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 for 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 the 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.