1. A method for indoor positioning, executed by a processing unit of a first reference node, comprising: listening to a plurality of first broadcast signals of a plurality of second reference nodes; obtaining a plurality of first signal measurements of the first broadcast signals; obtaining identification information from a plurality of broadcast messages sent by the second reference nodes; obtaining a first distance associated with each identification information; and updating a first MLM (Machine Learning Model) according to the first signal measurements and the first distances, wherein the first MLM describes a linear function between signal measurements and distances.