# Singular Value Decomposition Channel Estimation in STBC MIMO-OFDM System
## 5 Simulation Results
The noise suppression performance of the proposed SVD channel estimation method is similar to that of the MMSE method. Hence, the performance of the proposed SVD method is very close to that of the MMSE method. At the BER of \(10^{-2}\), the SVD method outperforms the threshold and LS methods by about 2.7 dB and 6.3 dB SNR gains, respectively. At the BER of \(10^{-3}\), the SNR loss is about 1.3 dB between the threshold and SVD methods, and a 5.9 dB SNR  
Figure 6: Comparisons of BER performance in the case of 16-quadrature amplitude modulation (16 QAM) modulation at the static CDT1 channel. Figure 7: Comparisons of BER performance in the case of 64 QAM modulation at the static CDT1 channel. loss between the LS and SVD methods. Hence, the SVD method increases the accuracy of channel estimation and can be used to estimate the slightly frequency-selectivity CDT1 channel. As can be seen from Figure 6, as the SNR increases in the STBC MIMO-OFDM system, the simulation results of four channel estimation methods are decreased in terms of BER. Under the same conditions, the proposed SVD method has the lowest BER. Therefore, it provides the best BER performance especially under high SNR range. The LS method has the worst BER performance. At the BER of \(10^{-2}\), compared with the threshold channel estimation method, the SVD method has about 4.7 dB SNR gains. At the BER of \(10^{-3}\), the SVD method outperforms the threshold channel estimation method by about 2.9 dB SNR gains. Hence, under the 16 QAM modulation mode, the SVD method can also be well applied to the STBC MIMO-OFDM system. In the 64 QAM modulation, one symbol carries six binary bits, thus increasing the transmission rate in the MIMO-OFDM system. Under the condition of two transmit and two receive antennas, the 64 QAM modulation can provide various phases, it could significantly increase the transmission rate. As can be seen from Figure 7, under the 64 QAM modulation mode, the proposed SVD method also has good performance. Hence, the proposed method can adapt to the 64 QAM modulation mode. Under the QPSK, 16 QAM, and 64 QAM modulation modes, the BER performance curves in the CDT6 channel are shown in Figures 8-10, respectively. Figures 8 and 9 are simulated under the CDT6 channel environment. The BER of four channel estimation methods under the CDT6 channel is higher than in the CDT1 channel due to the stronger frequency-selectivity of the CDT6 channel. In Figure 8, at the BER of \(10^{-2}\), the SVD method outperforms the threshold and LS methods by about 1.8 dB and 6.4 dB SNR gains, respectively. At the BER of \(10^{-3}\), compared with the threshold method, the SVD method has about 0.35 dB SNR gains. In Figure 9, although the BER performance of the 16 QAM modulation mode is worse than that of the QPSK modulation mode, the SVD method still has good performance. At the BER of \(10^{-2}\), the SVD method outperforms the threshold method by about 3.1 dB SNR gains. To clearly see the SNR gains between the SVD and MMSE methods, this paper amplifies the green box part in Figure 9. It can be seen from the amplified part, the SVD method outperforms the MMSE method by about 0.3 dB SNR gains at the BER of \(2\times 10^{-1}\). Hence, SVD channel estimation can be well used in the CDT6 channel to obtain the CFR. As can be seen from Figure 10, the proposed SVD method has good performance under the CDT6 channel with the 64 QAM modulation mode due to fact that the proposed SVD method can suppress the noise effectively. The 64 QAM modulation includes 64 constellation points and is more susceptible  
Figure 8: Comparisons of BER performance in the case of QPSK modulation at the static CDT6 channel. to AWGN. The LS and threshold methods cannot suppress the AWGN effectively. Hence, with the increase of SNR, the BER curves of the LS and threshold methods decrease slowly. Under the QPSK and 16 QAM modulation modes, the BER performance curves in the CDT8 channel are shown in Figures 11 and 12, respectively.