Method to attain simultaneous transmission in a cellular radio communication system comprising at least one central node (RNC1, RNC2), a first and a second asynchronous base station (BS1, BS2) being connected to a particular central node, and a mobile station (MS1, MS2) communicating data packets (DP - DP) in data frames (DF - DF) of a pre-determined duration (Tf) with said first base station serving a home cell utilizing a first downlink dedicated channel and also during soft handover communicating with said second base station serving a target cell utilizing a second downlink dedicated channel, said home and target cells being associated with a first common downlink control channel (CDCH1) and a second common downlink control channel (CDCH2) respectively, where the mobile station (MS1, MS2) measures and reports to said particular central node a frame offset value between said first downlink dedicated channel of said home cell and said second common downlink control channel (CDCH2) of said target cell, and said particular central node based on said frame offset value calculates a timing advance value needed in said target cell between a frame structure of said second downlink dedicated channel and a frame structure of said second common downlink control channel (CDCH2), characterized in that said particular central node further calculates based on said timing advance value a downlink channel offset value for the second downlink dedicated channel in the target cell needed when numbering data frames on said second downlink dedicated channel, and informs said second base station of said calculated timing advance value and said calculated downlink channel offset value and thus provides aligned transmission timings between the dedicated channel frame structures in said target and home cells, comprising the steps of: Sending a set of data packets (DP -DP) from the particular central node to the first and the second base station respectively, and Sending system frame counter states from the particular central node to the base stations, Generating local frame counter states in each base station based on said system frame counter states, Associating in the second base station each data frame with a particular frame number derived from the local frame counter states of the second base station, wherein a first data frame, within a time equal to the downlink channel offset value is assigned a first frame number, whereby said first and second base stations (BS1, BS2) starts transmission of said data packets on said first and second downlink dedicated channels respectively after having synchronised the data frame numbering on the second downlink dedicated channel with the frame numbering on the first downlink dedicated channel. Sending a set of data packets (DP -DP) from the particular central node to the first and the second base station respectively, and Sending system frame counter states from the particular central node to the base stations, Generating local frame counter states in each base station based on said system frame counter states, Associating in the second base station each data frame with a particular frame number derived from the local frame counter states of the second base station, wherein a first data frame, within a time equal to the downlink channel offset value is assigned a first frame number, whereby said first and second base stations (BS1, BS2) starts transmission of said data packets on said first and second downlink dedicated channels respectively after having synchronised the data frame numbering on the second downlink dedicated channel with the frame numbering on the first downlink dedicated channel.