In telecommunications systems, a plurality of User Equipment (UEs) communicate with a common station via communication signals which have a system frame format. Commonly used time slots (CUTSs) are available for common use by the UEs for transmitting code identified signals for a specific uplink channel. The UEs select a code identifier from a plurality of identifiers, such as midambles. A UE transmission with a selected code identifier in a selected CUTS will fail if another UE transmits with the same code identifier in the same CUTS or if the UE transmission lacks sufficient power. Communication efficiency is enhanced by determining the number of successful and failed UE transmission in CUTSs per frame and adjusting one or more communication parameters in response to said determination such as a parameter upon which the UEs determine an access rate for transmitting in CUTSs and/or a power control parameter.