Subsystem for optical wireless communication

Abstract

A subsystem (100) for connecting a terminal device (200) to a first network (300) or a second network (400) via optical wireless communication; wherein the first network (300) and the second network (400) have different security levels and / or priority levels, the subsystem (100) comprising: a first communication interface (110) configured to provide a connection to the first network (300); a second communication interface (120) configured to provide a connection to a second network (400); an optical front end (OFE) (130) comprising a light source (131) configured to emit optical data to the terminal device (200) and a light detector (132) configured to receive optical data from the terminal device (200); a combiner (140) connected between the light source (131) and the first and second communication interfaces, configured to combine the analog signals received from both the first and second communication interfaces and provide the combined signals to the light source (131) for transmission; and a splitter (150) connected between the light detector (132) and the first and second communication interfaces, configured to split the analog signal received from the light detector (132) and provide to the first communication interface (110) or the second communication interface (120).

Description

Technical Field

[0001] The present invention relates to the field of optical wireless communications, such as Li-Fi communications. More particularly, various devices and systems are disclosed herein that relate to efficient deployment of optical wireless communications that access multiple external networks. Background Art

[0002] To enable more and more electronic devices (such as laptops, tablets and smartphones) to connect wirelessly to the Internet, wireless communications face unprecedented requirements for data rates and link quality, and these requirements continue to grow year by year in view of the emerging digital revolution related to the Internet of Things (IoT). Radio frequency technologies (such as Wi-Fi) have limited spectrum capacity and are unable to meet this revolution.

[0003] At the same time, optical wireless communications (OWC) have attracted increasing attention due to their inherent security enhancements and ability to support higher data rates over available bandwidths in the visible, ultraviolet (UV) and infrared (IR) spectra. Depending on, for example, the wavelength used, this technology may also be referred to as coded light, light fidelity (LiFi), visible light communications (VLC), or free space optics (FSO). As compared to Wi-Fi, OWC or Li-Fi is directional and shielded by light-blocking materials, which provides it with the potential to deploy a larger number of access points in areas with dense users by spatially reusing the same bandwidth. These key advantages over wireless RF communications make OWC or Li-Fi a promising and secure solution to alleviate the pressure on the radio spectrum that is crowded with IoT applications and indoor wireless access. Other possible benefits of Li-Fi may include guaranteed bandwidth for certain users and the ability to operate safely in areas that are otherwise susceptible to electromagnetic interference. Therefore, Li-Fi is a very promising technology for enabling the next generation of immersive connectivity.

[0004] There are also scenarios where multiple networks need to be deployed in the same area to meet different application requirements. For example, when there are two external networks to be deployed, two optical access points (APs) may be needed to provide the last few meters of connectivity for end users. If there is an overlap between the wavelengths used by the two APs and / or if they transmit simultaneously, the two optical APs may interfere with each other.

[0005] One way to enable two wireless optical networks to coexist in the same area without interference is to apply different wavelengths to each network. However, this solution presents several constraints and drawbacks:

[0006] - Limitation on the number of “off-the-shelf” wavelengths in the IR spectrum: only a few LEDs can provide reasonably high power to guarantee large coverage (i.e. 850nm and 940nm);

[0007] - An IR filter (low-pass, high-pass or band-pass) needs to be placed in front of the optical receiver to provide sufficient attenuation of unwanted wavelengths, and these IR filters are expensive;

[0008] - Performance degradation with respect to temperature: LEDs typically exhibit a peak wavelength shift with respect to temperature (ie, a wavelength shift of 25 nm over a temperature change of 70° C.), which results in a loss of optical received power due to the fixed cut-off frequency of the IR filter.

[0009] Another method to enable two wireless optical networks to coexist in the same area without interference is to apply a channel access control method of time division multiple access (TDMA). Some baseband modules for optical wireless communications have controllable time slots. For example, by synchronizing the baseband modules, it is possible to schedule transmissions from multiple adjacent optical APs by allowing only one optical AP to transmit at a time.

[0010] US2018157001A1 relates to an optical bridge for providing communication between an external network and a residential network.

[0011] US2002131123A1 relates to a free space optical communication network for building to building communications.

[0012] EP3300264A1 relates to a repeater system for RF communications, and the backhaul network may be based on optical communications. Summary of the invention

[0013] To provide connectivity to multiple external networks in the same area, more than one optical AP would be required using off-the-shelf components. As mentioned above, the coexistence of multiple optical APs in the same area can be solved by using TDMA scheduling between multiple optical APs. However, this solution is still complex and bulky because it means installing a complete access point for each external network.

[0014] In view of the above, the present disclosure relates to an apparatus and system for providing an efficient solution for deploying an optical wireless communication system including a single optical front end (OFE) providing a terminal device with connections to multiple external networks. More particularly, the object of the present invention is achieved by a subsystem as claimed in claim 1.

[0015] According to a first aspect of the present invention, a subsystem is provided. A subsystem, which is part of an optical access point, is used to connect a terminal device to a first network or a second network via optical wireless communication; wherein the first network and the second network have different security levels and / or priority levels, and the subsystem comprises: a first communication interface, which is configured to provide a connection to the first network; a second communication interface, which is configured to provide a connection to the second network; an optical front end OFE, which comprises a light source configured to transmit optical data to the terminal device and a light detector configured to receive optical data from the terminal device; a combiner, which is connected between the light source and the first and second communication interfaces, is configured to combine analog signals received from both the first and second communication interfaces, and provides the combined analog signal to the light source for transmission; and a separator, which is connected between the light detector and the first and second communication interfaces, is configured to separate the analog signal received from the light detector, and provides the analog signal to the first communication interface or the second communication interface.

[0016] The subsystem is used to provide connections to multiple external networks (such as a first network and a second network). The external network can be a wired network or a wireless network. It is also possible that one of the external networks is a wired network and the other of the external networks is a wireless network. The wired network can be Ethernet. The wireless network can be based on a millimeter wave communication system or a 5G cellular network.

[0017] Optical wireless communication can be performed in the visible, ultraviolet (UV) and infrared (IR) light spectrum. Therefore, optical wireless communication can also be called Li-Fi communication or visible light communication (VLC). Most optical wireless communication uses infrared or near infrared spectrum contained between 780nm and 2500nm. In order to deploy multiple optical wireless communication systems for different networks in the same area, interference can be reduced by selecting different wavelengths for each communication system.

[0018] The optical front end (OFE) may include at least a light source for optical data transmission and a light detector for optical data reception. For transmission, the OFE is used to convert an electrical transmission signal into an output optical signal via a light source. For reception, the OFE is used to convert a received optical signal into an output electrical signal via a light sensor for further signal processing. The light source or light emitter may be one of a light emitting diode (LED), a laser diode, a vertical cavity surface emitting laser (VCSEL), or an edge emitting laser diode (EELD). Preferably, the light source includes at least one of an LED and a VCSEL. The light detector (also called a photodetector or a photoelectric sensor) is a photodiode, which may be a PIN diode, an avalanche photodiode (APD), or a photomultiplier tube.

[0019] By sharing the same OFE between the first and second communication interfaces, no additional measures are needed to avoid interference between the optical wireless communications for the two external networks to the end users in the coverage area. It also makes the subsystem more cost effective with reduced hardware components.

[0020] Note that the subsystem is not limited to providing the end user with connections to two different networks. By reusing the same OFE, the same subsystem architecture can be extended to provide the end user with connections to more than two different networks.

[0021] It may be possible to share the same OFE between two or more network interfaces with a pass-through option. And then the collision between data flows from different networks will depend on the actual traffic load. If the traffic load of both networks is low, the collision rate may still be low. However, it may be more efficient to share a single OFE in a coordinated manner.

[0022] Preferably, the subsystem is configured to use the OFE to connect to the first network or the second network on a time-sharing basis.

[0023] Beneficially, some optical wireless communication protocols support medium access control with controllable time slots. For example, in a system with time division multiple access (TDMA), a medium access control (MAC) frame / cycle is divided into multiple time slots. By assigning each time slot to a single network interface, two network interfaces can use a single OFE without interfering with each other.

[0024] Advantageously, the subsystem is configured to set a time schedule for using the OFE to connect to the first network or the second network according to different security levels and / or priority levels.

[0025] A network with a higher security level and / or priority level may have the opportunity to use a single OFE for a longer period of time, allowing the subsystem to prioritize traffic for that network.

[0026] In one option, the subsystem is configured to set the time schedule by further considering a predetermined traffic load regarding use of the first network and the second network.

[0027] The predetermined traffic load may be based on configurable parameters or historical data from earlier use of the system. And then, the time schedule is determined based on the priority level and / or security level of each individual network in combination with the predetermined traffic load information.

[0028] The time schedule may also be determined dynamically or adaptively so that real-time traffic load or user requests may be used as an additional factor.

[0029] Advantageously, the first and second communication interfaces respectively include a first baseband module and a second baseband module, wherein the first baseband module is configured to perform bidirectional data conversion between a baseband signal of the first network and a baseband signal suitable for OFE, and the second baseband module is configured to perform bidirectional data conversion between a baseband signal of the second network and a baseband signal suitable for OFE.

[0030] Each of the two communication interfaces includes a dedicated baseband module to achieve bidirectional data conversion between the separate external network and the optical wireless communication system. Therefore, different baseband modules can be used depending on the communication protocol used by the separate external network.

[0031] Advantageously, the baseband signal suitable for OFE is modulated according to Orthogonal Frequency Division Multiplexing (OFDM) or On-Off Keying (OOK).

[0032] OFDM is widely used as a digital multi-carrier modulation method in many communication systems because of its great robustness advantage against harsh channel conditions such as narrowband interference or frequency selective fading. By dividing the entire frequency band into multiple subcarriers, the system also has the flexibility to apply different modulation and coding schemes to individual subcarriers, which can be used to maximize the capacity of the channel. For optical wireless communications, single-pole OFDM modulation techniques such as ACO-OFDM, DCO-OFDM, ADO-OFDM and / or flipped OFDM are usually adopted.

[0033] With OOK encoding, the optical light is pulsed on or off during each bit time. Each "1" bit is encoded into an optical pulse, and each "0" bit is encoded into an off period. Therefore, the maximum bit rate to be supported is directly related to the speed at which the light source can be turned on and off. Typically, lasers and LEDs can be switched at rates up to hundreds of megahertz, and OOK modulation represents a simple process for producing relatively high bit rates. By interleaving OOK bit streams from several different lasers, even higher data rates, such as gigabit rates, can be achieved.

[0034] In a preferred arrangement, the subsystem further comprises a reference clock configured to synchronize the baseband modules of the first and second communication interfaces.

[0035] When the baseband modules support the slotted MAC protocol, it is beneficial to synchronize two or more baseband modules with a reference clock and then apply time scheduling using a single OFE.

[0036] Advantageously, the first and second communication interfaces also include a first analog front end (AFE) module and a second AFE module, respectively; wherein the first AFE module is configured to perform bidirectional conversion between digital signals going to / from the first baseband module and analog signals going to the combiner or from the separator, and the second AFE module is configured to perform bidirectional conversion between digital signals going to / from the second baseband module and analog signals going to the combiner or from the separator.

[0037] In one example, at least one of the first network and the second network is a wired network.

[0038] As mentioned above, the two or more external networks may be of the same type or of different types. Preferably, at least one of the first network and the second network is a wired network. And even more preferably, the wired network is Ethernet.

[0039] In one example, the subsystems are contained within a single housing.

[0040] For example, the subsystem can be deployed on a ceiling as a standalone optical access point (AP). The subsystem can also be deployed in a single enclosure as part of another electronic device, such as a luminaire.

[0041] In one arrangement, the subsystem is assembled in a pole and the OFE is placed on one side of the pole.

[0042] The pole includes multiple baseband modules, each corresponding to a different network. The multiple baseband modules are all connected to a single OFE. It is beneficial to deploy a single OFE at one end of the pole, such as the top of the pole. The pole or stick can be used as an access point (AP) inside a room or tent and placed on a table or another piece of furniture to improve the coverage area of ​​the AP.

[0043] Similarly, this subsystem can also be used to build a LiFi Endpoint (EP) pole, which consists of multiple basebands and all connected to a single OFE. A horizontal OWC link can be established between the LiFi AP pole and the LiFi EP pole, so that devices connected to the LiFi EP pole can access different networks.

[0044] Advantageously, the optical wireless communication is according to the Li-Fi standard.

[0045] As a derivative of optical wireless communication, Li-Fi provides high data rate communication over available bandwidth in the visible, ultraviolet (UV) and infrared (IR) spectrum. There are different standardization activities related to Li-Fi communication. The ITU G.9991 standard for indoor visible light communication (VLC) is one of the earliest standards for high-speed wireless communication using visible light and infrared. The IEEE has established the IEEE 802.11bb task group to develop and approve the global standard for Li-Fi. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In the drawings, similar reference numerals are used throughout the different Figure 1 Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

[0047] Figure 1 A block diagram showing the basic setup of the subsystem;

[0048] Figure 2 A block diagram showing another basic arrangement of the subsystem;

[0049] Figure 3 The diagram shows the time scheduling of two networks sharing one OFE in a subsystem;

[0050] Figure 4 Shows examples of implementing subsystems;

[0051] Figure 5 Another example of implementing a subsystem is shown;

[0052] Figure 6 illustrates an example implementation of a subsystem in a single housing, and

[0053] Figure 7 An example implementation of the subsystems in a distributed manner is illustrated. DETAILED DESCRIPTION

[0054] The embodiments set forth below represent information that enables those skilled in the art to practice these embodiments. After reading the following description in light of the accompanying drawings, those skilled in the art will understand the concepts of the present disclosure and will recognize the applications of these concepts, which are not particularly set forth herein. It should be understood that these concepts and applications fall within the scope of the present disclosure.

[0055] In some application scenarios, terminal devices in the same area may need to access different external networks, which may have different domains, security levels and / or priority levels. Example use cases include scenarios where accessibility is required for both public and private networks in the same area (such as hotels, public sectors and enterprises). Other applications include military and defense, such as providing accessibility to multiple networks with different security levels. In order to provide connections to these multiple external networks in the same area, more than one optical AP will be required to build a system using off-the-shelf components, where each individual optical AP is connected to a different external network. Interference avoidance between multiple APs can be handled by using wavelength multiplexing or TDMA. However, these traditional interference avoidance techniques have certain limitations and disadvantages, which add additional complexity and overhead to the system. For example, in order to coordinate multiple co-located APs according to wavelength multiplexing or TDMA, where each AP is connected to a different external network, a controller may be required to schedule and allocate wavelength or time resources. In addition, multiple co-located APs need to be synchronized to make such scheduling of the controller effective.

[0056] In order to solve this problem, a subsystem is disclosed in the present invention, which includes a single optical front end (OFE) for interfacing between a terminal device and multiple external networks. Figure 1 A block diagram showing a basic setup of a subsystem 100 is shown. The subsystem 100 is used to connect a terminal device to a plurality of external networks, such as a first network 300 or a second network 400, via optical wireless communication. The plurality of external networks, such as the first network 300 and the second network 400, belong to different domains with different security levels and / or priority levels, which may be wired networks or wireless networks.

[0057] As an example, in the use case of an interior tent of a command post, soldiers will simultaneously access different networks, such as NATO Confidential and NATO Restricted. Moreover, there are two key parameters on the battlefield: installation time, which should be as short as possible; and weight savings of military supplies that should be transported by aircraft and / or trucks. For these reasons, a solution that uses one single optical transceiver to transmit data from multiple networks is a key advantage, as it reduces wiring, weight and installation time.

[0058] As a basic setup, the subsystem 100 includes a first communication interface 110, a second communication interface 120, an optical front end (OFE) 130, a combiner 140, and a splitter 150. The first communication interface 110 is configured to provide a connection to the first network 300, so that it provides a bidirectional signal conversion between the first network 300 and the optical wireless communication network. Similarly, the second communication interface 120 is configured to provide a bidirectional signal conversion between the second network 400 and the optical wireless communication network. The optical front end is used to achieve the conversion between electrical signals and optical signals. OFE 130 includes at least a light source 131 for optical data transmission and a light detector 132 for optical data reception. In the transmitter chain, the OFE is used to convert the electrical transmission signal into an output optical signal via a light source. In the receiver chain, the OFE is used to convert the received optical signal into an output electrical signal via a light sensor for further signal processing. The light source or light transmitter can be one of a light emitting diode (LED), a laser diode, a vertical cavity surface emitting laser (VCSEL), or an edge emitting laser diode (EELD). Preferably, the light source comprises at least one of an LED and a VCSEL. The light detector (also called a photodetector or a photosensor) is a photodiode, which may be a PIN diode, an avalanche photodiode (APD) or a photomultiplier tube.

[0059] The combiner 140 connected between the light source 131 and the first and second communication interfaces is configured to combine the analog signals received from both the first and second communication interfaces and provide them to the light source 131 for transmission. The separator 150 connected between the light detector 132 and the first and second communication interfaces is configured to separate the analog signals received from the light detector 132 and provide them to the first communication interface 110 or the second communication interface 120.

[0060] Thus, the first and second communication interfaces 110, 120, the combiner 140 and the OFE 130 form a transmitter chain for optical wireless communication. The OFE 130, the splitter 150 and the first and second communication interfaces 110, 120 form a receiver chain for optical wireless communication. The OFE 130, the combiner 140 and the splitter 150 are shared components in the subsystem for providing connections to different external networks. Note that the subsystem is not limited to providing connections to two different networks to a terminal device. By reusing the shared components of the OFE 130, the combiner 140 and the splitter 150, and adding additional communication interfaces in addition to the first and second communication interfaces 110, 120, the same subsystem architecture can be extended to provide connections to more than two different networks to a terminal device. In fact, the same OFE 130 can be used to provide access to three, four or even more external networks to a terminal device.

[0061] The shared OFE 130 may be used to connect the terminal device to the first network 300 or the second network 400 on a time-sharing basis. For example, the subsystem may determine a time schedule for using the OFE 130 based on different security levels and / or priority levels associated with the first and second communication networks 300, 400. The time schedule may be determined by further considering a predetermined traffic load using the first network 300 and the second network 400.

[0062] Figure 2 1 shows a block diagram of another basic arrangement of the subsystem 100. The first and second communication interfaces include a first baseband module 111 and a second baseband module 121, respectively. The first baseband module 111 is configured to perform bidirectional data conversion between a baseband signal of the first network 300 and a baseband signal suitable for the OFE 130, and the second baseband module 121 is configured to perform bidirectional data conversion between a baseband signal of the second network 400 and a baseband signal suitable for the OFE 130. The baseband signal suitable for the OFE 130 may be modulated according to orthogonal frequency division multiplexing (OFDM) or on-off keying (OOK). For example, if the first and second networks are Ethernet, the first communication interface 110 and the second communication interface 120 respectively use a dedicated baseband chipset (such as the first baseband module 111 and the second baseband module 121) to convert the Ethernet data into a baseband signal suitable for optical communication, such as using OFDM or OOK modulation.

[0063] The first and second communication interfaces may further include a first analog front end (AFE) module 112 and a second AFE module 122, respectively. The first AFE module 112 is configured to perform bidirectional conversion between digital signals to / from the first baseband module 111 and analog signals to / from the combiner 140 or from the splitter 150. The second AFE module 122 is configured to perform bidirectional conversion between digital signals to / from the second baseband module 121 and analog signals to / from the combiner 140 or from the splitter 150. For example, the first AFE module 112 is configured to convert a digital signal received from the first baseband module 111 into an analog signal to be sent to the combiner 140, and to convert an analog signal received from the splitter 150 into a digital signal to be sent to the first baseband module 111. Similarly, the second AFE module 122 is configured to convert a digital signal received from the second baseband module 121 into an analog signal to be sent to the combiner 140, and to convert an analog signal received from the splitter 150 into a digital signal to be sent to the second baseband module 121.

[0064] Figure 3The time scheduling of two networks sharing one OFE 130 in the subsystem 100 is illustrated. Advantageously, some baseband modules for optical wireless communication have controllable time slots. For example, in a system with time division multiple access (TDMA), one medium access control (MAC) frame / cycle is divided into multiple time slots. By synchronizing the baseband modules of more than one network interface, it is possible to select the transmission from the first baseband module or the second baseband module. Thus, two network interfaces 110, 120 can share a single OFE 130 without interfering with each other.

[0065] Figure 4 An example of implementing subsystem 100 is shown. In this example, the first and second networks are based on the Smart Ethernet Protection (SEP) protocol, which is a ring network protocol specifically for the Ethernet link layer. Each network interface includes a SEP to Ethernet adapter. Each network interface also includes its dedicated baseband chipset to convert Ethernet data into a modulated signal / demodulated signal with the appropriate modulation type (i.e., OFDM, OOK).

[0066] Because time division is applied to the transmission / reception between the two networks, a single optical front-end module can be used. In this example, the time scheduling between the two communication interfaces when using the shared OFE 130 can be achieved by synchronizing the baseband modules, digital front ends (DFEs) of the first and second communication interfaces using a reference clock SYNCHRO.

[0067] Figure 5 Another example of implementing subsystem 100 is shown. In this example, both the first and second networks are based on the Ethernet protocol. Note that the two networks and / or additional networks can be based on the same or different communication protocols. For example, it is also possible that one of the external networks is a wired network and the other of the external networks is a wireless network. The wired network can be Ethernet. The wireless network can be based on a millimeter wave communication system or a 5G cellular network. Different networks are associated with different domains, different priorities, or different security levels.

[0068] By sharing the same OFE between multiple network interfaces in a subsystem, interference handling can be addressed within the subsystem, such as scheduling multiple baseband modules accordingly. Different priorities and / or different security levels can also be reflected in the scheduling using a single OFE. For example, a network with a higher priority and / or security level can use the OFE for a longer period of time to meet strict latency requirements, while another network with a lower priority and / or security level can occupy the OFE for a shorter period of time. Scheduling can also be determined by considering additional factors, such as the typical traffic load on a certain network.

[0069] By synchronizing two or more baseband modules, scheduling can be implemented as a fixed-time scheduling, where each baseband module corresponds to a separate network. In another option, the subsystem 100 may further include a controller for dynamically controlling two or more network interfaces when using a single OFE module 130 based on one or more other factors (such as real-time traffic information or user requests). In another example, it may also be possible to determine the scheduling by considering the presence of certain terminal devices. For example, if terminal devices are only allowed to access low-security level networks and not high-security level networks, it is also more efficient to allocate more time to low-security level networks to use a single OFE module 130. In another example, if there are only one or more terminal devices connected to a high-security level network, it is also effective to temporarily suspend the low-security level network interface.

[0070] Depending on the use case, the OFE 130 can have a narrow beam or a wide beam. For example, in a use case of deploying LiFi in a military tent, it is preferable to share the same OFE between several different networks and still present a large coverage area of ​​the OFE with a + / - 45 degree beam angle. For vehicle-to-vehicle communications where the distance between two vehicles may be long (e.g., hundreds of meters) and may require switching between multiple networks (e.g., voice and data), a narrow beam may be more beneficial (e.g., 1 degree beam angle). In this case, bulky optics (e.g., Fresnel lenses) may be required to reach long distances, and sharing one OFE (one optic) between multiple networks is a real advantage.

[0071] The subsystem can be contained in a single housing. For example, the subsystem can be deployed on a ceiling as a standalone optical access point. The subsystem can also be deployed in a single housing as part of another electronic device, such as a luminaire.

[0072] In another example, the subsystem may be implemented as a LiFi access point (AP) pole, such as Figure 6 The pole includes multiple basebands for different networks, which are all connected to a single OFE, and the OFE transmits and receives data from multiple networks (such as in a TDMA-based approach). Similarly, this subsystem can also be used to build a LiFi Endpoint (EP) pole, which consists of multiple basebands and is all connected to a single OFE. A horizontal OWC link can be established between the LiFi AP pole and the LiFi EP pole so that devices connected to the LiFi EP pole can access different networks. The OFE can be deployed at one end of the pole, such as the top of the pole.

[0073] Alternatively, the subsystems can also be implemented in a distributed manner, such as Figure 7As shown in . For example, the two network interfaces can be contained in a single or two separate housings and placed close to an Ethernet switch. The outputs of the two network interfaces are connected to a single OFE, which transmits and receives data from multiple networks. The reference clock SYNCHRO can be used to synchronize the two network interfaces for sharing a single OFE in a time division multiple access method. LiFi endpoints (EPs) can have a dedicated service set identifier (SSID) for connecting to a specific network, and will be connected to their corresponding networks when placed under the coverage area of ​​the OFE. In a given area, only one cable and one OFE are needed to transmit data of multiple networks.

Claims

1. A subsystem (100), which is part of an optical access point, for connecting a terminal device (200) to a first network (300) or a second network (400) via optical wireless communication; wherein the first network (300) and the second network (400) have different security levels and / or priority levels, the subsystem (100) comprising: - a first communication interface (110) configured to provide a connection to a first network (300); - a second communication interface (120) configured to provide a connection to a second network (400); - an optical front end OFE (130) comprising a light source (131) configured to transmit optical data to a terminal device (200) and a light detector (132) configured to receive optical data from the terminal device (200); a combiner (140) connected between the light source (131) and the first and second communication interfaces, configured to combine analog signals received from both the first and second communication interfaces and to provide the combined analog signal to the light source (131) for transmission; and A separator (150) connected between the optical detector (132) and the first and second communication interfaces, configured to separate the analog signal received from the optical detector (132) and provide the analog signal to the first communication interface (110) or the second communication interface (120).

2. The subsystem (100) of claim 1, the subsystem (100) being configured to use the OFE (130) to connect to the first network (300) or the second network (400) on a time-sharing basis.

3. The subsystem (100) according to claim 2, wherein the subsystem (100) is configured to set a time schedule for connecting to the first network (300) or the second network (400) using the OFE (130) according to different security levels and / or priority levels.

4. The subsystem (100) according to claim 3, the subsystem (100) being configured to set the time schedule by further considering a predetermined traffic load regarding the use of the first network (300) and the second network (400).

5. A subsystem (100) according to any one of the preceding claims, wherein the first communication interface and the second communication interface respectively include a first baseband module (111) and a second baseband module (121), wherein the first baseband module (111) is configured to perform bidirectional data conversion between a baseband signal of the first network (300) and a baseband signal suitable for OFE (130), and the second baseband module (121) is configured to perform bidirectional data conversion between a baseband signal of the second network (400) and a baseband signal suitable for OFE (130).

6. The subsystem (100) according to claim 5, wherein the baseband signal applied to the OFE (130) is modulated according to Orthogonal Frequency Division Multiplexing (OFDM) or On-Off Keying (OOK).

7. The subsystem (100) according to claim 5 or 6, wherein the subsystem (100) further comprises a reference clock, wherein the reference clock is configured to synchronize baseband modules of the first communication interface and the second communication interface.

8. The subsystem (100) according to any one of the preceding claims 5-7, wherein the first communication interface and the second communication interface further comprise a first analog front end AFE module (112) and a second AFE module (122), respectively; The first AFE module (112) is configured to perform bidirectional conversion between digital signals to / from the first baseband module (111) and analog signals to a combiner (140) or from a separator (150), and the second AFE module (122) is configured to perform bidirectional conversion between digital signals to / from the second baseband module (121) and analog signals to a combiner (140) or from a separator (150).

9. The subsystem (100) according to any one of the preceding claims, wherein at least one of the first network (300) and the second network (400) is a wired network.

10. The subsystem (100) according to any one of the preceding claims, wherein the subsystem (100) is contained in a single housing.

11. The subsystem (100) according to claim 10, wherein the subsystem (100) is assembled in a pole and the OFE (130) is placed on one side of the pole.

12. The subsystem (100) according to any of the preceding claims, wherein the optical wireless communication is according to the Li-Fi standard.

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