Advanced wireless technology to support high reliability and low complexity needed
along with acccelerated development of technology information and communication. Nowadays researchers and industry have started preparing the world by developing Massive
MIMO technology that can support the evolution of 4G to 5G. There are some studies that
discussed several techniques to overcome problems in communication systems with high reliability. One of the techniques required in massive MIMO implementation is proper space
time coding.In the era of 4G, space time block code developed rapidly with two kinds of
orthogonal schemes that are categorized into two groups: orthogonal and orthogonal quasi.
Orthogonal space time block code that can only be used in simple modulation , with quasi
orthogonal space time block code modulation complex can be applied and orthogonality
value generated by QOSTBC will be higher than OSTBC so as to increase the reliability
of the data. In previous research has been proposed QOSTBC using MC-CDMA as multicarrier, result of this system still has orthogonal which is less stable causing decrease of
system performance
This research will be proposed a MIMO system scheme which is an improvement of
QOSTBC that used a transmission diversity technique. Full diversity in this technique will
occur if multiple symbols are transmitted into two transmitting parts that are transmitted
at different time slots. This improvement from QOSTBC is Twice QOSTBC uses a provision in two codeword matrices to be sent are arranged diagonally so as to have higher
levels of orthogonality. The detection also involves nonlinear processing, which further
complicates the system. To solve these problems, we propose a zero forcing EVCM which
eliminates the system complexity. In this case Twice QOSTBC highly structured (4x1)
can be replaced as an equivalent EVCM channel H.
From the simulation results when used 4 pieces antenna at the transmitter the proposed
results outperform other QOSTBC techniques with a difference around 3 dB for 10?6 BER.
We can concluded that in general the proposed sytem maintained a better performance
compared to other Space Time Coding scheme because the data is transmitted through
two symbols at once which is repeated with the second codeword and the effect of diaganol
matrices at the transmitter can fully the orthogonality of scheme. The decoder ZF EVCM
has a very similar structure as the code matrix S of the underlying Twice QSTBC which
can eliminates the system complexity.