In this paper, we analyze the performance of vertical handover (VHO) algorithms for seamless mobility between WiFi and UMTS networks. We focus on a no-coupling scenario, characterized by the lack of any form of cooperation between the involved players (users and network operators). In this “hostile” scenario, the VHO operations are completely operated by the mobile terminal (MT), and the network authentication procedures are unoptimized, leading to typically long handover times. In this context, we ﬁrst propose a low-complexity Received Signal Strength Indicator (RSSI)-based algorithm and, then, an improved hybrid RSSI/goodput version. We present experimental results based on the implementation of a real testbed with commercial WiFi (Guglielmo) and UMTS (Telecom Italia) Italian deployed networks. Despite the relatively long handover times experienced in our testbed, the proposed RSSI-based VHO algorithm guarantees an eﬀective goodput increase at the MTs. Moreover, this algorithm mitigates the ping-pong phenomenon. Our results show that, by using simple MT-driven VHO mechanisms, the users can beneﬁt from redundant and heterogeneous wireless network infrastructures. This can be done by leveraging on pre-existing commercially deployed networks, without the need for any modiﬁcation of them.
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