In a communication system including mobile terminals and different wireless networks the mobile terminals can estimate the speed with which the mobile terminals move and communicate estimated values of the speed to a selection function (17) selecting one of the wireless networks communicating information from and to the respective mobile terminal. In the estimating, first estimated speeds and/or positions of a mobile terminal are determined (11) particularly for each of the wireless networks, from the communication with the particular wireless network. Then the estimated values are by special interfaces (11) input to a different speed estimation function (15) in which a combined value of the speed of the mobile terminal is calculated, according to a speed estimation algorithm and is input to the selection function. In this speed estimation also a recommended one of the wireless networks can be determined. The functions for estimating the speed are divided between a network layer (L3) and lower layers (L2, L1).