The disclosure relates to a range-classifying-module for a radio receiver, the range-classifying-module configured to: receive a signal representative of a chirp from a transmitter, determine the presence of one or more pulses in the received signal; and classify the receiver as either proximal to or distal from the transmitter based on: one or more characteristics of the one or more pulses; in addition to a time-of-arrival of the one or more pulses.