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The fourth-generation (4G) (Liu, 2004) system is expected to support fully integrated services and ubiquitous access anytime and anywhere. Instead of developing a new uniform standard for all wireless communication systems, some endeavors in 4G research focus on the seamless integration of various existing wireless communication networks, such as integrated Wireless LAN (WLAN) and the third-generation (3G) cellular networks. 3G cellular networks provide wide coverage and universal roaming services with limited data rate up to 2 Mbps (Liu, 2006, 2007). With careful network planning and mature admission control algorithms, the achievable Quality of Service (QoS) level of 3G cellular networks is relatively high. On the other hand, WLANs provide low-cost, high data rate wireless access within limited hotspot-area. Since WLAN is originally designed for besteffort data services with contention-based access, it is difficult to achieve strict QoS provisioning for real-time services, such as voice service (Song et al., 2006). Due to different network capacities, user mobile patterns, vertical handoffs, and QoS levels, the integrated WLAN and 3G cellular networks require a new call admission control scheme to provide QoS provisioning and efficient resource utilization. Currently there are three major architectures for internetworking between 3G cellular cellular networks and WLAN (Ahmavaara et al., 2003). But they are all lack of joint resource management and admission control schemes in integrated environment. Previous research work on admission control in homogeneous cellular networks and heterogeneous integrated networks are investigated with technical descriptions on their pros and cons. It is shown that more endeavors are needed on joint congestion control, load balance, and high-level QoS provisioning in integrated networks. In this chapter, a novel joint call admission control (CAC) scheme is proposed to support both voice and data services with QoS provisioning. Due to different network service characteristics, 3G cellular network is defined to be a voice-priority network where voice services have higher priority for resource allocation than data services, while WLAN is defined as data-priority network where data services have higher priority than voice services. A joint call admission policy is derived to support heterogeneous network architecture, service types, QoS levels, and user mobility characteristics. Furthermore, to relieve traffic congestion in cellular networks, an optimal channel searching and replacement algorithm and related passive handoff techniques are further developed to balance total system traffic

Joint Call Admission Control in Integrated Wireless LAN and 3G Cellular Networks