A cellular communication system comprises a media gateway (111) which interfaces between a packet switched network (113) and a circuit switched network (115). The media gateway (111) time aligns received packet data in response to timestamps of these. Each of first and second RNC (105, 109) comprise a Node B interface (201) which receives real time data being data of an air interface communication from the remote station (101) to a base station (103, 107) supported by the RNC (105, 109). A packet processor (203, 205) then transmits the data packets to the media gateway (111) via the packet switched network (113). A timestamp processor (207) determines timestamps for the data packets in response to a timing characteristic of the air interface communication.