from an optical element of the first apparatus.

7. The optical wireless communication system of claim 1, wherein the first receiver receives the first light at a first wavelength or wavelength range, and the transmitter transmits the second light at a second wavelength or wavelength range, wherein the first wavelength or wavelength range includes one of an infrared wavelength, a visible light wavelength, or an ultraviolet wavelength, and the second wavelength or wavelength range includes one of an infrared wavelength, a visible light wavelength, or an ultraviolet wavelength.

8. The optical wireless communication system according to claim 1, wherein: The multiple second devices are configured such that during at least a portion of a time period when the optical channel is busy with transmission between the first device and the at least another second device among the multiple second devices, the at least another second device among the multiple second devices disables at least one component of its transmitter or transmitter-side processing circuit, and / or postpones transmission; wherein during the at least a portion of the time period, the optical wireless communication signal of the at least another second device among the multiple second devices is received by the first device.

9. The optical wireless communication system of claim 8, wherein each of the plurality of second devices is configured to determine to disable the component and / or defer transmission based on processing of at least a portion of the second optical wireless communication signal received from the first device.

10. The optical wireless communication system of claim 9, wherein the processing further comprises at least one of an energy detection process, noise detection, detection of a scrambled signal, or at least partial decryption of an encrypted signal.

11. The optical wireless communication system according to any one of claims 4 to 10, wherein the first transceiver device comprises: a multiplexer device arranged to receive said first optical wireless communication signals from a plurality of signal paths and pass these signals to a transmitter for transmission; wherein the first signal path to the multiplexer device is from the transmitter side processing circuit; a second signal path to the multiplexer device from the receiver side; wherein the controller controls the operation of the first transceiver device to retransmit at least a portion of a first optical wireless communication signal received by the first receiver from one of the plurality of second devices via the multiplexer device to a transmitter.

12. The optical wireless communication system according to claim 11, wherein: Passing at least a portion of the received first optical wireless communication signal to the transmitter for retransmission includes processing at least a portion of the received first optical wireless communication signal to produce a processed signal and / or a representation of at least a portion of the received first optical wireless communication signal, and the retransmitting includes transmitting the processed signal and / or the representation by the transmitter.

13. The optical wireless communication system according to claim 11, wherein: The received first optical wireless communication signal is an uplink signal; wherein at least one of the second optical wireless communication signals generated by the transmitter-side processing circuit comprises a downlink signal transmitted in response to the uplink signal; Wherein the uplink signal and the downlink signal include and / or form part of an exchange of signals between one of the plurality of second devices and the first device, the exchange establishing and / or forming part of a channel busy period; during the channel busy period, an optical wireless communication channel from the first device is reserved for one of the second devices and is excluded from use by other second devices among the second devices.

14. The optical wireless communication system according to claim 1, wherein: The optical wireless communication system includes a full-duplex communication system or a half-duplex communication system using the same wavelength or wavelength range.

15. The optical wireless communication system of claim 1, wherein the receiver-side processing circuit comprises an amplifier stage.

16. The optical wireless communication system of claim 15, wherein the amplifier stage is connected to a physical layer.

17. A transceiver device of a first device, configured to communicate with a plurality of second devices via an optical channel, the transceiver device comprising: a receiver for receiving first light, the first light representing a first optical wireless communication signal transmitted by the second device, the receiver comprising at least one photodetector; a receiver-side processing circuit, configured to process the first optical wireless communication signal received by the receiver to extract data represented by the received first optical wireless communication signal; a transmitter for transmitting a second light, the second light representing a second optical wireless communication signal; a transmitter-side processing circuit, configured to generate the second optical wireless communication signal for transmission by the transmitter; as well as At least one optical element for reflecting and / or directing at least a portion of light received from at least one of the second devices to at least another one of the second devices or each additional second device.

18. The transceiver device of claim 17, wherein the first light is at a first wavelength or wavelength range and the second light is at a second wavelength or wavelength range.

19. The transceiver device of claim 17, further comprising a controller for controlling operation of the transceiver device of the first device.

20. The transceiver device of claim 17, wherein the receiver-side processing circuit comprises an amplifier stage.

21. The transceiver device of claim 20, wherein the amplifier stage is connected to a physical layer.

22. A method of operating an optical wireless communication system, the method comprising: receiving, by a first transceiver device of the first apparatus, first light representing a first optical wireless communication signal; as well as using at least one optical element to reflect and / or direct at least a portion of the received first light to at least one of a plurality of second devices; wherein, by reflecting and / or directing at least a portion of the received first light by the at least one optical element, indicating to at least one of the plurality of second devices that the optical channel of the receiver is busy; wherein the first transceiver means of the first device comprises at least one optical element; wherein each of the plurality of second devices comprises a second transceiver device; wherein the first device is configured to communicate with the plurality of second devices via at least one optical channel; and Wherein, the transceiver device of the first device comprises: a receiver for receiving said first light representing a first optical wireless communication signal transmitted by a second device; and The transmitter is configured to transmit a second light representing a second optical wireless communication signal.

23. The method according to claim 22, further comprising: monitoring, using a controller, receipt of the first light representing the first optical wireless communication signal; as well as controlling, using a controller, operation of the first transceiver means of the first device to transmit the second light representing the second optical wireless communication signal in response to monitoring the received first light, The first transceiver device comprises a controller.

24. The method according to claim 23, wherein: Transmitting the second light in accordance with the monitoring includes being responsive to the first transceiver device ceasing or not receiving the first light.

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