Abstract:
It is all about spectrum, the electromagnetic communication frequency spectrum characterizes
the distribution of all the different wireless technologies approved by the
Federal Communications Commission (FCC) and their emitted radiation power in
a way that minimizes the interference between two or more wireless systems. All
electronic communications compel a transmission medium to transmit the information
from one location (transmitter) to another (receiver). In radio frequency (RF), the
medium is free space. Today most of our electronic devices use the wireless channel
for communication of either voice or data. In order to overcome interference between
the numerous signals hovering in free space, each communication system should process
its own allocated frequency band. As the request for higher capacity and faster
services increases, new improved technologies have to find their room in the crowded
spectrum. Ultra-wideband (UWB) technology provides a bright solution to the over
populated RF spectrum by allowing new communication systems to coexist with the
present radio with almost no interference.
In order to increase the capacity with UWB systems to achieve high data rates, the use
of space-time coding (STC) with Multiple Input Multiple Output (MIMO) systems is
considered. This can be realized by transmitting independently and simultaneously
several symbols over different time intervals due to the antenna diversity introduced
with MIMO systems.
In this work, we present a noncoherent space-time block code based on a coherent
one discussed in the literature for M-PPM modulation associated with Impulse-Radio
Ultra-Wideband (IR-UWB) systems where neither the receiver nor the transmitter has
knowledge of the channel’s parameters. The proposed scheme takes advantages of the Multiple Input Multiple output (MIMO) system and achieves a full transmit diversity
with two transmitters at the cost of a reduced coding rate while being shape
preservative and totally real. The main advantage resides in a compelling adaptability
to simple energy detection bypassing involved analog to digital conversion.
