Connectivity Support in Heterogeneous Wireless Networks

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Recent advances in wireless technology and decreasing costs of portable devices strongly contributed to increase the popularity of mobile communications. Wireless communication and device integration have lead to the so-called nomadic computing (or mobile computing) where portable devices (such as laptop and handheld computers) allow users to access Internet and data on their home or work computers from anywhere in the world. Multimedia services requirements nowadays encompass not only large bandwidths, but also on-the-move facilities. Future 4th generation wireless communications systems will provide seamless mobility support to access heterogeneous wired and wireless networks (Makhecha & Wandra, 2009), (Lin et al., 2010). Emerging and pre-existing wireless technologies exhibit different characteristics, access technologies, available services and network performances. For example GSM, UMTS, WLAN and WiMAX have different bandwidth (70 Mbps for WiMAX and 9.6 kbps for GSM), cell diameter ( 50 km in LoS for WiMAX and 100 m for WLAN), or handover latency (3 s for WLAN and 50 μs for WiMAX). The increasing demand for services with high QoS requirements and novel mobility scenarios, like on-the-move business users, home and office networks, on-the-move entertainment, info-mobility etc., provide users to be connected to the Internet anytime and anywhere, as well as user services and connectivity be maintained, and kept alive. Mobility management in heterogeneous networks is the essential support for roaming nomadic devices switching from one access technology to another, at the same time maintaining seamless connectivity at high QoS services (i.e. video-streaming). New emerging multimode mobile devices are equipped with multiple wireless network interface cards, providing Vertical Handover capability to autonomously select the best access network. The design of innovative handover mechanisms —sometimes called as handoff— between heterogeneous mobile devices (e.g. PDA, laptop, smart phones) and seamless integration of different integrated network (e.g. GSM, UMTS, HSDPA, GPS, WLAN, Bluetooth and so on) is an open research issue.