Tom Van Leeuwen

FAMOUS: A Network Architecture for Delivering Multimedia Services to FAst MOving USers

When today’s commuters in the train or in a car want to access the Internet, they see themselves restricted to simple web surfing or e-mail. Interactive multimedia services, like online gaming or video conferencing are still unavailable to them, even with promising new technologies like UMTS or WiMAX. The impact of high bit rate multimedia traffic on the access network and aggregation network is an important topic, that has not been addressed in enough detail before. We designed a network architecture for offering these multimedia services to fast moving users. We refer to the overall network architecture as the FAMOUS network architecture, which consists of two parts: (i) an access network part which has to deal with large number of users, asking for a high bandwidth, while experiencing a high handoff frequency and (ii) an aggregation network part which has to deal with dynamic tunnels of very high bandwidth, while experiencing a low handoff frequency. In this paper, we detail the FAMOUS architecture, together with optimized handoff strategies, an optical switching architecture, a design methodology for dimensioning aggregations networks and automatic tunnel pre-configuration and activation. Moreover, performance results of these mentioned aspects will be presented.

Location assisted fast vertical handover for UMTS/WLAN overlay networks

UMTS/WLAN integration offers considerable benefits for the mobile users as well as for the mobile network. As soon as coverage is available, a mobile user should switch seamlessly from the ubiquitous low bandwidth UMTS network to a high bandwidth WLAN. This will improve his quality of service, but also increases capacity in the cellular network. To be able to change between radio access technologies, an inter-RAT handover protocol is needed. If this handover protocol is not fast enough, the vehicular user will penetrate deep into the cell before packets get delivered to the right access point, underutilizing the available bandwidth with a lower overall performance as a result. In this paper, we introduce a new vertical handover protocol which uses location information from the vehicle to predict where and when the handover should occur, thus optimizing user throughput and network performance. We consider its deployment on three UMTS/WLAN integration scenarios.

A TCP Protocol Booster for Wireless Networks

Standard TCP has been developed for wired networks and stationary hosts. In wireless networks, consecutive handoffs between access points introduce packet loss that TCP will consider as an indication of congestion, which is followed by a reduction of its congestion window. This will result in a considerable degradation of the performance in terms of throughput, although sufficient bandwidth is available between handoffs. In this paper we present the design of a TCP protocol booster, which combines retransmissions based on negative selective acknowledgements, delayed duplicate acknowledgements and detection of congestion in order to protect the sender in a transparent way from the handoff packet losses. A test-bed implementation demonstrates that the booster improves the TCP performance considerably in a wireless network.