Air interface switching and performance analysis for fast vertical handoff in cellular network and WLAN interworking

Abstract

The integration of wireless local area network (WLAN) hotspot and the 3G cellular networks is imminently the future mode of public access networks. One of the key elements for the successful integration is vertical handoff between the two heterogeneous networks. Service disruption may occur during the vertical handoff because of the IP layer handoff activities, such as registration, binding update, routing table update, etc. In this paper, the network interface switching and registration process are proposed for the integrated WLAN/cellular network. Two types of fast vertical handoff protocols based on bicasting and non-bicasting supporting real-time traffic, such as voice over IP, are modeled. The performance of a bicasting based handoff scheme is analyzed and compared with that of fast handoff without bicasting. Numerical results and the simulation are given to show that packet loss rate can be reduced by the bicasting during handoff scheme without increasing bandwidth on both wireless interfaces. gateway GPRS supporting nodes (GGSNs), or 3G core network switches. Generally a loosely coupled network architecture, which is shown in Figure 1, is preferred [3] due to the flexible deployment and it is the network topology considered in the paper. In the figure, WLAN and 3G cellular networks work in a complementary way, and the interworking between WLAN and 3G cellular network is through an IP network. Mobile IP (MIP) protocol [4,5] is applied to support IP mobility for mobile nodes (MNs). The MNs are provided with MIP clients and can support both 802.11 and 3G cellular access technologies. Data can be transported between two different paths, shown as dashed lines in the figure, depending on the access interface that the MN is associated with. With this loosely coupled architecture, the same WLAN can be shared by different cellular service providers who own different 3G cellular networks. The main parts of a 3G cellular network owned by each service provider are radio access network (RAN) and core network. The network has two new functional entities, the home agent (HA) and the foreign agent (FA), specifically added to support MIP. The PDSN is modified to act as a FA for the cellular network in addition to its original intended functionality. 802.11 WLANs are connected through an IP network (or the Internet) to the 3G cellular core networks. Each WLAN has its own gateway which serves as a FA for MNs within its coverage. The authentication, authorization, and accounting (AAA) server is used for authentication and authorization of WLAN users as well as 3G cellular network users. Users registered with a cellular service provider is authenticated by the AAA/ RADIUS (remote authentication dial-in user service) server at the home network, whether accessing the network through the 3G cellular network section or the WLAN section.In loosely coupled WLAN/cellular networks, seamless service continuity is desired. Seamless service continuity requires that data loss and service break time during the vertical handoff between 3G c...

VoIP over WLAN: voice capacity, admission control, QoS, and MAC

“…Moreover, packets may be dropped by the old AP during the handoff procedure, which degrades, or even disconnects the voice connections during the handoff. Optimized fast handoff scheme has been proposed and analysed in the literature [57,58]. The proposed scheme uses bicasting technique in which duplicated packets are sent to both air interfaces (cellular network and WLAN) for a short period during the handoff.…”

“…The proposed scheme uses bicasting technique in which duplicated packets are sent to both air interfaces (cellular network and WLAN) for a short period during the handoff. It is shown in Reference [57] that fast handoff with bicasting technique can significantly reduce the handoff packet losses. Currently, the 802.11k task group is working on the radio resource management to make efficient use of the WLAN resources.…”