Abstract: In a positioning system (100) for estimating the position of a mobile device (7), a processing system (9) receives external-range data, representative of a range between the mobile device and an external unit (2, 3, 4, 5), and acceleration data representative of acceleration of the mobile device due to its movement as it is carried by a person (6). The acceleration data is processed in a step-detection algorithm to determine step-distance data representative of a time series of step-data-based distances travelled by the mobile device, and step-distance data is processed to determine a step-data-based position estimate for the mobile device.

Abstract: In a positioning system, a plurality of transmitter units (2, 3, 4, 5) transmit respective transmitter-specific identification signals at intervals, which are received at a mobile receiver unit (7). A processing system (7; 9) identifies the transmitter unit that transmitted each received identification signal, and, for each signal, determines range data from time of arrival data and determines distance data from Doppler shift information. The range data and distance data are compared to determine range error data. A position estimate for the mobile receiver unit (7) is determined by solving an optimisation problem using range estimates determined for the plurality of transmitter units, weighted in dependence on the range error data.