A method of transmitting voice over IP (VoIP) in a wireless telecommunications system comprising at least one wireless mobile station, a first radio access gateway and a second radio access gateway. Address information of the second radio access gateway is defined in the first radio access gateway, if a need is detected to hand over the connection of the mobile station from a base station connected to the first radio access gateway to a base station connected to the second radio access gateway. Address information of the first radio access gateway is defined in the second radio access gateway. Data addressed to and transmitted from the mobile station is transferred through the first radio access gateway and the second radio access gateway when the handover has been performed to the base station connected to the second radio access gateway.