Mobile-based positioning using assistance data provided by onboard micro-BSA

A method for estimating position of a mobile device, the method comprising:

• receiving, from a base station almanac (BSA) associated with a network server, observed time difference of arrival (OTDOA) assistance data for a first plurality of cells;
• storing, within a memory of the mobile device, the OTDOA assistance data as a first micro-BSA;
• and
• determining an initial position estimate for the mobile device based upon time difference of arrival (TDOA) measurements associated with an initial subset of the first plurality of cells and initial OTDOA assistance data corresponding to the initial subset of the first plurality of cells;
• determining an improved position estimate for the mobile device based upon TDOA measurements associated with an additional subset of the first plurality of cells and improved OTDOA assistance data corresponding to the additional subset of the first plurality of cells;
• determining additional position estimates for the mobile device based upon further improved OTDOA assistance data generated by the micro-BSA based on one or more of the additional position estimates;
• and
• assessing a quality of the additional position estimates by evaluating contours in a position estimation cost function, calculating a time difference of arrival (TDOA) residual error vector, or any combination thereof;
• wherein elements of the TDOA residual error vector correspond to selected cells of the first plurality of cells, the TDOA residual error vector being denoted by e and having the form of e=r−h({circumflex over (x)}) where r is a TDOA measurement vector for one of the additional position estimates, h({circumflex over (x)}) is a TDOA vector for a position estimate {circumflex over (x)}, and h({circumflex over (x)}) is defined using the inverse of the speed of light as a constant scaling factor;
• and
• wherein each element of r includes a TDOA measurement associated with one of the selected cells and h({circumflex over (x)}) is given by
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A mobile device, comprising:

• a processor;
• a receiver in communication with the processor;
• and
• a memory including program code that when executed by the processor causes the mobile device to perform operations including:
• receiving, over a wireless link from a base station almanac (BSA) associated with a network server, observed time difference of arrival (OTDOA) assistance data for a first plurality of cells;
• storing, within the memory of the mobile device, the OTDOA assistance data as a first micro-BSA;
• determining an initial position estimate for the mobile device based upon time difference of arrival (TDOA) measurements associated with an initial subset of the first plurality of cells and initial OTDOA assistance data corresponding to the initial subset of the first plurality of cells;
• performing a cell scan on the wireless link after storing the OTDOA assistance data for the first plurality of cells in the memory of the mobile device;
• detecting, through the cell scan, one or more cells on the wireless link that are not included in the first plurality of cells;
• and
• requesting, from the BSA associated with the network server, additional OTDOA assistance data associated with the detected one or more cells, the requesting triggered by the detection of the one or more cells.