Martin Wenig

The effect of the radio wave propagation model in mobile ad hoc networks

The simulation of wireless networks has been an important tool for researchers and the industry in the last years. Especially in the field of Mobile Ad Hoc Networking, most current results have been achieved using simulators. The need for reproducible results and easy to observe environments limits the use of real world measurements for those kind of networks.It is stated here that the radio wave propagation model has a strong impact on the results of the simulation run. This work shows the limitations of current simulation environments and describes a high accuracy propagation model based on the use of a ray-tracer. By using a parallelized preprocessing step we made this propagation model feasible for usage in network simulators. Based on two examples, the effects on characteristic performance properties in Mobile Ad Hoc Networks are shown. We found that the physical layer simulation has a great impact on routing protocol efficiency.

How to Study Wireless Mesh Networks: A hybrid Testbed Approach

Simulation is the most famous way to study wireless an mobile networks since they offer a convenient combination of flexibility and controllability. However, their largest disadvantage is that the gained results are difficult to transfer into reality since not only the abstraction of the upper network layer are typically high, but also the environment of mobile and wireless networks is very complex. This is due to two reasons. First there are typically many simplifications in the models of the upper networking layers, and second the environment of mobile and wireless networks is in particular complicated and thus difficult to be considered in all details. In this paper we introduce UMIC-mesh, a hybrid testbed approach, that consists of real mesh nodes and a virtualization environment. On the one hand the virtualization allows the development and testing of software as if it was executed on real mesh routers, but in a more repeatable and controllable way. On the other hand the results and conclusions gained by a software evaluation in the testbed can be easily transferred into reality, since the testbed represents a high degree of realism.

Performance Evaluation of a Hybrid Testbed for Wireless Mesh Networks

Wireless mesh networks (WMN) are supposed to provide flexible and high-performance wireless network access for large indoor and outdoor areas, e.g., community networking and metropolitan area networks. However, these claims are mostly substantiated by simulation studies only as real testbeds are inflexible and associated with high maintenance effort. In this work we present a hybrid, i.e., partly real and partly virtualized, WMN testbed. This provides a high degree of realism while still allowing the flexibility known from simulations. In addition to the architectural discussion we present measurement results from our testbed highlighting the optimization potential of small protocol parameter changes.

Architecture of the hybrid MCG-mesh testbed

The study of wireless and mobile networks is mainly based on simulations. Although simulation environments offer a convenient combination of flexibility and controllability, their largest disadvantage is that the results gained by using them are difficult to transfer into reality. This is due to the complex environment of mobile and wireless networks.In this paper we introduce a hybrid testbed approach, which consists of real mesh nodes and a virtualization environment. This combination provides on the one hand a flexible development environment for distributed network protocols and applications, and on the other hand a high degree in realism. Therefore, it allows the design and conduction of large scale networks where the results are easily transferred to the real world.

Realistic mobility and propagation framework for MANET simulations

Two main steps on the way to more realistic simulations of mobile ad-hoc networks are the introduction of realistic mobility and sophisticated radio wave propagation models. Both have strong impact on the performance of mobile ad-hoc networks, e.g. the performance of routing protocols changes with these models. In this paper we introduce a framework which combines realistic mobility and radio wave propagation models. Our approach consists of a zone-based mobility generator and a high accuracy radio wave propagation model. For the mobility generation a wide variety of well understood random mobility models is combined with a graph based zone model, where each zone has its own mobility model. To achieve a realistic radio wave propagation model a ray tracing approach is used. The integration of these two techniques allows to create simulation setups that closely model reality.

Models for Realistic Mobility and Radio Wave Propagation for Ad Hoc Network Simulations

An ad hoc network is realized by mobile devices which communicate over radio. Since, experiments with real devices are very difficult, simulation is used very often. Among many other important properties that have to be defined for simulative experiments, the mobility model and the radio propagation model have to be selected carefully. Both have strong impact on the performance of mobile ad hoc networks, e.g., the performance of routing protocols changes with these models. There are many mobility and radio propagation models proposed in literature. Each of them was developed with different intentions and is not suited for every scenario. In this chapter we introduce well-known models for mobility and radio propagation, and discuss their advantages, drawbacks, and limitations in respect to the simulation of mobile ad hoc networks.

Improving MANET Simulation Results - Deploying Realistic Mobility and Radio Wave Propagation Models

Recent research has shown the poor accuracy of widely used simulators in the area of wireless networks. Beside many other parameters two are of particular interest: (i) the mobility model, and (ii) the radio wave propagation model. The first is responsible for the network topology and the latter for the perception of transmitted data. Both have strong impact on the performance of mobile ad-hoc networks, e.g. the performance of routing protocols changes with these models. We developed a framework combining a realistic mobility model and radio wave propagation model. To generate mobility multiple well understood random mobility models are combined in a scenario graph. The graph also includes obstacles which restrict the movement and the radio wave propagation. The radio wave propagation is calculated using a ray-tracing approach. We present an extensive simulation study on the effect of the mobility and radio wave propagation on simulation results.

Construction and Evaluation of a Wireless Mesh Network Testbed

Wireless mesh networks (WMN) are supposed to provide flexible and high-performance wireless network access for large indoor and outdoor areas, e.g., community networking and metropolitan area networks. However, these claims are mostly substantiated by simulation studies only as real testbeds are inflexible and associated with high maintenance effort. In this work we present a hybrid, i.e., partly real and partly virtualized, WMN testbed. This provides a high degree of realism while still allowing the flexibility known from simulations. In addition to the architectural discussion we present measurement results from our testbed highlighting the optimization potential of small protocol parameter changes.

A Hybrid Testbed for Wireless Mesh Networks

The study of wireless and mobile networks is mainly based on simulations. Although simulation environments offer a convenient combination of flexibility and controllability, their largest disadvantage is that the results gained by using them are difficult to transfer into reality. This is due to the complex environment of mobile and wireless networks. In this paper we introduce a hybrid testbed approach, which consists of real mesh nodes and a virtualization environment. This combination provides on the one hand a flexible development environment for distributed network protocols and applications and on the other hand a high degree in realism. Therefore, it allows the design and conduction of large scale networks where the results are easily transferred to the real world

Improving tcp performance through explicit corruption and route failure notification (ecrfn)

The Transport Control Protocol (TCP) was designed with fixed, wired networks in mind. As a result TCP performs suboptimal in networks with noisy links and changing paths, e.g., wireless multi-hop networks. The main reason is that TCP assumes packet loss indicates congestion. However, such fluttering networks drop a non negligible amount of packets because of corruption, route failures and disconnections. In this paper we introduce and evaluate the Explicit Corruption and Route Failure Notification (ECRFN) algorithm. ECRFN improves TCP performance in such environments. It treats all possible loss types and features a smart timing scheme in case of path disconnections. It employs an optional router enhancement and exploits common router messages.