TECHNICAL FIELD

The present invention relates to mobile electronic devices and methods for directional proximity detection of other mobile electronic user devices communicating wirelessly.

BACKGROUND ART

In recent years, there has been a large interest in developing technology for determining the position of user devices. The most commonly used method is GPS (Global positioning system), in which satellites are used to obtain the position of a mobile device. However, this method is not suitable for indoor use since this causes the building structure to obstruct the GPS signal and makes it unable to reach the mobile device. Furthermore, there is technology developed for indoor positioning using a stationary beacon device that enables positioning by sending a signal that is able to reach the mobile devices in the near surrounding of the beacon and thereby allowing the devices to attain position information.

The present invention is aimed at providing improvements to these technologies and to provide technology for proximity positioning of mobile wireless devices without the need for a separate beacon or a GPS signal.

SUMMARY OF THE INVENTION

With the above description in mind, then, an aspect of the present invention is to provide a mobile electronic device for directional proximity detection of a second mobile electronic device and for presenting in the first mobile electronic device, information regarding the second mobile electronic device and to notify a user of the first mobile electronic device of the second mobile electronic device. The invention also provides a method for such directional proximity detection.

These and further objects are achieved by a first mobile electronic device for directional proximity detection, comprising an antenna array operatively connected to a signal transceiver configured for wireless communication, a control unit comprising software and memory for the wireless communication, wherein the control unit is operatively connected to the signal transceiver, and wherein the control unit is configured to receive, by means of the antenna array and the signal transceiver, at least one wireless signal from a second mobile electronic device, and to calculate spatial information regarding the second mobile electronic device by means of the signal/-s transmitted from the second mobile electronic device to the first mobile electronic device, and to configure a notification for the user of the first mobile electronic device based on at least the spatial information regarding the second mobile electronic device, and to notify the user of the first mobile electronic device of the second mobile electronic device. By providing a mobile electronic device according to the above, a user of the first electronic device is able to be notified of the presence of the second mobile electronic device, e.g. its whereabouts, such as a relative direction and be presented with information regarding the second detected mobile electronic device.

Moreover, the form or type of notification may be graphical, optical (rendering on a display, e.g visors), haptic, tactile (in the form of vibrations), and/or audible (sounds in speaker of a smart phone or in ear phones), which notification may be only information of the identity of the other mobile device or of its relative direction and/or distance in a one-way

communication or the start of a two-way communication between the at least two devices. Hence, this notification may be realized in a very simple and quick way to and for the user of the first mobile electronic device enabling the user to for example choose a desirable action or the device may be predeterminately set to perform a certain desirable action or switch on or off a certain function of the first mobile device. Furthermore, the direction can be

calculated with high accuracy without having to rely on satellites or external antennas i.e.

the spatial information regarding the mobile electronic device can be determined by the first mobile electronic device alone.

According to one aspect of the disclosure, it provides a first mobile electronic device, wherein the first mobile electronic device is a mobile phone. By providing a mobile phone according to the invention, the user of the mobile phone can be notified with spatial information regarding a second mobile electronic device. Furthermore, the user of the mobile phone can easier be informed of the spatial information of other mobile electronic devices and receive information regarding said other mobile electronic devices.

According to one further aspect of the disclosure, it provides a first mobile electronic device, wherein the first mobile electronic device is a visor. By providing visors according to the invention the user of the visors can be notified with spatial information regarding a second mobile electronic device. Furthermore, the user of the mobile phone can easier determine the spatial information of other mobile electronic devices and receive information regarding said other mobile electronic devices by enabling the information to be rendered in the view of the user of the visors.

According to another aspect of the disclosure, the antenna array of the first mobile electronic device faces in substantially the same direction as the user is facing. By providing a mobile electronic device with the antenna array facing in substantially the same direction as the user is facing, other mobile electronic devices that are located in the direction that the user of the first mobile electronic device is facing can be detected by the antenna array. Furthermore, the accuracy of the calculation of the spatial information of the other mobile electronic devices is improved and the notifications can be made more accurate accordingly.

According to yet another aspect of the disclosure, a first mobile electronic device is provided, wherein the antenna array is arranged to receive signals originating from the second mobile electronic device in the front view of the user. By providing a mobile electronic device in which the antenna array is arranged to receive signals originating from the second mobile electronic device in the front view of the user, other mobile electronic devices that are located in the front view of the first mobile electronic device can be detected.

According to a further aspect of the disclosure, a first mobile electronic device is provided, wherein the antenna array faces a direction being substantially perpendicular to the direction the user is facing. By providing an antenna array that faces in direction perpendicular to the direction the user is facing, the antenna array can detect and notify the user of the other mobile electronic devices that are located to either side of the user.

According to yet another aspect of the disclosure, a first mobile electronic device is provided, wherein the first mobile electronic device is a wireless hands-free device. By providing a wireless hands-free device according to the invention, the user can be notified of detected mobile electronic devices without having to have his mobile electronic device, such as a mobile phone at hand, e.g. by not having to hold the mobile phone and not having to fumble it out of his bag or briefcase when notified. The wireless hands-free device may be adapted to, independent of a mobile electronic device, retrieve information regarding the detected mobile electronic device and notify the user of the wireless hands-free device. The wireless hands-free device may also transmit the information, i.e. a unique ID of a detected mobile electronic device, to the mobile electronic device which is connected to the wireless hands-free device in order for the mobile electronic device to retrieve the information regarding the detected mobile electronic device.

The above and further objects are also achieved by a method for directional proximity detection, comprising at least one mobile electronic device adapted to communicate wirelessly, the method comprises receiving, by means of a first mobile electronic device, at least one wireless signal from a second mobile electronic device by means of an antenna array on the first mobile electronic device; and calculating, by means of the first mobile electronic device, spatial information regarding the second mobile electronic device by means of the signal/-s transmitted from the second mobile electronic device to the first mobile electronic device; and configuring a notification for the user of the first mobile electronic device based on at least the spatial information regarding the second mobile electronic device; and notifying the user of the first mobile electronic device of the second mobile electronic device. By providing a mobile electronic device according to the above, a user of the first electronic device is able to be notified of the presence of the second mobile electronic device, e.g. its whereabouts, such as a relative direction and be presented with information regarding the second detected mobile electronic device. Moreover, the form or type of notification may be graphical, optical (rendering on a display, e.g visors), haptic, tactile (in the form of vibrations), and/or audible (sounds in speaker of a smart phone or in ear phones), which notification may be only information of the identity of the other mobile device or of its relative direction and/or distance in a one-way communication or the start of a two-way communication between the at least two devices. Hence, this notification may be realized in a very simple and quick way to and for the user of the first mobile electronic device enabling the user to for example choose a desirable action or the device may be predeterminately set to perform a certain desirable action or switch on or off a certain function of the first mobile device. Furthermore, the direction can be calculated with high accuracy without having to rely on satellites or external antennas i.e. the spatial information regarding the mobile electronic device can be determined by the first mobile electronic device alone.

The above are also achieved by below aspects of the invention, and further objects and features will appear from the following detailed description of aspects of the invention.

According to another aspect of the disclosure, it provides a method for directional proximity detection, wherein the first mobile electronic device determines a unique ID for the second mobile electronic device by means of the signal/-s transmitted from the second mobile electronic device to the first mobile electronic device. By providing a method for determining a unique ID for the second mobile electronic device, the first mobile electronic device can identify and retrieve information regarding said second mobile electronic device. Furthermore, the spatial information that is calculated can be coupled to corresponding unique ID to ensure correct notification of information to the user of the first mobile electronic device.

According to a further aspect of the disclosure, it provides a method for directional proximity detection, wherein the first mobile electronic device uses the unique ID for the second mobile electronic device to retrieve information associated with the user of the second mobile electronic device. By providing a method for determining a unique ID, e.g. a BTMAC ID or other unique identifier, information coupled to said unique ID can be retrieved from a server by the first mobile electronic device and notified to a user of the first mobile electronic device. The information that is stored in the server in connection to the unique ID can be altered by the user of the device with corresponding unique ID such that that user can choose what information that is retrievable by other mobile electronic devices.

According to yet another aspect of the disclosure, it provides a method for directional proximity detection, wherein the first mobile electronic device notifies the user of the first mobile electronic device of the identity information associated with the second mobile electronic device by the aid of the spatial information associated with the second mobile electronic device. By providing a method for using the spatial information to notify the user of the identity information regarding the user of the second mobile electronic device, the notification can be made more precise. For instance, if the second mobile electronic device is detected at a certain direction in relation to the first mobile electronic device, the notification comprising identity information can be presented to the user of the first mobile electronic device correspondingly to alert the user of the first mobile electronic device of both the direction and the identity information regarding the second mobile electronic device simultaneously.

According to yet another aspect of the disclosure, it provides a method for directional proximity detection, wherein the first mobile electronic device notifies the user of the first mobile electronic device by means of rendering an overlay at a position on a display, which position is determined by using the spatial information associated with the second mobile electronic device. By providing a method for rendering a visual overlay which position is determined by using the spatial information associated with the second mobile electronic device, information can be accurately presented to the user of the first mobile electronic device. Information can be rendered as an overlay in a position corresponding to the position of the second mobile electronic device as viewed through the first mobile electronic device e.g. as viewed through a pair of augmented reality visors.

According to a further aspect of the disclosure, it provides a method for directional proximity detection, wherein the first mobile electronic device notifies the user of the first mobile electronic device by means of generating an audio signal, which audio signal is determined by using the spatial and/or identity information associated with the second mobile electronic device. By providing a method for using an audio signal as notification to a user of a first mobile electronic device, an effective way of notifying the user of the spatial information such as the relative direction and identity of the user carrying a second mobile electronic device. The audio signal can be sounding from a certain direction corresponding to relative position of the second mobile electronic device to indicate where the second mobile electronic device is located to the user of the first mobile electronic device.

According to a further aspect of the disclosure, it provides a method for directional proximity detection, wherein the first mobile electronic device notifies the user of the first mobile electronic device by means of controlling an audio stream by using the spatial information associated with the second mobile electronic device. By providing a method for controlling an audio stream by using the spatial information associated with the second mobile electronic device can e.g. the audio stream from an ongoing conversation with a user of the second mobile electronic device be controlled such that the audio is generated in the first mobile electronic device corresponding to the position of the second mobile electronic device. Thereby can the user of the first mobile electronic device in a simple way locate the direction to the second mobile electronic device by listening to which direction the audio, generated by the speaker system associated with the first mobile electronic device, is coming from.

According to another aspect of the disclosure, it provides a method for directional proximity detection, wherein the first mobile electronic device notifies the user of the first mobile electronic device by means of generating a tactile signal, which tactile signal is determined by using the spatial and/or identity information associated with the second mobile electronic device. By providing method for using a tactile signal as a notification to the user of the first mobile electronic device can be notified by only being in contact with the first mobile electronic device. The tactile signals may be varied depending on the spatial information, e.g. the relative position of the second mobile electronic device and the identity of the user of the second mobile electronic device, e.g. emit a signal on one side of the first mobile electronic device that increases in strength as the second mobile electronic device approaches the first mobile electronic device and thereby giving the user of the first electronic device information regarding both the relative direction and the relative distance to the second mobile electronic device.

According to a further aspect of the disclosure, it provides a method for directional proximity detection according to any preceding claim, wherein the first mobile electronic device transmits the spatial information to the second mobile electronic device. By providing a method for transmitting the spatial information calculated by the first mobile electronic device regarding the second mobile electronic device to the second mobile electronic device, the spatial information can be used by the second mobile electronic device to determine its own location in relation to the first mobile electronic device.

According to a yet another aspect of the disclosure, it provides a method for directional proximity detection, wherein the first mobile electronic device notifies the user of the first mobile electronic device of the spatial information comprising the direction to the second mobile electronic device in relation to the first mobile electronic device. By providing a method for notifying the user of the first mobile electronic device of the direction of the second mobile electronic device, i.e. the relative direction compared to the orientation of the first mobile electronic device, a way of making a user of the first mobile electronic device aware of the relative direction of the second mobile electronic device is provided.

According to a yet another aspect of the disclosure, it provides a method for directional proximity detection, wherein the first mobile electronic device uses motion sensors to

compensate for movements and rotations of the antenna array during the receiving and/or transmitting of at least one wireless signal. To further enhance the precision of the direction detection, rotations and other movements of the antenna array during the transmitting and/or receiving of a measurement signal package can be compensated for by using accelerometer, gyro and/or magnetometer to detect such movements. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates a mobile electronic device where the present invention can be

implemented.

Figure 2 illustrates a mobile electronic device where the present invention can be

implemented.

Figure 3 illustrates an exemplary application where the present invention is implemented.

Figure 4 illustrates a flowchart of a method according to the present invention for directional proximity detection of mobile electronic devices by a mobile electronic device.

Figure 5 illustrates an exemplary application of the present invention where a first, tracking mobile electronic device in the shape of augmented reality visors detects a second, tracked mobile electronic device.

Figure 6 illustrates an exemplary application of the invention where a first, tracking mobile electronic device in the shape of a pair of augmented reality visors receives signal/-s from a second, tracked mobile electronic device in the shape of a mobile phone.

It should be added that the following description of the embodiments is for illustration purposes only and should not be interpreted as limiting the disclosure exclusively to these embodiments/aspects.

DETAILED DESCRIPTION

Embodiments of the present invention will be described more fully hereinafter with

reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be

construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference signs refer to like elements throughout.

Figure 1 illustrates a mobile electronic device 1. Examples of such devices are mobile phones, glasses with integrated displays, augmented reality visors, touch pads, a wireless handsfree device, e.g. a Bluetooth headset or a "lifelogger" being able to take photos for documenting an every-day life for a user etc.

The first i.e. the tracking mobile electronic device 1 comprises an antenna array 10 according to the invention which includes a plurality of antenna elements, preferably less than 10 elements, ideally 5-7 elements which are separated with a predetermined distance, each being able to receive and send a signal e.g. a Bluetooth signal, a low energy Bluetooth signal, a WLAN signal etc. The antenna array 10 is operatively connected to a signal transceiver 13 to enable wireless communication i.e. receive and send e.g. a Bluetooth signal, a WLAN signal etc. The antenna array 10 is adapted to receive signals from and/or transmit signals to at least one second mobile electronic device 2 that is to be tracked by the first mobile electronic device 1 or vice versa, the first mobile electronic device 1 is instead tracked by the second mobile electronic device 2. The antenna array 10 may also transmit and/or receive a switched signal, i.e. the active antenna segments are switched at predetermined time intervals. The second, tracked mobile electronic device 2 comprises at least a regular wireless communication antenna and/or an antenna array 10 capable of transmitting and/or receiving signals that is receivable by the antenna array 10 in the first, tracking mobile electronic device 1. The first mobile electronic 1 device may also comprise a regular wireless communication antenna.

The characteristics and contents of the signals that is received by the different antenna elements in the antenna array 10 is analyzed by a control unit 12 which further comprises software and a memory 18. The control unit 12 is operatively connected to the signal transceiver 13. The control unit 12 is adapted to calculate spatial information regarding the second, tracked mobile electronic device 2. The spatial information may comprise the angle between the tracking mobile electronic device 1 and the tracked mobile electronic device 2. The calculation of the relative angle is based on analyzing received l&Q samples when a known signal is sequentially coupled to multiple transmit or receive antennas, which is a technique known in the art and will not be described in further detail.

Furthermore, the angle that is detected can be combined with a relative distance between the first mobile electronic device 1 and the second mobile electronic device 2 that is determined by measuring the strength of the signal from the second mobile electronic device 2 when received by the first mobile electronic device 1. The determined distance can be used to display a distance to said tracked mobile electronic device 2 in said tracking mobile electronic device 1 or to determine the size of the displayed information regarding the tracked mobile electronic device 2.

Moreover, the relative distance between the first mobile electronic device 1 and the second mobile electronic device 2 may be determined by measuring the time difference of arrival (TDOA) of the signal from the second mobile electronic device 2 when received by the first mobile electronic device 1. The determined distance can be used to display a distance to said tracked mobile electronic device 2 in said tracking mobile electronic device 1 or to determine the size of the displayed information regarding the tracked mobile electronic device 2.

Furthermore, the relative distance between the first mobile electronic device 1 and the second mobile electronic device 2 may be determined by measuring the round trip time (RTT) of the signal from the second mobile electronic device 2 when received by the first mobile electronic device 1. The determined distance can be used to display a distance to said tracked mobile electronic device 2 in said tracking mobile electronic device 1 or to determine the size of the displayed information regarding the tracked mobile electronic device 2.

The tracking mobile electronic device 1 is further adapted to notify the user of the tracking mobile electronic device 1 of the presence of at least one second mobile electronic device 2 in a predetermined way.

A first way of notifying a user of a tracking mobile electronic device 1 that another mobile electronic device 2 is approaching is to use tactile signaling, i.e. vibrations that are provided by at least one vibration unit 16. The vibrations can occur when an approaching mobile electronic device 2 is detected. The vibrations can be directional, i.e. when another mobile electronic device 2 approach from a certain direction, the first, tracking mobile electronic device 1 vibrates on the corresponding side facing the approaching, tracked mobile electronic device 2 to indicate the approach direction. The vibrations can also occur with different frequencies and sequences depending on if the e.g. the approaching mobile electronic device is a known device or not.

A second way of notifying a user of a tracking mobile electronic device 1 that another mobile electronic device 2 is approaching is to use sound signals that are provided by at least one speaker 14. The sound signals occur when an approaching device is detected. The sound signals can be directional, i.e. when another mobile electronic device approaches from a certain direction, the first, tracking mobile electronic device sounds a signal from a speaker on the corresponding side facing the approaching, tracked mobile electronic device. The sound signal can further be different depending on the approaching, tracked mobile electronic device 2, i.e. it can read out information regarding the approaching mobile electronic device 2 or the user of said approaching device. The sound signals may be in the form of an audio signal or several audio signals or an audio stream. The method may control an audio stream by using the spatial information associated with the second mobile electronic device. Hence, the audio stream from an ongoing conversation with the user of a second mobile electronic device 2 can be controlled such that the audio is generated in the first mobile electronic device 1 corresponding to the position of the second mobile electronic device 2. Thereby can the user of the first mobile electronic device 1 in a simple way locate the direction to the second mobile electronic device 2 by listening to which direction the audio, generated by the speaker system associated with the first mobile electronic device 1, is coming from i.e. similar to a surround sound system.

A third way of notifying a user of a tracking mobile electronic device 1 that another mobile electronic device 2 is approaching or is in the vicinity is to use visual notifications that are displayed/rendered on a display 15 of the tracking mobile electronic device 1. The visual notifications occur when an approaching device 2 or a device 2 in the vicinity is tracked. The visual notifications can comprise a message containing identification information regarding the tracked mobile electronic device 2 or the user of the tracked mobile electronic device 2. In a preferred embodiment, visual identification information regarding the tracked mobile electronic device 2 is rendered as a overlay in a position on a display 15 corresponding to the position that the tracked mobile device 2 has when viewed by a user through the tracking mobile electronic device 1 e.g. as viewed through a pair of augmented reality visors 1. The relative angle between the first, tracking mobile electronic device 1 and the second, tracked mobile electronic device 2 that is calculated by the control unit 12 with use of the signals transmitted by the tracked mobile electronic device 2 is used to determine where to render the information regarding the tracked mobile electronic device 2. To further enhance the precision of the rendering position and to ensure that the rendered information in the users field of view follows the position of the tracked mobile electronic device 2 when the relative angle between the two changes, a gyroscope, a

accelerometer and/or a magnetometer can be applied to compensate the position of the rendering for movements of the tracking mobile electronic device 1. Furthermore, to achieve a high refresh rate of the rendering of the information regarding the tracked device 2, the position can be recalculated using the signals transmitted from the tracked device 2 and compensated according to the above. To further enhance the precision of the direction detection, rotations and other movements of the antenna array 10 during the transmitting and/or receiving of a measurement signal package can be compensated for by using motion sensors 20 e.g.

accelerometer, gyro and/or magnetometer to detect such movements. Performing these compensations is a known art and will not be further discussed in this disclosure.

Figure 2 shows a mobile electronic device 1 in the shape of a pair of augmented reality visors 1, comprising means 15 for displaying information in the field of view of the user. The visors further comprises at least one antenna array 10 that is arranged in the frame of the visors 1 or integrated into the glass. For tracking mobile electronic devices that are located in front of the tracking augmented reality visors 1, the antenna array 10 is mounted on the part of the frame/glass facing forwards, e.g. essentially perpendicular to the direction the visors are facing. For tracking of mobile electronic devices that are located to the side of the tracking visors 1, further antenna arrays 17 can be arranged on the sides of the frame i.e. on the sidepieces of the visors.

Figure 3 shows three mobile electronic devices in the form of augmented reality visors. The tracking device 1 receives signals from the tracked devices 2 enabling the tracking device 1 to locate the tracked devices 2. The signals further comprise a respective unique ID depending on the standard used by the associated devices, e.g. an unit, Mac or device ID for the tracked devices, in this case a BTMAC ID but this can be any type of unique network identifier. The units IDs are then sent to a server 11 to retrieve public information that is connected to the respective unit ID, by performing a lookup in a web registry, and then a public source, e.g. the Facebook page of the user that is connected to the unit ID. The web registry maps unit IDS to public IDs, e.g. the

Facebook IDs of the users of the devices. The control unit 12 can then determine where to render the retrieved information in the display 15 of the visors 1 so that it becomes an overlay which is attached to the corresponding tracked mobile electronic device 2. Face detection can further be used to improve the accuracy of the rendering, i.e. to ensure that the positioning of the rendered information does not obstruct the view of the user of the tracked device 2.

Figure 4 shows a flowchart of the method for notifying a user of a tracking mobile electronic device 1 that a tracked mobile electronic device 2 is detected. The first step SI of the method is to receive at least one signal from a second mobile electronic device 2 by means of an antenna array 10 on a first, tracking mobile electronic device 1.

The second step S2 of the method is to calculate, by means of a control unit 12 in the first mobile electronic device 1, spatial information regarding the second mobile electronic device 2 by means of the signal/-s transmitted from the second mobile electronic device 2 to the first mobile electronic device 1. The signal/-s that is received from the second mobile electronic device 2 can comprise a unique unit ID. The control unit 12 registers unit IDs and makes sure that the unit IDs are connected to corresponding spatial information. The control unit 12 is adapted to calculate spatial information that comprises the angle and/or distance to the tracked, second mobile electronic device 2.

Step three, S3, comprises configuring a notification for the user of the first mobile electronic device 1 based on at least the spatial information regarding the second mobile electronic device 2. The control unit 12 can further be adapted to use the spatial information in combination with information gathered from a server 11 using the unit ID of the second mobile electronic device 2. The information that is gathered from the server is registered by the user of the second mobile electronic device 2 in advance; alternatively the information or some of the information may also be gathered automatically by the server 11. The control unit 12 combines the information gathered from the server 11 with the corresponding spatial information and uses it to notify the user of the first, tracking mobile electronic device 1 that a second, tracked mobile electronic device 2 is detected or is in the vicinity. The notification can comprise a directional vibration, a directional sound signal that can also be comprising information regarding the second, tracked mobile electronic device 2, or a visual, rendered overlay in a position on a display 15 on the first device 1 corresponding to the position of the second, tracked mobile electronic device 2 as seen through the first, tracking mobile electronic device 1 e.g. as seen through a pair of visors 1. The notification can also be a combination of these alternatives.

Step four, S4, comprises notifying the user of the first, tracking mobile electronic device 1 of the second, tracked mobile electronic device 2 in a predetermined way. The predetermined way can be any of the alternatives above or a combination of these.

Figure 5 shows an exemplary application of the present invention where a first, tracking mobile electronic device 1 in the form of augmented reality visors 1 detects a second, tracked mobile electronic device 2. The signals from the tracked device 2 are received by the antenna array 10 and the spatial information is calculated. The unit ID is used to retrieve the corresponding user information from the server 11 and the control unit 12 in the tracking device 1 renders the information on the position calculated by the control unit 12 in the tracking device 1 using at least the spatial information. The process is repeated to ensure that the information is rendered in the correct position and to ensure that the information regarding the tracked device 2 is kept up to date. Face recognition, a gyroscope and accelerometers can be applied to improve the accuracy of the rendering. The visors can also be connected to another electronic device e.g. a wireless handsfree device via Bluetooth and thereby allow the connected device to be active in the notification of the user e.g. by producing a sound signal or vibration.

Figure 6 shows another exemplary application of the invention where a first, tracking mobile electronic device 1 in the shape of a pair of augmented reality visors 1 receives signal/-s from a second, tracked mobile electronic device 2 in the shape of a mobile phone 2. The tracking mobile electronic device 1 can, by analyzing the signals e.g. by calculating the Angle of Arrival, determine the angle in the horizontal plane between the first tracking mobile electronic device 1 and the tracked mobile electronic device 2. The technique of calculating Angle of Arrival is known in the art and will not be described in further detail. The array can also be positioned in another direction, e.g. vertically, to provide an angle in the vertical plane that can be combined with the angle in the horizontal plane to provide a three dimensional calculation of the position of the second, tracked mobile device 2 by the first, tracking mobile electronic device 1.