Intelligent optical wireless communication system

Abstract

A control system for an optical wireless communication system is provided, the optical wireless communication system comprising a plurality of optical communication access points, APs (102), having combined fields of view defining coverage areas, wherein the APs are for communicating with terminal devices, EDs (204), over a communication medium of an optical wireless local area network. At least one ED is movable through a coverage area and thereby within communication range of different APs along a path through the coverage area. A controller obtains a topology of a movable area, wherein the movable area is defined by a physical space through which the movable ED can move. APs are identified that have the movable ED in their field of view (210), and then a first subset of the APs is activated that are determined to be likely to be next from the identified APs along a path through the movable area. A second subset of the APs are determined not to be next along the path through the movable area, and they are switched to a reduced power mode.

Description

Technical Field

[0001] This invention relates to optical wireless communication (OWC) systems. In particular, it relates to a high-bandwidth OWC access point switching between active and reduced power modes to optimize power consumption. Background Technology

[0002] Optical wireless communication (OWC) refers to technologies that transmit information in the form of signals embedded in light emitted by a light source, including visible or invisible light such as infrared light. Depending on the specific wavelength used, this technology may also be called coded light, LiFi, visible light communication (VLC), or free-space optical communication (FSO). In this context, visible light can be light with wavelengths ranging from 380 nm to 740 nm, and infrared (IR) light can be light with wavelengths ranging from 740 nm to 1.5 nm. It's important to understand that there may be some overlap between these ranges.

[0003] OWC (and therefore LiFi and VLC) uses light as a communication medium to replace cable (wired) communication.

[0004] International patent application WO 2020 / 101155 A1 discloses a method for supporting vehicle mobility in a VLC network. According to one of the techniques proposed therein, prior to a handover process, the serving cell to which the vehicle is located provides advance handover notification to the target cell to which the vehicle is moving. This advance notification allows the target cell to prepare for the upcoming handover (including reserving resources for the handover) before the handover process occurs. A different technique is also disclosed, whereby, as the vehicle travels along a street in such a VLC network, streetlights in front of the serving cell in the vehicle's driving direction are added to the current serving cell, and some serving streetlights behind the current serving cell are removed from the current serving cell. In other words, the serving cell is reconfigured as the vehicle travels.

[0005] Light-based communication enables high-data-rate communication (e.g., even exceeding 10 Gbit / s) between devices that have a line of sight. This is applicable, for example, to a group of communication devices in an office environment.

[0006] Known LiFi products rely on a grid of optical access points mounted on the ceiling. These access points have sufficiently wide beams (and thus a large field of view and / or coverage area) to overlap with adjacent access points on a horizontal plane below a table. The receiving device in such a system is typically located at the table or is being held at a height close to the table.

[0007] For ease of installation, the access point grid is aligned, for example, with the lighting grid in the ceiling. Each access point in this installation must reach (i.e., illuminate) several square meters, thus illuminating a fairly large conical area. This installation can use the lighting light for the downlink (to the end device) and can use invisible light (such as infrared or ultraviolet light) for the uplink (towards the access points) so as not to disturb mobile device users. Alternatively, both the downlink and uplink can utilize invisible light, thereby at least partially or completely decoupling the lighting and communication infrastructure.

[0008] To communicate with access points, dongles are currently attached to user devices (such as laptops or tablets). These dongles also emit a similar wide beam to ensure that at least one access point will receive the signal from the dongle.

[0009] Each access point includes a modem connected to one or more optical transceivers. Terminal devices (e.g., laptops with dongles) are connected to the access point via optical links, and they also include modems connected to one or more transceivers.

[0010] A modem functions to handle the protocol (modulation and demodulation) for transmitting and receiving data over a visible or invisible light connection. A modem transmitter includes an optical front end that converts the electrical signals of the transmitted data into optical signals (e.g., using an LED), and a modem receiver converts the optical signals into electrical signals for receiving the data (using a photodiode).

[0011] Industrial setups often include structures that can severely impede the propagation of RF waves (such as metal frames and / or machines). Therefore, modern production processes can utilize optical wireless communications, and these processes are typically highly automated. Specialized machines for different production steps are distributed throughout the production floor. These machines can be, for example, 3D printers or automated milling tools. For instance, on-demand manufacturing using 3D printing systems is expected to become increasingly common.

[0012] Autonomous mobile transport and handling machines supply raw materials to the production machines and retrieve finished products after the production steps have been completed. Final products can then be stored in a warehouse for inspection and shipment. This type of production space can typically operate without human intervention and can be controlled and monitored by a central control system.

[0013] The capabilities of transport machines (or robots) are steadily improving. For example, machines are not only able to find the correct path through space, but they are now also capable of visually inspecting goods or performing simple tests. Therefore, autonomously moving machines also need to be connected to a central control system.

[0014] Furthermore, modern industrial production spaces require flexibility. Therefore, when using an OWC system, any location within the production space should be able to connect to at least one access point, ensuring ease of repositioning production equipment and dynamic allocation through aisles. Terminal devices (EDs), also known as endpoints (EPs), such as dongles, can be installed on fixed equipment or on mobile assets within the production workshop.

[0015] However, the power consumption of OWC in such extended industrial spaces is typically quite high due to the number of APs required to cover all the space needed for seamless OWC connectivity. Therefore, a new approach for seamless OWC connectivity that reduces overall power consumption is needed. Summary of the Invention

[0016] This invention is defined by the claims.

[0017] An alternative approach is provided that offers seamless OWC coverage by managing when the AP enters a reduced-power mode (such as standby) to reduce power consumption.

[0018] According to an example of one aspect of the invention, a control system for an optical wireless communication system is provided, the optical wireless communication system including a plurality of optical communication access points (APs) having a combined field of view defining a coverage area, wherein the APs are used to communicate with terminal devices (EDs) via a communication medium of an optical wireless local area network, wherein at least one ED is movable through the coverage area and thus within the communication range of different APs along a path through the coverage area.

[0019] This control system is suitable for:

[0020] Obtain the topology of the movable region, where the movable region is defined by physical space, and the movable ED can move through this physical space;

[0021] Identify APs that have movable EDs within their field of view;

[0022] The first subset of activated APs is determined to be the next AP along the path through the movable area from the identified AP; and

[0023] The second subset of APs that are determined not to be along the path through the movable area will be set to reduced power mode.

[0024] Preferably, a control system is provided for a manufacturing system of an optical wireless communication system, the optical wireless communication system including a plurality of optical communication access points (APs) having a combined field of view defining a coverage area, wherein the APs are used to communicate with terminal devices (EDs) via a communication medium of an optical wireless local area network, wherein at least one ED is movable through the coverage area and thus within the communication range of different APs along a path through the coverage area.

[0025] The control system described herein is suitable for:

[0026] Obtain the topology for a movable region for at least one movable ED, wherein the movable region is defined by a physical space through which at least one movable ED can move;

[0027] Identify APs that have at least one movable ED in their field of view;

[0028] The first subset of activated APs is determined to be the next AP along the path through the movable area from the identified AP; and

[0029] The second subset of APs that are determined not to be along the path through the movable area will be set to reduced power mode;

[0030] Each AP in the second subset of APs is set to one of at least two reduced power modes, each reduced power mode being defined by different power consumption and / or activation time, and the selection of the reduced power mode for any particular AP in the second subset is based on the distance between the particular AP and the movable ED and whether the field of view of the particular AP is in the movable area.

[0031] The active APs perform ED switching as they move along the path. Reduced power is used, for example, as a standby mode for background communication, while the active APs are used for guaranteed quality of service connections.

[0032] This could be of interest in all kinds of OWC applications, but the inventors found an attractive opportunity to automate such a standby management system, particularly in industrial use cases. During production processes, repetitive activities often occur, allowing rules to be established for power optimization.

[0033] Optical access points (APs) typically have a much smaller field of view (FOV) than other RF-based APs (such as WiFi or Bluetooth) because they rely on visible (or near-visible) light blocked by objects. Additionally, a smaller FOV generally results in higher service quality. Therefore, optical AP arrays are often used to ensure coverage over large areas. In this context, the combined FOV of all APs is referred to as the coverage area.

[0034] The purpose of an optical access point (AP) is to enable an electronic device (ED) to communicate wirelessly with a local area network (LAN). Some EDs can be static (i.e., stationary) and therefore can communicate with a single AP. However, when an ED moves across the coverage area, it will have to change the AP it is communicating with. To avoid latency when switching between APs, this requires all APs in the coverage area to be active, allowing any ED to move throughout the coverage area without any latency. In some cases, having all APs in the coverage area active, even when only one AP is in use, requires significantly more power than strictly required. In other words, an ED only needs one AP at any given time, but all APs must be active to reduce latency.

[0035] Therefore, it has been proposed that only the AP identified as likely to be the next one along the ED path is activated, while the remaining APs can be set to reduced power mode. This reduces the total power usage across all APs, as only the AP that is likely to be the next one is activated (and therefore uses a large amount of power), while the rest are in reduced power mode.

[0036] This makes it possible to assess communication requirements for various industrial processes and analyze the trade-offs between using OWC systems and using low signal quality (QoS) RF communication.

[0037] Additionally, the topology of the space is also considered. In most rooms, the movable ED will not be able to move completely freely. Rooms may have large fixed machines, walls, furniture, etc., which may hinder how the movable ED can move. Therefore, the control system can be given a topology called a movable area. The movable area defines the space through which the movable ED can move and may include obstacles or objects that impede the ED's movement in a particular direction. Therefore, the control system can only activate the AP for the purpose of communicating with the movable ED, through which the ED's path is physically possible. The movable area is a subset of the coverage area, and it defines, for example, the path within the topology of the coverage area.

[0038] The first subset of activated APs can be executed by sending wake-up triggers to at least the APs adjacent to the identified AP. Therefore, the first subset of APs consists of adjacent APs that are triggered to activate based on wake-up triggers. Alternatively, the first subset can be determined by examining which APs might be next along the path and sending wake-up triggers only to APs that might be next along the path—whose FOV covers the relevant movable area (i.e., the movable area including one or more potential paths). The second subset may include all APs not in the first subset.

[0039] When multiple mobile EDs exist in the coverage area, a first subset can be generated for each mobile ED, and a second subset can include all APs that are not in any of the first subsets.

[0040] An access point (AP) can be powered down in different states, typically defined by varying power consumption and / or activation time. For example, the AP's transmit current (TX current) can be disabled. For more aggressive power saving, all power to the AP can be shut off. An AP with its TX current disabled may only take a relatively short time to activate, while a complete power outage of the AP could result in a greater delay in activation.

[0041] The choice of reduced power mode may depend on many factors. However, two important factors are the distance between the AP and the ED and whether the AP's FOV is within the movable area. If the AP is not in the path of the ED (i.e., not within the movable area), it is expected that the ED will not connect to the AP, and therefore the AP can be set to a low reduced power mode (e.g., completely de-energized). However, if the AP is relatively close to the ED, it may be beneficial for it to be in a high reduced power mode (e.g., the TX current is disabled).

[0042] Similarly, the distance between the AP and the ED affects the selection of the reduced power mode. This distance can be determined based on the distance between the AP identified as having a movable ED within its FOV and the AP in question. For example, the closer the ED is to the AP, the more likely it is to be activated quickly. Therefore, the closer APs in the second subset can be set to a high reduced power mode (e.g., TX is disabled).

[0043] One type of power reduction mode may include reducing the transmitter current of the AP's modem. Another type of power reduction mode may include disabling the AP's modem.

[0044] Significant energy savings can be achieved by switching access points (APs) whose coverage areas do not overlap with the movable areas of portable LEDs to the off state. More subtle variations in power savings can be achieved (alternatively or additionally) by taking into account the distance between the AP and the portable LED and switching the corresponding AP to one of several power-reducing modes based on the physical distance. Physical distance can be measured, for example, as Euclidean distance; or, when considering physical constraints imposed by machines, walls, and furniture, as the shortest path distance between the AP and the portable LED.

[0045] The control system can be adapted to store historical data related to the paths that the ED has already followed.

[0046] Therefore, during normal system operation, the path can be determined, and thus the rules for activation and standby can be determined.

[0047] The control system can also be adapted to generate a probability map from path-related historical data, where the probability map indicates the probability of APs that need to be activated.

[0048] Probabilistic graphs can be used to inform the control system which reduced-power mode to set for an AP, or even to set a threshold power consumption. A probabilistic graph can indicate the probability of activation over time. For example, if the probability of activation for an AP in the second subset exceeds 10% (or 20%, 30%, 40%, 50%, etc.) within the next 30 seconds, that AP can be set to a high reduced-power mode (e.g., TX is disabled), or it can even be moved to the first subset and preemptively activated. In fact, the choice of whether an AP is in the first or second subset can be enhanced using probabilistic graphs.

[0049] The control system can be adapted to set different APs along the path to different settings corresponding to different data transmission requirements at different locations along the path.

[0050] The control system can be adapted to set an AP that is not within the communication range of any path already followed by any ED to a static mode, wherein when a movable ED is identified in the AP's field of view, the AP in static mode is not activated or is set to a reduced power mode.

[0051] In this way, APs that have historically been connected to a mobile ED can be marked as <Dynamic>. All other APs can be marked as <Static> and will not respond to wake-ups triggered by neighboring APs. After the coverage area is redeployed, the control system can learn over time which APs are statically connected only to non-mobile EDs and which APs are connected to mobile EDs.

[0052] For example, if an AP in static mode is connected to a non-removable machine that needs to be connected, it can be continuously activated. Alternatively, an AP in static mode can be set to a reduced power mode. The difference between static and dynamic modes is that an AP in static mode does not respond to activation or reduced power mode requests based on the movement of the movable device.

[0053] The control system can also be adapted to determine whether the movable ED is moving or stationary, and set the threshold power consumption of the identified AP to a high threshold based on the movable ED being stationary.

[0054] The identified access point (AP) is one that is identified as having a movable electrical device (ED) within its field of view (FOV). The control system can determine whether the ED is moving or stationary by checking the duration for which the ED is connected to the identified AP. If the ED is connected to the identified AP for a duration longer than a threshold time (e.g., 1, 2, 5, 10, 30 seconds, etc.), the control system can mark the ED as stationary. For example, the ED may be interacting with another device. The specific threshold time can depend on the nature of the ED. For example, if the ED is a machine moving at a known maximum speed, the threshold time can be determined from the time it takes for the machine to cross the AP's FOV.

[0055] The threshold power consumption of a stopped ED is higher than that of a mobile ED. In many cases, there is the assumption that when an ED stops, it is performing a function or doing something. For example, an ED might check the quality of a product before deciding where to move it. Quality checks (or other actions) typically occur in a central system, not locally by the ED, and therefore the bandwidth required when an ED is stopped is usually greater than when it is moving. Consequently, the power requirements of an AP connected to a stopped ED are typically greater than those of a mobile ED.

[0056] The present invention also provides an optical wireless communication system, which includes a set of optical access points (APs) and the control system described above.

[0057] Optical wireless communication systems may also include one or more radio frequency-based access points (RF APs) as backup connections to a local area network used for mobile EDs.

[0058] The present invention also provides a manufacturing system comprising:

[0059] A set of processing units, wherein paths are defined between processing units;

[0060] Vehicles used for conveying materials to and from the processing unit and for removing processed materials from the processing unit; and

[0061] The aforementioned optical wireless communication system includes an ED (Electronic Device) installed in the vehicle.

[0062] A manufacturing plant may include multiple static objects and at least one automated guided vehicle that transports materials to the static objects.

[0063] At least one processing unit may include a 3D printer or a milling machine.

[0064] The present invention also provides a method for controlling an optical wireless communication system in a manufacturing system, the manufacturing system including a plurality of optical communication access points (APs) having a combined field of view defining a coverage area, wherein the APs are used to communicate with a terminal device (ED) via a communication medium of an optical wireless local area network, wherein at least one ED is movable through the coverage area and thus within the communication range of different APs along a path through the coverage area.

[0065] This method includes:

[0066] Obtain the topology for a movable region for at least one movable ED, wherein the movable region is defined by physical space through which at least one movable ED can move.

[0067] Identify APs that have at least one movable ED in their field of view.

[0068] The first subset of activated APs is determined to be the next AP along the path through the movable area from the identified AP, and

[0069] The second subset of APs that are determined not to be along the path through the movable area will be set to reduced power mode;

[0070] Each AP in the second subset of APs is configured with at least one of two reduced power modes, each defined by different power consumption and / or activation time, and the selection of a reduced power mode for any particular AP in the second subset depends on:

[0071] The distance between a specific AP and at least one movable ED, and

[0072] Whether the field of view of a specific AP is within the movable area.

[0073] This method may further include storing historical data related to the paths that the ED has already followed.

[0074] The method may further include generating a probability map from path-related historical data, wherein the probability map indicates the probability of APs that need to be activated.

[0075] The present invention also provides a computer program including computer program code, which, when run on a computer, is adapted to implement the above-described method.

[0076] These and other aspects of the invention will be clear and set forth with reference to one or more embodiments described below. Attached Figure Description

[0077] To better understand the invention and to more clearly illustrate how it can be practiced, reference will now be made to the accompanying drawings by way of example only, in which:

[0078] Figure 1 A typical OWC system is shown;

[0079] Figure 2 A floor plan of an exemplary automated production workshop is shown;

[0080] Figure 3 A production workshop with an exemplary path for moving EDs is shown;

[0081] Figure 4 The field of view of the access point superimposed on the production workshop is shown; and

[0082] Figure 5 A method for controlling an optical wireless communication system is shown. Detailed Implementation

[0083] The invention will be described with reference to the accompanying drawings.

[0084] It should be understood that while the detailed description and specific examples indicate exemplary embodiments of the apparatus, system, and method, they are intended for illustrative purposes only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, system, and method of the present invention will become more readily understood from the following description, the appended claims, and the accompanying drawings. It should be understood that the drawings are merely schematic and are not drawn to scale. It should also be understood that in all the drawings, the same reference numerals are used to indicate the same or similar parts.

[0085] This invention provides a control system for an optical wireless communication system comprising multiple optical communication access points (APs) having combined fields of view defining a coverage area, wherein these APs are used to communicate with terminal devices (EDs) via a communication medium of an optical wireless local area network. At least one ED is movable through the coverage area and thus within the communication range of different APs along a path through the coverage area. The control system obtains the topology of the movable area, wherein the movable area is defined by the physical space through which the movable ED can move. APs having movable EDs in their fields of view are identified, and a first subset of APs is then activated, which are determined to be likely the next AP along the path through the movable area from the identified APs. A second subset of APs is determined not to be the next AP along the path through the movable area, and they are switched to a reduced power mode.

[0086] Figure 1A typical OWC system is illustrated, in which a set of access points (APs) 102 form a ceiling-mounted infrastructure, and terminal equipment (also referred to as stations STAs) is implemented by dongles 106 attached to mobile devices (such as laptops 104). The combination of units 104 and 106 constitutes the terminal equipment (also referred to as endpoints). Access points are preferably linked to the backbone network, for example, by means of wired links (such as Ethernet links using twisted-pair cables or fiber optic networks), thereby allowing the access points and / or global system controllers to align, for example, during handover.

[0087] Each access point (AP) contains a modem that connects to one or more LiFi transceivers. End devices can connect to the AP via an optical link. Each end device also contains a modem that connects to one or more LiFi transceivers. The function of the LiFi modem is to handle the physical layer (PHY) and media access control (MAC) protocols to transmit and receive data over visible or invisible light connections.

[0088] A LiFi transceiver includes a transmitter for converting electrical signals of transmitted data from a modem into optical signals (e.g., via an LED, VCSEL, or laser diode), and a receiver for converting the optical signals into electrical signals of received data from the modem (e.g., via a photodiode). The terminal device is implemented, for example, by a dongle 106 attached to a mobile device such as a laptop. Alternatively, it is envisioned that the receiver functionality is ideally integrated with the user's receiving device itself, so that laptops, tablets, mobile phones, and / or other devices can use optical communication without a dongle.

[0089] The connection to network 110 is achieved via an OWC system. In this case, AP 102 can be integrated with the lighting fixture or within the luminaire. AP 102 is connected to network 110 via data transmission equipment and / or OWC control system 108. The number of APs 102 determines the reliability of the connection and the number of independent, interference-free connections in the space.

[0090] Figure 1 A typical OWC system in an office setting is shown. However, OWC systems can also be used in industrial settings, such as automated production workshops, where the end devices (EDs) are, for example, production machines. Figure 2 A floor plan of an exemplary automated production workshop 200 is shown. Production machines 202 (e.g., 3D printers or automated milling tools) are arranged throughout the production workshop 200 and can be used for different production steps. Figure 2As shown, production machines 202 are typically arranged in rows on production workshop 200. Mobile equipment 204 (such as autonomous moving vehicles (e.g., automated guided vehicles AGVs) and handling machines) and service personnel may move around the production workshop. People and mobile equipment 204 are typically restricted to moving within their dedicated, separate corridors (aisles). Service personnel should not use the corridors used for moving vehicles.

[0091] Figure 2 Figure a) shows production machines 202 arranged in four rows on workshop 200. After processing is completed, moving ED 204 carries raw materials or pre-made goods from one production machine 202 to the next. A warehouse is also present, which may include raw materials, intermediate storage, final product storage 206, and rejected parts storage 208.

[0092] OWC APs can be placed along the aisles of production workshop 200, and in some cases, multiple APs can be used to cover all areas of production workshop 200. Figure 2 Figure b) shows the field of view (FOV) 210 of the optical AP along the corridor of the workshop. For clarity, only 16 FOVs 210 are shown along the corridor. However, it will be understood that the entire workshop 200 can be covered by the FOV 210 of the AP, so that the production machines 202 can also be connected and easily rearranged.

[0093] Additionally, when mobile ED 204 or machine 202 cannot connect to the OWC system, a similar RF communication field (e.g., WiFi or Bluetooth) can be used in workshop 200 as a backup communication system. Therefore, the OWC AP provides high Quality of Service (QoS), while the RF communication system provides a backup connection with lower QoS. The OWC AP can typically transmit data packets with guaranteed latency and data rate, while RF communication may be susceptible to varying interference and fading.

[0094] Figure 3 A production workshop 200 with an exemplary path for moving ED 204 is shown. Figure 3In the scenario depicted in a), the product is being 3D printed at the first production machine 302. When the mobile ED 204 (e.g., a moving transport machine) signals completion, it removes the product from the first production machine 302. En route to the second production machine 304 (e.g., the final painting process), the product may require visual inspection via video transmission from the mobile ED 204 for analysis and back-end processing in a server room, for example. At path 306 from the first processing machine 302 to the second processing machine 304, the product's quality is analyzed, and it is determined whether the product is within margin for further processing. If the product does not meet quality requirements, it can be placed in the non-conforming parts storage 208.

[0095] Figure 3 b) shows the path 308 that the moving ED 204 takes when it must bring the product to the non-conforming parts storage 208.

[0096] Paths 306 and 308 start at the same point, and therefore, it would be preferable if the mobile vehicle determines whether the product has sufficient quality within the same portion of paths 306 and 308. For this purpose, the AP needs to be active along the entire length of path 306 to allow terminal devices (EDs) in the mobile vehicle to communicate with the network and seamlessly switch between APs along path 306.

[0097] Therefore, it is recommended to activate the surrounding APs using the AP currently connected to Mobile ED 204. Figure 4 The field of view of the access points superimposed on production workshop 200 is shown. The blank FOV 402 depicts the active AP, while the lined FOV 404 depicts the AP in reduced power mode. From Figure 4 As clearly shown in the diagram in a), this can significantly reduce the power consumption of the OWC system because it is no longer necessary to activate all APs at full power.

[0098] Proximity information between access points (APs) can be determined from, for example, the known coordinates of the APs, allowing them to directly contact the nearest (neighboring) AP or use neighbor detection techniques.

[0099] Neighbor detection techniques include, for example, observing stray light reflected, diffracted, scattered, and / or refracted at surfaces or objects illuminated by beams from neighboring APs to monitor whether the channel is busy (occupied) due to OWC transmissions from neighboring transmitters.

[0100] It is also recommended to keep the RF connection always available and provide a lower QoS (relative to the OWC AP) because, in this case, a timely failure to connect to the OWC AP will only result in performance degradation, not a complete connection failure. Therefore, it is recommended to always have a backup RF-based connection available to allow for optimal power reduction by disabling potentially as many APs as possible. Additionally, if the AP is already connected to the maximum number of EDs (e.g., the G.hn OWC AP can connect to up to 16 EDs), the mobile ED 204 can still connect to the backup RF communication system. In other words, the backup RF communication system ensures that when the mobile ED 204 cannot connect to the AP, it can still connect to the network via the backup RF communication system.

[0101] In some embodiments, there may be multiple power reduction modes and ways to wake up nodes. Figure 4 The FOVs shown in b) illustrate different power reduction modes. The blank FOV 402 depicts the active AP, the sparsely lined FOV 406 depicts the AP in the first power reduction mode, and the densely lined FOV 408 depicts the AP in the second power reduction mode, where the AP in the second power reduction mode consumes less power and / or takes longer to activate than the AP in the first power reduction mode.

[0102] Generally, the first step in reducing power in OWC is to disable the TX current. Only a short delay is needed for the current to reach the nominal bias level before transmission becomes possible. Disabling the entire optical front end (OFE) will result in more time delay, for example, because the transimpedance amplifier (TIA) in the receive path (RX path) will require some time to stabilize after being powered on again. Finally, the entire modem can be disabled along with the OFE, which will minimize power consumption and result in the highest possible latency after wake-up triggering until availability can be guaranteed. Many other power reduction modes are envisioned, altering the activation time and power consumption in the power reduction mode.

[0103] The operating conditions for an OWC system can be optimized in several ways, such as by implementing training patterns. Over time, the implementation of these training patterns can be considered an optimization of the OWC system. Inputs to the training patterns can include the system's dynamics over time. In other words, optimization may differ at different times based on the schedule (e.g., data requirements may differ at night compared to repetitive processes during a daytime cycle).

[0104] Another input that can be considered for training modes is the system's location dynamics. In other words, depending on the specific physical location in the system (i.e., the hotspot for data / QoS), there may be different data requirements. For example, data traffic through each AP can be monitored, and APs with high data traffic levels and / or high QoS requirements may, for example, not be set to a low-power reduction mode.

[0105] Similarly, the same processing can be applied to APs in locations known to have high data traffic levels and / or minimum QoS requirements. This might happen when mobile ED 204 needs to perform inspections on products from a specific production machine 202. If the inspection is performed at the production machine, the AP corresponding to the location of production machine 202 can be processed differently from other APs (e.g., not set to reduced power mode).

[0106] The dynamics arising from the movement of objects can also be used as input for training patterns. For example, the movement of ED204 may primarily follow a specific path. The production of a particular product may follow one of a variety of different paths (e.g., defective products on the production line may require different processes than other products, and therefore may require different QoS).

[0107] The recording and analysis of communication behavior between the mobile ED 204 and the AP can be done on a local server or externally (e.g., on a cloud server).

[0108] All APs serving the area where there is no movable ED 204 can be moved can remain in reduced power mode, regardless of their proximity to the movable ED 204. The area where the movable ED 204 can be moved is referred to as the movable area. Some production machines 202 may require connection, and therefore they can be activated individually. If machines 202 do not require any OWC connection, they can remain in reduced power mode (e.g., disabled), and therefore only APs at the location where the movable ED 204 might move next need to be activated and await a switchover request. A floor plan of the production workshop 200 can be manually used to determine the AP range.

[0109] Movable areas can be obtained via a floor plan detailing the locations of static objects such as machines, walls, etc. The floor plan may be updated if the machine layout changes. Alternatively, movable areas can be updated over time by examining the paths of moving ED204s. If the paths of moving EDs no longer lead them through a specific area, it may be because a machine has been moved to that area or a new machine has been placed in it. Therefore, a specific area can be removed from the movable areas, meaning that APs in that specific area may no longer respond to nearby moving EDs or receive wake-up triggers.

[0110] APs can be marked as static APs when they do not have their field of view (FOV) within the movable area (e.g., they are not in a corridor). Therefore, all APs can be marked as either "static" or "dynamic". APs marked as static may not respond to wake-up calls (i.e., they will not be in the first subset of APs, which is those determined to be the next AP along the path through the movable area), while APs marked as dynamic will respond to such wake-up calls.

[0111] The history of the movement of mobile ED 204 around production shop 200 can be registered and used to determine which APs are marked as dynamic or static. This can be used to automatically mark all APs as dynamic if they have ever been connected to mobile ED 204. All other APs are marked as static and do not respond to wake-ups triggered by neighboring APs. After the shop floor is rearranged, the system can learn over time which APs are statically connected only to non-mobile EDs and which APs are connected to mobile ED 204.

[0112] The probability that a neighboring AP will receive a handover can be calculated based on its historical moves. For example, Figure 4 The probability of moving ED204 to the right towards storage 206 or 208 is likely higher than the probability of moving it to the left towards the end of the corridor. Therefore, this probability can be used to indicate which APs are active, and in some instances, to indicate which reduced power mode should be set for inactive APs. For example, a higher activation probability for a particular AP corresponds to a higher reduced power mode (i.e., higher power consumption / shorter activation time). In cases where APs have overlapping FOVs and moving ED 204 can selectively connect to any AP, this probability can be used to select which AP to connect to (e.g., if the probability of connecting to the leftmost AP is higher, then connect to the leftmost available AP).

[0113] This probability can be made dependent on the direction of movement. Therefore, different probabilities may exist depending on the direction in which the moving ED 204 is moving. For example, if the moving ED 204 starts moving from the first production machine to the second production machine, the probability diagram may look different from the case where the moving ED 204 starts moving in the opposite direction toward the non-conforming parts storage 208.

[0114] Additionally, this probability can be made dependent on information transmitted by a process control system that controls the trajectory of each movement of the moving ED 204. Using the information from the process control system, the speed of the moving ED 204 can be predicted, thereby allowing the wake-up timing for the AP to be adjusted to suit the speed of the moving ED 204 (i.e., the faster the moving ED 204 moves, the faster a wake-up message needs to be sent to activate the AP).

[0115] Machine learning algorithms can also be used to improve the performance of OWC systems. Starting with an AP with high QoS (and therefore high power operation), a feedback loop using recorded historical data requirements can be fed into a machine learning algorithm to optimize QoS. This can be applied to situations where ED is only used temporarily in high QoS mode (e.g., to deliver visual inspection data). For the remaining time when high QoS mode is not used, a lower power mode can be selected.

[0116] In summary, it is recommended to use optimizations for automatic standby activation and recovery of APs based on rules determined during typical OWC system operation (i.e., the next AP along a possible path). This approach can be applied to all types of OWC applications, but is particularly advantageous in industrial use cases, where frequent, repetitive activities are often involved. For cases where atypical activity is detected, it is further recommended to use backup RF connections, as these may require unplanned AP node reactivation, which could take some time.

[0117] Repeated movement sequences (i.e., common paths) can be found in the requirements profile to schedule AP operation and standby mode timelines, which leads to reduced power consumption.

[0118] Process triggering (e.g., dynamic / static, near-moving ED, etc.) can be selected to initiate this activation / de-power mode schedule for regular production processes.

[0119] The special activation of AP allows any deviation from the timetable to be adaptively adjusted for changes in the sequence or timing.

[0120] Figure 5 A method for controlling an optical wireless (OWC) communication system is illustrated. The OWC system includes multiple optical communication access points (APs) having a combined field of view that defines a coverage area. The APs are used to communicate with terminal devices (EDs) via a communication medium of an optical wireless local area network, wherein at least one ED is movable through the coverage area and thus within the communication range of different APs along a path through the coverage area.

[0121] The method includes, in step 502, identifying APs with movable EDs within their field of view. In step 504, activating a first subset of APs, which are determined to be likely the next AP along the path through the movable region from the identified APs. Additionally, in step 506, setting a second subset of APs to a reduced power mode, said second subset of APs being determined not to be the next AP along the path through the movable region.

[0122] Those skilled in the art will be able to readily develop control systems for performing any of the methods described herein. Therefore, each step of the flowchart can represent a different action performed by the control system and can be executed by the corresponding module processing the control system.

[0123] Control systems can be implemented in many ways, using software and / or hardware, to perform a variety of required functions. A processor, then commonly referred to as a controller, is one example of a control system that employs one or more microprocessors, which can be programmed using software (e.g., microcode) to perform the desired functions. However, control systems can be implemented with or without a processor, and can also be implemented as a combination of dedicated hardware performing some functions and processors performing other functions (e.g., one or more programmed microprocessors and associated circuitry).

[0124] Examples of controller components that may be used in various embodiments of this disclosure include, but are not limited to, conventional microprocessors, application-specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs).

[0125] In various implementations, the processor or controller may be associated with one or more storage media, such as volatile and non-volatile computer memories, such as RAM, PROM, EPROM, and EEPROM. The storage media may be encoded with one or more programs that, when executed on one or more processors and / or controllers, perform the required functions. The various storage media may be fixed within the processor or controller, or may be transportable, such that one or more programs stored thereon can be loaded into the processor or controller.

[0126] Based on a study of the accompanying drawings, the disclosure, and the appended claims, those skilled in the art can understand and implement variations of the disclosed embodiments in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality.

[0127] The mere fact that certain measures are referenced in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously.

[0128] If the term “suitable” is used in the claims or description, it should be noted that the term “suitable” is intended to be equivalent to the term “configured as”.

[0129] Any reference numerals in the claims should not be construed as limiting the scope.

Claims

1. A control system for use in an optical wireless communication system in a manufacturing system, said manufacturing system comprising a plurality of optical communication access points (APs) (102) having combined fields of view defining a coverage area, wherein the APs are used to communicate with terminal devices (EDs) (204) via a communication medium of an optical wireless local area network, wherein at least one ED is movable through said coverage area and thus within communication range of different APs along a path through said coverage area. The control system described herein is suitable for: Obtain a topology for a movable region for at least one movable ED, wherein the movable region is a subset of the covered region and is defined by physical space, the at least one movable ED being movable through the physical space without any fixed obstacles or objects impeding movement, and the movable region defining a path within the topology of the covered region; Identify APs that have at least one movable ED in their field of view (210); The first subset of activated APs is determined to be the next AP along the path through the movable area from the identified APs. and The second subset of APs that are determined not to be along the path through the movable area will be set to reduced power mode; Each AP in the second subset of the APs is set to one of at least two reduced power modes, each reduced power mode being defined by different power consumption and / or activation time, and the selection of the reduced power mode for any particular AP in the second subset depends on the distance between the particular AP and at least one movable ED and whether the field of view of the particular AP is within the movable area.

2. The control system of claim 1, wherein the control system is adapted to store historical data related to paths already followed by the ED.

3. The control system of claim 2, wherein the control system is further adapted to generate a probability map from path-related historical data, wherein the probability map indicates the probability of an AP that needs to be activated.

4. The control system according to claim 2, wherein the control system is adapted to set different APs along the path to different settings corresponding to different data transmission requirements at different locations along the path.

5. The control system according to claim 2 or 4, wherein the control system is adapted to set an AP that is not within the communication range of any path already followed by any ED to a static mode, wherein when a movable ED is identified in the field of view of the AP, the AP in the static mode is not activated or set to a reduced power mode.

6. The control system of claim 1 or 4, wherein each AP includes an optical front end having an optical transmitter and a modem connected to the optical front end, and wherein at least two power reduction modes of a particular AP are selected from: - First power-off mode, in which the optical transmitter current of the optical transmitter is disabled for a specific AP; - Second power-off mode, in which power supply to the optical front end of a specific AP is disabled; and - The third power outage mode, in which all power supply to a specific AP is turned off.

7. The control system according to claim 1 or 4, wherein the control system is further adapted to: Determine whether the movable ED is moving or stationary; and Since the movable ED is stopped, the threshold power consumption of the identified AP is set to a high threshold.

8. An optical wireless communication system, comprising: A group of access points (APs); and The control system according to claim 1 or 4.

9. The optical wireless communication system of claim 8 further includes one or more radio frequency-based access points (RFAPs) as backup connections to a local area network for a mobile ED.

10. A manufacturing system, comprising: A set of processing units, wherein the path (306, 308) is defined between the processing units; Vehicles used to transport materials to and from the processing unit and to remove processed materials from the processing unit; and The optical wireless communication system according to claim 9, The vehicle is equipped with an optical wireless communication system (ED).

11. The manufacturing system of claim 10, wherein at least one processing unit comprises a 3D printer or a milling machine.

12. A method for controlling an optical wireless communication system in a manufacturing system, the manufacturing system comprising a plurality of optical communication access points (APs) having combined fields of view defining a coverage area, wherein the APs are used to communicate with terminal devices (EDs) via a communication medium of an optical wireless local area network, wherein at least one ED is movable through the coverage area and thus within communication range of different APs along a path through the coverage area. The method includes: Obtain a topology for a movable region for at least one movable ED, wherein the movable region is a subset of the covered region and is defined by physical space, the at least one movable ED being movable through the physical space without any fixed obstacles or objects impeding movement, and the movable region defining a path within the topology of the covered region; Identify (502) an AP that has at least one movable ED in its field of view; Activate the first subset of APs (504), which are determined to be the next AP along the path through the movable area from the identified APs; and The second subset of APs that are not along the path through the movable area will be set to reduced power mode (506); Each AP in the second subset of APs is configured with at least two reduced power modes, each defined by different power consumption and / or activation time, and the selection of a reduced power mode for any particular AP in the second subset depends on: The distance between a specific AP and at least one movable ED, and Whether the field of view of a specific AP is within the movable area.

13. The method of claim 12, further comprising storing historical data related to paths already followed by the ED.

14. The method of claim 13, further comprising generating a probability map from path-related historical data, wherein the probability map indicates the probability of an AP requiring activation.

15. A computer program product comprising computer program code, which, when run on a computer, implements the method according to claim 12.

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