Device ranging

Abstract

The present invention relates to a method and related systems and devices for providing distance measurements between a first electronic device and a second electronic device, where the devices are connected to a wireless communication device and configured to communicate using the wireless communication device. The method comprises the steps of detecting a movement of the second device, sending a request signal from the second device to the first device, at the first device, receiving the request signal and generating a response signal using the first transducer, at the second device, receiving the response signal, and calculating a distance between the devices from the response signal.

Description

Technical Field

[0001] The present invention is based on calculating the absolute distance between a first electronic device and a second electronic device. Background Art

[0002] In some cases, a user of an electronic device may advantageously know the distance between two potentially mobile electronic devices at configurable regular intervals or triggered by other mechanisms. When the distance between the two devices is at a preconfigured distance, the distance measurement can be used to initiate any number of different operations on one or both devices. Alternatively, knowing the distance between these devices can prevent or allow these devices to cooperate or communicate based on the distance between them.

[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 sent between these devices. Each device has a speaker and two microphones, and two-dimensional positioning can be performed as on a desktop. Radio communication (Bluetooth or WiFi) can be used to increase the communication capabilities between these devices and provide additional possibilities for device synchronization. In US2021 / 0400417, an audio system is described in which different devices are able to determine 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, where the distance measurement can use the phase difference based on a sound sensor. This is used to combine a synchronization signal and sound.

[0005] Several methods for measuring distance and / or relative position are known, but they generally require active sensors to continuously listen for nearby devices because new devices may enter the vicinity or these devices may be moved, thus changing the relative position between these devices. This is power-consuming, and an object of the present invention is to provide a solution that minimizes the power consumption of the devices. Summary of the Invention

[0006] The object of the present invention is achieved as described in the appended claims.

[0007] Therefore, according to the present invention, an energy-saving solution is provided because the solution only detects the distance between devices and the possible relative position when these devices are activated by an event related to a change in distance (for example, by using an inertial measurement unit, etc., to record that one of these devices has moved). Brief Description of the Drawings

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

[0009] Figure 1 Two devices according to the present invention are shown.

[0010] Figure 2 The sequence of the method according to the present invention is shown.

[0011] Figure 3 A system according to the present invention including a computer and two mobile devices is shown. Detailed Description

[0012] Figure 1 The first device 1 and the second device 2 are shown, both including being configured to communicate using WiFi or a similar system. The second device 2 further includes a sensor 6 with low power consumption, such as an inertial measurement unit (IMU), which is connected to the main processor 5. In the figure, the second device 2 is a mobile phone, which also includes microphones 4a, 4b and a speaker 7.

[0013] When the sensor 6 detects movement, this indicates that the distance needs to be updated. In this case, the processor in the second device 2 uses the WiFi connection to send a request signal. Initially, the movement can include activating a button or pressing a computer mouse or touchpad to initialize the system, but at a later stage, the movement mainly includes activities that presumably change the relative position and orientation between these devices. The request signal is received by the processor 8 in the first device 1, which instructs the transducer 3 to send a response signal 3a, which will be 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, which is received by at least one of the microphones 4a, 4b in the first device. If the second device is provided with two microphones, the angle of the input signal can be analyzed, and the distance D and possible relative position between these devices can be calculated, for example, as described in NO20221246.

[0014] If the distance is within a predetermined limit, for example, within a predetermined area around the first device and / or if other requirements such as protocol type, signal strength, etc. are met, a WiFi connection can be established. For example, if the distance, position and orientation are within a predetermined limit, a computer mouse can request to use Bluetooth pairing, for example, giving priority to a mouse configured to be used with the right hand, which is placed on the right side and within the actual distance from the computer.

[0015] Reference Figure 2 , the sequence of this operation can thus be:

[0016] 21 Detect movement in the second device using a sensor 6 with low power consumption (such as an IMU).

[0017] 22 In the second device 2, send a request signal using a wireless communication system such as WiFi, Bluetooth, etc.

[0018] 23 The request signal is received in the first device 1.

[0019] 24 A response signal is generated from the first device, preferably an acoustic signal in the ultrasonic range.

[0020] 25 The second device receives the response signal and calculates the distance between the devices.

[0021] When the distance has been calculated, the system can wait for another movement to be detected or repeat the process as long as a movement is recorded. The distance information can be distributed in the system (e.g., using WiFi) such that the first device can adapt to the distance between the devices.

[0022] If the direction between the devices is known or has been measured, e.g., as disclosed therein, and the IMU is capable of measuring the direction of movement, the process can be started only when the movement is in the direction between the devices, thus changing the distance.

[0023] Figure 3 A case is shown where the first device is a computer and there are two second devices 33a, 33b, each of which includes circuits 36a, 36b that detect movement and send a request signal to the first device 31, and the first device 31 responds by sending response signals 34a, 34b. The request signal should preferably include an identification code such that the first device can adapt the communication between the devices to the said distance and possibly to the orientation and relative position. There can also be two first devices in the system. If there are several first devices with a known or measured relative position, the mobile device can select a first device by recording the movement or orientation of the mobile device, e.g., as described in NO20221243. As an example, the first device can be a computer associated with a video conferencing system that allows the second devices to access (possibly restricted) to join the system and present files in the system, thus creating an ad-hoc network.

[0024] As described above, there are different ways to measure the distance between electronic devices. Using ultrasound for ranging is a viable technique that allows an electronic device to measure the distance between itself and another electronic device. In this case, both electronic devices need at least one ultrasound transducer to send an ultrasound signal (e.g., a chirp) to the other electronic device at time T0, and at least one ultrasound transducer in the other device receives the ultrasound signal by receiving the transmitted signal at time T1. When the second device receives the ultrasound signal from the first device, the second device will send the ultrasound signal back to the first device again using the same ultrasound transducer or using another ultrasound transducer. The first device will receive the ultrasound response signal at time T2 in the same ultrasound transducer or another ultrasound transducer, and based on the speed of sound and the time elapsed since sending the first ultrasound signal (i.e., T2 - T0), calculate the distance between these devices. The second device can use its own ultrasound signal to delay the response by a predefined delay D that is known to both the first device and the second device, causing the second device to use the elapsed time T2 - D - T0 to adjust the distance measurement when calculating the distance as described above.

[0025] In most cases, it would be advantageous if the first device and the second device could communicate simultaneously in simplex or duplex using another wireless technology such as Bluetooth or WIFI. If no other viable option is available, the communication channel can be replaced with a low-bitrate acoustic communication channel based on acoustic wave modulation.

[0026] An alternative to ranging is to synchronize the clocks of the first device and the second device within the required specifications in order to provide distance measurements with the required accuracy. If these devices are part of the same data network or when these devices are part of the same data network, synchronization protocols such as the Network Time Protocol or the Precision Time Protocol can be used. An obvious benefit of relying on clock synchronization is that the second device does not have to send any ultrasound signal back to the first device. The time elapsed between the first device sending the ultrasound signal and the second device receiving the ultrasound signal, T1 - T0, can be used to calculate the distance between these devices in the second device. If the clocks of these devices are synchronized, distance measurement can be accomplished by the first device sending at least one ultrasound signal at a predefined time. The ultrasound signal can be sent only once or at a predefined interval known to both devices, enabling the second device to calculate the distance based on a) the elapsed time and b) the speed of sound. The first device can also send a timestamp in a separate out-of-band data channel to the second device indicating when the ultrasound signal will be sent or has been sent. If the out-of-band channel is not available, in-band ultrasound modulation techniques can also be used to send the information.

[0027] A third option is to send a radio signal and an ultrasonic signal at the same time and measure the time difference when these signals are received. Radio signals will travel at the speed of light. Another possible technique is to send a wireless signal (e.g., wifi, Bluetooth, Zigby, etc.) at the same time as the ultrasonic signal and measure the time difference between the radio signal and the ultrasonic signal when they arrive at the second device. The time difference and the speed of sound can be used to calculate the distance between the two devices.

[0028] Another possible technique is to exploit the difference in the speed of sound at different frequencies, for example, as described in https: / / pages.mtu.edu / ~suits / SpeedofSound.html. By using an acoustic signal that includes both infrasound and ultrasonic components, receiving the different components of the signal at a sampling rate that is capable of detecting the difference in the speed of sound can be used to estimate the distance between the first device and the second device based on the known difference in air speed.

[0029] The fifth option is to use the signal amplitude of the received signal as an approximation of the distance to other devices based on empirical data. This is only feasible in the following case: the ultrasonic transducer of the first device that sends the output signal is not covered or wrapped by one or more objects, but sends the output signal in the same space where the second device is located. Combining the amplitude information with other pieces of information (e.g., device orientation) or techniques as described above can provide additional information. At the same time, the use of empirical data can enable the second device to know that the first device is covered or wrapped by one or more objects, which may reduce the signal output and the reachable distance. Today's widespread electronic devices have many sensors, including 6-degree-of-freedom inertial measurement unit sensors (IMUs). These sensors can be used to detect device orientation, which in turn can be used to select a set of ideal ultrasonic transceivers (e.g., microphones facing the first device) for receiving ultrasonic signals from the first device or sending ultrasonic signals to the first device.

[0030] If one or both devices are moving away from the other, the distance measurement will change as the devices move away from each other and therefore be less accurate or out of date by the time the measurement is completed. One way to adjust the distance measurement is to include a Doppler measurement of the incoming ultrasound signal and adjust the calculated distance measurement using the motion offset predicted by the Doppler information in the received ultrasound signal, as discussed in NO20221244.

[0031] As described above, due to power limitations of the electronic device or interference in the frequency band in use, it may not be practical to use the acoustic signals as stated above and in some cases radio signals for continuous distance measurements. In some cases, it may be necessary to duty cycle the distance measurements at fixed intervals or predetermined intervals. These devices can also agree to use pseudo-random intervals based on an agreed random seed for the intervals used in the distance measurements to reduce the likelihood of interference from other devices making measurements in the same area.

[0032] The object of the present invention can be solved by using an IMU sensor to trigger distance measurements only when absolutely necessary. The power consumption of an IMU sensor is generally lower than that of an acoustic sensor.

[0033] Thus, according to a preferred embodiment of the present invention, the IMU sensor in the first device or the second device can trigger a new set of distance measurements when a significant lateral movement is detected, because the last distance measurement may be invalid after the device has moved or is still moving. The distance measurements should continue while at least one of these devices is still moving. Once the IMU sensor indicates that the movement has stopped, the distance measurements can stop once the distance to the device is measured again. If these devices are installed in a moving vehicle or object (e.g., a train, a ship, etc.), it may be necessary to compare the IMU sensor data between the two devices to determine whether the devices are moving relative to each other. If so, a new set of distance measurements is required.

[0034] Another mechanism to prevent unnecessary distance measurements is that if the first device emits a conventional wireless beacon with a limited range, the second device can detect the beacon when it is close enough. Thus, if the second device cannot hear the beacon from the first device, distance measurements are not required. Similarly, the first device can use, for example, GPS technology to establish a geofence area around the device, where the second device can use its own GPS device (if available) to limit the distance measurements to the case where the second device is within the geofence area established by the first device.

[0035] If the first device is stationary but the second device is mobile, another possible solution is to use low-power environmental sensors (e.g., temperature sensors, humidity sensors, air quality sensors, atmospheric sensors, etc.) in the second device (if available) to determine when the second device is likely to be close to the first device. When the current environment indicates that the second device is not in the same environment as the first device based on historical data or a deep neural network based on historical data, the first device and the second device can exchange historical sensor data as long as a suitable communication channel is available to allow the second device to enter a power-saving mode. The system is capable of detecting the presence of nearby objects or people and restricting sensor activity based on the type of sensor activity measured.

[0036] Another solution is to emit an identifiable ultrasonic signal from the first device if the power limit of the first device permits. This is possible if the first device is a stationary device connected to a power source. The idea is that the second device will listen for the ultrasonic signal emitted by the first device and start a distance measurement process when the signal is detected.

[0037] If one of the ultrasonic signals emitted from the first device when the second device starts moving away from the first device is a sine wave or a set of sine waves, the second device can use the change in one or more sine frequencies to estimate the speed of the second device as it moves away from the first device and estimate the change in distance of the second device as it moves away from the first device based on integration. These estimates can be compared with the estimates of the device speed and the corresponding distance traveled from the IMU sensor data. The estimates from the two data sources can provide more accurate information about the path of the second device relative to the first device, e.g., as described in NO20221244.

[0038] In some cases where one of these devices is mobile (e.g., being carried, worn, attached to a person or animal, etc.) and the other is stationary, the current relative speed of the mobile device with respect to the other device and the changing relative distance between these devices can be used to infer the user's intention of relative movement. Combining distance measurement with the instantaneous speed of the mobile device based on IMU data and the Doppler effect estimation of the transmitted sine signal allows the mobile device to determine where the user is going and what action to take based on this.

[0039] In a scenario where there are more than one first devices in a limited area, where a second device can receive ultrasonic signals from multiple first devices simultaneously, the ultrasonic signals transmitted from each first device should preferably be unique. With unique signals, the second device can easily detect that the second device is within the range of the correct first device. However, the ultrasonic frequency band is limited, and it is not practical to create unique signals for each first device and have these unique signals not be affected by interference from signals transmitted from other first devices, for example. Known multiplexing techniques such as FDM (Frequency Division Multiplexing), TDM (Time Division Multiplexing), CDM (Code Division Multiplexing), and SDM (Space Division Multiplexing) can be used to create a fixed number of unique signals. A frequency band can be reserved that has a fixed number of different frequencies, where each first device transmits a signal with a designated frequency. If there are more first devices than available frequencies, considering that the available frequencies need to be separated in frequency (e.g., 150 Hz) to avoid incorrect frequency detection due to the Doppler effect of a moving second device, several first devices can use the same frequency to emit TDM sine pulses with a limited duration (e.g., 100 ms).

[0040] Another way to utilize CDM is to have different first devices emit a set of concurrent sine pulses to create different sine frequency codes. In this case, the second device must know the frequency code used by its own first device and be able to handle the situation where one or more of the sine pulses may conflict with sine pulses transmitted by one or more other first devices. If the first device cannot be uniquely detected using the ultrasonic signal transmitted by the first device, the second device can use a handshake mechanism between the first device and the second device to ensure that the detected first device is the correct first device. The second device and the first device can have a predetermined ultrasonic signal to send to each other using a two-way handshake. In principle, the second device will send an encoded ultrasonic signal to the first device (e.g., a modulated message, sine pulses with one or more sines from non-overlapping frequency ranges, a chirp, an encoded signal, etc.). Once the first device recognizes the encoded message, the first device can send another encoded ultrasonic signal to the second device. If the random seeds of the pseudo-random algorithms are the same and the generated encoded messages are randomly picked when the first device and the second device have an active communication channel, the probability that another first device will be able to correctly complete the two-way handshake significantly decreases.

[0041] Although modulating messages via ultrasound may ensure authentication, the data rate of an ultrasonic modem is too low for this purpose. Thus, once the two-way handshake is correctly completed, the second device can be almost certain that it is communicating with the correct first device and can start distance measurement. The paired first and second devices can use a pre-arranged pseudo-random sequence known to both devices to generate a set of ever-changing coded messages to prevent eavesdroppers from replaying older messages.

[0042] In devices with strict power requirements, using low-frequency ultrasonic signals (e.g., low-frequency ultrasonic signals of 20 - 24 kHz if the sampling rate is 48 kHz) and thus using the minimum sampling rate applicable only to the lowest frequencies can reduce power consumption. If one of the sine frequencies used by the first device can be detected using a lower sampling rate than the remaining sine frequencies, the second device may use the lower sampling rate until the second device detects the sine frequency or sine pulse used by its first device and then changes to a higher sampling rate to correctly sample the other frequencies of the signal transmitted by the first device when receiving the next ultrasonic signal. Whether to switch the sampling rate or not after the initial detection is usually a trade-off between detection response and power consumption.

[0043] If the first device is a fixed device but the second device is a mobile device, the second device can monitor its surrounding environment while moving around and create an internal map of the surrounding environment of the first device. As an example, the mobile second device can record any devices (e.g., WIFI access points, Bluetooth devices, noise sources, ultrasonic devices, etc.) or physical layouts (i.e., stairs, elevators, etc.) detected by the second device while moving around when the first device cannot be reached using the distance scheme discussed above. The second device should also record relevant sensor events from the second device, such as IMU sensors, pedometers, door sensors, humidity sensors, ALS sensors, altimeters, time, etc. Similarly, when the first device is within reach, the second device can record any devices (i.e., WIFI access points, Bluetooth devices, noise sources, ultrasonic devices) and relevant sensors, such as IMU sensors, ALS sensors, pedometers, altimeters, etc., that the second device can detect. This information can be used to create an overview of the locations reachable by the first device.

[0044] This information can be added to the edge artificial intelligence training process in one or both of the first device and the second device, where the detected device, sensor information, time information, etc. are used as inputs. Whenever a suitable communication channel between the first device and the second device is available, the updated machine learning model can be transmitted to the second device. Once the second device has obtained the updated deep neural network model, events from sensors and the environment can be used as input features for the deep neural network inference engine to make a probability decision on whether it is likely to be reachable from the current location of the second device to the first device. As an example, if the moving second device is mobile and temporarily unable to transmit data to the first device, as long as the second device re - establishes a communication channel with the first device, the second device can transmit the information to the first device. This is relevant to the scenario where the second device can operate in a low - power state where all networking capabilities are temporarily disabled (i.e., a Windows laptop in the modern standby power state), and once the power state of the second device is changed and the networking capabilities are re - enabled and the communication channel is available again, the data collected by the second device can be transmitted to the first device.

[0045] In some scenarios, in an open environment (e.g., office building, cubicle environment, etc.), there may be several first devices that are very close to each other, but a particular second device should only measure the distance to a particular one of these first devices. Since there may be more than one very close first device, the second device needs to ensure that it measures the distance to the correct first device.

[0046] A possible solution is that each first device emits an encoded ultrasonic signal that can be detected in the ultrasonic detection zone around the first device. The size of this zone depends on the amplitude of the encoded signal (i.e., chirp, one or more sine waves, one or more sine pulses, etc.) and the distortion it will undergo. In an open space, the typical zone diameter can reach 10 - 15 meters. Obstacles such as walls can significantly reduce the size of the ultrasonic zone.

[0047] Emitting an encoded ultrasonic signal from the first device enables the corresponding second device to identify its first device when the second device can detect the encoded ultrasonic signal.

[0048] This is important in cases where the power consumption of the second device should be minimized. One possibility is that the second device and the first device communicate using data modulation (e.g., frequency - shift keying, phase - shift keying, etc.) via the ultrasonic signal. Another option is to send data between these devices via an out - of - band communication channel (e.g., WIFI, Bluetooth, etc.) if an out - of - band communication channel is available. In some cases, the out - of - band communication channel may have to be re - established first by the second device and / or the first device to enable out - of - band communication.

[0049] In one embodiment, the first device is a video conferencing device that wants to know the distances to all the laptops in the same room. In this case, the first device will use a response where the second device will respond to the signal from the first device with a delayed response signal sent back from the second device to the first device. When the first device receives the response and adjusts for the agreed-upon response delay, the first device can calculate the distance to the second device. If desired, any available wireless communication technology or optical communication technology can be used to send information about the second device from the first device to the second device as in-band information embedded in the signal from the first device to the second device or as information in an out-of-band signal.

[0050] In one embodiment, the first device is a gaming device that wants to know the distances to all the game controllers in the same room. In this case, the first device will send a radio signal while it sends an ultrasonic signal. When the second device receives these signals and measures the time difference of reception, the second device can calculate the distance to the first device. When the first device receives the response and adjusts for the agreed-upon response delay, the first device can calculate the distance to the second device. If desired, any available communication technology can be used to send information about the second device from the first device to the second device as in-band information embedded in the signal from the first device to the second device or as information in an out-of-band signal.

[0051] In another embodiment, the first device is an access control system that will display different access panel menus based on the proximity of personal access devices. In this embodiment, both the first device and the second device synchronize their clocks with any known high-precision synchronization protocol (such as NTP, PTP, etc.). The first device will emit an ultrasonic signal at a predetermined start time, and this signal will be received by the second device, and then the second device can calculate the distance between the first device and the second device.

[0052] In another embodiment, a video conferencing system wants to know the current distance to a mobile device (e.g., a smart phone) that controls the conferencing system. This allows the video conferencing system to track the current distance of the mobile device. This can be beneficial in cases where the mobile device leaves the room and the video conferencing system wants to regain control.

[0053] In yet another embodiment of the present invention, when the second device is closer to the first device than a preconfigured distance threshold, either device can connect to the other device via a wireless technology including WiFi, Bluetooth, etc., enabling the two devices to communicate. Before establishing a connection, there may be additional conditions that must be met, including device status, device configuration (hinge angle, fold, unfold, screen separation, lid closed, etc.), device orientation, power status, biometric security, such as but not limited to face recognition, voice recognition, fingerprint, etc. Gestures, i.e., how to operate one or both devices (e.g., shake, lift, wave, etc.) may be another condition that must be met to initiate a connection. Based on the techniques discussed in NO20221246 and NO20221243, other conditions can include not only the distance between these devices but also the relative position between these devices. Before initiating a connection, the second device may need to be in a predetermined position relative to the first device, e.g., to the right, left, below, in front of, or on top of the first device. Another solution is to use a presence sensing solution including an acoustic solution to monitor the surrounding environment to prevent a connection from being initiated when other users are nearby. Combining a set of conditions can also be a possible solution to enable the user to control when to initiate a connection.

[0054] For security reasons, the user may have to utilize at least one biometric scheme (e.g., fingerprint, voice recognition, face recognition) or an approval dialog on either one or both devices to approve the connection establishment.

[0055] According to yet another embodiment, one of the devices to be connected is a wireless access point, which can include an audio system having an output device capable of sending ultrasonic messages to devices near the access point. Since for all practical purposes ultrasonic messages are confined within the room where the access point is transmitting by the physical properties of ultrasonic waves, the ultrasonic messages can include information on how to connect to the wireless network handled by the wireless access point.

[0056] These messages can include the network name and corresponding password information enabling the recipient of the ultrasonic message to seamlessly connect to the wireless network. Even if the information extracted from the ultrasonic message is not used for automatically connecting to the wireless network, these ultrasonic messages can be used to filter out all wireless access points outside the room. Unless no ultrasonic message corresponding to a specific wireless access point is heard, the device can filter out wireless access points in other rooms from the list of available networks.

[0057] In another scenario of small cell base stations (e.g., femtocells) targeted at homes and small businesses, sending ultrasound from a cellular base station (CBS) will enable a user equipment (UE) to filter out all CBSs outside the space or room where the UE is currently located. In an apartment building where multiple CBSs have been installed, it may be a problem for the UE to select a preferred CBS. If the CBS can send ultrasound messages and the UE can receive them, the UE can use these messages to connect to the CBS in the same room rather than, for example, the CBS with the highest signal strength. The ultrasound messages can include additional information about the cellular network, including cost, QoS parameters, etc., which will allow the UE to make an informed decision on whether it should connect via the CBS. The UE and CBS can also exchange multiple ultrasound messages. These messages can be used to send security messages between these devices to verify that the UE is allowed to connect to the CBS. As described above, these messages can also be used to measure the distance between these devices. Based on these distance measurements, the UE or CBS may not allow the UE to connect to the cellular network via the CBS. There may also be other conditions that control when or whether to allow the UE to connect to the CBS.

[0058] Filtering out devices based on proximity may be more important for Bluetooth devices (e.g., smart speakers, cars, laptops, etc.). Bluetooth devices are located farther away.

[0059] In summary, the present invention relates to a system for monitoring the relative position between at least two electronic devices equipped with wireless communication means, wherein a first device of the devices includes at least one first transducer unit configured to receive a predetermined request signal, and a second device includes a motion sensor and at least one second transducer unit configured to send the predetermined request signal for the first transducer unit to receive, wherein the first device is configured to initiate communication between the first device and the second device upon receiving the request signal, the communication being adapted to measure the distance between the devices, and a response signal is sent to the second device.

[0060] These signals can be encoded to be adapted to calculate the distance between the devices or have characteristics adapted to calculate the distance between the devices.

[0061] Preferably, the transducer unit includes an acoustic transducer for sending and receiving acoustic signals, and the distance is calculated based on the propagation time and / or amplitude of the signal. The distance can be calculated in the processor of the second device or necessary information can be transmitted to the first device for processing, wherein the communication includes the result of measuring the propagation time of the acoustic signal between the first transducer unit and the second transducer unit.

[0062] Preferably, the first communication unit and the second communication unit further include providing electromagnetic communication for synchronizing the devices, and the propagation time is measured from one device to another device in the devices.

[0063] According to another embodiment, the second transducer unit is configured to send 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 the distance between the devices based on the measurement time starting from the first acoustic transmission.

[0064] The communication means of the devices may include an electromagnetic transmitter and a receiver, and the electromagnetic transmitter and the receiver are configured to detect signals from one device. The system may be configured to send a request signal only when another suitable device is detected in the system.

[0065] The second device according to the present invention will include 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 all connected to a main processor, and the main processor is configured to initiate the transmission of a request signal when motion is detected, and calculate the distance from the other electronic device when the predetermined signal is received at the transducer unit. As described above, the predetermined signal is preferably an acoustic signal, and the distance is calculated based on the propagation time or amplitude of the received acoustic signal.

[0066] The first electronic device further includes a wireless communication unit for communicating with at least one other electronic device and a transducer unit for sending a predetermined signal. The communication unit and the transducer unit are connected to a processor. When the processor receives a request signal through a wireless communication system according to a predetermined protocol or specification, the processor is configured to send a predetermined response signal through the transducer unit. Through the communication system, the processor may be configured to receive a signal indicating the distance from other devices.

[0067] According to the method for providing distance measurement between a first electronic device and a second electronic device according to the present invention, the first electronic device and the second electronic device are connected to a wireless communication device and are configured to communicate using the wireless communication device. The method includes the following steps:

[0068] - Detecting the movement of the second device,

[0069] - Sending a request signal from the second device to the first device,

[0070] - At the first device, receive the request signal and generate a response signal using a first transducer,

[0071] - At the second device, receive the response signal,

[0072] - Calculate the distance between the devices based on the response signal.

[0073] The method may further include the steps of calculating the distance based on the propagation time and / or amplitude of the acoustic signal, and determining whether the distance is within a predetermined limit and establishing wireless communication if a predetermined requirement is met, the requirement including that the distance is within the predetermined limit.

Claims

1. A system for monitoring the relative position between at least two electronic devices equipped with wireless communication means, wherein a first device 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 for reception by said first transducer unit, wherein, The first device is configured to initiate communication between the first device and the second device upon receiving the request signal, and the communication is adapted to measure the distance between the devices.

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

3. The system according to claim 2, wherein the communication includes measuring the propagation time of the acoustic signal between the first transducer unit and the second transducer unit.

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

5. The system according to claim 3, wherein the second transducer unit is configured to send 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 measurement time starting from the first acoustic transmission.

6. The system according to claim 1, wherein the devices include an electromagnetic transmitter and receiver configured to detect a signal from one device, and the system is configured to send the start signal only when another device is detected.

7. The system according to claim 1, wherein the devices are configured to establish wireless communication if a predetermined requirement is met, and the requirement includes that the distance is within a predetermined limit.

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, the transducer unit, and the sensor are all connected to a main processor, and the main processor is configured to initiate transmission of a request signal upon detecting motion and, when the predetermined signal is received at the transducer unit, calculate the distance from the other electronic device.

9. The electronic device according to 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. An electronic device, comprising a wireless communication unit for communicating with at least one other electronic device and a transducer unit for sending a predetermined signal, wherein the communication unit and the transducer unit are connected to a processor, and the processor is configured to send the predetermined signal through the transducer unit when a request signal is received through wireless communication, and the processor is configured to receive a signal indicating the distance from the other device.

11. A method for providing distance measurement between a first electronic device and a second electronic device, the devices being connected to a wireless communication means and configured to communicate using the wireless communication means, the method comprising the steps of: - Detecting movement of the second device, - Sending a request signal from the second device to the first device, - At the first device, receive the request signal and generate a response signal using a first transducer, - At the second device, receive the response signal, - Calculate the distance between the devices based on the response signal.

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

13. The method according to claim 9, including the additional steps of determining whether the distance is within a predetermined limit, and establishing wireless communication if a predetermined requirement is met, the requirement including the distance being within the predetermined limit.

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