Felix Juraschek

Gossip routing in wireless mesh networks

Gossip routing is an approach to reduce the redundancy of flooding in wireless networks. A study by Haas et al. evaluated different gossip routing variants in simulations on regular and random network topologies. Using the DES-Testbed, a wireless mesh network, we tried to replicate their experiments to evaluate whether the findings hold in real world scenarios. Four different gossip routing variants and the experiment setup are elaborated as well as issues regarding the replication of the experiments discussed. With this study we demonstrate that even small wireless network deployments show a bimodal behavior when a certain probability threshold is passed.

DES-SERT: A framework for structured routing protocol implementation

Routing is a general task, yet the implementation of routing protocols requires specific operating system related knowledge. The developer has to deal with particular kernel internals that might have severe side effects. This is especially true for reactive and hybrid protocols where routing and forwarding are heavily intermixed. Furthermore, novel routing protocols require features that are not provided by current operating systems or have to be customized. Thus routing protocols for mobile ad-hoc networks and wireless mesh networks are often studied in simulation environments. However, simulations have limitations that can result in conclusions that do not hold in real networks. A framework for the implementation of routing protocols in operating systems is required to enable real world oriented research. We introduce the DES Simple and Extensible Routing-Framework for Testbeds (DES-SERT). The framework supports the implementation and evaluation of routing protocols in a testbed environment. A structured protocol implementation is advocated by transmitting data in extensions attached to packets and by its pipeline based architecture. Several steps are elaborated how to derive an implementation from a routing protocol specification.

Experimentation Made Easy

Scientifically sound network studies require the execution of large series of experiments. Researchers usually have to execute experiments manually, a labor-intensive and error-prone task, since there is no automation of the overall experimentation process. This task becomes especially hard on a distributed testbed and the researcher has to deal with additional challenges.

A Testbed for Next Generation Wireless Network Research

ABSTRACT Multi-hop wireless networks are in the focus of research since more than two decades. Mobile ad-hoc networks, wireless sensor networks, and wireless mesh networks are among the most prominent ones. The research in this area is done most often based on simulation studies. As these networks are hard to model with all their properties and operating system interdependencies, testbeds are an important alternative that has regained attention in largescale national and international research projects. In this paper we review architectures for next generation wireless networks including the aforementioned ones according to future applications. We introduce the DES-Testbed at the Freie Universität Berlin, which we believe is suitable to study these architectures or network configurations, as we call them. Furthermore, we discuss an approach on how to set up network configurations and perform long-term experiments.

An Experimental Facility for Wireless Multi-hop Networks in Future Internet Scenarios

Next to traditional communication systems like servers or routers at the backbone and personal computers or laptops acting as clients, the Future Internet will additionally comprise many so-called smart objects. Most of everyday devices like coffee machines, fridges, or light switches will participate in this Internet of Things (IoT).Small-sized computers will connect these devices to the network by establishing low power wireless links. To achieve this vision various kinds of wireless multi-hop networks (WMHNs) play an important role. During the last years, it has become clear that test bed-based research is mandatory in order to develop suitable protocol implementations and metrics for these networks. In this article, we review network configurations for wireless networks for the IoT. We describe the DES-Test bed at the Freie Universität Berlin as an experimental facility to study these network configurations. In addition to the infrastructure and software provided by the test bed, we introduce µkleos as a micro kernel based operating system for embedded devices. We designed µkleos with a special focus on Wireless Sensor Networks (WSNs) to complement our approach to study WMHNs.µkleos provides an implementation of 6LoWPAN to interconnect WSNs to IP-based networks.

From earthquake detection to traffic surveillance: about information and communication infrastructures for smart cities

Smart cities use networks of sensors, actuators, and centralized computing clusters to observe physical reality, derive information, and thereby influence citizens and authorities. Smart city applications therefore require three components to work: wireless sensor networks, geo-information systems, and frameworks for distributed analysis of sensor and geo-data. In this paper, we provide an overview on a set of concrete technologies for such information and communication infrastructures for smart cities. These technologies include a combination of WiFi- and PAN-based sensor networks, City GML data, a model-driven approach to collect and manage data, as well as distributed data analysis based on domain specific languages. We show how we use these technologies to research two typical smart city applications: earthquake early warning and traffic surveillance.

DES-Chan: A framework for distributed channel assignment in wireless mesh networks

In this paper we present the DES-Chan framework for experimentally-driven research on distributed channel assignment algorithms in wireless mesh networks. The implementation process of channel assignment algorithms is a difficult task for the researcher since common operating systems do not support channel assignment algorithms out of the box. DES-Chan provides a set of common services required by distributed channel assignment algorithms. The modular architecture of DES-Chan allows the extensions with further modules or the modifications of existing ones. As a proof of concept, we present a reference implementation of a distributed greedy channel assignment algorithm. We evaluate its performance in the DES-Testbed, a multi-transceiver wireless mesh network (WMN) with 100 nodes at the Freie Universität Berlin.

A Study of Adaptive Gossip Routing in Wireless Mesh Networks

Gossip routing is an approach to limit the overhead of flooding in wireless networks. Each node, that receives a packet that would normally be flooded, applies a probabilistic approach. The packet is either forwarded with probability p or dropped with 1 − p. This paper is a follow-up to our last study that evaluated the approaches by Haas et al. in the DES-Testbed, a wireless mesh network. Four different gossip routing variants were discussed which used static parameters to determine the value p. In this study, we compare the proposals by four other entities and discuss whether they show an overall improvement regarding the two most important metrics in this domain: reachability and redundancy. We also discuss the assumptions and parameters of the simulation studies in the context of our experiments in a real world deployment.

Distributed channel assignment in large-scale wireless mesh networks: A performance analysis

In this paper we present a performance evaluation of two distributed channel assignment algorithms in a large-scale wireless multi-radio testbed. We compare the performance of a link-based approach, in which channels are assigned to existing links in the network, with an interface-based approach, in which channels are assigned to the network interfaces. Both algorithms have significantly increased the network capacity in small wireless testbeds with less than 15 nodes. In this study, we investigate if the performance gain scales to large-scale wireless mesh networks. We evaluate the performance of the algorithms in the DES-Testbed, a multi-radio wireless mesh network with 126 nodes at Freie Universität Berlin. We compare the results to a single channel network and a randomized strategy. Additionally, we analyze the impact of the algorithms on the network connectivity and the spectral diversity. The results show, that compared to the single channel network, both algorithms increase the network capacity by a factor of three.

Multi-path OLSR performance analysis in a large testbed environment

Optimized Link State Routing (OLSR) protocol is a leading proactive routing protocol for Mobile Ad-hoc Networks (MANETs). Since the OLSR protocol in its standard version does not support multi-path packet forwarding, we have developed and implemented its multi-path extension. As a result of a slightly modified path computation algorithm and the application of backpressure Max-Weight Scheduling (MWS) policy, the MANETs can utilize the extended functionality based on OLSR. The experiment results presented in this paper compare the performance of the standard and extended OLSR versions in a large congested MANET (i.e., in large-scale DES-Testbed located at Freie Universitat Berlin).