Marius Portmann

Wireless Mesh Networks for Public Safety and Crisis Management Applications

Wireless mesh networks (WMNs) are multihop wireless networks with self-healing and self-configuring capabilities. These features, plus the ability to provide wireless broadband connectivity at a comparatively low cost, make WMNs a promising technology for a wide range of applications. While discussing the suitability of WMN technology for public safety and crisis management communication, this article highlights its strengths and limitations and points to current and future research in this context.

Evaluation of multi-radio extensions to AODV for wireless mesh networks

Due to their self-configuring and self-healing capabilities, as well as their low equipment and deployment cost, Wireless Mesh Networks (WMNs) based on commodity hardware present a promising technology for a wide range of applications. Currently, one of key challenges that WMN technology faces is the limited capacity and scalability due to high levels of interference, which is typical for multi-hop wireless networks. A simple and relatively low-cost approach to address this problem that has recently been proposed is the use of multiple wireless network interfaces (radios) per node. Operating the radios on each node on different, non-overlapping channels allows making more efficient use of the radio spectrum and thereby reducing interference and contention. In this paper, we evaluate the performance of the Ad-hoc On-demand Distance Vector (AODV) routing protocol in a Multi-Radio Wireless Mesh Network. Our simulation results show that under high traffic load conditions, Multi-Radio AODV (AODV-MR) is able to efficiently utilize the increased spectrum, and proves to be far superior to single radio AODV. We therefore believe that AODV-MR is a promising candidate for multi-radio WMNs.

Cost-effective broadcast for fully decentralized peer-to-peer networks

Fully unstructured and decentralized peer-to-peer networks such as Gnutella are appealing for a variety of applications, among which file-sharing is the most prominent one. The decentralized nature of these systems provides a high degree of robustness and the ability to cope with a highly dynamic and transient network environment. However, the lack of centralized directory nodes makes the task of searching more expensive and difficult. In completely unstructured peer-to-peer networks, searching can only be realized via application-layer broadcast, where query messages are routed to every node in the network. Gnutella implements application-layer broadcast by using flooding as the underlying message routing mechanism. Flooding creates a large amount of traffic and can quickly exhaust the resources of nodes in a large network. In this paper, we explore Rumor mongering (also known as Gossip) as a more cost-effective and scalable alternative to flooding for implementing services such as searching in decentralized peer-to-peer networks. We further present a new variant of the Rumor mongering protocol, which exploits the power-law characteristics of typical peer-to-peer networks and achieves a significant further reduction in cost.

The cost of peer discovery and searching in the Gnutella peer-to-peer file sharing protocol

A lot of attention has been focused on peer-to-peer file sharing systems. Gnutella is a fully distributed peer-to-peer protocol without the need for a central entity. This increases the reliability of the system by avoiding a single point of failure as well making it more immune to legal attack. The two main features of the Gnutella protocol discovery of peers and searching for files are implemented by passing different types of messages between the nodes of the Gnutella overlay network. Due to its fully distributed nature, Gnutella relies on flooding to route most of these messages, which immediately raises the question of cost and scalability. We study these aspects of the Gnutella protocol by means of simulation also considering the influence of the topology of the Gnutella network.

MARCH: a distributed content adaptation architecture

A novel, server-centric architecture for adapting media content to suit the operational environment for heterogeneous devices and networks is presented. The given architecture, so called MARCH, exhibits several advantages over traditional static proxy solutions. The viability of the MARCH framework has been demonstrated through a prototype implementation.

Automated analysis of AODV using UPPAAL

This paper describes an automated, formal and rigorous analysis of the Ad hoc On-Demand Distance Vector (AODV) routing protocol, a popular protocol used in wireless mesh networks. We give a brief overview of a model of AODV implemented in the UPPAAL model checker. It is derived from a process-algebraic model which reflects precisely the intention of AODV and accurately captures the protocol specification. Furthermore, we describe experiments carried out to explore AODVs behaviour in all network topologies up to 5 nodes. We were able to automatically locate problematic and undesirable behaviours. This is in particular useful to discover protocol limitations and to develop improved variants. This use of model checking as a diagnostic tool complements other formal-methods-based protocol modelling and verification techniques, such as process algebra.

A process algebra for wireless mesh networks

We propose a process algebra for wireless mesh networks that combines novel treatments of local broadcast, conditional unicast and data structures. In this framework, we model the Ad-hoc On-Demand Distance Vector (AODV) routing protocol and (dis)prove crucial properties such as loop freedom and packet delivery.

Securing Wireless Mesh Networks

Now found in domestic, commercial, industrial, military, and healthcare applications, wireless networks are becoming ubiquitous. Wireless mesh networks (WMNs) combine the robustness and performance of conventional infrastructure networks with the large service area and self-organizing and self-healing properties of mobile ad hoc networks. In this article, the authors consider the problem of ensuring security in WMNs, introduce the IEEE 802.11s draft standard, and discuss the open security threats faced at the network and data-link layers.

Performance analysis of multi-radio AODV in hybrid wireless mesh networks

Wireless Mesh Networks (WMNs), based on commodity hardware, present a promising technology for a wide range of applications due to their self-configuring and self-healing capabilities, as well as their low equipment and deployment costs. One of the key challenges that WMN technology faces is the limited capacity and scalability due to co-channel interference, which is typical for multi-hop wireless networks. A simple and relatively low-cost approach to address this problem is the use of multiple wireless network interfaces (radios) per node. Operating the radios on distinct orthogonal channels permits effective use of the frequency spectrum, thereby, reducing interference and contention. In this paper, we evaluate the performance of the multi-radio Ad-hoc On-demand Distance Vector (AODV) routing protocol with a specific focus on hybrid WMNs. Our simulation results show that under high mobility and traffic load conditions, multi-radio AODV offers superior performance as compared to its single-radio counterpart. We believe that multi-radio AODV is a promising candidate for WMNs, which need to service a large number of mobile clients with low latency and high bandwidth requirements.

High Performance AODV Routing Protocol for Hybrid Wireless Mesh Networks

Hybrid wireless mesh networks are multi-hop networks consisting of two types of nodes, mesh routers and mesh clients. Mesh routers are more static and less resource constrained than mobile mesh clients, and form the wireless backhaul of the network. Routing in hybrid wireless mesh networks is a challenging task as both type of nodes participate in the routing and forwarding of packets. In this paper, we present extensions to the ad-hoc on-demand distance vector (AODV) routing protocol with the aim to exploit the heterogeneity of hybrid wireless mesh networks. As demonstrated via extensive simulations, our extensions achieve a more than 100% improvement over the standard multi-radio AODV in terms of key performance metrics such as packet delivery ratio, routing overhead and latency.