WO2024013159A1

WO2024013159A1 - A method of a system for determining a position of a mobile terminal device relative a coverage area of an optical wireless communication module

Info

Publication number: WO2024013159A1
Application number: PCT/EP2023/069169
Authority: WO
Inventors: Gang Wang; Ying Dong WEI; Jia Long QIU
Original assignee: Signify Holding B.V.
Priority date: 2022-07-12
Filing date: 2023-07-11
Publication date: 2024-01-18

Abstract

A method of determining a position of a mobile terminal device relative to a coverage area of an optical wireless communication module providing wireless network connectivity, the mobile terminal device comprising or being operatively connected to an optical wireless transceiver unit, the method performed by a processor and comprising the steps of: determining a zone of a multizone Time of Flight, ToF, sensor as corresponding to a location of the optical wireless transceiver unit of the mobile terminal device based on strength data received from the ToF sensor, the strength data related to ambient optical signal in a field of view of the ToF sensor, the field of view of the ToF sensor being larger than and covering the coverage area of the optical wireless communication module; obtaining distance data of the determined zone from the ToF sensor, and determining a position of the mobile terminal device relative to the coverage area of the optical wireless communication module based on the obtained distance data.

Description

A method of a system for determining a position of a mobile terminal device relative a coverage area of an optical wireless communication module

TECHNICAL FIELD

The present disclosure generally relates to the field of optical wireless communication, more particularly, to a method of and a system for determining a position of a mobile terminal device relative to a coverage area of an optical wireless communication module.

BACKGROUND

Nowadays, an increasing number of devices are connect to the Internet, most wirelessly. This places the conventional wireless communication technologies making use of Radio Frequency, RF, technologies under much pressure. The reason is twofold. In the first place, the RF spectrum is becoming much congested; besides, there are areas where RF wireless communication is not permitted or does not fit well.

The recently developed Light Fidelity, LiFi, technology is an optical wireless communication technology which utilizes light to transmit or communicate data between devices, over for example visible light, ultraviolet, and infrared spectrums.

Wireless LiFi communication is a viable technology of data communication to augment traditional radio-frequency -based communication techniques. Moreover, LiFi communication is advantageous over wireless RF communication in various aspects.

For example, the light spectrum as used in LiFi is much wider compared to the RF spectrum; it offers higher data rates, and is usable in areas susceptible to electromagnetic interference such as aircrafts. Moreover, communication over light supports data densities that are significantly higher than in RF, due to the almost unlimited bandwidth of the visible/invisible light spectrum.

A LiFi system generally comprises for example an access point comprising a LiFi APs positioned on the ceiling, which is for example integrated with a luminaire, and a LiFi access keys plugged into a mobile device such as a laptop or tablet, via for example a Universal Serial Bus, USB, interface. The USB LiFi key is arranged to receive data and send data back to the LiFi AP. It is known that LiFi communication has limited coverage as light cannot penetrate through obstacles such as walls. Besides, for the LiFi connection to work properly, the LiFi USB key must be located within the LiFi coverage area of the LiFi AP.

For wireless LiFi communication in the invisible or infrared spectrum, it is not possible for a user to see the LiFi signal as the light is invisible to human being. Besides, it is neither practical nor convenient for a regular user to get the distance between his/her mobile device and the LiFi AP on the ceiling.

Even if the user knows the distance, it is still not practical or convenient for the user to remember or make sure that the mobile device is placed within the coverage area of the LiFi AP.

W02019076660A1 discloses a controller for controlling a lighting device of a people transportation object. The people transportation object is configured to traverse a plurality of locations. The controller comprises: a receiver configured to obtain location information indicative of a current location, an upcoming location and/or a destination location of the people transportation object, and a processor configured to control the lighting device such that the light output of the lighting device comprises an embedded code indicative of the current location, the upcoming location and/or the destination location of the people transportation object.

In consideration of the above, there is a genuine need of a method and a system for determining a position of a mobile terminal device relative a coverage area of an optical wireless communication module, so as to allow the user to know the precise LiFi coverage area easily and to better position his or her laptop to get a good and stable LiFi connection.

SUMMARY

In a first aspect of the present disclosure, there is presented a method of determining a position of a mobile terminal device relative to a coverage area of an optical wireless communication module providing wireless network connectivity, the mobile terminal device comprising or being operatively connected to an optical wireless transceiver unit, the method performed by a processor and comprising the steps of: determining a zone of a multizone Time of Flight, ToF, sensor as corresponding to a location of the optical wireless transceiver unit of the mobile terminal device based on strength data received from the ToF sensor, the strength data related to ambient optical signal in a field of view of the ToF sensor, the ToF sensor having a field of view larger than or equal to and covering the coverage area of the optical wireless communication module; obtaining distance data of the determined zone from the ToF sensor, and determining a position of the mobile terminal device relative to the coverage area of the optical wireless communication module based on the obtained distance data.

The present disclosure is based on the insight that a position of a mobile terminal device relative to a coverage area of an optical wireless communication module providing wireless network connectivity to the mobile terminal device can be accurately determined based on both a strength of an optical signal emitted by an optical wireless transceiver unit of the mobile terminal device and a distance between the mobile terminal device and the optical wireless communication module.

When the mobile terminal is within the FoV of the ToF sensor, a position of the mobile terminal device relative to the ToF sensor can be determined. However, it is impossible for a low resolution ToF sensor to determine if there is a mobile terminal, or an optical wireless transceiver unit connected to the mobile temal device, in its FoV via "recognition".

The inventor realized that an optical signal emit by the optical wireless transceiver unit connected to the mobile terminal device towards the optical wireless communication module can also be received by a light receiver of the ToF sensor, if the optical wireless transceiver unit is placed in the FoV of the ToF sensor.

Based on the above, by arranging the ToF sensor to have a FoV larger than and covering the coverage area of the optical wireless communication module connected to the mobile terminal device and checking the strength data related to ambient optical signal in the FoV the ToF sensor, the position of the mobile terminal device can be determined. This is because the signal strength of a zone of the ToF sensor mapped to a physical location having the optical wireless transceiver unit would be significantly different than other zones.

After determining the zone of the ToF sensor corresponding to the location of the optical wireless transceiver unit, a distance between the optical wireless transceiver unit, that is, the mobile terminal device, and the optical wireless communication module is obtained from the ToF sensor.

As the distance data of the optical wireless transceiver unit represents three dimensional coordinate (x,y,z) of the optical wireless transceiver unit in a coordinate system with the ToF sensor, and possibly also the optical wireless communication module as the origin (0,0,0), the position of the mobile terminal device relative to the coverage area of the optical wireless communication module can then be easily determined based on the obtained distance data.

The position of the mobile terminal device relative to the coverage area of the optical wireless communication module may be used to enable a user of the mobile terminal device to become aware where the mobile terminal device is presently located in the coverage area. The user can move the mobile terminal device to a location having optimal network connection, if necessary.

The method of the present disclosure may be performed by a processor of the mobile terminal device or a processor of the ToF sensor or the optical wireless communication module.

In an example of the present disclosure, the ToF sensor and the optical wireless communication module are two independent devices and the ToF sensor is installed next to or integrated into the optical wireless communication module.

When the ToF sensor and the optical wireless communication module are two independent or separate devices, for the ToF sensor to have a field of view larger than and covering the coverage area of the optical wireless communication module, the ToF sensor can be installed immediately next to the optical wireless communication module. On the other hand, the ToF sensor may also be integrated into the optical wireless communication module, which may be for example a luminaire installed at a ceiling of an office space.

In an example of the present disclosure, the ToF sensor is integrated with the optical wireless communication module by configuring the ToF sensor and the optical wireless communication module to share a same optical transmitter and to have separate optical receivers.

As both the ToF sensor and the optical wireless communication module make use of a light emitter and a light transceiver, the ToF sensor and the optical wireless communication module can be integrated into one device. In this case, the ToF sensor and the optical wireless communication module can be made to share a same optical transmitter or light emitter while each still have an independent or separate optical receiver.

This reduces the hardware cost while ensures that the position of the optical wireless transceiver unit to be determined more accurately, as the ToF sensor and the optical wireless communication module are essentially placed at a same location, which means the measured distance to the optical wireless transceiver unit is the same for the ToF sensor and the optical wireless communication module. In an example of the present disclosure, the strength data received from the ToF sensor comprises an array of strength values, the determined zone has the highest strength value of the array.

When the optical wireless transceiver unit is operating and transmitting optical signal for data communication, the signal strength of the zone of the ToF sensor corresponding to a location of the optical wireless transceiver unit will be significantly higher than other zones. Therefore, of the array of strength values related to ambient optical signal in the FoV of the ToF sensor, the one having the highest strength value, which in the same time is significantly higher than values of other zones, is the zone mapped to the optical wireless transceiver unit.

This only involve simple numerical comparison and can be performed in a straightforward and resource saving manner.

In an example of the present disclosure, the mobile terminal device comprises a display interface, the method further comprises the step of indicating the determined position of the mobile terminal device relative to the coverage area of the optical wireless communication module on the user interface.

This allows the user of the mobile terminal device to become intuitively aware of the relative location of the mobile terminal device relative to the coverage area of the optical wireless communication module.

As a specific example, the step of indicating comprises indicating, on the user interface, the coverage area of the optical wireless communication module as a circle and the position of the mobile terminal device relative to the circle.

Visualizing the position of the mobile terminal device relative to the coverage area of the optical wireless communication module gives the user the most straightforward illustration of whether the mobile terminal device is located in a location having better connection.

In an example of the present disclosure, the step of indicating further comprises indicating a moving direction allowing a connection between the optical wireless communication module and the mobile terminal device to be improved on the user interface.

By following the indication and adjusting the location of the mobile terminal device, the user can optimize network connection to the optical wireless communication module. In an example of the present disclosure, the optical wireless communication module comprise a LiFi access point, the optical wireless communication transceiver unit of the mobile terminal device comprise a plug-and-play LiFi key.

In a specific example, the LiFi access point and the LiFi key operate in an infrared band, the ToF sensor operates in the same infrared band.

This method can be used especially advantageously to a LiFi system comprising a LiFi access point and a LiFi key plugged to a mobile terminal device.

Having the method described above running on such commonly used LiFi network devices allows a regular use to benefit from the advantage of the present disclosure, that is, to allow the user to know the precise LiFi coverage area easily and to better position his or her laptop to get a good and stable LiFi connection.

A second aspect of the present disclosure provides system for determining a position of a mobile terminal device relative to a coverage area of an optical wireless communication module providing wireless network connectivity, the system comprising the optical wireless communication module, the mobile terminal device and a multizone time of flight, ToF, sensor, the mobile terminal device comprising or being operatively connected to an optical wireless transceiver unit, the ToF sensor being arranged to have a field of view larger than or equal to and covering the coverage area of the optical wireless communication module, at least one of the optical wireless communication module, the mobile terminal device and the ToF sensor comprises a processor, wherein: the ToF sensor is arranged to measure distance data between the mobile terminal device and the optical wireless communication module and strength data related to ambient optical signal in a field of view of the ToF sensor, and to transmit the distance data and the strength data to the processor; the processor is arranged to: determine a zone of the multizone ToF sensor as corresponding to a location of the optical wireless transceiver module of the mobile terminal device based on strength data received from the ToF sensor; obtain a distance of the determined zone from the ToF sensor, and determining a position of the mobile terminal device relative to the coverage area of the optical wireless communication module based on the obtained distance.

The system operates according to the method described in the first aspect of the present disclosure to indicate the position of the mobile terminal device in the coverage area of the optical wireless communication transceiver, allowing the user to position his or her mobile device in a position having optimal network connection.

A third aspect of the present disclosure provides a computer program product, comprising a computer readable storage medium storing instructions which, when executed on at least one processor, cause said at least one processor to carry out the method according to the first aspect of the present disclosure.

The above mentioned and other features and advantages of the disclosure will be best understood from the following description referring to the attached drawings. In the drawings, like reference numerals denote identical parts or parts performing an identical or comparable function or operation.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a diagram schematically illustrating coverage area of an optical wireless communication module.

Fig. 2 schematically illustrates arrangement of a ToF sensor in the LiFi system of Figure 1, according to the present disclosure.

Fig. 3 schematically illustrates, in a block diagram, a device integrating a LiFi AP and a ToF sensor.

Fig. 4 schematically illustrates an exemplary PHY frame.

Fig. 5 schematically illustrates, in a flow chart type diagram, an embodiment of a method of determining a position of a mobile terminal device in a coverage area of an optical wireless communication module providing wireless network connectivity, according to the present disclosure.

Fig. 6 schematically illustrates an embodiment of a laptop with a LiFi USB Key placed on a table.

Figs. 7a to 7c are exemplary distance data and signal strength data measured by the ToF sensor of Fig. 2.

Figs. 8a to 8c are exemplary user interface for visualizing the coverage area of the LiFi AP to the user.

DETAILED DESCRIPTION

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 limited to only the embodiments set forth herein. Rather, the illustrated embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

The inventive concept of the present disclosure will be described with reference to an exemplary LiFi network system operating in the infrared spectrum. It will be understood by a skilled person that the principle described herein applies also to other optical wireless communication network system.

The term “optical wireless communication module” is used in the present disclosure to refer to a device allowing a terminal or client device to access an optical wireless network. An example of the “optical wireless communication module” is described hereafter as a LiFi access point, AP.

The term “optical wireless transceiver unit” is used in the present disclosure to refer to the terminal device accessing the optical wireless network via the optical wireless communication module, or a transceiver connected to or comprised in such a terminal device. An example of the “optical wireless transceiver unit” is described hereafter as a LiFi USB key pluggable to the terminal device via a USB interface.

However, from a technical point of view, it can be understood by a skilled person that both the “optical wireless communication module” and the “optical wireless transceiver unit” can be referred to as a transceiver as they both transmit and receive data over the optical wireless network.

As described in the background section, LiFi is emerging as a viable technology of data communication to augment traditional radio-frequency-based communication techniques.

Though direct line of sight is not necessary for electronic devices enabled with LiFi capability to communicate data between each other, in practice a coverage area of for example a LiFi access point is determined based on light of sight between a transmitter and a receiver.

Figure 1 is a diagram 10 schematically illustrating coverage area of an optical wireless communication module, here a LiFi access point, AP, 11.

In the example, a LiFi AP 11 is integrated into a luminaire (not shown) on the ceiling with a height of dl of 2.8m. The LiFi AP 11 modulates light such as infrared light and provides data transmission for devices, such as mobile terminal devices including laptops, located in its coverage area, depicted overall as a cone 12 in Figure 1.

In practice, the coverage area 12 of the LiFi AP 11 varies depending on a distance between the LiFi AP 11 and a circle containing a mobile terminal device having the LiFi USB key 13 plugged therein. Referring to Figure, 1, the coverage areas at different distances dl to d3 from the LiFi AP 11 are depicted as a number of circles with different radius rl to r3.

In our example, a mobile device such as a laptop connecting the LiFi USB key 13 is placed on a table with a height of 0.8m, which means a distance d2 between the LiFi AP 11 and the LiFi USB key 13 is about 1.8m. To have a good LiFi connection, the laptop must be placed within the circle of having a radius r2, here about one meter, under the LiFi transceiver.

It is noted that the distances and radius are described for exemplary purpose only and is not limiting to the present disclosure. Moreover, the mobile terminal device and the LiFi USB key are used interchangeable hereafter.

As described in the background, a user of a mobile terminal device accessing the LiFi network normally is not aware of an area or a position having optimal LiFi connection.

The present disclosure proposes to visualize the LiFi coverage area of the LiFi AP 11 to the user, for example on a display of the laptop into which the LiFi USB key 13 is plugged.

For the purpose of visualizing the LiFi coverage area to the user, the relative position between the LiFi AP 11 and the LiFi USB key 13 (or the mobile terminal device) has to be known. Based on the inventive idea of the present disclosure, a Time of Flight, ToF sensor is used to determine the relative position between the LiFi AP 11 and the LiFi USB key 13.

A light ToF sensor directly measures a distance from the sensor to an object based on a time for photons emitted by an emitter of the ToF sensor to be reflected by the object and detected by a receiver of the ToF sensor, enabling distance ranging.

However, with a low-resolution ToF sensor, such as an 8x8 ToF sensor, it is difficult to distinguish a USB LiFi key from a similar object such as a mobile phone on the table by relying only on the measured distance between the ToF sensor (or the LiFi AP) and the object.

It is known that the LiFi USB key can emit IR light, of for example 940nm IR light, towards the LiFi AP. Such IR light may also be received by the ToF sensor if the LiFi USB key is in the FoV of the ToF sensor, and the ToF sensor also operates in the same IR band. In contrast, similar objects or devices in the FoV of the ToF sensor cannot emit IR light. The difference is used in the present disclosure to determine the precise location of the LiFi USB key.

Figure 2 schematically illustrates arrangement of a ToF sensor in the LiFi system of Figure 1.

The system of Figure 2 further comprises, in addition to a LiFi AP 21, a ToF sensor 25, which is arranged to have a field of view, FoV 26, larger than or equal to and covering or overlapping the coverage area 22 of the LiFi AP 21.

The ToF sensor 25 is installed at a same location as the LiFi AP 21. In practice, the ToF sensor 25 may be placed for example just beside or immediately next to the LiFi AP 21. The ToF sensor 25 may also be integrated into a same luminaire comprising the LiFi AP 21. Such an arrangement ensures that the FoV 26 of ToF sensor 25 covers or encloses, or at least overlaps with, the whole LiFi coverage area 22, as illustrated in Figure 2.

The ToF sensor 25 is configured to measure ambient signal strength in its FoV 26. The ambient signal strength of a zone containing a LiFi USB key, emitting light, connected to a mobile terminal device accessing the network via the LiFi AP 21 is significantly higher than other zones. The present disclosure thereby employs the ambient signal strength data measured by the ToF sensor to determine a location having the LiF USB key. Thereafter distance data obtained by the ToF sensor 25 of the same location is used to determine the relative position between the LiF USB key and the LiFi AP 21.

In this example, the ToF sensor 25 and the LiFi AP 21 are two separate and independent devices. The ToF sensor 25 may be for example a low-resolution multi-zone infrared, IR, ToF sensor. The ToF sensor 25 comprises an IR emitter such as a Light Emitting Diode, LED, or a laser/Vertical-cavity surface-emitting laser, VCSEL, and an IR receiver. The IR emitter sends photons which are reflected by an object in the FoV 26 of the ToF sensor 25 and then detected by the receiver. The time difference between the emission and the reception provides the actual distance between the object and the ToF sensor.

A controller controls the working of ToF sensor and LiFi AP, so that the working periods of the ToF sensor and the LiFi AP are not overlapped but are interleaved.

It is also possible to integrate the ToF sensor and the LiFi AP into one device. This structure can be advantageously used in a LiFi system according to the present disclosure.

Figure 3 schematically illustrates, in a block diagram, a device 300 integrating a LiFi AP and a ToF sensor. Referring to Figure 3, the device 300 integrates a LiFi AP 310 and a ToF sensor 350. The ToF sensor 350 is indicated by a block of solid line, and the LiFi AP 310 is indicated with dashed line.

The ToF sensor 350 comprises a ToF processor 351, a light receiver or detector 352 and a light transmitter 353. The LiFi AP 310 comprises a LiFi baseband module 311, an analog front end, AFE, module 312, a light receiver 313 and the light transmitter 353.

It is seen from Figure 3 that the ToF sensor 350 and the LiFi AP 310 share the same light transmitter 353, which may be for example a LED or VCSEL as known to those skilled in the art.

For the light receiver or detector 352 of the ToF sensor may comprise a Single-photon avalanche diode, SPAD or a SPAD array. This is especially advantageous for very low energy signal application due to the high sensitivity of the SPAD.

The light receiver 313 of the LiFi AP 310 may comprise a PIN diode or an avalanche photodiode, APD.

In practice various optoelectronic semiconductor devices, including photodiode, CMOS/CCD image sensor, PIN diode, and APD may be used as the light receiver 313 of the LiFi AP 310.

Among these devices, PIN diode and APD are widely used for high-speed LiFi and optical fiber communication due to its comprehensive performance of high-speed, good sensitivity, cost, size and complexity of receiving circuit. PD and CMOS/CCD image sensor are commonly used to be receivers for low speed LiFi system.

The device 300 works in a hybrid mode. In operation, the ToF sensor 350 operates to measure distance and ambient signal strenghty of objects within the FoV of the ToF sensor, while the LiFi AP provides LiFi connections to devices within its coverage range. The SPAD detector 350 is used only by the ToF sensor 350 while the PIN/APD receiver 313 is used only by the LiFi AP 310. The LED/VCSEL 353 part is used by both the ToF sensor 350 and the LiFi AP 310.

By integrating ToF sensor and LiFi AP by sharing the emitter, it's easier to realize the interleaved working of the two.

As the LiFi AP 310 and the ToF sensor 350 are combined as a single device 300, the ToF sensor 350 is synchronized with the LiFi AP 310 and uses a part of communication time and frame length of the LiFi communication module. Here no synchronization between the ToF sensor 350 and LiFi clients is needed. As an example, in a LiFi connection, a part of preamble of a physical PHY frame header may be used for ToF Tx to get signal reflection. An exemplary PHY frame 40 is illustrated in Figure 4. The PHY frame 40 comprises a preamble 41, a header 42, additional channel estimation symbols 43 and payload 44.

Measurement data from the ToF sensor 350 may be transmitted using the preamble 41 of the exemplary PHY frame 40.

Specifically, for measuring ambient signal strength, the ToF sensor 350 receives the signal strength by its detector or Rx 352 from the environment, including for example USB LiFi key or dongle connected to a mobile terminal device within the FoV of the ToF sensor 350.

For measuring a distance of an object, and possibly ambient signal reflectance, the transmission of the measured data by the ToF sensor 350 is combined with the LiFi communication preamble.

As an example, for a typical distance measuring performed by a ToF sensor, it first emits a narrow pulse light towards the object, and then receives a reflected light and analyzes the receiving time distribution to determine the time of flight, thereby calculating the distance to the object.

In this process, the narrow pulse light has an appropriate length of time, such as 5us, which is neither so long as to cause signal overlapping and make it hard to determine the time of flight, nor so short as to providing too little power to get enough SNR. One narrow pulse has a time interval with a next narrow pulse light so as to enable the current measuring completed.

For a preamble of a physical PHY frame header of LiFi communication, it works in a relatively low frequency in the whole communication process, which is suitable to get an appropriate length of “narrow pulse light”. This preamble may have an SYNC part for synchronization and a start of frame delimiter, SFD, part for frame boundary detection.

As an example, in practice, both parts may have alternatively “1” and “0” value, with a “1” value used as the “narrow pulse light” and a “0” value used as the “time interval”.

It is also possible that in some cases the preamble is too complicated and hard to directly get effective “narrow pulse light’ and “time interval”. It this case, these “narrow pulse light’ and “time interval” may be added into the preamble and this will have little impact on the communication process. By determining from the preamble the time of the emitted narrow pulse light and the received reflected light, the distance to the object may be calculated as described above.

The device 300 as described above is advantageous in that interference between the ToF sensor 350 and the LiFi AP can be effectively avoided and the transmitter 353 and related circuit is multiplexed.

Figure 5 schematically illustrates, in a flow chart type diagram, an embodiment of a method of determining a position of a mobile terminal device in a coverage area of an optical wireless communication module providing wireless network connectivity, according to the present disclosure.

Referring to Figures 1 and 5 at the same time, at step 51, a mobile terminal device determines a zone of a multizone ToF sensor as corresponding to a location of the optical wireless transceiver unit of the mobile terminal device based on strength data received from the ToF sensor, the strength data related to ambient optical signal in FoV of the ToF sensor, the FoV of the ToF sensor is larger than and covering the coverage area of the optical wireless communication module.

The optical wireless transceiver unit may be for example the LiFi USB key 13 plugged into a laptop accessing the wireless network via an optical wireless communication module, such as the LiFi AP 11.

The ToF sensor measures the ambient signal strength from objects in its FoV as well as its distance data to such objects and transmits the ambient signal strength and the distance data to the mobile terminal device such as the laptop. The transmission may be done via the LiFi AP, or directly to mobile terminal device.

As the FoV of the ToF sensor is larger than the coverage area of the LiFi AP, even if the mobile terminal device is at an outer edge or even outside the coverage area of the LiFi AP, the ToF sensor can still obtain such measurement data from the mobile terminal device.

The ToF sensor used in the present disclosure is a 3D sensor which can measure a location of an object (x,y,z) in a three dimensional coordinate system with the sensor as the origin (0,0,0). As the ToF sensor is arranged immediately next to the LiFi AP, or the ToF sensor and the LiFi AP are integrated as a single device, the measured location (x, y, z) of the object is also considered as being representing in a three dimensional coordinate system with the LiFi AP as original. The ToF sensor in the invention may be a low-resolution sensor with for example 8x8=64 zones. To determine whether there is a LiFi USB key within its FoV, the ToF sensor monitors ambient optical signal strength, such as IR strength of each zone. When the LiFi USB key emits signals, that is, IR signals, the ambient IR strength of the zone which contains the LiFi USB key will increase significantly. This is used to identify whether a zone containing the LiFi USB key.

In other words, the strength data received from the ToF sensor comprises an array of strength values. In an example, the zone having a strength value significantly higher value than other zones, as compared with normal values, of the array is determined to contain the LiFi USB key.

In practice, the zone having the highest strength value, which is in the same time higher than the values of other zones by for example an order, is determined to comprise the LiFi USB key.

According to another example, the LiFi USB key may also be controlled by the mobile terminal device to emit light according to a defined pattern. The pattern may be for example emitting light for a first time period, emitting no light for a second time period and then emitting light for a third time period. In this case, a zone having strength data corresponding to the defined pattern is determined to contain the LiFi USB key.

At step 52, the mobile terminal device 13 obtaining distance data of the determined zone from the ToF sensor.

Such distance data includes the (x, y, z) coordinates of the LiFi USB key and are measured together with the strength data. The mobile terminal device obtains the distance data of the determined zone, such data will be used at the next step to determine a position of the LiFi USB key relative to the LiFi AP.

It is observed that accuracy of the measured distance data may be compromised due to interference between both the LiFi AP and the LiFi client the ToF sensor. Actually, the location of the LiFi USB key (the client in which zone) can still be detected despite the interference and is still reliable, but the measured distance may not be as accurate.

For the purpose of having more accurate distance data, the currently detected location and historical distance data may be used together to determine the distance of the LiFi USB key. Alternatively, more accurate distance result may be obtained by increasing observation period, by referring to more data collected during the extended observation period. At step 53, the mobile terminal device 13 determines a position of the mobile terminal device relative to the coverage area of the optical wireless communication module based on the obtained distance data.

Specifically, the location of the determined zone is used to determine (x,y) coordinates of the LiFi USB key and a distance value of the zone is used to determine (z) coordinates of the LiFi USB key.

With both the location and the distance of the LiFi USB key available, its position relative to the LiFi AP can be determined accordingly.

At step 54, the mobile terminal device 13 may indicate determined position of the mobile terminal device relative to the coverage area of the optical wireless communication module on for example its user interface. Such indication will be described in detail with an example thereafter.

It can be contemplated by a skilled person that the method of Figure 3 is performed by a processor of the mobile terminal device. It may also be performed by a processor of the ToF sensor or the LiFi AP.

It will be understood by those skilled in the art the determined relative position, when not determined by the mobile terminal device, may be passed to the mobile terminal device, which can then conveniently indicate the position to the user on its interface.

The method of Figure 5 is hereafter described in detail with reference to an example illustrated in Figure 6 and Figures 7a-7c.

Referring to Figure 6, a laptop 69 with a LiFi USB Key 63 is placed on a table 68 with a height of for example 60 cm. On the ceiling a ToF sensor (not shown) with 64 (8x8) zones is mounted at a some location as a LiFi AP (not shown), for example at a height of 240 cm.

Figure 7a shows distance data between the laptop/the LiFi USB key and the LiFi AP, measured by the ToF sensor. The distance data is an array with a size of 8x8, with a value in each zone or element of the array indicating a distance between the ToF sensor and a closest object in the specific zone.

With such distance data, based on a rough distance between the table 68 and the LiFi AP, it can be decided that the four zones marked in the rectangle 71 may represent a surface area of the table 68.

It is however not possible to determine an exact location of the LiFi USB key

63 by just using these distance data. Therefore, strength data of IR signals emitted by the LiFi USB key 63 is used together with the distance data to determine the precise or exact location of the LiFi USB key 63.

Figures 7b and 7c illustrates ambient IR strength data measured by the same ToF sensor. A value in each zone or element indicates a number of photons (kilo-count per second) received by the IR receiver of the ToF sensor.

Figure 7b is the measured IR strength data when the LiFi USB Key is not working. As a result, the ambient IR strength of all 64 zones are low, with a maximum value of 15.

Figure 7c is when the USB Key is working, that is, emitting IR signal. This leads to a significant increase of the ambient IR strength of the zone containing the USB Key as well as a few neighboring zones. The zone at row 5 column 4, R5C4, marked by the rectangular 73 with the highest value (3733) is the zone containing the USB Key. This indicates that the LiFi USB Key is positioned within this zone.

For a ToF sensor that includes a lens over the IR receiver which flips (horizontally and vertically) the captured image of the target, the position of the USB Key is corresponding to zone R5C4 instead of zone R5C3.

When the USB Key is working, the distance data in Figure 7a remain unchanged. In this way, the relative position between the transceiver and the USB Key is obtained.

The determined relative location between the LiFi USB key and the LiFi AP may be illustrated or indicated on a user interface of the mobile terminal device, thereby enabling the user to become aware of the LiFi coverage area and to adjust the location of the mobile terminal device if necessary.

This can be realized by a software application with an intuitive user interface, as illustrated in Figures 8a to 8c as an example. On the user interface 80, a small rectangle represents the laptop and is always in the central position of the user interface 80. A shape showing an area, such as a circle, represents the coverage area of one LiFi AP in the vicinity of the laptop. The position of the circle illustrates the actual LiFi coverage of the space where the laptop locates.

Referring to Figure 8a, the laptop 81 (i.e., the USB key) is outside the LiFi coverage 82, which means the connection quality is bad. An arrow 83 pointing to the center of the LiFi coverage circle 82 may be used to guide the user to adjust the position of the laptop 81. Once the laptop 81 is moved inside the coverage circle 82 as shown in Figure 6b, the connection quality becomes good. The arrow 83 shows how to further improve the connection quality. In Figure 8c, the laptop 81 is located at the center of the coverage circle 82 and the connection quality is excellent. The inventive concept of the present disclosure is described above with reference to a LiFi network system operating in the infrared band. Those skilled in the art will understand that the above examples are described for illustrative purpose only and the method can be applied to LiFi network in other bandwidth as well.

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

Claims

CLAIMS:

1. A method (50) of determining a position of a mobile terminal device (69) relative to a coverage area (12, 22) of an optical wireless communication module (11, 21) providing wireless network connectivity, the mobile terminal device (69) comprising or being operatively connected to an optical wireless transceiver unit (13, 63), the method performed by a processor comprising the steps of: determining (51) a zone of a multizone Time of Flight, ToF, sensor (25) as corresponding to a location of the optical wireless transceiver unit (13, 63) of the mobile terminal device (69) based on strength data received from the ToF sensor (25), the strength data related to ambient optical signal in a field of view (26) of the ToF sensor (25), the field of view (26) of the ToF sensor (25) being larger than or equal to and covering the coverage area (12, 22) of the optical wireless communication module (11, 21), wherein the optical wireless transceiver unit (13, 63) emits light for being captured by the ToF sensor, and the strength data received from the ToF sensor (25) comprises an array of strength values, a strength value in the determined zone is significant higher than strength values of other zones of the array; obtaining (52) distance data of the determined zone from the ToF sensor (25), and determining (53) a position of the mobile terminal device (69) relative to the coverage area (12, 22) of the optical wireless communication module (11, 21) based on the obtained distance data.

2. The method (50) according to claim 1, wherein the ToF sensor (25) and the optical wireless communication module (11, 21) are two independent devices and the ToF sensor (25) is installed next to or integrated into the optical wireless communication module (11, 21).

3. The method (50) according to claim 1, wherein the ToF sensor (350) is integrated with the optical wireless communication module (310) by configuring the ToF sensor (350) and the optical wireless communication module (310) to share a same optical transmitter (353) and to have separate optical receivers (352, 313).

4. The method (50) according to any of the previous claims 1 to 3, wherein optical wireless transceiver unit (13, 63) of the mobile terminal device (69) is configured to emit light according to a defined pattern over time, the strength data in the determined zone corresponds to the defined pattern over time.

5. The method (50) according to any of the previous claims, wherein the mobile terminal device (69) comprises a display interface (80), the method further comprises the steps of: indicating (54) the determined position of the mobile terminal device relative to the coverage area (12, 22) of the optical wireless communication module (11, 21) on the user interface (80).

6. The method (50) according to claim 5, the step of indicating (54) comprising indicating, on the user interface, the coverage area (12, 22) of the optical wireless communication module (11, 21) as a circle (83) and the position of the mobile terminal device relative to the circle (82).

7. The method (50) according to claim 5 or 6, the step of indicating (54) further comprising indicating a moving direction (83) allowing a connection between the optical wireless communication module (11, 21) and the mobile terminal device to be improved on the user interface (82).

8. The method (50) according to any of the previous claims, wherein the optical wireless communication module (11, 21) comprise a LiFi access point, the optical wireless transceiver unit (13, 63) of the mobile terminal device (69) comprise a plug-and-play LiFi key.

9. The method (50) according to claim 8, wherein the LiFi access point and the LiFi key operate in an infrared band, the ToF sensor operates in the same infrared band.

10. A system for determining a position of a mobile terminal device relative to a coverage area (22) of an optical wireless communication module (21) providing wireless network connectivity, the system comprising the optical wireless communication module (21), the mobile terminal device and a multizone time of flight, ToF, sensor (25), the mobile terminal device comprising or being operatively connected to an optical wireless transceiver unit, the ToF sensor (25) being arranged to have a field of view (25) larger than or equal to and covering the coverage area (22) of the optical wireless communication module (21), at least one of the optical wireless communication module (21), the mobile terminal device and the ToF sensor (25) comprises a processor, wherein: the optical wireless transceiver unit (13, 63) is arranged to emit light for being captured by the ToF sensor, and the ToF sensor (25) is arranged to measure distance data between the mobile terminal device and the optical wireless communication module (21) and strength data related to ambient optical signal in a field of view (26) of the ToF sensor (25), and to transmit the distance data and the strength data to the processor; the processor is arranged to: determine a zone of the multizone ToF sensor as corresponding to a location of the optical wireless transceiver unit of the mobile terminal device based on strength data received from the ToF sensor, wherein the strength data received from the ToF sensor (25) comprises an array of strength values, a strength value in the determined zone is significant higher than strength values of other zones of the array; obtain a distance of the determined zone from the ToF sensor, and determining a position of the mobile terminal device relative to the coverage area of the optical wireless communication module based on the obtained distance.

11. The system according to claim 10, wherein the ToF sensor (25) and the optical wireless communication module (21) are two independent devices and the ToF sensor (25) is installed next to or integrated into the optical wireless communication module (21), or the ToF sensor (350) is integrated with the optical wireless communication module (310) by configuring the ToF sensor (350) and the optical wireless communication module (310) to share a same optical transmitter (353) and to have separate optical receivers (352, 313).

12. The system according to claim 10 or 11, wherein the mobile terminal device comprises a display interface arranged to display the determined position of the mobile terminal device relative to the coverage area of the optical wireless communication module.

13. The system according to any of the previous claims 10 to 12, wherein the optical wireless communication module comprise a LiFi access point, the optical wireless transceiver unit of the mobile terminal device comprise a plug-and-play LiFi key, the LiFi access point and the LiFi key operate in an infrared band, the ToF sensor operates in the same infrared band.

14. A computer program product, comprising a computer readable storage medium storing instructions which, when executed on at least one processor, cause said at least one processor to carry out the method according to any of the previous claims 1 to 9.