Interference mitigation

Abstract

An optical wireless communication OWC network (100) includes multiple access points (120) for communicating with multiple endpoint devices (110) via modulated light. A control system (13) receives a report of an indicated time slot during which a first access point (120a) detects an event indicating interference and transmits the indication of the time slot to at least one other access point (120b). The other access points (120b) provide the control system (13) with identifiers of any registered endpoint devices that have used or are using the time slot. If the control system (13) receives the identifier of a single endpoint device from the other access points (120b), it identifies that endpoint device as the cause of the interference experienced at the first access point (120a). If the control system (13) receives the identifiers of multiple endpoint devices from the other access points (120), it causes the endpoint devices in the OWC network (100) to announce their presence.

Description

Technical Field

[0001] This disclosure relates to control systems, access points, and methods for optical wireless communication (OWC) networks. Background Technology

[0002] To enable a growing number of electronic devices, such as laptops, tablets, and smartphones, to wirelessly connect to the internet, wireless communication faces unprecedented demands for data rates and link quality, and these demands continue to grow year after year, given the emerging digital revolution associated with the Internet of Things (IoT). Radio frequency (RF) technologies, such as Wi-Fi, have limited spectrum capacity and cannot meet this revolution. Meanwhile, Light Fidelity (Li-Fi) is attracting increasing attention due to its inherent enhanced security and ability to support higher data rates across the available bandwidth of the visible, ultraviolet (UV), and infrared (IR) spectra. Furthermore, compared to Wi-Fi, Li-Fi is directional and shielded by light-blocking materials, making it possible to deploy a larger number of access points in densely populated areas by spatially reusing the same bandwidth. These key advantages compared to wireless RF communication make Li-Fi a promising solution for alleviating the congested radio spectrum pressures of IoT applications. Other benefits of Li-Fi include guaranteed bandwidth for specific users and the ability to operate safely in areas susceptible to electromagnetic interference. Therefore, Li-Fi is a very promising technology for enabling next-generation immersive connectivity.

[0003] Several related terms exist in the field of lighting-based communications. Visible light communication (VLC) transmits data via intensity-modulated light sources such as light-emitting diodes (LEDs) and laser diodes (LDs), faster than the persistence of the human eye. VLC is typically used to embed signals into light emitted by a lighting source, such as everyday lamps, for example, indoor or outdoor lighting, thus allowing the lighting from the lamp to serve as a carrier of information. Therefore, the light can include a visible lighting component used to illuminate a target environment such as a room (often the primary purpose of light), and an embedded signal used to provide information to the environment (often considered a secondary function of light). In this case, modulation can typically be performed at a sufficiently high frequency to exceed human perception, or at least make any visible transient light artifacts (such as flicker and / or stroboscopic artifacts) sufficiently weak and not noticeable or at least tolerable to humans at a sufficiently high frequency. Therefore, the embedded signal does not affect the primary lighting function; that is, the user only perceives the overall lighting, not the effect of the data modulated into that lighting.

[0004] The IEEE 802.15.7 Visible Light Communication Personal Area Network (VPAN) standard maps anticipated applications to four topologies: peer-to-peer, star, broadcast, and coordinated. Optical Wireless PAN (OWPAN) is a more general term than VPAN, as it also allows communication over invisible light, such as UV and IR. Therefore, Li-Fi is often considered a derivative of Optical Wireless Communication (OWC) technology, which utilizes a broad spectrum to support bidirectional data communication.

[0005] In Li-Fi systems, signals are embedded by modulating the properties (typically intensity) of light, using any of a variety of suitable modulation techniques. For high-speed communication, infrared (IR) is often used instead of visible light. Although ultraviolet and infrared radiation are invisible to the human eye, the techniques for utilizing these spectral regions are similar, although variations can occur as a result of wavelength dependence (such as in the case of refractive index). In many instances, using ultraviolet and / or infrared is advantageous because these frequency ranges are invisible to the human eye and can introduce more flexibility into the system. Of course, ultraviolet quanta have higher energy levels than infrared and / or visible light, which in turn may make the use of ultraviolet light undesirable in certain situations.

[0006] Based on modulation, any suitable light sensor can be used to detect information in light. For example, a light sensor can be a photodiode. A light sensor can be a dedicated photocell (point detector), a photocell array possibly with lenses, reflectors, diffusers, or phosphor converters (for lower speeds), or a photocell (pixel) array and lenses for forming an image on the array. For example, a light sensor can be a dedicated photocell included in a dongle inserted into a user device such as a smartphone, tablet, or laptop, or the sensor can be integrated and / or dual-purpose, such as an infrared detector array originally designed for 3D facial recognition. Either way, this allows applications running on the user device to receive data via light. Summary of the Invention

[0007] According to a first aspect disclosed herein, a control system for an optical wireless communication (OWC) network is provided, wherein the OWC network includes multiple access points for communicating with multiple endpoint devices via modulated light. The control system is configured to: in response to receiving a report indicating a time slot, transmit an indication of the time slot to at least one other access point, causing the other access point to provide the control system with identifiers of the endpoint devices registered with the other access point and communicating with the other access point using the time slot, or identifiers of each endpoint device, during which a first access point among the access points detects an event indicating interference; and in response to receiving an identifier of a single endpoint device from the other access point, determine the single endpoint device identified by the identifier as the cause of interference experienced at the first access point; and in response to receiving identifiers of multiple endpoint devices from one or more of the other access points, instruct the one or more other access points to instruct the endpoint devices registered with the one or more other access points to announce their presence.

[0008] In one example, the EP is communicating with or attempting to communicate with the other access point during the time slot.

[0009] In one example, the control system is configured to transmit an indication of the timeslot to one or more access points (or access points) that are closest to the first access point.

[0010] The nearest other access points (or one or more) can be, for example, the other access points (or multiple access points) that are geographically closest (physically closest) to the first access point. These other access points (or multiple access points) can be, for example, the other access points (or multiple access points) that have the largest overlap coverage with the first access point. This information can be configured into the control system by the installer. Alternatively, the control system can understand which other access points have overlapping coverage areas by reporting the endpoints that detect the announcements of other access points when associated with the first access point (and thus implicitly covering the coverage area of ​​the first access point). (Additionally, if the EP's report includes the received signal power of the announcements of the detected other access points, the control system can understand how close the nearby other access points are.) The coverage of an access point (or, in this sense, an endpoint) can be interpreted two-dimensionally as a coverage area or three-dimensionally as a coverage volume. In practical systems, two-dimensional evaluation has provided a simplified but satisfactory approximation of the coverage volume.

[0011] There may be more than one nearest other access point. For example, two or more other access points may be within a threshold distance of the first access point. These other access points may even be at the same or substantially the same distance from the first access point. As another example, two or more other access points may have an overlap coverage with the first access point exceeding a threshold. These other access points may even have the same or substantially the same overlap coverage with the first access point. The control system can be configured to transmit an indication of the timeslot to each nearest other access point.

[0012] In one example, the control system is configured to transmit an indication of the timeslot to at least one other access point physically located within a threshold distance of the first access point. The threshold distance may be, for example, one meter or two meters, ten meters, or something else. Generally, the threshold distance may be equal to or substantially equal to the maximum receiving field of view of the access point (or the average number of access points or more than one (e.g., all) access points).

[0013] In one example, the control system is configured to transmit an indication of the timeslot to at least one other access point that has overlapping coverage with the first access point exceeding a threshold.

[0014] In one example, the control system is configured to transmit the time slot indication to all other access points in the same building room as the first access point.

[0015] In one example, the control system is configured to transmit the indication of the timeslot to all other access points in the OWC network.

[0016] In one example, the control system is configured to, in response to receiving a report from an endpoint device registered to one of the access points indicating interference from at least one neighboring access point, notify the endpoint device of its presence. In these examples, the endpoint device is the device that initially determines the potential interference, unlike other examples where the access point initially determines the potential interference. Therefore, one advantage is that uplink interference (by the access point) and downlink interference (by the endpoint device) are handled separately.

[0017] In one example, the control system is implemented at the first access point. Generally, the control system can be implemented as a central lighting controller at the first access point, or in a distributed manner at access points in the OWC network.

[0018] In some examples, the control system can be implemented as a central entity, thereby covering the functionality of multiple access points. This central entity can be contained within an access point (AP), but it can also be contained in a separate unit not included in the AP.

[0019] In other examples, the control system can be implemented in a distributed manner, whereby its functionality is contained within access points. In this case, each access point includes a portion of the control system associated with it, such as information about its nearest other access point or multiple access points.

[0020] In one example, the control system is implemented in a distributed manner across multiple access points.

[0021] According to a second aspect disclosed herein, a method is provided executed by a control system of an optical wireless communication (OWC) network, the OWC network including multiple access points for communicating with multiple endpoint devices via modulated light, the method comprising: receiving a report indicating a time slot during which a first access point detects an event indicating interference; in response to receiving the report, transmitting an indication of the time slot to at least one other access point such that the other access point provides the control system with the endpoint device or an identifier of each endpoint device that is registered with the other access point and is communicating with the other access point using the time slot; in response to receiving an identifier of a single endpoint device from the other access point, determining a single neighboring endpoint device identified by the identifier as the cause of interference experienced at the first access point; and in response to receiving identifiers of multiple neighboring endpoint devices from one or more of the other access points, instructing the one or more other access points to instruct the endpoint devices registered with the one or more other access points to announce their presence.

[0022] In one example, the method includes: in response to receiving a report from an endpoint device registered to one of the access points indicating interference from at least one neighboring access point, causing the endpoint device to announce its presence.

[0023] According to a third aspect disclosed herein, an access point for an optical wireless communication (OWC) network is provided for communicating with at least one endpoint device via modulated light, the access point being configured to: in response to receiving an indication of a time slot from a control system, identify an endpoint device registered to the access point and communicating with the access point using the time slot, during which another access point detects an event indicating interference; and provide an identifier of the endpoint device to the control system.

[0024] According to the fourth aspect disclosed herein, a method is provided performed by an access point of an optical wireless communication (OWC) network, the method comprising: in response to receiving an indication of a time slot from a control system, identifying an endpoint device registered to the access point and communicating with the access point using the time slot, during which another access point detects an event indicating interference; and providing an identifier of the endpoint device to the control system.

[0025] According to the fifth aspect disclosed herein, an optical wireless communication (OWC) system is provided, which includes the control system of the first aspect and multiple access points. Attached Figure Description

[0026] To aid in understanding this disclosure and to illustrate how embodiments may be implemented, reference is made by way of example to the accompanying drawings, in which:

[0027] Figure 1 An example of an OWC network system is illustrated schematically;

[0028] Figure 2 An example of a MAC cycle is illustrated schematically;

[0029] Figure 3 The first example of an AP notification is shown schematically;

[0030] Figure 4 The second example of an AP notification is illustrated schematically;

[0031] Figure 5 The first example of an EP notification is shown schematically;

[0032] Figure 6 A second example of an EP notification is shown schematically;

[0033] Figure 7 Another example of an OWC network is illustrated schematically;

[0034] Figure 8 The first example method is illustrated schematically; and

[0035] Figure 9 The second example method is illustrated schematically. Detailed Implementation

[0036] In optical wireless communication (OWC) networks, fast and effective interference handling requires rapid detection of the cause of interference. Existing interference detection methods are based on devices cyclically sending short frames (“advertisements” or “adverts”) carrying identifiers that identify the device.

[0037] OWC networks can include multiple access points (APs) and multiple endpoints (EPs). This type of network is often referred to as a multipoint-to-multipoint network, where multiple access points provide network access services to multiple endpoints located within their coverage areas. If many EPs are present in a dense area, identification can take a relatively long time or otherwise incur significant overhead due to frequent announcements. This disclosure proposes an event-triggered scheme, rather than a cyclic scheme, for instructing EPs to announce their presence. This achieves short latency to address uplink interference. It also reduces network traffic. Furthermore, it minimizes EP power consumption, which is particularly important in battery-powered EPs.

[0038] In other words, this disclosure relates more to determining network topology and not to interference mitigation techniques themselves. Some examples of this disclosure achieve network topology determination with short latency while avoiding conflicts within a limited available time.

[0039] Generally speaking, the example solutions provided in this article can be summarized as follows.

[0040] The control system (e.g., a LiFi controller) receives reports from the AP indicating that uplink interference has occurred in a time slot (e.g., a time slot in the MAC cycle, discussed in more detail below). Upon receiving such a report, the control system sends an interference check request to the AP's neighboring APs (which includes an indication of the time slot in the MAC cycle, and, if necessary, an indication of the MAC cycle itself). When the interference check request is received, the AP checks whether the EP registered to it has already transmitted in the indicated time slot and replies to the request indicating whether this is the case, thereby (optionally) including the EP's identifier. Various options exist for the response. For example:

[0041] Option 1: If the AP has detected that the EP is transmitting in the time slot indicated by the interference check request, the AP instructs the EP to send a notification;

[0042] Option 2: Upon receiving a response from the AP regarding an interference check request (indicating that the EP is transmitting), the control system sends an EP notification request (including the EP's identifier) ​​to the AP, and the AP instructs the EP to send a notification on that request.

[0043] Figure 1 An example of an OWC network system 100 (also referred to herein as OWC network 100) is illustrated schematically. The terms OWC and LiFi are often used interchangeably. Other commonly used terms include visible light communication (VLC) and free space optical communication (FSO).

[0044] OWC network 100 includes multiple access points (APs) 120 and one or more endpoint devices (EPs) 110. A backbone 21 and control system 13 are also shown; these can be separate devices and arrangements, or they can be considered part of OWC network 100. For the purposes of explanation, simplification is provided. Figure 1 The diagram illustrates an OWC network 100, which may include additional access points and endpoint devices, as well as additional components (such as IP routers, Ethernet switches, etc.). The OWC network 100 can also connect to external networks (not shown in the diagram). Figure 1 (As shown in the image).

[0045] AP 120 and control system 13 are operatively coupled via backbone 21. Backbone 21 provides a stable and high-speed communication link, which can be a wired connection (such as Ethernet) or a radio frequency (RF) or millimeter wave-based wireless connection. The backbone connection can also be another type of optical wireless link, which differs from the link used by the endpoints in an optical multi-cell wireless network. An example of another type of optical wireless link could be a free-space point-to-point optical link.

[0046] The EP 110 is or includes an end-user modem that facilitates connection of terminal devices to the OWC network 100. Currently, the EP 110 is typically a dedicated entity that connects to or is integrated into a laptop or other terminal device. In the future, the EP 110 may be partially or fully integrated into smartphones, tablets, computers, remote controls, smart TVs, display devices, storage devices, home appliances, or other smart electronic devices.

[0047] AP 120 and EP 110 communicate via OWC signals. For this purpose, each AP 120 and each EP 110 includes at least one optical front end for transmitting and receiving OWC signals. For example, each AP 120 may include an OWC transceiver (TRX) for transmitting and receiving OWC signals to and from EP 110. Similarly, each EP 110 may include an OWC TRX for transmitting and receiving OWC signals to and from AP 120.

[0048] Each optical front end provides OWC connectivity within its field of view (FoV) or coverage area. The first device (e.g., AP 120) is able to receive OWC signals from the second device (e.g., AP 120) only if the first device (e.g., EP 110) is within the coverage area of ​​the second device (e.g., AP 120).

[0049] exist Figure 1In this context, it is assumed that each AP 120 and EP 110 comprises a single optical front end, and its field of view (FOV) is shown as a circular sector. It should be understood that in the real world, each FOV will typically be a three-dimensional volume, and its shape will depend on various factors, including, for example, the layout of the environment in which the AP 120 or EP 110 is mounted, the physical shape and construction of the AP 120 or EP 110 itself, the orientation of the AP 120 or EP 110 within the environment, etc.

[0050] In operation, at any given time, each EP 110 selectively associates with and synchronizes with a corresponding AP 120. That is, each EP 110 registers with a specific AP 120. This is in... Figure 1 The arrows indicate that EP1 and EP2 are associated with AP1, and EP3 is associated with AP2.

[0051] Essentially, the EP 110 can connect to the AP 120 via a bidirectional optical link or a hybrid downlink and uplink. Note that in this document, downlink refers to the communication link from the AP 120 to the EP 110, and uplink refers to the communication link from the EP 110 to the AP 120. The bidirectional optical link enables a relatively symmetrical connection between the EP 110 and the AP 120. Therefore, both the downlink and uplink enjoy the same advantages of Li-Fi communication as described above.

[0052] In cases where the coverage areas of the access points overlap, communication interference can occur between AP 120 and EP 110. Coordination by access point 120 is required to handle the interference. In this example, this is the responsibility of control system 13.

[0053] In this case, there are two types of interference to consider:

[0054] Uplink (or "uptream") interference: EP 110 transmits a signal to AP 120 to which it is registered, while another EP 110 is transmitting a signal to its own AP 120, which may cause uplink interference to the signal from the first EP 110 at the AP 120 to which the first EP 110 is registered;

[0055] Downlink (or "downstream") interference: If these APs 120 transmit signals (typically signals for EPs registered to them) while EPs 110 are scheduled to receive signals from their own APs, then EPs 110 in the overlapping coverage area of ​​multiple optical downlinks from several APs 120 will experience interference.

[0056] Two EPs (Figure 1 The uplink overlap coverage area of ​​EP2 and EP3 in the AP can be defined as AP ( Figure 1 AP2) can be a region or area that can receive OWC signals from two EPs.

[0057] Two APs ( Figure 1 The downlink overlapping coverage area of ​​AP1 and AP2 in the EP (AP1 and AP2) can be defined as EP (AP1 and AP2). Figure 1 EP2) is an area or zone that can receive OWC signals from two APs.

[0058] exist Figure 1 In the setup shown, when AP1 and AP2 transmit simultaneously, downlink interference to EP2 will occur. When EP2 and EP3 transmit simultaneously, uplink interference to AP2 will occur.

[0059] The control system 13 performs various functions, including, in various examples, deriving information about topology and neighbor relationships, and determining the scheduling of different APs 120 for interference suppression. The control system 13 may also provide a user interface that allows users or administrators (e.g., IT administrators) to configure the control system to influence the scheduling of multiple APs 120, monitor reports from these APs 120, and / or derive further statistics about system performance.

[0060] exist Figure 1 In the example shown, control system 13 is implemented as a dedicated OWC network controller (i.e., in a centralized manner) that is connected to multiple APs 120 in the OWC network 100 via backbone 21. However, it will be understood that control system 13 is a functional block for performing the various tasks described herein and can be implemented in one of the APs 120 or in a distributed manner (e.g., across APs 120), as in other examples described below.

[0061] OWC Network 100 typically uses Time Division Multiple Access (TDMA) to handle interference. TDMA is based on a time division multiplexing scheme in which access to radio resources is scheduled in the time domain and different time slots are allocated to different transmitters in a typical cyclic repeating frame structure or MAC cycle (also known as a MAC frame). Figure 2 The example MAC cycle 200 is shown in the figure.

[0062] For interference handling, the control system 13 determines for each AP 120 which time slot(s) ...

[0063] MAC cycle 200 includes a common channel 210 that provides interference handling (shown at the end of MAC cycle 200 in this example). Access to the common channel 210 can be contention-based, contention-free through coordinated scheduling, or a combination of both. The common channel 210 is divided into two parts: a first part 211 for the AP (CC-AP) and a second part 212 for the EP (CC-EP). This goes back to below.

[0064] MAC cycles are synchronized among Access Points 120. Various synchronization methods are known. For example, APs 120 can be synchronized to a common time base, such as using a synchronization handshake, via a reference clock distributed across the network (such as a synchronized Ethernet clock), or via a dedicated synchronization server in the network, or derived from a common signal (such as zero-crossing of trunk power). A concrete example of a synchronization protocol is the Precision Time Protocol (PTP), IEEE 1588v2. PTP provides sub-microsecond accuracy, which is sufficient for G.vlc inter-domain MAC alignment (where G.vlc refers to ITU-T G.9991). To maintain PTP accuracy, support from the Ethernet switch is necessary, and it should also support PTP. To maintain PTP accuracy, any element in the Ethernet network must handle PTP; therefore, the switch chosen for any deployment must support and be configured accordingly to operate in PTP mode.

[0065] In some examples, there may be a dedicated Li-Fi synchronization server connected to the system, responsible for synchronizing (or aligning) the G.vlc MAC cycles 200 of different G.vlc domains. This may require aligning some common time slots to detect neighboring AP 120 and avoid interference with EP 110 located in the overlapping area of ​​neighboring AP 120. In other examples, this functionality may be implemented by the (central or distributed) control system 13 itself.

[0066] For downlink detection, the AP initially accesses the CC-AP by randomly selecting time slots. Once the LC has learned or configured which APs will interfere, it allocates time slots to each AP to avoid interference. If the LC has partial information about the interference map, it allocates a subset of time slots to each AP, from which the AP randomly selects to mitigate interference.

[0067] For uplink detection, the EP randomly selects a time slot within the CC-EP. Since the EP is mobile, this access can be less controlled by the LC (due to the dynamic location of the EP). However, each AP can instruct its registered EPs when to send presence announcements, and a round-robin scheme, for example, can be applied to determine which EP to instruct at which time.

[0068] In short, the control system 13 can mitigate interference occurring within the OWC network 100 by temporally separating the transmissions of potentially interfering devices. However, in order to perform this interference mitigation, the control system 13 requires information about the topology of the OWC network 100, specifically which devices are receiving signals from or transmitting signals to which other devices, and at what times. This information may be referred to as "interference mapping."

[0069] One way to determine at least a portion of the network topology is through the use of announcements (also known as beacons). There are two different types of announcements: AP announcements and EP announcements. Simply put, in an AP announcement, APs announce their presence, and then (multiple) EPs can let the control system 13 know which APs they can “see”; and in an EP announcement, EPs announce their presence, and then APs can let the control system 13 know which EPs they can “see”.

[0070] AP 120 announces its presence by transmitting SMAP-D frames in CC-AP. EP 110 announces its presence by transmitting SMAP-D frames in CC-EP. An SMAP-D frame is a short MAP-D frame containing only a header carrying the necessary information.

[0071] In the following example, for clarity, a simple OWC network 100 is shown, comprising a local AP 120a and a neighboring AP 120b. Assume a single EP 110 is registered to (only) the local AP 120a. One or more other EPs (not shown) may register to the neighboring AP 120b. The local AP 120a and the neighboring AP 120b are operatively coupled to the control system 13 via a backbone 21. It should be understood that there may be more APs, more EPs, or both.

[0072] Figure 3An example of an AP notification is illustrated. This example illustrates how the OWC controller (control system 13) detects whether an EP registered to an AP (local AP 120a) is within the coverage area of ​​another AP (neighboring AP 120b).

[0073] In S30, neighboring AP 120b announces its presence. This includes broadcasting an announcement or "beacon" identifying neighboring AP 120b (which, as mentioned above, can be an SMAP-D frame). Local AP 120a can also announce its presence. EP 110 receives announcements from any AP within its coverage area (including neighboring AP 120b in this example).

[0074] In S31, EP 110 sends a report to its local AP 120a, instructing it to receive the notification from its neighboring AP 120b.

[0075] In S32, the local AP 120a forwards the report to the control system 13. The control system 13 is thus informed of the APs (in this example, neighboring AP 120b) with the FoV or coverage area where the EP is located. The control system 13 can then use this information to perform one or more interference mitigation steps. For example, in Figure 3 In the configuration, the control system 13 can determine that the neighboring AP 120b is a potential source of interference for the EP 110, and therefore coordinate the communication from the local AP 120a and the neighboring AP 120b to avoid this.

[0076] like Figure 4 As illustrated schematically, AP announcements can also be performed when control system 13 is implemented in a distributed manner. Except that each AP 120 has a partition of control system 13, system 100 in this example is similar to the system in the previous example. Specifically, local AP 120a has a local portion of control system 13a, and neighboring AP 120b has a neighboring portion of control system 13b. This example illustrates the principle of partitioning and distributed control system 13 detecting whether an EP registered to an AP (local AP 120a) is within the coverage area of ​​another AP (neighboring AP 120b).

[0077] In S40, as described above, neighbor AP 120b announces its presence.

[0078] In S41, as described above, EP 110 sends a report of any received notifications to its local AP 120a.

[0079] In S42, the local AP 120a forwards the report to the local part of the control system 13a.

[0080] In S43, the local part of control system 13a forwards the report to the neighbor part of control system 13b.

[0081] Therefore, all parts of the control system 13 are informed of the (multiple) APs in the FoV or coverage area where EP 110 is located, and appropriate measures can be taken to mitigate the interference, as described above.

[0082] Figure 5 An example of an EP notice is shown schematically.

[0083] In S50, EP 110 announces its presence. This includes broadcasting a notice or "beacon" identifying the EP 110. As mentioned above, this can be an SMAP-D frame. The AP receives notices from any EP within its coverage area. Figure 5 The image shows neighboring AP120b receiving a notification from EP 110. It should be understood that local AP 120a can also receive this notification. However, this is not surprising, as EP110 is registered with local AP 120a.

[0084] In S51, the neighboring AP 120b sends a report to the control system 13 indicating that no EP (EP 110 in this example) has registered with the neighboring AP 120b and that the neighboring AP 120b has received notifications from it.

[0085] Control system 13 is thus informed of which EP FoV neighbor AP 120b is located within. Similar to the above, control system 13 can then use this information to perform one or more disturbance mitigation steps. For example, in Figure 5 In the arrangement, the control system 13 can determine that EP 110 (which is not registered to neighbor AP 120b) is a potential source of interference to neighbor AP 120b.

[0086] like Figure 6 As illustrated, when the control system 13 is implemented in a distributed manner, EP notifications can also be executed.

[0087] In this scenario, at S60, EP 110 notifies as before. At S61, neighboring AP 120b sends a report to the neighbor section of control system 13b. At S52, the neighbor section of control system 13b forwards the report to the local section of control system 13a.

[0088] For the uplink notification of EP 110 (such as in Figure 5 and Figure 6 In the example), this problem may be more pronounced than with the downlink announcement for AP 120 (as in...). Figure 3 and Figure 4The situation is more severe in the example because the density of EP 110s may be higher than that of AP 120s. For rapid interference handling, rapid detection of the cause of interference is required. In the prior art, to achieve this, announcements occur as frequently as possible. However, if many EP 110s send announcements within a limited available time (CC-EP 221) in each MAC cycle 200, numerous collisions will occur. To mitigate these collisions, the frequency at which EP 110s access CC-EP 221 can be limited under the control of the AP 120 to which EP 110s register. For example, AP 120s can apply a cyclic scheme to allocate which EP 110s can access CC-EP 221 in which MAC cycle 200. However, this disclosure recognizes that this results in greater delays in detecting which AP 120s are in which EP 110s' uplink coverage areas.

[0089] This disclosure proposes to address these issues by triggering EPs to announce their presence based on events rather than on cyclic or periodic timing used in known configurations. The EP announcements can then still be used for network topology determination and interference mitigation purposes. One advantage of this is that it allows for rapid interference handling of EPs that are suffering from or potentially suffering from uplink interference from EPs registered to another AP. For example, based on cyclic timing, an EP can be triggered to announce earlier than it would otherwise. Another advantage is that it enables separate handling of uplink and downlink interference and improves performance due to better utilization of streams.

[0090] Now for reference Figure 7 and Figure 8 Describe an example.

[0091] Figure 7 An OWC network 100 is schematically illustrated, comprising a local AP 120a, a first neighbor AP 120b, a second neighbor AP 120c, a local EP 110a, and a neighbor EP 120b. Local AP 120a, first neighbor AP 120b, and second neighbor AP 120c are operatively coupled to a control system 13 via a backbone 21. In this example, the control system 13 is a centrally implemented control system (as in...). Figure 1 , Figure 3 and Figure 5 (as in the previous example), but to understand, in other examples, control system 13 can be implemented in a distributed manner (as in...). Figure 4 and Figure 6 (as in the previous example).

[0092] For illustrative purposes, assume that local EP 110a is registered to local AP 120a, and neighboring EP 120b is registered to neighboring AP 120b. This is in Figure 7Solid arrows are used to indicate this. It is also assumed that the neighboring EP 120b is within the receiving FoV of the local AP 120a. This is determined by... Figure 7 The dashed arrow in the diagram indicates this. Therefore, neighboring EP 110b is a potential source of interference for local AP 120a.

[0093] Figure 8 An example method is illustrated schematically. Local AP 120a monitors the reception of uplink communication from its registered EP (local EP 110a in this example). In S80, local AP 120a detects events indicating interference. For example, AP 120a can determine that it has not received or has not correctly received data from local EP 110a (such as...). Figure 8 (As indicated by the broken arrow in the diagram). This can be viewed by the local AP 120a as potential interference from another EP registered to another AP (e.g., neighboring EP 110b in this example).

[0094] As discussed above, communication is synchronized within the MAC cycle. Therefore, the local AP 120a can identify time slots within one or more MAC cycles that indicate the occurrence of events that could potentially cause interference.

[0095] In S81, the local AP 120a sends a report to the control system 13, indicating that the local AP 120a has detected multiple time slots indicating an event that indicates interference.

[0096] The time slot can be indicated in the report as one or more of the following: start time and end time, start time and duration, MAC cycle number, and time slot number. Using an indication format that requires the fewest bits has the advantage of minimizing the amount of data transmitted within the OWC network 100. For example, time slots can have a predefined (fixed) duration, and their occurrence (position) within the MAC cycle can be numbered sequentially. This allows a single number to be used to indicate the time slot in the report.

[0097] In S82, the control system 13 transmits indications of time slots to one or more neighboring APs. In this example, the control system 13 transmits the indication to the first neighboring AP 120b and the second neighboring AP 120c. Generally, the control system 13 may transmit the indication to all neighboring APs within the OWC network 100, all neighboring APs within the OWC network 100 that are geographically close to the local AP 120a (e.g., within a certain distance, such as within 1 meter, several meters, or 10 meters), and only the APs that are the closest neighbors of the local AP 120a (e.g., within 1 to 3 meters).

[0098] The neighboring AP is configured to provide the control system 13 with the identifier of any neighboring EP device in response to an indication to receive (multiple) time slots, said device registering with the neighboring AP and being configured to communicate with the neighboring AP using said time slots. This is advantageous because these EPs are potential sources of interference identified by the local AP 120a, as they use the same time slots.

[0099] Alternatively or additionally, the neighboring AP is configured to provide the control system 13 with the identifier of any neighboring EP device in response to an indication to receive (multiple) time slots, said neighboring EP device being registered with the neighboring AP and scheduled to communicate with the neighboring AP using said time slots. This is advantageous because these EPs have already caused potential interference identified by the local AP 120a, since they have already used the same time slots.

[0100] The control system 13 transmits an indication of the timeslot to at least one other AP 120, so that the AP 120 provides the control system 13 with the identifier of the EP 110 or each EP 110 that is registered with the AP 120 and is using the timeslot to communicate with the AP 120 (in the event of interference). That is, the AP 120 determines whether it has any registered EP(s) using the indicated timeslot to communicate with the AP 120.

[0101] In other words, the control system 13 investigates neighboring APs to identify whether they have any EPs that are already in use or currently in use of the indicated time slot. As explained below, there are several possibilities regarding what responses are received from the neighboring APs.

[0102] In the first possibility, control system 13 may not receive any response. For example, control system 13 may not receive any response from the neighboring AP being investigated within a predetermined time limit. This could be the case, for example, if the source of interference at the local AP is a device that is not part of OWC network 100 (e.g., it might be part of another network). In this case, if the interference occurs only once in the indicated time slot, control system 13 may take no action. However, if the interference in that time slot persists (i.e., control system 13 receives at least a second indication for the same time slot), and control system 13 still does not receive any response from the neighboring AP being investigated (e.g., within the predetermined time limit), then control system 13 may exclude that time slot from communication. That is, control system 13 controls the local AP to avoid using that time slot (either entirely or with the specific EP that first identified the interference).

[0103] In the second possibility, the control system 13 can receive an identifier that identifies only a single EP. In this case, the control system 13 determines that the identified EP is the cause of the interference. This is as follows: Figure 8 As shown. In S90, the control system 13 receives the identifier of neighbor EP 110b from the first neighbor AP 120b (and receives no response from any other neighbor AP). In S91, the control system 13 determines that neighbor EP 110b is the cause of the interference initially identified by the local AP 120a. Note that the EP responsible for the interference experienced at the local AP 120a can be determined without any announcement (e.g., by sending an SMAP-D frame). Therefore, the use of network data is reduced. This reduction is proportional to the number of neighbor EPs present in the network (which would otherwise have required announcement). This also minimizes the power consumption of the EP, which is especially important in battery-powered EPs.

[0104] In a third possibility, control system 13 can receive identifiers that identify two or more EPs. In this case, control system 13 instructs the relevant neighboring APs to notify those identified EPs of their presence. This is as follows: Figure 8 As shown. In S100a, the control system 13 receives an instruction from the first neighbor AP 120b, representing the first neighbor EP. In S100b, the control system 13 receives an instruction from the second neighbor AP 120c, representing the second neighbor EP. This means that the first neighbor EP is using (or has been using) the time slot in question to communicate with the first neighbor AP 120b, and the second neighbor EP is also using (or has been using) the same time slot to communicate with the second neighbor AP 120c. Therefore, both the first neighbor EP and the second neighbor EP are potential causes of interference in that time slot identified by the local AP 120a.

[0105] In this third possibility, since the control system 13 cannot determine which neighboring EP is responsible for the interference, EP notification is used. In the example shown, this involves the control system 13 sending an instruction to the first neighboring AP 120b in S101a and to the second neighboring AP 120c in S101b. In response to the instruction, the first neighboring AP 120b and the second neighboring AP 120c instruct their respective identified EPs to notify. Then, in S102a, the first neighboring AP 120b instructs its identified EP to notify, and in S102b, the second neighboring AP 120c instructs its identified EP to notify. This notification by the identified EP can be performed according to any known technique, such as sending an SMAP-D frame in a CC-EP for each notifying EP.

[0106] In the example given above, AP 120 initially determined that problematic interference existed in the uplink direction (from EP to AP) of the received communication. Therefore, this type of interference monitoring can be referred to as "upstream monitoring." Another type of interference monitoring can be referred to as "downstream monitoring," where EP is the device initially identified as having interference. As discussed below, OWC network 100 can also perform downstream monitoring. An advantage of this disclosure is that uplink and downlink monitoring can be performed separately.

[0107] Figure 9 Additional methods that can be performed by the OWC network 100 are illustrated schematically. For illustrative purposes, it is assumed that the OWC network 100 operates similarly to the methods described above. Figure 7 Arranged in a descriptive manner.

[0108] In S110, local EP 110a detects events indicating interference. For example, EP 110a can determine that it has not received or has not correctly received data from local AP 120a. In another example, EP 110a can receive signals (such as...) from another AP to which it is not registered (e.g., AP 210b). Figure 9 (Indicated by the broken arrow in the image).

[0109] In S111, local EP 110a sends a report indicating interference or potential interference to local AP 120a.

[0110] In S112, the local AP 120a relays the report to the control system 13. As described above, the control system 13 can be implemented locally (or in a distributed manner) on the local AP 120a. Therefore, the relay of the report can include reports that are "internally" passed from the local AP 120a to the control system 13 (or a part of the control system 13).

[0111] In S113, the control system 13 instructs the local EP 110a to announce its presence.

[0112] In S114, local EP 110a announces its presence. Although EP 110a may not currently interfere with any EP registered to another AP, it is highly likely that it will interfere at some point. Therefore, this has the advantage of local EP 110a notifying another AP 120b of its presence. Appropriate interference mitigation steps can then be taken. Note that these mitigation steps can even be implemented before interference occurs.

[0113] In some examples, control system 13 is configured to check whether the applied mitigation steps(s) have actually reduced the amount of interference. This can be done for one or both of uplink and downlink monitoring. For example, control system 13 may determine that uplink interference persists in a time slot used by a particular EP 110 despite the mitigation steps(s). In this case, control system 13 may remove the time slot from the allowed uplink time slots of that EP 110. If EP 110 reports a change in the current situation—for example, EP 110 detects a change in AP announcements (which could be due to a change in the EP's orientation toward the AP)—control system 13 may determine to re-add the time slot to the allowed time slots of that EP 110.

[0114] Finally, as a result of the report, there may be additional scheduling constraints. In these cases, the number of allowed time slots (the “allowed area” of a particular EP) may be appropriately reduced.

[0115] The term "controller" is used herein to generally describe various means relating to the operation of one or more network devices or coordinators—among other functions. A controller can be implemented in a variety of ways (e.g., such as with dedicated hardware) to perform the various functions discussed herein. A "processor" is an example of a controller employing one or more microprocessors, which can be programmed using software (e.g., microcode) to perform the various functions discussed herein. A controller can be implemented with or without a processor, and can also be implemented as a combination of dedicated hardware performing some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) performing other functions. Examples of controller components that can be employed 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).

[0116] In various embodiments, the processor or controller may be associated with one or more storage media (collectively referred to herein as "memory," such as volatile and non-volatile computer memories, such as RAM, PROM, EPROM, and EEPROM, compact disks, optical disks, etc.). In some embodiments, the storage media may be encoded with one or more programs that, when executed on one or more processors and / or controllers, perform at least some of the functions discussed herein. Various storage media may be fixed within the processor or controller, or may be transportable, such that one or more programs stored thereon may be loaded into the processor or controller to implement various aspects of the invention discussed herein. The terms "program" or "computer program" are used herein in a general sense to refer to any type of computer code (e.g., software or microcode) that can be used to program one or more processors or controllers.

[0117] As used herein, the term “network” refers to any interconnection of two or more devices (including controllers or processors) that facilitates the transport of information (e.g., for device control, data storage, data exchange, etc.) between any two or more devices and / or between multiple devices coupled to the network.

[0118] Although at least some aspects of the embodiments described herein with reference to the accompanying drawings include computer processes executed in a processing system or processor, the invention also extends to computer programs suitable for practicing the invention, particularly computer programs on or in a carrier. The program may be in the form of non-transitory source code, object code, code between source and object code (e.g., partially compiled), or any other non-transitory form suitable for implementing the processes according to the invention. The carrier may be any entity or device capable of carrying the program. For example, the carrier may include: storage media, such as solid-state drives (SSDs) or other semiconductor-based RAM; ROM, such as CD ROMs or semiconductor ROMs; magnetic recording media, such as floppy disks or hard disks; general optical storage devices; and so on.

[0119] The examples described herein should be understood as illustrative examples of embodiments of the invention. Further embodiments and examples are contemplated. Any feature described with respect to any example or embodiment may be used alone or in combination with other features. Furthermore, any feature described with respect to any example or embodiment may also be used in combination with one or more features of any other example or embodiment, or in any combination of any other example or embodiment. Moreover, equivalents and modifications not described herein may be employed within the scope of the invention as defined in the claims.

Claims

1. A control system (13) for an optical wireless communication OWC network (100), wherein the OWC network (100) includes multiple access points (120) for communicating with multiple endpoint devices (110) via modulated light, the control system (13) being configured to: In response to receiving a report indicating a time slot, the indication of the time slot is transmitted to at least one other access point (120b), during which a first access point (120a) of the access points detects an event indicating interference; The control system is characterized by: The instruction causes the other access point (120b) to provide the control system (13) with the identifier of the endpoint device or each endpoint device that is registered with the other access point (120b) and is communicating with the other access point (120b) using the time slot; and In response to receiving an identifier of a single endpoint device from the other access point (120b), the single endpoint device identified by the identifier is determined as the cause of the interference experienced at the first access point (120a); and In response to receiving identifiers of multiple endpoint devices from one or more of the other access points (120), the one or more other access points (120) instruct the endpoint devices registered to the one or more other access points (120) to announce their presence.

2. The control system (13) according to claim 1, wherein, The control system (13) is configured to transmit an indication of the time slot to one or more other access points that are closest to the first access point (120a).

3. The control system (13) according to claim 2, wherein, The control system (13) is configured to transmit an indication of the time slot to at least one other access point physically located within a threshold distance of the first access point (120a).

4. The control system (13) according to claim 1, wherein, The control system (13) is configured to transmit an indication of the time slot to at least one other access point physically located within a threshold distance of the first access point (120a).

5. The control system (13) according to any one of claims 1, 3 and 4, wherein, The control system (13) is configured to transmit an indication of the time slot to at least one other access point, which has an overlap of more than a threshold with the first access point (120a).

6. The control system (13) according to any one of claims 1, 3 and 4, wherein, The control system (13) is configured to transmit the time slot indication to all other access points in the same building room as the first access point (120a).

7. The control system (13) according to any one of claims 1, 3 and 4, wherein, The control system (13) is configured to transmit the indication of the time slot to all other access points in the OWC network (100).

8. The control system (13) according to any one of claims 1, 3 and 4, wherein, The control system (13) is configured to: in response to receiving a report from an endpoint device (110) registered to one of the access points (120) indicating interference from at least one neighboring access point, cause the endpoint device to announce its presence.

9. The control system (13) according to any one of claims 1, 3 and 4, implemented at the first access point (120a).

10. The control system (13) according to any one of claims 1, 3 and 4 is implemented in a distributed manner across multiple access points.

11. A method performed by the control system (13) according to claim 1, the method comprising: Receive a report of an indicated time slot during which the first access point (120a) detected an event indicating interference; In response to receiving the report, an indication of the time slot is transmitted to at least one other access point (120b); The method is characterized by: Receiving the indication of the time slot causes the other access point (120b) to provide the control system (13) with the identifier of the endpoint device or each endpoint device that has registered with the other access point (120b) and is using the time slot to communicate with the other access point (120b). In response to receiving an identifier of a single endpoint device from the other access point (120b), the single neighboring endpoint device identified by the identifier is determined as the cause of the interference experienced at the first access point (120a); and In response to receiving identifiers of multiple neighboring endpoint devices from one or more of the other access points (120), the one or more other access points (120) instruct the endpoint devices registered to the one or more other access points (120) to announce their presence.

12. The method of claim 11, comprising: In response to receiving a report from an endpoint device registered to one of the access points indicating interference from at least one neighboring access point, the endpoint device announces its presence.

13. An access point (120) for an optical wireless communication OWC network, for communicating with at least one endpoint device (110) via modulated light, said access point (120) being configured to: The system (13) receives an indication of a time slot from the control system according to claim 1, during which another access point detects an event indicating interference; The access point is characterized in that it is configured as follows: In response to receiving the instruction, an endpoint device (110) registered to the access point (120) and communicating with the access point (120) using the time slot is identified; and the identifier of the endpoint device (110) is provided to the control system (13).

14. A method performed by an access point (120) according to claim 13, the method comprising: The control system (13) receives an indication of a time slot from the control system according to claim 1, during which another access point detects an event indicating interference, and The method is characterized by: In response to receiving the instruction, an endpoint device (110) registered to the access point (120) and communicating with the access point (120) using the time slot is identified. as well as The identifier of the endpoint device (110) is provided to the control system (13).

15. An optical wireless communication OWC system (100), characterized in that, It includes a control system (13) according to any one of claims 1 to 10 and a plurality of access points (120) according to claim 13.

Images