Hybrid GSM/WLAN loose/tight coupled system

General Packet Radio Service (GPRS) is marked as the 2.5G generation of wireless service and it can provide data communication with low data rate and wide area coverage. Wireless Lan (WLAN) is recently spreadly used another wireless technology with very high datarate and small area coverage; normally just exist in "HOTSPOT". In this thesis we investigate the co-existence of Wireless LAN (802.11) and GPRS system. Based on the network coupling structure between the two access technologies, i.e. wireless LAN and GSM, the concept of joint radio network built on the reference structure is briefly introduced. Mobile IP is used to achieve the seamless roaming between the coupled networks. This research uses C++ based simulation to design and to test the performance of the coupling networks. Two main network scenarios are considered, such as increasing the AP existence probability with fixed tight and loose coupling ratio and increasing tight/loose coupling ratio with fixed AP existence probability. By combining these two main network scenarios with different traffic load, we can get different performance results. The results show that the wireless LAN can be very effective in complementing GSM cellular system