Joint Call Admission Control in Integrated Wireless LAN and 3G Cellular Networks
Chunming Liu, Chi Zhou, Niki Pissinou, S. Kami · InTech eBooks · 2011
IntroductionThe 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(Liu, , 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 www.intechopen.comRecent Advances in Wireless Communications and Networks 190 between WLAN and 3G cellular network, as well as to reduce average system QoS cost, such as system blocking probability.A one-dimensional Markov model for voice service is also developed to analyze interworking system performance metrics.Both theoretical analysis and simulation results show that average system QoS costs, such as overall blocking and dropping probabilities, are reduced, and our scheme outperforms both traditional disjoint static CAC scheme and joint CAC without optimization. Technical backgroundThis section briefly describes concepts, architecture and vertical handoffs in integrated WLAN and cellular networks. Architecture of integrated WLAN and 3G cellular networksDriven by the anywhere and anytime mobile service concept, it is expected that 4G wireless networks will be heterogeneous, integrating different networks to provide seamless Internet access for mobile users.The integrated WLAN and 3G cellular network takes advantage of the wide coverage and almost universal roaming support of 3G cellular networks and the high data rates of WLANs.Currently, there are three major architectures for internetworking between 3G Universal Mobile Telecommunications System (UMTS) cellular networks and IEEE 802.11WLAN.These are Open Coupling, Tight Coupling, and Loose Coupling (Liu, 2006).The Open Coupling architecture specifies an open standard and is used for access and roaming between 802.11 WLAN and UMTS networks.In this approach, both networks are considered as two independent systems that may share a single billing scheme between them.An 802.11WLAN is connected to the Internet through a Gateway Router, and UMTS network, is connected to the Internet through a Gateway GPRS Support Node (GGSN).Open Coupling scheme is lack of supports for mobility, resource management, QoS provisioning, and security in integrated environment.As a direct integration scheme, Tight Coupling connects the WLAN network to the rest of the core network in the same manner as other cellular radio access technologies (Liu & Zhou, 2005a, 2005b; Liu, 2006).As shown in Fig. 1, the WLAN gateway router hides the details of the WLAN from the 3G UMTS core network by adding a new component, SGSN emulator, into WLAN.The SGSN emulator connects the gateway router in the WLAN to the IP core network.It interconnects the UMTS core network at the G n interface (Liu, 2006), and implements all UMTS protocols required in a 3G radio access network.In terms of UMTS protocols, the WLAN service area works like another SGSN coverage area to the UMTS core network.As a result, all the traffics, including data and UMTS signaling, generated in the WLAN are injected directly into the UMTS core network through the SGSN emulator.This increases the traffic load of the UMTS core network.If the operators of the WLAN are different from those of UMTS network, the new interface between the UMTS and the WLAN can cause security weaknesses.In addition, the WLAN cards in client devices must incorporate the UMTS protocol stack, and Universal Subscriber Identity Module (USIM) authentication mechanism must be used for authentication in the WLAN (Liu & Zhou, 2005a).In contrast to high cost of Tight Coupling, the Loose Coupling is an IP-based mechanism, and approach separates the data paths in the 802.11WLAN and 3G cellular networks (Liu, 2006).The 802.11 WLAN gateway routers connect to the Internet, and all data traffic is www.intechopen.com How to referenceIn order to correctly reference this scholarly work, feel free to copy and paste the following: Chunming Liu, Chi Zhou, Niki Pissinou and S. Kami Makki (2011).Joint Call Admission Control in Integrated Wireless LAN