O-Sok Song

A seamless handoff scheme for UMTS-WLAN interworking

In this paper, we present a practical UMTS-WLAN interworking architecture based on 3GPP standards, and propose a seamless handoff scheme that guarantees low delay and low packet loss during UMTS-WLAN handoff. For low handoff delay, the proposed handoff scheme performs pre-registration and pre-authentication processes before the layer 2 handoff. Moreover, it uses packet buffering and forwarding functions in order to reduce packet loss during the handoff period. Numerical and simulation results show that the proposed scheme performs well with respect to signaling cost, handoff delay, and packet loss compared with conventional schemes.

Seamless Handoff Scheme Based on Pre-registration and Pre-authentication for UMTS-WLAN Interworking

Interworking issues between Universal Mobile Telecommunication System (UMTS) and Wireless Local Area Network (WLAN) have become a great matter of interest as an increasing number of mobile internet users require broadband wireless access to IP services in the wide area. In this paper, we present a practical UMTS–WLAN interworking architecture based on 3GPP standards and propose a seamless handoff scheme that guarantees low delay and low packet loss during UMTS–WLAN handoff. For low handoff delay, the proposed handoff scheme performs pre-registration and pre-authentication processes before layer 2 handoff. Moreover, it uses packet buffering and forwarding functions in order to reduce packet loss during the handoff period. On the above basis, detailed signaling procedures are presented, together with system requirements when a mobile terminal moves from UMTS to WLAN and vice-versa. Numerical results show that the proposed scheme performs well with respect to signaling cost, handoff delay, and packet loss compared with conventional schemes.

Performance evaluation of VoIP over 3G-WLAN interworking system

In this paper, we present the experimental measurements of real-time voice packets over a 3G-WLAN interworking system. It is of interest to evaluate: (i) the performance of VoIP with an IPSec tunnel in a 3G-WLAN interworking system; (ii) maximum number of VoIP connections in a single 802.11b access point (AP); (iii) handoff latency due to terminal mobility; and (iv) impact of terminal mobility on the VoIP performance. Our results show that the performance can degrade significantly with an increase of VoIP connections and with the terminal mobility. Furthermore, the performance degradation affects all the existing VoIP connections, not merely the new connection or the user equipment which undergoes mobility. The amount of delay during terminal movement severely affects the performance of all realtime applications in that particular AP.

SHARE: seamless handover architecture for 3G-WLAN roaming environment

For the transition from 3G communication systems to 4G communication systems, 3G-WLAN interworking systems can be a reference model for 4G communication systems. In this paper, we identify challenging problems in 3G-WLAN interworking systems and propose a loosely coupled architecture called SHARE. In SHARE, each WLAN hotspot access point (AP) is equipped with a 3G radio transmission module to generate radio signals for control channels of 3G networks in addition to a WLAN radio module. Consequently, base stations of the 3G networks share their control channels with hotspot APs. By monitoring these channels, mobile nodes can easily detect available WLAN hotspots without probe delay for handovers.

A Novel Method for Authentication Optimization during Handover in Heterogeneous Wireless Networks

This paper presents a solution for optimizing network access authentication procedure and security context transfer during vertical handover in heterogeneous wireless networks (HWN). Security in HWN is a major challenge due to the vastly different security architectures used within each network. Currently, standardization working groups study the optimization of authentication procedure and security context transfer for seamless handover between heterogeneous networks. The goal of this paper is to provide a security frame work that accounts for heterogeneity in wireless access networks without degrading the level of security currently provided by the individual wireless systems. We propose a new frame work for access network specific authentication optimization and security context transfer during vertical handover preparation phase. We also demonstrate how the proposed security frame work provides improvement in the handover performance.

A novel scheme for mobility management in heterogeneous wireless networks

In this paper, we present a mobility management scheme for real-time multimedia sessions over heterogeneous wireless networks. Most approaches in the current literature use Mobile IP (MIP) or Session Initiation Protocol (SIP) to maintain real-time sessions during mobility. In this paper, we analyze MIP and SIP in terms of the mobility rate, packet loss and packet overheads in the user plane and propose a mechanism by which the network can choose the optimum protocol for mobility management. We perform the analysis for constant bit rate (CBR) as well as for variable bit rate (VBR) traffic. We show that for CBR traffic, the proposed mechanism leads to 12–35% improvement in the system capacity, while for VBR traffic, capacity improvements ranging from about 35–50% can be obtained. Our proposed approach and the analysis are applicable to handovers between different IP domains both in homogeneous as well as in heterogeneous wireless networks.