WiFi mobility framework supporting GPRS roaming: Design and implementation

To provide IP mobility for wireless users several micro-mobility protocols are currently available. These are capable of supporting this feature inside the scope of a LAN, by means of performing handovers between adjacent WiFi radio-access cells in order to follow users' movements. Also, it is possible to achieve wireless mobility in a larger extent, i.e. across whole network domains. But, in order to do it these protocols have to be used in conjunction with a macro-mobility protocol, like Mobile IP. In this context, a problem arises if such domains are so far away from each other that wireless-access gaps exist between them. In fact, this prevents wireless IP users from experiencing access continuity while traveling across these domains. In this paper we describe a solution which was designed and implemented to cope with the above problem. Starting from the Cellular IP protocol, we developed a new mobility framework that extends it to seamlessly manage roaming into GPRS access network, whenever the mobile host is out of range from any WiFi domain. Also, management of inter-domain macro-mobility is integrated in our framework, eliminating the need to externally rely on Mobile IP.