## PERFORMANCE STUDY OF 2X2 AND 4X2 MIMO OFDM(6)

The simulated results in figure 5 and 6 for the MIMO OFDM system shows a plot of BER v/s SNR for 4×1 and 4×2 systems with BPSK modulation. The figure indicates that at BER of 10-3 point the performance in SNR is ~8dB and 6dB in 4×1 and 4×2 systems respectively. The figure also shows that at 10-3 BER, when compared to 4×1, there is an improvement of SNR ~2dB in 4×2 MIMO systems.

Figure 3 : MIMO OFDM BER plot for 2X1 with BPSK modulation

Figure 4 : MIMO OFDM BER plot for 2X2 with BPSK modulation

Figure 5 : MIMO OFDM BER plot for 4X1 with BPSK modulation

Figure 6 : MIMO OFDM BER plot for 4X2 with BPSK modulation

The simulated results in figure 7 for MIMO OFDM system shows a plot of BER v/s SNR for all 2×1, 2×2, 4×1 and 4×2 systems with BPSK modulation. The figure also indicates that at BER of 10-3 point, all the way from 2×1 to 4×2, there is only ~3dB improvement in SNR

Figure 7 : MIMO OFDM BER omparison plot for BPSK modulation

The simulated results in figure 8 and 9 for the MIMO OFDM system shows a plot of BER v/s SNR for 2×1 and 2×2 systems with QPSK modulation. The figure indicates that at BER of 10-3 point the performance in SNR is ~15dB and 12dB in 2×1 and 2×2 systems respectively. The figure also shows that at 10-3 BER, when compared to 2×1, there is an improvement of SNR ~3dB in 2×2 MIMO systems.

Figure 8 : MIMO OFDM BER plot for 2X1 with QPSK modulation

Figure 9 : MIMO OFDM BER plot for 2X2 with QPSK modulation

The simulated results in figure 10 and 11 for the MIMO OFDM system shows a plot of BER v/s SNR for 4×1 and 4×2 systems with QPSK modulation. The figure indicates that at BER of 10-2 point the performance in SNR is ~12dB and 10dB in 4×1 and 4×2 systems respectively. The figure also shows that at 10-3 BER, when compared to 4×1, there is only an improvement of SNR ~2dB in 4×2 MIMO systems.

Figure 10 : MIMO OFDM BER plot for 4X1 with QPSK modulation

Figure 11. MIMO OFDM BER plot for 4X2 with QPSK modulation.

The simulated results in figure 12 for MIMO OFDM system shows a plot of BER v/s SNR for all 2×1, 2×2, 4×1 and 4×2 systems with QPSK modulation. The figure also indicates that at BER of 10-3 point, all the way from 2×1 to 4×2, there is ~2dB improvement in SNR.

Figure 12 : MIMO OFDM BER comparison plot for QPSK modulation

CONCLUSION
In the MIMO case, increasing the number of transmitting and receiving antennas, on the one hand, increases the total number of degrees of freedom for communication and, on the other hand, results in an increase in channel uncertainty. Since the total available transmit power is split uniformly across transmitting antennas, increasing the number of transmit antennas results in a smaller SNR per degree of freedom which leads to the existence of a finite optimum (in the sense of capacity (maximizing) number of transmit antennas. Increasing the number of receive antennas, on the other hand, yields an increase in the receive SNR and is hence always beneficial.