Liesbeth Peters

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.

Micromobility support for random access network topologies

The combination of mobile IP with frequent handovers results in high handoff latencies and control overhead in the core network. Micromobility protocols like cellular IP. Hawaii and MIPv4 regional registration were developed to avoid these problems, supporting local mobility within one IP domain. Hereby, tree access topologies were considered to evaluate the protocol performance A. Campbell et al., (2000) (2002) although meshed topologies are desired for reasons of robustness against link failures and load balancing L. Peters et al., (2003). The mentioned micromobility protocols do not use the extra links or result in a bad performance in terms of end-to-end delay. This paper proposes a new micromobility protocol for random access topologies. During handoff a router in the access network detects if it has the function of cross-over node. Hereby, control traffic is concentrated near the involved access routers, while optimal paths in the access network are achieved. The basic concept of the protocol is presented and the handoff performance is compared to other micromobility protocols.

Impact of the access network topology on the handoff performance

Micromobility protocols such as Cellular IP, Hawaii and Hierarchical Mobile IP are developed to solve problems of high handoff latency and control overhead, which occur when Mobile IP is used in combination with frequent handoffs. Up to now, tree access network topologies are considered to evaluate the protocol performance. However, for reasons of robustness against link failures and load balancing, extra uplinks and mesh links in the topology are desired. This article makes a classification of several topology types and gives a model that points out to which extent the topology influences the protocol performance in terms of handoff latency and handoff packet loss. Simulations confirm the results calculated by the model. Performance metrics such as load balancing, end-to-end delay and robustness against link failures are also evaluated. The study points to several shortcomings of the existing micromobility protocols for different topology types. Several aspects of the studied handoff schemes, their advantages and drawbacks are identified.

Network Layer Solutions forWireless Shadow Networks

Congestion control in wireless multi-hop networks is challenging and complicated because of two reasons. First, interference is ubiquitous and causes loss in the shared medium. Second, wireless multihop networks are characterized by the use of diverse and dynamically changing routing paths. Traditional end point based congestion control protocols are ineffective in such a setting resulting in unfairness and starvation. This paper adapts the optimal theoretical work of Tassiulas and Ephremedes [33] on cross-layer optimization of wireless networks involving congestion control, routing and scheduling, for practical solutions to congestion control in multi-hop wireless networks. This work is the first that implements in real off-shelf radios, a differential backlog based MAC scheduling and router-assisted backpressure congestion control for multi-hop wireless networks. Our adaptation, called DiffQ, is implemented between transport and IP and supports legacy TCP and UDP applications. In a network of 46 IEEE 802.11 wireless nodes, we demonstrate that DiffQ far outperforms many previously proposed “practical” solutions for congestion control.Nowadays, people more and more rely on a good working telecommunication network for every day activities. However, due to natural disasters or intentional attacks, large parts of this network can be destroyed. While the setup of a new, wired infrastructure can take several days, network connection is already needed within the first hours for rescue operations. The setup of a wireless adhoc network, known as a wireless shadow network, can provide such communication. In this paper, the broadcasting scenario, as presented in [1], is studied and several network layer issues are identified. To solve these issues, two network layer solutions are investigated: the ad hoc protocol OLSR [3] in combination with Mobile IP and the micromobility handoff scheme MEHROM’ [4] in combination with Mobile IP Regional Registration. Our MEHROM’ scheme turns out to perform the best in fulfilling the severe requirements of simplicity, mobility support and easy integration with the wired network.

Q-MEHROM: mobility support and resource reservations for mobile senders and receivers

The increasing use of wireless networks and the popularity of multimedia applications, lead to the need for Quality of Service support in a Mobile IP-based environment. This paper investigates the reservation of resources for mobile receivers as well as senders in combination with micromobility support. We present Q-MEHROM, which is the close coupling between the micromobility protocol MEHROM and a resource reservation mechanism. In case of handoff, Q-MEHROM updates the routing information and allocates the resources for a sending or receiving mobile host simultaneously. Invalid routing information and reservations along the old path are explicitly deleted. Resource reservations along the part of the old path that overlaps with the new path are reused. Q-MEHROM uses access network topology and link state information calculated by QOSPF. Simulation results show that the control load is limited. Moreover, it consists mainly of QOSPF traffic and it is influenced by the handoff rate in the network. Q-MEHROM makes real use of the mesh links and extra uplinks, which are present in the access network to increase the robustness against link failures, to reduce handoff packet loss and to improve the performance for highly asymmetric network loads. Also, attention is paid to the differences between the mobile sender and the mobile receiver scenario.

Q-MEHROM: mobility support and resource reservations for mobile hosts in IP access networks

The increasing use of wireless networks and the popularity of multimedia applications, leads to the need of Quality of Service support in a mobile IP-based environment. This paper presents Q-MEHROM, which is the close coupling between the micromobility protocol MEHROM and a resource reservation mechanism. In case of handoff, Q-MEHROM updates the routing information and allocates the resources for receiving mobile hosts simultaneously. Invalid routing information and reservations along the old path are explicitly deleted. Resource reservations along the part of the old path that overlaps with the new path are reused. Q-MEHROM uses information calculated by QOSPF. Simulation results show that the control load is limited, mainly QOSPF traffic and influenced by the handoff rate in the network. Q-MEHROM uses mesh links and extra uplinks, present to increase the link failure robustness, to reduce handoff packet loss and improve the performance for highly asymmetric network loads.

Support of path changes with resource reservations for mobile hosts in IP-based access networks

The increasing use of wireless networks and the popularity of multimedia applications, leads to the need of QoS (quality of service) support in a mobile IP-based environment. This paper considers the reservation of resources in the micromobility scenario. The reasons for path changes in the access network are investigated. Based upon this, we present the functionality that should be present in the different access network elements to support path changes regardless their cause and to avoid router inconsistencies. For the simulations we added this functionality to our previously developed Q-MEHROM handoff scheme (L. Peters et al., 2005). However, the ideas and results presented in this paper are not restricted to this micromobility protocol

Wireless Shadow Network Setup Through the Mehrom Micromobility Protocol

Due to natural disasters or intentional attacks, large parts of our telecommunication network can be destroyed. The setup of a wireless shadow network can restore the damaged network connectivity. This paper investigates the need for a network layer solution to integrate such a wireless shadow network with the wired network. It presents the combination of the micromobility protocols MEHROM and mobile IP regional registration as an efficient solution to support terminal mobility. The proposed solution is evaluated in terms of control overhead, required storage and calculation capacity, and functional complexity

Performance evaluation of a framework to support path changes in IP-based access networks

The increasing use of wireless networks and the popularity of multimedia applications, leads to the need of Quality of Service support in a mobile IP-based environment. In [1], we investigated the reasons for path changes in the access network and we presented a framework to support these path changes regardless their cause and to avoid router inconsistencies. In this paper, the performance of this framework is thoroughly evaluated. To this end, we added the functionality of the framework to our Q-MEHROM handoff scheme [2]. However, the ideas and results presented in this paper are not restricted to this micromobility protocol. The performance with and without the defined functionalities is compared and tested under different network topologies, in terms of received service, packet loss and end-to-end delay.

Impact of link state changes and inaccurate link state information on mobility support and resource reservations

The increasing use of wireless networks and the popularity of multimedia applications, leads to the need of QoS (Quality of Service) support in a mobile IP-based environment. This paper presents the framework, needed to support both micromobility and resource reservations. We present an admission control mechanism in which a mobile host can trigger reservations without performing handoff, taking advantage of link state changes caused by the handoff of other mobile hosts. We also investigate the impact of inaccurate link state information and the occurrence of simultaneous handoffs on the performance of the handoff and reservation mechanism. This impact is higher when only a small part of the mobile hosts can receive QoS service at the same time. For the simulations, we use Q-MEHROM [10]. Herein, [11] gathers the link state information and calculates the QoS tables. However, the ideas and results presented in this paper are not restricted to these protocols.