Spatially located ultrasound beacons are provided in known locations within a distributed communication system. The ultrasound beacons are configured to emit ultrasound pulses that can be received by client devices in ultrasound communication range of the beacons. The client devices are configured to analyze the received ultrasound pulses from the beacons to determine their time-difference of arrival and as a result, their location(s) within the distributed communication system. The client devices comprise inertial navigation systems (INS) that calculate client device location as the client device moves, and when received ultrasound signals are below a predefined threshold.

An underwater positioning system for accurate underwater positioning. At least one among at least one acoustic transmitter and at least one hydrophone is provided at known coordinates and which positions an unknown point having unknown coordinates at which another acoustic transmitter or hydrophone is provided, includes a time window that stores in advance, when the unknown point is set in a plurality of regions set by dividing an underwater positioning range, a time window for a sound wave emitted from the acoustic transmitter to reach the hydrophone for each of the regions, and a coordinate estimation and specification unit that calculates for each of the regions a time window-applied impulse response as an inner product of the time window and an impulse response of a sound wave propagation path from the acoustic transmitter to the hydrophone and estimates that the unknown point is located in the region where the energy of the time window-applied impulse response is maximized.

A location position system can include a plurality of beacons arranged a grid formation divided into a plurality of sub-grids. A mobile computing device can implement a location position application and can receive a radio signal from a particular beacon of the plurality of beacons. The radio signal can comprise a data component uniquely identifying the particular beacon, which can be used to identify a particular sub-grid of the plurality of sub-grids. An audio signal can be received from each of a set of sub-grid beacons associated with the particular sub-grid. Each audio signal can: (i) have a frequency in the frequency range of 16 kHz to 24 kHz and a transmission delay from a reference time, (ii) lack any additional identifying data, and (iii) be separately transmitted from the radio signal transmitted by the particular beacon. The mobile computing device can determine its position based on the received audio signals.

A location position system can include a plurality of beacons arranged a grid formation divided into a plurality of sub-grids. A mobile computing device can implement a location position application and can receive a radio signal from a particular beacon of the plurality of beacons. The radio signal can comprise a data component uniquely identifying the particular beacon, which can be used to identify a particular sub-grid of the plurality of sub-grids. An audio signal can be received from each of a set of sub-grid beacons associated with the particular sub-grid. Each audio signal can: (i) have a frequency in the frequency range of 16 kHz to 24 kHz and a transmission delay from a reference time, (ii) lack any additional identifying data, and (iii) be separately transmitted from the radio signal transmitted by the particular beacon. The mobile computing device can determine its position based on the received audio signals.

An acoustic model determination approach for a real-time locating system is disclosed. The system includes one or more transmitting devices and one or more mobile devices. The acoustic model may be determined by deriving an acoustic representation of sub-structures within the building, and then forming the acoustic model based on the acoustic representation and the location and orientation of the static acoustic transmitting device. In another embodiment, an acoustic signal is transmitted from a static acoustic transmitting device, with the reflected signals received by the same static acoustic transmitting device in a receiving mode. Based on these received acoustic signals, the acoustic model is formed based on the reflected signals and the location and orientation of the static acoustic transmitting device.

A method and system for enabling the determination of a position of a receiver within a space includes transmitting a beacon signal from each of a plurality of beacon devices located at different locations within the space. The beacon signal transmitted from each beacon device has a unique information component and may have a unique frequency pattern of multiple frequencies. Each beacon signal can be distinguishable from the beacon signals transmitted from any other of the beacon devices based on the combination of its unique information component and its unique frequency pattern. The beacon signals are received at a receiver. At the receiver, for each beacon signal of a working subset, time-delay information of the received beacon signal is determined and multilateration is applied to determine the position of the receiver based on the location of each beacon device of the working subset.

A method and system for enabling the determination of a position of a receiver within a space includes transmitting a beacon signal from each of a plurality of beacon devices located at different locations within the space. The beacon signal transmitted from each beacon device has a unique information component and may have a unique frequency pattern of multiple frequencies. Each beacon signal can be distinguishable from the beacon signals transmitted from any other of the beacon devices based on the combination of its unique information component and its unique frequency pattern. The beacon signals are received at a receiver. At the receiver, for each beacon signal of a working subset, time-delay information of the received beacon signal is determined and multilateration is applied to determine the position of the receiver based on the location of each beacon device of the working subset.