Latent oscillator frequency estimation for ranging measurements

A computer-implemented method for determining location of objects in a space, each object is equipped with a wireless transceiver and transmits messages amongst the objects via the wireless transceiver, comprising:

• modeling a system of objects using a factor graph having a plurality of variable vertices interconnected by a plurality of factor vertices, where a given variable vertex in the factor graph represents a location of a particular object at a given time and another variable vertex corresponding to the given variable vertex represents frequency of an oscillator driving the wireless transceiver of the particular object;
• modeling location of a particular object over time as a chain in the factor graph and modeling frequency of an oscillator over time as a chain the factor graph;
• constraining location estimates using range factors, where range factors are represented by factor vertices that interconnect location vertices and frequency vertices a given variable vertex to another variable vertex corresponding to the given variable vertex and representing frequency;
• computing by a given object, time of flight for each of a plurality of transmissions between the given object and objects in the space from which transmissions are received by the given object;
• and
• estimating, by the given object, location of the objects in the space using the computed time of flight values for the plurality of transmissions and the factor graph.