A radio communication system comprises a secondary station having a communication channel with a primary station for the transmission of data packets from the primary station to the secondary station. In response to receipt of a data packet, the secondary station transmits a combined acknowledgement and quality parameter signal (402) to the primary station. The signal (402) indicates whether the data packet was received correctly and the value of the quality parameter enables the primary station to select transmission parameters for further data transmissions. A range of formats for the combined signal are possible.In one embodiment the quality parameter is a site selection signal indicating a preferred subset of primary stations for subsequent data transmissions. In another embodiment the quality parameter relates to the quality of the radio link and enables the primary station to select suitable modulation and coding schemes and/or transmit power levels.