Time of flight between two or more ultrasonic transceivers is measured using known delays. First and second transceivers are duty cycled, each having a respective receive period that is less than a measurement period during which the transceivers are configured to receive transmissions. An ultrasonic trigger pulse is transmitted by the first transceiver. The second transceiver, upon receiving the trigger pulse, transmits an ultrasonic response pulse after a first predefined delay time that is known to the first transceiver and greater than the receive period of the second transceiver. Subsequently, the first transceiver receives the ultrasonic response pulse and determines a receive time. The first transceiver determines the distance between the first transceiver and the second transceiver from a speed of sound, an elapsed time between the time of transmission of the trigger pulse and the receive time, and the first predetermine delay time.

A wearable device is described that is configured to alert a subject prior to encountering an obstacle. The subject may be visually-impaired. The device includes: a mobile transceiver tag adapted to be worn by a subject within a designated area (e.g., a swimming pool); three or more stationary transceiver beacons in spaced apart, fixed positions; a wearable signal output device (e.g., headset); and a processor with software that can calculate the subject's position relative to one or more obstacles (e.g., end of swimming lane) and sends a left, right, or reverse signal to the signal output device.

According to certain examples, a circuit-based wireless communications system provides secure access to a vehicle by way of certain circuitry configure to compare a first RF background observed for a vehicle-located RF receiver that is part of a vehicle-located circuit secured to a vehicle, with a second RF background observed for a wireless-communications vehicle-access circuit that includes another RF receiver. In response, a distance metric is generated to indicate a degree of similarity between the first RF background and the second RF background, and based on whether this metric satisfies a threshold, access to the vehicle may be granted via the wireless-communications vehicle-access circuit.

The ultrasonic navigation system uses a root node and extended nodes to transmit and receive ultrasonic signals. The root node is attached to the object to be tracked, i.e., the collar of a pet, a robotic cleaning device, etc. The ultrasonic wave originates from the root node and may include a transmitter; it monitors when it initially sends each signal. The system sends several signal pulses simultaneously so that it can measure distances more effectively. The signals travel from the root node to each extended node (at least three) where they are received, respectively, and each extended node sends a timestamp of when it received the pulse, respectively. These extended nodes are placed around a boundary of a confined area. When the root node emits a signal, it bounces back from all of the extended nodes on the perimeter allowing for continuous and accurate measurement of any space.

A method for finding door location in an automated way based on observations of people that are equipped with a device whose position is determined acoustically. By observing positioning transitions across internal structures such as walls, the location of doors can be automatically identified.

A method for geolocating a mobile computing device within an indoor environment. One embodiment may comprise generating a geolocation request audio signal by a speaker of a first device starting at a first point in time, receiving, by a microphone of the first device, a reply audio signal from a second device, and extracting, by one or more processors of the first device, information encoded in the reply audio signal. The method may further comprise estimating, by the one or more processors, a receipt time by the first device for the reply audio signal and calculating a first time of flight (TOF) using the first point in time and the estimated receipt time for a second audio signal. The first device may comprise a smartphone and the second device may comprise a beacon located at a known location in an indoor environment.

A system for tracking an instrument with ultrasound includes a probe (122) for transmitting and receiving ultrasonic energy and a transducer (130) associated with the probe and configured to move with the probe during use. A medical instrument (102) includes a sensor (120) configured to respond to the ultrasonic energy received from the probe. A control module (124) is stored in memory and configured to interpret the ultrasonic energy received from the probe and the sensor to determine a three dimensional location of the medical instrument and to inject a signal to the probe from the transducer to highlight a position of the sensor in an image.

A system for tracking an instrument with ultrasound includes a probe (122) for transmitting and receiving ultrasonic energy and a transducer (130) associated with the probe and configured to move with the probe during use. A medical instrument (102) includes a sensor (120) configured to respond to the ultrasonic energy received from the probe. A control module (124) is stored in memory and configured to interpret the ultrasonic energy received from the probe and the sensor to determine a three dimensional location of the medical instrument and to inject a signal to the probe from the transducer to highlight a position of the sensor in an image.

A method of determining a range between two devices, which can for instance be wireless devices, such as handheld devices. The method performs a double-sided two-way ranging protocol at the two devices. This protocol causes the two devices to transmit and receive signals, with a view to determining the range between the two devices, using a two-way ranging methods, where each of the signals is a composite tone generated as a composition of two waveforms that are timewise separated by a gap to form a bipolar waveform. The gap is a zero or low-amplitude signal, contrasting with the two waveforms. The particular pattern in the correlation footprint eases the determination of the time of flight. The method can be used to measure social distancing.

A method, performed by an electronic device, of determining a location of an external device includes: receiving a trigger signal, which is output at a first location; receiving, after the trigger signal is received, a first chirp signal transmitted from a first external device among at least one external device present at a different location from a location of the electronic device, the first chirp signal being transmitted according to the trigger signal being received by the first external device; obtaining, based on a time point at which the first chirp signal is received, a difference value between a time point at which the trigger signal is received by the electronic device and a time point at which the trigger signal is received by the first external device; and determining a location of the first external device based on the difference value.