Mobile IP Telephony (MIPTel)

Project Report

Cooperation in Multi-hop Networks

The MIPTel project aims to develop and support mobile telephony applications over IP networks. Providers are in great need of scalable, extensible, flexible and transparent charging and accounting methods, which take into account the specific attributes of wireless networks and requirements of diversified services. A wide range of accounting, charging and pricing schemes have been analyzed. Our research focuses on cooperation and accounting strategies in multi-hop cellular networks. With multi-hop cellular networks the coverage area can be increased and the installation costs for the provider can be reduced. However, the individual customers play an important role in such networks and their participation must be encouraged. We proposed a scheme called CASHnet (Cooperation and Accounting Strategy in Hybrid Networks), which makes cooperation a rewarding alternative, but allows uncooperative nodes at the same time.

Wireless Mesh Networks

Wireless mesh networks (WMN) are evolving to an important access technology for wireless broadband services. They provide a cost efficient way to interconnect isolated networks as well as to enhance wireless network coverage. WMNs usually consist of static mesh routers and mobile or static mesh clients. Both support multi-hop communication and may act as routers. The mesh nodes might support multiple heterogeneous radio interfaces. WMNs offer a more robust and redundant communication infrastructure than many wireless networks deployed today. They provide communication facilities even in special situations where certain systems such as GSM are overloaded. Our project aims at exploiting WMNs as an infrastructure for Mobile IP telephony. IP telephony requires short delays and moderate packet loss. In WMNs the quality of the routes may vary unpredictably because of the unreliable and erroneous wireless medium. Routes may break, if the network topology changes due to node or link failures. Links and nodes may be- come congested, which leads to larger delays or packet loss. This makes the deployment of a real time application such as IP telephony a challeng- ing task.

We see two important approaches to improve the speech quality and to reduce outages in a Mobile IP telephony application in WMNs: path di- versity and multi-stream coding. The characteristics of multiple paths are usually uncorrelated, i.e., the delay, jitter, and loss rate of the paths dif- fer a lot from each other. Therefore, the transmission over multiple paths can be used to compensate for the dynamic and unpredictable nature of WMNs. In order to exploit this path diversity for improving the quality of the audio transmission, a robust multi-path routing protocol and a mechanism for selecting appropriate coding and path allocation for the given network conditions are needed.

ATOM (Adaptive Transport over Multipaths) is an architecture to enable real-time communications in Wireless Mesh Networks. ATOM reduces the problems of real-time transmissions over WMNs by using path diversity and multi-stream coding. At session estab- lishment, ATOM decides on the used parameter set (encodings, paths etc.) considering current network conditions and collected historic data. After session establishment, the effect of this decision is continuously monitored and if necessary adapted.

Multi-stream coding is one of the key parts of the ATOM architecture. In order to evaluate video codecs, we have defined an video evaluation framework for the OMNeT++ simulator. At the source, a video file is transcoded by the open source library ffmpeg into streams with the defined codec/parameters and then transmitted through the simulated network. At the destination, the video is reconstructed from the received packets and then compared with the original file by quality metrics.

A heterogeneous real-world test bed has been established for the MIPTel project. The testbed consists of PCEngines Wireless Router Application Platform (WRAP), PCEngines ALIX, Meraki Mini and OpenMesh om1p nodes. We tailored an embedded fully functional Linux with a small footprint to our three node types. The image build process is integrated in ADAM (Administration and Deployment of Adhoc Mesh networks). ADAM supports cross-compilation and individual build configuration for the three node types. The ADAM build and management system is highly modular and can be easily extended with additional software packages or ported to a new node type. It fully supports IPv6, flexible management nodes, and ad-hoc routing protocols. In addition, ADAM provides mechanisms for deployment and configuration a wireless mesh network. It guarantees the availability of the network de- spite configuration errors or faulty software updates by the mean of various fallback behaviors. It even provides a safe update of the operating system. ADAM has been selected as a candidate for the KuVS Communication Software award and has been presented to a wide audience at the KIVS conference.

In order to make experiments with larger topologies with Linux based nodes, we have design and implemented VirtualMesh. It provides a virtualization of a complete wireless mesh network by using host virtualization (XEN) for the mesh nodes and redirecting their wireless network traffic to a network simulator (emulation of the wireless medium). For the Linux networking stack, the driver now behaves as a normal wireless driver although it is performing the traffic redirection to the simulator.

In addition, we have started the implementation of a temporary WMN based system to support video communication in large construction sites, which faces the problem of missing communication facilities at the time of electric installation. By providing video communication over an “easy- to-install” temporary WMN, the requirement of costly on-site visits by an electrical engineer is reduced.

Project Details

Publications

	Thomas Staub, Reto Gantenbein, Torsten Braun: VirtualMesh: an emulation framework for wireless mesh and ad hoc networks in OMNeT++, SIMULATION , Thousand Oaks, CA, USA, Vol. 87, Nr. 1-2, January 1, 2011, pp. 66-81, SAGE Publications, ISSN 0037-5497 SAGE Print
	Thomas Staub, Reto Gantenbein, Torsten Braun: VirtualMesh: An Emulation Framework for Wireless Mesh and Ad-Hoc Networks in OMNeT++, SIMULATION: Transactions of the Society for Modeling and Simulation International, Special Issue on Software Tools, Techniques and Architectures for C , Thousand Oaks, CA, USA, July 2, 2010, SAGE Publications, ISSN 1741-3133 SAGE Online First
	Thomas Staub, Stefan Ott, Torsten Braun: Automated Deployment of a Wireless Mesh Communication Infrastructure for an On-site Video-conferencing System (OViS), 4th ERCIM Workshop on eMobility co-located with the 8th International Conference on wired/Wireless Internet Communications (WWIC 2010) , Lulea, Sweden, May 31, 2010, Lulea University of Technology, ISBN 978-91-7439-103-9
	Thomas Staub, Reto Gantenbein, Torsten Braun: VirtualMesh: An Emulation Framework for Wireless Mesh Networks in OMNeT++, The 2nd International Workshop on OMNeT++ (OMNeT++ 2009) held in conjuction with the 2nd International Conference on Simulation Tools and Techniques , Rome, Italy, March 6 - 7, 2009, pp. 1-8, ICST (Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering), ISBN 978-963-9799-45-5
	Thomas Staub, Daniel Balsiger, Simon Morgenthaler, Michael Lustenberger, Torsten Braun: ADAM (Administration and Deployment of Adhoc Mesh networks), Demo session for the KuVS Communication Software Award co-located with KiVS'09 , Kassel, Germany, March 6 - 7, 2009
	Thomas Staub, Stefan Ott, Torsten Braun: Experimental Evaluation of Multi-Path Routing in a Wireless Mesh Network Inside a Building, 5th Workshop on Mobile Ad-Hoc Networks - WMAN 2009 - in conjunction with the 16th bi-annual Conference on Communication in Distributed Systems (KiVS) , Kassel, Germany, Vol. 17, March 5 - 6, 2009, pp. 1-12, Electronic Communications of the EASST, ISSN 1863-2122
	Thomas Staub, Torsten Braun: Supporting Real-time Communication in Wireless Mesh Networks, 1st Workshop on Wireless Broadband Access for Communities and Rural Developing Regions - WIRELESS4D'08 held at 1st International Conference on M4D , Karlstad University, Sweden, Vol. 2008, Nr. 62, December 11 - 13, 2008, pp. 48-53, Karlstad University Press, ISBN 978-91-7063-222-8
	Thomas Staub, Torsten Braun: ATOM: Adaptive Transport over Multipaths in Wireless Mesh Networks, 2nd ERCIM Workshop on eMobility , Tampere, Finland, May 30, 2008, pp. 101-106, University of Tampere, Finland, ISBN 978-952-15-1972-7
	Thomas Staub, Daniel Balsiger, Michael Lustenberger, Torsten Braun: Secure Remote Management and Software Distribution for Wireless Mesh Networks, 7th International Workshop on Applications and Services in Wireless Networks (ASWN 2007) , Santander, Spain, May 24 - 26, 2007, pp. 47-54, ISBN 978-84-690-5727-8
	Attila Weyland, Carolin Latze, Torsten Braun, Thomas Staub: Linux Implementation and Evaluation of a Cooperation Mechanism for Hybrid Wireless Networks, Sixth International Workshop on Wireless Local Networks (WLN) , Tampa, FL, USA, November 14, 2006, pp. 939-946, IEEE, ISBN 1-4244-0419-3
	Attila Weyland, Thomas Staub, Torsten Braun: Comparison of motivation-based cooperation mechanisms for hybrid wireless networks, Computer Communications , Vol. 29, Nr. 13-14, August 21, 2006, pp. 2661-2670, Elsevier, ISSN 0140-3664
	Attila Weyland, Thomas Staub, Torsten Braun: Comparison of Incentive-based Cooperation Strategies for Hybrid Networks, 3rd International Conference on Wired/Wireless Internet Communications (WWIC 2005) , Xanthi, Greece, May 11 - 13, 2005, pp. 169-180, ISBN 3-540-25899-X
	Attila Weyland, Thomas Staub, Torsten Braun: Liveliness Evaluation of a Cooperation and Accounting Strategy in Hybrid Networks, 4th Workshop on Applications and Services in Wireless Networks (ASWN 2004) , Boston, MA, USA, August 8 - 11, 2004
	Attila Weyland, Torsten Braun: Cooperation and Accounting Strategy for Multi-hop Cellular Networks, 13th IEEE Workshop on Local and Metropolitan Area Networks (LANMAN 2004) , Mill Valley, CA, USA, April 25 - 28, 2004, pp. 193-198
	Attila Weyland, Torsten Braun: CASHnet - Cooperation and Accounting Strategy for Hybrid Networks, 2nd Workshop on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks (WiOpt 2004) , Cambridge, UK, March 24 - 26, 2004, pp. 423-424