There is disclosed devices and methods of operating a first device to determine a distance, between it and a further device, the methods comprising: transmitting a first broadcast frame comprising an identifier and a transmission timestamp; receiving a further broadcast frame, the further broadcast frame comprising an identifier of the further device, and a transmission timestamp of the further device, and at least one data pair comprising a transmitting device identifier and a reception timestamp, wherein the reception timestamp is indicative of the arrival time, at the further device, of a prior broadcast frame broadcast from the transmitting device; determining a reception timestamp of the further broadcast frame; comparing each transmitting device identifier with the identifier of the first device; and determining the distance between the first device and the further device.