Handoff vertical entre reseau UMTS et WLAN

One of the major challenges for next generation for the wireless communication systems is to use the limited resources of communication networks effectively to provide quality and capacity that are sufficient for the growing need of bandwidth and the ability to provide all sorts of value added services.;The objective of this Master thesis is to study and combine techniques of mobility management to exploit the advantages of both networks: cellular (UMTS) and wireless LAN (WLAN) and can integrate these two technologies so that the change in technology is transparent.;The first part of this thesis, particular aspects of mobility management will be discussed. Heterogeneous UMTS/WLAN network can be interconnected in three different ways; two particular architectures will be discussed. Furthermore, different hand-off algorithms will be discussed, such as RSS algorithm, SNR and SINR.;Most contributions in this context take into account just the maximization of throughput across both UMTS and WLAN networks, but not much research was done on minimizing the number of handoffs during a call or data transfers. This plays an important role to avoid unnecessary handoffs and eliminate the ping-pong effect which degrades the quality of service.;The bandwidth requirements of users have increased due to new applications such as video and Internet browsing. This has enabled many emerging technologies that are constantly improving to meet the needs of users. This is particularly the case of heterogeneous networks used to interconnect various networks such as WiFi, GSM/UMTS and Satellite. These networks will help meet user's needs by offering them cheaper bandwidth, higher mobility, and more reliable networks.;Hence, in the second part of the thesis, a new integrated strategy for achieving vertical handoffs is proposed for mobile users between the two networks while minimizing the number of handoffs. This solution will lower the packets lost in the network. It will also achieve greater throughput and transfer rates, while the cost remains lower. In this context we present and we test several handoff algorithms, and we compare these algorithms with our proposed solution. All algorithms have been validated and evaluated by simulations.;Keywords: Heterogeneous networks, UMTS, WLAN, vertical handoff, ping-pong effect.