DEVICE RELATIVE TO A USER BODY AND A METHOD THEREOF

FIELD OF THE INVENTION

The invention relates to a method for determining a relative position of a mobile device relative to a user body. The invention further relates to a control device, a system and a computer program product for determining a relative position of a mobile device relative to a user body.

BACKGROUND

Connected lighting refers to a system of one or more lighting devices which are controlled not by (or not only by) a traditional wired, electrical on-off or dimmer circuit, but rather by using a data communications protocol via a wired or more often wireless connection, e.g., a wired or wireless network. Typically, the lighting devices, or even individual lamps within a lighting device, may each be equipped with a wireless receiver or transceiver for receiving lighting control commands from a lighting control device according to a wireless networking protocol such as Zigbee, Wi-Fi or Bluetooth.

These connected lighting devices can communicate and exchange communication and/or control messages with mobile devices such as a mobile phone, tablets, laptop etc. The connectivity for the lighting devices opens a new dimension for sensing applications utilizing these connected lighting devices. More specifically, connected lighting devices provide an excellent opportunity for distributed sensing applications such as detecting air quality, stress levels and well being. The sensing, e.g., radiofrequency-based sensing, can be based on connectivity between the connected lighting systems and mobile devices or communication between lighting devices.

WO 2014/120465A1 discloses a surveying technique for generating location fingerprint data. A mobile device can survey a venue by measuring, at multiple locations at the venue, signals from one or more signal sources. At each location, the mobile device can take multiple measurements of signals. The mobile device can take each measurement at a distinct orientation. The measurements can be used to determine expected measurements of the signals at the venue. Differences between the multiple measurements of signals can be used to determine a variance of the expected measurements. The expected measurements and variance can be designated as location fingerprint data for the venue. The location fingerprint data can be used by mobile devices for determining a location at the venue.

SUMMARY OF THE INVENTION

The inventors have realized that one important factor for distributed sensing utilizing mobile devices is the detection of phone sensing context, i.e., the position of the phone carried by a user (e.g., in the pocket, in the hand, inside a backpack, inside a purse, on the hip, arm mounted, etc.) in relation to the event being sensed; for example: an air-quality sensor or an ambient noise sensor offers poor sensing quality buried in a person's backpack.

Furthermore, for BLE-based COVID contact tracing utilizing mobile phones of users to determine physical proximity between a first person and a second person, the wearing position of the phone with respect to the user' s body is important. Similarly, the knowledge of the phone' s position may be used to adjust the maximum allowed wireless transmit power of the phone to minimize the wireless radiation exposure of sensitive body parts; for instance, if the phone is worn in the front pocket a lower maximum wireless transmit power is used than when the phone is stacked away in the backpack.

It is therefore an object of the present invention to address the problems as mentioned above or other related problems and provide an improved detection of the position of a mobile device with respect to the user body.

According to a first aspect, the object is achieved by a method of determining a relative position of a mobile device relative to a user body using at least one node, wherein the mobile device is carried by the user; and wherein the at least one node is arranged for transmitting and/or receiving radiofrequency signals; wherein the method comprises: receiving a signal indicative of an orientation information of the user; receiving a first and a second radiofrequency signal communicated between the mobile device and the at least one node, wherein the received first or the second radiofrequency signal is affected by the user body; comparing a signal characteristic of the received first and the second radiofrequency signals; determining the relative position of the mobile device with respect to the user’s body based on the comparison.

The method is related to the determination of a relative position of a mobile device with respect to a user body. The mobile device is carried by the user, such that mobile device is in (close) proximity of the user. In other words, the method aims at determining the position of the mobile device carried by a user e.g., in the pocket, in the hand, inside a backpack, on the hip, arm mounted, etc. The mobile device may be a mobile phone, a tablet, a wearable etc. For example, wearable can be a wearable sensor, e.g., whether the user is wearing the wearable is his/her right hand or left hand. In another example, the wearable can be any other device other than a sensing device, such a smart gadget etc.

The method utilizes at least one node for determining the relative position. The number of nodes may be greater than 1, e.g., 2 or more. The number of nodes may be based on an accuracy requirement for the determination and/or confidence level of the prediction. For example, if the phone sensing context is a critical sensing task, e.g., healthcare or wellbeing detection such as contact tracing information, and/or the output of the determination has low confidence, then the method may add more than 1 node for determination.

Each of the at least one node may be arranged for transmitting and/or receiving radiofrequency signals. For example, if there are more than one node, than few nodes may be arranged for only transmitting and few for only receiving or for both transmitting and receiving. The role of receiving and/or transmitting may be based on the position of the node relative to the user, location of the nodes in an environment, hardware capabilities of the node, wireless interference experienced by the node etc. The node may comprise a transmitter/receiver or a transceiver arranged for transmitting and/or receiving radiofrequency signals. Each or few of the at least one node may further comprise a processor arranged for processing the received radiofrequency signals.

The method comprises receiving a signal indicative of an orientation information of the user. The signal may be a wireless signal received by the at least one node or by any other device, e.g., a control device. The signal may be received from a sensor arranged for detecting orientation of the user. The orientation information may comprise the physical orientation of the user such as position of the user, head position of the user in a specific direction and a back position (e.g., towards the opposition direction), a posture information, a gesture information (e.g., person keeps strongly moving the arms) etc.

The method further comprises receiving a first and a second radiofrequency signal communicated between the mobile device and the at least one node, wherein the received first or the second radiofrequency signal is affected by the user body. The radiofrequency signal may comprise a signal from a radiofrequency spectrum, such as a GHz signal, a millimeter wave signal etc. The radio frequency signals may be received according to a wireless communication protocol which may use a protocol of any suitable type, including for example Bluetooth, ZigBee, or WiFi. The first and the second radiofrequency signals may be received by the at least one node or by any other device, e.g., a control device. The first and/or the second radio frequency may be transmitted from the mobile device and received by the at least one node or transmitted by the at least one node and received by the mobile device. The direction of the communication (the transmitter/receiver role) between the mobile device and the at least one node may change dynamically over time. The change may be based on a software update such as only for processing (e.g., comparison) the role of the transmitter/receiver is changed, whereas the transmission between the mobile device and the at least one node is uninterrupted.

The received first or the second radiofrequency signal is affected by the user body. The effect may be characterized by a change in signal characteristics of the first or the second radiofrequency signal. The effect may be caused by an interaction of the first or the second radiofrequency signal with the user body, such as the first or the second radiofrequency signal is reflected, absorbed, refracted, scattered etc., by the user body. Such interaction will affect the signal characteristics of the first or the second radiofrequency signals. Such an interaction may be based on the orientation of the user, location of the transmitting/receiving node and the relative position of the mobile device relative to the user body, such that based on the orientation of the user, location of the node and the relative position, either the first signal is affected by the user body, or the second signal is affected by the user body. In an example, both the first and the second radiofrequency signal are affected by the user body. In that case, the effect which changes the signal characteristics exceeding a threshold is considered, and the effect for which the changes in the signal characteristic does not exceed the threshold is not considered an effect. In an example, the effect for both the first and the second radiofrequency signals may exceed the threshold, then difference of the effect of the first and the second radiofrequency signal may be considered.

The method further comprises comparing a signal characteristic of the received first and the second radiofrequency signals. The comparison or the processing may be performed by the at least one node and/or by any other device, e.g., the mobile device, a control device. The processing may be performed external to the at least one node and/or a control device such as a server computer, in cloud etc. The comparison may involve comparing the signal characteristics, which may comprise received signal strength indicator (RSSI), channel state information (CSI), missed wireless messages etc.

Since, the method further comprises determining the relative position of the mobile device with respect to the user’s body based on the comparison, the method provides an improved detection of the position of mobile device with respect to the user body.

In an embodiment, the method may further comprise receiving the first radiofrequency signal at a first time; receiving a change signal indicative of a change of orientation of the user, and further indicative of the changed orientation information of the user; receiving the second radiofrequency signal at the second time after the change of orientation of the user; comparing a signal characteristic of the received first and the second radiofrequency signals received at the first and the second time respectively; determining the relative position of the mobile device based on the comparison.

The method may further comprise receiving the first radiofrequency signal at a first time and the method may further comprise receiving a change signal indicative of a change of orientation of the user, and further indicative of the changed orientation information of the user. The first-time instance is before receiving the change signal. The user may change his/her orientation after the first-time instance, and the change signal may indicate that the change has occurred. For example, the user moves, and the change signal indicates the change. The change signal may further indicate the new changed orientation of the user.

The method may further comprise receiving the second radiofrequency signal at the second time instance after the change of orientation of the user. After the change signal has received, i.e., the user has changed his/her orientation, the second radiofrequency signal is received. The change of orientation is such that either the received first or the second radiofrequency signal is affected by the user body, or one is more affected by the other signal.

Since, the method further may comprise comparing a signal characteristic of the received first and the second radiofrequency signals received at the first and the second time respectively and may further comprise determining the relative position of the mobile device based on the comparison, the method provides a further improved detection of the position of mobile device with respect to the user body.

In an example of one single node, for instance if the single node is located in the ceiling, a first wireless frequency /beam shape for the first radiofrequency signal and a second frequency /beam shape for the second radiofrequency signal may be introduced which interacts less with the body mass than the first wireless signal (e.g., 2.4GHz vs 60GHz). In another example, if the single wireless node in the ceiling is co-located, i.e., located at the same location as the thermopile sensor (which determines the orientation of the user), the difference can be deduced between the first and second radiofrequency signal and the orientation info from the thermopile whether the phone is worn in the front or back pocket. The two frequencies can be selected such that they maximally differ on the degree of their respective interaction with human body mass (water absorption). In an embodiment, the method may further comprise receiving the first radiofrequency signal communicated between a first node and the mobile device; receiving the second radiofrequency signal communicated between a second node and the mobile device; comparing a signal characteristic of the first and the second radiofrequency communicated between the mobile device and the first and the second node respectively; determining the relative position of the mobile device based on the comparison.

The method may further comprise receiving the first radiofrequency signal communicated between a first node and the mobile device. The communication may be in either direction (from the mobile device to the first and/or the second node or from the first and/or the second node to the mobile device) or the direction of communication may change dynamically over time. The first and/or the second node may comprise a single node a set of nodes. The number of nodes may be based on the position of the user relative to the position of the node.

Since, the method may further comprise comparing a signal characteristic of the first and the second radiofrequency communicated between the mobile device and the first and the second node respectively; determining the relative position of the mobile device based on the comparison, the method provides an alternate and further improved detection of the position of mobile device with respect to the user body.

In an embodiment, the at least one node may be static and located at a fixed spatial location. In an example, the nodes may be static and fixed. The fixed and static locations improve accuracy since the signal characteristics are not affected by the movement of the nodes.

In an embodiment, the first and the second node may be located in an environment; and wherein the environment may comprise a first and a second zone; wherein the first and the second zones may be adjacent to each other separated by a virtual vertical plane passing through the user body; wherein the method may comprise: selecting the first node located in the first zone; and selecting the second node located in the second zone.

In an example, the nodes may be located in an environment such as an office, a house, a warehouse, a grocery store, a factory etc. The environment may comprise a first and a second zone. These zones may be virtually defined based on the sensing requirements. These zones may be defined adjacent to each other and separated by a virtual vertical plane passing through the user body. In other words, the user position is the dividing point/line/plane of the environment into the first and the second zone. In an example, the method further comprises receiving a position signal indicative of the position information of the user. Additionally, and/or alternatively, the position information is comprised in the signal comprising orientation information.

The virtual vertical plane may be defined based on the given position information of the user and/or on the orientation information of the user. The environment may be divided into the first and the second zone separated by the virtual vertical plane. For example, the user head is positioned towards the first zone and the back side is positioned towards the second zone or vice versa. In these cases, the first and the second nodes are advantageously selected to be located in the first and the second zones respectively to improve sensing.

In an embodiment, the method may further comprise determining a confidence level of the determination of the relative position of the mobile device; wherein when the confidence level does not exceed a threshold, selecting at least a further node and/or adjusting a characteristic of the communication between the at least one node and the mobile device.

In an example, when the confidence of the determination is not satisfactory, system parameters may be adjusted, for example, another node may be added and/or a characteristic of the communication between the at least one node and the mobile device may be adjusted. For example, transmission power is increased, role of transmitter/receiver is switched, beam shaping is performed etc. Such changes will advantageously improve the confidence level of the determination. The adjustment may include using multiple sensing frequencies/beamshapes in parallel.

In an embodiment, the method may further comprise selecting at least one node based on mounting orientation, beam steering capabilities, hardware capabilities, spatial location, obstructions to the wireless channel between the node and the mobile device.

To further improve performance of the sensing, additional nodes may be added and/or the first and the second node may be selected based on their capabilities and/or location etc. Such selection criteria help in improving sensing performance.

In an embodiment, the method may further comprise controlling the first and/or the second node to transmit a first and/or the second radiofrequency signal respectively; receiving the transmitted first and/or the second radiofrequency signal; determining a motion trail and/or gait of the user based on received first and/or the second radiofrequency signal; determining the orientation of the user based on the motion trail and/or gait. In this advantageous embodiment, the orientation information of the user may be determined using the (same) first and/or the second node e.g., via radiofrequency-based sensing. For example, the radiofrequency signals may be used to determine a motion trail or gait of the user and determine orientation of the user thereof. RF sensing at the breathing- related chest/abdomen movement may be analyzed to deduce the orientation of the user with respect to the wireless node.

In an embodiment, the method may further comprise controlling the first and/or the second node to transmit a first and/or the second radiofrequency signal respectively; receiving the transmitted first and/or the second radiofrequency signal; determining motion or no motion of the user based on the received first and/or the second radiofrequency signal; and wherein when no motion is detected for a predetermined time period; learning body mass of the user based on the effect of the body mass on the received first and/or the second radiofrequency signal.

The method may further comprise learning the body mass of the user when the user is not moving and is static. The learning of the body mass will be helpful is baselining the change in radiofrequency signals. For example, for a user with heavy body mass the expected effect will be more compared to a thin user. In an example, the motion may be classified as major motion.

In an embodiment, the method may further comprise determining the orientation of the user based on thermopile images or microphones. The orientation of the user may advantageously be determined using thermopile and microphones.

In an embodiment, the method may further comprise determining a relative position of another mobile device relative to another user’s body; wherein the other mobile device is carried by the other user; receiving a distance signal indicative of a distance information between the user and the other user; and wherein when the distance does not exceed a threshold, alerting a monitoring system based on the distance information and the position of the mobile device and the other mobile device relative to the user and the other user respectively.

For various health-care related applications, the distance information and contact tracing information are important factors to limit the spread of the viral diseases such as COVID19. The method may further comprise detecting relative positions of the mobile device and another mobile device relative to the user and the other user respectively. The distance information between the user and the other use may be received. The distance estimation may be based on Bluetooth low energy (BLE) or UWB based, and therefore, the position of the phone with respect to the user' s body (front pocket, back pocket, inside handbag) has an unwanted influence on the BLE/UWB-based distance estimation between two users. Therefore, the method advantageously alerts a monitoring system based not only on the distance information but also on the relative position of the mobile device.

In an embodiment, the method may further comprise determining presence or no presence (absence) of a user in an environment based on radiofrequency signal(s) communicated between the mobile device and the at least one node, and/or communicated between the first and the second node; wherein when the presence is detected, determining a contact tracing information of the user based on the radiofrequency signal communicated between the mobile device and the at least one node, and/or communicated between the first and the second node; and wherein when no presence (absence) is detected, determining a contact tracing information of the user based on an application executed on the mobile device.

The method may advantageously provide a hybrid contact tracing information. The contact tracing information may comprise breathing or heartrate detection indicative of COVID infection or other respiratory health issues. When the user is detected via the radiofrequency -based sensing utitlizing the communication between the mobile device and the first and/or the second node, the contact tracing information is determined by the radiofrequency -based sensing utitlizing the communication between the mobile device and the first and/or the second node. When the presence is not detected by the radiofrequencybased sensing, such that e.g., the user is out of sight of the radiorequency-based sensing system, then the contact tracing may be performed via an application executed on the mobile phone.

According to a second aspect, the object is achieved by a control device for determining a relative position of a mobile device relative to a user body using at least one node, wherein the mobile device is carried by the user, wherein the control device comprises a processor arranged for executing at least some of the steps of the method of the first aspect.

According to a third aspect, the object is achieved by a system for determining a relative position of a mobile device relative to a user body using at least one node, wherein the mobile device is carried by the user, wherein the system comprises: a control device according to the second aspect; and at least one node arranged for transmitting and/or receiving a radiofrequency signal. According to a fourth aspect, the object is achieved by a computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method of the first aspect.

It should be understood that the control device, the system and the computer program product may have similar and/or identical embodiments and advantages as the above-mentioned methods.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as additional objects, features and advantages of the disclosed systems, devices and methods will be better understood through the following illustrative and non-limiting detailed description of embodiments of systems, devices and methods, with reference to the appended drawings, in which:

Fig. la and Fig. lb show schematically and exemplary an embodiment of a system for determining a relative position of a mobile device relative to a user body,

Fig. 2a and Fig. 2b show schematically and exemplary another embodiment of a system for determining a relative position of a mobile device relative to a user body,

Fig. 3 shows schematically and exemplary a flowchart illustrating an embodiment of a method for determining a relative position of a mobile device relative to a user body,

Fig. 4 show schematically and exemplary an embodiment of a control device for determining a relative position of a mobile device relative to a user body.

All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the invention, wherein other parts may be omitted or merely suggested.

DETAILED DESCRIPTION OF EMBODIMENTS

Fig. la and Fig. lb show schematically and exemplary an embodiment of a system 100 for determining a relative position of a mobile device 130 relative to a user body 120. The mobile device 130 is carried by the user 120. In this exemplary figure, the user 120 is carrying the mobile device 130 in his back pocket. The mobile device 130 may be a mobile phone, a tablet etc. In this exemplary figure, the mobile device 130 is a mobile phone. The mobile device 130 may be arranged for transmitting and/or receiving radiofrequency signals.

The user 120 is present in an environment 101. An example of environment 101 may be an office, a house, a warehouse, a retail store, a factory etc. The system 100 further comprises at least one node 1 lOa-d. In this exemplary figure, the nodes are represented as lighting devices 1 lOa-d. A lighting device is a device or structure arranged to emit light suitable for illuminating an environment 101, providing or substantially contributing to the illumination on a scale adequate for that purpose. A lighting device comprises at least one light source or lamp, such as an LED-based lamp, gas-discharge lamp or filament bulb, etc., plus any associated support, casing or other such housing.

Each of the lighting device may take any of a variety of forms, e.g., a ceiling mounted luminaire, a wall-mounted luminaire, a wall washer, or a free-standing luminaire (and the luminaires need not necessarily all be of the same type). In the exemplary figure, the lighting devices 1 lOa-d are ceiling luminaire. In an example, the at least one node 1 lOa-d may be static and located at a fixed spatial location in the environment 101. Alternatively, and/or additionally, the at least one node 1 lOa-d may be non-static such as a table lamp, a torch light. Further additionally and/or alternatively, the at least one node 1 lOa-d or the lighting devices such as spotlights may be located at a fixed spatial location, but the light output may be provided a different place. Furthermore, beam forming may be used to provide transmission/reception in a specific direction.

The at least one node 1 lOa-b may be any other type of devices which can be arranged for transmitting and/or receiving a radiofrequency signal. For example, the at least one node 1 lOa-b may be a wall switch, a sensor, a dimmer etc. The at least one node 1 lOa-d may comprise (not shown) a transmitter/receiver or a transceiver arranged for transmitting and/or receiving radiofrequency signals. There may be n number of nodes in the environment 101, wherein the n >=1. The system 100 may comprise both lighting devices and nonlighting devices as at least one node 1 lOa-d.

The at least one node 1 lOa-d and the mobile device 130 may be arranged for transmitted and/or receiving radiofrequency signals between each other. For example, the at least one node 1 lOa-d may be arranged for transmitting the radiofrequency signal and the mobile device 130 may be arranged for receiving the transmitted radiofrequency signal. Alternatively, the mobile device 130 may be arranged for transmitting and the at least one node 1 lOa-d may be arranged for receiving the transmitted radiofrequency signal. The communication may be performed according to a suitable wireless protocol such as Wifi, ZigBee, BLE etc.

The orientation information of the user 120 may be received by the system 100. For example, the orientation information is received at the least one node 1 lOa-d, or at the mobile device 130 or any device external to the at least one node 1 lOa-d or to the mobile device. The orientation information may be received at both the at least one node 1 lOa-d or the mobile device 130. The orientation information may comprise physical orientation of the user, e.g., the direction of head and the back of the user 120. In the exemplary figure Fig. la and lb the user head position is facing towards right, and the back is facing towards left.

In an example, the physical orientation of the user 120 may be determined using radiofrequency-based sensing. In this example, the first and/or the second node may be controlled to transmit a first and/or a second radiofrequency signal respectively. Such a transmission may be according to a wireless communication protocol and further may be arranged for network communication. The transmitted first and/or the second radiofrequency signal are received. The reception may be at the first (provided that the second node has transmitted the radiofrequency signal) or at the second node (provided that the first node has transmitted the radiofrequency signal) or at the mobile device or any other external device (provided that the first and/or the second node has transmitted the radiofrequency signal). In an example, the first or the second node may receive the transmitted signal from them (e.g., using the RADAR principle). The received signal is then processed to determine a motion trail and/or gait of the user 120 based on the received first and/or the second radiofrequency signal. The orientation of the user 120 may be determined based on the motion trail and/or gait.

Additionally, and/or alternatively, the orientation of the user 120 may be determined based on thermopile images or microphones. For example, the facing direction could be detected through the inscribed ellipse for thermopile images, considering head position and the posture (sitting or standing). Microphone array could detect the direction of sound which could be used to derive the orientation of the user.

Any other method to determine orientation of the user 120 which are known in the art is not excluded.

Fig. la exemplary shows that the first 1 lOa-b and the second node 1 lOc-d are located in an environment 101; and wherein the environment comprises a first 105 and a second zone 107. The first 105 and the second zones 107 are adjacent to each other separated by a virtual vertical plane 102 passing through the user body 120. The zones 105, 107 may be virtual zones. The position of the user body 120 may be received, in an example, the position information may be comprised in the signal indicative of the orientation information. Additionally, and/or alternatively the position may be determined using any known method in that art, such as utilizing PIR sensor, thermopile sensor, RF -based sensing. The virtual vertical plane 102 may be based on the position information of the user 120. In an example, the first node 1 lOa-b is selected to be located in the first zone 105 and the second node 1 lOc-d is selected to be located in the second zone 107. The first node 1 lOa-b and the second node 1 lOc-d may be arranged for communicating with the mobile device 130. The communication path is shown via a solid line and a dotted line. In Fig. la the user 120 is wearing the mobile phone 130 in his/her back pocket. The radiofrequency signal between the second node 1 lOc-d and the mobile device 130 is affected by the body mass of the user 120 as indicated by the dotted line, whereas the radiofrequency signal between the first node 1 lOa-b and the mobile device 130 is not affected (or the effect at least does not exceed a threshold, or at least less the effect on the radiofrequency signal between the second node 1 lOc-d and the mobile device 130) as indicated by the solid line. The body mass of the user 120 affects the signal characteristics, such as RSSI, CSI of the radiofrequency signals between the second node 1 lOc-d and the mobile device 130.

A signal characteristic of the first and the second radiofrequency communicated between the mobile device 130 and the first 1 lOa-b and the second node 110c- d respectively may be compared. For example, the RSSI value of the first and the second radiofrequency signals communicated between the mobile device and the first 1 lOa-b and the second node 1 lOc-d respectively are compared. The relative position of the mobile device 130 may be determined based on the comparison. The relative position may be relative to the user body 120 and/or relative to the first 1 lOa-b and/or the second node 1 lOc-d.

Fig. lb exemplary shows another example which is similar to the example of Fig. la. The difference is that user 120 is wearing the mobile phone 130 is the front pocket and the first and the second zones are not disclosed (or not formed). In this example, the radiofrequency signals between the first node 1 lOa-b and the mobile device 130 are affected by the user body 120, as indicated by the dotted line and the radiofrequency signals between the second node 1 lOc-d and the mobile device 130 are not affected (or at least affected not exceeding a threshold).

Fig. 2a and Fig. 2b show schematically and exemplary another embodiment of a system 200 for determining a relative position of a mobile device 130 relative to a user body 120. In this example, the system 200 may comprise only a single node 1 lOa-b or a single set of nodes 1 lOa-b. The determination of the position of the mobile device 130 relative to the user (and/or relative to the node 1 lOa-b) may be determined based on the change of orientation and the reception of radiofrequency signals at two different times, e.g., the first signal before the change of orientation and the second signal after the change of orientation. In this example, the first radiofrequency signal is received at a first time, e.g., as shown exemplary in the Fig. 2a. A change signal indicative of a change of orientation of the user 120, and further indicative of the changed orientation information of the user 120 is received. The changed orientation is shown in Fig. 2b. The user 120 is wearing the mobile phone 130 in the front pocket. In Fig. 2a, based on the orientation of the user 120 and the location of the at least one node 1 lOa-b, the first radio frequency is affected by the user body 120. When the user 120 changes his/her orientation as shown in Fig. 2b, the second radiofrequency signal is not affected by the user body 120 (or at least the effect does not exceed a threshold, or the effect is less than the effect on the first radiofrequency signal). The location of the at least one node 1 lOa-b may remain fixed. The relative position of the mobile device may be determined based on the comparison of a signal characteristic of the received first and the second radiofrequency signals received at the first and the second time respectively.

Fig. 3 shows schematically and exemplary a flowchart illustrating an embodiment of a method 300 for determining a relative position of a mobile device 130 relative to a user body 120. The mobile device 130 is carried by the user 120. The at least one node 1 lOa-d may be arranged for transmitting and/or receiving radiofrequency signals. The mobile device 130 may also be arranged for transmitting and/or receiving radiofrequency signals and arranged for communicating with the at least one node 1 lOa-d. In an example, the communication may only be limited to sniffing or receiving radiofrequency signals.

The method 300 may comprise receiving 310 a signal indicative of an orientation information of the user 120. The orientation information comprises information about the physical orientation of the user 120. The orientation information may be determined using radiofrequency -based sensing, thermopile sensor, microphones or any other known method in the art.

The method 300 may further comprise receiving 320 a first and a second radiofrequency signal communicated between the mobile device 130 and the at least one node 110-ad. The at least one node 1 lOa-d may be selected based on mounting orientation, beam steering capabilities, hardware capabilities, spatial location, obstructions to the wireless channel between the node and the mobile device 130. In an example, when a confidence level of the determination of the relative position of the mobile device does not exceed a threshold, a further node may be selected and/or a characteristic of the communication between the at least one node 1 lOa-d and the mobile device 130 may be adjusted to improve the sensing. The received first or the second radiofrequency signal may be affected by the user body 120. The effect may be based on the location of the at least one node 1 lOa-d, orientation of the user 120 etc.

The method 300 may further comprise comparing 330 a signal characteristic of the received first and the second radiofrequency signals. In an example, the first and/or the second node may be controlled to transmit a first and/or the second radiofrequency signal respectively. The transmitted first and/or the second radiofrequency signal may be received, and motion or no motion of the user 120 based on the received first and/or the second radiofrequency signal. When no motion is detected for a predetermined time period; body mass of the user may be learnt based on the effect of the body mass on the received first and/or the second radiofrequency signal. Different learning method, e.g., machine learning methods, statistical learning, are used for learning.

The method 300 may further comprise determining 340 the relative position of the mobile device 130 with respect to the user’s body 120 based on the comparison. The comparison may be based on comparing signal characteristics of the received first and the second radiofrequency signals, e.g., which one is greater, smaller or the difference of the signals exceeds a threshold etc. In an example, the relative position may be determined if the threshold exceeds the threshold.

In an example, the presence or no presence (absence) of a user in an environment 101 may be determined based on radiofrequency signal communicated between the mobile device 130 and the at least one node 1 lOa-d, and/or communicated between the first and the second node 1 lOa-d. When the presence is detection, a contact tracing information of the user 120 may be determined based on the radiofrequency signal communicated between the mobile device 130 and the at least one node 1 lOa-d, and/or communicated between the first and the second node 1 lOa-d; and when no presence is detected, a contact tracing information of the user 120 may be determined based on an application executed on the mobile device. Contact tracing has become a crucial element to block virus spread (such as covid-19) by recording social contacts. Mobile phone apps, e.g., utilizing Bluetooth Low Energy (BLE) technology are widely deployed to track people within social distances, albeit with mediocre performance. In some cases, office workers temporarily forget to carry their phones on them, or a phone OS could suspend Bluetooth scanning when the app runs in the background; battery power consumption is another issue for current state-of-the-art asset tracking apps as BLE/UWB is constantly scanning; additionally, an in-depth recent study shows extremely disappointing predication accuracy for exposure notifications based on current BLE based contact tracing systems. The above example thereof provides a hybrid contact tracing system, which utilizes at least one node 1 lOa-d, e.g., the lighting loT systems, for contact tracing whenever the user 120 is in the field of view of the lighting loT systems and utilizes the phone' s BLE radio and app when people are out of the view of the lighting loT systems. The contact tracing information may comprise detecting vital sign conditions, e.g., breathing rate, of the user 120.

Fig. 4 show schematically and exemplary another embodiment of a control device 210 for determining a relative position of a mobile device 130 relative to a user body 120. The control device 210 may comprise an input unit 214 and an output unit 215. The input 214 and the output 215 units may be comprised in a transceiver (not shown) arranged for receiving (input unit 214) and transmitting (output unit 215) communication signals, e.g., to and from the first and/or the second nodes 1 lOa-d or to and from the mobile device 130. The communication signal may comprise control instructions to control the first and/or the second nodes 1 lOa-d, for instance control instructions to transmit and/or receive the radiofrequency signals. The control device 210 may further comprise a memory 212 which may be arranged for storing e.g., communication IDs of the first and/or the second node 1 lOa-d. The memory 212 may further be arranged for storing learning algorithm(s). The control device 210 may comprise a processor 213 which may be arranged for controlling the first and the second nodes for transmitting the radiofrequency signals, receiving the transmitted radiofrequency signals, and executing at least few or all steps of the method 300.

The control device 210 may be implemented in a unit separate from the first and/or the second node 1 lOa-d and/or the mobile device 130, such as wall panel, desktop computer terminal, or even a portable terminal such as a laptop, tablet or smartphone. Alternatively, the control device 210 may be incorporated into the same unit as the mobile device 130 and/or the same unit as one of the first or the second node 1 lOa-d. Further, the control device 210 may be implemented in the environment 101 or remote from the environment (e.g. on a server); and the control device 210 may be implemented in a single unit or in the form of distributed functionality distributed amongst multiple separate units (e.g. a distributed server comprising multiple server units at one or more geographical sites, or a distributed control function distributed amongst the first and/or the second node 1 lOa-d or amongst the first and the second nodel lOa-d and the mobile device 130). Furthermore, the control device 210 may be implemented in the form of software stored on a memory (comprising one or more memory devices) and arranged for execution on a processor (comprising one or more processing units), or the control device 210 may be implemented in the form of dedicated hardware circuitry, or configurable or reconfigurable circuitry such as a PGA or FPGA, or any combination of these.

Regarding the various communication involved in implementing the functionality discussed above, to enable the control device 210, for example, to transmit and receive communication signals, these may be implemented in by any suitable wireless means, such as a local (short range) RF network, e.g., a Wi-Fi, ZigBee or Bluetooth network; or any combination of these and/or other means.

The method 300 may be executed by computer program code of a computer program product when the computer program product is run on a processing unit of a computing device, such as the processor 213 of the control device 210.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer or processing unit. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Aspects of the invention may be implemented in a computer program product, which may be a collection of computer program instructions stored on a computer readable storage device which may be executed by a computer. The instructions of the present invention may be in any interpretable or executable code mechanism, including but not limited to scripts, interpretable programs, dynamic link libraries (DLLs) or Java classes. The instructions can be provided as complete executable programs, partial executable programs, as modifications to existing programs (e.g. updates) or extensions for existing programs (e.g. plugins). Moreover, parts of the processing of the present invention may be distributed over multiple computers or processors or even the ‘cloud’.

Storage media suitable for storing computer program instructions include all forms of nonvolatile memory, including but not limited to EPROM, EEPROM and flash memory devices, magnetic disks such as the internal and external hard disk drives, removable disks and CD-ROM disks. The computer program product may be distributed on such a storage medium, or may be offered for download through HTTP, FTP, email or through a server connected to a network such as the Internet.