N this information era people are living in a society in which
processing, ?ow and Iexchange of information are vital for their
existence. Two major issues in such so- ety, which are related to ?ow
and exchange of information, are connectivity and mobility. On one hand,
computers and Internet provide connectivity and allow communication as
well as fast access to large amounts of information. On the other hand,
wireless techno- gies bring mobility. People can move and still be able
to communicate and have access to various kind of information.
Therefore, the functioning of an information society is unthinkable
without the use of computers, Internet and wireless technologies. The
exp- tations are that in the future they will merge into a unique system
for communication, access to information as well as their exchange and
processing. The era of wireless communications started in 1901, when
Guglielmo Marconi s- cessfully transmitted radio signals across the
Atlantic Ocean. From that moment up to now wireless communications
experienced explosive growth and became the fastest growing ?eld in the
engineering world. Pushed by customer requirements, new wireless techno-
gies have been emerging very fast. Each new generation of wireless
technologies have brought new features and more complexity. Pushed by
market forces to reduce costs, the semiconductor industry has provided
new technologies for solid-state circuits implem- tation. Fortunately at
the same time with the cost reduction, performance of new te- nologies
has been improving.
