Cost-effective and feasible VOOH solution for seamless service roaming

Vertical handoff (VHO) is the key factor for seamless voice calls in today's heterogeneous networks, but due to the high technical and economic cost of such VHO technologies, barely any service provider currently offers those voice services. To address this issue and to offer full area-covering for calls, we present a feasible and cost-efficient Virtual Room based Vertical Handoff (VOOH) solution. Moreover, our approach simplifies the handling of telephone numbers, protects the privacy of called parties, and requires no changes on existing wireless access networks. Besides, VOOH does not violate contract agreements of most commercial network providers. Instead of the packet switched channel, VOOH uses the circuit switched channel of UMTS for calls in case of handoff from WLAN to UMTS. To investigate the impact of Direct Call Function on VOOH performance, we design an enhanced VOOH (eVOOH) solution. Based on a developed and comprehensive Markov model, the system performance of both solutions (i.e., VOOH and eVOOH) is compared under different traffic loads. The results illustrate that eVOOH performs up to 42.46% better than VOOH.