Wednesday August 29, 2007

 

 

Lecturer: Mr. Sandro Scalise and Prof. Vittorio Degli Esposti

DLR, Oberpfaffenhofen (Germany) / University of Bologna (Italy)
e-mail: Sandro.Scalise@dlr.de - vdegliesposti@deis.unibo.it

Title: Propagation and Packet Error Models for Mobile Wireless Channels

Abstract: A good understanding of the impairments introduced by the propagation channel is of paramount importance in the design of a satellite-based communications system. The relevant sources of channel impairments depend upon several factors, among them the considered scenario (e.g. mobile vs. fixed terminals, rural vs. urban etc…), the carrier frequency and the employed access scheme. For instance, effects like shadowing and blockage are typical of mobile reception. On the other hand, atmospheric attenuation phenomena can be safely disregarded at frequency bands below some GHz, whereas they start to become relevant as the carrier frequency increases.
Since terminals are often located in urban areas, where also repeaters and gap fillers may be adopted, also terrestrial, multipath propagation represents a major concern. Urban multipath propagation and its impact on the radio channel characteristics will be therefore addressed, with a particular focus on deterministic models such as ray tracing.
Furthermore, a formal methodology to derive packet error models complementing a purely propagational model with considerations related to the adopted waveform and coding scheme will be presented.
Each of the main parts of this lecture will be organized as an independent module. In general, the main focus will be on specific results and considerations derived by models and measurements, rather than on reviewing the well-known theory of channel characterization and modelling. Nevertheless, the most important definitions will be recalled for the sake of clarity and adequate references provided.
The lecture will be concluded by a short talk concerning the ongoing revision of DVB-RCS standard towards the full support of mobility.

1. Introduction

2. Characterization of Linear Time-Variant Propagation Channels (0.5 h)

• Channel Characteristic functions
• Channel Parameters and Classification
• First and Second Order Channel Statistics

3. Propagation Channel Models for Satellite Channels at Different Frequency Bands and for Different Environments (1.5 h)

• Single-State First-Order Characterization for Frequency Non-Selective Channels
• Multi-State Markov Chain Models for Frequency Non-Selective Channels
• Doppler Spectrum Models
• Modelling of Frequency Selective Channels
• Example of Models and Measurements

4. Propagation and Channel Modelling for Terrestrial Links in the Urban Environment (2 h)

• Introduction to urban propagation
• Power Attenuation with distance
• Macro -and micro- cellular propagation
• Need for multi-dimensional models
• Classification of urban propagation and channel models
• Deterministic ray models
• Environment representation issues
• Geometrical Optics basics
• Ray tracing and ray launching
• Hybrid ray models and diffuse scattering
• Multidimensional prediction by ray tracing
• Deterministic channel modelling by ray tracing

5. From Propagation Models to Packet Error Models (1 h)

• <to be further detailed>

6. Test (0.5 h)

• Overview about the ongoing revision of DVB-RCS standard towards the full support of mobility.

Lecturer’s Short Bio

Sandro Scalise was born in Utrecht, Holland in April 1973. In July 1999 he graduated in Electronic Engineering specialising in Telecommunications (with honours) from University of Ferrara, Italy. Since 2001, he is with the Institute for Communications and Navigation, DLR (German Aerospace Centre), Germany. Since October 2004, he is leading the Mobile Satellite Systems Group. His research activity deals with forward error correction and synchronization schemes for mobile satellite applications, land mobile satellite channel modelling and link performance evaluation. He is co-author of many international journal and conference papers, was co-chairman of the 3rd Advanced Satellite Mobile Systems Conference in 2006 and editor of a chapter devoted to satellite channel impairments in the framework of a book devoted to satellite communications to be published by Springer.

Please visit: http://www.dlr.de/kn/institut/abteilungen/dn/satcom/index