2 research outputs found
Spatial modulation: theory to practice
Spatial modulation (SM) is a transmission technique proposed for multiple–input multiple–
output (MIMO) systems, where only one transmit antenna is active at a time, offering an increase
in the spectral efficiency equal to the base–two logarithm of the number of transmit
antennas. The activation of only one antenna at each time instance enhances the average bit
error ratio (ABER) as inter–channel interference (ICI) is avoided, and reduces hardware complexity,
algorithmic complexity and power consumption. Thus, SM is an ideal candidate for
large scale MIMO (tens and hundreds of antennas). The analytical ABER performance of SM
is studied and different frameworks are proposed in other works. However, these frameworks
have various limitations. Therefore, a closed–form analytical bound for the ABER performance
of SM over correlated and uncorrelated, Rayleigh, Rician and Nakagami–m channels is proposed
in this work. Furthermore, in spite of the low–complexity implementation of SM, there
is still potential for further reductions, by limiting the number of possible combinations by exploiting
the sphere decoder (SD) principle. However, existing SD algorithms do not consider
the basic and fundamental principle of SM, that at any given time, only one antenna is active.
Therefore, two modified SD algorithms tailored to SM are proposed. It is shown that the proposed
sphere decoder algorithms offer an optimal performance, with a significant reduction of
the computational complexity. Finally, the logarithmic increase in spectral efficiency offered
by SM and the requirement that the number of antennas must be a power of two would require
a large number of antennas. To overcome this limitation, two new MIMO modulation systems
generalised spatial modulation (GNSM) and variable generalised spatial modulation (VGSM)
are proposed, where the same symbol is transmitted simultaneously from more than one transmit
antenna at a time. Transmitting the same data symbol from more than one antenna reduces
the number of transmit antennas needed and retains the key advantages of SM.
In initial development simple channel models can be used, however, as the system develops it
should be tested on more realistic channels, which include the interactions between the environment
and antennas. Therefore, a full analysis of the ABER performance of SM over urban
channel measurements is carried out. The results using the urban measured channels confirm
the theoretical work done in the field of SM. Finally, for the first time, the performance of SM
is tested in a practical testbed, whereby the SM principle is validated