Cloud voice service as over-the-top solution for seamless voice call continuity in a heterogeneous network environment

Despite the current introduction of the 4G mobile network technology Long Term Evolution (LTE) and the existing heterogeneous network infrastructure, hardly any service provider supports seamless cloud voice service owing to the high integration cost.In order to address this challenging issue, we present a cost-effective Virtual Room based vertical handoff (VOOH) as an Over-the-top (OTT) solution, which is network provider independent and only uses existing wireless access technologies (e.g., LTE, 2G/3G, WiFi) for connectivity purposes. That means no changes in the underlying network technologies are required that result in lower integration effort. Besides providing handoff of ongoing Voice over IP (VoIP) calls seamlessly between WiFi and LTE, unlike related solutions (e.g., Circuit-Switched Fall Back (CSFB)) VOOH presents a cost-effective OTT solution to support voice call continuity between LTE and the circuit-switched channel of 2G/3G networks. In the long term, VOOH also enables data-offloading (e.g., via WiFi) to lower the traffic load of cellular base stations.While our previous work has mainly focused on proof of concepts and experimental performance evaluations, this manuscript proposes a novel analytical and simulation model to analyze the scalability of the VOOH solution that is discussed for specific use case examples. Moreover, the impact of an enhanced VOOH (eVOOH) approach is presented to improve the system performance in terms of blocking probability. Based on the validated models, the results illustrate that eVOOH outperforms the original solution that is shown by lower call blocking probabilities.