For supporting a satellite based positioning of a mobile arrangement (30,40) with assistance data, a communication network converts parameters of a dedicated orbit model describing a movement of a satellite (50,60), which dedicated orbit model is defined for a particular satellite based positioning system, into parameters of a common orbit model describing a movement of a satellite (50,60). Alternatively or in addition, the network replaces a reference value that is based on a satellite based positioning system time in available parameters of an orbit model by a reference value that is based on a communication system time. After the parameter conversion and/or the reference value replacement, the parameters are provided as a part of assistance data for the satellite based positioning.