The University of Western Ontario, Canada
|Andrea M. Tonello
DIEGM - Università di Udine, Italy
The 14th ACM MSWiM 2011 Symposium
is pleased to offer the following half day tutorials:
Tutorial title: From Packets to Time Samples - Physical Layer Simulation for Advanced Wireless Networking Research
Jens Mittag and Prof. Hannes Hartenstein
Decentralized Systems and Network Services Research Group
Karlsruhe Institute of Technology (KIT)
Abstract: The communication performance of upcoming wireless ubiquitous networks - for instance of cooperative vehicular systems - will be influenced significantly by the mobility of its nodes, by external influences such as communication obstacles, and by the large number of transmitting and receiving nodes. Especially a time- and frequency-selective fading of the channel, which is typically modeled through multi-tap filters, and large Doppler spreads can degrade the communication reliability significantly. In order to recognize the impacts of these characteristics and to properly assess the performance of such networks - as well as the performance of applications that are built on top of them - one has to understand how these effects influence/alter the signal of a transmitted packet and how this influence can impact the successful reception of the packet. Understanding these effects and their impact on communication performance is also crucial if a joint optimization of the physical and medium access and/or network layer are considered. Recent studies proposing cross-layer optimizations to achieve a higher network performance or to simplify higher layer protocols, e.g. through interference cancellation or network coding on physical layer, are only an example for such optimizations. The example also shows that a separated development of the lower layers might not be the best approach to get the best performance out of future systems and networks. Indeed, it will be beneficial to communication engineers if they are experts on both layers, networking and physical layer.
This tutorial will use the IEEE 802.11 standard and its OFDM-based PHY specification as a concrete example for wireless communication. With the help of a validated physical layer simulator that is integrated into the popular NS-3 network simulator (published under the GPL and available at http://dsn.tm.kit.edu/english/ns3-physim.php), the proposed tutorial covers the following two aspects:
1) Step-by-step explanation and illustration of signal processing steps that are executed at the physical layer of a wireless communication system, such that researchers from the networking community understand the challenges, caveats and opportunities that exist at the physical layer:
a) Signal theory: How can complex signals be used to represent individual bits (PSK, QAM, OFDM)? Illustration of fundamental characteristics (Phase shifts, frequency offsets, etc.)
b) Signal processing mechanisms: Error correction, bit scrambling, pilot symbols/subcarriers, insertion of guard intervals and what is the motivation behind each mechanism.
2) Discussion of typical radio propagation effects, explanation of how the effects can be quantified, and outline their implications on physical layer signal processing:
a) Free-space vs. multi-path propagation, effects imposed by node mobility / changes in the geometry of the environment, classification of various propagation models (pathloss, large-scale, small-scale) and modeling methods (deterministic, stochastic, stochastic-deterministic)
b) Signal processing algorithms: detection of a transmission, time synchronization, channel estimation and equalization, the actual decoding of received signals, as well as a discussion of how channel impairments can be encountered.
Bio: Jens Mittag holds a diploma in computer sience from the University of Karlsruhe, Germany, and is currently pursuing his Ph.D. within the Decentralized Systems and Network Services Research Group at the Karlsruhe Institute of Technology (KIT), Germany. His research interests include vehicular mobile networks, accurate simulation environments and the modeling of the lower layers in wireless digital communications. He participated in the NOW: Network on Wheels project (2004-2008) and contributed to the standardization of Intelligent Transportation Systems (ITS) in Europe as a member of the ETSI specialist task force on Configuration and Validation of Channel Congestion Control Methods of ITS. Furthermore, Jens gives lectures about Vehicle-to-Vehicle and Vehicle-to-Infrastructure Communication for the HECTOR School of Engineering and Management, the Business School of the Karlsruhe Institute of Technology (KIT), and teaches Modeling and Simulation of Distributed Systems and Networks to students of the Karlsruhe Institute of Technology.
Hannes Hartenstein is a full professor for decentralized systems and network services at the Karlsruhe Institute of Technology (KIT), Germany, and executive director of the KIT Steinbuch Centre for Computing. He is also member of the scientific directorate of IBFI Schloss Dagstuhl. His research interests include mobile networks, virtual networks and IT management. Prior to joining the University of Karlsruhe, he was a senior research staff member with NEC Europe. He was involved in the FleetNet - Internet on the Road (2000-2003) and NOW: Network on Wheels (2004-2008) projects, partly funded by the German Ministry of Education and Research (BMBF), he actively participated in the EU FP7 project PRE-DRIVE-C2X (2008-2010), and is now contributing to the follow-on project called DRIVE-C2X. He has been TPC co-chair and general chair of various highly selective ACM and IEEE international workshops and symposia on vehicular communications. He co-authored more than 100 publications, more than 40 devoted to vehicular ad-hoc networks, and presented a tutorial on Vehicular Ad-Hoc Networks at ACM MobiCom/MobiHoc in 2007.