Exploiting the wireless channel for communication

de Lacerda Neto, Raul Liberato




The development of cellular communications during the 1980s made wireless networks

one of the most important areas of technology. Fueled by the advances in wireless computer

networks, high data rate connections have recently become the focus of research

in the communication domain. The growth of the Internet and the introduction of a

multitude of applications culminated in a new era of communications in which wireless

networks play a very important role.

However, the wireless environment still offers some challenges that need to be addressed

before reaching the prerequisites of future wireless networks. Due to imprecise

channel characterization, much of the potential of the wireless environment is wasted.

Furthermore, the requirements caused by multiple connections lead to the use of multiple

access schemes that were not designed to cope with some of the wireless environment

phenomenons. These two points are treated in this thesis.

The first part of this thesis is dedicated to the use of probability theory tools that

enable the creation of models based only on partial knowledge of the environment. Using

Jaynes' maximum entropy principle, we present a framework that allows us to infer on

the channel characteristics by choosing probability distributions that maximize entropy

under the constraints that represent our state of knowledge. This technique is considered

as the most reliable method to perform inferences. Models for two different types of environment

are derived: wideband channels and multiple-input multiple-output (MIMO)


In the second part, the multiple access problem for ultra wideband (UWB) systems

is assessed. Despite the large amount of work conducted during recent years on UWB

technology, no scheme can cope with the high dispersion of UWB channels and still offer

reasonable spectral efficiency. An innovative scheme that exploits the users' channels

to guarantee multiple access is introduced, entitled Channel Division Multiple Access

(ChDMA). This scheme provides a very simple solution and achieves high spectral efficiency.

Systèmes de Communication
Eurecom Ref:
© Université de Nice. Personal use of this material is permitted. The definitive version of this paper was published in Thesis and is available at :
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PERMALINK : https://www.eurecom.fr/publication/2703