Nowadays wireless networks, mobile terminals (MTs) and Internet applications are rapidly evolving. Traditional circuit-switched cellular networks like GSM are gradually shifting towards packet-switched networks like GPRS, UMTS, etc. In addition, recent years have also witnessed rapid emergence and growth of diverse wireless access technologies like WiFi, WiMAX, Bluetooth, DVB-H, etc. All these technologies that coexist and overlap in coverage/deployment are thus resulting in heterogeneous wireless environments, where the common desire to be connected "anytime, anywhere, anyway, and to anything" leads to explosive growth of mobile computing and novel mobile Internet applications like VolP, multimedia conferencing, etc., and rapid evolution of traditional single-mode MTs towards being multimodal. It is obvious that users would always want the best available services in accordance with their preferences and application requirements, while roaming across heterogeneous wireless networks. Thus, the necessity of convergence of diverse wireless access technologies comes forth.The key objective ofthis research work is to overcome new challenges that the coexistence of heterogeneous wireless networks would put forth and rather eventually produce a synergy.