## PERFORMANCE STUDY OF 2X2 AND 4X2 MIMO OFDM(5)

OFDM modulation

MIMO technology will predominantly be used in broadband systems that exhibit frequency-selective fading and, therefore, inter-symbol interference (ISI). OFDM modulation turns the frequency-selective channel into a set of parallel flat fading channels. Figure 1 depicts the schematic of a MIMO-OFDM system. Consequently, the overall frequency-selective channel is converted into a set of parallel flat fading channels, which drastically simplifies the equalization task. However, as the CP carries redundant information, it incurs a loss in spectral efficiency, which is usually kept at a maximum of 25 percent.

In general, OFDM has tighter synchronization requirements than single-carrier (SC) modulation and direct-sequence spread spectrum (DSSS), is more susceptible to phase noise, and suffers from a larger peak-to-average power ratio.

The simulation is done using MATLAB simulation software.

The simulated results in figure 3 and 4 for the MIMO OFDM system shows a plot of BER v/s SNR for 2×1 and 2×2 systems with BPSK modulation. The figure indicates that at BER of 10-3 point the performance in SNR is ~11 dB and 8dB 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.

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