WLAN call admission control strategies for voice traffic over integrated 3G/WLAN networks
Alessandro Bazzi, M. Diolaiti, Claudio Gambetti, Gianni Pasolini · 2006
Heterogeneous networks integration and interwork- ing, with particular reference to third generation (3G) cellular networks and wireless local area networks (WLANs), is a challenging issue for the early future wireless communications world. In our researches we consider the opportunity to convert those circuit switched voice flows that would be blocked by UMTS for resource saturation into voice over IP streams to be served through the WLAN connection. In order to increase voice users satisfaction when WLAN available resources are critically falling off, in this paper we investigate, by means of a simulation approach, different WLAN call admission control strategies within the context of 3G-WLAN integrated networks. I. INTRODUCTION Heterogeneous networks integration and interworking, with particular reference to third generation (3G) cellular networks and wireless local area networks (WLANs), is a challenging issue for the early future wireless communications world. Provided that the WLAN hot spot is within the 3G network coverage and that the final user is equipped with a dual mode terminal, integrating the two technologies, thus increasing the pool of available resources, would considerably increase both users satisfaction and networks utilization efficiency. In the last few years several projects were dedicated to the issue of 3G/WLAN interworking networks (e.g., (1)) and many papers appeared, investigating specific aspects mainly related to architectural/signalling issues (e.g., (2)) and vertical handover (e.g., (3)). Besides the data users exchange between UMTS and WLAN, in this paper we focused our attention on the possi- bility to serve by means of the WLAN technology those voice calls that within the hot spot region cannot be served by the 3G network (and would therefore be blocked) in case of saturation of its radio resources. Obviously a format conversion from circuit-switched (CS) voice flows into packet-switched (PS) Voice over IP (VoIP) flows (and vice versa) is needed in order to allow the radio network switching (see (4) for details on the network architecture). The benefits of 3G/WLAN interworking are here inves- tigated with reference to the Chinese TD-SCDMA UMTS This work was carried out in the framework of VICOM Project funded by MIUR. technology (5) and to the upcoming IEEE802.11e (6) WLAN technology. In this paper, in particular, the users satisfaction level provided in a realistic scenario by the integrated network is assessed by means of a dedicated simulation platform. Three simple but effective call admission control (CAC) strategies for the WLAN are implemented in our simulation platform in order to prevent WLAN overloads. Their performance have been derived and compared. The paper is outlined as follows. In section II the WLAN CAC strategies are described, in section III the scenario under investigation is introduced; in section IV and in section V the simulations settings and the related numerical results are reported and finally, in section VI the final conclusions are drawn.