Abstract:
Space time block coding (STBCs) improves the reliability of transmission
by sending multiple copies of data through multiple antennas. Recently, the
study of orthogonal designs in higher dimensions has supported higher diversity
gains, i.e. combining STBCs with different forms of diversity. Also,
designing codes with higher code rates is a desired aim for future communication
networks but the complexity of the receiver has always limited this
freedom. Quaternion orthogonal designs (QODs) have been derived mostly
from complex orthogonal codes (CODs). This supports the idea and benefits
of using QODs to achieve higher code rates but it remained limited in fully
exploiting the use of dual-polarized antennas. The real essence of adding the
polarization diversity to the coding designs still remains unexplored. This
research targets this research gap and presents a thorough analysis of using
higher dimensional variables not only to achieve efficient code designs with
higher code rates but also to investigate mechanisms to optimize the receiver
design. Based on these aims, this research takes two major paths. First,
it studies the impact of using quaternion designs with dual-polarized antennas.
The underlying channel between the dual-polarized transmit and receive
antennas is discussed when the pure QODs are transmitted. These QODs
provide promising diversity gains and shows comparative code rates similar
to the state-of-the-art Alamouti codes. Secondly, this research work presents
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linear and decoupled decoders for pure QODs, that was not possible before.
As an application of the proposals in this work, quaternionic channel-based
modulation has been discussed that fully exploits the polarization diversity
without considerable limitations on the transmit and receiver dimensions.
The design of wireless communication systems using pure QODs transmitted
using dual-polarized antennas will open new horizons of research. It will
support higher data rates and improved receiver efficiency, that are the two
main targets of the future generations of wireless systems.
