A communications system for providing a user's mobile station (MS) with an Internet Protocol (IP) connectivity, has an IP network gateway for allocating an IP address to the MS to enable it to access an IP network. First and second base stations are respectively configured to support communications of the MS over first and second radio access networks using different radio access technologies. A first access gateway provides an interface between the IP network gateway and the first radio access network, whereas a second access gateway provides an interface between the IP network gateway and the second radio access network. A handover interface is provided between the first access gateway and the second access gateway for enabling the MS to switch between the first and second radio access networks with minimum latency.