The next generation (4G) wireless network is envisioned as a convergence of different wireless access technologies providing the user with the best anywhere anytime connection and improving the system resource utilization. The integration of wireless local area network (WLAN) hotspots and the third generation (3G) cellular network has recently received much attention. While the 3G-network can provide global coverage with a low data-rate service, the WLAN can provide a high data-rate service within the hotspots. Although increasing the underlay network utilization is expected to increase the user available bandwidth, it may violate the quality-of-service (QoS) requirements of active real-time applications. Hence, achieving seamless handoff between different wireless technologies, known as vertical handoff (VHO), is a major challenge for 4G-system implementation. Several factors, such as application QoS requirements and handoff delay, should be considered to realize an application transparent handoff. We present a novel framework to evaluate the impact of VHO algorithm design on system resource utilization and user perceived QoS. We used this framework to compare the performance of two different VHO algorithms. The results show a very good match between simulation and analytical results. In addition, it clarifies the tradeoff between achieving high resource utilization and satisfying user QoS expectations.
['Ahmed H. Zahran', 'Ben Liang']
Performance evaluation framework for vertical handoff algorithms in heterogeneous networks