Device Ranging

Abstract

The present invention relates to a method, and associated systems and devices, for providing distance measurement between a first electronic device and a second electronic device, where the devices are connected and configured to communicate using wireless communication means. The method comprises: - detecting movement of the second device; - transmitting a request signal from the second device to the first device; - receiving, at a first device, the request signal and generating a response signal using a first transducer; - receiving a response signal at a second device; - calculating the distance between the devices based on the response signals; Includes.

Description

[Technical Field]

[0001] The present invention is based on calculating the absolute distance between the primary and secondary electron devices. [Background technology]

[0002] There are situations in which it may be useful for a user of an electronic device to know the distance between two potentially mobile electronic devices at regular, configurable intervals or triggered by other mechanisms. The distance measurement may be used to initiate any number of different actions on one or both devices when the devices are at a preconfigured distance. Alternatively, knowing the distance between the devices may prevent or allow the devices from cooperating or communicating based on the distance between the devices.

[0003] Several different solutions have been proposed that describe how two or more devices can determine their relative position and orientation based on ultrasonic signals transmitted between them. Each device has one speaker and two microphones, allowing for 2D positioning, such as on a tabletop. Wireless communication (Bluetooth or WiFi) can be used to add communication capacity between devices and increase the possibilities for device synchronization. US2021 / 0400417 describes an audio system that allows different devices to determine their relative position and orientation.

[0004] EP1758308A1 relates to a system that provides distance measurement between devices in the system when activated by an acceleration sensor, and the distance measurement may use a phase difference based sound sensor, which is used to combine a synchronization signal with the sound. Summary of the Invention [Means for solving the problem]

[0005] While several methods for measuring distance and / or relative position are known, they typically require active sensors that continuously listen to nearby devices as new devices may come into the vicinity or as devices move, changing their relative positions. This consumes power, and it is an object of the present invention to provide a solution that minimizes the power consumption of the devices.

[0006] The objects of the invention are achieved as set forth in the appended claims.

[0007] Thus, the present invention provides a power efficient solution as it only needs to detect the distance and possibly the relative position between the devices when they are woken up by an event related to a change in distance, for example by using an inertial measurement unit or similar to register that one of the devices has moved.

[0008] The invention will now be described in more detail with reference to the accompanying drawings, which illustrate the invention by way of example. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 shows two devices according to the invention. [Figure 2] FIG. 2 shows the sequence of the method according to the invention. [Figure 3] FIG. 1 illustrates a system according to the present invention, including a computer and two mobile devices. DETAILED DESCRIPTION OF THE INVENTION

[0010] 1 shows a first device 1 and a second device 2, both configured to communicate using WiFi or a similar system. The second device 2 also includes a low-power sensor 6, such as an inertial measurement unit (IMU), connected to a main processor 5. In the figure, the second device 2 is a mobile phone that also includes microphones 4a, 4b and a speaker 7.

[0011] If the sensor 6 detects a movement indicating the need for a distance update, the processor of the second device 2 sends a request signal using the WiFi connection. Initially, the movement may include key activations for system initialization or pressing a computer mouse or touchpad, but at later stages, the movement primarily includes activities that presumably change the relative position and orientation between the devices. The request signal is received by the processor 8 in the first device 1, which instructs the transducer 3 to transmit a response signal 3a that is received by the second device 2. According to a preferred embodiment of the present invention, the response signal is an acoustic signal, preferably an ultrasonic signal, that is received by at least one microphone 4a, 4b in the first device. If the second device is equipped with two microphones, the angle of the incoming signal can be analyzed to calculate the distance D, and possibly the relative position, of the devices, as described, for example, in NO20221246.

[0012] A WiFi connection may be established if the distance is within a predetermined range, e.g., within a predetermined zone around the first device, and / or if other requirements are met, such as protocol type, signal strength, etc. For example, a computer mouse may request pairing using Bluetooth if the distance, location, and orientation are within a predetermined range, e.g., giving preference to a mouse configured for right-handed use that is located on the right side and within a practical distance from the computer.

[0013] Referring to FIG. 2, the sequence of operations may be as follows: 21 A low power consumption sensor 6, such as an IMU, is used to detect movement in the second device. 22 The second device 2 transmits a request signal using a wireless communication system such as WiFi, Bluetooth, or the like. 23 At the first device 1, the request signal is received. 24. From the first device, generate a response signal, preferably an acoustic signal in the ultrasonic range. 25 At the second device, the response signal is received and the distance between the devices is calculated.

[0014] Once the distance is calculated, the system can wait for another motion to be detected or continue to repeat the process as long as motion is registered. Distance information can be distributed within the system, for example using WiFi, to allow the first device to adapt to the distance between devices.

[0015] If the direction between the devices is known or has already been measured, for example as disclosed, and the IMU is able to measure the direction of movement, the process can be initiated only when the movement is directional between the devices and therefore the distance changes.

[0016] FIG. 3 illustrates a situation in which the first device is a computer and there are two second devices 33a, 33b, each of which includes circuitry 36a, 36b that detects movement and transmits a request signal to the first device 31, which responds by transmitting a response signal 34a, 34b. The request signal preferably includes an identification code so that the first device can adapt communication between the devices to distance, and possibly orientation and relative position. It is also possible to have two first devices in a system. If there are several first devices whose relative positions are known or measured, a mobile device can select a first device by registering the mobile device's movement or orientation, as described, for example, in NO20221243. As an example, the first device may be a computer associated with a videoconferencing system, allowing secondary devices to join the system and submit files, possibly with limited access, creating an ad hoc network.

[0017] As described above, there are several methods for measuring the distance between electronic devices. Ultrasonic transponding is one effective technique that allows an electronic device to measure the distance between itself and another electronic device. In this case, both electronic devices require at least one ultrasonic transducer to transmit an ultrasonic signal (e.g., a chirp) toward the other electronic device at time T0, and at least one ultrasonic transducer in the other device to receive the ultrasonic signal by receiving the transmitted signal at time T1. When the second device receives the ultrasonic signal from the first device, it transmits the ultrasonic signal back to the first device using the same or another ultrasonic transducer. The first device receives the ultrasonic response signal at T2 with the same or another ultrasonic transducer and calculates the distance between the devices based on the speed of sound and the elapsed time since transmitting the first ultrasonic signal (i.e., T2 - T0). The second device delays its response with its own ultrasonic signal by a predefined delay D known to both the first and second devices, allowing the second device to adjust its distance measurement using the elapsed time T2 - D - T0 when calculating the distance as described above.

[0018] In most cases, this is advantageous whether the first and second devices are capable of simultaneous one-way or two-way communication using another wireless technology such as Bluetooth or WiFi. If no other viable option exists, this communication channel can be replaced with a low-bit-rate acoustic communication channel based on modulation of acoustic waves.

[0019] One alternative to transponding is to synchronize the clocks of the first and second devices within the required specifications to provide distance measurements with the required accuracy. If the devices are part of the same data network, synchronization protocols such as Network Time Protocol or Precision Time Protocol can be used. One clear advantage of relying on clock synchronization is that the second device does not need to send an ultrasonic signal back to the first device. The elapsed time T1-T0 between the first device transmitting the ultrasonic signal to the second device and the second device receiving it can be used by the second device to calculate the distance between the two devices. If the clocks of both devices are synchronized, distance measurements can be made by the first device transmitting an ultrasonic signal at least once at a predefined time. The ultrasonic signal can be transmitted only once or at predefined intervals known to both devices, allowing the second device to calculate the distance from a) the elapsed time and b) the speed of sound. It is also possible for the first device to transmit a timestamp to the second device of the time the ultrasonic signal is transmitted, or the time transmitted on a separate out-of-band data channel. If an out-of-band channel is not available, in-band ultrasonic modulation techniques can also be used to transmit information.

[0020] A third option is to simultaneously send a radio signal and an ultrasonic signal and measure the time difference when these signals are received. Radio signals travel at the speed of light. Another possible technique is to simultaneously send a wireless signal (e.g., WiFi, Bluetooth, Zigby, etc.) with an ultrasonic signal and measure the time difference when the radio signal and the ultrasonic signal reach the second device. This time difference and the speed of sound can be used to calculate the distance between the two devices.

[0021] Another possible technique is to exploit the difference in the speed of sound at different frequencies, as described, for example, at https: / / pages.mtu.edu / ~suits / SpeedofSound.html. By using an acoustic signal that contains both infrasonic and ultrasonic components, reception of the different components of the signal using a sampling rate that can detect the difference in the speed of sound can be used to estimate the distance between a first device and a second device based on the known speed difference in air.

[0022] A fifth option is to use the signal amplitude of the received signal as an approximation of the distance to the other device based on empirical data. This only works if the ultrasound transducer of the first device transmitting the output signal is not obscured or encased by one or more objects and is transmitting the output signal in the same space as the second device. Combining the amplitude information with other information (e.g., device orientation) or the techniques described above can provide additional information. At the same time, empirical data can also be used to allow the second device to recognize that the first device is obscured or encased by one or more objects, potentially reducing signal power and range. A wide range of modern electronic devices have numerous sensors, including 6DoF inertial measurement unit (IMU) sensors. These sensors can be used to detect the device's orientation, which can then be used to select an ideal set of ultrasound transceivers (e.g., microphones facing the first device) for transmitting and receiving ultrasound signals to and from the first device.

[0023] If one or both devices are moving away from the other, the distance measurements will change as the devices move away from each other and may therefore be less accurate or already out of date by the time the measurements are made. One way to adjust the distance measurements is to include Doppler measurements of the incoming ultrasound signals and adjust the calculated distance measurements by a movement offset predicted by the Doppler information in the received ultrasound signals, as described in NO20221244.

[0024] As mentioned above, continuous distance measurements using acoustic signals, and in some cases radio signals, may be impractical due to power constraints on electronic devices or interference with frequency bands in use. In some situations, it may be necessary to duty-cycle distance measurements at fixed or predefined intervals. Devices may also agree to use pseudo-random intervals based on an agreed-upon random number seed for the intervals used for distance measurements to reduce the possibility of interference from other devices making measurements in the same area.

[0025] The object of the present invention can be achieved by using an IMU sensor to trigger distance measurements only when absolutely necessary, and the power consumption of an IMU sensor is generally lower than that of an acoustic sensor.

[0026] Thus, according to a preferred embodiment of the present invention, a new set of distance measurements can be triggered by an IMU sensor in either the first device or the second device detecting significant lateral movement after the devices have moved or while they are still moving, since the last distance measurement may be invalid. Distance measurements must continue while at least one of the devices is still moving. When the IMU sensor indicates a cessation of motion, the distance to the device is measured again and distance measurements can be stopped. If the devices are mounted on a moving vehicle or object (e.g., a train, a ship, etc.), it may be necessary to compare IMU sensor data between the two devices to determine whether they are moving relative to each other. If so, a new set of distance measurements is required.

[0027] Another mechanism for preventing unnecessary distance measurements is for a first device to transmit periodic wireless beacons within a limited range that can be detected by a second device if it is close enough. Thus, if the second device cannot hear the beacon from the first device, distance measurements are unnecessary. Similarly, the first device can establish a geofencing zone around the device, for example, using GPS technology, and the second device can use its own GPS device, if available, to limit distance measurements to situations that are within the geofencing zone established by the first device.

[0028] Another possible solution when the first device is stationary and the second device is mobile is to use low-power environmental sensors (e.g., temperature sensors, humidity, air quality, barometric pressure, etc.) on the second device, if available, to determine when the second device may be in close proximity to the first device. The first and second devices exchange historical sensor data whenever a suitable communication channel is available, and when the current environment indicates, based on the historical data or a DNN based on the historical data, that the second device is not in the same environment as the first device, the second device can enter a power-saving mode. The system may be able to detect the presence of nearby objects or people and may limit sensor activity based on the type of activity measured.

[0029] Another solution, if the device's power constraints allow it, is to transmit a distinguishable ultrasonic signal from the first device. This is possible if the first device is a stationary device connected to a power source. The idea is that the second device listens for the ultrasonic signal transmitted by the first device and, if that signal is detected, begins the distance measurement process.

[0030] If one of the ultrasound signals emitted by the first device is a sine wave or set of sine waves while the second device begins to move away from the first device, the second device can use the change in frequency of the sine wave to estimate both the velocity and, based on integration, the change in distance as the second device moves away from the first device. These estimates can be compared to estimates of device velocity and corresponding distance traveled from IMU sensor data. Estimates from both data sources can provide more accurate information about the path of the second device relative to the first device, as described, for example, in NO20221244.

[0031] In some situations where one device is mobile (e.g., carried, worn, attached to a person or animal, etc.) and the other device is stationary, the current relative velocity of the mobile device with respect to the other device and changes in the relative distance between the devices can be used to infer the user's intentions regarding relative movement. By combining distance measurements with the estimated instantaneous velocity of the mobile device based on IMU data and the Doppler effect in the emitted sinusoidal signal, the mobile device can determine the user's heading and, based thereon, what action to take.

[0032] In situations where two or more first devices exist within a limited area and a second device can simultaneously receive ultrasonic signals from multiple first devices, the ultrasonic signals emitted from each first device should preferably be unique. Using unique signals allows the second device to easily detect when it is within range of the correct first device. However, ultrasonic frequency bands are limited, making it impractical to create unique signals for each first device that are unaffected by interference from signals emitted by other first devices. It is possible to create a fixed number of unique signals by using known multiplexing techniques, such as FDM (frequency division multiplexing), TDM (time division multiplexing), CDM (code division multiplexing), and SDM (spatial division multiplexing). It is possible to reserve a frequency band with a fixed number of different frequencies, with each first device transmitting a signal at an assigned frequency. Assuming that the available frequencies need to be separated in frequency (e.g., 150 Hz) to avoid false frequency detection due to the Doppler effect of a moving second device, if there are more first devices than available frequencies, several first devices can use the same frequency to transmit TDM sinusoidal pulses of limited duration (e.g., 100 ms).

[0033] Another approach to utilizing CDM is for different first devices to simultaneously transmit sets of sinusoidal pulses to create different sinusoidal frequency codes. In this case, the second device must recognize the frequency code used by its own first device and be able to handle situations where one or more sinusoidal pulses may collide with sinusoidal pulses emitted by one or more other first devices. If a first device cannot be uniquely detected using the ultrasonic signal it emits, the second device can use a handshake mechanism between the first and second devices to verify that the detected first device is the correct one. The second and first devices may have predefined ultrasonic signals to transmit to each other in a two-way handshake. In principle, the second device transmits a coded ultrasonic signal (e.g., a modulated message, a sinusoidal pulse containing one or more sinusoids from non-overlapping frequency ranges, a chirp, a coded signal, etc.) to the first device. If the first device recognizes the coded message, it can transmit another coded ultrasonic signal to the second device. If the pseudo-random number algorithm's random number seed is the same and the generated coded message is chosen randomly while the first device and second device have an active communication channel, the probability that another first device will be able to successfully complete the two-way handshake is significantly reduced.

[0034] While authentication can potentially be performed securely by modulating messages over ultrasound, the data rates of ultrasonic modems are too low for this purpose. Thus, once the two-way handshake is successfully completed, the second device can be fairly certain that it is communicating with the correct first device and can begin distance measurement. The first and second device pair can use a predetermined pseudorandom number sequence known to both devices to generate a constantly changing set of coded messages to prevent eavesdroppers from retransmitting old messages.

[0035] Devices with strict power requirements can reduce power consumption by using low-frequency ultrasonic signals (e.g., 20-24 kHz for a 48 kHz sampling rate) and therefore the smallest sampling rate appropriate for only the lowest frequencies. If a first device can detect one of its sine wave frequencies using a sampling rate lower than the remaining sine wave frequencies, the second device could potentially use a lower sampling rate until it detects the sine wave frequency or sine wave pulse used by the first device, and then change to a higher sampling rate when the next ultrasonic signal is received to properly sample the other frequencies of the signal emitted by the first device. Whether to switch sampling rates after the initial detection is typically a trade-off between detection response and power consumption.

[0036] If the first device is a stationary device but the second device is a mobile device, the second device can monitor its surroundings while moving and create an internal map of the first device's surroundings. As an example, a mobile second device can use the distance scheme described above to register any devices (e.g., WiFi access points, Bluetooth devices, noise sources, ultrasonic devices, etc.) or physical layout (i.e., stairs, elevators, etc.) that it detects while moving when the first device is out of range. The second device should also register relevant sensor events from the second device, such as IMU sensors, pedometers, door sensors, humidity sensors, ALS sensors, altimeters, and time. Similarly, the second device can register any devices (i.e., WiFi APs, Bluetooth devices, noise sources, ultrasonic devices, etc.) that it can detect when the first device is in range, as well as any associated sensors, such as IMU sensors, ALS sensors, pedometers, and altimeters. This information can be used to provide an overview of reachable locations for the first device.

[0037] This information can be added to the edge AI training process on either or both the first and second devices, where detected devices, sensor information, time information, etc. are used as inputs. Whenever a suitable communication channel is available between the first and second devices, the updated ML model can be transferred to the second device. Once the second device has the updated deep neural network model, events from the sensors and environment can be used as input features to a DNN inference engine to probabilistically determine whether the first device can be reached from the second device's current location. For example, if a mobile second device is mobile and temporarily unable to transfer data to the first device, it can transfer that information to the first device once a communication channel with the first device is re-established. This is true in scenarios where the second device may operate in a low-power state where all networking capabilities are temporarily disabled (i.e., a Windows laptop in Modern Standby power state). The data collected by the second device can be transferred to the first device as soon as the second device's power state is changed, networking capabilities are re-enabled, and a communication channel becomes available again.

[0038] In some scenarios, for example in an open environment such as an office building, cubicle environment, etc., there may be several first devices located in close proximity to each other, but a particular second device only needs to measure the distance to one specific one of these first devices. Since there may be more than one first device in close proximity, the second device needs to ensure that it measures the distance to the correct first device.

[0039] One possible solution is for every first device to emit a coded ultrasonic signal that is detectable within an ultrasonic detection zone around it. The size of the zone depends on the amplitude of the coded signal (i.e., chirp, one or more sine waves, one or more sine wave pulses, etc.) and the distortion it experiences. In open space, a typical zone is up to 10-15 meters in diameter. Obstacles such as walls can significantly reduce the size of the ultrasonic zone.

[0040] By transmitting a coded ultrasound signal from a first device, a corresponding second device can identify its own first device when it is able to detect the coded ultrasound signal.

[0041] This is important if the power consumption of the second device needs to be minimized. One possibility is for the second device and the first device to communicate using data modulation (e.g., FSK, PSK, etc.) with ultrasonic signals. Another option is to transmit data between the devices over an out-of-band communication channel (e.g., WiFi, Bluetooth, etc.), if available. In some cases, the out-of-band communication channel may need to be re-established by the second device and / or the first device to enable it.

[0042] In one embodiment, the first device is a videoconferencing device that wants to know the distance to all laptops in the same room. In this case, the first device uses transponding, and the second device responds to the signal from the first device by sending a delayed response signal back to the first device. Once the first device receives the response and adjusts the agreed-upon transponding delay, the first device can calculate the distance to the second device. If desired, information about the second device can be transmitted from the first device to the second device either as in-band information embedded in the signal from the first device to the second device, or as out-of-band information using any available wireless or optical communication technology.

[0043] In one embodiment, the first device is a gaming device that wants to know the distance to all game controllers in the same room. In this case, the first device transmits an ultrasonic signal and a radio signal at the same time. When the second device receives these signals and measures the difference in reception time, the second device can calculate the distance to the first device. When the first device receives the response and adjusts the agreed-upon transponding delay, the first device can calculate the distance to the second device. If desired, information about the second device can be transmitted from the first device to the second device either as in-band information embedded in the signal from the first device to the second device, or as out-of-band information using any available communication technology.

[0044] In another embodiment, the first device is a door access system that displays different access panel menus depending on how far away the personal access device is. In this embodiment, both the first device and the second device have their clocks synchronized by any known high-precision synchronization protocol (e.g., NTP, PTP, etc.). The first device transmits an ultrasonic signal at a predefined start time, which is received by the second device, and the distance between the first device and the second device can then be calculated.

[0045] In another embodiment, the video conferencing system wants to know the distance to the mobile device (e.g., a smartphone) that is currently controlling the conferencing system. This allows the video conferencing system to track how far away the mobile device is. This can be useful if the mobile device leaves the room and the video conferencing system wants to regain control.

[0046] In yet another embodiment of the present invention, when a secondary device approaches a primary device closer than a preconfigured distance threshold, either device can connect to the other device via wireless technology, including WiFi, Bluetooth, etc., to enable communication between the two devices. Before establishing a connection, there may be additional conditions to be met, including device state, device configuration (e.g., hinge angle, folded, unfolded, screen detached, lid closed, etc.), device orientation, power state, biometric authentication such as, but not limited to, face ID, voice recognition, and fingerprint. Gesture, i.e., the manner in which either or both devices are handled (e.g., shaking, lifting, swinging, etc.), may be another condition to be met to initiate a connection. Other conditions may include not only the distance between the devices but also the relative positions between the devices based on the techniques described in NO20221246 and NO20221243. Before a connection is initiated, the secondary device may need to be in a predefined position relative to the primary device, such as to the right, left, below, in front of, or above the primary device. Another solution is to use presence sensing solutions, including acoustic solutions, to monitor the surroundings and prevent a connection from being initiated if another user is nearby. Allowing the user to control when a connection is initiated by combining a set of conditions may also be a possible solution.

[0047] For security reasons, the user may be required to approve the connection setup via at least one biometric authentication method (e.g., fingerprint, voice recognition, face ID, etc.) or an approval dialog on either or both devices.

[0048] According to yet another embodiment, one of the connected devices is a wireless access point and may include an audio system with an output device capable of transmitting ultrasonic messages to devices in the vicinity of the access point. Because the ultrasonic messages are effectively limited to the room in which the access point is transmitting due to the physical properties of ultrasound, the ultrasonic messages may include information about how to connect to the wireless network handled by the wireless access point.

[0049] The message may include SSID and corresponding password information, allowing the recipient of the ultrasound message to seamlessly connect to the wireless network. Even if the information extracted from the ultrasound message is not used to automatically connect to the wireless network, these ultrasound messages can also be used to filter out all wireless access points outside the room. Unless an ultrasound message corresponding to a specific wireless access point is heard, the device can filter access points in other rooms from its list of available networks.

[0050] In another scenario, with small cellular base stations (e.g., femtocells) targeted at homes and small businesses, ultrasound from the cellular base station (CBS) allows the user equipment (UE) to filter out all CBSs outside the space or room in which the UE is currently located. In apartment buildings with multiple CBSs, selecting a preferred CBS can be problematic. If a CBS can transmit an ultrasound message and the UE can receive it, the UE can use this message to connect to a CBS in the same room, rather than, for example, the CBS with the strongest signal. The ultrasound message may contain additional information about the cellular network, including cost, QoS parameters, etc., allowing the UE to make an informed decision about whether to connect via the CBS. It is also possible for the UE and CBS to exchange multiple ultrasound messages. These messages can be used to send secure messages between devices to verify whether the UE can connect to the CBS. These messages can also be used to measure the distance between devices, as described above. Based on these distance measurements, either the UE or the CBS may not allow the UE to connect to the cellular network via the CBS. There may be other conditions that control if or when a UE can connect to a CBS.

[0051] Filtering out devices based on proximity may be more important for Bluetooth devices (e.g., smart speakers, cars, laptops, etc.) than for Bluetooth devices that are farther away.

[0052] In summary, the present invention relates to a system for monitoring the relative position between at least two electronic devices comprising wireless communication means, a first of said devices comprising at least one first transducer unit configured to receive a predetermined request signal, a second of said devices comprising a motion sensor and at least one second transducer unit configured to transmit a predetermined request signal to be received by said first transducer unit, and wherein the first device is configured, upon receipt of said request signal, to initiate communication between them suitable for measuring the distance between the devices, and a response signal is transmitted to the second device.

[0053] The signal may be coded or have properties suitable for calculating the distance between the devices.

[0054] Preferably, the transducer unit includes an acoustic transducer for transmitting and receiving an acoustic signal, and the distance is calculated based on the propagation time and / or amplitude of the signal. The distance may be calculated in a processor of the second device, or the necessary information is communicated to the first device for processing, the communication including the result of measuring the propagation time of the acoustic signal between the first transducer unit and the second transducer unit.

[0055] Preferably, the first and second communication units also include electromagnetic communication to provide synchronization of the devices, the propagation time being measured from one of the devices to the other.

[0056] According to another embodiment, the second transducer unit is configured to transmit a second acoustic signal after a predetermined time, the first transducer unit is configured to receive a signal from the second acoustic signal, and the first device is configured to measure a distance between the devices based on a measured time from the first acoustic transmission.

[0057] The communication means of the device may include an electromagnetic transmitter and receiver configured to detect signals from the device, and the system may be configured to transmit a request signal only if another suitable device is detected within the system.

[0058] The second device of the devices according to the invention comprises a wireless communication unit for communicating with at least one other electronic device, a transducer unit for receiving a predetermined signal, and a motion sensor. The communication unit, the transducer unit, and the sensor are connected to a main processor configured to initiate transmission of a request signal upon detection of motion, and to calculate the distance to the other electronic device upon reception of the predetermined signal at the transducer unit. As mentioned above, preferably, the predetermined signal is an acoustic signal, and the distance is calculated based on the propagation time or amplitude of the received acoustic signal.

[0059] The first electronic device also includes a wireless communication unit for communicating with at least one other electronic device and a transducer unit for transmitting a predetermined signal. The communication unit and the transducer unit are connected to a processor. The processor is configured to transmit a predetermined response signal via the transducer unit upon receiving a request signal according to a predetermined protocol or specification via the wireless communication system. The processor may be configured to receive a signal via the communication system indicating a distance to the other device.

[0060] A method according to the present invention for providing distance measurement between a first electronic device and a second electronic device, the first electronic device and the second electronic device being connected and configured to communicate using wireless communication means, the method comprising: - detecting movement of the second device; - transmitting a request signal from the second device to the first device; - receiving, at a first device, the request signal and generating a response signal using a first transducer; - receiving a response signal at a second device; - calculating the distance between the devices based on the response signals; Includes.

[0061] The method may also include the step of calculating the distance based on the propagation time and / or amplitude of the acoustic signal, and the additional step of determining whether the distance is within a predetermined range and establishing wireless communication if predetermined requirements are met, the requirements including the distance being within the predetermined range. [Explanation of symbols]

[0062] 1. First Device 2 Second Device 4a microphone 4b Microphone 5 Main Processor 6 sensors 7 speakers 8 processors 31 First Device 33a Second Device 33b Second Device 34a Response signal 34b Response signal 36a circuit 36b circuit

Claims

1. 1. A system for monitoring the relative position between at least two electronic devices comprising wireless communication means, wherein a first of said devices comprises at least one first transducer unit configured to receive a predetermined request signal, and a second device comprises a motion sensor and at least one second transducer unit configured to transmit said predetermined request signal to be received by said first transducer unit, and wherein said first device is configured, upon receipt of said request signal, to initiate communication between said devices suitable for measuring the distance therebetween.

2. The system of claim 1 , wherein the transducer unit includes an acoustic transducer for transmitting and receiving acoustic signals, and the distance is calculated based on a propagation time of the signals.

3. The system of claim 2 , wherein the communication includes measuring the time of flight of an acoustic signal between the first transducer unit and a second transducer unit.

4. 4. The system of claim 3, wherein the first and second transducer units also include electromagnetic communication means for synchronizing the devices, and the propagation time is measured from one of the devices to the other.

5. 4. The system of claim 3, wherein the second transducer unit is configured to transmit a second acoustic signal after a predetermined time, the first transducer unit is configured to receive the signal from the second acoustic signal, and the first device is configured to measure the distance between the devices based on the measured time from the first acoustic transmission.

6. 10. The system of claim 1, wherein the device includes an electromagnetic transmitter and receiver configured to detect a signal from the device, and the system is configured to transmit the initiation signal only if another device is detected.

7. The system of claim 1 , wherein the device is configured to establish wireless communication when predetermined requirements are met, the requirements including the distance being within a predetermined range.

8. An electronic device comprising a wireless communication unit for communicating with at least one other electronic device, a transducer unit for receiving a predetermined signal, and a motion sensor, wherein the communication unit, transducer unit, and sensor are connected to a main processor, the main processor being configured to initiate the transmission of a request signal upon detection of motion, and to calculate the distance to the other electronic device upon reception of the predetermined signal at the transducer unit.

9. 9. The electronic device of claim 8, wherein the predetermined signal is an acoustic signal, and the distance is calculated based on the propagation time or amplitude of the received acoustic signal.

10. 1. An electronic device comprising: a wireless communication unit for communication with at least one other electronic device; and a transducer unit for transmitting a predetermined signal, wherein the communication unit and the transducer unit are connected to a processor, the processor being configured to transmit the predetermined signal via the transducer unit upon receiving a request signal via wireless communication; and the processor being configured to receive a signal indicative of the distance to the other device.

11. 1. A method for providing distance measurement between a first electronic device and a second electronic device, the devices being connected and configured to communicate using wireless communication means, the method comprising: - detecting a movement of the second device; - transmitting a request signal from the second device to the first device; - receiving the request signal at the first device and generating a response signal using a first transducer; - receiving the response signal at the second device; - calculating the distance between the devices based on the response signals; A method comprising:

12. The method of claim 9 , wherein the response signal is an acoustic signal and the distance is calculated based on the propagation time and / or the amplitude of the acoustic signal.

13. 10. The method of claim 9, comprising the additional step of determining whether the distance is within a predetermined range and establishing wireless communication if predetermined requirements are met, the requirements including the distance being within the predetermined range.

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