Impact of MIMO Techniques on the Interoperability between UMTS-HSDPA and WLAN Wireless Systems

Next generation wireless communication networks integrate in a seamless manner existing technologies such as 3G wireless networks and WLANs in order to create a heterogeneous system with improved capacity and complementary coverage. Besides, they support more mobile users and a variety of services with variable bandwidth and QoS "anytime anywhere". In this paper, we first present a survey of the most recent methods that achieve interoperability between 3G and WLAN systems. Motivated by the above presented methods, we propose a mechanism that achieves interoperability between an HSDPA cellular system and a WLAN radio access network. The mechanism is based on the definition and calculation of a cost function which uses suitable metrics to trigger interoperability. The performance of the interoperability mechanism is evaluated by means of system level simulations, assuming that both HSDPA and WLAN are enhanced with MIMO space-time coded techniques. Extensive simulations have shown that the incorporation of MIMO schemes greatly affects the inter-system handovers while significant performance enhancements can be achieved at the system level.