A mobile station for use in a radio telephone network, the radio telephone network comprising a base station subsystem and a plurality of mobile stations for communicating with the base station subsystem and in which radio signal transmission slots at a mobile station are synchronised to radio signal reception slots at the base station subsystem to account for a propagation delay between the mobile station and the base station subsystem, the reception slots corresponding to uplink and/or downlink user data packet switched transmission channels allocated dynamically by the base station subsystem, the mobile station being configured to: receive a timing advance value once, from the base station subsystem to the mobile station, and to; advance transmission slots at the mobile station for both the uplink and downlink channels using the received timing advance value so that transmitted data is received at the base station subsystem in the allocated base station subsystem reception slots. view more