A system for synchronizing communications in a radio ranging process involves transmitting calibration signals according to a predetermined schedule of nominal transmission times. Timing offsets are determined. A start time is determined for a transmission of a ranging signal. The start time is earlier than a nominal start time of the ranging signal by at least the largest timing offset. Another system for synchronization involves a radio device transmitting a calibration signal to a second radio device and receiving a calibration response signal from the second radio device. A time-of-flight value is determined in dependence on a time of departure of the calibration signal and a time of arrival of the calibration response signal. A ranging signal is transmitted at a time determined in dependence on the determined time-of-flight value. A ranging response signal is received and processed to determine a range value.