Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.Exploiting the available diversity from various sources in wireless networks is an easy way
to improve performance at the expense of additional hardware, space, complexity and/or
bandwidth. Signal space diversity (SSD) and cooperative communication are two promising
techniques that exploit the available signal space and space diversity respectively. This study
first presents symbol error rate (SER) analysis of an SSD system containing a single transmit
antenna and N receive antennas with maximal-ratio combining (MRC) reception; thereafter
it presents a simplified maximum-likelihood (ML) detection scheme for SSD systems, and
finally presents the incorporation of SSD into a distributed switch and stay combining with
partial relay selection (DSSC-PRS) system.
Performance analysis of an SSD system containing a single transmit antenna and multiple
receive antennas with MRC reception has been presented previously in the literature using the
nearest neighbour (NN) approximation to the union bound, however results were not presented
in closed form. Hence, closed form expressions are presented in this work. A new lower bound
for the SER of an SSD system is also presented which is simpler to evaluate than the union
bound/NN approximation and also simpler to use with other systems. The new lower bound is
based on the minimum Euclidean distance of a rotated constellation and is termed the minimum
distance lower bound (MDLB); it is also presented here in closed form. The presented bounds
have been validated with simulation and found to be tight under certain conditions.
The SSD scheme offers error performance and diversity benefits with the only penalty being an
increase in detector complexity. Detection is performed in the ML sense and conventionally,
all points in an M-ary quadrature amplitude modulation (M-QAM) constellation are searched
to find the transmitted symbol. Hence, a simplified detection scheme is proposed that only
searches m symbols from M after performing initial signal conditioning. The simplified
detection scheme is able to provide SER performance close to that of optimal ML detection in
systems with multiple receive antennas.
Cooperative communication systems can benefit from the error performance and diversity
gains of the spectrally efficient SSD scheme since it requires no additional hardware,
bandwidth or transmit power. Integrating SSD into a DSSC-PRS system has shown an
improvement of approximately 5dB at an SER of 10-4 with a slight decrease in spectral
efficiency at low SNR. Analysis has been performed using the newly derived MDLB and
confirmed with simulation
