The present disclosure relates to a method performed by a traffic analyzing element 23 in a communication network in which a radio device communicates over a packet switched (PS) radio access bearer (RAB) 7 with a radio access network (RAN) using compression in uplink (UL). The method comprises measuring at least one property of radio traffic between the radio device and the RAN. The method also comprises predicting a fraction of UL data on the PS RAB which will be compressible, based on the measuring. The method also comprises outputting information about the predicted fraction to a memory size estimating element 24 in the communication network. The present disclosure also relates to a method performed by a memory size estimating element, as well as to a memory size estimating element and a traffic analyzing element.