Mobile Satellite Broadcast and Multichannel Communications — Analysis and Design

Principal Investigator: Prof. Björn Ottersten
Funding source(s): SES ASTRA S.A., AFR/FNR
Researcher: Cristoff Martin, Industrial PhD Student Project

In this project, analytical analysis and design techniques for wireless communications
with diversity are studied. The impact of impairments such
as correlated fading is analyzed using statistical models. Countermeasures
designed to overcome, or even exploit, such effects are proposed
and examined. In particular two applications are considered, satellite
broadcast to vehicular terminals and communication using transmitters
and receivers equipped with multiple antennas.
Mobile satellite broadcast systems offer the possibility of high data
rate services with reliability and ubiquitous coverage. The design of system
architectures providing such services requires complex trade-offs involving
technical, economical, and regulatory aspects. A satisfactory
availability can be ensured using space, terrestrial, and time diversity
techniques. The amount of applied diversity affects the spectral efficiency
and system performance. Also, dedicated satellite and terrestrial
networks represent significant investments and regulatory limitations may
further complicate system design.
The work presented in this project provides insights to the technical
aspects of the trade-offs above. This is done by deriving an efficient
method for estimating what resources in terms of spectrum and delay
are required for a broadcast service to reach a satisfactory number of end
users using a well designed system. The results are based on statistical
models of the mobile satellite channel for which efficient analytical design
and error rate estimation methods are derived. We also provide insight to
the achievable spectral efficiency using different transmitter and receiver
configurations.

Multiple-element antenna communication is a promising technology for future high speed wireless infrastructures. By adding a spatial dimension, radio resources in terms of transmission power and spectrum can be used more efficiently. Much of the design and analysis work has focused on cases where the transmitter either has access to perfect channel state
information or it is blind and the spatial channels are uncorrelated.
Herein, systems where the fading of the spatial channels is correlated
and/or the transmitter has access to partial channel state information are
considered. While maintaining perfect channel knowledge at the transmitter
may prove difficult, updating parameters that change on a slower
time scale could be realistic. Here we formulate analysis and design
techniques based on statistical models of the multichannel propagation.
Fundamental properties of the multi-element antenna channel and limitations
given by information theory are investigated under an asymptotic
assumption on the number of antennas on either side of the system. For
example, limiting normal distributions are derived for the squared singular
values of the channel matrix and the mutual information. We also
propose and examine a practical scheme capable of exploiting partial
channel state information.
In both applications outlined above, by using statistical models of
the channel characteristics in the system design, performance can be
improved. The main contribution of this project is the development of
efficient techniques for estimating the system performance in different
scenarios. Such techniques are vital to obtain insights to the impact of
different impairments and how countermeasures against these should be
designed.