Seamless handover between WLAN and UMTS

One of the most important aims of next generation mobile communications systems (systems beyond 3G) is to achieve the inter-operation of heterogeneous networks such as WLAN, 3G and digital video broadcasting (DVB). Interworking among these networks would allow network operators to cooperate to provide new value added services which they could not individually provide in a satisfactory manner. These services should be provided in a cost effective, reliable and secure manner. The paper addresses handover between WLAN and UMTS. We propose a network architecture, and address seamless handover issues from the user´s point of view. Moreover, the paper explains how two popular mobility protocols (SIP and Mobile IP) may each be deployed in this scenario. Performance of SIP and Mobile IP in similar situations are compared, in consideration of network characteristics such as available bandwidth (throughput), overhead, end-to-end delay, latency and packet lost rate. Finally, alternative solutions such as SIP-based approach, hybrid solution, integrated solution and multilayer solution are examined and compared.