# A Generalized Spatial Modulation System Using Massive MIMO Space Time Coding Antenna Grouping
## 3 Simulation Results  
In the following, simulation results for the proposed GSM-STC technique are compared to conventional GSM [22] and modified GSM. A set of trials were done in terms of modulation techniques, the number of subcarriers and channel taps. These trials are discussed in the following subsections. The simulation results are displayed and discussed. The selective fading channel and QAM modulation will be used. The proposed GSM-STC is evaluated and compared with the conventional and the modified GSM. The simulation test is done for conventional GSM by using one group of antennas containing five antennas at the transmitter. Only two of them are active for each data symbol. At the receiver side, two antennas are used. The modified GSM is examined through simulation for the same number of antennas at the transmitter, like the conventional GSM. However, at the receiver side, four antennas are used. The proposed GSM-STC is implemented using two groups of antennas at the transmitter, where each group has five antennas, with only two of them active per group for each data symbol. A selective Rayleigh fading channel is used with QAM modulation schemes. The simulation parameters used in the evaluation are summarized in Table 3.  
The BER performance versus SNR for M=16 and selective fading channel is shown in Figure 3. The comparison is done for the BER performance of conventional GSM. Simulation results show that the proposed technique outperforms the conventional GSM techniques. The SNR is enhanced by 11 dB as compared to conventional GSM and by 4 dB as compared to modified GSM. \begin{table}
\begin{tabular}{c l l} \hline \hline  & **Receiving Antenna 1** & **Receiving Antenna 2** \\ \hline \multirow{2}{*}{Time \(t\)} & \(r_{0}=h_{0}s_{0}+h_{1}s_{1}+\mu_{0}\) & \(r_{2}=h_{2}s_{0}+h_{3}s_{1}+\mu_{3}\) \\  & \(r_{4}=h_{4}s_{0}+h_{5}s_{1}+\mu_{4}\) & \(r_{6}=h_{6}s_{0}+h_{7}s_{1}+\mu_{6}\) \\ \hline \multirow{2}{*}{Time \(t+\tau\)} & \(r_{1}=-h_{0}s_{1}^{*}+h_{1}s_{0}^{*}+\mu_{1}\) & \(r_{3}=-h_{2}s_{1}^{*}+h_{3}s_{0}^{*}+\mu_{3}\) \\  & \(r_{5}=-h_{4}s_{1}^{*}+h_{5}s_{0}^{*}+\mu_{5}\) & \(r_{7}=-h_{6}s_{1}^{*}+h_{7}s_{0}^{*}+\mu_{7}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The received signal using two antennas at receiver. The procedure is repeated for M = 64, M = 128, M = 256. The obtained results are displayed in Figures 4-6, for the proposed system (GSM-STC) in comparison with conventional and modified GSM. The preference for STC-GSM versus conventional GSM and modified GSM is illustrated in Table 4, which summarizes the obtained SNR in a comparative form. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Types** & **Conventional GSM** & **Modified GSM** & **GSM-STC** \\ \hline Number of antenna & & One group & One group & Two groups \\ groups at transmitter & & & \\ \hline Transmitting antennas \(N_{t}\) & 5 & 5 & 10 \\ \hline Active antennas at & & & \\ transmitter \(N_{u}\) & 2 & 2 & 4 \\ \hline Receiving antennas \(N_{r}\) & 2 & 4 & 4 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Simulation parameters. Figure 4: BER comparison for the proposed technique (GSM-STC) with GSM techniques versus SNR using 64-QAM. Figure 3: BER (bit error rate) comparison for the proposed technique (GSM-STC) with GSM techniques versus SNR (signal-to-noise ratio) using 16-QAM. The GSM-STC technique has a better performance and matches massive MIMO requirements due to the ability to increase the data rate by the use of two subgroups of antennas at the transmitter to achieve diversity and enhance BER. The comparison between QAM modulation schemes with the same number of antennas at transmitter \(N_{t}=10\) and same active antennas per group \(N_{u}=2\), and also with the same number of receiving antennas \(N_{r}=4\), is shown in Figure 7. This reveals that the 16-QAM is better than all the others.