LiFi module, mobile device including a LiFi module, and method for initiating a handover of a user device - Patents.com

Abstract

A LiFi module for operatively connecting to a WiFi communication module supporting both Wi-Fi and Li-Fi connections is disclosed. The LiFi module includes an optical front end (OFE) and a connection circuit for communicatively connecting the OFE to the WiFi communication module. The connection circuit includes a switching element electrically connected to the LiFi signal strength detector and configured to enable or disable a connection between the OFE and the WiFi communication module under the control of the LiFi signal strength detector, and a LiFi signal strength detector electrically connected to the switching element and a receive path of the OFE and configured to detect a strength of an optical signal received on the receive path of the OFE and to control the switching element based on the detected strength of the optical signal.

Description

[Technical field]

[0001] The present disclosure relates generally to the field of wireless communications, and more specifically to a LiFi module, a mobile device including a LiFi module, and a method for initiating handover of a user device. [Background technology]

[0002] Today, more and more devices are connected to the Internet, most of which are wireless. This puts traditional wireless communication technologies that use Radio Frequency (RF) technology under great pressure for two reasons: first, the RF spectrum is becoming quite crowded, and secondly, there are areas where RF wireless communication is not permitted or does not fit well.

[0003] The recently developed LiFi technology is a wireless communication technology that uses light to transmit or communicate data between devices, for example, via the visible, ultraviolet, and infrared spectrum.

[0004] Wireless LiFi communication can have advantages over wireless RF communication in a number of ways: for example, the optical spectrum used by LiFi is much broader than the RF spectrum, offering higher data rates and allowing use in areas susceptible to electromagnetic interference, such as aircraft. Additionally, communication over light supports significantly higher data density than RF due to the nearly unlimited bandwidth of the visible / invisible light spectrum.

[0005] On the other hand, LiFi communication has limited coverage because light cannot penetrate walls, etc. Furthermore, most of the devices currently available use hardware that is only for WiFi networking, making them incompatible with LiFi technology.

[0006] In view of the above, it would be more desirable to use both WiFi and LiFi technologies together, allowing users to experience the benefits of both WiFi and LiFi communications.

[0007] Proposed solutions for using WiFi and LiFi simultaneously involve either utilizing both WiFi and LiFi network interfaces, or utilizing MIMO chips and requiring a combiner at a higher layer, i.e., the TCP / IP layer, to send signals over both RF and LiFi signal paths. Such solutions handle communication between the two devices using MIMO technology and a mix of RF and optical frequencies.

[0008] In another conventional solution, the LiFi module is designed as an integral part of the WiFi chip, and the signal needed to make the selection between the WiFi network and the LiFi network comes from the MAC layer. This signal is from the digital domain and is based on the Received Signal Strength Indicator (RSSI) calculated in the WiFi chip. To utilize this MAC signal, an additional connection between the Optical Front End (OFE) and the WiFi chip is needed.

[0009] According to another known system, an Access Point (AP) can connect both WiFi and LiFi, as well as user terminal devices. In this case, the handover between LiFi and WiFi networks occurs within the same network, and there is no roaming or handover from one LiFi AP to another WiFi AP or vice versa. This handover is sometimes called Intra-AP handover, since it only involves a physical (PHY) layer handover.

[0010] Recent developments have proposed 802.11 WiFi-based LiFi systems, which allow the possibility of combining LiFi with existing WiFi networks. The advantages of using WiFi chips for LiFi communication include extensive WiFi network management and security protocols and resource reuse.

[0011] For convenience, a well-designed WiFi-based LiFi system allows the LiFi front-end to remain transparent to higher-layer WiFi protocols so that existing mechanisms such as fast roaming can also be reused. In this way, the LiFi network becomes an integral part of the wireless access network, e.g., in a building, together with the existing WiFi network.

[0012] US2020 / 195342A1 discloses a WLAN Li-Fi transceiver including a Wi-Fi device and an analog front end. Paragraphs 101 and 102 disclose that a MAC controller 420 configures the WLAN transceiver to communicate via Wi-Fi instead of via Li-Fi if the Li-Fi signal quality is unacceptable. The MAC controller 420 generates a selection signal 424 to disconnect between the Wi-Fi RF module 408 and the RF / Li-Fi converter 412 and to connect between the Wi-Fi RF module 408 and the Wi-Fi antenna interface 416.

[0013] "Handover in hybrid LiFi and WiFi networks" by SANUSI JAAFARU et al. (2019-12-10) provides an overview concept of hybrid handover in LiFi / WiFi networks. It discloses the concept of soft handover, where various QoS parameters including RSSI are considered in hybrid handover.

[0014] ASHIMBAYEVA AIGERIM et al.'s "Hard and soft switching for indoor hybrid VLC / RF systems" (2017-09-20) is dedicated to the analysis of hard switching (HS) and soft switching (SS) methods for hybrid VLC / RF systems. It demonstrates that SS outperforms HS when power is optimally shared between the VLC and RF links.

[0015] 1 shows a schematic diagram of a communication system 10 deployed with both LiFi and WiFi networks. The communication system 10 may be a local area network (LAN) including a LAN switch 11, a WiFi access point (AP) 12, and two LiFi APs 13 and 14 connected to the LAN switch 11. The LiFi APs 13 and 14 have coverage areas 15 and 16, respectively, indicated by solid triangles, and the WiFi AP has coverage area 17 indicated by dashed triangles.

[0016] As can be seen from Fig. 1, the LiFi APs have relatively small coverage areas 15 and 16, and therefore there may be blind spots between the coverage areas of the two LiFi APs. In contrast, WiFi signals, which are prevalent in commercial buildings, may achieve wider coverage 17, but the throughput of WiFi may be significantly slower than LiFi due to interference.

[0017] Due to the above facts, a user device operating in a network environment as shown in FIG. 1 may need to handover between a WiFi network and a LiFi network from time to time. In an office environment, a user may need to move from one room to another during an online meeting. For a LiFi network, when a user enters or passes through a blind area, the connection link may be temporarily lost. It may take several seconds to disconnect from a LiFi AP and connect to a WiFi AP, which will result in a bad user experience. Summary of the Invention [Problem to be solved by the invention]

[0018] Therefore, there is a real need for a seamless handover method between LiFi and WiFi networks to enhance user experience in WiFi-based LiFi networks. [Means for solving the problem]

[0019] In a first aspect of the present disclosure, there is provided a LiFi module for operatively connecting to a WiFi communication module supporting both Wi-Fi and Li-Fi connections, the LiFi module including an optical front-end (OFE) for transmitting and receiving data over an optical medium, and a connection circuit for communicatively connecting the OFE to the WiFi communication module, the connection circuit comprising: a switching element electrically connected to the LiFi signal strength detector and configured to enable or disable a connection between the OFE and the WiFi communication module under control of the LiFi signal strength detector; a LiFi signal strength detector electrically connected to the switching element and the receive path of the OFE and configured to detect a strength of an optical signal received at the receive path of the OFE and to control the switching element based on the detected strength of the optical signal; A LiFi module is presented, including:

[0020] The present disclosure is based on the insight that by utilizing a LiFi module operating in conjunction with a WiFi communication module supporting dual antenna connectivity, a seamless transition between LiFi and WiFi networks can be achieved by using only one wireless link for data communication.

[0021] The connection circuit of the LiFi module for connecting the LiFi module to the WiFi communication module includes a switching element that operates under the control of a LiFi signal strength detector, or simply a signal strength detector, and enables or disables the connection between the OFE of the LiFi module and the WiFi communication module based on the strength of the optical signal detected by the LiFi signal strength detector. This provides a seamless handover between the LiFi network and the WiFi network depending on the availability of the LiFi network as indicated by the strength of the optical signal detected by the LiFi signal strength detector of the LiFi module.

[0022] Compared with the prior art which relies on enabling WiFi and LiFi connections simultaneously for data communication and therefore requires complex protocols at the TCP / IP layer to combine RF and optical data paths and two baseband chips, the LiFi module of the present disclosure remains simple in terms of circuit design and does not require any modification of the existing TCP / IP protocol.

[0023] Compared to the prior art, where the signal required to make the selection between WiFi and LiFi networks comes from the MAC layer and therefore requires an extra connection between the OFE and the WiFi chip, the optical signal used in this disclosure is an analog signal that is generated locally inside the OFE. As a result, the LiFi module communication remains completely independent of the WiFi module, which makes the LiFi module "universal", i.e., the LiFi module can work with standard off-the-shelf WiFi communication modules that support dual antenna connections without extra connectors.

[0024] In one example of the present disclosure, the switching element includes a first switch and a second switch, a control terminal of the first switch is connected to a first output terminal of the LiFi signal strength detector, and a control terminal of the second switch is connected to a second output terminal of the LiFi signal strength detector.

[0025] A LiFi signal strength detector for detecting the optical signal outputs two control signals to separately control two switches that operate to ensure a smooth transition in a so-called "make before break" manner, meaning that the connection with one network is established before the connection with the other network is broken, thus preventing connection interruptions.

[0026] In one example of the present disclosure, the signal strength detector is configured to output an enabling signal at its second output terminal when a detected strength of the optical signal is lower than a threshold value, and output a disabling signal at its first output terminal after a delay period, the first switch is configured to disable a connection between the OFE and the WiFi communication module in response to the disabling signal received at its control terminal from the first output terminal of the LiFi signal strength detector, and the second switch is configured to enable a connection between the WiFi communication module and a radio frequency (RF) antenna in response to the enabling signal received at its control terminal from the second output terminal of the LiFi signal strength detector.

[0027] When the detected strength of the optical signal is lower than a threshold, indicating that the user is near the edge of the LiFi coverage, the RF antenna of the WiFi network is enabled by the second switch. In this way, the WiFi communication module can prepare to connect to the WiFi network, for example, through a WiFi access point (AP) within the coverage area of ​​the RF antenna, and prepare for fast roaming.

[0028] In effect, the first switch operates to disable the connection between the OFE and the WiFi communication module after a slight delay, thereby allowing a certain amount of "overlap" time between the WiFi and LiFi networks, ensuring that the WiFi network connects before the LiFi network disconnects in a "make and break" manner, thereby allowing a smooth transition from the LiFi network to the WiFi network.

[0029] Furthermore, when the connection between the OFE and the WiFi communication module is disabled, the first switch may be further configured to enable a connection between the WiFi communication module and the further RF antenna.

[0030] Therefore, a WiFi communication module may be connected to two antennas, operating at the same or different frequencies, thus allowing more communication resources.

[0031] A person skilled in the art may contemplate that it is also possible to connect the WiFi communication module to a load such as a 50 Ohm terminator to disable the connection to the WiFi communication module controlled by the first switch.

[0032] In one example of the present disclosure, the LiFi signal strength detector is configured to output an enabling signal at its first output terminal and output a disabling signal at its second output signal after a delay period when a detected strength of the optical signal is higher than a threshold, the first switch is configured to enable a connection between the OFE and the WiFi communication module in response to the enabling signal received at its control terminal from the first output terminal of the LiFi signal strength detector, and the second switch is configured to disable a connection between the WiFi communication module and the RF antenna and enable a connection between the WiFi communication module and the 50 ohm terminator in response to the disabling signal received at its control terminal from the second output terminal of the LiFi signal strength detector.

[0033] This concerns a scenario of handover from a WiFi network to a LiFi network. When a user enters a LiFi coverage area, the detected strength of the optical signal is higher than a threshold. Therefore, the signal strength detector outputs a control signal to a first switch to enable the connection between the OFE and the WiFi communication module. The second switch is also controlled by the signal strength detector to disconnect the RF antenna from the WiFi communication module after a delay.

[0034] This enables smooth handover and seamless connectivity between LiFi and WiFi networks through the LiFi module working together with the WiFi communication module supporting both WiFi and LiFi connections.

[0035] In a further example of the present disclosure, the first switch and the second switch are single pole double throw switches.

[0036] These readily available switches can be conveniently used to implement the connection circuits of LiFi modules, keeping the cost of the LiFi modules low and the implementation simple.

[0037] In one example of the present disclosure, the LiFi module further includes an RF-to-LiFi converter connected between the OFE and the first switch of the connectivity module and configured to perform frequency conversion between an RF band and a LiFi optical baseband.

[0038] The RF-LiFi converter upconverts or downconverts, for example, 2.4G or 5GHz RF signals at the connection port of the WiFi communication module to optical baseband frequencies, which are then interfaced with the OFE.

[0039] In one example of the present disclosure, a third switch is connected between the RF-LiFi converter and the first switch of the connection module and configured to separate the transmission signal and the reception signal from the WiFi communication module.

[0040] Because the OFE communication module operates in full-duplex and the WiFi communication module operates in half-duplex, the third switch works together with the RF detector to separate the TX and RX signals from the WiFi communication module by detecting the RF signal in the TX path.

[0041] A second aspect of the present disclosure provides a wireless communication module for providing network services to both a WiFi network and a LiFi network connected to the same LAN, the wireless communication module including a LiFi module according to the first aspect of the present disclosure and a WiFi communication module operatively connected to the LiFi module and supporting both the WiFi connection and the LiFi connection. The WiFi communication module includes a first connection port and a second port, and under the control of a LiFi signal strength detector of the LiFi module, the first connection port is switched between an RF antenna and a terminator, and the second connection port is switched between an OFE of the LiFi module and a second RF antenna or terminator.

[0042] The LiFi module of the present disclosure may be used in a user device. In addition to including a LiFi module according to the first aspect of the present disclosure, the user device further includes a WiFi communication module that supports both WiFi and LiFi connections and is operably connected to the LiFi module, and the connection between the OFE of the LiFi module and the WiFi communication module is enabled or disabled under the control of a signal strength detector of the LiFi module.

[0043] Such user devices will be able to seamlessly handover between WiFi and LiFi networks, thereby enhancing the user experience in terms of network connectivity.

[0044] A third aspect of the present disclosure is a method of initiating a handover of a user device between a WiFi network and a LiFi network, both of which are connectable to a user device and both of which are connected to the same local area network (LAN), the user device including a LiFi module according to the first aspect of the present disclosure, the user device further including a WiFi communication module supporting a WiFi connection and a LiFi connection at two connection ports, respectively, the method being performed by a control software routine of the WiFi communication module of the user device; detecting a state change at one of the connection ports of the WiFi communication module; initiating a handover between the WiFi network and the LiFi network using a fast roaming procedure; The present invention provides a method comprising:

[0045] When initiating a handover between a WiFi communication network and a LiFi communication network, for example using fast roaming, it is very important for the WiFi module to know when a switching action between the two networks should be performed. The LiFi module according to the first aspect of the present disclosure, when operating with the WiFi communication module, under the control of the signal strength detector of the LiFi module, provides an indication to the WiFi communication module when a state change occurs in one of the connection ports.

[0046] When the WiFi module detects that a state change has occurred, it will realize that it is time to begin or initiate a handover procedure. Since fast roaming is accomplished in a very short time, typically around 40 milliseconds, the user device will successfully connect to the new network before losing connection with the current network, thereby achieving a seamless handover between networks.

[0047] In one example of the present disclosure, the user device is connected to a LiFi network, the detecting step includes detecting a WiFi beacon message being received at a second connection port of the WiFi communication module, and the initiating step includes initiating a handover from the LiFi network to the WiFi network.

[0048] When the user device is accessing a LiFi network, the WiFi module may receive a WiFi beacon message as a result of the user device losing connection with the LiFi network, for example due to the user device being at the edge of the LiFi network, at which point a handover from the LiFi network to the WiFi network is initiated.

[0049] Specifically, in one example of the present disclosure, the WiFi beacon message is received at the second connection port of the WiFi communication module as a result of a connection between the second connection port of the WiFi communication module and the RF antenna being enabled in response to an enabling signal received at the control terminal of the second switch from the second output terminal of the signal strength detector of the LiFi module.

[0050] If the user device is about to lose connection with the LiFi network, the signal strength detector notices the situation and controls the second switch to enable a connection between the second port of the WiFi communication module and the RF antenna, thereby allowing the WiFi communication module to receive WiFi beacon messages.

[0051] Except for the two connection ports, no direct communication is required between the LiFi module and the WiFi communication module.

[0052] In one example of the present disclosure, the user device is connected to a WiFi network, the detecting step includes detecting a LiFi beacon message being received at a first connection port of the WiFi communication module, and the initiating step includes initiating a handover from the WiFi network to the LiFi network.

[0053] This relates to the scenario where a user is accessing a WiFi network and moves into the coverage area of ​​the LiFi network, which means that the WiFi communication module should now initiate a handover from the WiFi network to the LiFi network.

[0054] In one example of the present disclosure, a LiFi beacon message is received at a first connection port of the WiFi communication module as a result of a connection between the first connection port of the WiFi communication module and the OFE being enabled in response to an enabling signal received at a control terminal of a first switch from a first output terminal of a signal strength detector of the LiFi module.

[0055] Again, a state change can be triggered by the signal strength detector in the LiFi module to initiate fast roaming at the appropriate time.

[0056] In one embodiment of the present disclosure, an indicator is included in WiFi beacon messages and LiFi messages to distinguish between WiFi networks and LiFi networks.

[0057] The indicator may be a special code to identify the LiFi AP that is inserted into the appropriate field of the beacon message, allowing the user device to determine which network is reachable.

[0058] In a fourth aspect of the present disclosure, there is provided a computer program product comprising a computer-readable storage medium storing instructions that, when executed on at least one processor, cause the at least one processor to perform a method according to the third aspect of the present disclosure.

[0059] The above and other features and advantages of the present disclosure will be best understood from the following description taken in conjunction with the accompanying drawings, in which like reference numerals indicate identical parts or parts performing the same or equivalent functions or operations, and in which: [Brief description of the drawings]

[0060] [Figure 1] 1 illustrates a schematic diagram of a communication system deployed using both LiFi and WiFi networks. [Diagram 2] 1 illustrates a schematic block diagram of a LiFi module according to the present disclosure. [Diagram 3] FIG. 1 is a schematic timing diagram illustrating the control of a switch to enable or disable a LiFi or WiFi network based on the detected strength of the optical signal. [Figure 4] 1 illustrates a schematic diagram of an 802.11 beacon frame. [Diagram 5] 1 illustrates, in a flow chart type diagram, a method for initiating a handover of a user device including a LiFi module of the present disclosure between a WiFi network and a LiFi network. [Figure 6] 6 illustrates a schematic diagram of a complete operational procedure utilizing the method of FIG. 5 by a user device or an EP. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] The embodiments contemplated by the present disclosure will now be described in more detail with reference to the accompanying drawings. The disclosed subject matter should not be construed as being limited to only the embodiments described herein. Rather, the illustrated embodiments are provided as examples to convey the scope of the subject matter to those skilled in the art.

[0062] In the following description, the terms "handover," "handoff," and "roaming" are used interchangeably, and the terms "user device" and "EP" are also used interchangeably.

[0063] Seamless handoff between WiFi network and LiFi network is realized by using the LiFi module proposed by this disclosure. The application scenario of the LiFi module may be a user device, such as a laptop or a mobile phone, which may be called an Endpoint (EP), deployed in a Local Area Network (LAN).

[0064] The LAN may be an Extended Basic Service Set (Extended BSS) that includes multiple BSSs including LiFi APs and WiFi APs. The LiFi AP and WiFi AP are independent of each other and both connect to the same LAN. The LiFi AP may also be a module that is removably connected to the WiFi AP, and the two APs function independently of each other. In other words, the LiFi AP and WiFi AP may be physically packaged together, even on the same PCB, but logically are two separate APs connected to the same LAN.

[0065] Both LiFi and WiFi APs implement IEEE 802.11r, an amendment to the IEEE 802.11 standard that allows continuous connectivity for wireless devices while moving, with fast and secure client transitions nearly seamlessly from one BSS or AP to another. Switching or transition from one AP to another is also known as handoff or roaming.

[0066] 802.11r introduces a new concept of roaming called Fast Transition (FT), where an initial handshake with the new AP is performed before the client, i.e., EP or user device, roams to the target AP. The initial handshake allows the client and AP to calculate Pairwise Transient Keys (PTKs) in advance. These PTKs are applied to the client and AP after the client does a reassociation request or response exchange with the new target AP.

[0067] FT according to 802.11r may be referred to as a "Make Before Break" procedure. Specifically, an FT originator, which may be an EP or a user device, determines that it needs to transition to a new or target AP while still connected to a current AP. The FT originator then exchanges Authentication-Request and Authentication-Response messages with the target AP before exchanging Reassociation Request and Reassociation Response messages with the target AP. A successful reassociation occurs only if the time between the Authentication Request and the Reassociation Request does not exceed the Reassociation Deadline Time.

[0068] Therefore, it is very important for the WiFi chip in the EP that performs the transition or switching action from one AP to another to know the moment to initiate the switch to another network.

[0069] The LiFi module proposed by this disclosure works together with a dual-antenna WiFi communication module to achieve smooth and seamless handoff between LiFi and WiFi networks.

[0070] 2 shows a schematic block diagram of a LiFi module 20 according to the present disclosure. The LiFi module 20, sometimes referred to as an analog front end, is suitable for operation with an existing WiFi communication module 200 that supports both WiFi and LiFi connections.

[0071] The WiFi communication module 200 may be configured in a popular M.2 module form factor, which allows easy connection to a motherboard of a user device, for example, via a PCIe interface. The WiFi communication module 200 has two connection ports 201 and 202, which means that the WiFi communication module 200 supports dual antennas. The WiFi chip 205 of the WiFi communication module 200 is configured to cooperate with the operation of the LiFi module 20 to perform high-speed roaming between the WiFi network and the LiFi network.

[0072] The LiFi module 20 includes an optical front-end (OFE) 21 that includes a transmit path 22 and a receive path 23 that are arranged to transmit and receive data, respectively, over an optical medium, such as the visible, ultraviolet, and infrared spectrums.

[0073] The transmit path 22 of the OFE 21 includes a driver and a light transmitting device, which may be, for example, a vertical-cavity surface-emitting laser (VCSEL) or a light emitting diode (LED). The receive path 23 of the OFE 21 includes a light receiving device, such as a photodiode, and a transimpedance amplifier (TIA).

[0074] The LiFi module 20 further includes a connection circuit for communicatively connecting the OFE 21 to one of the connection ports of the WiFi communication module 200. In the example as shown in FIG. 2, the connection 26 between the OFE 21 of the LiFi module 20 and the connection port 201 of the WiFi communication module 200 via the connection circuit may be enabled or disabled.

[0075] The connection circuit includes a switching element 24 and a LiFi signal strength detector, or simply a signal strength detector 25. The switching element 24 is electrically connected to the signal strength detector 25 and is configured to enable or disable a communication connection, a connection 26, between the OFE 21 and the WiFi communication module 200 under the control of the signal strength detector 25.

[0076] A signal strength detector 25 is electrically connected to the switching element 24 and to the receive path 23 of the OFE 21 and is configured to detect the strength of the optical signal received at the receive path 23 of the OFE and to control the switching element 24 based on the detected strength of the optical signal.

[0077] The switching element 24 includes a first switch S1 and a second switch S2 that are respectively controlled by a first control signal K1 and a second control signal K2 output by the signal strength detector 25. That is, a control terminal of the first switch S1 is connected to a first output terminal of the signal strength detector 25, and a control terminal of the second switch S2 is connected to a second output terminal of the signal strength detector 25.

[0078] The two switches S1 and S2 may be, for example, single-pole double-throw (SPDT) switches operating together to control the routing of communication signals from the WiFi communication module 200 to the OFE 21 of the LiFi module 20 or to the RF antenna 203, and optionally to a further RF antenna 204, depending on the detected optical signal strength.

[0079] Specifically, the first switch S1 is controlled by a first control signal K1 to switch the first connection port 201 of the WiFi communication module 200 between position 1 connected to the OFE 21 and position 0 connected to the further RF antenna 204. It can be understood that the output terminal of S1 in position 0 connected to the RF antenna 204 may be terminated with a 50 ohm load (not shown). In this case, the WiFi communication module 200 operates in only one RF band via the RF antenna 203.

[0080] The second switch S2 is controlled by a second control signal K2 to switch the second connection port 202 of the WiFi communication module 200 between position 1 connected to the RF antenna 203 and position 0 terminated with a 50 ohm load R1.

[0081] Due to the signal at the connection port of the WiFi communication module 200 being a radio frequency signal, the LiFi module 20 further includes an RF mixer for down / up converting the RF signal transmitted through the connection port 201 of the WiFi communication module 200 and then interfacing with the OFE 21 of the LiFi module 20.

[0082] Since the OFE 21 is a full-duplex module while the WiFi communication module 200 operates in half-duplex, the LiFi module 20 further includes an RF detector 28 and a third switch S3, which together function to separate the TX and RX signals from the WiFi communication module 200 by detecting the RF signal in the TX path.

[0083] The operation of the LiFi module 20 is described in detail below.

[0084] The signal strength detector 25 measures the strength of the optical signal received via the receive path 23 of the LiFi module 20, which indicates whether the user device including the LiFi module 20 is within a LiFi coverage area.

[0085] Depending on the comparison of the measured strength of the received optical signal with a predetermined threshold, the signal strength detector 25 outputs two control signals K1 and K2 for separately controlling the first switch S1 and the second switch S2, respectively.

[0086] As an example, the signal strength detector 25 may output a control signal having a high level "1" at one of its output terminals and a further control signal "0" at its other output terminal if the measured strength of the received optical signal is higher than a threshold value. When the control signal is high "1", the controlled switch is connected to position 1 and when the control signal is low "0", the switch is connected to position 2.

[0087] Those skilled in the art may contemplate that the above examples are not intended to limit the implementation aspects of the present disclosure, and in fact, other controller manners may be defined.

[0088] In a steady-state operation mode of a user device including the LiFi and WiFi communication modules 20 and 200, either the RF connection or the optical connection is active and the other medium is disabled, allowing the WiFi chip processor 205 in the WiFi communication module 200 to detect state transitions or state changes that can be used by the user device to initiate high-speed roaming.

[0089] A user device is connected to a LAN that includes a LiFi AP and a WiFi AP, both of which are connected to the same LAN.

[0090] Assume that currently, the first switch S1 is in position 1 and the switch S2 is in position 0, i.e., the connection between the WiFi communication module 200 and the OFE 21 of the LiFi module 20 is enabled. At this point, the user device is connected to the LAN via the LiFi AP. If the user device moves towards the edge of the LiFi coverage area, the strength of the optical LiFi signal detected by the signal strength detector 25 starts to decrease and falls below the threshold.

[0091] In this case, the second switch S2 is controlled by a control signal K2 received at an input terminal of the second switch S2 from the signal strength detector 25 to switch to position 1, which enables a connection between the RF antenna 203 and the WiFi communication module 200 via the connection port 202. In this way, the WiFi communication module 200 can establish contact with a WiFi AP in the coverage area of ​​the RF antenna 203 and prepare for fast roaming.

[0092] At the same time, the user device is still associated with the LiFi AP by a signal path through the first switch S1 via the connection port 201. The WiFi chip 205 initiates, for example, an 802.11 fast roaming procedure as soon as it notices that the WiFi AP is accessible.

[0093] From this point onwards, the control signal K1 is set to level "0" after a predefined amount of "overlap" time or when the detected LiFi signal becomes approximately zero. Therefore, the first switch S1 is controlled by K1 to switch to position 0. From that time onwards, the connection between the WiFi communication module 200 and the OFE 21 is broken and the user device operates in WiFi mode.

[0094] In practice, the “overlap” time or delay between switching the second switch S2 to position 1 and switching the first switch S1 to position 0 may be set to a predetermined time, such as 100 ms, that is sufficient for the fast roaming procedure to be completed.

[0095] Alternatively, the control signal K1 may be triggered by a further even lower threshold value of the strength of the optical LiFi signal detected by the signal strength detector 25. The same is true for the switching procedure from the WiFi network to the LiFi network.

[0096] If switch S1 position 0 is connected to the further antenna 204, the WiFi chip 205 operates with dual antennas. It is also possible to connect S1 position 0 with a 50 ohm terminator and operate the WiFi chip with only one antenna.

[0097] On the other hand, when the user device enters a LiFi coverage area while still connected to a WiFi network, the connection between the OFE of the LiFi connectivity module 20 and the WiFi communication module 200 is enabled before disconnecting the RF antenna(s).

[0098] Specifically, the strength of the optical LiFi signal detected by the signal strength detector 25 exceeds a threshold. Therefore, the signal strength detector 25 outputs a control signal K1 “1” to switch the switch S1 to position 1. Therefore, the connection port 201 of the WiFi communication module 200 is connected to the OFE 21 while the connection port 202 of the WiFi communication module 200 remains connected to the RF antenna 203.

[0099] While the WiFi chip 205 maintains association with the WiFi AP, a fast roaming procedure is initiated to begin association with the LiFi AP.

[0100] When the user device is associated with the LiFi AP, the second switch S2 is controlled by the signal strength detector 25 to switch to position 0, which connects the connection port 202 to a 50 ohm terminator, i.e., the reception of WiFi signals is completely disabled. This serves the purpose of allowing the WiFi chip 205 to detect the WiFi / LiFi operation mode state transition without extra signal connection between the LiFi and WiFi communication modules.

[0101] Since a user device is associated with only one AP at any time, the LiFi module 20 proposed by the present disclosure can achieve smooth handover between LiFi and WiFi networks, thereby achieving seamless connectivity.

[0102] FIG. 3 is a schematic timing diagram 30 illustrating the control of switches S1 and S2 using control signals K1 and K2 to enable or disable the LiFi or WiFi network based on the detected strength of the optical signal.

[0103] Curve 31 represents the strength of the optical signal detected by signal strength detector 25. At time point A, the strength of the detected optical signal falls below threshold 39. The control signal K2 at this point 32 enables switch S2 to connect the RF antenna to the WiFi communication module, triggering the initiation of a fast roaming procedure for roaming to the WiFi network.

[0104] At time 33, the user device is connected to the WiFi network. Then, at time 34, the control signal K1 controls the switch S1 to disconnect the OFE from the WiFi communication module. As mentioned above, the time period between 32 and 34 may be set to a predetermined value. Alternatively, the time 34 may be determined by a further threshold 310 that is lower than the first threshold 39.

[0105] Meanwhile, at time B, the strength of the optical signal detected by the signal strength detector 25 exceeds the threshold 39. At this point 36, the control signal K1 enables the switch S1 to connect the OFE to the WiFi communication module, triggering the initiation of a fast roaming procedure for roaming into the LiFi network.

[0106] At time 37, the user device is connected to the LiFi AP. Then, at time 38, the control signal K2 controls the switch S2 to disconnect the RF antenna from the WiFi communication module and connect the connection port 202 to the 50 ohm terminator. Again, the delay period between 36 and 38 may be set to have a predetermined length. Alternatively, the time 38 may be determined based on a further threshold (not shown) that is higher than the first threshold 39.

[0107] A method for initiating a handover of a user device including a LiFi module of the present disclosure between a WiFi network and a LiFi network is detailed below.

[0108] IEEE 802.11r provides two roaming methods, namely Over-the-Air and Over-the-DS (Distribution System). For completeness, the Over-the-Air message exchange procedure that complies with IEEE, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications”, IEEE, 2016 is briefly described below. In all fast roaming processes, the FT Originator (FTO) is the client.

[0109] Initially, the FTO is connected to the current AP with a secure session and is performing data transmission when it determines it needs to migrate to the target AP. Then, the FTO sends an 802.11 authentication request to the target AP and receives an authentication response from the target AP. Then, a reassociation request can be sent from the FTO to the target AP, followed by a reassociation response from the target AP to the FTO. Successful reassociation occurs only if the time between the authentication request and the reassociation request does not exceed the reassociation deadline time. If the reassociation is successful, the 802.1X controlled port is unblocked and a (secure) session and data transmission can be performed successfully.

[0110] For successful fast roaming, the WiFi chip in the user device keeps a record of neighboring APs and knows the trigger for transition when both WiFi and LiFi APs become visible, after which the user device immediately decides to handover to the new AP.

[0111] To distinguish between WiFi APs and LiFi APs, during the installation phase, LiFi APs are given a special code in their beacon frames so that user devices can always distinguish between WiFi APs and LiFi APs. With this information, user devices know the exact moment when they need to trigger a fast roaming procedure.

[0112] The special code for identifying the LiFi AP can be implemented, for example, in the Vender Specific field in the 802.11 beacon frame as shown in Figure 4, or any other convenient field of the beacon frame. In this way, the user device will know whether the AP is a WiFi AP or a LiFi AP after decoding the beacon frame.

[0113] FIG. 5 illustrates generally in a flow chart type diagram a method 50 for initiating a handover of a user device including a LiFi module of the present disclosure between a WiFi network and a LiFi network.

[0114] Except for the two connection ports of the WiFi communication module, there is no direct communication between the LiFi module and the WiFi chip of this disclosure.

[0115] Method 50 enables the WiFi chip to know when a switching action, i.e., a transition of K1, K2, shown as "A" and "B" in FIG. 3, occurs and thereby initiate fast roaming at the appropriate time.

[0116] In step 51, the WiFi chip detects a state change in one of the connection ports of the WiFi communication module.

[0117] This may include the WiFi chip detecting that an RF antenna is connected to connection port 202 of the WiFi communication module, or that an OFE is connected to connection port 201 of the WiFi communication module.

[0118] In one example, a user device performs a network scan in a traditional manner to learn if there is an AP within its range. If the user device can "see" a LiFi AP, i.e., the user device can be connected or attached to the LiFi AP, the user device will connect to the LiFi AP.

[0119] In this operating state, the RF antenna will be disabled under the control of the LiFi signal strength detector by control signals K1 and K2, and therefore the WiFi chip will not be able to see the WiFi AP, although it may still be physically within the WiFi coverage area.

[0120] When the user device approaches the edge of the LiFi coverage area, the LiFi signal detector enables the connection of the RF antenna to the connection port 202. At this point, the WiFi chip realizes that a WiFi AP is within its communication range because a WiFi beacon message is received at the connection port 202 of the WiFi communication module.

[0121] This state change allows the WiFi chip to see both LiFi and WiFi AP simultaneously since there is still active data communication between the connection port and the OFE. The state change is a direct result of the LiFi signal strength detector's action (changing K2 from "0" to "1"). This state change will be used by the WiFi chip as a trigger to initiate a fast roaming procedure and handover to the WiFi network in the next step.

[0122] In step 52, the WiFi chip initiates a handover from the LiFi network to the WiFi network using a fast roaming procedure.

[0123] The fast roaming procedure is very fast, typically completing in about 40 ms, and it is expected that the user device will already be associated with a WiFi AP before the LiFi signal is lost entirely.

[0124] In another example, a user enters a LiFi zone while still associated with a WiFi AP. At this point, the LiFi signal detector changes the control signal K1 to "1" at time "B" (see FIG. 3). This allows the WiFi chip to notice or detect (step 51) a state change since it can see both the WiFi and the LiFi AP. This state change is used as a trigger to handover to the LiFi network via a fast roaming procedure.

[0125] The WiFi chip then initiates a handover from the WiFi network to the LiFi network using a fast roaming procedure (step 52).

[0126] This procedure is less time-critical than LiFi-WiFi handover since WiFi signals remain available in the LiFi zone and therefore the transition can be done slowly, if necessary.

[0127] Additionally, signal K1 may be utilized to turn off the OFE TX circuitry to save power when the user device is outside of LiFi coverage.

[0128] To avoid frequent transitions or false detections by the LiFi signal strength detector, a signal quality assessment circuit ensures that it switches to the optical medium only if the signal received by the OFE is of sufficient connection quality, e.g., above a defined signal-to-noise ratio (SNR) or RSSI threshold.

[0129] This can be achieved in combination with well-considered thresholds, and possibly hysteresis, as shown in Figure 3, to avoid frequent switching between LiFi-WiFi when the user device is stationary near the edge of LiFi coverage. The hysteresis can be implemented with two different thresholds (not shown in Figure 3), e.g., a higher threshold for time point A than time point B (instead of using the same threshold).

[0130] In a real-life application scenario, a user device that resides in a LAN with both WiFi and LiFi networks is assumed to be connected to the WiFi network by default at startup. Since there is no direct communication between the LiFi module and the WiFi chip in the user device, except for the two antenna ports of the WiFi chip, the above method is used to make the WiFi chip start roaming as soon as the LiFi signal strength detection changes state (in or out of coverage area).

[0131] FIG. 6 shows a schematic diagram of a complete operational procedure 60 for utilizing the above method by a user device or EP.

[0132] After starting up in step 601, such as by powering up the user device, the user device connects with a WiFi AP in step 602. While still connected to the WiFi AP, the EP performs a network scan in step 603, which is typically implemented in WiFi devices to know which APs are within range.

[0133] Once the user device sees a LiFi AP within reach in step 604, it initiates a fast roaming procedure in step 605 and connects to the LiFi AP in step 606.

[0134] When this happens, the RF antenna 203 will be disabled by the LiFi signal strength detector circuit (K1, K2). In this operating state, with both RF antennas disconnected, the WiFi chip will no longer be able to see the WiFi AP, even though it is still physically within WiFi coverage.

[0135] When connected to a LiFi AP, if the user moves near the edge of LiFi coverage, the LiFi signal detector enables the RF antenna 203 (K2 goes high "1" at time 32, see FIG. 3). When the EP scans for networks (607), its WiFi chip will notice that there is a reachable WiFi AP at 608. At this point, WiFi beacons are received over port 202 while active data communication is still taking place over port 201 connected to the OFE.

[0136] This state change is used as a trigger to initiate a fast roaming procedure (609) and handover to the WiFi network (602). This state change is a direct result of the action of the LiFi signal strength detector (changing K2 from "0" to "1"), where both LiFi and WiFi APs are visible.

[0137] In another scenario, if the user device enters a LiFi zone while still associated with a WiFi network, the WiFi chip will notice the state change since it can see both the WiFi and the LiFi AP, because the LiFi signal detector will change K1 to "1" at time 36 (see Figure 3).

[0138] This state change is used as a trigger to handover to the LiFi network via a fast roaming procedure, which is less time-critical than a LiFi-WiFi handover since WiFi signals remain available in the LiFi zone and thus the transition can be done slowly, if necessary.

[0139] The present disclosure is not limited to the examples disclosed above, but can be modified and extended by those skilled in the art beyond the scope of the present disclosure disclosed in the appended claims, without the need to apply inventive skills, for use in any data communication, data exchange and data processing environment, system or network.

Claims

1. 1. A Li-Fi module for operatively connecting to a WiFi communication module supporting both Wi-Fi and Li-Fi connections, the Li-Fi module including an optical front end (OFE) for transmitting and receiving data over an optical medium, and connection circuitry for communicatively connecting the OFE to the WiFi communication module, the connection circuitry comprising: a switching element including a first switch configured to enable or disable a connection between the OFE and the WiFi communication module, and a second switch configured to enable or disable a connection between the WiFi communication module and a radio frequency (RF) antenna; a LiFi signal strength detector electrically connected to the switching element and a receive path of the OFE and configured to control the switching element based on a detected strength of an optical signal received at the receive path of the OFE; Including, A LiFi module, wherein a control terminal of the first switch is connected to a first output terminal of the LiFi signal strength detector, and a control terminal of the second switch is connected to a second output terminal of the LiFi signal strength detector.

2. the LiFi signal strength detector is configured to output an enabling signal at a second output terminal and, after a delay period, a disabling signal at a first output terminal when a detected strength of the optical signal is lower than a threshold; the first switch is configured to disable a connection between the OFE and the WiFi communication module in response to receiving the disabling signal; The WiFi module of claim 1 , wherein the second switch is configured to enable a connection between the WiFi communication module and an RF antenna in response to receiving the enabling signal.

3. the LiFi signal strength detector is configured to output an enabling signal at a first output terminal and, after a delay period, a disabling signal at a second output terminal when a detected strength of the optical signal is greater than a threshold; the first switch is configured to enable a connection between the OFE and the WiFi communication module in response to receiving the enabling signal; 2. The WiFi module of claim 1, wherein the second switch is configured to disable a connection between the WiFi communication module and an RF antenna and enable a connection between the WiFi communication module and a terminator in response to receiving the disabling signal.

4. The LiFi module of claim 1 or 2, wherein the first switch and the second switch are single-pole double-throw switches.

5. The LiFi module of claim 1 or 2, further comprising an RF-LiFi converter connected between the OFE and the first switch of the connection module and configured to perform frequency conversion between an RF band and a LiFi optical baseband.

6. The LiFi module of claim 5, further comprising a third switch connected between the RF-LiFi converter and the first switch of the connection module and configured to separate the transmit and receive signals from the WiFi communication module.

7. 4. A wireless communication module for providing network services to both a WiFi network and an WiFi network connected to the same LAN, the wireless communication module comprising: an WiFi module according to any one of claims 1 to 3; and a WiFi communication module operably connected to the WiFi module and supporting both WiFi and WiFi connections, the WiFi communication module comprising a first connection port and a second connection port, and under the control of an WiFi signal strength detector of the WiFi module, the second connection port is switched between an RF antenna and a terminator, and the first connection port is switched between an OFE of the WiFi module and a second RF antenna or terminator.

8. 4. A method for initiating handover of a user device between a WiFi network and a WiFi network, both of which are connectable to a user device and both of which are connected to the same local area network, the user device including the WiFi module of any one of claims 1 to 3, the user device further including a WiFi communication module supporting WiFi and WiFi connections on two connection ports, respectively, the method being performed by a control software routine of the WiFi communication module of the user device; detecting a state change at one of the connection ports of the WiFi communication module; initiating a handover between the WiFi network and the WiFi network using a roaming procedure; A method comprising:

9. the user device is connected to the WiFi network; the detecting step includes detecting a WiFi beacon message being received at a second connection port of the WiFi communication module; the initiating step includes initiating a handover from the WiFi network to the WiFi network. The method of claim 8.

10. 10. The method of claim 9, wherein the WiFi beacon message is received at the second connection port of the WiFi communication module as a result of a connection between the second connection port of the WiFi communication module and an RF antenna being enabled in response to an enabling signal received at a control terminal of a second switch from a second output terminal of a WiFi signal strength detector of the WiFi module.

11. The method of claim 9 , wherein an indicator is included in the WiFi beacon message to distinguish between the WiFi network and the LiFi network.

12. the user device is connected to the WiFi network; the detecting step includes detecting a WiFi beacon message being received at a first connection port of the WiFi communication module; The method of claim 8 , wherein the initiating step includes initiating a handover from the WiFi network to the WiFi network.

13. 13. The method of claim 12, wherein the WiFi beacon message is received at the first connection port of the WiFi communication module as a result of a connection between the first connection port of the WiFi communication module and the OFE being enabled in response to an enabling signal received at a control terminal of a first switch from a first output terminal of a WiFi signal strength detector of the WiFi module.

14. The method of claim 12 , wherein an indicator is included in an LiFi message to distinguish between the WiFi network and the LiFi network.

15. 10. A computer program product comprising a computer readable storage medium storing instructions that, when executed on at least one processor, cause the at least one processor to perform the method of claim 8.

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