Cloud voice service for seamless roaming in heterogeneous networks

Today´s heterogeneous networks are still in growing progress with the current introduction of Long Term Evolution. Despite the given infrastructure, hardly any service provider offers seamless voice call services due to the high integration cost. For addressing this issue, we introduce a feasible Virtual Room based Vertical Handoff (VOOH) cloud solution that only applies latest existing wireless access technologies (UMTS, LTE, WiFi) for connectivity purposes. Therefore, VOOH does not require any changes in the underlying network layers that result in low integration effort. Moreover, this solution uses the circuit-switched instead of packet-switched channel of UMTS to guarantee QoS for calls while handing over seamlessly from VoIP (via LTE or WiFi) to UMTS. Besides introducing the VOOH concept and its communication procedure, we present an analytical three-dimensional Markov model for performance evaluation that is validated by our developed event-discrete simulation model. Based on this model, a scalable and cost-effective design of VOOH as cloud service for specific use case examples and the obtained findings are discussed. The results presented in this paper illustrate that an enhanced VOOH (eVOOH) solution improves the VOOH performance up to 56% and thus allows to further minimize economic costs.