An apparatus is configured to, based on a first signal comprising one or more data transmission frames received from a first radio device by a second radio device. The first signal has a particular carrier frequency of a carrier wave thereof and the one or more data transmission frames comprising a plurality of symbols provided at a particular symbol frequency. The carrier frequency and symbol frequency based on a reference clock frequency of the first radio device. One or more of an estimate of the particular carrier frequency is determined and an estimate of the particular symbol frequency relative to a reference clock frequency of the second radio device and provide for transmission of a response signal from the second radio device to the first radio device.